̽��ֱ�� of Cambridge - star

Farewell, Gaia: spacecraft operations come to an end

sc604 — Thu, 27 Mar 2025 10:27:38 +0000

On 27 March 2025, Gaia’s control team at ESA’s European Space Operations Centre switched off the spacecraft’s subsystems and sent it into a ‘retirement orbit’ around the Sun.

Though the spacecraft’s operations are now over, the scientific exploitation of Gaia’s data has just begun.

Launched in 2013, Gaia has transformed our understanding of the cosmos by mapping the positions, distances, motions, and properties of nearly two billion stars and other celestial objects. It has provided the largest, most precise multi-dimensional map of our galaxy ever created, revealing its structure and evolution in unprecedented detail.

̽��ֱ��mission uncovered evidence of past galactic mergers, identified new star clusters, contributed to the discovery of exoplanets and black holes, mapped millions of quasars and galaxies, and tracked hundreds of thousands of asteroids and comets. ̽��ֱ��mission has also enabled the creation of the best visualisation of how our galaxy might look to an outside observer.

“ ̽��ֱ��data from the Gaia satellite has and is transforming our understanding of the Milky Way, how it formed, how it has evolved and how it will evolve,” said Dr Nicholas Walton from Cambridge’s Institute of Astronomy, lead of the Gaia UK project team. “Gaia has been in continuous operation for over 10 years, faultless, without interruption, reflecting the quality of the engineering, with significant elements of Gaia designed and built in the UK. But now it is time for its retirement. Gaia has finished its observations of the night sky. But the analysis of the Gaia mission data continues. Later in 2026 sees the next Gaia Data Release 4, to further underpin new discovery unravelling the beauty and mystery of the cosmos.”

Gaia far exceeded its planned lifetime of five years, and its fuel reserves are dwindling. ̽��ֱ��Gaia team considered how best to dispose of the spacecraft in line with ESA’s efforts to responsibly dispose of its missions.

They wanted to find a way to prevent Gaia from drifting back towards its former home near the scientifically valuable second Lagrange point (L2) of the Sun-Earth system and minimise any potential interference with other missions in the region.

“Switching off a spacecraft at the end of its mission sounds like a simple enough job,” said Gaia Spacecraft Operator Tiago Nogueira. “But spacecraft really don’t want to be switched off.

“We had to design a decommissioning strategy that involved systematically picking apart and disabling the layers of redundancy that have safeguarded Gaia for so long, because we don’t want it to reactivate in the future and begin transmitting again if its solar panels find sunlight.”

On 27 March, the Gaia control team ran through this series of passivation activities. One final use of Gaia’s thrusters moved the spacecraft away from L2 and into a stable retirement orbit around the Sun that will minimise the chance that it comes within 10 million kilometres of Earth for at least the next century.

̽��ֱ��team then deactivated and switched off the spacecraft’s instruments and subsystems one by one, before deliberately corrupting its onboard software. ̽��ֱ��communication subsystem and the central computer were the last to be deactivated.

Gaia’s final transmission to ESOC mission control marked the conclusion of an intentional and carefully orchestrated farewell to a spacecraft that has tirelessly mapped the sky for over a decade.

Though Gaia itself has now gone silent, its contributions to astronomy will continue to shape research for decades. Its vast and expanding data archive remains a treasure trove for scientists, refining knowledge of galactic archaeology, stellar evolution, exoplanets and much more.

“No other mission has had such an impact over such a broad range of astrophysics. It continues to be the source of over 2,000 peer-reviewed papers per year, more than any other space mission,” said Gaia UK team member Dr Dafydd Wyn Evans, also from the Institute of Astronomy. “It is sad that its observing days are over, but work is continuing in Cambridge, and across Europe, to process and calibrate the final data so that Gaia will still be making its impact felt for many years in the future.”

A workhorse of galactic exploration, Gaia has charted the maps that future explorers will rely on to make new discoveries. ̽��ֱ��star trackers on ESA’s Euclid spacecraft use Gaia data to precisely orient the spacecraft. ESA’s upcoming Plato mission will explore exoplanets around stars characterised by Gaia and may follow up on new exoplanetary systems discovered by Gaia.

̽��ֱ��Gaia control team also used the spacecraft’s final weeks to run through a series of technology tests. ̽��ֱ��team tested Gaia’s micro propulsion system under different challenging conditions to examine how it had aged over more than ten years in the harsh environment of space. ̽��ֱ��results may benefit the development of future ESA missions relying on similar propulsion systems, such as the LISA mission.

̽��ֱ��Gaia spacecraft holds a deep emotional significance for those who worked on it. As part of its decommissioning, the names of around 1500 team members who contributed to its mission were used to overwrite some of the back-up software stored in Gaia’s onboard memory.

Personal farewell messages were also written into the spacecraft’s memory, ensuring that Gaia will forever carry a piece of its team with it as it drifts through space.

As Gaia Mission Manager Uwe Lammers put it: “We will never forget Gaia, and Gaia will never forget us.”

̽��ֱ��Cambridge Gaia DPAC team is responsible for the analysis and generation of the Gaia photometric and spectro-photometric data products, and it also generated the Gaia photometric science alert stream for the duration of the satellite's in-flight operations.

Adapted from a media release by the European Space Agency.

̽��ֱ��European Space Agency’s Gaia spacecraft has been powered down, after more than a decade spent gathering data that are now being used to unravel the secrets of our home galaxy.

ESA/Gaia/DPAC, Stefan Payne-Wardenaar

Artist's impression of the Milky Way

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Last starlight for ground-breaking Gaia

Anonymous — Wed, 15 Jan 2025 09:22:32 +0000

Launched on 19 December 2013, Gaia’s fuel tank is now approaching empty – it uses about a dozen grams of cold gas per day to keep it spinning with pinpoint precision. But this is far from the end of the mission. Technology tests are scheduled for the weeks ahead before Gaia is moved to its ‘retirement’ orbit, and two massive data releases are tabled for around 2026 and the end of this decade, respectively.

“Today marks the end of science observations and we are celebrating this incredible mission that has exceeded all our expectations, lasting for almost twice its originally foreseen lifetime,” said ESA Director of Science Carole Mundell.

“ ̽��ֱ��treasure trove of data collected by Gaia has given us unique insights into the origin and evolution of our Milky Way galaxy, and has also transformed astrophysics and Solar System science in ways that we are yet to fully appreciate. Gaia built on unique European excellence in astrometry and will leave a long-lasting legacy for future generations.”

“Today marks the last day of science data collection from Gaia, these observations to form part of the final data release,” said Dr Nicholas Walton from Cambridge’s Institute of Astronomy, lead of the UK Gaia Project team and ESA Gaia Science Team member. “Our Gaia team in the UK is now working hard on the incredibly complex data analysis for the upcoming Gaia data releases. These will enable a wealth of new discovery, adding to the science from one of the world’s most productive science discovery machines.”

Gaia delivers best Milky Way map

Gaia has been charting the positions, distances, movements, brightness changes, composition and numerous other characteristics of stars by monitoring them with its three instruments many times throughout the mission.

This has enabled Gaia to deliver on its primary goal of building the largest, most precise map of the Milky Way, showing us our home galaxy like no other mission has done before.

Gaia’s repeated measurements of stellar distances, motions and characteristics are key to performing ‘galactic archeology’ on our Milky Way, revealing missing links in our galaxy’s complex history to help us learn more about our origins. From detecting ‘ghosts’ of other galaxies and multiple streams of ancient stars that merged with the Milky Way in its early history, to finding evidence for an ongoing collision with the Sagittarius dwarf galaxy today, Gaia is rewriting the Milky Way’s history and making predictions about its future.

Warning! More ground-breaking science ahead

̽��ֱ��Gaia scientific and engineering teams are already working on the preparations for Gaia Data Release 4 (DR4), expected in 2026.

“This is the Gaia release the community has been waiting for, and it’s exciting to think this only covers half of the collected data,” said Antonella Vallenari, Deputy Chair of DPAC based at the Istituto Nazionale di Astrofisica (INAF), Astronomical Observatory of Padua, Italy. “Even though the mission has now stopped collecting data, it will be business as usual for us for many years to come as we make these incredible datasets ready for use.”

“Over the next months we will continue to downlink every last drop of data from Gaia, and at the same time the processing teams will ramp up their preparations for the fifth and final major data release at the end of this decade, covering the full 10.5 years of mission data,” said Rocio Guerra, Gaia Science Operations Team Leader based at ESA’s European Space Astronomy Centre (ESAC) near Madrid in Spain.

Gaia’s retirement plan

While today marks the end of science observations, a short period of technology testing now begins. ̽��ֱ��tests have the potential to further improve the Gaia calibrations, learn more about the behaviour of certain technology after ten years in space, and even aid the design of future space missions.

After several weeks of testing, Gaia will leave its current orbit around Lagrange point 2, 1.5 million km from the Earth in the direction away from the Sun, to be put into its final heliocentric orbit, far away from Earth’s sphere of influence. ̽��ֱ��spacecraft will be passivated on 27 March 2025, to avoid any harm or interference with other spacecraft.

Wave farewell to Gaia

During the technology tests Gaia’s orientation will be changed, meaning it will temporarily become several magnitudes brighter, making observations through small telescopes a lot easier (it won’t be visible to the naked eye). A guide to locating Gaia has been set up here, and amateur astronomers are invited to share their observations.

“Gaia will treat us with this final gift as we bid farewell, shining among the stars ahead of its well-earned retirement,” said Uwe Lammers, Gaia Mission Manager.

“It’s a moment to celebrate this transformative mission and thank all of the teams for more than a decade of hard work operating Gaia, planning its observations, and ensuring its precious data are returned smoothly to Earth.”

Adapted from a European Space Agency press release.

̽��ֱ��European Space Agency’s Milky Way-mapper Gaia has completed the sky-scanning phase of its mission, racking up more than three trillion observations of about two billion stars and other objects over the last decade to revolutionise the view of our home galaxy and cosmic neighbourhood.

ESA/Gaia/DPAC, Stefan Payne-Wardenaar

This is a new artist’s impression of our galaxy, the Milky Way, based on data from ESA’s Gaia space telescope.

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‘Inside-out’ galaxy growth observed in the early universe

sc604 — Fri, 11 Oct 2024 09:00:00 +0000

This galaxy is one hundred times smaller than the Milky Way, but is surprisingly mature for so early in the universe. Like a large city, this galaxy has a dense collection of stars at its core but becomes less dense in the galactic ‘suburbs’. And like a large city, this galaxy is starting to sprawl, with star formation accelerating in the outskirts.

This is the earliest-ever detection of inside-out galactic growth. Until Webb, it had not been possible to study galaxy growth so early in the universe’s history. Although the images obtained with Webb represent a snapshot in time, the researchers, led by the ̽��ֱ�� of Cambridge, say that studying similar galaxies could help us understand how they transform from clouds of gas into the complex structures we observe today. ̽��ֱ��results are reported in the journal Nature Astronomy.

“ ̽��ֱ��question of how galaxies evolve over cosmic time is an important one in astrophysics,” said co-lead author Dr Sandro Tacchella from Cambridge’s Cavendish Laboratory. “We’ve had lots of excellent data for the last ten million years and for galaxies in our corner of the universe, but now with Webb, we can get observational data from billions of years back in time, probing the first billion years of cosmic history, which opens up all kinds of new questions.”

̽��ֱ��galaxies we observe today grow via two main mechanisms: either they pull in, or accrete, gas to form new stars, or they grow by merging with smaller galaxies. Whether different mechanisms were at work in the early universe is an open question which astronomers are hoping to address with Webb.

“You expect galaxies to start small as gas clouds collapse under their own gravity, forming very dense cores of stars and possibly black holes,” said Tacchella. “As the galaxy grows and star formation increases, it’s sort of like a spinning figure skater: as the skater pulls in their arms, they gather momentum, and they spin faster and faster. Galaxies are somewhat similar, with gas accreting later from larger and larger distances spinning the galaxy up, which is why they often form spiral or disc shapes.”

This galaxy, observed as part of the JADES (JWST Advanced Extragalactic Survey) collaboration, is actively forming stars in the early universe. It has a highly dense core, which despite its relatively young age, is of a similar density to present-day massive elliptical galaxies, which have 1000 times more stars. Most of the star formation is happening further away from the core, with a star-forming ‘clump’ even further out.

̽��ֱ��star formation activity is strongly rising toward the outskirts, as the star formation spreads out and the galaxy grows. This type of growth had been predicted with theoretical models, but with Webb, it is now possible to observe it.

“One of the many reasons that Webb is so transformational to us as astronomers is that we’re now able to observe what had previously been predicted through modelling,” said co-author William Baker, a PhD student at the Cavendish. “It’s like being able to check your homework.”

Using Webb, the researchers extracted information from the light emitted by the galaxy at different wavelengths, which they then used to estimate the number of younger stars versus older stars, which is converted into an estimate of the stellar mass and star formation rate.

Because the galaxy is so compact, the individual images of the galaxy were ‘forward modelled’ to take into account instrumental effects. Using stellar population modelling that includes prescriptions for gas emission and dust absorption, the researchers found older stars in the core, while the surrounding disc component is undergoing very active star formation. This galaxy doubles its stellar mass in the outskirts roughly every 10 million years, which is very rapid: the Milky Way galaxy doubles its mass only every 10 billion years.

̽��ֱ��density of the galactic core, as well as the high star formation rate, suggest that this young galaxy is rich with the gas it needs to form new stars, which may reflect different conditions in the early universe.

“Of course, this is only one galaxy, so we need to know what other galaxies at the time were doing,” said Tacchella. “Were all galaxies like this one? We’re now analysing similar data from other galaxies. By looking at different galaxies across cosmic time, we may be able to reconstruct the growth cycle and demonstrate how galaxies grow to their eventual size today.”

Reference:
William M. Baker, Sandro Tacchella, et al. ‘A core in a star-forming disc as evidence of inside-out growth in the early Universe.’ Nature Astronomy (2024). DOI: 10.1038/s41550-024-02384-8

Astronomers have used the NASA/ESA James Webb Space Telescope (JWST) to observe the ‘inside-out’ growth of a galaxy in the early universe, only 700 million years after the Big Bang.

NASA, ESA, CSA, Sandro Tacchella, William Baker, Ovee Tulaskar

Galaxy NGC 1549, seen today and possibly 13 billion years ago

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Astronomers uncover risks to planets that could host life

sc604 — Mon, 05 Aug 2024 14:10:39 +0000

̽��ֱ��discovery suggests that the intense UV radiation from these flares could significantly impact whether planets around red dwarf stars can be habitable.

“Few stars have been thought to generate enough UV radiation through flares to impact planet habitability. Our findings show that many more stars may have this capability,” said first author Vera Berger, who led the research while based at the ̽��ֱ�� of Hawai’i and who is now based at the ̽��ֱ�� of Cambridge.

Berger and her team used archival data from the GALEX space telescope to search for flares among 300,000 nearby stars. GALEX is a now-decommissioned NASA mission that simultaneously observed most of the sky at near-and far-UV wavelengths from 2003 to 2013. Using new computational techniques, the team mined insights from the data.

“Combining modern computer power with gigabytes of decades-old observations allowed us to search for flares on thousands and thousands of nearby stars,” said co-author Dr Michael Tucker from Ohio State ̽��ֱ��.

According to researchers, UV radiation from stellar flares can either erode planetary atmospheres, threatening their potential to support life, or contribute to the formation of RNA building blocks, which are essential for the creation of life.

̽��ֱ��study, published in the Monthly Notices of the Royal Astronomical Society, challenges existing models of stellar flares and exoplanet habitability, showing that far-UV emission from flares is on average three times more energetic than typically assumed, and can reach up to twelve times the expected energy levels.

“A change of three is the same as the difference in UV in the summer from Anchorage, Alaska to Honolulu, where unprotected skin can get a sunburn in less than 10 minutes,” said co-author Benjamin J. Shappee from the ̽��ֱ�� of Hawai’i.

̽��ֱ��exact cause of this stronger far-UV emission remains unclear. ̽��ֱ��team believes it might be that flare radiation is concentrated at specific wavelengths, indicating the presence of atoms like carbon and nitrogen.

“This study has changed the picture of the environments around stars less massive than our Sun, which emit very little UV light outside of flares,” said co-author Jason Hinkle.

According to Berger, now a Churchill Scholar at Cambridge, more data from space telescopes is needed to study the UV light from stars, which is crucial for understanding the source of this emission.

“Our work puts a spotlight on the need for further exploration into the effects of stellar flares on exoplanetary environments,” said Berger. “Using space telescopes to obtain UV spectra of stars will be crucial for better understanding the origins of this emission.”

Reference:
Vera L Berger et al. ‘Stellar flares are far-ultraviolet luminous.’ Monthly Notices of the Royal Astronomical Society (2024). DOI: 10.1093/mnras/stae1648

Adapted from a ̽��ֱ�� of Hawai’i media release.

Astronomers have discovered that red dwarf stars can produce stellar flares that carry far-ultraviolet (far-UV) radiation levels much higher than previously believed.

Scott Wiessinger/NASA

A red dwarf star unleashes a series of powerful flares.

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Earliest detection of metal challenges what we know about the first galaxies

sc604 — Thu, 06 Jun 2024 14:52:26 +0000

Using the James Webb Space Telescope (JWST), an international team of astronomers led by the ̽��ֱ�� of Cambridge observed a very young galaxy in the early universe and found that it contained surprising amounts of carbon, one of the seeds of life as we know it.

In astronomy, elements heavier than hydrogen or helium are classed as metals. ̽��ֱ��very early universe was almost entirely made up of hydrogen, the simplest of the elements, with small amounts of helium and tiny amounts of lithium.

Every other element that makes up the universe we observe today was formed inside a star. When stars explode as supernovas, the elements they produce are circulated throughout their host galaxy, seeding the next generation of stars. With every new generation of stars and ‘stardust’, more metals are formed, and after billions of years, the universe evolves to a point where it can support rocky planets like Earth and life like us.

̽��ֱ��ability to trace the origin and evolution of metals will help us understand how we went from a universe made almost entirely of just two chemical elements, to the incredible complexity we see today.

“ ̽��ֱ��very first stars are the holy grail of chemical evolution,” said lead author Dr Francesco D’Eugenio, from the Kavli Institute for Cosmology at Cambridge. “Since they are made only of primordial elements, they behave very differently to modern stars. By studying how and when the first metals formed inside stars, we can set a time frame for the earliest steps on the path that led to the formation of life.”

Carbon is a fundamental element in the evolution of the universe, since it can form into grains of dust that clump together, eventually forming into the first planetesimals and the earliest planets. Carbon is also key for the formation of life on Earth.

“Earlier research suggested that carbon started to form in large quantities relatively late – about one billion years after the Big Bang,” said co-author Professor Roberto Maiolino, also from the Kavli Institute. “But we’ve found that carbon formed much earlier – it might even be the oldest metal of all.”

̽��ֱ��team used the JWST to observe a very distant galaxy – one of the most distant galaxies yet observed – just 350 million years after the Big Bang, more than 13 billion years ago. This galaxy is compact and low mass – about 100,000 times less massive than the Milky Way.

“It’s just an embryo of a galaxy when we observe it, but it could evolve into something quite big, about the size of the Milky Way,” said D’Eugenio. “But for such a young galaxy, it’s fairly massive.”

̽��ֱ��researchers used Webb’s Near Infrared Spectrograph (NIRSpec) to break down the light coming from the young galaxy into a spectrum of colours. Different elements leave different chemical fingerprints in the galaxy’s spectrum, allowing the team to determine its chemical composition. Analysis of this spectrum showed a confident detection of carbon, and tentative detections of oxygen and neon, although further observations will be required to confirm the presence of these other elements.

“We were surprised to see carbon so early in the universe, since it was thought that the earliest stars produced much more oxygen than carbon,” said Maiolino. “We had thought that carbon was enriched much later, through entirely different processes, but the fact that it appears so early tells us that the very first stars may have operated very differently.”

According to some models, when the earliest stars exploded as supernovas, they may have released less energy than initially expected. In this case, carbon, which was in the stars’ outer shell and was less gravitationally bound than oxygen, could have escaped more easily and spread throughout the galaxy, while a large amount of oxygen fell back and collapsed into a black hole.

“These observations tell us that carbon can be enriched quickly in the early universe,” said D’Eugenio. “And because carbon is fundamental to life as we know it, it’s not necessarily true that life must have evolved much later in the universe. Perhaps life emerged much earlier – although if there’s life elsewhere in the universe, it might have evolved very differently than it did here on Earth.”

̽��ֱ��results have been accepted for publication in the journal Astronomy & Astrophysics and are based on data obtained within the JWST Advanced Deep Extragalactic Survey (JADES).

̽��ֱ��research was supported in part by the European Research Council, the Royal Society, and the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

Reference:
Francesco D’Eugenio et al. ‘JADES: Carbon enrichment 350 Myr after the Big Bang.’ Astronomy & Astrophysics (in press). DOI: 10.48550/arXiv.2311.09908

Astronomers have detected carbon in a galaxy just 350 million years after the Big Bang, the earliest detection of any element in the universe other than hydrogen.

NASA, ESA, CSA, STScI, Brant Robertson (UC Santa Cruz), Ben Johnson (CfA), Sandro Tacchella (Cambridge), Phill Cargile (CfA)

Deep field image from JWST

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Astronomers spot oldest ‘dead’ galaxy yet observed

sc604 — Wed, 06 Mar 2024 16:00:10 +0000

Using the James Webb Space Telescope, an international team of astronomers led by the ̽��ֱ�� 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.

̽��ֱ��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.

“ ̽��ֱ��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.

̽��ֱ��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.”

Reference:
Tobias J Looser et al. ‘A recently quenched galaxy 700 million years after the Big Bang.’ Nature (2024). DOI: 10.1038/s41586-024-07227-0

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

JADES Collaboration

False-colour JWST image of a small fraction of the GOODS South field, with JADES-GS-z7-01-QU highlighted

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Latest Gaia data release reveals rare lenses, cluster cores and unforeseen science

sc604 — Tue, 10 Oct 2023 12:47:51 +0000

Gaia is mapping our galaxy and beyond in multi-dimensional detail, completing the most accurate stellar census ever. ̽��ֱ��mission is painting a detailed picture of our place in the Universe, enabling us to better understand the diverse objects within it.

̽��ֱ��mission’s latest data release provides new and improved insights into the space around us. ̽��ֱ��release also brings findings that go far beyond what Gaia was initially designed to discover and digs deep into our cosmic history.

“This focused product data release will open up new insights across astronomy, from the precise orbits of asteroids in our Solar System, to quasar discovery in the distant cosmos,” said Dr Nicholas Walton from Cambridge’s Institute of Astronomy, lead of the UK Gaia Project team and ESA Gaia Science Team member. “It demonstrates the breadth of science enabled by Gaia, and the role of Cambridge and UK Gaia teams in the creation of these data products. This release represents but a small taste of the riches to be revealed with the publication of the next full release, Gaia DR4.”

So – what’s new from Gaia?

Half a million new stars: Gaia's observing mode extended to unlock cluster cores

Gaia’s third data release (DR3) contained data on over 1.8 billion stars, building a pretty complete view of the Milky Way and beyond. However, there remained gaps in our mapping. Gaia had not yet fully explored areas of sky that were especially densely packed with stars, leaving these comparatively unexplored – and overlooking stars shining less brightly than their many neighbours.

Globular clusters are a key example of this. These clusters are some of the oldest objects in the Universe, making them especially valuable to scientists looking at our cosmic past. Unfortunately, their bright cores, chock-full of stars, can overwhelm telescopes attempting to get a clear view. As such, they remain missing pieces in our maps of the Universe.

To patch the gaps in our maps, Gaia selected Omega Centauri, the largest globular cluster that can be seen from Earth. Rather than just focusing on individual stars, as it typically would, Gaia enabled a special mode to truly map a wider patch of sky surrounding the cluster’s core every time the cluster came into view.

“In Omega Centauri, we discovered over half a million new stars Gaia hadn't seen before – from just one cluster!” says lead author Katja Weingrill of the Leibniz-Institute for Astrophysics Potsdam (AIP), Germany, and a member of the Gaia collaboration.

“Through a new use of one of Gaia’s specialised engineering modes, we have been able to generate an imaging catalogue of some of the densest stellar fields in our galaxy,” said Dr Dafydd Wyn Evans, lead of the Gaia photometric development team. “This is enabling us to provide a more complete view of all components of the Milky Way, including the cores of Globular Clusters, some of the oldest structures in our Galaxy.”

This finding not only meets but actually exceeds Gaia’s planned potential. ̽��ֱ��team used an observing mode designed to ensure that all of Gaia’s instruments are running smoothly.

“ ̽��ֱ��Gaia Sky Mapper images required the development of a new processing pipeline to measure the accurate brightness of the hundreds of thousands faint stars not seen by Gaia before,” said Dr Francesca De Angeli, lead of Gaia’s Photometric Data Processing Centre in Cambridge. “This rich data probes regions of the sky previously unseen by Gaia, and fills in important gaps in earlier data releases.”

̽��ֱ��new stars revealed in Omega Centauri mark one of the most crowded regions explored by Gaia so far.

Gaia is currently exploring eight more regions in this way, with the results to be included in Gaia Data Release 4. These data will help astronomers to truly understand what is happening within these cosmic building blocks, a crucial step for scientists aiming to confirm the age of our galaxy, locate its centre, figure out whether it has gone through any past collisions, verify how stars change through their lifetimes, constrain our models of galactic evolution, and ultimately infer the possible age of the Universe itself.

Looking for lenses: Gaia the accidental cosmologist

While Gaia was not designed for cosmology, its new findings peer deep into the distant Universe, hunting for elusive and exciting objects that hold clues to some of humanity’s biggest questions about the cosmos: gravitational lenses.

Gravitational lensing occurs when the image of a faraway object becomes warped by a disturbing mass – a star or galaxy, for instance – sitting between us and the object. This intermediate mass acts as a giant magnifying glass, or lens, that can amplify the brightness of light and cast multiple images of the faraway source onto the sky. These rare configurations hold immense scientific value, revealing clues about the earliest days of the Universe.

̽��ֱ��team identified the candidates from an extensive list of possible quasars (including those from Gaia DR3). Five of the possible lenses are potential Einstein crosses, rare lensed systems with four different image components shaped like a cross. (See 12 such configurations discovered by Gaia in 2021.)

Finding lensed quasars is challenging. A lensed system’s constituent images can clump together on the sky in misleading ways, and most are very far away, making them faint and tricky to spot.

Extending Gaia’s value into cosmology brings synergy with ESA’s Euclid mission, recently launched on its quest to explore the dark Universe. While both focus on different parts of the cosmos – Euclid on mapping billions of galaxies, Gaia on mapping billions of stars – the lensed quasars discovered by Gaia can be used to guide future exploration with Euclid.

Asteroids, stacked starlight and pulsating stars

Other papers published today offer further insight into the space around us, and the diverse and sometimes mysterious objects within it.

One reveals more about 156,823 of the asteroids identified as part of Gaia DR3. ̽��ֱ��new dataset pinpoints the positions of these rocky bodies over nearly double the previous timespan, making most of their orbits – based on Gaia observations alone – 20 times more precise. In the future, Gaia DR4 will complete the set and include comets, planetary satellites and double the number of asteroids, improving our knowledge of the small bodies in nearby space.

Another paper maps the disc of the Milky Way by tracing weak signals seen in starlight, faint imprints of the gas and dust that floats between the stars. ̽��ֱ��Gaia team stacked six million spectra to study these signals, forming a dataset of weak features that have never been measured in such a large sample. ̽��ֱ��dataset will hopefully allow scientists to narrow down the source of these signals, which the team suspects to be a complex organic molecule. Knowing more about where this signal comes from helps us to study the physical and chemical processes active throughout our galaxy, and to understand more about the material lying between stars.

Finally, a paper characterises the dynamics of 10,000 pulsating and binary red giant stars in by far the largest such database available to date. These stars were part of a catalogue of two million variable star candidates released in Gaia DR3, and are key when calculating cosmic distances, confirming stellar characteristics, and clarifying how stars evolve throughout the cosmos. ̽��ֱ��new release provides a better understanding of how these stars change over time.

“This data release further demonstrates Gaia’s broad and fundamental value – even on topics it wasn’t initially designed to address,” said Timo Prusti, Project Scientist for Gaia at ESA.

̽��ֱ��next steps

Gaia’s previous Data Release, Gaia DR3, came on 13 June 2022. It was the most detailed survey of the Milky Way to date, and a treasure trove of data on strange ‘starquakes’, asymmetrically moving stars, stellar DNA and more. Gaia DR3 contained new and improved details for almost two billion stars in the Milky Way, and included the largest catalogues of binary stars, thousands of Solar System objects, and – more distantly and outside of our galaxy – millions of galaxies and quasars.

̽��ֱ��mission’s next Data Release, Gaia DR4, is expected not before the end of 2025. It will build upon both Gaia DR3 and this interim focused product release to further improve our understanding of the multi-dimensional Milky Way. It will refine our knowledge of stars’ colours, positions, and movements; resolve variable and multiple star systems; identify and characterise quasars and galaxies; list exoplanet candidates; and more.

Adapted from an ESA press release.

̽��ֱ��European Space Agency’s Gaia mission has released a goldmine of knowledge about our galaxy and beyond. Among other findings, the star surveyor has surpassed its planned potential to reveal half a million new and faint stars in a massive cluster, identified over 380 possible cosmic lenses, and pinpointed the positions of more than 150,000 asteroids within the Solar System.

This release represents but a small taste of the riches to be revealed with the publication of the next full release, Gaia DR4

Nicholas Walton

ESA/Gaia/DPAC

Gaia view of Omega Centauri

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Astronomers use ‘little hurricanes’ to weigh and date planets around young stars

sc604 — Fri, 06 Jan 2023 08:25:43 +0000

Researchers from the ̽��ֱ�� of Cambridge and the Institute for Advanced Study have developed a technique, which uses observations of these ‘hurricanes’ by the Atacama Large Millimeter/submillimetre Array (ALMA) to place some limits on the mass and age of planets in a young star system.

Pancake-like clouds of gases, dust and ice surrounding young stars – known as protoplanetary discs - are where the process of planet formation begins. Through a process known as core accretion, gravity causes particles in the disc to stick to each other, eventually forming larger solid bodies such as asteroids or planets. As young planets form, they start to carve gaps in the protoplanetary disc, like grooves on a vinyl record.

Even a relatively small planet – as small as one-tenth the mass of Jupiter according to some recent calculations – may be capable of creating such gaps. As these ‘super-Neptune’ planets can orbit their star at a distance greater than Pluto orbits the Sun, traditional methods of exoplanet detection cannot be used.

In addition to the grooves, observations from ALMA have shown other distinct structures in protoplanetary discs, such as banana- or peanut-shaped arcs and clumps. It had been thought that at least some of these structures were also driven by planets.

“Something must be causing these structures to form,” said lead author Professor Roman Rafikov from Cambridge’s Department of Applied Mathematics and Theoretical Physics, and the Institute for Advanced Study in Princeton, New Jersey. “One of the possible mechanisms for producing these structures – and certainly the most intriguing one – is that dust particles that we see as arcs and clumps are concentrated in the centres of fluid vortices: essentially little hurricanes that can be triggered by a particular instability at the edges of the gaps carved in protoplanetary discs by planets.”

Working with his PhD student Nicolas Cimerman, Rafikov used this interpretation to develop a method to constrain a planet’s mass or age if a vortex is observed in a protoplanetary disc. Their results have been accepted for publication in two separate papers in the Monthly Notices of the Royal Astronomical Society.

“It’s extremely difficult to study smaller planets that are far away from their star by directly imaging them: it would be like trying to spot a firefly in front of a lighthouse,” said Rafikov. “We need other, different methods to learn about these planets.”

To develop their method, the two researchers first theoretically calculated the length of time it would take for a vortex to be produced in the disc by a planet. They then used these calculations to constrain the properties of planets in discs with vortices, basically setting lower limits on the planet’s mass or age. They call these techniques ‘vortex weighing’ and ‘vortex dating’ of planets.

When a growing planet becomes massive enough, it starts pushing material from the disc away, creating the tell-tale gap in the disc. When this happens, material on the outside of the gap becomes denser than material on the inside of the gap. As the gap gets deeper and the differences in density become large, an instability can be triggered. This instability perturbs the disc and can eventually produce a vortex.

“Over time, multiple vortices can merge together, evolving into one big structure that looks like the arcs we’ve observed with ALMA,” said Cimerman. Since the vortices need time to form, the researchers say their method is like a clock that can help determine the mass and age of the planet.

“More massive planets produce vortices earlier in their development due to their stronger gravity, so we can use the vortices to place some constraints on the mass of the planet, even if we can’t see the planet directly,” said Rafikov.

Using various data points such as spectra, luminosity and motion, astronomers can determine the approximate age of a star. With this information, the Cambridge researchers calculated the lowest possible mass of a planet that could have been in orbit around the star since the protoplanetary disc formed and was able to produce a vortex that could be seen by ALMA. This helped them put a lower limit on the mass of the planet without observing it directly.

By applying this technique to several known protoplanetary discs with prominent arcs, suggestive of vortices, the researchers found that the putative planets creating these vortices must have masses of at least several tens of Earth masses, in the super-Neptune range.

“In my daily work, I often focus on the technical aspects of performing the simulations,” said Cimerman. “It’s exciting when things come together and we can use our theoretical findings to learn something about real systems.”

“Our constraints can be combined with the limits provided by other methods to improve our understanding of planetary characteristics and planet formation pathways in these systems,” said Rafikov. “By studying planet formation in other star systems, we may learn more about how our own Solar System evolved.”

̽��ֱ��research was supported in part by the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

References:
Roman R Rafikov and Nicolas P Cimerman. ‘Vortex weighing and dating of planets in protoplanetary discs.’ Monthly Notices of the Royal Astronomical Society (2022). DOI: 10.1093/mnras/stac3692 or DOI: 10.48550/arXiv.2301.01789

Nicolas P Cimerman and Roman R Rafikov. ‘Emergence of vortices at the edges of planet-driven gaps in protoplanetary discs.’ Monthly Notices of the Royal Astronomical Society (2022). DOI: 10.1093/mnras/stac3507

Little ‘hurricanes’ that form in the discs of gas and dust around young stars can be used to study certain aspects of planet formation, even for smaller planets which orbit their star at large distances and are out of reach for most telescopes.

It’s extremely difficult to study smaller planets that are far away from their star by directly imaging them: it would be like trying to spot a firefly in front of a lighthouse. We need other, different methods to learn about these planets

Roman Rafikov

ALMA (ESO/NAOJ/NRAO)

ALMA image of the protoplanetary disc around HL Tauri

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