We do not have a clear view of the Milky Ways shape and functions like we do of other galaxies, mainly because we live within it. That gives scientists the tools they need to compare our own galaxy to the many millions of others in the Universe.
This week, an international team of scientists from the USA, UK, and Chile launched a paper that does just that. They dug through a catalogue of ten thousand galaxies produced by the Sloan Digital Sky Survey, searching for galaxies with comparable attributes to our own.
They discovered that the Milky Way has twins– much of them– however simply as numerous that are just ostensibly similar, with fundamental differences buried in the data. What they found has implications for the future development of our own galaxy.
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Digging through the Data
Second, they ruled out galaxies with a significantly various bulge-to-total ratio (the size of the galaxy compared to its brilliant main core). They just chose galaxies with a comparable Hubble Type: a classification system that groups galaxies based on their shape. Some galaxies, like our own, are spiral-shaped, while others, normally older ones, are formed more like fuzzy blobs, and are understood as elliptical galaxies.
A simple representation of Hubble Classifications, with spiral galaxies on the right (barred galaxies on the lower branch) and elliptical galaxies on the. Image Credit: Cosmogoblin (Wikimedia Commons).
At the end of this procedure, the team was left with 138 galaxies superficially similar to our own. From there, they might dig into the details to see just how close our stellar cousins actually are to ourselves.
They plugged the information into a design that forecasts star development, considering how stellar winds blow excess gas away from galaxy, which can be pulled in towards the centre of galaxies. The model also accounted for the chemical structure and metallicity of products within various areas of the galaxies.
What did they discover?
It ends up that there are undoubtedly galaxies out there that look a lot like ours. 56 of the 138 galaxies in the sample ended up being a close match to house.
What defines these Milky Way-like galaxies is that they have a long timescale in which star formation takes place in their external regions, progressively birthing brand-new stars in a leisurely fashion. The inner region, on the other hand, experiences a dramatic period of intense star development early in the galaxys history, spurred on by a flow of gas being pulled inward towards the centre from the external region.
This isnt true for all 138 galaxies studied. A substantial portion of the galaxies which in the beginning look appeared comparable to the Milky Way ended up looking extremely various on closer examination. These fall under 2 categories.
The first category (including 55 of the 138 galaxies) are galaxies that appear to have no differentiation at all in between their external and inner regions. These galaxies are experiencing star development evenly, in a long sluggish extended procedure without the wild burst in the core. In these galaxies, stars in both the outer and inner areas appear identical.
The 2nd classification, meanwhile, includes what are referred to as centrally-quenched galaxies (27 of 138), and these are maybe the strangest of the lot. These outliers appear to lack any substantial period of recent star formation from recycled product in their cores, implying that the radial inflow of gas from the outer regions that we see in the Milky Way isnt occurring in these galaxies.
One constant feature of these centrally-quenched galaxies is that they appear, as a guideline, to have actually completed most of their star formation in the past, hinting that possibly they might be older than the Milky Way.
If thats true, maybe we are taking a look at the Milky Ways own future. Our galaxy may someday likewise wind up with a quenched centre, and these galaxies therefore represent a sneak peek of the next phase of galactic evolution.
” Perhaps these galaxies are the evolutionary followers of the Milky Way, which are even more along in their lives,” compose the authors.
They likewise pose some other possible descriptions, such as an extremely active galactic nucleus that may suppress star development in the inner regions of the galaxies.
Theres still much to learn, but this study offers a great deal of new possibilities to chew on when it concerns stellar advancement. Basically, it reveals that we are not totally distinct. There is a massive range of galaxy types in the Universe, however a minimum of a few of them play by the very same guidelines as the Milky Way, and lots of are at the exact same life phase. Studying these look-alikes can assist us find out more about our own house, giving us the next best thing to holding our galaxy approximately a mirror and showing us our reflection.
The paper is readily available in preprint format on ArXiv:
Shuang Zhou, Alfonso Aragón-Salamanca, Michael Merrifield, Brett H. Andrews, Niv Drory, Richard R. Lane. “Are Milky-Way-like galaxies like the Milky Way? A view from SDSS-IV/MaNGA.”
Featured Image Credit: Pablo Carlos Budassi (Wikimedia Commons).
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Second, they ruled out galaxies with a greatly different bulge-to-total ratio (the size of the galaxy compared to its bright main core). They just chose galaxies with a comparable Hubble Type: a classification system that groups galaxies based on their shape. Some galaxies, like our own, are spiral-shaped, while others, normally older ones, are shaped more like fuzzy blobs, and are understood as elliptical galaxies. The very first classification (consisting of 55 of the 138 galaxies) are galaxies that appear to have no differentiation at all between their inner and external areas. There is a massive variety of galaxy types in the Universe, however at least some of them play by the very same guidelines as the Milky Way, and many are at the very same life stage.