Exoplanet-hunting telescope to begin search for another Earth in 2026

Europe's next big space mission -- a telescope that will hunt for Earth-like rocky planets outside of our solar system -- is on course to launch at the end of 2026.

PLATO, or PLAnetary Transits and Oscillations of stars, is being built to find nearby potentially habitable worlds around Sun-like stars that we can examine in detail.

The space telescope will blast into orbit on Europe's new rocket, Ariane-6, which made its maiden flight last week after being developed at a cost of €4billion (£3.4billion).

Dr David Brown, of the University of Warwick, is giving an update on the mission at the Royal Astronomical Society's National Astronomy Meeting at the University of Hull this week.

"PLATO's goal is to search for exoplanets around stars similar to the Sun and at orbital periods long enough for them to be in the habitable zone," he said.

"One of the main mission objectives is to find another Earth-Sun equivalent pair, but it is also designed to carefully and precisely characterise the exoplanets that it finds (i.e. work out their masses, radii, and bulk density)."

PLATO isn't just an exoplanet hunter, however. It is also a stellar science mission.

As well as searching for exoplanets it will study the stars using a range of techniques including asteroseismology (measuring the vibrations and oscillations of stars) to work out their masses, radii, and ages.

Unlike most space telescopes, PLATO has multiple cameras -- including a UK-named one called ArthurEddington, after the famous astronomer and physicist who won the Royal Astronomical Society's Gold Medal in 1924.

It has 24 'Normal' cameras (N-CAMs) and 2 'Fast' cameras (F-CAMs). The N-CAMs are arranged into four groups of six cameras, with the cameras in each group pointing in the same direction but the groups slightly offset.

This gives PLATO a very large field of view, improved scientific performance, redundancy against failures, and a built-in way to identify 'false positive' signals that might mimic an exoplanet transit, Dr Brown explained.

"The planned observing strategy is to stare at two patches of sky, one in the North and one in the South, for two years each," he added.

"The Southern patch of sky has been chosen, while the Northern patch won't be confirmed for another few years."

Several of the spacecraft's components have finished their manufacturing programmes and are close to completing their calibration tests. This includes the UK-provided Front-End Electronics (FEE) for the N-CAMs.

Built by the Mullard Space Science Laboratory of University College London, these operate the cameras, digitise the images, and transfer them to the onboard data processing.

Ten of the final cameras have been built and tested and the first of these was mounted onto the optical bench -- the surface which keeps all cameras pointed in the right direction -- earlier this year.

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Sun-like stars found orbiting hidden companions

Most stars in our universe come in pairs. While our own Sun is a loner, many stars like our Sun orbit similar stars, while a host of other exotic pairings between stars and cosmic orbs pepper the universe. Black holes, for example, are often found orbiting each other. One pairing that has proved to be quite rare is that between a Sun-like star and a type of dead star called a neutron star.

Now, astronomers led by Caltech's Kareem El-Badry have uncovered what appear to be 21 neutron stars in orbit around stars like our Sun. Neutron stars are dense burned-out cores of massive stars that exploded. On their own, they are extremely faint and usually cannot be detected directly. But as a neutron star orbits around a Sun-like star, it tugs on its companion, causing the star to shift back and forth in the sky. Using the European Space Agency's Gaia mission, the astronomers were able to catch these telltale wobbles to reveal a new population of dark neutron stars.

"Gaia is continuously scanning the sky and measuring the wobbles of more than a billion stars, so the odds are good for finding even very rare objects," says El-Badry, an assistant professor of astronomy at Caltech and an adjunct scientist at the Max Planck Institute for Astronomy in Germany.

The new study, which includes a team of co-authors from around the world, was published in The Open Journal for Astrophysics. Data from several ground-based telescopes, including the W. M. Keck Observatoryon Maunakea, Hawai'i; La Silla Observatory in Chile; and the Whipple Observatory in Arizona, were used to follow up the Gaia observations and learn more about the masses and orbits of the hidden neutron stars.

While neutron stars have previously been detected in orbit around stars like our Sun, those systems have all been more compact. With little distance separating the two bodies, a neutron star (which is heavier than a Sun-like star) can steal mass away from its partner. This mass transfer process makes the neutron star shine brightly at X-ray or radio wavelengths. In contrast, the neutron stars in the new study are much farther from their partners -- on the order of one to three times the distance between Earth and the Sun.

That means the newfound stellar corpses are too far from their partners to be stealing material from them. They are instead quiescent and dark. "These are the first neutron stars discovered purely due to their gravitational effects," El-Badry says.

The discovery comes as somewhat of a surprise because it is not clear how an exploded star winds up next to a star like our Sun.

"We still do not have a complete model for how these binaries form," explains El-Badry. "In principle, the progenitor to the neutron star should have become huge and interacted with the solar-type star during its late-stage evolution." The huge star would have knocked the little star around, likely temporarily engulfing it. Later, the neutron star progenitor would have exploded in a supernova, which, according to models, should have unbound the binary systems, sending the neutron stars and Sun-like stars careening in opposite directions.

"The discovery of these new systems shows that at least some binaries survive these cataclysmic processes even though models cannot yet fully explain how," he says.

Gaia was able to find the unlikely companions due to their wide orbits and long periods (the Sun-like stars orbit around the neutron stars with periods of six months to three years). "If the bodies are too close, the wobble will be too small to detect," El-Badry says. "With Gaia, we are more sensitive to the wider orbits." Gaia is also most sensitive to binaries that are relatively nearby. Most of the newly discovered systems are located within 3,000 light-years of Earth -- a relatively small distance compared, for example, to the 100,000 light-year-diameter of the Milky Way Galaxy.

The new observations also suggest just how rare the pairings are. "We estimate that about one in a million solar-type stars is orbiting a neutron star in a wide orbit," he said.

El-Badry also has an interest in finding unseen dormant black holes in orbit with Sun-like stars. Using Gaia data, he has found two of these quiet black holes hidden in our galaxy. One, called Gaia BH1, is the closest known black hole to Earth at 1,600 light-years away.

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Newly discovered carbon monoxide-runaway gap can help identify habitable exoplanets

A carbon monoxide (CO)-runaway gap identified in the atmospheres of Earth-like planets by researchers at Tokyo Tech can help expand the search for habitable planets. This gap, identified through atmospheric modeling, is an indicator of a CO-rich atmosphere on Earth-like planets orbiting Sun-like stars. CO is an important compound for the formation of prebiotic organic compounds, which are building blocks for more complex molecules for the formation of life.

The search for habitable exoplanets involves looking for planets with similar conditions to the Earth, such as liquid water, a suitable temperature range and atmospheric conditions.

One crucial factor is the planet's position in the habitable zone, the region around a star where liquid water could potentially exist on the planet's surface.

NASA's Kepler telescope, launched in 2009, revealed that 20-50% of visible stars may host such habitable Earth-sized rocky planets.

However, the presence of liquid water alone does not guarantee a planet's habitability.

On Earth, carbon compounds such as carbon dioxide (CO2), methane (CH4), and carbon monoxide (CO) played a crucial role in shaping the climate and biogeochemistry and could have contributed to the emergence of life.

Taking this into consideration, a recent study by Associate Professor Kazumi Ozaki from Tokyo Institute of Technology, along with Associate Researcher Yasuto Watanabe from The University of Tokyo, aims to expand the search for habitable planets.

Published in the Astrophysical Journal on 10 January 2024, the researchers used atmospheric modeling to identify conditions that could result in a CO-rich atmosphere on Earth-like planets that orbit sun-like (F-, G-, and K-type) stars.

This phenomenon, known as CO runaway, is suggested by atmospheric models to have possibly occurred in early planetary atmospheres, potentially favoring the emergence of life.

"The possibility of CO runaway is critical in resolving the fundamental problem regarding the origin of life on Earth because various organic compounds suitable for the prebiotic chemistry are more likely to form in a CO-rich atmosphere than in a CO2-rich atmosphere," explains Dr. Ozaki.

The researchers modeled the CO cycle between the atmosphere and the oceans, considering the various sources of CO production, its transport mechanisms and the processes involved in its removal.

The photolysis of CO2, in which CO2 breaks down into CO when exposed to light, was considered the primary source of CO. Additional sources included photochemical reactions in the atmosphere, emissions from volcanic gases, and the hydrothermal decomposition of formaldehyde (H2CO) in the ocean.

The removal of CO from the atmosphere primarily occurred through its reaction with hydroxyl (OH) radicals formed due to the photolysis of water vapor, and to a lesser extent, by deposition to the planet's surface.

The researchers found that a CO runaway occurs when the CO production surpasses the removal by OH radicals.

This can occur due to higher CO2 levels or the presence of reducing gases from volcanoes which compete for the OH radicals.

At a temperature of 277 K, conditions for CO runaway are met when the partial pressure of CO2 exceeds 0.2 bar.

However, at higher temperatures (300 K), a CO runaway needs even higher CO2 and volcanic gas levels due to increased water vapor in the atmosphere, which is a major source of OH radicals.

Once initiated, the CO levels in the atmosphere are limited only by surface deposition, where CO is deposited onto the planet's surface.

Notably, the changes in the CO, CO2 and CH4 levels before and after the runaway effect led to a gap reflected in the phase space defined by the ratios of their partial pressures (pCO/pCO2 and pCH4/pCO2). "Our results suggest that this CO-runaway gap is a general feature of Earth-like lifeless planets orbiting Sun-like stars, providing insights into the characteristics and potential habitability of exoplanets," says Dr. Ozaki.

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Ravenous black hole consumes three Earths'-worth of star every time it passes

A star like our own Sun in a nearby galaxy is gradually being eaten away by a small but ravenous black hole, losing the equivalent mass of three Earths every time it passes close.

The discovery by University of Leicester astronomers is reported today (7 September) in Nature Astronomy and provides a 'missing link' in our knowledge of black holes disrupting orbiting stars. It suggests a whole menagerie of stars in the process of being consumed that still lie undiscovered.

The team was supported by the UK Space Agency and the UK Science and technology Facilities Council (STFC).

The astronomers were alerted to the star by a bright X-ray flash that seemed to come from the centre of the nearby galaxy 2MASX J02301709+2836050, around 500 million light-years away from the Milky Way. Named Swift J0230, it was spotted the moment it happened for the first time using a new tool developed by the scientists for the Neil Gehrels Swift Observatory. They rapidly scheduled further Swift observations of it, finding that instead of decaying away as expected, it would shine brightly for 7-10 days and then abruptly switch off, repeating this process roughly every 25 days.

Similar behaviour has been observed in what are termed quasi-periodic eruptions and periodic nuclear transients, where a star has material ripped away by a black hole as its orbit takes it close by, but they differ in how often they erupt, and in whether it is in X-rays or optical light that the explosion is predominant. The regularity of Swift J0230's emissions fell between the two, suggesting that it forms the 'missing link' between the two types of outburst.

Using the models proposed for these two classes of event as a guide, the scientists concluded that the Swift J0230 outburst represents a star of a similar size to our own sun in an elliptical orbit around a low-mass black hole at the centre of its galaxy. As the star's orbit takes it close to the intense gravitational pull of the black hole, material equivalent to the mass of three Earths is wrenched from the atmosphere of the star and heated up as it falls into the black hole. The intense heat, around 2 million degrees Celsius, releases a huge amount of X-rays which were first picked up by the Swift satellite.

Lead author Dr Phil Evans of the University of Leicester School of Physics and Astronomy said: "This is the first time we've seen a star like our Sun being repeatedly shredded and consumed by a low mass black hole. So-called 'repeated, partial tidal disruption' events are themselves quite a new discovery and seem to fall into two types: those that outburst every few hours, and those that outburst every year or so. This new system falls right into the gap between these, and when you run the numbers, you find the types of objects involved fall nicely into place too."

Dr Rob Eyles-Ferris, who works with Dr Evans on the Swift satellite, recently completed his PhD at Leicester, which included the study of stars being disrupted by black holes. He explains: "In most of the systems we've seen in the past the star is completely destroyed. Swift J0230 is an exciting addition to the class of partially-disrupted stars as it shows us that the two classes of these objects already found are really connected, with our new system giving us the missing link."

Dr Kim Page from the University of Leicester, who worked on the data analysis for the study, said: "Given that we found Swift J0230 within a few months of enabling our new transient-hunting tool, we expect that there are a lot more objects like this out there, waiting to be uncovered."

Dr Chris Nixon is a theoretical astrophysicist who recently moved from the University of Leicester to the University of Leeds. He led the theoretical interpretation of this event. His research is funded by the UK Science and Technology Facilities Council and the Leverhulme Trust.

They estimate that the black hole is around 10,000 to 100,000 times the mass of our sun, which is quite small for the supermassive black holes usually found at the centre of galaxies. The black hole at the centre of our own galaxy is thought to be 4 million solar masses, while most are in the region of 100 million solar masses.

It is the first discovery to be made using the new transient detector for the Swift satellite, developed by the University of Leicester team and running on their computers. When an extreme event takes place, causing an X-ray burst in a region of the sky where there were previously no X-rays, astronomers call it an astronomical X-ray transient. Despite the extreme events they herald, these events are not easy to find, or at least, not quickly -- and so this new tool was developed to look for new types of transients in real time.

Dr Evans adds: "This type of object was essentially undetectable until we built this new facility, and soon after it found this completely new, never-before-seen event. Swift is nearly 20 years old and it's suddenly finding brand new events that we never knew existed. I think it shows that every single time you find a new way of looking at space, you learn something new and find there's something out there you didn't know about before."

Dr Caroline Harper, Head of Space Science at the UK Space Agency, said:"This is yet another exciting discovery from the world-leading Swift mission -- a low mass black hole taking 'bites' from a Sun-like star whenever it orbits close enough.

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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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A young, sun-like star may hold warnings for life on Earth

Astronomers spying on a stellar system located dozens of lightyears from Earth have, for the first time, observed a troubling fireworks show: A star, named EK Draconis, ejected a massive burst of energy and charged particles much more powerful than anything scientists have seen in our own solar system.

The researchers, including astrophysicist Yuta Notsu of the University of Colorado Boulder, will publish their results Dec. 9 in the journal Nature Astronomy.

The study explores a stellar phenomenon called a "coronal mass ejection," sometimes known as a solar storm. Notsu explained that the sun shoots out these sorts of eruptions on a regular basis -- they're made up of clouds of extremely-hot particles, or plasma, that can hurtle through space at speeds of millions of miles per hour. And they're potentially bad news: If a coronal mass ejection hit Earth dead on, it could fry satellites in orbit and shut down the power grids serving entire cities.

"Coronal mass ejections can have a serious impact on Earth and human society," said Notsu, a research associate at the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder and the U.S. National Solar Observatory.

The new study, led by Kosuke Namekata of the National Astronomical Observatory of Japan and formerly a visiting scholar at CU Boulder, also suggests that they can get a lot worse.

In that research, Namekata, Nostu and their colleagues used telescopes on the ground and in space to peer at EK Draconis, which looks like a young version of the sun. In April 2020, the team observed EK Draconis ejecting a cloud of scorching-hot plasma with a mass in the quadrillions of kilograms -- more than 10 times bigger than the most powerful coronal mass ejection ever recorded from a sun-like star.

The event may serve as a warning of just how dangerous the weather in space can be.

"This kind of big mass ejection could, theoretically, also occur on our sun," Notsu said. "This observation may help us to better understand how similar events may have affected Earth and even Mars over billions of years."

Superflares erupt

Notsu explained that coronal mass ejections often come right after a star lets loose a flare, or a sudden and bright burst of radiation that can extend far out into space.

Recent research, however, has suggested that on the sun, this sequence of events may be relatively sedate, at least so far as scientists have observed. In 2019, for example, Notsu and his colleagues published a study that showed that young sun-like stars around the galaxy seem to experience frequent superflares -- like our own solar flares but tens or even hundreds of times more powerful.

Such a superflare could, theoretically, also happen on Earth's sun but not very often, maybe once every several thousand years. Still, it got Notsu's team curious: Could a superflare also lead to an equally super coronal mass ejection?

"Superflares are much bigger than the flares that we see from the sun," Notsu said. "So we suspect that they would also produce much bigger mass ejections. But until recently, that was just conjecture."

Danger from above

To find out, the researchers set their sights on EK Draconis. The curious star, Notsu explained, is about the same size as our sun, but, at just 100 million years old, it's a relative youngster in a cosmic sense.

"It's what our sun looked like 4.5 billion years ago," Notsu said.

The researchers observed the star for 32 nights in winter and spring 2020 using NASA's Transiting Exoplanet Survey Satellite (TESS) and Kyoto University's SEIMEI Telescope. On April 5, Notsu and his colleagues got lucky: The researchers looked on as EK Draconis erupted into a superflare, a really big one. About 30 minutes later, the team observed what appeared to be a coronal mass ejection flying away from the star's surface. The researchers were only able to catch the first step in that ejection's life, called the "filament eruption" phase. But even so, it was a monster, moving at a top speed of roughly 1 million miles per hour.

It may also not bode well for life on Earth: The team's findings hint that the sun could also be capable of such violent extremes. But don't hold your breath -- like superflares, super coronal mass ejections are probably rare around our getting-on-in-years sun.

Still, Notsu noted that huge mass ejections may have been much more common in the early years of the solar system. Gigantic coronal mass ejections, in other words, could have helped to shape planets like Earth and Mars into what they look like today.

"The atmosphere of present-day Mars is very thin compared to Earth's," Notsu said. "In the past, we think that Mars had a much thicker atmosphere. Coronal mass ejections may help us to understand what happened to the planet over billions of years."

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