How much does the Milky Way weigh?

Having processed the new observational data on fifty dwarf galaxies - satellites of the Milky Way, a group of astrophysicists from the UK and the USA gave a new estimate of the mass of our galaxy. According to this new estimate, visible matter - stars, clouds of interstellar gas and dust, accounts for only 15% of the mass of the Milky Way, everything else - dark matter, distributed around the periphery - in the halo of the galaxy.

Galaxies are in constant motion; when they collide with each other, new, more massive galaxies form. Our closest galactic neighbor, Andromeda, flies towards the Milky Way at a speed of 110 km / s, the collision should begin in 4.5 billion years. As they move through outer space, large galaxies attract smaller clusters of stars that occupy orbits and accompany large galaxies in much the same way that planets revolve around stars and satellites around planets and smaller cosmic bodies. The dynamics of all participants in cosmic motion is determined by mass, distance and acceleration. Observing the rotation of the satellite galaxies of the Milky Way, astrophysicists calculate the nature of the movement and the mass of the latter; there are no other ways to do this, since we cannot observe our own galaxy from the side.

Unlike other researchers, who calculated the mass of the Milky Way, the authors of the new work did not rely on the speed of satellite galaxies and changes in their position relative to the Earth, but on the angular momentum - a physical quantity that determines the distance between objects and their speed. Satellite galaxies rotate in elliptical orbits, accelerating in areas closer to the center of the Milky Way, and decelerating as they move away. Unlike the speed of movement in orbit, the angular momentum does not change, therefore, the authors of the work believe that their estimate can be more accurate than the previous ones. In addition, it will be possible to clarify the mass of our galaxy when new data from new devices arrive; astrophysicists have high hopes for the Gaia space observatory, which entered the calculated orbit four years ago and the LSST (Large Synoptic Survey Telescope, Large Observation Telescope).

The mass of the galaxy, according to a new estimate, is 0.96 trillion solar masses; other estimates gave both more and less - from 700 billion to two trillion solar masses; old calculations confirming that the closest galaxy of Andromeda to us are more massive than ours were confirmed. We checked the new assessment on a computer model - a simulation of the Universe, consisting of 20 thousand galaxies resembling ours, and another 90 thousand satellite galaxies that revolve around them.

The article was published in The Astrophysical Journal .


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