Andromeda Not Much Bigger Than Milky Way: Size Matters When Galaxies Collide

Rodiano Bonacci
Febbraio 15, 2018

However, with the latest data fed onto simulators prepared by ICRAR, the Milky Way, and the Andromeda Galaxy are supposed to collide and bind together and not being engulfed by the latter.

Astronomers have long believed the Milky Way would be torn apart and lapped up by its big brother, but new research suggests the two galaxies are actually about the same size. Our home galaxy, the Milky Way, is over a trillion times heavier than our tiny planet Earth so to escape its gravitational pull we have to launch with a speed of 550 kilometers per second.

The team concluded that Andromeda is 800 billion times heavier than the Sun - a figure comparable to the mass of the Milky Way. They calculated the speed that a quick-moving star would need to escape the gravitational pull of its host galaxy to speculate the size of the concerned galaxy.

Astronomers believe our own home galaxy will be swallowed by Andromeda because it is much larger. That is significantly smaller than the 2.5 trillion solar masses from the last estimate, and the new estimate was arrived at by using a new technique - by looking at the escape velocity of objects from within Andromeda. "We used this technique to tie down the mass of Andromeda", said astrophysicist Dr Prajwal Kafle from the University of Western Australia branch of ICRAR, according to an official statement on the ICRAR website.

The Milky Way and Andromeda prior to the merger. Science Alert stated in its post stating that the neighboring galaxy is about 2.5 million light-years away from the Milky Way and belongs to a segment called "Local Group" which encapsulates 30 other galaxies.

Australian scientists say the amount of dark matter in Andromeda is far less than previously estimated - about two-thirds less.

Though scientists are unable to say exactly what will happen when these two galaxies collide, one thing is sure that these new findings have completely altered their understanding of the cosmic bodies.

Their research explains why some of Andromeda's stars orbit the galactic centre erratically, while in the Milky Way, they all go in the same direction.

"We had thought there was one biggest galaxy and our own Milky Way was slightly smaller but that scenario has now completely changed", said Kafle after the surprising find. The team used the velocity technique in order to reexamine the estimate of the mass of the Milky Way, back in 2014.

Researchers published their findings in a paper in the journal Monthly Notices of the Royal Astronomical Society.

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