XMM-Newton discovers scorching gas in Milky Way's halo

JANUARY 17, 2020
by European Space Agency



This animated artist's impression shows the Milky Way (the small galaxy depicted at the centre of the frame) and its halo (the extended gaseous region). It illustrates the halo in three different shades – emerald, yellow and green. These all mix together throughout the halo, and each represents gas of a different temperature. Dots then appear across this halo; these represent elements and their relative abundances, as detected by ESA's XMM-Newton X-ray space observatory: nitrogen (black, 41 dots), neon (orange/yellow, 39 dots), oxygen (light blue, 7 dots) and iron (red, 1 dot). A halo is a vast region of gas, stars and invisible dark matter surrounding a galaxy. It is a key component of a galaxy, connecting it to wider intergalactic space, and is thus thought to play an important role in galactic evolution. Credit: European Space Agency


ESA's XMM-Newton has discovered that gas lurking within the Milky Way's halo reaches far hotter temperatures than previously thought and has a different chemical make-up than predicted, challenging our understanding of our galactic home.

A halo is a vast region of gas, stars and invisible dark matter surrounding a galaxy. It is a key component of a galaxy, connecting it to wider intergalactic space, and is thus thought to play an important role in galactic evolution.

Until now, a galaxy's halo was thought to contain hot gas at a single temperature, with the exact temperature of this gas dependent on the mass of the galaxy.

However, a new study using ESA's XMM-Newton X-ray space observatory now shows that the Milky Way's halo contains not one but three different components of hot gas, with the hottest of these being a factor of ten hotter than previously thought. This is the first time multiple gas components structured in this way have been discovered in not only the Milky Way, but in any galaxy.

More:
https://phys.org/news/2020-01-xmm-newton-gas-milky-halo.html