HUN-REN Research Centre for Astronomy and Earth Sciences
Konkoly Thege Miklós Astronomical Institute

New Gaia release reveals rare lenses, half a million more stars, and unforeseen science

2023. october 18. | Szerző: CSFK

Press Release

ESA's Gaia mission released a goldmine of knowledge about our galaxy and beyond. Four hundred scientists worked on the mission’s latest ‘focused product release’ (FPR), with the active involvement of eight researchers from the Observatory.

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

The mission’s latest ‘Focused Product Release’ builds further on this, providing many new and improved insights into the space around us. The release brings exciting and unexpected science: findings that go far beyond what Gaia was initially designed to discover and dig deep into our cosmic history. It is the work of more than four hundred researchers who form the Gaia Data Processing and Analysis Consortium, or DPAC. Among them, nine scientists from the Konkoly Observatory of the HUN-REN Research Centre for Astronomy and Earth Sciences participated in this release.


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 jigsaw 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 and a great example of a ‘typical’ cluster. 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.

Az omega Centauri gömhalmaz képe, egyesítve a korábbi és új adatokat. (Forrás: ESA/Gaia/DPAC)


“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.

“It’s not just patching up holes in our mapping, although this is valuable in itself,” adds co-author and Gaia Collaboration member Alexey Mints, also of the AIP. “Our data allowed us to detect stars that are too close together to be properly measured in Gaia's regular pipeline. With the new data we can study the cluster’s structure, how the constituent stars are distributed, how they’re moving, and more, creating a complete large-scale map of Omega Centauri. It’s using Gaia to its full potential – we’ve deployed this amazing cosmic tool at maximum power.”

This finding not only meets, but actually exceeds Gaia’s planned potential. The team used an observing mode designed to ensure that all of Gaia’s instruments are running smoothly. “We didn’t expect to ever use it for science, which makes this result even more exciting,” adds Weingill.

A Hubble űrtávcső felvétele az omega Centauri belsejéről. A sárga csillagok szerepeltek a Gaia DR3 katalógusban, a pirosak az újonnan azonosított csillagok. (Forrás: ESA/Gaia/DPAC, Hubble)


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, 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 curious and rare configurations are visually intriguing and hold immense scientific value, revealing unique clues about the very earliest days and inhabitants of the Universe.

“Gaia is a real lens-seeker,” says co-author Christine Ducourant of Laboratoire d’Astrophysique de Bordeaux, France, and a member of the Gaia collaboration. “Thanks to Gaia, we’ve found that some of the objects we see aren’t simply stars, even though they look like them. They’re actually really distant lensed quasars – extremely bright, energetic galactic cores powered by black holes. We now present 381 solid candidates for lensed quasars, including 50 that we deem highly likely: a goldmine for cosmologists, and the largest set of candidates ever released at once.”

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.

Felül: három lencsézett kvazár képei a Pan-STARRS felmérés képein, a Gaia által azonosított forrásokat bejelölve. Alul: a lencsére létrehozott szintetikus kép, amely a kvazár összes lencsézett képét tartalmazza. (Forrás: „Gaia Focused Product Release: A catalogue of sources around quasars to search for strongly lensed quasars”, Gaia Collaboration, A. Krone-Martins, et al. 2023)


“The great thing about Gaia is that it looks everywhere, so we can find lenses without needing to know where to look,” adds co-author Laurent Galluccio of Université Côte d’Azur, France, and member of the Gaia collaboration. “With this data release, Gaia is the first mission to achieve an all-sky survey of gravitational lenses at high resolution.”

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 recently 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. The 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.

Ilyen mértékű javulást ért el a kisbolygók pályaparamétereiben a Gaia. (Forrás: ESA/Gaia/DPAC - CC BY-SA 3.0 IGO)


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. The Gaia team stacked six million spectra to study these signals, forming an incredibly large dataset of weak features that have never before been measured in such a large sample. The dataset will hopefully allow scientists to finally 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 complex and intertwined physical and chemical processes active throughout our galaxy, and to understand more about the material lying between stars.

Az egyik diffúz csillagközi sáv erőssége a Tejútrendszerben, 5400 fényévre a Naptól. (Forrás: ESA/Gaia/DPAC)


Last but by no means least, a paper characterises the dynamics of 10,000 pulsating and binary red giant stars in by far the largest such database available to date. Brightness variations of these stars were part of Gaia DR3: this release complements them with line-of-sight velocity variations based on spectroscopy. This made it possible, for example, to separate motions caused by binary stars orbiting each other from pulsating motions of the stellar surface. The new release provides a better understanding of how these fascinating 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," says Timo Prusti, Project Scientist for Gaia at ESA. "Although its key focus is as a star surveyor, Gaia is exploring everything from the rocky bodies of the Solar System to multiply imaged quasars lying billions of light-years away, far beyond the edges of the Milky Way. The mission is providing a truly unique insight into the Universe and the objects within it, and we’re really making the most of its broad, all-sky perspective on the skies around us."

The next steps

The space telescope is expected to remain operational until 2025, but the vast amount of data it collects will provide work for the consortium involving Hungarian participation for years to come. "Gaia is clearly the flagship of European space astronomy. Our participation in ESA missions shows that Hungarian astronomers are at the forefront of science. We are not merely using the released data; we are also actively contributing to its production," summarized László Molnár, a researcher at HUN-REN CSFK Konkoly Observatory and a member of the Gaia consortium.

Gaia’s previous Data Release, Gaia DR3, came on 13 June 2022. The 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.

Ábrahám Péter, Kóspál Ágnes, Kun Mária, Marton Gábor, Molnár László, Nagy Zsófia, Plachy Emese, and Szabados László from the HUN-REN CSFK participated in the Gaia Focused Product Release.





László Molnár (HUN-REN CSFK):

HUN-REN CSFK press officer Adrienn Ádám:


Papers comprising the Gaia focused product release: 

  • Gaia Focused Product Release: spatial distribution of two diffuse interstellar bands
  • Gaia Focused Product Release: Asteroid astrometry and orbits
  • Gaia Focused Product Release: A catalogue of sources around quasars to search for strongly lensed quasars
  • Gaia Focused Product Release: radial velocity time series of Long-Period Variables
  • Gaia Focused Product Release: Sources from Service Interface Function Image Analysis