Humongous, Gassy Halo Found Surrounding Milky Way
Our galaxy — and the nearby Large and Small Magellanic Clouds as well — appears to be surrounded by an enormous halo of hot gas, several hundred times hotter than the surface of the Sun and with an equivalent mass of up to 60 billion Suns, suggesting that other galaxies may be similarly encompassed and providing a possible clue to the mystery of the galaxy’s missing baryons — a.k.a., dark matter. The findings were reported by a research team using data from NASA’s Chandra X-ray Observatory.
While observing bright x-ray sources hundreds of millions of light-years distant, the researchers found that oxygen ions in the immediate vicinity of our galaxy were “selectively absorbing” some of the x-rays. They were then able to measure the temperature of the halo of gas responsible for the absorption. The scientists determined the temperature of the halo is between 1 million and 2.5 million kelvins — a few hundred times hotter than the surface of the Sun.