Building the most detailed 3D map of the Milky Way

Building the most detailed 3D map of the Milky Way

Galaxy map art

Gaia is creating an extremely accurate 3D map of more than a billion stars throughout our Milky Way galaxy and beyond. He maps their movements, brightness, temperature, and composition. This massive stellar census will provide the data needed to address a huge range of important questions regarding the origin, structure, and evolutionary history of our Galaxy.

the European Space Agency (ESA) and Gaia’s collaboration teams have published new data in the form of five focused product releases. The results are very promising, making this delivery a first teaser for what will be the fourth release of the Gaia catalog (Gaia DR4), expected by the end of 2025.

The Gaia satellite has been charting the sky since 2014, and its map includes stars a million times fainter than what can be seen with the naked eye. The third edition of the most complete and detailed star catalog (Gaia DR3) was published in June 2022, a milestone in astrophysical research. The extremely precise distances, motions and fundamental parameters that Gaia found, along with the classification of quasars and precise astrometry of asteroids, are now part of the daily work and research of most astronomers.

Gaia maps the stars of the Milky Way

Artistic view of the Gaia satellite in front of the Milky Way. Source: ESA/ATG medialab; Background: ESO/S. Bruner

Most notable discoveries

One of the most notable newly released statements is Omega Centauri globular cluster. The cluster contains about 10 million stars that are extremely crowded in the sky, posing a challenge for Gaia to solve. In light of the Gaia DR4, it is expected that different techniques will be used to process data in the densest and most interesting areas. Reprocessing of the Omega Centauri cluster allowed the astronomical and photometric recovery of an additional 526,587 stars located at its core.

While Gaia observes the same stars multiple times and at different periods, the European Space Agency has only published average measurements so far. Gaia has not been prevented from identifying variable stars, but their properties, such as instantaneous photometry and radial velocities used in the classification process, have not yet been published. While we wait for Gaia DR4 where all observations (epoch and mean) will be available, a partial post of the high quality time series of data acquired for 9164 Long period variables It is part of these focused product releases, and will help the scientific community prepare for the wealth of data that Gaia will provide in 2025.

Spectrum of Mira variants

The ESA-Gaia spacecraft has repeatedly observed the spectrum of an unprecedented amount of cold giant stars — called Mira variables — that are known to continuously expand and contract their surfaces over long periods, sometimes for more than one year. This artist’s impression of the star Mira shows how the speed of the movements of the surface and its atmosphere is precisely measured by the Doppler shifts of the dark lines observed in Gaia’s detailed spectra. Source: Royal Belgian Observatory

Understanding interstellar phenomena

The space between stars is not completely empty. It is filled with a low-density gas made up of atoms, ions and molecules as well as dust. This interstellar material absorbs and scatters light, causing persistent reddening and weakening of the stellar stream. Additional extensive features, named Interstellar gangs are rampantThey also appear in the spectra of stars. This is due to absorption most likely associated with very complex molecules present in the interstellar medium in certain directions. Such interstellar bands are in the wavelength range of the Gaia radial velocity spectrograph and are used to track their formation in milky way The disc and its spiral arms.

Gaia Three gravitationally lensed quasars

For three gravitationally lensed quasars (from left to right: H1413+117, J2240+0321 and J1310-1714), we show in the top row the Gaia DR3 positions (with no special processing of the quasar environment) plotted on ground-based PanSTARRS images. The bottom row shows reconstructed synthetic images from the focused version of the Gaia product (with quasar environment analysis implemented). Observations taken from Earth can be a bit blurry, due to the atmosphere. Thanks to Gaia’s exceptional resolution, these images are resolved to a gravitationally lensed source. Credit: “Gaia-focused product release: Catalog of resources on quasars for searching for strongly lensed quasars” by Gaia Collaboration, A. Krone-Martins, et al. 2023.

From quasars to asteroids

At one end of the distance scale, near the limits of our observable universe, Gaia detects quasars. In the sky, some can be very close to a massive galaxy and have their light path bent by the galaxy’s gravity well, as if passing through a lens. Lensing produces gravitational mirages that can be used to directly estimate the age and expansion rate of the universe. Over the past months, Gaia teams have identified 381 new candidates Quasars and mirages are lensed.

At the other end of the distance scale, Gaia teams reprocessed 156,764 Asteroids, but using 66 months of data instead of the 34 months of Gaia DR3. Thus, observations of most main belt asteroids now cover a complete revolution around the Sun, closing the orbit, leading to a huge increase in Accuracy Of orbits.

Contributions and future expectations

The expertise of astrophysicists from KU Leuven, the Royal Belgian Observatory, Université libre de Bruxelles, Universiteit Antwerpen and Université de Liège plays an important role in the overall processing and analysis of Gaia data, and in the implementation of the focused product. Versions in particular. They are supported in their efforts by the Belgian Federal Office for Science Policy (BELSPO) via the European Space Agency’s PRODEX programme. In addition to providing new data to complement the third release of the Gaia catalog, the focused product releases are proof-of-concept for several new features implemented in the data analysis pipeline that produces Gaia DR4 with twice as much data. It provides a necessary and useful overview of all the promises that the fourth edition of the catalog will deliver.

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