Andromeda dwarf galaxies help unravel the mysteries of dark matter

Nov 08, 2011 by Tammy Plotner, Universe Today
The circled cluster of stars is the dwarf galaxy Andromeda 29, which University of Michigan astronomers have discovered. The bright star within the circle is a foreground star within our own Milky Way galaxy. This image was obtained with the Gemini Multi-Object Spectrograph at the Gemini North telescope in Hawaii. Credit: Gemini Observstory/AURA/Eric Bell

Yep. It’s that time of year again. Time to enjoy the Andromeda Galaxy at almost every observing opportunity. But now, rather than just look at the nearest spiral to the Milky Way and sneaking a peak at satellites M32 and M110, we can think about something more when we peer M31′s way. There’s two newly discovered dwarf galaxies that appear to be companions of Andromeda!

Eric Bell, an associate professor in astronomy, and Colin Slater, an astronomy Ph.D. student, found 28 and Andromeda 29 by utilizing the Sloan Digital Sky Survey and a recently developed star counting technique. To back up their observations, the team employed data from the Gemini North Telescope in Hawaii. Located at 1.1 million and 600,000 light-years respectively, Andromeda XXVIII and Andromeda XXIX have the distinction of being the two furthest satellite galaxies ever detected away from the host – M31. Can they be spotted with amateur equipment? Not hardly. This pair comes in about 100,000 fainter than Andromeda itself and can barely be discerned with some of the world’s largest telescopes. They’re so faint, they haven’t even been classified yet.

“With presently available imaging we are unable to determine whether there is ongoing or recent star formation, which prevents us from classifying it as a dwarf spheroidal or a dwarf irregular.” explains Bell.

The dwarf galaxy Andromeda 29, which University of Michigan astronomers have discovered, is clustered toward the middle of this image, obtained with the Gemini North telescope in Hawaii. Credit: Gemini Observstory/AURA/Eric Bell

In their work – published in a recent edition of the edition of the Astrophysical Journal Letters – the team of Bell and Slater explains how they were searching for dwarf galaxies around Andromeda to help them understand how physical matter relates to theoretical dark matter. While we can’t see it, hear it, touch it or smell it, we know it’s there because of its gravitational influence. And when it comes to gravity, many astronomers are convinced that dark matter plays a role in organizing galaxy structure.

“These faint, dwarf, relatively nearby galaxies are a real battleground in trying to understand how dark matter acts at small scales,” Bell said. “The stakes are high.”

Right now, current consensus has all galaxies embedded in surrounding dark matter… and each “bed” of dark matter should have a galaxy. Considering the volume of the Universe, these predictions are pretty much spot on – if we take only large galaxies into account.

“But it seems to break down when we get to smaller galaxies,” Slater said. “The models predict far more dark matter halos than we observe galaxies. We don’t know if it’s because we’re not seeing all of the galaxies or because our predictions are wrong.”

“The exciting answer,” Bell said, “would be that there just aren’t that many dark matter halos.” Bell said. “This is part of the grand effort to test that paradigm.”

Right or wrong… pondering and while observing Andromeda will add a whole new dimension to your observations!

Explore further: Comet Jacques makes a 'questionable' appearance

More information: Andromeda XXVIII: A Dwarf Galaxy more than 350 kpc from Andromeda and Andromeda XXIX: A New Dwarf Spheroidal Galaxy 200 kpc from Andromeda.

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omatwankr
3.3 / 5 (12) Nov 08, 2011
Thank you very much for this fairly pointless article, let me elucidte.

"or because our predictions are wrong."

This should never stand in the way of the advancement of your delusions, be it Repulsive Neutronium, Huggs Bozo-on or that the sex was consensual, only yours thoughts on these matters count, can you see a pattern yet?

Patterns are great I see them everywhere, in the capture codes some sites make you use to prove your humanness (why they are all telling me to burn things I don't know yet) to the hair left in the sink after shaving (Jesus, Sasquatches and Judith Curry (JC^2) have abided in my bathroom and what they were doing to each other I will leave to your imagination, what I saw myself doing in the mirror was bad enough)

"The exciting answer, Bell said"
Repulsive Neutrons is obviously responsible and then linked to some anti-Global warming induced coming Ice-age because the Illuminati are alien-reptiles and love the cold that would kill them as proof.
that_guy
5 / 5 (4) Nov 08, 2011
I haven't seen mr manual on here in a few days. Thanks for stepping in for him.
Ober
not rated yet Nov 08, 2011
To the lower right of the dwarf galaxy is a star with a black dot in it!!! Is it an artifact?? If so, that photo is pretty messed up!!!!
Baseline
1.7 / 5 (6) Nov 08, 2011
Thank you very much for this fairly pointless article, let me elucidte.

"or because our predictions are wrong."

This should never stand in the way of the advancement of your delusions, be it Repulsive Neutronium, Huggs Bozo-on or that the sex was consensual, only yours thoughts on these matters count, can you see a pattern yet?


You know your adolescent postings in pathetic attempts at humor stopped being funny after the first time you posted them. I think you are missing your calling you should be over at Tomshardware and posting Ya but can it play Crysis after every story on new computers. What's the matter son didn't mommy pay enough attention to you as a child?
yyz
5 / 5 (3) Nov 09, 2011
Thanks for reporting on these recent discoveries. I've been keeping track of these numerous new Andromeda dwarf satellite galaxies for some time now, so it's great to see this story on these latest two denizens of our neighboring galaxy (M 31, natch).

There is a discrepancy in the number of known dwarf galaxies belonging to the Milky Way vs Andromeda (despite their nearly equal masses) and this is still a puzzle to those who study such dwarf galaxy systems in the Local Group (poor dwarf spiral M 33 has hardly any satellite dwarf galaxies at all; M 31 may have grabbed them in a past encounter!).

Perhaps this discrepancy has to do with the formation of the individual major galaxies and/or the formation of the Local Group itself, as has been speculated.

Meanwhile, the hunt for these dim, dark matter dominated systems in the Local Group continues.
that_guy
5 / 5 (3) Nov 10, 2011
To the lower right of the dwarf galaxy is a star with a black dot in it!!! Is it an artifact?? If so, that photo is pretty messed up!!!!

You just found the planet nibiru!!!

@baseline - Lighten up. you catch more flies with honey than an asshole. Wait, that can't be correct. You catch more flies with honey than vinegar.

I'll give you that some of the jokes are tired, but Mr Oliver K Manuel is a quack that just doesn't give up, and we get really tired of him.