Andromeda's halo is gargantuan. Extending for at least 2 million light years, if we could see in our night sky it would be 100 times the diameter of the Moon or 50 degrees across!


The merger of the Milky Way and Andromeda galaxy won't happen for another 4 billion years, but the recent discovery of a massive halo of hot gas around Andromeda may mean our galaxies are already touching. University of Notre Dame astrophysicist Nicholas Lehner led a team of scientists using the Hubble Space Telescope to identify an enormous halo of hot, ionized gas at least 2 million light years in diameter surrounding the galaxy.

The Andromeda Galaxy is the largest member of a ragtag collection of some 54 galaxies, including the Milky Way, called the Local Group. With a trillion stars — twice as many as the Milky Way — it shines 25% brighter and can easily be seen with the naked eye from suburban and rural skies.

Six examples of quasars photographed with the Hubble. Quasars are distant, brilliant sources of light, believed to occur when a massive black hole in the center of a galaxy feeds on gas and stars. As the black hole consumes the material, it emits intense radiation, which is then detected as a quasar. Lehner and team measured Andromeda’s halo by studying how its gas affected the light from 18 different quasars.

Think about this for a moment. If the halo extends at least a million light years in our direction, our two galaxies are MUCH closer to touching that previously thought. Granted, we're only talking halo interactions at first, but the two may be mingling molecules even now if our galaxy is similarly cocooned.

Lehner describes halos as the "gaseous atmospheres of galaxies". Despite its enormous size, Andromeda's nimbus is virtually invisible. To find and study the halo, the team sought out quasars, distant star-like objects that radiate tremendous amounts of energy as matter funnels into the supermassive black holes in their cores. The brightest quasar, 3C273 in Virgo, can be seen in a 6-inch telescope! Their brilliant, pinpoint nature make them perfect probes.

o detect Andromeda’s halo, Lehner and team studied how the light of 18 quasars (five shown here) was absorbed by the galaxy’s gas.

"As the light from the quasars travels toward Hubble, the halo's gas will absorb some of that light and make the quasar appear a little darker in just a very small wavelength range," said J. Christopher Howk , associate professor of physics at Notre Dame and co-investigator. "By measuring the dip in brightness, we can tell how much halo gas from M31 there is between us and that quasar."

Astronomers have observed halos around 44 other galaxies but never one as massive as Andromeda where so many quasars are available to clearly define its extent. The previous 44 were all extremely distant galaxies, with only a single quasar or data point to determine halo size and structure.

Andromeda's close and huge with lots of quasars peppering its periphery. The team drew from about five years' worth of observations of archived Hubble data to find many of the 18 objects needed for a good sample.

This illustration shows a stage in the predicted merger between our Milky Way galaxy and the neighboring Andromeda galaxy, as it will unfold over the next several billion years. In this image, representing Earth’s night sky in 3.75 billion years, Andromeda (left) fills the field of view and begins to distort the Milky Way with tidal pull.

The halo is estimated to contain half the mass of the stars in the Andromeda galaxy itself, in the form of a hot, diffuse gas. Simulations suggest that it formed at the same time as the rest of the galaxy. Although mostly composed of ionized hydrogen — naked protons and electrons — Andromeda's aura is also rich in heavier elements, probably supplied by supernovae. They erupt within the visible galaxy and violently blow good stuff like iron, silicon, oxygen and other familiar elements far into space. Over Andromeda's lifetime, nearly half of all the heavy elements made by its stars have been expelled far beyond the galaxy's 200,000-light-year-diameter stellar disk.

You might wonder if galactic halos might account for some or much of the still-mysterious dark matter. Probably not. While dark matter still makes up the bulk of the solid material in the universe, astronomers have been trying to account for the lack of visible matter in galaxies as well. Halos now seem a likely contributor.

The next clear night you look up to spy Andromeda, know this: It's closer than you think!

might make it there one day
if we don't take are selfs out
or are taken out by are leaders

The universe will always win, just like in the past... nothing is forever, ask the dinosaurs about that... if mans greed is our undoing, it's not any different from a comet destroying the planet, or getting razed by an alien race... dead is dead...

I watched that Stephen Hawkin movie a few days ago.
The theory of everything.

Worth a watch I thought.

It's all happening sooner then i expected it to

Does that indicate the creatures from another planet that will reign havoc on earth will be from Andomeda?.... in scientific theory maybe that's a way when the worm hole opens up & makes a pathway linking earth to the other planet for those beings to get through to Earth....and they won't be in space ships or any high tech machines

Do you mean the Earth will diminish coz the universe will swallow it?

If yes then i've to agree coz earth will be destroyed in the end...it's like humans would have lived a very fast life on earth & they would be extinct....sad truth

yes, the sun is predicted to swell ans swallow the earth in about 6 billion years...

it could possibly happen sooner...maybe sooner not by the sun but other phenomena...a thousand years is all i give it....if humans are still about by then i wonder what life would be like & a few thousand years for earth.

Just the past century or so...so much has been achieved & upto date the human mind has almost accomplished each feat.....what could possibly be up for the next 100 or even 50 years.....

It seems the boy from Andromeda will finally visit Earth

lol, just think if we last half as long as the dinosaurs did, they were around for about 200 million years or so...we have maybe 200,000 so far...20,000 if we count somewhat "modern" history...

200 million years for the dinosaurs....that estimate always had me questioning If they were accurate....just curiosity

well, as long as we are questioning things, i've always wondered how it it would actually take all evidence of any past life to completely disappear... if there was an advanced civilization 3 billion years ago, would there be anything left of it to show it was there?

Bout time we had some excitement round here

there is evidence of the past yes....but i somehow can't agree it was millions & billions years ago.....maybe thousands is what i think...just my opinion

i'm not saying there was one, but if there was, how would we know? whats the time limit on everything they did/had would turn to dust?

there are pyramids that are 12,000 years old, and they think they have found evidence of processed uranium from millions of years ago in Africa... as far as we know, processed uranium is only a man made thing, not natural...

http://www.s8int.com/atomic2.html

here's another version:
http://gizmodo.com/there-s-a-naturally-occurring-nuclear-fission-reactor-i-1475445638

Not necessarily the end for mankind. We, if we wanted to develop the resources, have the ability to colonize other worlds. It might take multiple spaceships capable of traveling for hundreds of years, but we basically know how to do it.

This world will end life as we know it, probably with an asteroid or comet strike long before we are consumed by the expanding Sun. We all don't have to be on it when that happens.

Of great note is the instrumentation being developed to examine the planets on distant stars. If we found some likely candidate planets and maybe used a little terraforming, we could create another homeworld.

the earth has replenished itself after what, 6-7 ELE's that they know of? after the sun swallows it, it's gone... but yea, if we can live long enough as a race, that would be our only option... they say the Europa might be habitable during the red giant phase of the sun, but that would last only a few million years...