A galaxy has been found with almost no dark matter! - Page 1
Forum section: electronics / general

author: BrianHG
author_rank: Super Contributor
timestamp: March 30, 2018, 08:48:12 pm
content: Amazing, but, true: We now know very well that there is invisible matter in most galaxies acceleration there outer star's orbit speed since we now found a galaxy where this invisible matter is missing and the outer star's orbit speeds are slower like they should be if said dark matter wasn't present.https://news.nationalgeographic.com/2018/03/dark-matter-galaxy-gravity-dragonfly-physics-space-science/https://futurism.com/df2-galaxy-no-dark-matter/

author: Rick Law
author_rank: Super Contributor
timestamp: March 30, 2018, 09:46:56 pm
content: I heard that on the radio last night. What a fascinating surprise! To have such a galaxy sized region of space devoid of dark matter is difficult given (one accepted explanation is) that real matter is formed as a result of dark matter.I've not heard any explanation yet, not even wild ones. But this is on my thought (ie:my speculation): Some have proposed that perhaps the reason why gravity is so much weaker than other forces (such as electromagnetic force) is that it may "leak" into other dimensions. If that is the case, we might have found where the other universe(s) are interfering with our space/dimensions around there.Or, (another thought) may be we simply do not understand how gravity should be evaluated yet... (ie: that gravity is proportional to m1m2/x2is missing some other components, components that when x exceeds a certain size, that became significant and causes g to increasing as X increases). In other words, dark matter really is just an shoe-horned explanation of missing components in the equation of gravity.Very interesting indeed. Hopefully, someone actually in the game will have some real and meaningful theory coming out soon.

author: ejeffrey
author_rank: Super Contributor
timestamp: March 31, 2018, 03:00:04 am
content: I wouldn't describe it as "real matter is formed as a result of dark matter". It's more like that as the universe expanded from a uniform mass and began clumping together into galactic clusters and galaxies, the dark matter drove the clumping (since there was more of it) and the baryonic / light matter sort of followed suit.One other clarification, I don't think this galaxy was close enough to measure the orbital velocity. The dark matter fraction was estimated by comparing the amount of light (and hence stars) to the total mass measured by gravitational lensing. It is inferred that the outer stars would be orbiting at the "slow" speed, but that isn't directly observed.Not much is known about the system yet, but there are some fairly mundane (by cosmological standards) explanations. One is that this galaxy was formed by ejected mass from a galactic merger. In that case, the idea is that almost all the dark matter and most of the baryonic matter from the parent galaxies stayed with the merged entity. This is a low mass galaxy, so it could be an ejected fragment of a much larger galaxy.Edit: I was confused, they did measure the mass by looking at orbital speeds

author: TerraHertz
author_rank: Super Contributor
timestamp: March 31, 2018, 04:33:20 am
content: Hands up all who recognize that finding a galaxy in which orbital velocities are almost as they would be under the influence of standard gravity alone, isn't a proof at all, of what kind of effect is allowing higher orbital velocities of stars in other galaxies. It just demonstrates that *whatever* the cause is, it is possible for it to be absent.It's ironic that galactic stellar orbit theory should suffer so much from circular logic.

author: lordvader88
author_rank: Frequent Contributor
timestamp: March 31, 2018, 05:39:04 am
content: I'd say it's the equations that need more changingBut who knows, worst thing is if human death is real, like on TV and books. or even relatives that are no longer around, and we can't continue past that to find out all this stuff

author: JoeN
author_rank: Frequent Contributor
timestamp: March 31, 2018, 08:57:05 am
content: Now all we have to do is find a galaxy made of all anti-matter and we will be set forever.

author: digsys
author_rank: Unknown
timestamp: March 31, 2018, 09:18:57 am
content: Quote from: JoeNSo whatever happened to that theory? I remember the excitement in the 70s at Uni about "how close" they were to working out where theother 50% of the big bang was, ie anti-matter galaxies. Theory being that thee had to be 50:50 ...If I was anti-matter, I'd be peed off :-)

author: BrianHG
author_rank: Super Contributor
timestamp: April 01, 2018, 12:23:46 am
content: Hubble Views Galaxy Lacking Dark Matter

author: ejeffrey
author_rank: Super Contributor
timestamp: April 02, 2018, 04:09:15 am
content: Quote from: digsys on March 31, 2018, 09:18:57 amBasically, we learned more.First, observations failed to find any significant areas of anti-matter. It turns out that the space between galaxies contains the intergalactic medium. It is very sparse but it is enough that if there were anti-matter regions of the universe we expect to see a bright wall of particle annihilations at the border.Second, both measurements in particle accelerators of CP violation (starting in the 60s) and better theoretical understanding of the standard model gave avenues to introduce a matter-antimatter imbalance.That said, this is still a pretty big mystery. We now know (and observe) that it is possible to create matter and anti-matter in different quantities, but we still don't know how it happened enough to produce the amount of normal matter we see in the universe today.