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 surprise phenomena of ‘starquakes’—massive tsunami-like movements on the surface of stars 

The story so far: The third dataset released by the European Space Agency’s star-mapping Gaia probe, covering almost 1.8 billion stars in the Milky Way galaxy, has revealed an unexpected phenomena called ‘starquakes’, which are similar to earthquake-like movements but on the surface of stars.

The data has also revealed the largest chemical map of the entire Milky Way, showing the DNA of millions of stars, which includes their age, mass, chemical composition, colour, temperature and metal content. Besides, the new data has also made discoveries about binary star systems, quasars, asteroids, and exoplanets.

Scientists, in the years to follow, will interpret several terabytes of data to make discoveries about astronomical phenomena. The second dataset in 2018 allowed astronomers to show that the Milky Way merged with another galaxy in a violent collision around 10 billion years ago.

The Milky Way, our home galaxy, is just one of the estimated one to two hundred billion galaxies of varied shapes and sizes in the universe. Roughly 13 billion years old, the Milky Way is a barred spiral galaxy consisting of 100 to 200 billion stars, with the sun as its local star.

The galaxy is shaped like a flattened disc spread across 100,000 light-years with spiral arms. The majority of the stars are located in the disc, scattered around 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 positioned between the centre and the periphery of the galaxy.

Outside the bulge and the disc exists a halo of isolated stars and ancient clusters of stars, and further beyond this is an even bigger halo of invisible dark matter.

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