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CosmosUp | January 19, 2019

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Andromeda Galaxy had a much more Violent History than Milky Way

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Andromeda Galaxy had a much more Violent History than Milky Way

To a distant observer, our own Milky Way and the Andromeda galaxy would probably look very similar. Although Andromeda is longer, more massive, and more luminous than the Milky Way, both galaxies are vast spirals composed of hundreds of millions of stars.

Recently, The Hubble Space Telescope has captured an amazing new photo of the Andromeda Galaxy. The new mosaic image represents the sharpest and largest mosaic image of the Milky Way’s galactic neighbor ever taken, Hubble officials said.

The panoramic image shows striking details of the bright galaxy, which is located about 2.5 million light-years from Earth. While that may seem far away, Hubble usually trains its view on more distant targets. Because Andromeda fills up so much of Hubble’s field of view, the telescope was able to capture incredible detail in its survey of the galaxy.

The new image revealed that Andromeda had more violent history, as scientists found a more disordered stellar population than our Milky Way, suggesting that it may have been bombarded by smaller galaxies.

Andromeda galaxy

Hubble Space Telescope has produced the largest and sharpest image ever taken of the Andromeda galaxy. (Photo: NASA, ESA, J. Dalcanton, B. F. Williams, L. C. Johnson, the PHAT team, and R. Gendler.) ~ click to zoom

Puragra Guhathakurta, professor of astronomy and astrophysics at the University of California, Santa Cruz said, “In the Andromeda galaxy we have the unique combination of a global yet detailed view of a galaxy similar to our own. We have lots of detail in our own Milky Way, but not the global, external perspective”.

The detailed study of the disk of the Andromeda galaxy was carried out because of the fact that the structure and internal motions of this stellar disk will hold important keys to understanding the galaxy’s formation history.

The researchers said that if one could look at the disk edge on, the stars in the well-ordered, coherent population would lie in a very thin plane, whereas the stars in the disordered population would form a much puffier layer.

The researchers considered different scenarios of galactic disk formation and evolution that could account for their observations. One scenario involves the gradual disturbance of a well-ordered disk of stars as a result of mergers with small satellite galaxies.

An alternate scenario involves the formation of the stellar disk from an initially thick, clumpy disk of gas that gradually settled. The oldest stars would then have formed while the gas disk was still in a puffed up and disordered configuration. Over time, the gas disk would have settled into a thinner configuration with more ordered motion, and the youngest stars then would have formed with the disk in a more ordered configuration.

Now, thanks to this new research, scientists can cite our own galaxy’s comparative orderliness as strong evidence that we live in a quieter, less cannibalistic neighborhood than most other spiral galaxies in the Universe. “Even the most well ordered Andromeda stars are not as well ordered as the stars in the Milky Way’s disk,” said Dorman.

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Source: http://goo.gl/7l6TMF.



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