Gaia’s Multi-Billion-Star Map of Milky Way

Global Astrometric Interferometer for Astrophysics (Gaia), a project of the European Space Agency (ESA), which maps the Milky Way, launched on June 13 at 6 a.m. ET. Astronomers from all over the world flocked to the Gaia Archive, which serves as the landing page for all of the mission’s data. Mission authorities have finally released Data Release 3 (DR3) to the public after years of calibrating and validating the spacecraft’s measurements of the motion, speed, brightness, composition, and other characteristics of hundreds of millions of stars. Scientists started searching DR3 for the upcoming huge findings in black holes, asteroids, galactic archaeology, exoplanets, and more while reading news releases and posting images of telescope-themed desserts on Twitter.

Within minutes of the publication, the ESA unveiled updated three-dimensional maps of the Milky Way and unleashed a flood of fresh data on the billions of stars in our vicinity, including their composition, direction of motion, age, and speed. All of this was done in support of Gaia’s core objective of surveying the sky to better understand our galaxy.

“I didn’t anticipate such positive coverage for us. Having worked on Gaia since the late 1990s, astronomer Ronald Drimmel of the Astrophysical Observatory of Turin at Italy’s National Institute for Astrophysics and a member of the Gaia Data Processing and Analysis Consortium (DPAC) says, “All those maps—my jaw dropped.

Just long enough to put together a report, one of the numerous papers the DPAC team prepared to show what is possible with DR3, Drimmel spent a few months prior to the release verifying some of Gaia’s observations. Drimmel and his colleagues mapped out the stellar motions of various parts of our galaxy using new measurements of the 3-D trajectories of more than 33 million stars—including their motion toward and away from us, not just across the sky—in particular those for the Milky Way’s two trailing spiral arms and the flattened, bar-shaped centre between them. Researchers can reverse engineer the formation of our galaxy’s peculiar spiral shape and better understand how such structures may arise by understanding how the stars in these diverse regions move today.

According to Adrian Price-Whelan, an astronomer at the Center for Computational Astrophysics (CCA) at the Flatiron Institute in New York City, who co-authored a new paper that was posted to the preprint server just one day after DR3’s release, “Now we’re in an era, at least for the Milky Way, where we can see all of this very dynamic stuff happening.” They searched for indications of modifications in the Milky Way’s structure brought on by occurrences like close encounters with the Sagittarius dwarf galaxy using the updated star movements in DR3.

—a tiny galaxy’s remnant stuck in our galaxy’s death spiral. Researchers are able to identify significant moments in the Milky Way’s turbulent past by studying this and other “satellite” galaxies, which reveals the titanic intergalactic collisions and close calls that over the course of billions of years gave rise to our familiar spiral of stars. As explained by Price-Whelan, “the history of our galaxy is what objects have accreted into and been absorbed by the Milky Way over time—both that’s tied to the construction of our galaxy and also has implications for the patterns that we observe in the galaxy.”

Gaia’s accurate motion measurements are essential for locating smaller-scale systems inside the galaxy, such as binary stars and stars circling more unusual astroparticles like neutron stars and black holes. In essence, the death of big stars left behind these dense “stellar remains.” Researchers anticipate discovering a black hole in a binary from the Gaia data soon if the massive stars are in binary systems since astronomers’ theories predict that the remnants will continue orbiting their live partner stars.

According to Katie Breivik, an astronomer at the CCA, “we’re all thrilled about black holes; everyone’s champing to locate the black hole.” However, when searching through the vast new collection of binary systems in DR3 in the days following its release, “we were like, ‘Really? Nothing is present? Not a single enormous black hole is shouting at us? But it’s all right. Our dreams have not yet been shattered.

Breivik still has a lot to accomplish. The ability to examine double stars of all different masses, types, and stages of evolution, she claims, will be the “true ‘powerhouse’ research” that the Gaia data will deliver. Breivik has been improving artificial iterations of the Gaia data for binary star systems since the data release. In order to do this, she creates fake star populations using mathematical models, which she later compares to the actual Gaia results to see where the gaps in our current beliefs are.

Binaries are just the beginning of the fun with stars. According to Jacqueline Faherty, an astronomer at the American Museum of Natural History in New York City, “one of the things that I’m doing with [DR3] right now is working on a very local sample of stars.” She is trying to figure out where stars come from and where they are headed. The eagerly awaited inclusion of stellar spectra in DR3, which show how a star’s brightness varies in line with the wavelength, or colour, of its emitted light, aids Faherty’s study. The temperature and chemical makeup of stars are revealed via spectra. Stars that may have originated in the same locations can be located using the fingerprints of various elements found in spectra.

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