Astronomers measure weight of galaxies, expansion of universe

Jul 30, 2014

Astronomers at the University of British Columbia have collaborated with international researchers to calculate the precise mass of the Milky Way and Andromeda galaxies, dispelling the notion that the two galaxies have similar masses.

While it was previously thought that the two weighed the same because of their similar size and structure, researchers found that neighboring Andromeda is about twice as heavy as our own Milky Way.

"Most of the weight of these galaxies is present in the form of invisible ," says Yin-Zhe Ma, a postdoctoral fellow in the Department of Physics and Astronomy, adding that Andromeda has almost twice as much dark matter as the Milky Way.

"We don't know much about dark matter so this discovery means we'll get a chance to study it from within our own galaxy."

Ma and his colleagues were also able to measure the expansion of the universe by observing the motion of smaller "satellite galaxies" that orbit the Milky Way and Andromeda. Previous research used cosmic microwave radiation to measure the expansion of the universe from a great distance.

"It was surprising that we could see expansion happening from within our own local group of galaxies that is consistent with expansion on a universal scale," says Ma. "This is the first time we've captured evidence that cosmic expansion is taking place so close to us."

Researchers hope to model the dark matter in our galaxy to better understand the interaction between dark matter and gravity.

Background

Researchers built computer models to simulate the two galaxies as a dumbbell structure in an expanding universe. The model showed the movement of small satellite galaxies around the larger galaxies. They measured the speed, position and motion of these to infer the structure and mass of the Milky Way and Andromeda.

The study, a collaboration between the University of British Columbia, the University of Edinburgh, Carnegie Mellon University and NRC Herzberg Institute of Astrophysics, was published in Monthly Notices of the Royal Astronomical Society.

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Nashingun
1.4 / 5 (10) Jul 30, 2014
Now this sounds so ridiculous trying to measure the weight of the universe! lol
And what makes you think you got them right this time? The last episode of Higgs Physics it says the universe collapsed right after Big Bang... So where are we now, ow yes, how much the universe weighs! lol
antialias_physorg
4.6 / 5 (11) Jul 30, 2014
Painful to see 'weight' and 'mass' being thrown around like this in a scientific article (even if it's only written by a science jourmalist). They should know better than to confuse the two.
cantdrive85
1.9 / 5 (11) Jul 30, 2014
Painful to see 'weight' and 'mass' being thrown around like this in a scientific article (even if it's only written by a science jourmalist). They should know better than to confuse the two.

"Most of the weight of these galaxies is present in the form of invisible dark matter," says Yin-Zhe Ma, a postdoctoral fellow in the Department of Physics and Astronomy,

It's not just the journalist who is confused...
Hat1208
1.4 / 5 (9) Jul 30, 2014
Researchers built computer models to simulate the two galaxies as a dumbbell structure in an expanding universe. The model showed the movement of small satellite galaxies around the larger galaxies. They measured the speed, position and motion of these satellite galaxies to >>>>>>infer<<<<<< the structure and mass of the Milky Way and Andromeda.

Could we not also infer dense aether, plasma universe and neutron repulsion?
Scroofinator
2 / 5 (4) Jul 30, 2014
researchers found that neighboring Andromeda is about twice as heavy as our own Milky Way.


How do they "find" this out? Do they do a spectrum analysis to see what elements comprise the galaxy?
Urgelt
5 / 5 (5) Jul 30, 2014
Scroofinator wrote, "How do they "find" this out? Do they do a spectrum analysis to see what elements comprise the galaxy?"

The article didn't bother to tell us, but I think what the authors did can be summed up as a 'gravitational analysis.' This isn't new; what's new is the precision the authors are claiming for their measurements.

Basically, they study movement - like the rate at which galaxies rotate and how they dances around with other nearby galaxies. Knowing distances and movements, they can use math to back into how much gravity is affecting each object.

Gravity implies mass. The more precisely they can nail down distances and movements, the more precisely they can estimate the masses in the objects.

This species of analysis doesn't reveal what, exactly, is contributing gravitational effects. It sheds no light (pun not intended) on the nature of 'dark matter.'
Mimath224
5 / 5 (2) Jul 30, 2014
Another point I wondered about is similar to the border of Solar System and interstellar space. Just how far form a galaxy center does its influence go? At what point does galactic space become intergalactic space?
TechnoCreed
4.6 / 5 (10) Jul 31, 2014
How do they "find" this out? Do they do a spectrum analysis to see what elements comprise the galaxy?
Basically, they study movement - like the rate at which galaxies rotate and how they dances around with other nearby galaxies. Knowing distances and movements, they can use math to back into how much gravity is affecting each object.
Another point I wondered about is similar to the border of Solar System and interstellar space. Just how far form a galaxy center does its influence go? At what point does galactic space become intergalactic space?
Hey! What is the matter with all the people here? Does anyone understand that reading an article on Phys.Org is like reading the back cover of a book? If this article intrigues you or brings up interrogations, find the paper and read it. Speculation is just intellectual laziness. http://mnras.oxfo...c724bbb3
Arties
Jul 31, 2014
This comment has been removed by a moderator.
TechnoCreed
4.5 / 5 (8) Jul 31, 2014
OK - so we can say, the weight of Milky Way remains the same all the time, only human stupidity fluctuates.
My god Zephir all the time you waste here. When will you understand that people here do not give a damn about what you write and, just like me, they just scoll to the next comment.
verkle
1.4 / 5 (9) Jul 31, 2014
It is not scientifically correct to say that they men were measuring the mass of these galaxies. They were only looking at movements and perceived distances. Most of what they say is mass is actually something never seen or measured, and likely does not exist. This should be clarified in the article, or else it is not truthful.
TechnoCreed
5 / 5 (5) Jul 31, 2014
@verkle
Why do you keep reading articles on Phys.Org if all those articles bring you so much frustrations?
Scroofinator
2 / 5 (4) Jul 31, 2014
So we're not allowed to ask questions anymore Techno?
aroc91
5 / 5 (5) Jul 31, 2014
Most of what they say is mass is actually something never seen or measured, and likely does not exist.


That's an extremely ironic statement coming from you.
TechnoCreed
4.4 / 5 (7) Jul 31, 2014
So we're not allowed to ask questions anymore Techno?
Questions are very legit, that is not the problem. What you need to be concerned about is the quality of the answer you get. On a given study the best answer you will have is from the source, so why not interrogate the paper first? If you opened the link I provided and gave it a serious read, I am pretty sure you got the answer to your interrogation and with much more details that anyone else can give you.
TheGhostofOtto1923
1 / 5 (2) Jul 31, 2014
Painful to see 'weight' and 'mass' being thrown around like this in a scientific article (even if it's only written by a science jourmalist). They should know better than to confuse the two.
Krauss talks about weighing the universe in this 2014 vid @11.00
https://www.youtu...eezmF62k

-So it appears it is a convention you were not aware of.
lengould100
1 / 5 (4) Jul 31, 2014
Once again people who should know better refer to "dark matter" as if they actually know anything about it. A term which is simply used as a synonym for "we don't know what might be causing the effect" to explain an effect which is more rationally explainable with a modification to out formulae of how gravity operates should be less certain about what it describes.
IMP-9
3.9 / 5 (7) Jul 31, 2014
which is more rationally explainable with a modification to out formulae of how gravity operates


Is it more rational? No. When the problems arose about the missing mass there were two potential problems, a) our models of what made up galaxies and b) or knowledge of gravity. It is not any more rational to assume either is flawed of the bat. But then there's practice. We've been able to more or less fix most of these problems with cold dark matter, assuming our knowledge of gravity is correct. We have not been able to solve them by attempting to fix gravity, despite a lot of effort. Neither is more rational but dark matter is the stronger model so far. That could change but to do so we need to explore the model in all it's gruesome detail to see where it fails.
DeliriousNeuron
1 / 5 (7) Aug 02, 2014
which is more rationally explainable with a modification to out formulae of how gravity operates


Is it more rational? No. When the problems arose about the missing mass there were two potential problems, a) our models of what made up galaxies and b) or knowledge of gravity. It is not any more rational to assume either is flawed of the bat. But then there's practice. We've been able to more or less fix most of these problems with cold dark matter, assuming our knowledge of gravity is correct. We have not been able to solve them by attempting to fix gravity, despite a lot of effort. Neither is more rational but dark matter is the stronger model so far. That could change but to do so we need to explore the model in all it's gruesome detail to see where it fails.

LOL! "Dark matter" IS a joke!
Reg Mundy
1 / 5 (8) Aug 03, 2014
which is more rationally explainable with a modification to out formulae of how gravity operates


Is it more rational? No. When the problems arose about the missing mass there were two potential problems, a) our models of what made up galaxies and b) or knowledge of gravity. It is not any more rational to assume either is flawed of the bat. But then there's practice. We've been able to more or less fix most of these problems with cold dark matter, assuming our knowledge of gravity is correct. We have not been able to solve them by attempting to fix gravity, despite a lot of effort. Neither is more rational but dark matter is the stronger model so far. That could change but to do so we need to explore the model in all it's gruesome detail to see where it fails.

Dark matter exists because otherwise gravity does not. Or perhaps gravity does not exist unless Dark Matter does? There ain't no gravity, there is no proven evidence for it!

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