Explained | What is the Gaia space mission and what has it revealed about the Milky Way?

The new data released by the European Space Agency’s Gaia mission has revealed the surprising phenomena of ‘starquakes’ – huge tsunami-like movements on the surface of stars

The new data released by the European Space Agency’s Gaia mission has revealed the surprising phenomena of ‘starquakes’ – huge tsunami-like movements on the surface of stars

The story so far: The third dataset released by the European Space Agency’s Gaia Probe for Star Mappingspanning nearly 1.8 billion stars in the Milky Way galaxy, has revealed an unexpected phenomenon called “starquakes,” which resemble earthquakes, but on the surface of stars.

The data has also revealed the largest chemical map of the entire galaxy, showing the DNA of millions of stars, including their age, mass, chemical composition, color, temperature and metallicity. In addition, the new data has also made discoveries about binary star systems, quasars, asteroids and exoplanets.

Scientists will interpret several terabytes of data in the coming years to make discoveries about astronomical phenomena. With the second data set in 2018, astronomers were able to show that the Milky Way merged with another galaxy about 10 billion years ago in a violent collision.

Anatomy of the Milky Way

Structure of the Milky Way.  Photo: European Space Agency

Structure of the Milky Way. Photo: European Space Agency

The Milky Way, our own galaxy, is just one of an estimated one to two hundred billion galaxies of various shapes and sizes in the universe. About 13 billion years old, the Milky Way is a barred spiral galaxy made up of 100 to 200 billion stars, with the Sun as the local star.

The galaxy is shaped like an oblate disk spanning 100,000 light-years with spiral arms. Most of the stars are in the disk, scattered with a mixture of gas and cosmic dust. The Milky Way has a central bulge where about 10 billion of its oldest stars are concentrated. The sun is between the center and periphery of the galaxy.

Outside the bulge and disk is a halo of isolated stars and old clusters of stars, and beyond it is an even larger halo of invisible dark matter.

The Milky Way is part of a local group of galaxies, including Andromeda, the nearest large galaxy, and nearly 60 smaller galaxies.

What is the Gaia mission?

Gaia mission specs.  Photo: European Space Agency

Gaia mission specs. Photo: European Space Agency

Gaia is an ongoing astronomical observatory mission launched in December 2013 by the European Space Agency (ESA) with the aim of creating the most accurate and complete 3D map of the Milky Way by examining 1% or one billion of the galaxy’s 100 billion stars. . According to the ESA, “with this information, astronomers can reconstruct the galaxy’s past and future evolution over billions of years.”

The Gaia spacecraft took off on a Soyuz rocket from Kourou, French Guiana in 2013, and began scientific screening in 2014. The nearly hat-shaped spacecraft is equipped with two optical telescopes and the largest digital camera in space or the billion-pixel camera, with more than 100 electronic detectors. This camera is accurate enough to capture the diameter of a human hair at a distance of up to 1000 km.

The spacecraft is strategically stationed 1.5 million km from Earth, in the opposite direction from the sun, in orbit around the gravitational parking point in space called the Lagrange 2 or L2.

From here, Gaia maps the precise positions, movements, speed, brightness, temperature and composition of stars in the galaxy and other celestial bodies beyond.

Gaia's three screening techniques.  Photo: European Space Agency

Gaia’s three screening techniques. Photo: European Space Agency

To study the stars and objects, Gaia is also equipped with screening and imaging systems that use three techniques: astrometry, photometry and spectroscopy. Astrometry is the science of measuring the motion and position of stars in the plane of the sky, photometry studies the color, brightness and other inferred properties of stars, and spectroscopy measures the radial velocity or motion of stars toward or away from us. wondering by studying stellar spectra or the fingerprints of stars. Spectra are obtained by passing light from a star through a prism that splits it into a spectrum of colors.

Gaia’s predecessor, ESA’s Hipparcos mission, had mapped the precise positions of 100,000 stars and could see 1600 light-years away. Gaia, meanwhile, can map stars and objects up to 30,000 light-years away.

Gaia makes millions of observations in a single day, and this raw data observed by the spacecraft is processed into meaningful scientific information by the Gaia Data Processing and Analysis Consortium (DPAC), a group of 400 scientists.

Gaia’s data release was planned in four tranches: the first two data sets were released in 2016 and 2018 respectively, the third set is the current one and the final data will be released in 2030 after Gaia finishes mapping the skies in 2025.

What did the new data reveal?

Details of the new data collected by Gaia.  Photo: European Space Agency

Details of the new data collected by Gaia. Photo: European Space Agency

The new set of data released, collected from the Gaia probe between 2014 and 2017, contains enhanced information on nearly two billion celestial bodies, including stars in the Milky Way, objects outside the galaxy and those within our solar system. It contains the largest ever three-dimensional map of stars in the Milky Way. The map shows the chemical compositions, as well as past and future movements of stars.

Starquakes: One of the most surprising discoveries, which the ESA said Gaia was not built to observe, was that of more than 100,000 “starquakes” — which can be compared to tsunamis or huge tremors on the surface of stars that can change their shape. . Such quakes were also detected on the surfaces of stars that, according to existing astronomical theories, should not have such large-scale tremors.

“Starquakes teach us a lot about stars, especially their inner workings. Gaia opens a gold mine for ‘asteroseismology’ of massive stars,” says Belgian-based scientist Conny Aerts, who is part of the Gaia collaboration.

quasars: Quasars are extremely active and bright cores of galaxies powered by supermassive black holes. These are the most luminous objects in the universe and are visible along the far edges. The new Gaia data has revealed the measurements of more than a million confirmed quasars and data related to 6.6 million quasar candidates. This is an increase from the previous dataset which yielded positions of half a million confirmed quasars. The discovery of new quasars is important because it helps to measure the most remote parts of our universe.

Stellar DNA: The data shows chemical components, colors, brightness, speed, temperatures and positions of millions of stars. The chemical makeup of the stars also reveals what elements they contain. During the Big Bang, only light elements (hydrogen and helium) were formed. Heavier elements, which scientists call metals, are built in the stars, and when they die, newer stars are formed with the metals scattered by dead stars. So the chemical composition can be used to determine which stars were born in another galaxy and then migrated to the Milky Way. According to the ESA, astronomers hope to use the data to better understand how stars are born and die, and how the Milky Way has evolved over billions of years.

Previous Gaia data had revealed the correct positions or 2D motions of stars (how they move vertically and horizontally in the plane of the sky), but the new set shows the radial velocity of 33 million stars, i.e. how fast these stars move toward or move away from us. † This could help scientists figure out not only the orbits of the stars, but also their location of origin.

Binary stars: Binary star systems are two stars orbiting a shared center. The new data has revealed the position, distance, orbits and masses of more than 8,000,000 binary star systems. Scientists can use this data to determine the masses of individual stars in the dual system, how stars work, and even discover whether one of the two stars is an exoplanet — a planet that exists outside our solar system and generally orbits a star.

Asteroids and Galaxies: The data has produced a catalog of more than 156,000 asteroids in our solar system, which include their mass, composition, color and brightness (from which details of their shape and rotation can be inferred). In addition to mapping the Milky Way, the data also found magnitudes from 2.9 million other galaxies, including how their stars formed, how far away they are and when they formed.

(With input from agencies)

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