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When you think about it, given the immensity of space compared to the minutia of all matter, it is surprising that galaxies meet and blend. Yet they do it. Astronomers have known for a long time, for example, that our galaxy, the Milky Way, will merge with the great galaxy next to Andromeda, within 4 to 8 billion years. And just last week, we learned that the Great Magellanic Cloud would also collide with our Milky Way. This small galaxy will merge with ours in only 2 billion years, eventually destroying our solar system of the Milky Way. In the deep space, astronomers see and study the galaxies in fusion. On January 9, 2019, at the 233rd AAS meeting in Seattle, Washington, the astronomers of the Sloan Digital Sky Survey (SDSS) announced that they had access to the satellite. a new tool to look for mergers of galaxies that would be "missing".
They are looking for these galaxy fusions in the data from a survey called MaNGA (mapping galaxies close to the Apache Point Observatory), which is part of SDSS. Astronomers said in a statement:
These results show that by going beyond simple galaxy fusion research based on their appearance, astronomers will now be able to find more galaxy fusions than ever before.
Billions of years can take billions of years to blend completely into a single galaxy. When astronomers look out into space, they can only see "snapshots" of this long process of fusion. Located 300 million light-years away from the constellation Coma Berenices, these 2 colliding galaxies have been dubbed The Mice because of the long tail of stars and gases emanating from each galaxy. Also known as NGC 4676, the couple will eventually merge into one giant galaxy. Image via Wikimedia Commons.
Rebecca Nevin, from the University of Colorado, is the lead author of the new galaxy study, which served as the foundation for her doctoral dissertation in Colorado, with astronomer Julie Comerford as a consultant. Nevin commented:
The fusion of galaxies is essential to understanding the evolution of galaxies, but their search can be tricky.
Astronomers have stated that the magnificent visible characteristics of galaxy fusion – the giant tidal currents of stars and unusual shapes – are visible only in a small fraction of those observed. They said that some galaxies that did not seem to merge were maybe merging, after all. Their statement explained:
Astronomers have come up with a way to find these hidden fusions. They created a method that uses merged galaxy simulations to predict what the mergers would look like and how the stars of these galaxies would move.
By comparing their results with galaxy observations from the SDAP's MaNGA (Near Apache Point Observatory Galaxy) study, astronomers will be able to do much better at identifying melt-up galaxies in the wild.
Laura Blecha from the University of Florida – another member of the team – said:
These simulations allow us to predict the most subtle signs of galaxy fusion, so that we can find mergers in previously masked SDSS data.
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This montage of 6 images of the Hubble Space Telescope shows 6 galaxies at different stages of the fusion process. For more information on these galaxies, visit SpaceTelescope.org. Image via Hubble Heritage Team / NASA / ESA / A. Evans / SDSS.
The team's method works in part by analyzing images of galaxies:
They essentially produced a galactic photo album, including images of galaxies at all stages of their fusion. Previously, astronomers' 'photo albums' on galaxy fusions were rare, including only galaxies at the fusion stage where they looked like spectacular fusions.
Nevin says:
Nowadays, it would be totally unthinkable to take only one or two selfies a year. We have modernized the photo album of galaxy fusion. It's now like taking a selfie of galaxy fusion a day for years.
Astronomers plan to make these large photo albums available to everyone. Astronomers will use them to study the evolution of galaxies during their fusion.
Learn more about the work of these astronomers via SDSS
Three galaxies observed by the survey SDSS MaNGA. The top row shows images of galaxies, while the bottom row shows the speed of stars in galaxies; the red means that the stars are moving away from us and the blue means towards us. The left panel shows an isolated spiral galaxy, not the object of a merger. The middle panels show a spectacular pair of confusing galaxies, evident both in the picture and in the speed chart. The right panels show what appears in the image as being a single galaxy – but the velocity map reveals that it is actually a galaxy that has just merged. This is evident in the disturbed (counter-rotating) features of the speed chart. This example demonstrates the power of the team's new method, which will identify fused galaxies using both imaging and kinematics. Image via Rebecca Nevin and the SDSS
Conclusion: astronomers have developed a new technique for studying galaxy fusion.
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