Orbital telescope speed tests the Milky Way's "halo"
Using archival data from ESA'sXMM-Newton orbital telescope, a team of astronomers from theUniversity of Michigan has calculated the speed of the vast halocomposed of incredibly hot gas that surrounds the MilkyWay. The halo is thought to have a mass the equivalent of all of thestars in our galaxy combined, and by understanding it, we could gaininsights into the formation, and future evolution of the Milky Way.
It has been less than five centuriessince Copernicus proposed his theory that the Sun, rather than theEarth, lay at the center of our solar system. In the relatively shorttime since this humble beginning, mankind's understanding of oursolar system, and the galaxy in which it resides, has advanced at anastonishing pace.
We now know that we live in a barred spiral galaxy called theMilky Way, which is composed of billions of stars, all spinningaround a supermassive black hole known as Sagittarius A*, that lurksat the galactic center. Our understanding of how the Milky Way cameto coalesce and evolve is constantly being revised as we discover newcharacteristics and elements of our galaxy.
To further inform our understanding ofthe Milky Way, a team of researchers looked to the haloof hot gas that surrounds our galaxy. Previous observations carried out by NASA'sChandra X-ray Observatory suggest that the halo has a radiusof around 300,000 light-years, though it could be far larger.Furthermore, the gas that makes up the halo is thought to beincredibly hot, with a temperature between 1 million and 2.5 million Kelvins, rendering the matter in the state of ionized plasma.
It had previouslybeen believed that the halo, unlike the ever spinning disk of theMilky Way, was stationary. However, the new study appears to disprovethe standing theory. To gauge the halo's speed, the researchers madeuse of data collected by ESA's XMM-Newton telescope,focusing on thin strips of oxygen embedded within the vast cloud.
Sincemovement stretches the wavelength of light, the team was able toobserve the X-ray signature of the particles, and gauge the speed anddirection of the halo. It was found that the halo was rotating in thesame direction as the disk of the Milky Way, and at a comparable, ifslightly slower, pace. The disk of our galaxy is estimated to spin at around540,000 mph, while the halo moves at some 400,000 mph.
The discoverythat the halo is traveling at a comparable speed and direction asour galaxy will require a rethink to current models regarding theevolution of our galaxy.
Theresults indicate that the halo is perhaps the source of a significantamount of the star and planet forming matter that makes up the disk of our Milky Way.Furthermore, by studying the spin of the halo, astronomers hope togauge the rate at which the vast cloud may grant infusions of matterinto the disk of the Milky Way in the distant future.
The Milky Way's gas halo could provevital in mankind's ongoing mission to gain a deeper understanding of the myriad of galaxies that populate the cosmos. It is now thought possible that these vast galactic halos could account for some of theordinary, or baryonic matter, which is expected, yet missing, in surveys made of the observableuniverse.