Context
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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.
Key Findings
- 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.
The Milky Way 
- 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.
What is the Gaia mission?
- Gaia is an ongoing astronomical observatory mission launched in December 2013 by the European Space Agency (ESA) with the objective of creating the most accurate and complete 3D map of the Milky Way by surveying 1% or one billion of the galaxy’s 100 billion stars.
- According to the ESA, “this information allows astronomers to reconstruct the galaxy’s past and future evolution over billions of years.”
- The spacecraft is strategically stationed 1.5 million km from the Earth, in the opposite direction of the sun, in an orbit around the gravitational parking point in space called the Lagrange 2 or L2.
- In order to study the stars and objects, Gaia is also equipped with screening and imaging systems that employ three techniques—astrometry, photometry, and spectroscopy.
- Astrometry is the science of measuring the movement and position of stars within the plane of the sky,
- photometry studies the colour, brightness and other derived properties of stars, and
- spectroscopy measures the radial velocity or the movement of stars towards or away from us by studying stellar spectra or the fingerprints of stars.
- Spectra are obtained by passing the light from a star through a prism which splits it into a spectrum of colours.
- Gaia’s predecessor, ESA’s Hipparcos mission, had mapped the precise positions of 100,000 stars and could gaze 1,600 lightyears away. Gaia, meanwhile, can chart starts and objects as far as 30,000 lightyears.
What has the new data revealed?
- 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 likened to tsunamis or massive vibrations on the surface of stars that can change their shape. Such starquakes were also detected on the surface of stars that should not have any such large-scale vibrations as per existing astronomical theories.
- Quasars: Quasars are extraordinarily active and bright cores of galaxies powered by supermassive black holes. These are the most luminous objects in the universe and are visible along its distant edges. The discovery of new quasars is significant as it helps to measure the most distant stretches of our universe.
- Stellar DNA: The data shows chemical components, colours, brightness, velocity, temperatures, and positions of millions of stars. The chemical composition of the stars also reveals what elements they contain. Only light elements (hydrogen and helium) were formed during the Big Bang. Heavier elements, which scientists call metals, are built inside the stars, and when they die, newer stars are formed with the metals dispersed by dead stars.
- Binary Stars: Binary star systems are two stars that orbit each other around a shared centre. The new data has revealed the position, distance, orbits, and masses of over 8,00,000 binary star systems.
- Asteroids and galaxies: The data has provided a catalogue of more than 156,000 asteroids in our Solar System, which includes their mass, composition, colour, and brightness (from which details of their shape and rotation can be derived).
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