NASA/STScI: Hubble Maps Giant Halo Around Andromeda Galaxy

Find out the latest thinking about our universe.
User avatar
bystander
Apathetic Retiree
Posts: 20392
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

NASA/STScI: Hubble Maps Giant Halo Around Andromeda Galaxy

Post by bystander » Thu Aug 27, 2020 6:10 pm

Hubble Maps Giant Halo Around Andromeda Galaxy
NASA | GSFC | STScI | HubbleSite | 2020 Aug 27
In a landmark study, scientists using NASA’s Hubble Space Telescope have mapped the immense envelope of gas, called a halo, surrounding the Andromeda galaxy, our nearest large galactic neighbor. Scientists were surprised to find that this tenuous, nearly invisible halo of diffuse plasma extends 1.3 million light-years from the galaxy—about halfway to our Milky Way—and as far as 2 million light-years in some directions. This means that Andromeda’s halo is already bumping into the halo of our own galaxy.

They also found that the halo has a layered structure, with two main nested and distinct shells of gas. This is the most comprehensive study of a halo surrounding a galaxy. ...

The Andromeda galaxy, also known as M31, is a majestic spiral of perhaps as many as 1 trillion stars and comparable in size to our Milky Way. At a distance of 2.5 million light-years, it is so close to us that the galaxy appears as a cigar-shaped smudge of light high in the autumn sky. If its gaseous halo could be viewed with the naked eye, it would be about three times the width of the Big Dipper. This would easily be the biggest feature on the nighttime sky.

Through a program called Project AMIGA (Absorption Map of Ionized Gas in Andromeda), the study examined the light from 43 quasars—the very distant, brilliant cores of active galaxies powered by black holes—located far beyond Andromeda. The quasars are scattered behind the halo, allowing scientists to probe multiple regions. Looking through the halo at the quasars’ light, the team observed how this light is absorbed by the Andromeda halo and how that absorption changes in different regions. The immense Andromeda halo is made of very rarified and ionized gas that doesn’t emit radiation that is easily detectable. Therefore, tracing the absorption of light coming from a background source is a better way to probe this material. ...

Project AMIGA: The Circumgalactic Medium of Andromeda ~ Nicolas Lehner et al
viewtopic.php?t=34754
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

BDanielMayfield
Don't bring me down
Posts: 2490
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: East Idaho

Re: NASA/STScI: Hubble Maps Giant Halo Around Andromeda Galaxy

Post by BDanielMayfield » Thu Aug 27, 2020 10:57 pm

This means that Andromeda’s halo is already bumping into the halo of our own galaxy.
Hang on y'all. The "collision" has already begun.
Just as zero is not equal to infinity, everything coming from nothing is illogical.

John Done
Ensign
Posts: 18
Joined: Mon Aug 31, 2020 8:12 am

Re: NASA/STScI: Hubble Maps Giant Halo Around Andromeda Galaxy

Post by John Done » Mon Aug 31, 2020 9:31 am

Since Andromeda galaxy is closer to our Milky Way than any other galaxies, I believe that studying a halo surrounding the Andromeda galaxy allows us to better understand the structure of Milky Way own gas cloud cause it is much more difficult to see it than a halo of a neighbour as we ourselves located in this cloud.