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Hubble Finds Evidence of Dark Matter Around Small Galaxies

Perseus Cluster.  Credit: NASA, ESA, and Z. Levay (STScI)

Perseus Cluster. Credit: NASA, ESA, and Z. Levay (STScI)


The Hubble Space Telescope has uncovered a strong new line of evidence that galaxies are embedded in halos of dark matter. By looking at the Perseus galaxy cluster, Hubble discovered a large number of small galaxies that have remained intact while larger galaxies around them are being ripped apart by the gravitational tug of other galaxies. “We were surprised to find so many dwarf galaxies in the core of this cluster that were so smooth and round and had no evidence at all of any kind of disturbance,” said astronomer Christopher Conselice of the University of Nottingham, UK, and leader of the team that made the Hubble observations. “These dwarfs are very old galaxies that have been in the cluster for a long time. So if something was going to disrupt them, it would have happened by now. They must be very, very dark-matter-dominated galaxies.”

Observations by Hubble’s Advanced Camera for Surveys spotted 29 dwarf elliptical galaxies in the Perseus Cluster, located 250 million light-years away and one of the closest galaxy clusters to Earth. Of these galaxies, 17 are new discoveries.

Cosmologists estimate that dark matter comprises 23 percent of all energy in the cosmos. An equally mysterious “dark energy,” which drives galaxies apart, is thought to take up another 73 percent or so. The ordinary matter that we can see is believed to represent only four percent of the total mass of the Universe.

Because dark matter cannot be seen, astronomers detected its presence through indirect evidence. The most common method is by measuring the velocities of individual stars or groups of stars as they move randomly in the galaxy or as they rotate around the galaxy. The Perseus Cluster is too far away for telescopes to resolve individual stars and measure their motions. So Conselice and his team derived a new technique for uncovering dark matter in these dwarf galaxies by determining the minimum additional mass contribution from dark matter that the dwarfs must have to protect them from being disrupted by the strong, tidal pull of gravity from larger galaxies.

Galaxies in the Perseus Cluster. Credit: NASA, ESA, and Z. Levay (STScI)

Galaxies in the Perseus Cluster. Credit: NASA, ESA, and Z. Levay (STScI)



The dwarf galaxies may have an even higher amount of dark matter than spiral galaxies. “With these results, we cannot say whether the dark matter content of the dwarfs is higher than in the Milky Way Galaxy,” Conselice said. “Although, the fact that spiral galaxies are destroyed in clusters, while the dwarfs are not, suggests that this is indeed the case.”

But these new images provide evidence that the undisturbed galaxies are enshrouded by a “cushion” of dark matter that protects them from being torn apart.

Source: HubbleSite

About 

Nancy Atkinson is Universe Today's Senior Editor. She also works with Astronomy Cast, and is a NASA/JPL Solar System Ambassador.

Comments on this entry are closed.

  • DrFlimmer March 16, 2009, 10:13 AM

    :-D

    Anaconda, you make me laugh, really. So I try to be even more precise with what I try to tell you:

    The solar wind consits of electrons, protons and ions, right?
    I said that all species are moving very uniformly. What did I mean?
    I meant that if you take a random ccm of space in the solar system, you will find electrons, protons and ions moving away from the sun. It doesn’t matter how dense it is. What matters is that you have the same amount of charges in your volume and that these charges are moving with the same velocity. The particles at a random spot in the solar wind are moving with the same speed away from the sun. I think, this should be clear enough, now.

    But how can you explain such a movement with a charged sun?
    Btw: Why did you just refer to that ONE sentence and didn’t answer to the whole thing?
    Why are you insulting me, while you are guilty of the same behaviour?

    I definitly made some mistakes over at BA, but what about quarks, anti-matter, CMB (how does EU, PC or PU explain it?) and so on?

    I just wonder, who is more reliable?
    I’m going to get my master degree in physics next year. That doesn’t proove that I am an intelligent man or that I should know everything, definitly not.
    But what about someone, who has even no grisps of mathematics and disputes physics?
    Who is more reliable, I wonder?

    “The first is an an offer of evidence based completely on an abstract equation where if you build enough derivative equations will eventually lead you to all the phenomenon in the Universe.”

    You have absolutly no idea what you are talking about!
    Even your plasma physics are written in derivative equations. And since electromagnetism has very complicated equations, the same is right for plasma physics. And the more comlicated your problem is, which you like to describe, the more complicated is your equation. And that is right for every problem in physics – even in plasma physics.

  • ND March 16, 2009, 10:14 AM

    Trippy,

    Anaconda gave his opinion on ambiplasma on the Bad Astronomy blog:

    blogs.discovermagazine.com/badastronomy/2009/01/28/the-roar-of-the-centaur/#comment-152870

  • DrFlimmer March 16, 2009, 11:07 AM

    To give an example of plasma equations. One very fundamental formula is the Vlasov equiation. It tells us something about the time evolution of a plasma.
    Since a plasma consits of many particles one cannot solve the equaions of motion for every particle. Instead one analyses the distribution function f(x,v,t) where x is the coordinate of space, v the velocity and t is the time. This function includes every particle in a statistical fashion.
    To gain the time evolution of that distribution function (and thus of the plasma) one has to solve the Vlasov equation. In the collisionless form it reads:

    df/dt + v df/dx + d/dv (af) = 0

    with a being the acceleration of the particles. This seems to be very simple, but finding the solution can be a tough task.
    Including collisions (like Coulomb collisions) the equation reads:

    d(f_i)/dt + v d(f_i)/dx + d/dv (a(f_i)) = sum_q C(i,q)

    where sum_q means that one has to sum over the index q and “C(i,q) is the rate of change of f_i due to collisions of species i with species q”.
    (Quote and equations from “Fundamentals of plasma physics” by Paul M. Bellan)

  • Trippy March 16, 2009, 11:54 AM

    Anaconda:

    Enough with the dishonesty already.

    I said that the Observations were done in the UV with Hubble.

    I also said that the last Wikipedia article you cited supported what I had to say.

    This article doesn’t just talk about blackholes. And I’m well aware that the Chicago paper uses the term point singularity (having actually read it) but having actually studied relativity…

    Ugh.

    The simple fact that you’re completely failing to grasp is that according to relativity, Singularities exist, however what I have been saying is that most physicists will agree that that is a reflection of relativity breaking down under those conditions – in other words, Relativity is throwing its hands up in the air in disgust and saying “You want me to do what?”

    The point that you’ve failed to grasp is that because relativity predicts black holes, and because we’ve got nothing that doesn’t break down inside a black hole (we’ve got string theory, but that has yet to usurp relativity), those articles talk about the predictions of relativity.

    ANYBODY who has ACTUALLY studied relativity will tell you the same thing – that based on what we currently understand, at some point inside the event horizon of a black hole, the quantization of gravity starts to become important, and relativity begins to break down, and the singularity that relativity predicts lurks inside a blackhole is a reflection of this.

    This is the point that I have been arguing the whole time, and that you’ve failed to grasp, not this strawman that you’ve concocted.

  • Trippy March 16, 2009, 11:57 AM

    “I hold Plasma Cosmology to the same standards I hold the gravitational model to: Observation and measurement are required. Ambiplasma has never been observed or measured, neither has antimatter. These are theoretical speculations which I am not convinced of. ”

    If you Genuinely believe that Anaconda – I suggest you go to Wikipedia and look up Positron Emission Tomography, or even just Positron.

  • IVAN3MAN March 16, 2009, 12:01 PM

    I am resubmitting this because I am not sure if the first one got through, so apologies if it results in a double posting…

    @ Anaconda:

    All this from a guy who denied there were electric currents in space and that Birkeland currents are electric currents…

    I never that claim. Show me evidence to the contrary.

    But that’s not all. Ivan3Man, was also in denial regarding the fact that electric current is the only known way to cause magnetic fields.

    Yes, and I provided links at Bad Astronomy to articles that refer to two kinds of magnetic sources: (1) motion of electric charges, such as electric currents and (2) the intrinsic magnetism of elementary particles, such as the electron.
    Anaconda, however, obviously ignored them — just like bloody creationists!
    Furthermore, the NASA article that you provided a link to clearly states:

    Any electric current, however, must flow in a closed circuit [my emphasis], and since it seemed to be caused (like that of the aurora) by processes taking place in distant space, Birkeland proposed that it came down from space at one end of the arc and returned to space at the other end.

    The accompanying drawing in the article illustrates a circulating current of charged particles within the Earth’s magnetosphere. Space is defined as the region just above the Earth’s atmosphere and beyond; it does not state in the article that electric currents come from deep space, which is what “Electric Universe” proponents like you, Anaconda, are insinuating.

  • Salacious B. Crumb March 16, 2009, 12:01 PM

    Hey Trippy
    The next thing we will hear is PR – Plasma Relativity !!! ;)

  • IVAN3MAN March 16, 2009, 12:43 PM

    @ Trippy:

    If you Genuinely believe that Anaconda – I suggest you go to Wikipedia and look up Positron Emission Tomography, or even just Positron.

    Trippy, my fellow correspondents and I have already provided links, on Bad Astronomy, to various articles proving the existence of anti-matter, quarks, etc., for Anaconda to peruse, but he just ignores them — just like a bloody creationist!

  • Trippy March 16, 2009, 12:46 PM

    IVAN3MAN:

    I’d believe that – question, how do you get your quotes to come up in gray boxes like that?

  • IVAN3MAN March 16, 2009, 4:16 PM

    @ Trippy:

    [H]ow do you get your quotes to come up in gray boxes like that?

    Use these HTML tags: <blockquote>PLACE QUOTE HERE</blockquote> (N.B. Make sure that the closing tag has the “/” in front of “blockquote”).

  • IVAN3MAN March 16, 2009, 5:52 PM

    Anaconda is an unmitigated sophist, and this is how Wikipedia defines sophism:

    In modern usage, sophism, sophist, and sophistry are derogatory terms, due the influence of many philosophers in the past (sophism and Platonism were enemy schools).

    A sophism is taken as a specious argument used for deceiving someone. It might be crafted to seem logical while actually being wrong, or it might use difficult words and complicated sentences to intimidate the audience into agreeing, or it might appeal to the audience’s prejudices and emotions rather than logic, i.e., raising doubts towards the one asserting, rather than his assertion. The goal of a sophism is often to make the audience believe the writer or speaker to be smarter than he or she actually is, e.g., accusing another of sophistry for using persuasion techniques. An argument Ad Hominem is an example of Sophistry.

    A sophist is a user of sophisms, i.e., an insincere person trying to confuse or deceive people. A sophist tries to persuade the audience while paying little attention to whether his argument is logical and factual.

    Sophistry means making heavy use of sophisms. The word may be applied to a particular text or speech riddled with sophisms.

    Yep, that sounds like Anaconda, alright!

  • Anaconda March 27, 2009, 8:12 AM

    Returning after the Dust settled.

    Ivan3Man spends more effort detailing the term “sophist” then pointing to anything I stated that was sophist. What intensity of magnetic field would be generated by a stationary electron? Rather, it is the ordered, vector motion of electrons that generates a magnetic field. “Intrinsic” magnetism refers to the magnetic moment, the “spin” of electrons. If enough electrons are “spinning” in the same orientation, then magnetism occurs, which in turn induces electron movement among the atoms and in turn generates larger magnetic fields.

    Obviously, there is something “intrinsic” about an electron which upon ordered, vector motion generates a magnetic field.

    It all comes back to ordered motion of electrons generating magnetic fields, whether in vector motion or in “spin”.

    So, am I being sophist to point that out?

    Or is it a case of projection by Ivan3Man?

  • ND March 29, 2009, 2:16 PM

    I check on old threads once in a while if I can find them and sure enough Anaconda pops up to get the last word.

    Anaconda: “Returning after the Dust settled.”

    Is this not a dirty trick you’re playing?

  • An-Idiot but trying to learn April 22, 2009, 7:36 AM

    Okay im an idiot, but why cant light be a factor influencing the production of gravity in some kind of interaction with magnetic fields on both a large scale and within an atom?

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