Scorching storms on distant worlds revealed

Astronomers have created the most detailed weather report so far for two distant worlds beyond our own solar system.

The international study -- the first of its kind -- reveals the extreme atmospheric conditions on the celestial objects, which are swathed in swirling clouds of hot sand amid temperatures of 950C.

Using NASA's powerful James Webb Space Telescope (JWST), researchers set out to capture the weather on a pair of brown dwarfs -- cosmic bodies that are bigger than planets but smaller than stars.

These brown dwarfs, named collectively as WISE 1049AB, are the brightest and closest objects of their type to Earth, around six light years away.

The team tracked each brown dwarf's atmosphere by measuring the light waves emitted from their surfaces, which change as more or less cloudy regions revolve in and out of view.

By visualising this data through light curves -- a plot of how the brightness of light from each object changes over time -- the team was able to build up a detailed 3D picture of how the brown dwarfs' weather changed over the course of a full rotation or day, between five and seven hours.

The team was also able to plot how the light from each object varied by wavelength, to demonstrate the presence and complex interplay of gases such as water, methane, and carbon monoxide in their atmospheres.

The insights may help astronomers develop the understanding of brown dwarfs as a potential missing link between stars and planets -- promising new insights into both.

By observing the infrared part of the light spectrum, the JWST is able to observe wavelengths of light that are blocked by our own atmosphere.

This capability opens frontiers in the study of the early universe, star formation, and so-called exoplanets such as brown dwarfs which lie beyond our solar system.

The latest study builds on previous studies of brown dwarfs, which have mainly been confined to capturing static snapshots of their atmosphere on only one side. This approach is limited, as brown dwarfs are known to rotate relatively quickly and their weather can vary greatly over time, researchers say.

Their findings will pave the way for more detailed studies into brown dwarfs and other distant celestial objects.

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Astronomers uncover methane emission on a cold brown dwarf

Using new observations from the James Webb Space Telescope (JWST), astronomers have discovered methane emission on a brown dwarf, an unexpected finding for such a cold and isolated world. Published in the journal Nature, the findings suggest that this brown dwarf might generate aurorae similar to those seen on our own planet as well as on Jupiter and Saturn.

More massive than planets but lighter than stars, brown dwarfs are ubiquitous in our solar neighborhood, with thousands identified. Last year, Jackie Faherty, a senior research scientist and senior education manager at the American Museum of Natural History, led a team of researchers who were awarded time on JWST to investigate 12 brown dwarfs. Among those was CWISEP J193518.59-154620.3 (or W1935 for short) -- a cold brown dwarf 47 light years away that was co-discovered by Backyard Worlds: Planet 9 citizen science volunteer Dan Caselden and the NASA CatWISE team. W1935 is a cold brown dwarf with a surface temperature of about 400° Fahrenheit, or about the temperature at which you'd bake chocolate chip cookies. The mass for W1935 isn't well known but it likely ranges between 6-35 times the mass of Jupiter.

After looking at a number of brown dwarfs observed with JWST, Faherty's team noticed that W1935 looked similar but with one striking exception: it was emitting methane, something that's never been seen before on a brown dwarf.

"Methane gas is expected in giant planets and brown dwarfs but we usually see it absorbing light, not glowing," said Faherty, the lead author of the study. "We were confused about what we were seeing at first but ultimately that transformed into pure excitement at the discovery."

Computer modeling yielded another surprise: the brown dwarf likely has a temperature inversion, a phenomenon in which the atmosphere gets warmer with increasing altitude. Temperature inversions can easily happen to planets orbiting stars, but W1935 is isolated, with no obvious external heat source.

"We were pleasantly shocked when the model clearly predicted a temperature inversion," said co-author Ben Burningham from the University of Hertfordshire. "But we also had to figure out where that extra upper atmosphere heat was coming from."

To investigate, the researchers turned to our solar system. In particular, they looked at studies of Jupiter and Saturn, which both show methane emission and have temperature inversions. The likely cause for this feature on solar system giants is aurorae, therefore, the research team surmised that they had uncovered that same phenomenon on W1935.

Planetary scientists know that one of the major drivers of aurorae on Jupiter and Saturn are high-energy particles from the Sun that interact with the planets' magnetic fields and atmospheres, heating the upper layers. This is also the reason for the aurorae that we see on Earth, commonly referred to as the Northern or Southern Lights since they are most extraordinary near the poles. But with no host star for W1935, a solar wind cannot contribute to the explanation.

There is an enticing additional reason for the aurora in our solar system. Both Jupiter and Saturn have active moons that occasionally eject material into space, interact with the planets, and enhance the auroral footprint on those worlds. Jupiter's moon Io is the most volcanically active world in the solar system, spewing lava fountains dozens of miles high, and Saturn's moon Enceleadus ejects water vapor from its geysers that simultaneously freezes and boils when it hits space. More observations are needed, but the researchers speculate that one explanation for the aurora on W1935 might be an active, yet-to-be discovered moon.

"Every time an astronomer points JWST at an object, there's a chance of a new mind-blowing discovery," said Faherty. "Methane emission was not on my radar when we started this project but now that we know it can be there and the explanation for it so enticing I am constantly on the look-out for it. That's part of how science moves forward."

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Astronomy: How do brown dwarfs form?

New observations provide insights into whether the birth of the giant planets takes a similar course to that of stars.

The birth of stars is a chaotic and dynamic process, especially in the early phase, which is characterized by complex gas structures in the form of spirals and streamers.

Such structures are termed "feeding filaments" because they feed the gaseous material from the surroundings to the newly born star, akin to cosmic umbilical cords.

Cosmic umbilical cord

Brown dwarfs are celestial objects with masses less than one-tenth of the mass of the Sun.

This makes them too small to undergo nuclear fusion and shine like stars.

Before now, scientists did not know whether brown dwarfs form like sun-like stars or not.

A test of this hypothesis requires high-sensitivity and high-angular resolution observations of brown dwarfs during their earliest formation stages.

An international team led by LMU astrophysicist Dr. Basmah Riaz from the University Observatory Munich has now accomplished just that: The researchers conducted observations of the extremely young brown dwarf, Ser-emb 16, using the highly sophisticated ALMA observatory in Chile and recently published their results in the journal Monthly Notices of the Royal Astronomical Society.

"Our observations have revealed spectacular large-scale spiral and streamer structures that have never been seen before towards a newly born brown dwarf," says Riaz.

The filaments cover a vast area of about 2,000-3,000 astronomical units and are connected to Ser-emb 16. Clumps of matter were also seen around it, which themselves could potentially evolve into young brown dwarfs.

"These observations show, for the first time, the influence of the external environment, which results in asymmetric mass accretion via feeding filaments on to a brown dwarf in the making," says the astronomer.

Collapsing clumps or magnetic cores?

The spiral structures and streamers provide important clues about how brown dwarfs form.

Having simulated possible scenarios, the researchers compared them with data from the ALMA observatory.

The large structures could be explained, for example, by collisions of collapsing clumps within a star-forming region.

For this to occur, such collisions would have to happen at least once during the lifetime of star-forming cores.

"We have shown through new numerical simulations that collisions trigger the collapse of even small clumps to form brown dwarfs. Spirals and streamers of various sizes and morphologies form due to the collisions happening sideways, not head-on," says co-author Dr. Dimitris Stamatellos from the University of Central Lancashire in England.

If this model is correct, it implies a dynamic brown dwarf formation process, similar to Sun-like stars, where chaotic interactions in a star-forming environment are common from an early age.

In another scenario, the simulations showed that the observed structures correspond to the large (pseudo)-disk around a very young brown dwarf, where the (pseudo)-disk has been twisted by the rotation of the brown dwarf core in the presence of a strong magnetic field.

If this model is correct, it means the magnetic field plays an important role in the brown dwarf formation process.

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NASA's Webb finds signs of possible aurorae on isolated brown dwarf

Astronomers using NASA's James Webb Space Telescope have found a brown dwarf (an object more massive than Jupiter but smaller than a star) with infrared emission from methane, likely due to energy in its upper atmosphere. This is an unexpected discovery because the brown dwarf, W1935, is cold and lacks a host star; therefore, there is no obvious source for the upper atmosphere energy. The team speculates that the methane emission may be due to processes generating aurorae.

These findings are being presented at the 243rd meeting of the American Astronomical Society in New Orleans.

To help explain the mystery of the infrared emission from methane, the team turned to our solar system. Methane in emission is a common feature in gas giants like Jupiter and Saturn. The upper-atmosphere heating that powers this emission is linked to aurorae.

On Earth, aurorae are created when energetic particles blown into space from the Sun are captured by Earth's magnetic field. They cascade down into our atmosphere along magnetic field lines near Earth's poles, colliding with gas molecules and creating eerie, dancing curtains of light. Jupiter and Saturn have similar auroral processes that involve interacting with the solar wind, but they also get auroral contributions from nearby active moons like Io (for Jupiter) and Enceladus (for Saturn).

For isolated brown dwarfs like W1935, the absence of a stellar wind to contribute to the auroral process and explain the extra energy in the upper atmosphere required for the methane emission is a mystery. The team surmises that either unaccounted internal processes like the atmospheric phenomena of Jupiter and Saturn, or external interactions with either interstellar plasma or a nearby active moon, may help account for the emission.

A Detective Story

The aurorae's discovery played out like a detective story. A team led by Jackie Faherty, an astronomer at the American Museum of Natural History in New York, was awarded time with the Webb telescope to investigate 12 cold brown dwarfs. Among those were W1935 -- an object that was discovered by citizen scientist Dan Caselden, who worked with the Backyard Worlds zooniverse project -- and W2220, an object that was discovered using NASA's Wide Field Infrared Survey Explorer. Webb revealed in exquisite detail that W1935 and W2220 appeared to be near clones of each other in composition. They also shared similar brightness, temperatures, and spectral features of water, ammonia, carbon monoxide, and carbon dioxide. The striking exception was that W1935 showed emission from methane, as opposed to the anticipated absorption feature that was observed toward W2220. This was seen at a distinct infrared wavelength to which Webb is uniquely sensitive.

"We expected to see methane because methane is all over these brown dwarfs. But instead of absorbing light, we saw just the opposite: The methane was glowing. My first thought was, what the heck? Why is methane emission coming out of this object?" said Faherty.

The team used computer models to infer what might be behind the emission. The modeling work showed that W2220 had an expected distribution of energy throughout the atmosphere, getting cooler with increasing altitude. W1935, on the other hand, had a surprising result. The best model favored a temperature inversion, where the atmosphere got warmer with increasing altitude. "This temperature inversion is really puzzling," said Ben Burningham, a co-author from the University of Hertfordshire in England and lead modeler on the work. "We have seen this kind of phenomenon in planets with a nearby star that can heat the stratosphere, but seeing it in an object with no obvious external heat source is wild."

Clues from our Solar System

For clues, the team looked in our own backyard, to the planets of our solar system. The gas giant planets can serve as proxies for what is seen going on more than 40 light-years away in the atmosphere of W1935.

The team realized that temperature inversions are prominent in planets like Jupiter and Saturn. There is still ongoing work to understand the causes of their stratospheric heating, but leading theories for the solar system involve external heating by aurorae and internal energy transport from deeper in the atmosphere (with the former a leading explanation).

Brown Dwarf Aurora Candidates in Context

This is not the first time an aurora has been used to explain a brown dwarf observation. Astronomers have detected radio emission coming from several warmer brown dwarfs and invoked aurorae as the most likely explanation. Searches were conducted with ground-based telescopes like the Keck Observatory for infrared signatures from these radio-emitting brown dwarfs to further characterize the phenomenon, but were inconclusive.

W1935 is the first auroral candidate outside the solar system with the signature of methane emission. It's also the coldest auroral candidate outside our solar system, with an effective temperature of about 400 degrees Fahrenheit (200 degrees Celsius), about 600 degrees Fahrenheit warmer than Jupiter.

In our solar system the solar wind is a primary contributor to auroral processes, with active moons like Io and Enceladus playing a role for planets like Jupiter and Saturn, respectively. W1935 lacks a companion star entirely, so a stellar wind cannot contribute to the phenomenon. It is yet to be seen whether an active moon might play a role in the methane emission on W1935.

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Simulations reveal hydrodynamics of planetary engulfment by expanding star

When our sun exhausts the hydrogen fuel in its core some 5 billion years from now, it will expand to become a red giant, engulfing the inner planets. The dynamics and possible outcomes of planetary engulfment are poorly understood, but it is thought to be a relatively common fate for planetary systems.

A new study using hydrodynamical simulations reveals the forces acting on a planet when it is swallowed by an expanding star. The results show that the interactions of a substellar body (a planet or brown dwarf) with the hot gas in the outer envelope of a sun-like star can lead to a range of outcomes depending on the size of the engulfed object and the stage of the star's evolution.

Lead author Ricardo Yarza at the University of California, Santa Cruz, will present the new findings on June 13, 2022, at the 240th meeting of the American Astronomical Society (AAS) in Pasadena.

"Evolved stars can be hundreds or even thousands of times larger than their planets, and this disparity of scales makes it difficult to perform simulations that accurately model the physical processes occurring at each scale," said Yarza, a graduate student in astronomy and astrophysics at UCSC. "Instead, we simulate a small section of the star centered on the planet to understand the flow around the planet and measure the drag forces acting on it."

The results may help explain recent observations of planets and brown dwarfs closely orbiting stellar remnants such as white dwarfs and subdwarfs. Previous studies have suggested that these systems may be the end result of a planetary engulfment process that involves shrinking of the engulfed body's orbit and ejection of the outer layers of the star.

"As the planet travels inside the star, drag forces transfer energy from the planet to the star, and the stellar envelope can become unbound if the transferred energy exceeds its binding energy," Yarza explained.

According to the calculations by Yarza and his colleagues, no substellar bodies smaller than about 100 times the mass of Jupiter can eject the envelope of a sun-like star before it has expanded to about 10 times the radius of the sun. At later stages of stellar evolution and expansion, however, the stellar envelope could be ejected by an object as small as ten times the mass of Jupiter, which would shrink its orbit by several orders of magnitude in the process.

The study also found that planetary engulfment can increase the luminosity of a sun-like star by several orders of magnitude for up to several thousand years, depending on the mass of the engulfed object and the evolutionary stage of the star.

The framework provided by this study can be incorporated into future work to explore the effect of engulfment on the structure of the star. "Our work can inform simulations of planetary engulfment at the scale of the star by providing an accurate reference picture of the physics at the scale of the planet," Yarza said.

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Ground-breaking number of brown dwarfs discovered

Brown dwarfs are mysterious astronomical objects that fill the gap between the heaviest planets and the lightest stars, with a mix of stellar and planetary characteristics. Due to this hybrid nature, these puzzling objects are crucial to improve our understanding of both stars and giant planets. Brown dwarfs orbiting a parent star from sufficiently far away are particularly valuable as they can be directly photographed -- unlike those that are too close to their star and are thus hidden by its brightness. This provides scientists with a unique opportunity to study the details of the cold, planet-like atmospheres of brown dwarf companions.

However, despite remarkable efforts in the development of new observing technologies and image processing techniques, direct detections of brown dwarf companions to stars have remained rather sparse, with only around 40 systems imaged in almost three decades of searches. Researchers led by Mariangela Bonavita from the Open University and Clémence Fontanive from the Center for Space and Habitability (CSH) and the NCCR PlanetS at the University of Bern directly imaged four new brown dwarfs as they report in a study that has just been published in the journal Monthly Notices of the Royal Astronomical Society MNRAS. This is the first time that multiple new systems with brown dwarf companions on wide orbital separations have been announced at the same time.

Innovative search method

"Wide-orbit brown dwarf companions are rare to start with, and detecting them directly poses huge technical challenges since the host stars completely blind our telescopes," says Mariangela Bonavita. Most surveys conducted so far have been blindly targeting random stars from young clusters. "An alternative approach to increase the number of detections is to only observe stars that show indications of an additional object in their system," explains Clémence Fontanive. For example, the way a star moves under the gravitational tug of a companion can be an indicator of the existence of that companion, whether it is a star, a planet or something in between.

"We developed the COPAINS tool which predicts the types of companions that could be responsible for observed anomalies in stellar motions," Clémence Fontanive continues. Applying the COPAINS tool the research team carefully selected 25 nearby stars that seemed promising for the direct detection of hidden, low-mass companions based on data from the Gaia spacecraft of the European Space Agency (ESA). Using then the SPHERE planet-finder at the Very Large Telescope in Chile to observe these stars, they successfully detected ten new companions with orbits ranging from that of Jupiter to beyond that of Pluto, including five low-mass stars, a white dwarf (a dense stellar remnant), and a remarkable four new brown dwarfs.

Major boost in detection rate

"These findings significantly advance the number of known brown dwarfs orbiting stars from large distances, with a major boost in detection rate compared to any previous imaging survey," as Mariangela Bonavita explains. While for now this approach is mostly limited to signatures from brown dwarf and stellar companions, future phases of the Gaia mission will push these methods to lower masses and allow for the discovery of new giant exoplanets. Clémence Fontanive adds: "On top of having so many new discoveries in one go, our program also demonstrates the power of these search strategies."

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Astronomers discover widest separation of brown dwarf pair to date

A team of astronomers has discovered a rare pair of brown dwarfs that has the widest separation of any brown dwarf binary system found to date.

"Because of their small size, brown dwarf binary systems are usually very close together," said Emma Softich, an undergraduate astrophysics student at the Arizona State University (ASU) School of Earth and Space Exploration and lead author of the study. "Finding such a widely separated pair is very exciting."

The gravitational force between a pair of brown dwarfs is lower than for a pair of stars with the same separation, so wide brown dwarf binaries are more likely to break up over time, making this pair of brown dwarfs an exceptional find.

The study, which is based on observations the University of California San Diego (UC San Diego) Cool Star Lab conducted with W. M. Keck Observatory on Maunakea, Hawai'i Island, is published in today's issue of The Astrophysical Journal Letters.

Using Keck Observatory's Near-Infrared Echellette Spectrometer, or NIRES instrument, members of the UC San Diego Cool Star Lab, including Physics Professor Adam Burgasser and graduate students Christian Aganze and Dino Hsu, obtained infrared spectra of the brown dwarf binary system, called CWISE J014611.20-050850.0AB. The data revealed the two brown dwarfs are about 12 billion miles apart, or three times the separation of Pluto from the Sun. This distance confirms the unusual brown dwarf couple breaks the record for having the widest separation from each other.

"Keck's exceptional sensitivity in the infrared with this instrument was critical for our measurements," said co-author Burgasser, who leads the Cool Star Lab. "The secondary brown dwarf of this system is exceptionally faint, but with Keck we were able to obtain good enough spectral data to classify both sources and identify them as members of a rare class of blue L dwarfs."

"Wide, low-mass systems like CWISE J014611.20-050850.0AB are usually disrupted early on in their lifetimes, so the fact that this one has survived until now is pretty remarkable," said co-author Adam Schneider of the U.S. Naval Observatory, Flagstaff Station and George Mason University.

Brown dwarfs are celestial objects that are smaller than a normal star. These objects are not massive enough to sustain nuclear fusion and shine like normal stars, but are hot enough to radiate energy.

Many brown dwarfs have been discovered with data from NASA's Wide-field Infrared Survey Explorer (WISE) via the Backyard Worlds: Planet 9 citizen science project, which solicits help from the public to search the WISE image data bank to find brown dwarfs and low-mass stars, some of the Sun's nearest neighbors.

For this study, the researchers inspected images of Backyard Worlds discoveries, where companion brown dwarfs may have been overlooked. In doing so, they discovered the rare CWISE J014611.20 050850.0AB brown dwarf binary system.

Softich went through about 3,000 brown dwarfs from Backyard Worlds one by one and compared the WISE images to other survey images, looking for evidence of a brown dwarf companion to the original target. The team then used data from the Dark Energy Survey (DES) to confirm that it was indeed a brown dwarf pair.

They then used Keck Observatory's NIRES to confirm the brown dwarfs have spectral types L4 and L8, and that they are at an estimated distance of about 40 parsecs, or 130.4 light-years from Earth, with a projected separation of 129 astronomical units, or 129 times the distance between the Sun and the Earth.

The team hopes this discovery will allow astronomers the chance to study brown dwarf binary systems and to develop models and procedures that will help in recognizing more of them in the future.

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Citizen scientists find young-Jupiter-like object missed by previous exoplanet searches

Citizen scientists have discovered a new object orbiting a Sun-like star that had been missed by previous searches. The object is very distant from its host star -- more than 1,600 times farther than the Earth is from the Sun -- and is thought to be a large planet or a small brown dwarf, a type of object that is not massive enough to burn hydrogen like true stars. Details about the new world are published today in The Astrophysical Journal.

"This star had been looked at by more than one campaign searching for exoplanet companions. But previous teams looked really tight, really close to the star," said lead author Jackie Faherty, senior scientist in the American Museum of Natural History's Department of Astrophysics and co-founder of the citizen science project Backyard Worlds: Planet 9, which led to the object's discovery. "Because citizen scientists really liked the project, they found an object that many of these direct imaging surveys would have loved to have found, but they didn't look far enough away from its host."

The Backyard Worlds project lets volunteers search through nearly five years of digital images taken from NASA's Wide-field Infrared Survey Explorer (WISE) mission to try to identify new worlds inside and outside of our solar system. If an object close to Earth is moving, it will appear to "jump" in the same part of the sky over the years, similar to an object "moving" in a flipbook. Users can then flag these objects for further study by scientists.

In 2018, Backyard Worlds participant Jörg Schümann, who lives in Germany, alerted scientists to a new co-moving system: an object that appeared to be moving with a star. After confirming the system's motion, scientists used telescopes in California and Hawai'i to observe the star and object separately and were immediately excited by what they saw.

The new object is young and has a low mass, between 10 and 20 times the mass of Jupiter. This range overlaps with an important cutoff point -- 13 times the mass of Jupiter -- which is sometimes used to distinguish planets from brown dwarfs. But scientists still aren't sure how heavy planets can be, which can make relying on this cutoff challenging. "We don't have a very good definition of the word 'planet,'" said Faherty.

Another defining feature is how they form: planets form from material gathering in disks around stars, while brown dwarfs are born from the collapse of giant clouds of gas, similar to how stars form. But the physical properties of this new object do not provide any clues to its formation. "There are hints that maybe it's more like an exoplanet, but there's nothing conclusive yet. However, it is an outlier," said Faherty.

What surprised the team the most is the new object's relationship to its host star. The object is farther away from the star than expected based on its comparatively low mass -- over 1,600 times farther than the Earth is from the Sun. Few objects with such different masses from their host star have been found this far apart.

Ultimately, this discovery may help scientists get a better sense of how solar systems form, which is crucial to understanding the origins of life in the universe. "You had an exoplanet community just staring so close to it," said Faherty. "And we just pulled out a little, and we found an object. That makes me excited about what we might be missing in giant planets that might exist around these stars," said Faherty. "Sometimes, you need to broaden your scope."

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Unravelling the mystery of brown dwarfs

Brown dwarfs are astronomical objects with masses between those of planets and stars. The question of where exactly the limits of their mass lie remains a matter of debate, especially since their constitution is very similar to that of low-mass stars. So how do we know whether we are dealing with a brown dwarf or a very low mass star? An international team, led by scientists from the University of Geneva (UNIGE) and the Swiss National Centre of Competence in Research (NCCR) PlanetS, in collaboration with the University of Bern, has identified five objects that have masses near the border separating stars and brown dwarfs that could help scientists understand the nature of these mysterious objects. The results can be found in the journal Astronomy & Astrophysics.

Like Jupiter and other giant gas planets, stars are mainly made of hydrogen and helium. But unlike gas planets, stars are so massive and their gravitational force so powerful that hydrogen atoms fuse to produce helium, releasing huge amounts of energy and light.

'Failed stars'

Brown dwarfs, on the other hand, are not massive enough to fuse hydrogen and therefore cannot produce the enormous amount of light and heat of stars. Instead, they fuse relatively small stores of a heavier atomic version of hydrogen: deuterium. This process is less efficient and the light from brown dwarfs is much weaker than that from stars. This is why scientists often refer to them as 'failed stars'.

"However, we still do not know exactly where the mass limits of brown dwarfs lie, limits that allow them to be distinguished from low-mass stars that can burn hydrogen for many billions of years, whereas a brown dwarf will have a short burning stage and then a colder life," points out Nolan Grieves, a researcher in the Department of Astronomy at the UNIGE's Faculty of Science, a member of the NCCR PlanetS and the study's first author. "These limits vary depending on the chemical composition of the brown dwarf, for example, or the way it formed, as well as its initial radius," he explains. To get a better idea of what these mysterious objects are, we need to study examples in detail. But it turns out that they are rather rare. "So far, we have only accurately characterised about 30 brown dwarfs," says the Geneva-based researcher. Compared to the hundreds of planets that astronomers know in detail, this is very few. All the more so if one considers that their larger size makes brown dwarfs easier to detect than planets.

New pieces to the puzzle

Today, the international team characterized five companions that were originally identified with the Transiting Exoplanet Survey Satellite (TESS) as TESS objects of interest (TOI) -- TOI-148, TOI-587, TOI-681, TOI-746 and TOI-1213. These are called 'companions' because they orbit their respective host stars. They do so with periods of 5 to 27 days, have radii between 0.81 and 1.66 times that of Jupiter and are between 77 and 98 times more massive. This places them on the borderline between brown dwarfs and stars.

These five new objects therefore contain valuable information. "Each new discovery reveals additional clues about the nature of brown dwarfs and gives us a better understanding of how they form and why they are so rare," says Monika Lendl, a researcher in the Department of Astronomy at the UNIGE and a member of the NCCR PlanetS.

One of the clues the scientists found to show these objects are brown dwarfs is the relationship between their size and age, as explained by François Bouchy, professor at UNIGE and member of the NCCR PlanetS: "Brown dwarfs are supposed to shrink over time as they burn up their deuterium reserves and cool down. Here we found that the two oldest objects, TOI 148 and 746, have a smaller radius, while the two younger companions have larger radii."

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Astronomers probe layer-cake structure of brown dwarf’s atmosphere

Maunakea, Hawaii -- Jupiter may be the bully planet of our solar system because it's the most massive planet, but it's actually a runt compared to many of the giant planets found around other stars.

These alien worlds, called super-Jupiters, weigh up to 13 times Jupiter's mass. Astronomers have analyzed the composition of some of these monsters, but it has been difficult to study their atmospheres in detail because these gas giants get lost in the glare of their parent stars.

Researchers, however, have a substitute: the atmospheres of brown dwarfs, so-called failed stars that are up to 80 times Jupiter's mass. These hefty objects form out of a collapsing cloud of gas, as stars do, but lack the mass to become hot enough to sustain nuclear fusion in their cores, which powers stars.

Instead, brown dwarfs share a kinship with super-Jupiters. Both types of objects have similar temperatures and are extremely massive. They also have complex, varied atmospheres. The only difference, astronomers think, is their pedigree. Super-Jupiters form around stars; brown dwarfs often form in isolation.

A team of astronomers, led by Elena Manjavacas of the Space Telescope Science Institute in Baltimore, Maryland, has tested a new way to peer through the cloud layers of these nomadic objects. The researchers used an instrument at W. M. Keck Observatory on Maunakea in Hawaii to study in near-infrared light the colors and brightness variations of the layer-cake cloud structure in the nearby, free-floating brown dwarf known as 2MASS J22081363+2921215.

The Keck Observatory instrument, called the Multi-Object Spectrograph for Infrared Exploration (MOSFIRE), also analyzed the spectral fingerprints of various chemical elements contained in the clouds and how they change with time. This is the first time astronomers have used MOSFIRE in this type of study.

These measurements offered Manjavacas a holistic view of the brown dwarf's atmospheric clouds, providing more detail than previous observations of this object. Pioneered by Hubble observations, this technique is difficult for ground-based telescopes to do because of contamination from Earth's atmosphere, which absorbs certain infrared wavelengths. This absorption rate changes due to the weather.

"The only way to do this from the ground is by using Keck's high-resolution MOSFIRE instrument because it allows us to observe multiple stars simultaneously with our brown dwarf," said Manjavacas, a former staff astronomer at Keck Observatory and the lead author of the study. "This allows us to correct for the contamination introduced by the Earth's atmosphere and measure the true signal from the brown dwarf with good precision. So, these observations are a proof-of-concept that MOSFIRE can do these types of studies of brown dwarf atmospheres."

She decided to study this particular brown dwarf because it is very young and therefore extremely bright. It has not cooled off yet. Its mass and temperature are similar to those of the nearby giant exoplanet Beta Pictoris b, discovered in 2008 near-infrared images taken by the European Southern Observatory's Very Large Telescope in northern Chile.

"We don't have the ability yet with current technology to analyze in detail the atmosphere of Beta Pictoris b," Manjavacas said. "So, we're using our study of this brown dwarf's atmosphere as a proxy to get an idea of what the exoplanet's clouds might look like at different heights of its atmosphere."

Both the brown dwarf and Beta Pictoris b are young, so they radiate heat strongly in the near-infrared. They are both members of a flock of stars and sub-stellar objects called the Beta Pictoris moving group, which shares the same origin and a common motion through space. The group, which is about 33 million years old, is the closest grouping of young stars to Earth. It is located roughly 115 light-years away.

While they're cooler than bona fide stars, brown dwarfs are still extremely hot. The brown dwarf in Manjavacas' study is a sizzling 2,780 degrees Fahrenheit (1,527 degrees Celsius).

The giant object is about 12 times heavier than Jupiter. As a young body, it is spinning incredibly fast, completing a rotation every 3.5 hours, compared to Jupiter's 10-hour rotation period. So, clouds are whipping around the planet, creating a dynamic, turbulent atmosphere.

Keck Observatory's MOSFIRE instrument stared at the brown dwarf for 2.5 hours, watching how the light filtering up through the atmosphere from the dwarf's hot interior brightens and dims over time. Bright spots that appeared on the rotating object indicate regions where researchers can see deeper into the atmosphere, where it is hotter. Infrared wavelengths allow astronomers to peer deeper into the atmosphere. The observations suggest the brown dwarf has a mottled atmosphere with scattered clouds. If viewed close-up, the planet might resemble a carved Halloween pumpkin, with light escaping from the hot interior.

Its spectrum reveals clouds of hot sand grains and other exotic elements. Potassium iodide traces the object's upper atmosphere, which also includes magnesium silicate clouds. Moving down in the atmosphere is a layer of sodium iodide and magnesium silicate clouds. The final layer consists of aluminum oxide clouds. The atmosphere's total depth is 446 miles (718 kilometers). The elements detected represent a typical part of the composition of brown dwarf atmospheres, Manjavacas said.

She and her team used computer models of brown dwarf atmospheres to determine the location of the chemical compounds in each cloud layer.

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Caught speeding: Clocking the fastest-spinning brown dwarfs

 Astronomers at Western University have discovered the most rapidly rotating brown dwarfs known. They found three brown dwarfs that each complete a full rotation roughly once every hour. That rate is so extreme that if these "failed stars" rotated any faster, they could come close to tearing themselves apart. Identified by NASA's Spitzer Space Telescope, the brown dwarfs were then studied by ground-based telescopes including Gemini North, which confirmed their surprisingly speedy rotation.

Three brown dwarfs have been discovered spinning faster than any other found before. Astronomers at Western University in Canada first measured the rotation speeds of these brown dwarfs using NASA's Spitzer Space Telescope and confirmed them with follow-up observations with the Gemini North telescope on Maunakea in Hawai'i and the Carnegie Institution for Science's Magellan Baade telescope in Chile. Gemini North is one of the pair of telescopes that make up the international Gemini Observatory, a Program of NSF's NOIRLab.

"We seem to have come across a speed limit on the rotation of brown dwarfs," said Megan Tannock, the Western University physics and astronomy graduate student who led the discovery. "Despite extensive searches, by our own team and others, no brown dwarfs have been found to rotate any faster. In fact, faster spins may lead to a brown dwarf tearing itself apart."

Brown dwarfs are, simply put, failed stars. They form like stars but are less massive and more like giant planets.

Tannock and Western University astronomer Stanimir Metchev worked with international collaborators to find three rapidly rotating brown dwarfs spinning around their axes once every hour. This is approximately 10 times faster than normal, and about 30 percent faster than the most rapid rotations previously measured in such objects.

The astronomers used large ground-based telescopes, Gemini North in Hawai'i and Magellan Baade in Chile, to confirm the rapid rotations. They did this by measuring alterations in the brown dwarfs' light caused by the Doppler effect and using a computer model to match those alterations to spin rates. The researchers found that these brown dwarfs spin with speeds of about 350,000 kilometers per hour (around 220,000 miles per hour) at their equator, which is 10 times faster than Jupiter.

"These unusual brown dwarfs are spinning at dizzying speeds," said Sandy Leggett, an astronomer at Gemini North who studies brown dwarfs. "At about 350,000 kilometers per hour, the relatively weak gravity of the brown dwarfs is barely holding them together. This exciting discovery by the Tannock team has identified rotational limits beyond which these objects may not exist."

The team first identified the rapid rotation rates by using NASA's Spitzer Space Telescope to measure how quickly the brightness of the objects varied. "Brown dwarfs, like planets with atmospheres, can have large weather storms that affect their visible brightness," explained Metchev. "The observed brightness variations show how frequently the same storms are seen as the object spins, which reveals the brown dwarf's spin period."

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Cool new worlds found in our cosmic backyard

 How complete is our census of the Sun's closest neighbors? Astronomers using NSF's NOIRLab facilities and a team of data-sleuthing volunteers participating in Backyard Worlds: Planet 9, a citizen science project, have discovered roughly 100 cool worlds near the Sun -- objects more massive than planets but lighter than stars, known as brown dwarfs. Several of these newly discovered worlds are among the very coolest known, with a few approaching the temperature of Earth -- cool enough to harbor water clouds.

Discovering and characterizing astronomical objects near the Sun is fundamental to our understanding of our place in, and the history of, the Universe. Yet astronomers are still unearthing new residents of the Solar neighborhood. A remarkable breakthrough was announced today, with the discovery of roughly 100 cool brown dwarfs near the Sun.The new Backyard Worlds discoveries bridge a previously empty gap in the range of low-temperature brown dwarfs, identifying a long-sought missing link within the brown dwarf population.

"These cool worlds offer the opportunity for new insights into the formation and atmospheres of planets beyond the Solar System," said Aaron Meisner from the National Science Foundation's NOIRLab and the lead author of the research paper. "This collection of cool brown dwarfs also allows us to accurately estimate the number of free-floating worlds roaming interstellar space near the Sun."

This major advancement was made possible with archival data from the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory (KPNO) and the Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory (CTIO), which were made available through the Community Science and Data Center (CSDC), all programs of NSF's NOIRLab. Large survey data sets were then made available to the Backyard Worlds volunteers using NOIRLab's Astro Data Lab science platform. The results, to be published in TheAstrophysical Journal, demonstrate the rapidly growing role of survey and archival data research in astronomy today.

Brown dwarfs lie somewhere between the most massive planets and the smallest stars. Lacking the mass needed to sustain nuclear reactions in their core, brown dwarfs resemble cooling embers. Their low mass, low temperature and lack of internal nuclear reactions make them extremely faint -- and therefore extremely difficult to detect. Because of this, when searching for the very coolest brown dwarfs, astronomers can only hope to detect such objects relatively close to the Sun.

To help find our Sun's coldest and nearest neighbors, the astronomers of the Backyard Worlds project turned to a worldwide network of more than 100,000 citizen scientists. These volunteers diligently inspect trillions of pixels of telescope images to identify the subtle movements of brown dwarfs and planets. Despite the abilities of machine learning and supercomputers, there's no substitute for the human eye when it comes to scouring telescope images for moving objects.

The keen eyes of the Backyard Worlds volunteers have already discovered more than 1,500 cold worlds near to the Sun, and today's paper presents roughly 100 of the coldest in that sample. According to Meisner, this is a record for any citizen science program by a factor of about 20, and 20 citizen scientists are listed as co-authors of the study. A handful of these cool worlds -- which are among the very coldest brown dwarfs known -- approach the temperature of Earth. NASA's Spitzer Space Telescope provided the brown dwarf temperature estimates.

Brown dwarfs are expected to cool as they age, passing from near-stellar temperatures down to planetary temperatures and below, fading all the while and eventually winking out. The new discoveries attest to this picture by uncovering elusive examples of brown dwarfs approaching Earth-temperature.

"This paper is evidence that the solar neighborhood is still uncharted territory and citizen scientists are excellent astronomical cartographers," said co-author Jackie Faherty of the American Museum of Natural History. "Mapping the coldest brown dwarfs down to the lowest masses gives us key insights into the low-mass star formation process while providing a target list for detailed studies of the atmospheres of Jupiter analogs."

Citizen scientist, Astro Data Lab user, and paper co-author Jim Walla added, "It's awesome to know that our discoveries are now counted among the Sun's neighbors and will be targets of further research."

Alongside the dedicated efforts of the Backyard Worlds volunteers, NOIRLab's Astro Data Lab was instrumental in this research. The technical burden of downloading billion-object astronomical catalogs is typically insurmountable for individual investigators -- including most professional astronomers. "AstroData Lab's open and accessible web portal allowed Backyard Worlds citizen scientists to easily query massive catalogs for brown dwarf candidates," explained NOIRLab astronomer Stephanie Juneau, who helped introduce the citizen scientists to Astro Data Lab. Astro Data Lab also enables convenient matching between data sets from NOIRLab telescopes and external facilities, such as NASA's WISE satellite, that jointly contributed to these brown dwarf discoveries.

In addition to Astro Data Lab's making data accessible to the Backyard Worlds collaboration, archival observations by telescopes at two other NOIRLab Programs -- CTIO and KPNO -- were also key to this discovery. "Wide-area imaging from NOIRLab's Mayall and Blanco telescopes was also critical," explained Aaron Meisner. "To select only the very coldest brown dwarfs, we inspected deep images from a variety of sensitive astronomical surveys."

"It's great to see such thrilling results from NOIRLab's efforts to broaden participation in astronomy research," said Chris Davis of the National Science Foundation, the US agency that supports operations at the Kitt Peak and Cerro Tololo observatories and at CSDC. "By making archival data from NSF's Mayall and Blanco telescopes publicly available and easily accessible through CSDC, folks with a fascination for astronomy can make a real contribution to science and to our understanding of the Universe."

The approach of the Backyard Worlds project -- searching for rare objects in large data sets -- is also one of the goals for the upcoming Vera C. Rubin Observatory. Currently under construction on Cerro Pachón in the Chilean Andes, Rubin Observatory will image the visible sky from the southern hemisphere every three nights over ten years, providing a vast amount of data that will enable new ways of doing astrophysical research.

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In a first, NASA measures wind speed on a brown dwarf

For the first time, scientists have directly measured wind speed on a brown dwarf, an object larger than Jupiter (the largest planet in our solar system) but not quite massive enough to become a star. To achieve the finding, they used a new method that could also be applied to learn about the atmospheres of gas-dominated planets outside our solar system.

Described in a paper in the journal Science, the work combines observations by a group of radio telescopes with data from NASA's recently retired infrared observatory, the Spitzer Space Telescope, managed by the agency's Jet Propulsion Laboratory in Southern California.

Officially named 2MASS J10475385+2124234, the target of the new study was a brown dwarf located 32 light-years from Earth -- a stone's throw away, cosmically speaking. The researchers detected winds moving around the planet at 1,425 mph (2,293 kph). For comparison, Neptune's atmosphere features the fastest winds in the solar system, which whip through at more than 1,200 mph (about 2,000 kph).

Measuring wind speed on Earth means clocking the motion of our gaseous atmosphere relative to the planet's solid surface. But brown dwarfs are composed almost entirely of gas, so "wind" refers to something slightly different. The upper layers of a brown dwarf are where portions of the gas can move independently. At a certain depth, the pressure becomes so intense that the gas behaves like a single, solid ball that is considered the object's interior. As the interior rotates, it pulls the upper layers -- the atmosphere -along so that the two are almost in synch.

In their study, the researchers measured the slight difference in speed of the brown dwarf's atmosphere relative to its interior. With an atmospheric temperature of over 1,100 degrees Fahrenheit (600 degrees Celsius), this particular brown dwarf radiates a substantial amount of infrared light. Coupled with its close proximity to Earth, this characteristic made it possible for Spitzer to detect features in the brown dwarf's atmosphere as they rotate in and out of view. The team used those features to clock the atmospheric rotation speed.

To determine the speed of the interior, they focused on the brown dwarf's magnetic field. A relatively recent discovery found that the interiors of brown dwarfs generate strong magnetic fields. As the brown dwarf rotates, the magnetic field accelerates charged particles that in turn produce radio waves, which the researchers detected with the radio telescopes in the Karl G. Jansky Very Large Array in New Mexico.

Planetary Atmospheres

The new study is the first to demonstrate this comparative method for measuring wind speed on a brown dwarf. To gauge its accuracy, the group tested the technique using infrared and radio observations of Jupiter, which is also composed mostly of gas and has a physical structure similar to a small brown dwarf. The team compared the rotation rates of Jupiter's atmosphere and interior using data that was similar to what they were able to collect for the much more distant brown dwarf. They then confirmed their calculation for Jupiter's wind speed using more detailed data collected by probes that have studied Jupiter up close, thus demonstrating that their approach for the brown dwarf worked.

Scientists have previously used Spitzer to infer the presence of winds on exoplanets and brown dwarfs based on variations in the brightness of their atmospheres in infrared light. And data from the High Accuracy Radial velocity Planet Searcher (HARPS) -- an instrument on the European Southern Observatory's La Silla telescope in Chile -- has been used to make a direct measurement of wind speeds on a distant planet.

But the new paper represents the first time scientists have directly compared the atmospheric speed with the speed of a brown dwarf's interior. The method employed could be applied to other brown dwarfs or to large planets if the conditions are right, according to the authors.

"We think this technique could be really valuable to providing insight into the dynamics of exoplanet atmospheres," said lead author Katelyn Allers, an associate professor of physics and astronomy at Bucknell University in Lewisburg, Pennsylvania. "What's really exciting is being able to learn about how the chemistry, the atmospheric dynamics and the environment around an object are interconnected, and the prospect of getting a really comprehensive view into these worlds."

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Distant giant planets form differently than 'failed stars'

A team of astronomers led by Brendan Bowler of The University of Texas at Austin has probed the formation process of giant exoplanets and brown dwarfs, a class of objects that are more massive than giant planets, but not massive enough to ignite nuclear fusion in their cores to shine like true stars.

Using direct imaging with ground-based telescopes in Hawaii -- W. M. Keck Observatory and Subaru Telescope on Maunakea -- the team studied the orbits of these faint companions orbiting stars in 27 systems. These data, combined with modeling of the orbits, allowed them to determine that the brown dwarfs in these systems formed like stars, but the gas giants formed like planets.

The research is published in the current issue of The Astronomical Journal.

In the last two decades, technological leaps have allowed telescopes to separate the light from a parent star and a much-dimmer orbiting object. In 1995, this new capability produced the first direct images of a brown dwarf orbiting a star. The first direct image of planets orbiting another star followed in 2008.

"Over the past 20 years, we've been leaping down and down in mass," Bowler said of the direct imaging capability, noting that the current limit is about 1 Jupiter mass. As the technology has improved, "One of the big questions that has emerged is 'What's the nature of the companions we're finding?'"

Brown dwarfs, as defined by astronomers, have masses between 13 and 75 Jupiter masses. They have characteristics in common with both planets and with stars, and Bowler and his team wanted to settle the question: Are gas giant planets on the outer fringes of planetary systems the tip of the planetary iceberg, or the low-mass end of brown dwarfs? Past research has shown that brown dwarfs orbiting stars likely formed like low-mass stars, but it's been less clear what is the lowest mass companion this formation mechanism can produce.

"One way to get at this is to study the dynamics of the system -- to look at the orbits," Bowler said. Their orbits today hold the key to unlocking their evolution.

Using Keck Observatory's adaptive optics (AO) system with the Near-Infrared Camera, second generation (NIRC2) instrument on the Keck II telescope, as well as the Subaru Telescope, Bowler's team took images of giant planets and brown dwarfs as they orbit their parent stars.

It's a long process. The gas giants and brown dwarfs they studied are so distant from their parent stars that one orbit may take hundreds of years. To determine even a small percentage of the orbit, "You take an image, you wait a year," for the faint companion to travel a bit, Bowler said. Then "you take another image, you wait another year."

This research relied on AO technology, which allows astronomers to correct for distortions caused by the Earth's atmosphere. As AO instruments have continually improved over the past three decades, more brown dwarfs and giant planets have been directly imaged. But since most of these discoveries have been made over the past decade or two, the team only has images corresponding to a few percent of each object's total orbit. They combined their new observations of 27 systems with all of the previous observations published by other astronomers or available in telescope archives.

At this point, computer modeling comes in. Coauthors on this paper have helped create an orbit-fitting code called "Orbitize!" which uses Kepler's laws of planetary motion to identify which types of orbits are consistent with the measured positions, and which are not.

The code generates a set of possible orbits for each companion. The slight motion of each giant planet or brown dwarf forms a "cloud" of possible orbits. The smaller the cloud, the more astronomers are closing in on the companion's true orbit. And more data points -- that is, more direct images of each object as it orbits -- will refine the shape of the orbit.

"Rather than wait decades or centuries for a planet to complete one orbit, we can make up for the shorter time baseline of our data with very accurate position measurements," said team member Eric Nielsen of Stanford University. "A part of Orbitize! that we developed specifically to fit partial orbits, OFTI [Orbits For The Impatient], allowed us to find orbits even for the longest period companions."

Finding the shape of the orbit is key: Objects that have more circular orbits probably formed like planets. That is, when a cloud of gas and dust collapsed to form a star, the distant companion (and any other planets) formed out of a flattened disk of gas and dust rotating around that star.

On the other hand, the ones that have more elongated orbits probably formed like stars. In this scenario, a clump of gas and dust was collapsing to form a star, but it fractured into two clumps. Each clump then collapsed, one forming a star, and the other a brown dwarf orbiting around that star. This is essentially a binary star system, albeit containing one real star and one "failed star."

"Even though these companions are millions of years old, the memory of how they formed is still encoded in their present-day eccentricity," Nielsen added. Eccentricity is a measure of how circular or elongated an object's orbit is.

The results of the team's study of 27 distant companions was unambiguous.

"The punchline is, we found that when you divide these objects at this canonical boundary of more than about 15 Jupiter masses, the things that we've been calling planets do indeed have more circular orbits, as a population, compared to the rest," Bowler said. "And the rest look like binary stars."

The future of this work involves both continuing to monitor these 27 objects, as well as identifying new ones to widen the study. "The sample size is still modest, at the moment," Bowler said. His team is using the Gaia satellite to look for additional candidates to follow up using direct imaging with even greater sensitivity at the forthcoming Giant Magellan Telescope (GMT) and other facilities. UT-Austin is a founding member of the GMT collaboration.

Bowler's team's results reinforce similar conclusions recently reached by the GPIES direct imaging survey with the Gemini Planet Imager, which found evidence for a different formation channel for brown dwarfs and giant planets based on their statistical properties.

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Jupiter-like exoplanets found in sweet spot in most planetary systems

Illustration of Jupiter-like planet orbiting a star.

As planets form in the swirling gas and dust around young stars, there seems to be a sweet spot where most of the large, Jupiter-like gas giants congregate, centered around the orbit where Jupiter sits today in our own solar system.

The location of this sweet spot is between 3 and 10 times the distance Earth sits from our sun (3-10 astronomical units, or AU). Jupiter is 5.2 AU from our sun.

That's just one of the conclusions of an unprecedented analysis of 300 stars captured by the Gemini Planet Imager, or GPI, a sensitive infrared detector mounted on the 8-meter Gemini South telescope in Chile.

The GPI Exoplanet Survey, or GPIES, is one of two large projects that search for exoplanets directly, by blocking stars' light and photographing the planets themselves, instead of looking for telltale wobbles in the star -- the radial velocity method -- or for planets crossing in front of the star -- the transit technique. The GPI camera is sensitive to the heat given off by recently-formed planets and brown dwarfs, which are more massive than gas giant planets, but still too small to ignite fusion and become stars.

The analysis of the first 300 of more than 500 stars surveyed by GPIES, published June 12 in the The Astronomical Journal, "is a milestone," said Eugene Chiang, a UC Berkeley professor of astronomy and member of the collaboration's theory group. "We now have excellent statistics for how frequently planets occur, their mass distribution and how far they are from their stars. It is the most comprehensive analysis I have seen in this field."

The study complements earlier exoplanet surveys by counting planets between 10 and 100 AU, a range in which the Kepler Space Telescope transit survey and radial velocity observations are unlikely to detect planets. It was led by Eric Nielsen, a research scientist at the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University, and involved more than 100 researchers at 40 institutions worldwide, including the University of California, Berkeley.

One new planet, one new brown dwarf

Since the GPIES survey began five years ago, the team has imaged six planets and three brown dwarfs orbiting these 300 stars. The team estimates that about 9 percent of massive stars have gas giants between 5 and 13 Jupiter masses beyond a distance of 10 AU, and fewer than 1 percent have brown dwarfs between 10 and 100 AU.

The new data set provides important insight into how and where massive objects form within planetary systems.

"As you go out from the central star, giant planets become more frequent. Around 3 to 10 AU, the occurrence rate peaks," Chiang said. "We know it peaks because the Kepler and radial velocity surveys find a rise in the rate, going from hot Jupiters very near the star to Jupiters at a few AU from the star. GPI has filled in the other end, going from 10 to 100 AU, and finding that the occurrence rate drops; the giant planets are more frequently found at 10 than 100. If you combine everything, there is a sweet spot for giant planet occurrence around 3 to 10 AU."

"With future observatories, particularly the Thirty-Meter Telescope and ambitious space-based missions, we will start imaging the planets residing in the sweet spot for sun-like stars," said team member Paul Kalas, a UC Berkeley adjunct professor of astronomy.

The exoplanet survey discovered only one previously unknown planet -- 51 Eridani b, nearly three times the mass of Jupiter -- and one previously unknown brown dwarf -- HR 2562 B, weighing in at about 26 Jupiter masses. None of the giant planets imaged were around sun-like stars. Instead, giant gas planets were discovered only around more massive stars, at least 50 percent larger than our sun, or 1.5 solar masses.

"Given what we and other surveys have seen so far, our solar system doesn't look like other solar systems," said Bruce Macintosh, the principal investigator for GPI and a professor of physics at Stanford. "We don't have as many planets packed in as close to the sun as they do to their stars and we now have tentative evidence that another way in which we might be rare is having these kind of Jupiter-and-up planets."

"The fact that giant planets are more common around stars more massive than sun-like stars is an interesting puzzle," Chiang said.

Because many stars visible in the night sky are massive young stars called A stars, this means that "the stars you can see in the night sky with your eye are more likely to have Jupiter-mass planets around them than the fainter stars that you need a telescope to see," Kalas said. "That is kinda cool."

The analysis also shows that gas giant planets and brown dwarfs, while seemingly on a continuum of increasing mass, may be two distinct populations that formed in different ways. The gas giants, up to about 13 times the mass of Jupiter, appear to have formed by accretion of gas and dust onto smaller objects -- from the bottom up. Brown dwarfs, between 13 and 80 Jupiter masses, formed like stars, by gravitational collapse -- from the top down -- within the same cloud of gas and dust that gave rise to the stars.

"I think this is the clearest evidence we have that these two groups of objects, planets and brown dwarfs, form differently," Chiang said. "They really are apples and oranges."

Direct imaging is the future

The Gemini Planet Imager can sharply image planets around distant stars, thanks to extreme adaptive optics, which rapidly detects turbulence in the atmosphere and reduces blurring by adjusting the shape of a flexible mirror. The instrument detects the heat of bodies still glowing from their own internal energy, such as exoplanets that are large, between 2 and 13 times the mass of Jupiter, and young, less than 100 million years old, compared to our sun's age of 4.6 billion years. Even though it blocks most of the light from the central star, the glare still limits GPI to seeing only planets and brown dwarfs far from the stars they orbit, between about 10 and 100 AU.

The team plans to analyze data on the remaining stars in the survey, hoping for greater insight into the most common types and sizes of planets and brown dwarfs.

Chiang noted that the success of GPIES shows that direct imaging will become increasingly important in the study of exoplanets, especially for understanding their formation.

"Direct imaging is the best way at getting at young planets," he said. "When young planets are forming, their young stars are too active, too jittery, for radial velocity or transit methods to work easily. But with direct imaging, seeing is believing."

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Are brown dwarfs failed stars or super-planets?

Artist rendering of a brown dwarf. They are more massive and hotter than planets but lack the nuclear fusion in their core as in normal stars. Two such “failed” stars were detected orbiting the star ? Ophiuchi. They were probably formed in the earlier protoplanetary disk of the star.

Brown dwarfs fill the "gap" between stars and the much smaller planets -- two very different types of astronomical objects. But how they originate has yet to be fully explained. Astronomers from Heidelberg University may now be able to answer that question. They discovered that the star ν Ophiuchi in the Milky Way is being orbited by two brown dwarfs, which in all probability formed along with the star from a gas and dust disk, just as planets do. The research results were published in Astronomy & Astrophysics.

Brown dwarfs orbit either one star or travel in isolation in the vast expanse of the Milky Way. Their mass -- they are at least 13 times heavier than the planet Jupiter -- is sufficient to generate, at least temporarily, energy in their core through nuclear fusion. They are not sufficiently massive, however, to ignite hydrogen in their cores and hence to create their own light. The heat they continue to radiate after formation is how astronomers are able to locate them. It is estimated that up to 100 billion brown dwarfs make their home in the Milky Way. Yet it remains unclear how they form -- whether they are "failed" stars or possibly even super-planets.

The recent discoveries made at the Centre for Astronomy of Heidelberg University (ZAH) could provide an answer. Prof. Dr Andreas Quirrenbach and his team at the Königstuhl State Observatory of the ZAH analysed the variations in radial velocity of the star ν Ophiuchi. Using telescopes in the USA and Japan, the Heidelberg astronomers and others measured the velocity of the star for 11 years. The star has a mass slightly greater than two and half times that of the Sun, and is located approximately 150 light years from Earth in the constellation Ophiuchus.

The Heidelberg team noticed a certain pattern in the measurements, similar to those caused by orbiting planets or binary stars, which is usually nothing out of the ordinary. But in this case, in-depth analysis of the data revealed something extraordinary: apparently, ν Ophiuchi is being orbited by two brown dwarfs with an orbital period of approximately 530 and 3,185 days, which puts them in a 6:1 resonant configuration. So, the brown dwarf closest to ν Ophiuchi orbits its star exactly six times while the other, more distant brown dwarf completes only one orbit.

This discovery sheds completely new light on the evolution of brown dwarfs. Do they develop exclusively like normal stars in interstellar clouds, or can they also form in the so-called protoplanetary disk of gas and dust that surrounds the parent star in the early phase of its formation? "The 6:1 resonance is a strong indication for the latter scenario," explains Prof. Quirrenbach. "Only then could the orbits of the newly developing brown dwarfs adjust to a stable resonance over millions of years."

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When is a nova not a nova? When a white dwarf and a brown dwarf collide

This object is possibly the oldest of its kind ever catalogued: the hourglass-shaped remnant named CK Vulpeculae.

Researchers from Keele University have worked with an international team of astronomers to find for the first time that a white dwarf and a brown dwarf collided in a 'blaze of glory' that was witnessed on Earth in 1670.

Using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, the international team of astronomers, including workers from the Universities of Keele, Manchester, South Wales, Arizona State, Minnesota, Ohio State, Warmia & Mazury, and the South African Astronomical Observatory, found evidence that a white dwarf (the remains of a star like the Sun at the end of its life) and a brown dwarf (a 'failed' star without sufficient mass to sustain thermonuclear fusion) collided in a short-lived blaze of glory that was witnessed on Earth in 1670 as Nova Cygni -- 'a new star below the head of the Swan.' The brown dwarf star was 'shredded' and dumped on the surface of a white dwarf star, leading to the 1670 eruption and the hourglass we see today.

In July of 1670, observers on Earth witnessed a 'new star', or nova, in the constellation Cygnus -- the Swan. Where previously there was no obvious star, there abruptly appeared a star as bright as those in the Plough, that gradually faded, reappeared, and finally disappeared from view.

Modern astronomers studying the remains of this cosmic event initially thought it was triggered by the merging of two main-sequence stars -- stars on the same evolutionary path as our Sun. This so-called 'new star' was long referred to as 'Nova Vulpeculae 1670', and later became known as CK Vulpeculae.

However, we now know that CK Vulpeculae was not what we would today describe as a 'nova', but is in fact the merger of two stars -- a white dwarf and a brown dwarf.

By studying the debris from this explosion -- which takes the form of dual rings of dust and gas, resembling an hourglass with a compact central object -- the research team concluded that a brown dwarf, a so-called failed star without the mass to sustain nuclear fusion, had merged with a white dwarf.

Professor Nye Evans, Professor of Astrophysics at Keele University and co-author on the paper appearing in the Monthly Notices of the Royal Astronomical Society explains:

"CK Vulpeculae has in the past been regarded as the oldest 'old nova'. However, the observations of CK Vulpeculae I have made over the years, using telescopes on the ground and in space, convinced me more and more that this was no nova. Everyone knew what it wasn't -- but nobody knew what it was! But a stellar merger of some sort seemed the best bet. With our ALMA observations of the exquisite dusty hourglass and the warped disc, plus the presence of lithium and peculiar isotope abundances, the jig-saw all fitted together: in 1670 a brown dwarf star was 'shredded' and dumped on the surface of a white dwarf star, leading to the 1670 eruption and the hourglass we see today."

The team of European, American and South African astronomers used the Atacama Large Millimeter/submillimeter Array to examine the remains of the merger, with some interesting findings. By studying the light from two, more distant, stars as they shine through the dusty remains of the merger, the researchers were able to detect the tell-tale signature of the element lithium, which is easily destroyed in stellar interiors.

Dr Stewart Eyres, Deputy Dean of the Faculty of Computing, Engineering and Science at the University of South Wales and lead author on the paper explains:

"The material in the hourglass contains the element lithium, normally easily destroyed in stellar interiors. The presence of lithium, together with unusual isotopic ratios of the elements C, N, O, indicate that an (astronomically!) small amount of material, in the form of a brown dwarf star, crashed onto the surface of a white dwarf in 1670, leading to thermonuclear 'burning', an eruption that led to the brightening seen by the Carthusian monk Anthelme and the astronomer Hevelius, and in the hourglass we see today."

Professor Albert Zijlstra, from The University of Manchester's School of Physics & Astronomy, co-author of the study, says:

"Stellar collisions are the most violent events in the Universe. Most attention is given to collisions between neutrons stars, between two white dwarfs -- which can give a supernova -- and star-planet collisions.

"But it is very rare to actually see a collision, and where we believe one occurred, it is difficult to know what kind of stars collided. The type we believe that happened here is a new one, not previously considered or ever seen before. This is an extremely exciting discovery."

Professor Sumner Starrfield, Regents' Professor of Astrophysics at Arizona State University comments:

"The white dwarf would have been about 10 times more massive than the brown dwarf, so as the brown dwarf spiralled into the white dwarf it would have been ripped apart by the intense tidal forces exerted by the white dwarf. When these two objects collided, they spilled out a cocktail of molecules and unusual element isotopes.

"These organic molecules, which we could not only detect with ALMA, but also measure how they were expanding into the surrounding environment, provide compelling evidence of the true origin of this blast. This is the first time such an event has been conclusively identified.

"Intriguingly, the hourglass is also rich in organic molecules such as formaldehyde (H2CO), methanol (CH3OH) and methanamide (NH2CHO). These molecules would not survive in an environment undergoing nuclear fusion and must have been produced in the debris from the explosion. This lends further support to the conclusion that a brown dwarf met its demise in a star-on-star collision with a white dwarf."

Since most star systems in the Milky Way are binary, stellar collisions are not that rare, the astronomers note.

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Milky Way could have 100 billion brown dwarfs

Artist's impression of a T-type brown dwarf.

Our galaxy could have 100 billion brown dwarfs or more, according to work by an international team of astronomers, led by Koraljka Muzic from the University of Lisbon and Aleks Scholz from the University of St Andrews. On Thursday 6 July Scholz will present their survey of dense star clusters, where brown dwarfs are abundant, at the National Astronomy Meeting at the University of Hull.

Brown dwarfs are objects intermediate in mass between stars and planets, with masses too low to sustain stable hydrogen fusion in their core, the hallmark of stars like the Sun. After the initial discovery of brown dwarfs in 1995, scientists quickly realised that they are a natural by-product of processes that primarily lead to the formation of stars and planets.

All of the thousands of brown dwarfs found so far are relatively close to the Sun, the overwhelming majority within 1500 light years, simply because these objects are faint and therefore difficult to observe. Most of those detected are located in nearby star forming regions, which are all fairly small and have a low density of stars.

In 2006 the team began a new search for brown dwarfs, observing five nearby star forming regions. The Substellar Objects in Nearby Young Clusters (SONYC) survey included the star cluster NGC 1333, 1000 light years away in the constellation of Perseus. That object had about half as many brown dwarfs as stars, a higher proportion than seen before.

To establish whether NGC 1333 was unusual, in 2016 the team turned to another more distant star cluster, RCW 38, in the constellation of Vela. This has a high density of more massive stars, and very different conditions to other clusters.

RCW 38 is 5500 light years away, meaning that the brown dwarfs are both faint, and hard to pick out next to the brighter stars. To get a clear image, Scholz, Muzic and their collaborators used the NACO adaptive optics camera on the European Southern Observatory's Very Large Telescope, observing the cluster for a total of 3 hours, and combining this with earlier work.

The researchers found just as many brown dwarfs in RCW 38 -- about half as many as there are stars -- and realised that the environment where the stars form, whether stars are more or less massive, tightly packed or less crowded, has only a small effect on how brown dwarfs form.

Scholz says: "We've found a lot of brown dwarfs in these clusters. And whatever the cluster type, the brown dwarfs are really common. Brown dwarfs form alongside stars in clusters, so our work suggests there are a huge number of brown dwarfs out there."

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Cold brown dwarf discovered close to our solar system

This gif shows the 'flipbook' from which citizen scientists identified the new brown dwarf, marked with the red circle.

A new citizen-science tool released earlier this year to help astronomers pinpoint new worlds lurking in the outer reaches of our solar system has already led to a discovery: a brown dwarf a little more than 100 light years away from the Sun. Just six days after the launch of the Backyard Worlds: Planet 9 website in February, four different users alerted the science team to the curious object, whose presence has since been confirmed via an infrared telescope. Details were recently published in the Astrophysical Journal Letters.

"I was so proud of our volunteers as I saw the data on this new cold world coming in," said Jackie Faherty, a senior scientist in the American Museum of Natural History's Department of Astrophysics and one of Backyard World's researchers. "It was a feel-good moment for science."

The Backyard Worlds project lets anyone with a computer and an internet connection flip through images taken by NASA's Wide Field Infrared Survey Explorer (WISE) spacecraft. If an object is close enough to Earth, it will appear to "jump" when multiple images taken of the same spot in the sky a few years apart are compared. The goal for Backyard Worlds volunteers -- of which there are more than 37,000 -- is to flag the moving objects they see in these digital flipbooks for further investigation by the science team. So far, volunteers have classified more than 4 million flipbooks.

Days after the Backyard Worlds website debuted on February 15, Bob Fletcher, a science teacher in Tasmania, identified a very faint object moving across the WISE images. It was soon also flagged by three other citizen scientists from Russia, Serbia, and the United States. After some initial investigation by the research team, which originally called the object "Bob's dwarf," Faherty was awarded time on NASA's Infrared Telescope Facility in Hawaii, where she confirmed that it was a previously unknown brown dwarf just a few hundred degrees warmer than Jupiter. The authors say that sky surveys had missed this object because it's too faint. All four volunteers are co-authors on the scientific paper announcing the discovery.

Brown dwarfs, sometimes called "failed stars," are spread throughout the Milky Way. They lack enough mass to sustain nuclear fusion but they are hot enough to glow in the infrared range of the light spectrum.

"Brown dwarfs are strikingly similar to Jupiter so we study their atmospheres in order to look at what weather on other worlds might look like," said Jonathan Gagné, a Backyard Worlds team member from the Carnegie Institution for Science.

Although the Backyard Worlds research team hopes to find the infamous Planet 9 hiding in our own solar system, these brown dwarfs are also exciting discoveries.

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Surprise! When a brown dwarf is actually a planetary mass object

This is an artist's conception of SIMP J013656.5+093347, or SIMP0136 for short, which the research team determined is a planetary like member of a 200-million-year-old group of stars called Carina-Near.

Sometimes a brown dwarf is actually a planet -- or planet-like anyway. A team led by Carnegie's Jonathan Gagné, and including researchers from the Institute for Research on Exoplanets (iREx) at Université de Montréal, the American Museum of Natural History, and University of California San Diego, discovered that what astronomers had previously thought was one of the closest brown dwarfs to our own Sun is in fact a planetary mass object.

Their results are published by The Astrophysical Journal Letters.

Smaller than stars, but bigger than giant planets, brown dwarfs are too small to sustain the hydrogen fusion process that fuels stars and allows them to remain hot and bright for a long time. So after formation, brown dwarfs slowly cool down and contract over time. The contraction usually ends after a few hundred million years, although the cooling is continuous.

"This means that the temperatures of brown dwarfs can range from as hot as stars to as cool as planets, depending on how old they are," said the AMNH's Jackie Faherty, a co-author on this discovery.

The team determined that a well-studied object known as SIMP J013656.5+093347, or SIMP0136 for short, is a planetary like member of a 200-million-year-old group of stars called Carina-Near.

Groups of similarly aged stars moving together through space are considered prime regions to search for free-floating planetary like objects, because they provide the only means of age-dating these cold and isolated worlds. Knowing the age, as well as the temperature, of a free-floating object like this is necessary to determine its mass.

Gagné and the research team were able to demonstrate that at about 13 times the mass of Jupiter, SIMP0136 is right at the boundary that separates brown dwarf-like properties, primarily the short-lived burning of deuterium in the object's core, from planet-like properties.

Free-floating planetary mass objects are valuable because they are very similar to gas giant exoplanets that orbit around stars, like our own Solar System's Jupiter or Saturn, but it is comparatively much easier to study their atmospheres. Observing the atmospheres of exoplanets found within distant star systems is challenging, because dim light emitted by those orbiting exoplanets is overwhelmed by the brightness of their host stars, which blinds the instruments that astronomers use to characterize an exoplanet's atmospheres.

"The implication that the well-known SIMP0136 is actually more planet-like than we previously thought will help us to better understand the atmospheres of giant planets and how they evolve," Gagné said.

They may be easier to study in great detail, but these free-floating worlds are still extremely hard to discover unless scientists spend a lot of time observing them at the telescope, because they can be located anywhere in the sky and they are very hard to tell apart from brown dwarfs or very small stars. For this reason, researchers have confirmed only a handful of free-floating planetary like objects so far.

Étienne Artigau, co-author and leader of the original SIMP0136 discovery, added: "This newest addition to the very select club of free-floating planetary like objects is particularly remarkable, because we had already detected fast-evolving weather patterns on the surface of SIMP0136, back when we thought it was a brown dwarf."

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