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Updated November 26th, 2021 at 17:09 IST

Gaia satellite data states dwarf galaxies aren't Milky Way's satellites as earlier thought

A new set of data from ESA's Gaia satellite has suggested that the galaxies nearby the Milky Way are newcomers to the universe rather than satellite galaxies.

Reported by: Harsh Vardhan
Milky Way
Image: ESA | Image:self
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A new set of data from the European Space Agency's (ESA) Gaia satellite suggested that the galaxies nearby the Milky Way are newcomers to the universe and not satellites as earlier thought. Our galaxy, the Milky Way is surrounded by many dwarf galaxies which orbit it and were thought to be satellite galaxies that accompanied ours for billions of years. In simpler terms, a new study shows that these dwarf galaxies are not as old as scientists thought and have not yet been trapped under the Milky Way's influence. A galaxy is termed dwarf when it comprises stars in numbers between 1,000 to several billion.

Scientists mapped 40 dwarf galaxies around the Milky Way

Scientists confirmed the aforementioned theory by computing the motion of 40 dwarf galaxies that are revolving around the Milky Way. According to the ESA, astronomer François Hammer, and his colleagues from China and parts of Europe calculated the movement of the galaxies by computing velocities, orbital energy and the angular (rotational) momentum of each galaxy. The results revealed that each of the galaxies was moving too fast as compared to other giant stars and star clusters.

This means that their speeds are too much to orbit the Milky Way yet because their orbital energy and angular momentum would have been destroyed if that was the case. Further elaborating the same, ESA quoted François as saying "The Milky Way is a big galaxy, so its tidal force is simply gigantic and it's very easy to destroy a dwarf galaxy after maybe one or two passages". Our galaxy also has a reputation of being a cannibal as it has consumed many dwarf galaxies in its past such as the Gaia-Enceladus, which was destroyed 8-10 billion years ago or the Sagittarius dwarf galaxy 4-5 billion years ago.

Talking about the new findings, Timo Prusti, Gaia Project Scientist said as per ESA, "Thanks in large part to Gaia, it is now obvious that the history of the Milky Way is far more storied than astronomers had previously understood. By investigating these tantalising clues, we hope to further tease out the fascinating chapters in our galaxy’s past". Launched in December 2013, ESA's Gaia is a star surveyor which has been assigned a job to create a three-dimensional map of over a thousand million stars throughout our Milky Way galaxy and beyond.

Image: ESA

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Published November 26th, 2021 at 17:09 IST

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