The Milky Way is the biggest galaxy on the block, but that doesn't mean it's alone. Through its powerful gravitational clout, our galaxy has grabbed onto a few smaller galaxies during its 13-billion-year evolution that remain in orbit to this day. Eventually these so-called satellite galaxies may be consumed by the galactic behemoth, but for now, the Hubble Space Telescope has zoomed into the heart of one of them, producing a sparkling and colorful nebula photograph for the holiday season.
This observation is of two overlapping nebulae inside the Small Magellanic Cloud, a dwarf galaxy that's a little under 200,000 light-years from Earth. Astronomers often study the SMC (and its bigger sibling, the Large Magellanic Cloud) as it is so close that it can be easily seen in Southern Hemisphere skies. As they are so close, observatories like Hubble can study the stars and nebulae they contain and, in this case, the nebula pair of NGC 248 has been showcased.
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Originally discovered by English astronomer John Herschel in 1834, NGC 248 are two clouds of hydrogen glowing under the heat by the stars they contain. Though beautiful, a holiday snapshot wasn't the sole purpose of this observation. As a part of the Small Magellanic Cloud Investigation of Dust and Gas Evolution (SMIDGE) project, this study is being used to understand why other galaxies beyond the Milky Way are so depleted in dust, whereas the Milky Way is very well endowed with the stuff.
The SMC in particular has between 10-20 percent the amount of dust that our galaxy has and SMIDGE is trying to figure out why it contains such small quantities of the heavy elements required to form an abundance of dust. It's as if this small satellite galaxy is a remnant of our ancient universe, before there was a proliferation of heavy elements that fill large galaxies like the Milky Way. By doing so, it is hoped that we may gain a few more clues at to how our galaxy came to be and why it evolved in a different way to these ancient dwarf galaxies.
"It is important for understanding the history of our own galaxy, too," said Karin Sandstrom, of the University of California, San Diego, and principal investigator of the study. "Dust is a really critical part of how a galaxy works, how it forms stars."
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