Hubble Finds Giant Halo Around the Andromeda Galaxy

May 7, 2015, ESA/Hubble Information Centre
This diagram shows how scientists determined the size of the halo of the Andromeda galaxy. Because the gas in the halo is dark, the team measured it by using the light from quasars, the very distant bright cores of active galaxies powered by black holes. They observed the quasars' light as it traveled through the intervening gas. The halo's gas absorbed some of that light and made the quasar appear darker in a very small wavelength range. By measuring the tiny dip in brightness at that specific range, scientists could tell how much gas is between us and each quasar. Some quasars showed no dip in brightness, and this helped define the size of the halo. Credit: NASA, ESA, and A. Feild (STScI)

Scientists using NASA's Hubble Space Telescope have discovered that the immense halo of gas enveloping the Andromeda galaxy, our nearest massive galactic neighbor, is about six times larger and 1,000 times more massive than previously measured. The dark, nearly invisible halo stretches about a million light-years from its host galaxy, halfway to our own Milky Way galaxy. This finding promises to tell astronomers more about the evolution and structure of majestic giant spirals, one of the most common types of galaxies in the universe.

"Halos are the gaseous atmospheres of galaxies. The properties of these gaseous halos control the rate at which stars form in galaxies according to models of galaxy formation," explained the lead investigator, Nicolas Lehner of the University of Notre Dame, Indiana. The gargantuan halo is estimated to contain half the mass of the stars in the Andromeda galaxy itself, in the form of a hot, diffuse gas. If it could be viewed with the naked eye, the halo would be 100 times the diameter of the full Moon in the sky. This is equivalent to the patch of sky covered by two basketballs held at arm's length.

The Andromeda galaxy, also known as M31, lies 2.5 million light-years away and looks like a faint spindle, about 6 times the diameter of the full Moon. It is considered a near-twin to the Milky Way galaxy.

Because the gas in Andromeda's halo is dark, the team looked at bright background objects through the gas and observed how the light changed. This is a bit like looking at a glowing light at the bottom of a pool at night. The ideal background "lights" for such a study are quasars, which are very distant bright cores of active galaxies powered by black holes. The team used 18 quasars residing far behind Andromeda to probe how material is distributed well beyond the visible disk of the galaxy. Their findings were published in the May 10, 2015, edition of The Astrophysical Journal.

Earlier research from Hubble's Cosmic Origins Spectrograph (COS)-Halos program studied 44 distant galaxies and found halos like Andromeda's, but never before has such a massive halo been seen in a neighboring galaxy. Because the previously studied galaxies were much farther away, they appeared much smaller on the sky. Only one quasar could be detected behind each faraway galaxy, providing only one light anchor point to map their halo size and structure. With its close proximity to Earth and its correspondingly large footprint on the sky, Andromeda provides a far more extensive sampling of a lot of background quasars.

"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," explains co-investigator J. Christopher Howk, also of Notre Dame. "By measuring the dip in brightness in that range, we can tell how much halo gas from Andromeda there is between us and that quasar."

The scientists used Hubble's unique capability to study the ultraviolet light from the quasars. Ultraviolet light is absorbed by Earth's atmosphere, which makes it difficult to observe with a ground-based telescope. The team drew from about 5 years' worth of observations stored in the Hubble data archive to conduct this research. Many previous Hubble campaigns have used quasars to study gas much farther away than—but in the general direction of—Andromeda, so a treasure trove of data already existed.

But where did the giant halo come from? Large-scale simulations of galaxies suggest that the halo formed at the same time as the rest of Andromeda. The team also determined that it is enriched in elements much heavier than hydrogen and helium, and the only way to get these heavy elements is from exploding stars called supernovae. The supernovae erupt in Andromeda's star-filled disk and violently blow these heavier elements far out 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.

What does this mean for our own galaxy? Because we live inside the Milky Way, scientists cannot determine whether or not such an equally massive and extended halo exists around our galaxy. It's a case of not being able to see the forest for the trees. If the Milky Way does possess a similarly huge , the two galaxies' halos may be nearly touching already and quiescently merging long before the two massive galaxies collide. Hubble observations indicate that the Andromeda and Milky Way will merge to form a beginning about 4 billion years from now.

Explore further: Study of Andromeda's stellar disk indicates more violent history than Milky Way

More information: Astrophysical Journal, iopscience.iop.org/0004-637X/8 … 04-637X_804_2_79.pdf

Related Stories

Dark matter guides growth of supermassive black holes

February 18, 2015

Every massive galaxy has a black hole at its center, and the heftier the galaxy, the bigger its black hole. But why are the two related? After all, the black hole is millions of times smaller and less massive than its home ...

Four unusual views of the Andromeda Galaxy

July 21, 2011

The Andromeda Galaxy is revealed in unprecedented detail in four archive observations from the NASA/ESA Hubble Space Telescope. They show stars and structure in the galaxy’s disc, the halo of stars that surrounds it, ...

Could the Milky Way become a quasar?

February 27, 2015

A quasar is what you get when a supermassive black hole is actively feeding on material at the core of a galaxy. The region around the black hole gets really hot and blasts out radiation that we can see billions of light-years ...

Recommended for you

Hubble weighs in on mass of three million billion suns

January 16, 2018

In 2014, astronomers using the NASA/ESA Hubble Space Telescope found that this enormous galaxy cluster contains the mass of a staggering three million billion suns—so it's little wonder that it has earned the nickname of ...

How massive can neutron stars be?

January 16, 2018

Astrophysicists at Goethe University Frankfurt set a new limit for the maximum mass of neutron stars: They cannot exceed 2.16 solar masses.

Black hole spin cranks-up radio volume

January 12, 2018

Statistical analysis of supermassive black holes suggests that the spin of the black hole may play a role in the generation of powerful high-speed jets blasting radio waves and other radiation across the universe.

31 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

abecedarian
4.2 / 5 (11) May 07, 2015
Well I guess there's some of the U's missing mass, and a tiny little chunk of DM accounted for?
Returners
2.9 / 5 (11) May 07, 2015
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.


I feel vindicated knowing this is how I said star dust should behave.

Yeah, so much for that "dark matter" stuff. This is brilliant.
Nik_2213
1.8 / 5 (8) May 07, 2015
Yet another chunk of 'missing matter' found ??

Surely, all this mass on the galaxy fringes will alter the 'distribution' curve and reduce the need for arcane 'Dark Matter' and/or non-Newtonian gravity ??
Steve 200mph Cruiz
4.4 / 5 (14) May 07, 2015
Returners,
They measured the mass, it is still much too small and dark matter still needs to exist.

Dark matter really is not that weird of an idea. In the standard model, a few particles don't interact with certain forces directly. Something not interacting electromagneticly is far from being the strangest thing in the universe.
Mordechai Mineakoitzen
4 / 5 (4) May 07, 2015
If the halo is half the mass of Andromeda's stars, and yet people are going to say that accounts for nothing really, that dark matter still has to be, then how much mass _in the form of dark matter and as a proportion of the galaxy's mass_ is theoretically required outside the galaxy to make those stars rotate at the speeds they say they shouldn't be going?
Benni
2 / 5 (12) May 07, 2015
They measured the mass, it is still much too small and dark matter still needs to exist.
.......they measured the mass alright, but you forgot to read their conclusion about the "mass" of the halo: "The gargantuan halo is estimated to contain half the mass of the stars in the Andromeda galaxy itself, in the form of a hot, diffuse gas."

Dark matter really is not that weird of an idea.
Anything you claim to be "settled science" but which you have never proven to exist is a really weird idea, you just don't think so because you have never studied the Einstein Field Equations for gravity contained within General Relativity.

Paulw789
2.4 / 5 (7) May 07, 2015
If you ever saw an animation of how galaxies form, with hundreds of satellite galaxies merging very slowly over time, one would see that today's short-term view of a galaxy's rotation as mis-informed. None of the stars are truely in a stable circular or even eliptical orbit. After 10 billion years of slowly consolidating, it only looks like it is.

Now add-in the huge amount of matter surrounding the galaxy in a halo, one can do away with the dark matter concept.
Steve 200mph Cruiz
3.9 / 5 (16) May 07, 2015
Benni,
Check your math Einstein.

Also a hypothesis is only weird before it becomes a theory, then it becomes obvious.
Benni
1.9 / 5 (9) May 07, 2015
If you ever saw an animation of how galaxies form, with hundreds of satellite galaxies merging very slowly over time, one would see that today's short-term view of a galaxy's rotation as mis-informed. None of the stars are truely in a stable circular or even eliptical orbit. After 10 billion years of slowly consolidating, it only looks like it is.

Now add-in the huge amount of matter surrounding the galaxy in a halo, one can do away with the dark matter concept.
................before you post, VietVet thinks you should clear your science with him first, he imagines himself to be one of the resident experts who can follow every Differential Equation in Einstein'd GR :)
MandoZink
4.6 / 5 (11) May 07, 2015
"Earlier research from Hubble's Cosmic Origins Spectrograph (COS)-Halos program studied 44 distant galaxies and found halos like Andromeda's, but never before has such a massive halo been seen in a neighboring galaxy."

If you understand the function of the Cosmic Origins Spectrograph you would know it is to study the spectral absorption features of the interstellar and intergalactic medium around galaxies. This halo of dark baryonic matter has been known to exist, and has been accounted for in surveys of the universe's mass inventory. It is NOT dark matter. Dark baryonic matter requires absorption instruments such as COS to readily detect. We have already been studying it elsewhere in distant galaxies, and now we have observed the same in Andromeda. It does NOT change our accounting of dark matter, the effects of which we also can see.

So no upset in the currently understood balance of matter. The only surprise here is that we had not yet applied this instrument to Andromeda.
Returners
3.7 / 5 (6) May 08, 2015
Mandozonk:
The article says it's 6 times larger and a 1000 times more massive than previous "measurements".

Considering they are now saying it represents half the mass of all the stars in the galaxy, that pretty much means they previously missed half the mass of the galaxy in previous measurements.

I think that's pretty damned significant.
cdt
4.8 / 5 (16) May 08, 2015
As I see it, people positing DM to account for galaxy rotation speeds have claimed there needs to be a halo with a mass on the order of 5 times the mass of the measurable stars and gas in the galaxy. If we increase the mass of the galaxy by adding a measurable-matter halo that's 0.5 times the previously measurable stars and gas we reduce the amount of DM needed by a full 10 percent. That's a significant reduction, but it doesn't even come close to eliminating the need for DM.
Benni
1.6 / 5 (7) May 08, 2015
As I see it, people positing DM to account for galaxy rotation speeds have claimed there needs to be a halo with a mass on the order of 5 times the mass of the measurable stars and gas in the galaxy
Like you say, it's as you see it, but you don't know how to calculate the gravity all this newly discovered mass creates.

If we increase the mass of the galaxy by adding a measurable-matter halo that's 0.5 times the previously measurable stars and gas we reduce the amount of DM needed by a full 10 percent. That's a significant reduction, but it doesn't even come close to eliminating the need for DM.
Wow, where'd you come up with that math?

You do not comprehend the Einstein Field Equations for gravity in General Relativity, but that is not the testable/observable scientific method, and this goes for all your 5 Star voting allies whose mindset for testable/observed scientific methodology find scientific methodology as incomprehensible as you do.
El_Nose
5 / 5 (6) May 08, 2015
@abecedarian

@Nik_2213

@Paulw789

This does nothing to DM and DM theory. If astronomers got the mass of everything visible in the universe wrong by a factor of 3x we still have a HUGE mass issue. About 5 or 6 years ago we figured out that the estimates for red dwarfs and brown dwarfs in any given galaxy were off by at least 4-5 magnitudes thats 1000x-10000x and it did nothing to the issues in the mass missing from the universe.

Look we haven't proven DM -- but the missing mass issue is so mind bogglingly large to dismiss DM as a fantasy is to really miss the larger picture of where is the mass.

Nothing explains it... and I am not talking about small changes or tripling numbers

-- if every galaxy we can see we messed up in its mass bay a factor of 10 and it had a twin right next to it that was the same mass and just so cold we could not see it - we would still be missing 10% of the mass needed to make all our other observations make sense.
rossim22
1.8 / 5 (5) May 08, 2015
These galactic halos, and temperature gradients within them, can account for the lensing observations without requiring the abstract (and untestable) bending of space-time.
OdinsAcolyte
3 / 5 (3) May 08, 2015
Our galaxies must be about touching if not already so. Their atmospheres at any rate. There may be some infant stars already forming between us. It would be marvelous to see. Too bad we came so soon to the universe. Humanity shall be so long gone before the pretty fireworks are visible.
denglish
3 / 5 (4) May 08, 2015
if every galaxy we can see we messed up in its mass bay a factor of 10 and it had a twin right next to it that was the same mass and just so cold we could not see it - we would still be missing 10% of the mass needed to make all our other observations make sense.

We have a winner! 5/5
cdt
4.4 / 5 (7) May 08, 2015
If we increase the mass of the galaxy by adding a measurable-matter halo that's 0.5 times the previously measurable stars and gas we reduce the amount of DM needed by a full 10 percent. That's a significant reduction, but it doesn't even come close to eliminating the need for DM.
Wow, where'd you come up with that math?

Well, it was fairly straightforward Newtonian stuff. No it wasn't calculated based on relativity and so is certain to be no more than an approximation, but since we're not dealing with extreme accelerations or speeds the approximation is close enough. Until you get up past a third the speed of light relativity has only small effects on calculations. Important ones if you're a physicist interested in getting things to be correct down to the 10th decimal point, but relatively unimportant if you're happy being within a couple of percent, which I happen to be. Go ahead and show me the calculations that show I'm wrong and I'll happily change that stance.
Benni
1.5 / 5 (8) May 09, 2015
where'd you come up with that math?


it was fairly straightforward Newtonian stuff
.....which contradicts this next.......
No it wasn't calculated based on relativity
General Relativity is based on Newtonian gravity, but of course how would you be expected to k now this based on this next statement......
and so is certain to be no more than an approximation
Nothing like finding a way to exempt yourself from Einstein Field Equations in GR.

Until you get up past a third the speed of light relativity has only small effects on calculations
The newly discovered mass has nothing at all to do with the Lorentz Factor.

Go ahead and show me the calculations that show I'm wrong and I'll happily change that stance.
You don't have any calculations, you don't even know the appropriate applications for applying the Lorentz Factor......and you expect this Electrical/Nuclear Engineer to believe you've seen the inside of a college physics classroom?
cdt
4.2 / 5 (5) May 09, 2015
Benni, I'm guessing you're just trolling here, and so not deserving of a response, but just in case I'm wrong here goes. You make a simple logical error. I claim I didn't base my calculations on relativity. You claim relativity is based on Newtonian gravity, and therefore that I have contradicted myself. There is no contradiction. If Newtonian gravity were based on relativity, well then yes what I said would have been contradictory, but history went in the other direction.

I made my reasoning fairly clear in my first post. I'm not defending the science of dark matter, just pointing out that the amount that has been claimed to be needed will indeed be less given the increase of non-dark matter that this article reports on. The math is extremely simple: the effects on rotational speed come from gravity. It doesn't matter what that gravity comes from -- as far as we know all gravity is the same. Swapping out 10% of your DM and putting in a gravitationally equivalent ...
cdt
3.7 / 5 (3) May 09, 2015
... amount of regular matter makes no difference on the total gravity coming from the halo. If GR calculations were needed for the original DM estimates, then they should apply in exactly the same way with 10% of the DM swapped. Unless you are telling me that GR works differently for normal matter and DM when it comes to gravity. If that's the case then I'd take that belief to require some justification.

I'll be the first to admit that I never studied general relativity, and never implied that I have. Show me that calculating the effect of this discovery on the amount of DM needed to explain galactic rotation requires general relativity and explain to me why and I'll be happy to either look into it or retract what I've said. Or both. (I have no doubt that GR plays a role in figuring out how much DM is needed, but once you have that result, what role does GR further play if the needed gravity comes from some other source?)
Mike_Massen
4.3 / 5 (6) May 09, 2015
Benni claimed
...you don't even know the appropriate applications for applying the Lorentz Factor......and you expect this Electrical/Nuclear Engineer to believe you've seen the inside of a college physics classroom?
Pardon ?

Benni, haven't you realized its immensely naive to even try to make a claim what someone cannot do, its the most immature attempting at goading a confrontation, why would anyone who actually HAD achieved a uni degree in anything definitive such as Science EVER make such a complete ASS of themselves with gutter talk consistent ONLY with a mere high school student ?

Benni, you have often claimed to be an "Electrical Engineer", then later a "Nuclear Engineer" & especially so WHEN challenged, the server logs confirm the frequency of your claims re so many selfish egotistical oddities failing at dialectic but, no useful maths, no smart delivery or ANY education IN those DE's you claim to solve

Benni, prove where & when you graduated uni ?
denglish
5 / 5 (4) May 09, 2015
You don't have any calculations, you don't even know the appropriate applications for applying the Lorentz Factor......and you expect this Electrical/Nuclear Engineer to believe you've seen the inside of a college physics classroom

Troll.

I want to know what college you went to also.
Mike_Massen
3.7 / 5 (6) May 09, 2015
Benni claimed
.. General Relativity is based on Newtonian gravity, but of course how would you be expected to k now this based on this next statement..
No, that's immense distortion, Newton's work & Einsteins, you are vague & especially so as a narrow egotistical pedant trying to worm position of superiority, doesn't help you, it does confirm you could NOT have studied Electrical or Nuclear Engineering at university OR the educational institute at which you did, had minimal prerequisite requirements for Engineering discipline

Benni, you appear with only superficial understanding of General Relativity (GR) & have shown before you don't understand Special Relativity (SR) by applying Lorentz to E=mc^2 incorrectly in respect of clear cut differences between inertial & non-inertial reference frames

Eg. Newton's gravity referred here, cdt is correct - Newton's works, & GR adds precision re motion
https://en.wikipe...lativity

Benni, uni honestly ?
liquidspacetime
2.3 / 5 (3) May 09, 2015
Physicists are starting to realize the notions of dark matter and the dark matter particle are incorrect. They are referring to the mass which fills 'empty' space as the 'dark mass' in order to distinguish it from the baggage associated with dark matter.

'Dark Energy/Dark Mass: The Slient Truth'
https://tienzengo...t-truth/

"That is, all that we are certain about [is] the dark mass, not dark matter, let alone to say about the dark 'particle'."

Particles of matter move through and displace the dark mass, including 'particles' as large as galaxies and galaxy clusters.

The Milky Way moves through and curves spacetime.

The Milky Way moves through and displaces the dark mass.

The Milky Way's halo is the state of displacement of the dark mass.

The state of displacement of the dark mass is curved spacetime.

The Milky Way's halo is curved spacetime
liquidspacetime
1 / 5 (2) May 09, 2015
'Hubble Scientists Map a Massive Halo of Gas Around Andromeda Galaxy'
http://www.nbcnew...-n355521

""It's a very massive halo, but it's still less than a tenth the mass of the dark matter," he told NBC News."

Physicists are starting to realize the notions of dark matter and the dark matter particle are incorrect.

'Dark Energy/Dark Mass: The Slient Truth'
https://tienzengo...t-truth/

"That is, all that we are certain about [is] the dark mass, not dark matter, let alone to say about the dark 'particle'."

Particles of matter move through and displace the dark mass, including 'particles' as large as galaxies and galaxy clusters.

The Andromeda Galaxy is moving through and displacing the dark mass.

The statell of displacement of the dark mass is curved spacetime.
derek_dwyer
1 / 5 (1) May 09, 2015
So how do astronomers deal with the halo around the milky way and the way it would interfere with star brightness?
Nnnrj
not rated yet May 10, 2015
Questions, questions, questions generating more questions
EnsignFlandry
5 / 5 (2) May 10, 2015
There isn't enough mass in the halo to account for dark matter.
Astrophysicists already know that dust can affect their calculations of star and galaxy brightness, and thus, distance. They actually are as smart as some of the posters here.
liquidspacetime
2 / 5 (4) May 10, 2015
They're not smart enough to understand the Milky Way is moving through and displacing the mass that fills 'empty' space.

They're not smart enough to understand the state of displacement of the mass which fills empty space *is* curved spacetime.
Tuxford
1 / 5 (2) May 23, 2015
Physics is stuck. This dark mass is undetectable with the larger instruments of our universe. It's effects can be observed, but it cannot be detected. Like trying to isolate a tiny ball bearing from a pile while using only a sledge hammer. That is the state of physics. All we have available is the hammer, while trying to isolate a grain of sand. Sub-atomic particles are the hammers.

So if it can't be tested, it can't exist. Silly rules of physics. So the science is dead, unless it changes it's rules.

In SubQuantum Kinectics, matter forms from the 'dark mass' more readily when nearby higher densities of matter, such as a big galaxy. Hence the halo forms slowly over time. And since the core is seeding the galaxy with outbursts, the halo gains metals eventually too. Just slowly. And so gas slowly forms in intergalactic space too.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.