Milky Way May Have Dark Matter Satellite Galaxies

rubycodez writes "Berkeley astronomer Sukanya Chakrabarti has detected perturbations in the gases surrounding our Milky Way and concludes there is a satellite 'Galaxy X' 250,000 light years away that is mostly dark matter, but that may contain dwarf stars visible in infrared. She expects many more such dark matter satellites to the Milky Way to be discovered using her technique."

Comments

Dark matter vs black holes

[Fractal Dice]

How do you tell the difference between a blob of dark matter and a black hole? With all the small galaxies the Milky Way has swallowed over its lifetime, would it not be reasonable to find some relic black holes that have swung back out after being stripped of most of their surrounding gas/stars? Or, when "dark matter" is being talked about in this situation, is a black hole simply one of the possible candidates to supply the mystery mass?

Re:Dark matter vs black holes

[Monkeedude1212]

How do you tell the difference between a blob of dark matter and a black hole?

Gravitational pull is probably the biggest factor. A black hole simply gets so massive that at one point the gravitational pull is so strong that not even light can escape. It will have objects orbitting around it like planets orbit stars except at distances far greater than a star would normally hold.

Dark Matter, on the other hand, simply seems to have the gravitational pull of a regular star, but doesn't emit any light.

One thing to note is that when we observe things out there, it's not just a 2D plane we're observing but a great deal of depth is involved. When observing a black hole, the light behind the black hole will get sucked into the black hole if it happens to cross the event horizon. This will create a nice black circle in the sky. However dark matter, on the other hand, would not stop the light behind it from reaching our eyes, it might bend it a little but nothing too extreme.

Re:This sounds like a sci-fi blockbuster

[Black Parrot]

"The creature from invisible Galaxy X"

There was an interesting musing by the author of a recent Scientific American about how dark matter may interact with its own kind by forces other than the ones that cause normal matter to interact with its own kind. According to the musing (which the author rejects), dark matter operating under such forces could form complex systems, maybe even an unseen parallel universe where "people" live lives like ours, as unaware of us as we are of them. All undetectable, except by their gravitational attraction on us.

Re:Mark my words

[Black Parrot]

Let's get this out of the way first:

And we don't have any way to test for matter whose only property is it brings our mathematical formulae in line with our physical observations.

The, "Gee, that's funny" observation is what drives all science.

Now:

Making observations and theories is part of science. But what sets science apart from superstition is rigorous testing of the theories.

Believe it or not, some scientists do real science.

There was a competing explanation for this family of "Gee, that's funny" observations called MOND - Modification Of Newtonian Dynamics. It was ruled out on the basis of evidence. (There may be a MOND v. 2.0 out there now - not sure.)

One candidate for dark matter is the sterile neutrino, which people - real scientists - are trying to detect right now. A few years ago they were almost ready to dismiss its existence, but more recent results suggest that it may actually exist.

So no, contrary to your majestic disbelief, dark matter is a Real Hypothesis (tm), investigated by Real Scientists (tm), doing Real Science (tm).

If you want to actually learn something about the topic rather than simply using Slashdot as an outlet for you whingeing about the universe not working the way you learned in fifth grade, Wikipedia is an easy place to get started.