It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Thank you.
Some features of ATS will be disabled while you continue to use an ad-blocker.
What's in a galaxy? A lot, apparently. We now have the most accurate measurements of the size and mass of the Milky Way ever calculated, and it's turned out to be more massive than we thought.
How massive? Well, about 1.5 trillion Suns' worth of mass (solar masses), within a radius of around 129,000 light-years.
That's over twice as much as previous estimates - according to a 2016 study, the Milky Way was estimated at around 700 billion solar masses.
The Latest Calculation of Milky Way's Mass Just Changed What We Know About Our Galaxy
Our galaxy is a whole lot bigger than it looks. New work finds that the Milky Way stretches nearly 2 million light-years across, more than 15 times wider than its luminous spiral disk. The number could lead to a better estimate of how massive the galaxy is and how many other galaxies orbit it.
Astronomers have long known that the brightest part of the Milky Way, the pancake-shaped disk of stars that houses the sun, is some 120,000 light-years across (SN: 8/1/19). Beyond this stellar disk is a disk of gas. A vast halo of dark matter, presumably full of invisible particles, engulfs both disks and stretches far beyond them (SN: 10/25/16). But because the dark halo emits no light, its diameter is hard to measure.
Now, Alis Deason, an astrophysicist at Durham University in England, and her colleagues have used nearby galaxies to locate the Milky Way’s edge. The precise diameter is 1.9 million light-years, give or take 0.4 million light-years, the team reports February 21 in a paper posted at arXiv.org.
Astronomers have found the edge of the Milky Way at last
You see, the best way to measure galactic mass is by using the stars and globular clusters found distributed far away from the galactic center or disk: in the galaxy's halo. Doing this for a galaxy like Andromeda is fascinating and educational, teaching us that the massive halo extends for approximately a million light-years in all directions, and contains a large amount of mass in this halo as well, in terms of both gas and dark matter. Although there are large uncertainties, the total mass estimates of Andromeda range from about 800 billion solar masses up to 1.5 trillion solar masses. These estimates are so different because they're arrived at by using different techniques, which poses an interesting puzzle at present.
By measuring the motions of globular clusters within our own Milky Way, however, we don't have to rely only on the radial (along our line-of-sight) measurement, but can obtain transverse (moving perpendicular to our line-of-sight) motions as well. A combination of new data from the Gaia mission and the Hubble Space Telescope has given us a total of 46 globular clusters with distances reaching as far as 130,000 light-years from Earth, and was able to pin down the Milky Way's mass more accurately than ever before.
The result?
The Gaia data alone indicates a mass of 1.3 trillion solar masses, while the combined Gaia/Hubble data (where Hubble captures the more distant globular clusters) yields a mass of 1.54 trillion solar masses, with an uncertainty of less than 100 billion solar masses.
Could The Milky Way Be More Massive Than Andromeda?
If you want to know the mass and size of the earth, you can get simple answers and they will have reasonable error bars.
originally posted by: delbertlarson
I'm not looking for tomes, but rather some simple answers, although I know the answers may not be known right now.
So do you really want to know the virial mass? Or the static mass? If you're interested in dark matter, should the perhaps 150 satellite galaxies of the Milky Way be considered? We've discovered about 50 so far and this paper suggests 100 more may be waiting to be discovered for about 150 of them in total.
We question the importance of the role of formal virial quantities currently ubiquitously used in descriptions, models and relations that involve properties of dark matter structures. Concepts and relations basedon pseudo-evolving formal virial quantities do not properly reflect the actual evolution of dark matter halos and lead to an inaccurate picture of the physical evolution of our universe.
Just like we orbit the sun and the moon orbits us, the Milky Way has satellite galaxies with their own satellites. Drawing from data on those galactic neighbors, a new model suggests the Milky Way should have an additional 100 or so very faint satellite galaxies awaiting discovery...
Astrophysicists believe that dark matter is responsible for much of that structure, and now researchers at the Department of Energy's SLAC National Accelerator Laboratory and the Dark Energy Survey have drawn on observations of faint galaxies around the Milky Way to place tighter constraints on the connection between the size and structure of galaxies and the dark matter halos that surround them.
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.
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.
originally posted by: ChaoticOrder
Astronomers have found the edge of the Milky Way at last
Our galaxy is a whole lot bigger than it looks. New work finds that the Milky Way stretches nearly 2 million light-years across, more than 15 times wider than its luminous spiral disk. The number could lead to a better estimate of how massive the galaxy is and how many other galaxies orbit it.
What is the best estimate for the amount of dark matter in our galaxy?
originally posted by: delbertlarson
a reply to: 727Sky
In my aether model, dark matter comes about from a distortion of the aether itself. There is no particle associated with it.
Hopefully my reply to your OP question was of some help, but I'm not sure I can be of much help on your tension question. Instead of leaving you hanging without an answer, I'll mention some things I know about tension, realizing they may not be of much help but still some of it I find interesting and since I have worked with polymers a long time I find their properties in tension very interesting.
originally posted by: delbertlarson
The tension question, along with the OP questions, were the two areas that I wanted some advice on prior to submitting for peer review. I feel pretty comfortable with the rest of it.
Well if you want to be a hero to the cosmology community, what they really need is an answer to the problem of why more dark matter doesn't appear at the core of galaxies. In the other thread I think you mentioned your dark matter model would predict higher densities of dark matter at the core. It's not just your model which does that, but also simulations have predicted that using other models, which is a problem because they don't match observation which is that there doesn't seem to be as much dark matter at the core as simulations predict. It's sometimes referred to as the core-cusp problem and there's even a Wikipedia article about it.
By the way - your answer, Arbitrageur, does seem to support my model I believe. I was wondering why there wasn't evidence for quite a bit more dark matter far from galactic centers. My guess was that we hadn't found it yet. However, it appears that there may indeed be just such evidence.
originally posted by: delbertlarson
So this is a real simple concept: tension is an entity comprised of two back to back forces. There would of course be three Cartesian components of such entities in a solid. I did not see any mention of such a concept in the references you cited. If such a concept has been proposed I suspect it isn't widely known.
"serious feedback"
originally posted by: delbertlarson
Do you participate in some social media groups where discussions of my ideas might be welcome? Can you let me know what they are? If ATS is going away it would be good to have another outlet where ideas get some serious feedback. I see some here are going to Discord, but it was rather invasive as it would pop things up when I was working someplace else. I really like the forum here at ATS far better, as we can turn it off when we want to. Turning it off is something I wish we could do with all of the big tech - and only use it when we want to. A bygone era perhaps.
I can and plan to publish, but I am afraid almost no one reads. The problem is that everyone is writing and few are reading. It is a product of everyone chasing money through grants, with the publications being the "product" paid for by the government bodies.
Due to the speculative nature of the subject, not-yet-published papers uploaded to databases like ArXiv or presented at reputable conferences are also acceptable for discussion. (Note that references to such unreviewed sources remain unacceptable in the other subforums dedicated to more established areas of physics.)
This forum may not be used to propose new ideas or personal theories. All threads of this nature that are started in this forum will be removed by Mentors.
originally posted by: Arbitrageur
Well if you want to be a hero to the cosmology community, what they really need is an answer to the problem of why more dark matter doesn't appear at the core of galaxies.
I might be missing your point here but I thought the diagram showing the angles in this molecular model for tension shows in this case it's not always strictly "back to back" which to me implies angles of 180 degrees. These angles are not all 180 degrees in this model:
You may or may not get any reply, but there are numerous physicists on physicsforums.com. They seem to be pretty picky about what topics are discussed, and they have a list of "credible journals", which if a paper gets published in one of those, apparently it can be discussed there. They updated their list of "credible journals" last December, so if you get published in one of those you'd have a good forum to discuss your paper.
originally posted by: 727Sky
originally posted by: delbertlarson
a reply to: 727Sky
In my aether model, dark matter comes about from a distortion of the aether itself. There is no particle associated with it.
Well you may be correct for all the others with mucho money have shown nothing