The Andromeda galaxy's halo is even more massive than scientists expected, Hubble telescope reveals
Last edited Tue Sep 1, 2020, 02:04 AM - Edit history (2)
By Meghan Bartels 8 hours ago
An artist's depiction showing what the Andromeda Galaxy halo would look like in the sky if our
eyes could see it.
(Image: © NASA, ESA, J. DePasquale and E. Wheatley (STScI), and Z. Levay)
Galactic halos are both more massive and more complicated than scientists realized, according to new observations from the Hubble Space Telescope.
The venerable telescope turned its sights on the neighboring Andromeda galaxy using dozens of different quasars to map the galactic halo. Andromeda, more formally known as M31, is a spiral-shaped galaxy about the same size of the Milky Way galaxy we live in, with about 1 trillion stars. Cosmically, it's right next door, just 2.5 million light-years away, which means that Hubble can study its halo in unprecedented detail.
"This is truly a unique experiment because only with Andromeda do we have information on its halo along not only one or two sightlines, but over 40," lead researcher Nicolas Lehner, an astrophysicist at the University of Notre Dame in Indiana, said in a NASA statement. "This is groundbreaking for capturing the complexity of a galaxy halo beyond our own Milky Way."
Those sightlines are built by the active black holes that lie at the heart of galaxies on the opposite side of Andromeda. These objects, called quasars, produce lots of light and it's easier for scientists to study how gasses in the halo absorb some of that light than it is to study the halo itself. So Hubble turned its ultraviolet gaze to 43 different quasars beyond Andromeda and analyzed their light in order to map gaseous charged carbon, silicon and oxygen in the halo.
More:
https://www.space.com/andromeda-galaxy-halo-hubble-telescope-discovery.html
= new reply since forum marked as read
Some of the nearest objects appear smallest in the sky, while some of the most distant ones loom largest.
By Corey S. Powell
August 31, 2020 9:00 PM
The extended halo of the Andromeda Galaxy would fill a patch of sky more than 60 degrees wide if you could see it with your eyes. (Credit: NASA/ESA/J. DePasquale and E. Wheatley/ Z. Levay)
In about 4 billion years, the Andromeda Galaxy will collide with our galaxy, the Milky Way, unleashing a brilliant burst of star formation. This is not exactly breaking news (assuming anything that will happen billions of years in the future could be considered "news" of any kind). Astronomers have known about the impending collision for decades, many popular stories have discussed it, and a team working with the Hubble Space Telescope even put together pretty illustrations of what the impending conflagration will look like.
But there's an unexpected twist to the story.
Earlier this week, researchers working on a sky-mapping project called AMIGA reported that the early stages of the Andromeda-Milky Way collision will happen long before the main event. You don't have to wait 4 billion years to watch a galaxy smash-up. With a little vision enhancement you can see it happening right now...because the Andromeda-Milky Way collision has already begun.
The reason the collision is happening so soon is that the Andromeda Galaxy is much bigger than it appears. The galaxy's bright, starry disk is about 120,000 light years in diameter, making it slightly larger than the Milky Way. In recent years, deep studies of Andromeda using the giant Keck telescopes in Hawaii revealed an extended population of stars that stretched the galaxy's total diameter to about 200,000 light years. That's nothing compared to the latest study, however.
Nicolas Lehner of the University of Notre Dame and his colleagues determined that Andromeda's halo—its outer envelope of extremely thin, hot gas, kind of like a galactic atmosphere—keeps going up to 2 million light years away from its center. The AMIGA team also determined that the halo is divided into two layers, an inner one that is stirred by supernova explosions and an outer one that is much smoother and calmer. In future eons, gas from the halo will slowly rain down onto Andromeda, helping to form future generations of stars.
More:
https://www.discovermagazine.com/the-sciences/things-in-the-universe-are-bigger-than-they-appear
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And, thanks again to our human heroes on the Shuttles that patched her up.......
