Milky Way Galaxy is dwarfed by its massive hot gas "halo"

Check out the insane scale of this artist's representation of the Milky Way Galaxy, looking tiny and insignificant in the middle of a huge ball of hot gas. The image shows the hot gas extending with a radius of 300,000 light years — but NASA says it may "extend significantly further."

A new study, based on data from NASA's Chandra Observatory, has found evidence that this "halo" could have a mass comparable to that of all the stars in the galaxy. And this could be the long-sought explanation for the "missing baryon" problem — as the James Webb Telescope's Henry C. Ferguson explains here, baryons are composite particles that include protons and neutrons. And our best estimates are that the stars, gas and dust inside galaxies only account for at most 40 percent of the baryonic matter that the Big Bang Theory would predict. So where's the rest?


Using Chandra's X-ray observatory, lead researcher Anjali Gupta and his team were able to study X-rays from sources hundreds of millions of light-years away and see how they were absorbed by the circumgalactic medium (CGM) around our own galaxy. And as a result, they found that the CGM appeared to be much bigger than people had previously estimated. This "halo" is between 1 million and 2.5 million kelvins, or hundreds of times hotter than the surface of our sun. But its density is so low, that we can't detect similar halos around other galaxies.


You can read the entire paper, published in the Sept. 1 issue of The Astrophysical Journal, here.

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