The universe is vast, but Gaia has no fear. Launched in December 2013 by the European Space Agency (ESA), the Gaia Space Observatory, short for Global Astrometric Interferometer for Astrophysics, is an astronomical observatory mission set to precisely record stellar data in amounts and with precisions never achieved before. Gaia has released three groundbreaking datasets in 2016, 2018 and 2020, and is set to cease operations in 2022.

Gaia space observatory
3D image of Gaia spacecraft

However, despite Gaia’s ongoing groundbreaking work, it is often overlooked. In the middle of Hubble’s legacy and the excitement of James Webb, set to launch in December, the value of Gaia’s achievements is somewhat lying in the shadows. In this article, we attempt to shed light on Gaia as being a mighty successor to Hubble.

Gaia’s scientific objectives

Gaia was tasked with one fundamental aim: aggregating stellar data of unforeseen precision to craft a three-dimensional catalog of over 1 billion astronomical objects or 1% of our galaxy’s stars. To achieve this goal, Gaia will track each targetted star, measuring its motion around the center of the galaxy. To augment the precision of this tracking, Gaia will observe each of these stars an average of 70 times over five years to track its brightness and location over time.

Gaia space observatory
Credits: ESA

Eventually, Gaia will provide us with an exact – if not the most precise – map of the Milky Way’s composition, formation, and evolution. Beyond the Milky Way, Gaia also aims to target some stellar objects from neighboring galaxies; part of what is known as the Local Group, a dumbbell-shaped galaxy group that consists of the Milky Way, the Andromeda Galaxy, and their respective satellite galaxies. 

The specifications of the spacecraft and its operation

Gaia is a space observatory equipped with three main instruments: an astrometric instrument, a photometric instrument, and a radial velocity spectrometer. These will help Gaia record stereoscopic (relating to depth and three-dimensional position) and kinematic (relating to their velocity and movement) data of the stars.

Gaia was launched by a Russian Soyuz rocket whose upper stage (the upper section of the rocket – after detachment) brought Gaia into orbit. After a year of calibration, Gaia finally found itself in operational orbit in 2014 at the height of the Sun-Earth L2 Lagrange point about 1.5 million kilometers away from Earth. The L-2 Lagrange point is one of the few points between the Sun and the Earth where their gravitational pull on one another balances out.

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When Gaia is conducting observations, the observatory will spin once every six hours to sweep both its telescopes across the entire sky it is panning. This gives Gaia a capacity to scan and measure about 100’000 stars per minute and can therefore pan the entire sky once every two months. 

Gaia’s initial discoveries and first dataset

Only a year after its launch, Gaia discovered the first supernova in 2014. After that, Gaia went on to study the stellar composition of the Milky Way. Its first dataset was to be released in 2016. Therefore, Gaia focused on processing as much data as possible. Its first mission to map the skies was to aggregate stellar density data. This allowed the ESA, in 2016, to release the positions and G magnitudes for the 1.1 billion observed stars.

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In addition, Gaia had also recorded the motions and distances for about 2 million of the billion studied. After this first period, it could be affirmed that Gaia was on the right path! Indeed, this first dataset had been a trial period or test run allowing scientists and astronomers to verify the observational strategy of Gaia. In turn, Gaia’s first dataset was referred to in more than 300 scientific research papers.

Gaia’s developpment and second dataset

In 2018, ESA released the second dataset that Gaia had aggregated. This time, the position of 1.7 million stars had been mapped. The second dataset also concentrated on measuring the stars’ brightness and optical wavelengths for half a million stars. It also included the brightness for quasars. The colors and distances for about 1.3 billion of the total were calculated, and the velocities were determined for a set of 7 million stars. However, Gaia’s work goes beyond that of mapping stars. In this period, Gaia also concentrated on moving bodies such as asteroids to map their trajectories and orbits.

Gaia’s most recent results and their applications

In 2020, Gaia released its most recent dataset, which greatly improves upon the last two published in 2016 and 2018. On average, it improved the past data’s quality by about two-fold, especially relating to the motion of the stars. 

In the past four years, Gaia’s datasets have already helped scientists peer into the past of our galaxy. Indeed, Gaia had spotted the corpse of an ancient galaxy cannibalized by the Milky Way billions of years ago. In addition, on a more direct time frame, 20 hypervelocity stars have been recognized, and the data has helped NASA adjust the path of its space probes in the face of incoming asteroïds. 

Finally, Gaia was set to release the last dataset in 2022. However, due to the high demand and quality of its data, the ESA has decided to release preliminary datasets to publish at least 2 datasets before 2022. As a result, and due to the success of Gaia’s measurements, its mission will most likely be extended until 2025, if not longer!

Learn Astrophysics at Home:

Did you always want to learn how the universe works? Then, read our 30-article Basics of Astrophysics series absolutely free of cost. From the popular topics such as stars, galaxies, and black holes to the detailed concepts of the subject like the concept of magnitude, the Hertzsprung Russell diagram, redshift, etc., there is something for everyone in this series. All the articles are given here. Happy reading!

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