Most massive stellar black hole in our galaxy found

Astronomers have identified the most massive stellar black hole yet discovered in the Milky Way galaxy. This black hole was spotted in data from the European Space Agency's Gaia mission because it imposes an odd 'wobbling' motion on the companion star orbiting it. Data from the European Southern Observatory's Very Large Telescope (ESO's VLT) and other ground-based observatories were used to verify the mass of the black hole, putting it at an impressive 33 times that of the Sun.

Stellar black holes are formed from the collapse of massive stars and the ones previously identified in the Milky Way are on average about 10 times as massive as the Sun. Even the next most massive stellar black hole known in our galaxy, Cygnus X-1, only reaches 21 solar masses, making this new 33-solar-mass observation exceptional.

Remarkably, this black hole is also extremely close to us -- at a mere 2000 light-years away in the constellation Aquila, it is the second-closest known black hole to Earth. Dubbed Gaia BH3 or BH3 for short, it was found while the team were reviewing Gaia observations in preparation for an upcoming data release. "No one was expecting to find a high-mass black hole lurking nearby, undetected so far," says Gaia collaboration member Pasquale Panuzzo, an astronomer at the Observatoire de Paris, part of France's National Centre for Scientific Research (CNRS). "This is the kind of discovery you make once in your research life."

To confirm their discovery, the Gaia collaboration used data from ground-based observatories, including from the Ultraviolet and Visual Echelle Spectrograph (UVES) instrument on ESO's VLT, located in Chile's Atacama Desert. These observations revealed key properties of the companion star, which, together with Gaia data, allowed astronomers to precisely measure the mass of BH3.

Astronomers have found similarly massive black holes outside our galaxy (using a different detection method), and have theorised that they may form from the collapse of stars with very few elements heavier than hydrogen and helium in their chemical composition. These so-called metal-poor stars are thought to lose less mass over their lifetimes and hence have more material left over to produce high-mass black holes after their death. But evidence directly linking metal-poor stars to high-mass black holes has been lacking until now.

Stars in pairs tend to have similar compositions, meaning that BH3's companion holds important clues about the star that collapsed to form this exceptional black hole. UVES data showed that the companion was a very metal-poor star, indicating that the star that collapsed to form BH3 was also metal-poor -- just as predicted.

The research study, led by Panuzzo, is published today in Astronomy & Astrophysics. "We took the exceptional step of publishing this paper based on preliminary data ahead of the forthcoming Gaia release because of the unique nature of the discovery," says co-author Elisabetta Caffau, also a Gaia collaboration member from the CNRS Observatoire de Paris. Making the data available early will let other astronomers start studying this black hole right now, without waiting for the full data release, planned for late 2025 at the earliest.

Further observations of this system could reveal more about its history and about the black hole itself. The GRAVITY instrument on ESO's VLT Interferometer, for example, could help astronomers find out whether this black hole is pulling in matter from its surroundings and better understand this exciting object.

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The hidden role of the Milky Way in ancient Egyptian mythology

Ancient Egyptians were known for their religious beliefs and astronomical knowledge of the Sun, Moon, and planets, but up until now it has been unclear what role the Milky Way played in Egyptian religion and culture.

A new study by a University of Portsmouth astrophysicist sheds light on the relationship between the Milky Way and the Egyptian sky-goddess Nut.

Nut is goddess of the sky, who is often depicted as a star-studded woman arched over her brother, the earth god Geb.

She protects the earth from being flooded by the encroaching waters of the void, and plays a key role in the solar cycle, swallowing the Sun as it sets at dusk and giving birth to it once more as it rises at dawn.

The paper draws on ancient Egyptian texts and simulations to argue that the Milky Way might have shone a spotlight, as it were, on Nut's role as the sky.

It proposes that in winter, the Milky Way highlighted Nut's outstretched arms, while in summer, it traced her backbone across the heavens.

Associate Professor in Astrophysics, Dr Or Graur, said: "I chanced upon the sky-goddess Nut when I was writing a book on galaxies and looking into the mythology of the Milky Way. I took my daughters to a museum and they were enchanted by this image of an arched woman and kept asking to hear stories about her.

"This sparked my interest and I decided to combine both astronomy and Egyptology to do a double analysis -- astronomical and cross-cultural -- of the sky-goddess Nut, and whether she really could be linked to the Milky Way."

Dr Graur drew from a rich collection of ancient sources including the Pyramid Texts, Coffin Texts, and the Book of Nut and compared them alongside sophisticated simulations of the Egyptian night sky.

He found compelling evidence that the Milky Way highlighted Nut's divine presence.

Furthermore, Dr Graur connected Egyptian beliefs with those of other cultures, showing similarities in how different societies interpret the Milky Way.

He said: "My study also shows that Nut's role in the transition of the deceased to the afterlife and her connection to the annual bird migration are consistent with how other cultures understand the Milky Way. For example, as a spirits' road among different peoples in North and Central America or as the Birds' Path in Finland and the Baltics.

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Stellar collisions produce strange, zombie-like survivors

Despite their ancient ages, some stars orbiting the Milky Way's central supermassive black hole appear deceptively youthful. But unlike humans, who might appear rejuvenated from a fresh round of collagen injections, these stars look young for a much darker reason.

They ate their neighbors.

This is just one of the more peculiar findings from new Northwestern University research. Using a new model, astrophysicists traced the violent journeys of 1,000 simulated stars orbiting our galaxy's central supermassive black hole, Sagittarius A* (Sgr A*).

So densely packed with stars, the region commonly experiences brutal stellar collisions. By simulating the effects of these intense collisions, the new work finds that collision survivors can lose mass to become stripped down, low-mass stars or can merge with other stars to become massive and rejuvenated in appearance.

"The region around the central black hole is dense with stars moving at extremely high speeds," said Northwestern's Sanaea C. Rose, who led the research. "It's a bit like running through an incredibly crowded subway station in New York City during rush hour. If you aren't colliding into other people, then you are passing very closely by them. For stars, these near collisions still cause them to interact gravitationally. We wanted to explore what these collisions and interactions mean for the stellar population and characterize their outcomes."

Rose will present this research at the American Physical Society's (APS) April meeting in Sacramento, California. "Stellar Collisions in the Galactic Center" will take place on Thursday (April 4) as part of the session "Particle Astrophysics and the Galactic Center."

Rose is the Lindheimer Postdoctoral Fellow at Northwestern's Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). She began this work as a Ph.D. candidate at UCLA.

Destined to collide

The center of our Milky Way is a strange and wild place. The gravitational pull of Sgr A* accelerates stars to whip around their orbits at terrifying speeds. And the sheer number of stars packed into the galaxy's center is upwards of a million. The densely packed cluster plus the lightning-fast speeds equal a high-speed demolition derby. In the innermost region -- within 0.1 parsecs of the black hole -- few stars escape unscathed.

"The closest star to our sun is about four light-years away," Rose explained. "Within that same distance near the supermassive black hole, there are more than a million stars. It's an incredibly crowded neighborhood. On top of that, the supermassive black hole has a really strong gravitational pull. As they orbit the black hole, stars can move at thousands of kilometers per second."

Within this tight, hectic neighborhood, stars can collide with other stars. And the closer stars live to the supermassive black hole, the likelihood of collision increases. Curious of the outcomes of these collisions, Rose and her collaborators developed a simulation to trace the fates of stellar populations in the galactic center. The simulation takes several factors into account: density of the stellar cluster, mass of the stars, orbit speed, gravity and distances from the Sgr A*.

From 'violent high fives' to total mergers

In her research, Rose pinpointed one factor that is most likely to determine a star's fate: its distance from the supermassive black hole.

Within 0.01 parsecs from the black hole, stars -- moving at speeds reaching thousands of kilometers per second -- constantly bump into one another. It's rarely a head-on collision and more like a "violent high five," as Rose describes it. The impacts are not strong enough to smash the stars completely. Instead, they shed their outer layers and continue speeding along the collision course.

"They whack into each other and keep going," Rose said. "They just graze each other as though they are exchanging a very violent high five. This causes the stars to eject some material and lose their outer layers. Depending on how fast they are moving and how much they overlap when they collide, they might lose quite a bit of their outer layers. These destructive collisions result in a population of strange, stripped down, low-mass stars."

Outside of 0.01 parsecs, stars move at a more relaxed pace -- hundreds of kilometers per second as opposed to thousands. Because of the slower speeds, these stars collide with one another but then don't have enough energy to escape. Instead, they merge to become more massive. In some cases, they might even merge multiple times to become 10 times more massive than our sun.

"A few stars win the collision lottery," Rose said. "Through collisions and mergers, these stars collect more hydrogen. Although they were formed from an older population, they masquerade as rejuvenated, young-looking stars. They are like zombie stars; they eat their neighbors."

But the youthful appearance comes at the cost of a shorter life expectancy.

"They die very quickly," Rose said. "Massive stars are sort of like giant, gas-guzzling cars. They start with a lot of hydrogen, but they burn through it very, very fast."

Extreme environment 'unlike any other'

Although Rose finds simple joy in studying the bizarre, extreme region near our galactic center, her work also can reveal information about the history of the Milky Way. And because the central cluster is extremely difficult to observe, her team's simulations can illuminate otherwise hidden processes.

"It's an environment unlike any other," Rose said. "Stars, which are under the influence of a supermassive black hole in a very crowded region, are unlike anything we will ever see in our own solar neighborhood. But if we can learn about these stellar populations, then we might be able to learn something new about how the galactic center was assembled. At the very least, it certainly provides a point of contrast for the neighborhood where we live."

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Two of the Milky Way's earliest building blocks identified

Astronomers have identified what could be two of the Milky Way's earliest building blocks: Named "Shakti" and "Shiva," these appear to be the remnants of two galaxies that merged between 12 and 13 billion years ago with an early version of the Milky Way, contributing to our home galaxy's initial growth. The new find is the astronomical equivalent of archeologists identifying traces of an initial settlement that grew into a large present-day city. It required combining data for nearly 6 million stars from ESA's Gaia mission with measurements from the SDSS survey. The results have been published in the Astrophysical Journal.

The early history of our home galaxy, the Milky Way, is one of joining smaller galaxies, which makes for fairly large building blocks. Now, Khyati Malhan and Hans-Walter Rix of the Max Planck Institute for Astronomy have succeeded in identifying what could be two of the earliest building blocks that can still be recognized as such today: proto-galactic fragments that merged with an early version of our Milky Way between 12 and 13 billion years ago, at the very beginning of the era of galaxy formation in the Universe. The components, which the astronomers have named Shakti and Shiva, were identified by combining data from ESA's astrometry satellite Gaia with data from the SDSS survey. For astronomers, the result is the equivalent of finding traces of an initial settlement that grew into a large present-day city.

Tracing the origins of stars that came from other galaxies

When galaxies collide and merge, several processes happen in parallel. Each galaxy carries along its own reservoir of hydrogen gas. Upon collision, those hydrogen gas clouds are destabilized, and numerous new stars are formed inside. Of course, the incoming galaxies also already have their own stars, and in a merger, stars from the galaxies will mingle. In the long run, such "accreted stars" will also account for some of the stellar population of the newly-formed combined galaxy. Once the merger is completed, it might seem hopeless to identify which stars came from which predecessor galaxy. But in fact, at least some ways of tracing back stellar ancestry exist.

Help comes from basic physics. When galaxies collide and their stellar populations mingle, most of the stars retain very basic properties, which are directly linked to the speed and direction of the galaxy in which they originated. Stars from the same pre-merger galaxy share similar values for both their energy and what physicists call angular momentum -- the momentum associated with orbital motion or rotation. For stars moving in a galaxy's gravitational field, both energy and angular momentum are conserved: they remain the same over time. Look for large groups of stars with similar, unusual values for energy and angular momentum -- and chances are, you might find a merger remnant.

Additional pointers can assist identification. Stars that formed more recently contain more heavier elements, what astronomers call "metals," than stars that formed a long time ago. The lower the metal content ("metallicity"), the earlier the star presumably formed. When trying to identify stars that already existed 13 billion years ago, one should look for stars with very low metal content ("metal-poor").

Virtual excavations in a large data set

Identifying the stars that joined our Milky Way as parts of another galaxy has only become possible comparatively recently. It requires large, high-quality data sets, and the analysis involves sifting the data in clever ways so as to identify the searched-for class of objects. This kind of data set has only been available for a few years. The ESA astrometry satellite Gaia provides an ideal data set for this kind of big-data galactic archeology. Launched in 2013, it has produced an increasingly accurate data set over the past decade, which by now includes positions, changes in position and distances for almost 1.5 billion stars within our galaxy.

Gaia data revolutionized studies of the dynamics of stars in our home galaxy, and has already led to the discovery of previously unknown substructures. This includes the so-called Gaia Enceladus/Sausage stream, a remnant of the most recent larger merger our home galaxy has undergone, between 8 and 11 billion years ago. It also includes two structures identified in 2022: the Pontus stream identified by Malhan and colleagues and the "poor old heart" of the Milky Way identified by Rix and colleagues. The latter is a population of stars that newly formed during the initial mergers that created the proto-Milky Way, and continue to reside in our galaxy's central region.

Traces of Shakti and Shiva

For their present search, Malhan and Rix used Gaia data combined with detailed stellar spectra from the Sloan Digital Sky Survey (DR17). The latter provide detailed information about the stars' chemical composition. Malhan says: "We observed that, for a certain range of metal-poor stars, stars were crowded around two specific combinations of energy and angular momentum."

In contrast with the "poor old heart," which was also visible in those plots, the two groups of like-minded stars had comparatively large angular momentum, consistent with groups of stars that had been part of separate galaxies which had merged with the Milky Way. Malhan has named these two structures Shakti and Shiva, the latter one of the principal deities of Hinduism and the former a female cosmic force often portrayed as Shiva's consort.

Their energy and angular momentum values, plus their overall low metallicity on par with that of the "poor old heart," makes Shakti and Shiva good candidates for some of the earliest ancestors of our Milky Way. Rix says: "Shakti and Shiva might be the first two additions to the 'poor old heart' of our Milky Way, initiating its growth towards a large galaxy."

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Astronomers spot oldest 'dead' galaxy yet observed

A galaxy that suddenly stopped forming new stars more than 13 billion years ago has been observed by astronomers.

Using the James Webb Space Telescope, an international team of astronomers led by the University of Cambridge have spotted a 'dead' galaxy when the universe was just 700 million years old, the oldest such galaxy ever observed.

This galaxy appears to have lived fast and died young: star formation happened quickly and stopped almost as quickly, which is unexpected for so early in the universe's evolution. However, it is unclear whether this galaxy's 'quenched' state is temporary or permanent, and what caused it to stop forming new stars.

The results, reported in the journal Nature, could be important to help astronomers understand how and why galaxies stop forming new stars, and whether the factors affecting star formation have changed over billions of years.

"The first few hundred million years of the universe was a very active phase, with lots of gas clouds collapsing to form new stars," said Tobias Looser from the Kavli Institute for Cosmology, the paper's first author. "Galaxies need a rich supply of gas to form new stars, and the early universe was like an all-you-can-eat buffet."

"It's only later in the universe that we start to see galaxies stop forming stars, whether that's due to a black hole or something else," said co-author Dr Francesco D'Eugenio, also from the Kavli Institute for Cosmology.

Astronomers believe that star formation can be slowed or stopped by different factors, all of which will starve a galaxy of the gas it needs to form new stars. Internal factors, such as a supermassive black hole or feedback from star formation, can push gas out of the galaxy, causing star formation to stop rapidly. Alternatively, gas can be consumed very quickly by star formation, without being promptly replenished by fresh gas from the surroundings of the galaxy, resulting in galaxy starvation.

"We're not sure if any of those scenarios can explain what we've now seen with Webb," said co-author Professor Roberto Maiolino. "Until now, to understand the early universe, we've used models based on the modern universe. But now that we can see so much further back in time, and observe that the star formation was quenched so rapidly in this galaxy, models based on the modern universe may need to be revisited."

Using data from JADES (JWST Advanced Deep Extragalactic Survey), the astronomers determined that this galaxy experienced a short and intense period of star formation over a period between 30 and 90 million years. But between 10 and 20 million years before the point in time where it was observed with Webb, star formation suddenly stopped.

"Everything seems to happen faster and more dramatically in the early universe, and that might include galaxies moving from a star-forming phase to dormant or quenched," said Looser.

Astronomers have previously observed dead galaxies in the early universe, but this galaxy is the oldest yet -- just 700 million years after the big bang, more than 13 billion years ago. This observation is one of the deepest yet made with Webb.

In addition to the oldest, this galaxy is also relatively low mass -- about the same as the Small Magellanic Cloud (SMC), a dwarf galaxy near the Milky Way, although the SMC is still forming new stars. Other quenched galaxies in the early universe have been far more massive, but Webb's improved sensitivity allows smaller and fainter galaxies to be observed and analysed.

The astronomers say that although it appears dead at the time of observation, it's possible that in the roughly 13 billion years since, this galaxy may have come back to life and started forming new stars again.

"We're looking for other galaxies like this one in the early universe, which will help us place some constraints on how and why galaxies stop forming new stars," said D'Eugenio. "It could be the case that galaxies in the early universe 'die' and then burst back to life -- we'll need more observations to help us figure that out."

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Black hole at center of the Milky Way resembles a football

The supermassive black hole in the center of the Milky Way is spinning so quickly it is warping the spacetime surrounding it into a shape that can look like a football, according to a new study using data from NASA's Chandra X-ray Observatory and the U.S. National Science Foundation's Karl G. Jansky Very Large Array (VLA). That football shape suggests the black hole is spinning at a substantial speed, which researchers estimated to be about 60% of its potential limit.

The work, led by Penn State Berks Professor of Physics Ruth Daly, was published in the Monthly Notices of the Royal Astronomical Society.

Astronomers call this giant black hole Sagittarius A* (Sgr A*). It is located about 26,000 light-years away from Earth in the center of the galaxy. To determine how quickly Sgr A* is spinning -- one of its fundamental properties, along with mass -- the researchers applied a method that uses X-ray and radio data to assess how material is flowing towards and away from the black hole. The method was developed and published by Daly in 2019 in The Astrophysical Journal.

"Our work may help settle the question of how fast our galaxy's supermassive black hole is spinning," Daly said. "Our results indicate that Sgr A* is spinning very rapidly, which is interesting and has far-reaching implications."

The team found the angular velocity -- the number of revolutions per second -- of Sgr A*'s spin is about 60% of the maximum possible value, a limit set because material cannot travel faster than the speed of light.

Past estimations of Sgr A*'s speed have been made with different techniques and by other astronomers, with results ranging from no rotation at all to spinning at almost the maximum rate.

"This work, however, shows that this could change if the amount of material in the vicinity of Sgr A* increases," Daly said.

As a black hole rotates, it pulls "spacetime" -- the combination of time and the three dimensions of space -- and nearby matter. The gravitational pull also squashes the spacetime, altering its shape depending on how it's observed. Spacetime appears circular if the black hole is viewed from the top. From the side, however, the spacetime is shaped like a football. The faster the spin, the flatter the football.

The spin can also serve as an energy source, Daly said, if matter -- such as gas or the remnants of a star that wanders too close -- exists in the vicinity of the black hole. As the black hole spins, matter can escape in the form of narrow jets called collimated outflows. However, Sgr A* currently has limited nearby matter, so the black hole has been relatively quiet, with weakly collimated outflows, in recent millennia.

"A spinning black hole is like a rocket on the launch pad," said Biny Sebastian, a co-author from the University of Manitoba in Winnipeg, Canada. "Once material gets close enough, it's like someone has fueled the rocket and hit the 'launch' button."

This means that in the future, if the properties of the matter and the magnetic field strength close to the black hole change, part of the enormous energy of the black hole's spin could drive more powerful outflows. This source material could come from gas or from the remnants of a star torn apart by the black hole's gravity if that star wanders too close to Sgr A*.

"Jets powered and collimated by a galaxy's spinning central black hole can profoundly affect the gas supply for an entire galaxy, which affects how quickly and even whether stars can form," said co-author Megan Donahue from Michigan State University. "The 'Fermi bubbles' seen in X-rays and gamma rays around our Milky Way's black hole show the black hole was probably active in the past. Measuring the spin of our black hole is an important test of this scenario."

Fermi bubbles refer to structures that emit gamma rays above and below the black hole that researchers have theorized resulted from prior massive outflows.

The researchers used the outflow method to determine the spin of Sgr A*. Daly's approach incorporates consideration of the relationship between the spin of the black hole and its mass, the properties of the matter near the black hole and the outflow properties. The collimated outflow produces the radio waves, while the disk of gas surrounding the black hole emits X-rays. The researchers combined observational data from Chandra and the VLA with an independent estimate of the black hole's mass from other telescopes to inform the outflow method and determine the black hole's spin.

"We have a special view of Sgr A* because it is the nearest supermassive black hole to us," said co-author Anan Lu from McGill University in Montreal, Canada. "Although it's quiet right now, our work shows that in the future it will give an incredibly powerful kick to surrounding matter. That might happen in a thousand or a million years, or it could happen in our lifetimes."

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Lightest black hole or heaviest neutron star? MeerKAT uncovers a mysterious object in Milky Way

An international team of astronomers have found a new and unknown object in the Milky Way that is heavier than the heaviest neutron stars known and yet simultaneously lighter than the lightest black holes known.

Using the MeerKAT Radio Telescope, astronomers from a number of institutions including The University of Manchester and the Max Planck Institute for Radio Astronomy in Germany found an object in orbit around a rapidly spinning millisecond pulsarlocated around 40,000 light years away in a dense group of stars known as a globular cluster.

Using the clock-like ticks from the millisecond pulsar they showed that the massive object lies in the so-called black hole mass gap.

It could be the first discovery of the much-coveted radio pulsar -- black hole binary; a stellar pairing that could allow new tests of Einstein's general relativity and open doors to the study of black holes.

The results are published today in the journal Science.

UK project lead Ben Stappers, Professor of Astrophysics at The University of Manchester, said: "Either possibility for the nature of the companion is exciting. A pulsar-black hole system will be an important target for testing theories of gravity and a heavy neutron star will provide new insights in nuclear physics at very high densities."

When a neutron star -- the ultra-dense remains of dead star -- acquire too much mass, usually by consuming or colliding with another star, they will collapse. What they become after they collapse is the cause of much speculation, but it is believed that they could become black holes -- objects so gravitationally attractive that even light cannot escape them.

Astronomers believe that the total mass required for a neutron star to collapse is 2.2 times the mass of the sun. Theory, backed by observation, tells us that the lightest black holes created by these stars are much larger, at about five times more massive than the Sun, giving rise to what is known as the 'black hole mass gap'.

The nature of compact objects in this mass gap is unknown and detailed study has so far proved challenging. The discovery of the object may help finally understand these objects.

Prof Stappers, added: "The ability of the extremely sensitive MeerKAT telescope to reveal and study these objects is a enabling a great step forward and provides us with a glimpse of what will be possible with the Square Kilometre Array."

The discovery of the object was made while observing a large cluster of stars known as NGC 1851 located in the southern constellation of Columba, using the MeerKAT telescope.

The globular cluster NGC 1851 is a dense collection of old stars that are much more tightly packed than the stars in the rest of the Galaxy. Here, it is so crowded that the stars can interact with each other, disrupting orbits and in the most extreme cases colliding.

The astronomers, part of the international Transients and Pulsars with MeerKAT (TRAPUM) collaboration, believe that it is one such collision between two neutron stars that is proposed to have created the massive object that now orbits the radio pulsar.

The team were able to detect faint pulses from one of the stars, identifying it as a radio pulsar -- a type of neutron star that spins rapidly and shines beams of radio light into the Universe like a cosmic lighthouse.

The pulsar spins more than 170 times a second, with every rotation producing a rhythmic pulse, like the ticking of a clock. The ticking of these pulses is incredibly regular and by observing how the times of the ticks change, using a technique called pulsar timing, they were able to make extremely precise measurements of its orbital motion.

Ewan Barr from Max Planck Institute for Radio Astronomy, who led the study with his colleague Arunima Dutta, explained: "Think of it like being able to drop an almost perfect stopwatch into orbit around a star almost 40,000 light years away and then being able to time those orbits with microsecond precision."

The regular timing also allowed a very precise measurement of the system's location, showing that the object in orbit with the pulsar was no regular star but an extremely dense remnant of a collapsed star. Observations also showed that the companion has a mass that was simultaneously bigger than that of any known neutron star and yet smaller than that of any known black hole, placing it squarely in the black-hole mass gap.

While the team cannot conclusively say whether they have discovered the most massive neutron star known, the lightest black hole known or even some new exotic star variant, what is certain is that they have uncovered a unique laboratory for probing the properties of matter under the most extreme conditions in the Universe.

Arunima Dutta concludes: "We're not done with this system yet.

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Astronomers detect seismic ripples in ancient galactic disk

A new snapshot of an ancient, far-off galaxy could help scientists understand how it formed and the origins of our own Milky Way.

At more than 12 billion years old, BRI 1335-0417 is the oldest and furthest known spiral galaxy in our universe.

Lead author Dr Takafumi Tsukui said a state-of-the-art telescope called ALMA allowed them to look at this ancient galaxy in much greater detail.

"Specifically, we were interested in how gas was moving into and throughout the galaxy," Dr Tsukui said.

"Gas is a key ingredient for forming stars and can give us important clues about how a galaxy is actually fuelling its star formation."

In this case, the researchers were able to not only capture the motion of the gas around BRI 1335-0417, but also reveal a seismic wave forming -- a first in this type of early galaxy.

The galaxy's disk, a flattened mass of rotating stars, gas and dust, moves in a way not dissimilar to ripples spreading on a pond after a stone is thrown in.

"The vertically oscillating motion of the disk is due to an external source, either from new gas streaming into the galaxy or by coming into contact with other smaller galaxies," Dr Tsukui said.

"Both possibilities would bombard the galaxy with new fuel for star formation.

"Additionally, our study revealed a bar-like structure in the disk. Galactic bars can disrupt gas and transport it towards the galaxy's centre. The bar discovered in BRI 1335-0417 is the most distant known structure of this kind.

"Together, these results show the dynamic growth of a young galaxy."

Because BRI 1335-0417 is so far away, its light takes longer to reach Earth.

The images seen through a telescope in the present day are a throwback to the galaxy's early days -- when the Universe was just 10 per cent of its current age.

"Early galaxies have been found to form stars at a much faster rate than modern galaxies. This is true for BRI 1335-0417, which, despite having a similar mass to our Milky Way, forms stars at rate a few hundred times faster," co-author Associate Professor Emily Wisnioski said.

"We wanted to understand how gas is supplied to keep up with this rapid rate of star formation.

"Spiral structures are rare in the early Universe, and exactly how they form also remains unknown. This study also gives us crucial information on the most likely scenarios.

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Ancient stars made extraordinarily heavy elements

How heavy can an element be? An international team of researchers has found that ancient stars were capable of producing elements with atomic masses greater than 260, heavier than any element on the periodic table found naturally on Earth. The finding deepens our understanding of element formation in stars.

We are, literally, made of star stuff. Stars are element factories, where elements constantly fuse or break apart to create other lighter or heavier elements.

When we refer to light or heavy elements, we're talking about their atomic mass.

Broadly speaking, atomic mass is based on the number of protons and neutrons in the nucleus of one atom of that element.

The heaviest elements are only known to be created in neutron stars via the rapid neutron capture process, or r-process.

Picture a single atomic nucleus floating in a soup of neutrons.

Suddenly, a bunch of those neutrons get stuck to the nucleus in a very short time period -- usually in less than one second -- then undergo some internal neutron-to-proton changes, and voila!

A heavy element, such as gold, platinum or uranium, forms.

The heaviest elements are unstable or radioactive, meaning they decay over time.

One way that they do this is by splitting, a process called fission.

"The r-process is necessary if you want to make elements that are heavier than, say, lead and bismuth," says Ian Roederer, associate professor of physics at North Carolina State University and lead author of the research.

Roederer was previously at the University of Michigan.

"You have to add many neutrons very quickly, but the catch is that you need a lot of energy and a lot of neutrons to do so," Roederer says.

"We have a general idea of how the r-process works, but the conditions of the process are quite extreme," Roederer says.

"We don't have a good sense of how many different kinds of sites in the universe can generate the r-process, we don't know how the r-process ends, and we can't answer questions like, how many neutrons can you add? Or, how heavy can an element be? So we decided to look at elements that could be made by fission in some well-studied old stars to see if we could start to answer some of these questions."

The team took a fresh look at the amounts of heavy elements in 42 well-studied stars in the Milky Way.

The stars were known to have heavy elements formed by the r-process in earlier generations of stars.

By taking a broader view of the amounts of each heavy element found in these stars collectively, rather than individually as is more common, they identified previously unrecognized patterns.

Those patterns signaled that some elements listed near the middle of the periodic table -- such as silver and rhodium -- were likely the remnants of heavy element fission.

The team was able to determine that the r-process can produce atoms with an atomic mass of at least 260 before they fission.

"That 260 is interesting because we haven't previously detected anything that heavy in space or naturally on Earth, even in nuclear weapon tests," Roederer says.

"But seeing them in space gives us guidance for how to think about models and fission -- and could give us insight into how the rich diversity of elements came to be."

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Astronomers determine the age of three mysterious baby stars at the heart of the Milky Way

Through analysis of high-resolution data from a ten-metre telescope in Hawaii, researchers at Lund University in Sweden have succeeded in generating new knowledge about three stars at the very heart of the Milky Way. The stars proved to be unusually young with a puzzling chemical composition that surprised the researchers.

The study, which has been published in The Astrophysical Journal Letters, examined a group of stars located in the nuclear star cluster that makes up the heart of the galaxy.

It concerns three stars that are difficult to study because they are extremely far away from our solar system, and hidden behind enormous clouds of dust and gas that block out light.

The fact that the area is also full of stars makes it very complicated to discern individual stars.

In a previous study, the researchers put forward a hypothesis that these specific stars in the middle of the Milky Way could be unusually young.

"We can now confirm this. In our study we have been able to date three of these stars as relatively young, at least as far as astronomers are concerned, with ages of 100 million to about 1 billion years. This can be compared with the sun, which is 4.6 billion years old," says Rebecca Forsberg, researcher in astronomy at Lund University.

The nuclear star cluster has mainly been seen, quite rightly, as a very ancient part of the galaxy.

But the researchers' new discovery of such young stars indicates that there is also active star formation going on in this ancient component of the Milky Way.

However, dating stars 25,000 light years from Earth is not something that can be done in a hurry.

The researchers used high-resolution data from the Keck II telescope in Hawaii, one of the world's largest telescopes with a mirror ten metres in diameter.

For further verification, they then measured how much of the heavy element, iron, the stars contained.

The element is important for tracing the galaxy's development, as the theories the astronomers have about how stars are formed and galaxies develop indicate that young stars have more of the heavy elements, as heavy elements are formed to an increasing extent over time in the universe.

To determine the level of iron, the astronomers observed the stars' spectra in infrared light which, compared with optical light, are parts of the light spectrum that can more easily shine through the densely dust-laden parts of the Milky Way.

It was shown that the iron levels varied considerably, which surprised the researchers.

"The very wide spread of iron levels could indicate that the innermost parts of the galaxy are incredibly inhomogeneous, i.e. unmixed. This is something we had not expected and not only says something about how the centre of the galaxy appears, but also how the early universe may have looked," says Brian Thorsbro, researcher in astronomy at Lund University.

The study sheds significant light on our understanding of the early universe and the functioning of the very centre of the Milky Way.

The results may also be of benefit to inspire continued and future explorations of the heart of the galaxy, as well as the further development of models and simulations of the formation of galaxies and stars.

"Personally, I think it is very exciting that we can now study the very centre of our galaxy with such a high level of detail. These types of measurements have been standard for observations of the galactic disc where we are located, but have beenunreachable goal for more faraway and exotic parts of the galaxy. We can learn a lot about how our home galaxy was formed and developed from such studies," concludes Rebecca Forsberg.

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Why the vast supergalactic plane is teeming with only one type of galaxy

Our own Milky Way galaxy is part of a much larger formation, the local Supercluster structure, which contains several massive galaxy clusters and thousands of individual galaxies. Due to its pancake-like shape, which measures almost a billion light years across, it is also referred to as the Supergalactic Plane.

Most galaxies in the universe fall into one of two categories: firstly, elliptical galaxies, made mostly of old stars and containing typically extremely massive central black holes, and secondly actively star-forming disk galaxies, with a spiral-like structure similar to the Milky Way's. Both types of galaxies are also found in the Local Supercluster, but while the Supergalactic Plane is teeming with bright ellipticals, bright disk galaxies are conspicuously absent.

A cosmic anomaly challenges the standard model of cosmology

This peculiar segregation of galaxies in the Local Universe, which has been known since the 1960s, features prominently in a recent list of "cosmic anomalies" compiled by renowned cosmologist and 2019 Nobel laureate Jim Peebles.

Now an international team led by University of Helsinki astrophysicists Till Sawala and Peter Johansson appear to have found an explanation.

In an article published in Nature Astronomy, they show how the different distributions of elliptical and disk galaxies arise naturally due to the different environments found inside and outside of the Supergalactic Plane.

"In the dense galaxy clusters that are found on the Supergalactic Plane, galaxies experience frequent interactions and mergers, which leads to the formation of ellipticals and the growth of supermassive black holes. By contrast, away from the plane, galaxies can evolve in relative isolation, which helps them preserve their spiral structure," says Till Sawala.

In their work, the team made use of the SIBELIUS (Simulations Beyond The Local Universe) simulation, that follows the evolution of the universe over 13.8 billion years, from the early universe to the present.

It was run on supercomputers in England and on CSC's Mahti supercomputer in Finland.

While most similar simulations consider random patches of the universe which cannot be directly compared to observations, the SIBELIUS simulation aims to precisely reproduce the observed structures, including the Local Supercluster.

The final simulation result is remarkably consistent with the observations.

"By chance, I was invited to a symposium in honour of Jim Peebles last December, where he presented the problem in his lecture. And I realised that we had already completed a simulation that might contain the answer," comments Till Sawala.

"Our research shows that the known mechanisms of galaxy evolution also work in this unique cosmic environment."

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NASA's Webb reveals new features in heart of Milky Way

The latest image from NASA's James Webb Space Telescope shows a portion of the dense center of our galaxy in unprecedented detail, including never-before-seen features astronomers have yet to explain. The star-forming region, named Sagittarius C (Sgr C), is about 300 light-years from the Milky Way's central supermassive black hole, Sagittarius A*.

"There's never been any infrared data on this region with the level of resolution and sensitivity we get with Webb, so we are seeing lots of features here for the first time," said the observation team's principal investigator Samuel Crowe, an undergraduate student at the University of Virginia in Charlottesville.

"Webb reveals an incredible amount of detail, allowing us to study star formation in this sort of environment in a way that wasn't possible previously."

"The galactic center is the most extreme environment in our Milky Way galaxy, where current theories of star formation can be put to their most rigorous test," added professor Jonathan Tan, one of Crowe's advisors at the University of Virginia.

Protostars

Amid the estimated 500,000 stars in the image is a cluster of protostars -- stars that are still forming and gaining mass -- producing outflows that glow like a bonfire in the midst of an infrared-dark cloud.

At the heart of this young cluster is a previously known, massive protostar over 30 times the mass of our Sun.

The cloud the protostars are emerging from is so dense that the light from stars behind it cannot reach Webb, making it appear less crowded when in fact it is one of the most densely packed areas of the image.

Smaller infrared-dark clouds dot the image, looking like holes in the starfield.

That's where future stars are forming.

Webb's NIRCam (Near-Infrared Camera) instrument also captured large-scale emission from ionized hydrogen surrounding the lower side of the dark cloud, shown cyan-colored in the image.

Typically, Crowe says, this is the result of energetic photons being emitted by young massive stars, but the vast extent of the region shown by Webb is something of a surprise that bears further investigation.

Another feature of the region that Crowe plans to examine further is the needle-like structures in the ionized hydrogen, which appear oriented chaotically in many directions.

"The galactic center is a crowded, tumultuous place. There are turbulent, magnetized gas clouds that are forming stars, which then impact the surrounding gas with their outflowing winds, jets, and radiation," said Rubén Fedriani, a co-investigator of the project at the Instituto Astrofísica de Andalucía in Spain.

"Webb has provided us with a ton of data on this extreme environment, and we are just starting to dig into it."

Around 25,000 light-years from Earth, the galactic center is close enough to study individual stars with the Webb telescope, allowing astronomers to gather unprecedented information on how stars form, and how this process may depend on the cosmic environment, especially compared to other regions of the galaxy.

For example, are more massive stars formed in the center of the Milky Way, as opposed to the edges of its spiral arms?

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Mystery resolved: Black hole feeding and feedback at the center of an active galaxy

An international research team led by Takuma Izumi, an assistant professor at the National Astronomical Observatory of Japan, has observed in high resolution (approximately 1 light year) the active galactic nucleus of the Circinus Galaxy -- one of the closest major galaxies to the Milky Way. The observation was made possible by the Atacama Large Millimeter/Submillimeter Array (ALMA) astronomical observatory in Chile.

This breakthrough marks the world's first quantitative measurement at this scale of gas flows and their structures of a nearby supermassive black hole in all phase gases, including plasma, atomic, and molecular. Such high resolution allowed the team to team to capture the accretion flow heading towards the supermassive black hole, revealing that this accretion flow is generated by a physical mechanism known as 'gravitational instability.' Furthermore, the team also found that a significant portion of this accretion flow does not contribute to the growth of the black hole. Instead, most of the gas is expelled from the vicinity of the black hole as atomic or molecular outflows, and returns to the gas disk to participate again into an accretion flow towards the black hole, much like how water gets recycled in a water fountain. These findings represent a crucial advancement towards a greater understanding of the growth mechanisms of supermassive black holes.

These observation results were published in Science on November 2, 2023.

'Supermassive black holes,' with masses exceeding a million times that of the Sun, exist at the centers of many galaxies. But astronomers have long pondered the mechanisms responsible their formation. One proposed mechanism, as outlined in previous research, suggests that gas accretes onto the black hole as it gravitates towards the center of the host galaxy.

As gas approaches the supermassive black holes, the intense gravitational pull of the black hole causes the gas to accelerate. The resulting increase in friction between gas particles leads to the gas heating up to temperatures as high as several million degrees and results in the emission of brilliant light. Known as an active galactic nucleus (AGN), the brightness can at times surpass the combined light of all the stars in the galaxy. Interestingly, a portion of the gas that falls towards the black hole (accretion flow) is thought to be blown away by the immense energy of this active galactic nucleus, leading to outflows.

Previous theoretical and observational studies have provided detailed insights into gas accretion mechanisms from the 100,000 light-years scale down to a scale of a few hundred light-years at the center. However, gas accretion occurs a few dozen light-years from the galactic center. This limited spacial scale has hindered further understanding of the accretion process. For instance, to comprehend quantitatively the growth of black holes, it is necessary to measure the accretion flow rate (how much gas is flowing in) and to determine the amounts and types of gases (plasma, atomic gas, molecular gas) that are expelled as outflows at that small scale. Unfortunately, observational understanding has not progressed significantly until now.

"Observations of multiphase gases can provide a more comprehensive and thorough understanding of the distribution and dynamics of matter around a black hole and our observation marks the highest resolution ever achieved for multiphase gas observations in an active galactic nucleus," points out Izumi.

Izumi and his colleagues initially captured, for the first time, the accretion flow heading towards the supermassive black hole within the high-density gas disk that extends over several light-years from the galactic center. Identifying this accretion flow had long been a challenge due to the small scale of the region and the complex motions of gas near the galactic center. However, the research team pinpointed the location where the foreground molecular gas was absorbing the light from the active galactic nucleus shining brightly in the background. Detailed analysis revealed that this absorbing material is moving away from Earth. As the absorbing material consistently resides between the active galactic nucleus and Earth, this indicates that the team has successfully captured the accretion flow heading toward the active galactic nucleus.

The study also elucidated the physical mechanism responsible for inducing this gas accretion. The observed gas disk exhibited a gravitational force so substantial that it could not be sustained by the pressure calculated from the gas disk's motion. When this situation occurs, the gas disk collapses under its own weight, forming complex structures and losing its ability to maintain stable motion at the galactic center. Consequently, the gas rapidly falls towards the central black hole, A phenomenon known as "gravitational instability" at the heart of the galaxy.

Furthermore, the study advanced quantitative understanding of gas flows around the active galactic nucleus. By considering the density of the observed gas and the velocity of the accretion flow, the researchers were able to calculate the rate at which gas is supplied to the black hole. Surprisingly, this rate was found to be 30 times greater than what is needed to sustain the active galactic nucleus. In other words, the majority of the accretion flow at the 1-light-year scale around the galactic center was not contributing to the growth of the black hole.

So, where did this surplus gas go? High-sensitivity observations of all phase gases with ALMA detected outflows from the active galactic nucleus. Quantitative analysis revealed that the majority of the gas flowing towards the black hole was expelled as atomic or molecular outflows. However, due to their slow velocities, they couldn't escape the gravitational pull of the black hole and eventually returned to the gas disk. There, they were recycled into an accretion flow toward the black hole, completing a fascinating gas recycling process at the galactic center.

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Astrophysicists scan the Galaxy for signs of life

Astrophysicists from Trinity College Dublin are scanning the Universe for "technosignatures" emanating from distant planets that would provide support for the existence of intelligent, alien life.

Using the Irish LOFAR telescope and its counterpart in Onsala, Sweden, the team -- led by Professor Evan Keane, Associate Professor of Radio Astronomy in Trinity's School of Physics, and Head of the Irish LOFAR Telescope -- plans to monitor millions of star systems.

Scientists have been searching for extraterrestrial radio signals for well over 60 years. Many of these have been carried out using single observatories which limits the ability to identify signals from the haze of terrestrial interference on Earth. Much of the effort has focused on frequencies above 1 GHz because the single-dish telescopes employed operate at these frequencies.

Now, a new collaboration led by Trinity College Dublin, with the Breakthrough Listen team and Onsala Space Observatory in Sweden, is perfecting a multi-site, multi-telescope technique that allows them to search at much lower frequencies of 110 -- 190 MHz.

The Breakthrough Listen programme is the most comprehensive search for technologically advanced extraterrestrial life, developing dedicated instruments at the Irish and Swedish LOFAR stations. Using multiple sites has the major benefit that it is much less likely to provide a "false positive" signal; such signals arise due to interference from many human sources on Earth.

The team has just published details of their method and their ongoing search in the Astronomical Journal They have already scanned 1.6 million star systems flagged as interesting targets by the Gaia and TESS space missions, run by ESA and NASA respectively. So far these searches have drawn a blank.

But the search has only just begun...

Prof. Keane said: "In the last 50 years evidence has steadily mounted that the constituents and conditions necessary for life are relatively common in the Universe, which begs one of life's greatest unanswered questions: are we really alone?

"To some people the 'Search for Extra-terrestrial Intelligence, or SETI' might seem like something from a movie, but it has been a scientific pursuit for decades, and for a host of very good reasons. With this project we are basing our search on the common assumption that civilisations elsewhere in the Universe may employ similar technologies to those developed on Earth. As a result radio frequencies are a logical domain for conducting SETI surveys due to the widespread use of telecommunications and radar and our access to next-gen radio telescopes offers a great chance for a deep dive into the Universe."

Owen Johnson, PhD Candidate in Trinity's School of Physics, is the first author of the journal article, and the first Irish person to ever undertake a PhD on the topic of SETI. He added:

"What makes surveys like this one truly captivating is the fact that we're pushing these telescopes to their absolute limits, directing them towards substantial portions of the sky. As a result, we have the exciting possibility of discovering all sorts of wild and wondrous phenomena during this process and if we're very fortunate, even encountering our cosmic neighbours.

"LOFAR is soon to undergo a staged series of upgrades across all stations in the array across Europe, which will allow an even broader SETI at ranges of 15 -- 240 MHz. We have billions of star systems to explore and will be relying on some machine learning techniques to sift through the immense volume of data.

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Finding explanation for Milky Way's warp

The Milky Way is often depicted as a flat, spinning disk of dust, gas, and stars. But if you could zoom out and take an edge-on photo, it actually has a distinctive warp -- as if you tried to twist and bend a vinyl LP.

Though scientists have long known through observational data that the Milky Way is warped and its edges are flared like a skirt, no one could explain why.

Now, Harvard astronomers at the Center for Astrophysics | Harvard and Smithsonian (CfA) have performed the first calculations that fully explain this phenomenon, with compelling evidence pointing to the Milky Way's envelopment in an off-kilter halo of dark matter. The work also bolsters current thinking about how the galaxy evolved and may offer clues into some of the mysteries of dark matter.

The new calculations were led by Jiwon Jesse Han, a Griffin Graduate School of Arts and Sciences student affiliated with the CfA. Published in Nature Astronomy, the work includes co-authors Charlie Conroy and Lars Hernquist, both faculty members at the CfA and in the Department of Astronomy.

Our galaxy is located inside a diffuse cloud called the stellar halo, which extends much farther out into the universe. In groundbreaking work published last year, the Harvard team deduced that the stellar halo is tilted and elliptical in shape, like a zeppelin or football.

Building on that, the team assumed the same shape for the dark matter halo, the larger entity that encompasses everything in and around the Milky Way. Dark matter makes up 80 percent of the galaxy's mass but is invisible because it doesn't interact with light, so the shape of that halo must be inferred. Using models to calculate the orbits of stars within a tilted, oblong dark matter halo, the team found a near-perfect match to existing observations of a warped, flared galaxy.

"A tilted dark halo is actually fairly common in simulations, but no one had explored its effect on the Milky Way," Conroy said. "It turns out that the tilt is an elegant way to explain both the magnitude and direction of our galaxy's wobbly disk."

Scientists had long surmised that the Milky Way formed due to a galactic collision; the astronomers' work further underscores that hypothesis.

"If the galaxy was just evolving on its own, it would have had this nice, spherical halo, this nice, flat disk," Han said. "So the fact that the halo is tilted and has a football-like shape suggests that our galaxy experienced a merger event, where two galaxies collide."

Their calculation of the dark matter halo's probable shape may also provide clues as to the properties and particle nature of dark matter itself, which remain unsolved mysteries in physics. "The fact that the galaxy is not spherical in our data implies that there is some limit to which dark matter can interact with itself," Han explained.

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Plot thickens in hunt for ninth planet

A pair of theoretical physicists are reporting that the same observations inspiring the hunt for a ninth planet might instead be evidence within the solar system of a modified law of gravity originally developed to understand the rotation of galaxies.

Researchers Harsh Mathur, a professor of physics at Case Western Reserve University, and Katherine Brown, an associate professor of physics at Hamilton College, made the assertion after studying the effect the Milky Way galaxy would have on objects in the outer solar system -- if the laws of gravity were governed by a theory known as Modified Newtonian Dynamics (or MOND).

MOND proposes Isaac Newton's famous law of gravity is valid up to a point. That is, when the gravitational acceleration predicted by Newton's law becomes small enough, MOND allows for a different gravitational behavior to take over.

The observational success of MOND on galactic scales is why some scientists consider it an alternative to "dark matter," the term physicists use to describe a hypothesized form of matter that would have gravitational effects but not emit any light.

"MOND is really good at explaining galactic-scale observations," Mathur said, "but I hadn't expected that it would have noticeable effects on the outer solar system."

Their work was recently published in The Astronomical Journal.

A 'striking' alignment

Mathur and Brown had studied MOND's effect on galactic dynamics before. But they became interested in MOND's more local effects after astronomers announced in 2016 that a handful of objects in the outer solar system showed orbital anomalies that could be explained by a ninth planet.

Orbital peculiarities have led to historic discoveries before: Neptune was discovered through its gravitational tug on the orbits of nearby object, the minute precession of Mercury provided early evidence in support of Einstein's theory of general relativity, and astronomers have recently used orbital dynamics to infer the presence of a supermassive black hole at the center of our Galaxy.

Brown realized MOND's predictions might be at odds with the observations that had motivated the search for a ninth planet. "We wanted to see if the data that support the Planet Nine hypothesis would effectively rule out MOND," she said.

Instead, Mathur and Brown found MOND predicts precisely clustering that astronomers have observed. Over millions of years, they argue, the orbits of some objects in the outer solar system would be dragged into alignment with the galaxy's own gravitational field.

When they plotted the orbits of the objects from the Planet Nine dataset against the galaxy's own gravitational field, "the alignment was striking," Mathur said.

The authors caution that the current dataset is small and that that any number of other possibilities might prove to be correct; other astronomers have argued the orbital peculiarities are the result of observational bias, for example.

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Furthest ever detection of a galaxy's magnetic field

Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have detected the magnetic field of a galaxy so far away that its light has taken more than 11 billion years to reach us: we see it as it was when the Universe was just 2.5 billion years old. The result provides astronomers with vital clues about how the magnetic fields of galaxies like our own Milky Way came to be.

Lots of astronomical bodies in the Universe have magnetic fields, whether it be planets, stars or galaxies. "Many people might not be aware that our entire galaxy and other galaxies are laced with magnetic fields, spanning tens of thousands of light-years," says James Geach, a professor of astrophysics at the University of Hertfordshire, UK, and lead author of the study published today in Nature.

"We actually know very little about how these fields form, despite their being quite fundamental to how galaxies evolve," adds Enrique Lopez Rodriguez, a researcher at Stanford University, USA, who also participated in the study. It is not clear how early in the lifetime of the Universe, and how quickly, magnetic fields in galaxies form because so far astronomers have only mapped magnetic fields in galaxies close to us.

Now, using ALMA, in which the European Southern Observatory (ESO) is a partner, Geach and his team have discovered a fully formed magnetic field in a distant galaxy, similar in structure to what is observed in nearby galaxies. The field is about 1000 times weaker than the Earth's magnetic field, but extends over more than 16,000 light-years.

"This discovery gives us new clues as to how galactic-scale magnetic fields are formed," explains Geach. Observing a fully developed magnetic field this early in the history of the Universe indicates that magnetic fields spanning entire galaxies can form rapidly while young galaxies are still growing.

The team believes that intense star formation in the early Universe could have played a role in accelerating the development of the fields. Moreover, these fields can in turn influence how later generations of stars will form. Co-author and ESO astronomer Rob Ivison says that the discovery opens up "a new window onto the inner workings of galaxies, because the magnetic fields are linked to the material that is forming new stars."

To make this detection, the team searched for light emitted by dust grains in a distant galaxy, 9io9. Galaxies are packed full of dust grains and when a magnetic field is present, the grains tend to align and the light they emit becomes polarised. This means that the light waves oscillate along a preferred direction rather than randomly. When ALMA detected and mapped a polarised signal coming from 9io9, the presence of a magnetic field in a very distant galaxy was confirmed for the first time.

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DESI early data release holds nearly two million objects

The universe is big, and it's getting bigger. To study dark energy, the mysterious force behind the accelerating expansion of our universe, scientists are using the Dark Energy Spectroscopic Instrument (DESI) to map more than 40 million galaxies, quasars, and stars. Today, the collaboration publicly released its first batch of data, with nearly 2 million objects for researchers to explore.

The 80-terabyte data set comes from 2,480 exposures taken over six months during the experiment's "survey validation" phase in 2020 and 2021. In this period between turning the instrument on and beginning the official science run, researchers made sure their plan for using the telescope would meet their science goals -- for example, by checking how long it took to observe galaxies of different brightness, and by validating the selection of stars and galaxies to observe.

"The fact that DESI works so well, and that the amount of science-grade data it took during survey validation is comparable to previous completed sky surveys, is a monumental achievement," said Nathalie Palanque-Delabrouille, co-spokesperson for DESI and a scientist at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), which manages the experiment. "This milestone shows that DESI is a unique spectroscopic factory whose data will not only allow the study of dark energy but will also be coveted by the whole scientific community to address other topics, such as dark matter, gravitational lensing, and galactic morphology."

Today the collaboration also published a set of papers related to the early data release, which include early measurements of galaxy clustering, studies of rare objects, and descriptions of the instrument and survey operations. The new papers build on DESI's first measurement of the cosmological distance scale that was published in April, which used the first two months of routine survey data (not included in the early data release) and also showed DESI's ability to accomplish its design goals.

DESI uses 5,000 robotic positioners to move optical fibers that capture light from objects millions or billions of light-years away. It is the most powerful multi-object survey spectrograph in the world, able to measure light from more than 100,000 galaxies in one night. That light tells researchers how far away an object is, building a 3D cosmic map.

"Survey validation was very important for DESI because it allowed us -- before starting the main survey -- to adjust our selection of all the objects, including stars, bright galaxies, luminous red galaxies, emission line galaxies, and quasars," said Christophe Yeche, a scientist with the French Alternative Energies and Atomic Energy Commission (CEA) who co-leads the target selection group. "We've been able to optimize our selection and confirm our observation strategy."

As the universe expands, it stretches light's wavelength, making it redder -- a characteristic known as redshift. The further away the galaxy, the bigger the redshift. DESI specializes in collecting redshifts that can then be used to solve some of astrophysics' biggest puzzles: what dark energy is and how it has changed throughout the universe's history.

While DESI's primary goal is understanding dark energy, much of the data can also be used in other astronomical studies. For example, the early data release contains detailed images from some well-known areas of the sky, such as the Hubble Deep Field.

"There are some well-trodden spots where we've drilled down into the sky," said Stephen Bailey, a scientist at Berkeley Lab who leads data management for DESI. "We've taken valuable spectroscopic images in areas that are of interest to the rest of the community, and we're hoping that other people will take this data and do additional science with it."

Two interesting finds have already surfaced: Evidence of a mass migration of stars into the Andromeda galaxy, and incredibly distant quasars, the extremely bright and active supermassive black holes sometimes found at the center of galaxies.

"We observed some areas at very high depth. People have looked at that data and discovered very high redshift quasars, which are still so rare that basically any discovery of them is useful," said Anthony Kremin, a postdoctoral researcher at Berkeley Lab who led the data processing for the early data release. "Those high-redshift quasars are usually found with very large telescopes, so the fact that DESI -- a smaller, 4-meter survey instrument -- could compete with those larger, dedicated observatories was an achievement we are pretty proud of and demonstrates the exceptional throughput of the instrument."

Survey validation was also a chance to test the process of transforming raw data from DESI's ten spectrometers (which split a galaxy's light into different colors) into useful information.

"If you looked at them, the images coming directly from the camera would look like nonsense -- like lines on a weird, fuzzy image," said Laurie Stephey, a data architect at the National Energy Research Scientific Computing Center (NERSC), the supercomputer that processes DESI's data. "The magic happens in the processing and the software being able to decode the data. It's exciting that we have the technology to make that data accessible to the research community and that we can support this big question of 'what is dark energy?'"

DESI's early data was a unique project for NERSC. All of the experiment's code, including the computational heavy lifting, is written in the programming language Python rather than the traditional C++ or Fortran.

"That was the first time that using pure Python was shown to be a feasible approach for a major experiment at NERSC, and since then, Python has become increasingly common in our user workload," Stephey said.

The DESI early data release is now available to access for free through NERSC.

There is plenty of data yet to come from the experiment. DESI is currently two years into its five-year run and ahead of schedule on its quest to collect more than 40 million redshifts. The survey has already catalogued more than 26 million astronomical objects in its science run, and is adding more than a million per month.

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Mysterious dashes revealed in Milky Way's center

An international team of astrophysicists has discovered something wholly new, hidden in the center of the Milky Way galaxy.

In the early 1980s, Northwestern University's Farhad Yusef-Zadeh discovered gigantic, one-dimensional filaments dangling vertically near Sagittarius A*, our galaxy's central supermassive black hole. Now, Yusef-Zadeh and his collaborators have discovered a new population of filaments -- but these threads are much shorter and lie horizontally or radially, spreading out like spokes on a wheel from the black hole.

Although the two populations of filaments share several similarities, Yusef-Zadeh assumes they have different origins. While the vertical filaments sweep through the galaxy, towering up to 150 light-years high, the horizontal filaments look more like the dots and dashes of Morse code, punctuating only one side of Sagittarius A*.

The study will be published on Friday (June 2) in The Astrophysical Journal Letters.

"It was a surprise to suddenly find a new population of structures that seem to be pointing in the direction of the black hole," Yusef-Zadeh said. "I was actually stunned when I saw these. We had to do a lot of work to establish that we weren't fooling ourselves. And we found that these filaments are not random but appear to be tied to the outflow of our black hole. By studying them, we could learn more about the black hole's spin and accretion disk orientation. It is satisfying when one finds order in a middle of a chaotic field of the nucleus of our galaxy."

An expert in radio astronomy, Yusef-Zadeh is a professor of physics and astronomy at Northwestern's Weinberg College of Arts and Sciences and member of CIERA.

Decades in the making

The new discovery may come as a surprise, but Yusef-Zadeh is no stranger to uncovering mysteries at the center of our galaxy, located 25,000 light-years from Earth. The latest study builds on four decades of his research. After first discovering the vertical filaments in 1984 with Mark Morris and Don Chance, Yusef-Zadeh along with Ian Heywood and their collaborators later uncovered two gigantic radio-emitting bubbles near Sagittarius A*. Then, in a series of publications in 2022, Yusef-Zadeh (in collaborations with Heywood, Richard Arent and Mark Wardle) revealed nearly 1,000 vertical filaments, which appeared in pairs and clusters, often stacked equally spaced or side by side like strings on a harp.

Yusef-Zadeh credits the flood of new discoveries to enhanced radio astronomy technology, particularly the South African Radio Astronomy Observatory's (SARAO) MeerKAT telescope. To pinpoint the filaments, Yusef-Zadeh's team used a technique to remove the background and smooth the noise from MeerKAT images in order to isolate the filaments from surrounding structures.

"The new MeerKAT observations have been a game changer," he said. "The advancement of technology and dedicated observing time have given us new information. It's really a technical achievement from radio astronomers."

Horizontal vs. vertical

After studying the vertical filaments for decades, Yusef-Zadeh was shocked to uncover their horizontal counterparts, which he estimates are about 6 million years old. "We have always been thinking about vertical filaments and their origin," he said. "I'm used to them being vertical. I never considered there might be others along the plane."

While both populations comprise one-dimensional filaments that can be viewed with radio waves and appear to be tied to activities in the galactic center, the similarities end there.

The vertical filaments are perpendicular to the galactic plane; the horizontal filaments are parallel to the plane but point radially toward the center of the galaxy where the black hole lies. The vertical filaments are magnetic and relativistic; the horizontal filaments appear to emit thermal radiation. The vertical filaments encompass particles moving at speeds near the speed of light; the horizontal filaments appear to accelerate thermal material in a molecular cloud. There are several hundred vertical filaments and just a few hundred horizontal filaments. And the vertical filaments, which measure up to 150 light-years high, far surpass the size of the horizontal filaments, which measure just 5 to 10 light-years in length. The vertical filaments also adorn space around the nucleus of the galaxy; the horizontal filaments appear to spread out to only one side, pointing toward the black hole.

"One of the most important implications of radial outflow that we have detected is the orientation of the accretion disk and the jet-driven outflow from Sagittarius A* along the galactic plane," Yusef-Zadeh said.

'Our work is never complete'

The new discovery is filled with unknowns, and Yusef-Zadeh's work to unravel its mysteries has just begun. For now, he can only consider a plausible explanation about the new population's mechanisms and origins.

"We think they must have originated with some kind of outflow from an activity that happened a few million years ago," Yusef-Zadeh said. "It seems to be the result of an interaction of that outflowing material with objects near it. Our work is never complete. We always need to make new observations and continually challenge our ideas and tighten up our analysis."

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Galactic bubbles are more complex than imagined

Astronomers have revealed new evidence about the properties of the giant bubbles of high-energy gas that extend far above and below the Milky Way galaxy's center.

In a study recently published inNature Astronomy, a team led by scientists at The Ohio State University was able to show that the shells of these structures -- dubbed "eRosita bubbles" after being found by the eRosita X-ray telescope -are more complex than previously thought.

Although they bear a striking similarity in shape to Fermi bubbles, eRosita bubbles are larger and more energetic than their counterparts. Known together as the "galactic bubbles" due to their size and location, they provide an exciting opportunity to study star formation history as well as reveal new clues about how the Milky Way came to be, said Anjali Gupta, lead author of the study and a former postdoctoral researcher at Ohio State who is now a professor of astronomy at Columbus State Community College.

These bubbles exist in the gas that surrounds galaxies, an area which is called the circumgalactic medium.

"Our goal was really to learn more about the circumgalactic medium, a place very important in understanding how our galaxy formed and evolved," Gupta said. "A lot of the regions that we were studying happened to be in the region of the bubbles, so we wanted to see how different the bubbles are when compared to the regions which are away from the bubble."

Previous studies had assumed that these bubbles were heated by the shock of gas as it blows outward from the galaxy, but this paper's main findings suggest the temperature of the gas within the bubbles isn't significantly different from the area outside of it.

"We were surprised to find that the temperature of the bubble region and out of the bubble region were the same," said Gupta. Additionally, the study demonstrates that these bubbles are so bright because they're filled with extremely dense gas, not because they are at hotter temperatures than the surrounding environment.

Gupta and Smita Mathur, co-author of the study and a professor of astronomy at Ohio State, did their analysis using observations made by the Suzaku satellite, a collaborative mission between NASA and the Japanese Aerospace Exploration Agency.

By analyzing 230 archival observations made between 2005 and 2014, researchers were able to characterize the diffuse emission -- the electromagnetic radiation from very low density gas -- of the galactic bubbles, as well as the other hot gases that surround them.

Although the origin of these bubbles has been debated in scientific literature, this study is the first that begins to settle it, said Mathur. As the team found an abundance of non-solar neon-oxygen and magnesium-oxygen ratios in the shells, their results strongly suggest that galactic bubbles were originally formed by nuclear star-forming activity, or the injection of energy by massive stars and other kinds of astrophysical phenomena, rather than through the activities of a supermassive black hole.

"Our data supports the theory that these bubbles are most likely formed due to intense star formation activity at the galactic center, as opposed to black hole activity occurring at the galactic center," Mathur said. To further investigate the implications their discovery may have for other aspects of astronomy, the team hopes to use new data from other upcoming space missions to continue characterizing the properties of these bubbles, as well as work on novel ways to analyze the data they already have.

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