THE universe's darkest secret may be hiding not far from us. Three dwarf galaxies near the Milky Way appear to contain a higher proportion of invisible dark matter than any stellar system so far studied. If so, they are the ideal place to look to figure out what the stuff consists of.
Over the past three years, the Sloan Digital Sky Survey has identified Ursa Major II, Willman I and Coma Berenices Dwarf as small satellite galaxies of the Milky Way. Louis Strigari of the University of California, Irvine, analysed the motion of their stars and found that they appear to be subject to a gravitational field equivalent to that of at least 1 million solar masses distributed around each galaxy. Yet each of these galaxies only shines as bright as 1000 suns, a discrepancy which leads Strigari to suggest that these galaxies are rich in unseen dark matter.
Strigari says observing these galaxies is an excellent way to identify what dark matter is. For example, from the energy of any gamma rays we could infer that certain types of particle are annihilating with their own antiparticles. The galaxies' closeness and the concentration of dark matter makes observing them easy (The Astrophysical Journal, vol 678, p 614).
Dan Hooper at Fermilab in Batavia, Illinois, thinks Strigari is right that these dwarf galaxies are dominated by dark matter. But he says that the centre of the Milky Way is the best place to look for gamma-ray signals, even though it is slightly further away, as it contains a greater volume of dark matter than these galaxies.
Cosmology - Keep up with the latest ideas in our special report.
By Tissa Perera
Sat May 31 01:40:58 BST 2008
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By Polemos
Wed Jun 04 16:45:26 BST 2008
We are at the absolute gravitational centre of the Universe. Vacuum is more organised in the vicinity of the centre, hence the anomalous gravity of the nearby galaxies. The matter is that the Universe is gravitationally imploding, and this implosion in nonuniform - it is faster at the centre.By Luigi V.
Wed Jun 04 18:35:47 BST 2008
And you have evidence of this? Refferences please?By Polemos
Wed Jun 04 20:20:47 BST 2008
Positive feedback. Like money attracts more money; gravity attracts more gravity, which exponentially accelerates the implosion (the distant galaxies seem to receed).By Luigi V.
Thu Jun 05 15:57:47 BST 2008
But that can happen anywhere. How do you infer that we're at the center of the Universe from it? ...By Michael
Wed Jun 04 20:21:17 BST 2008
You managed to fly in the face of evidence on 6 counts.By Steve
Wed Jun 04 21:29:00 BST 2008
Hmm...the only thing imploding appears to be your credibility. You need to provide references for your claim, as others have requested.By Polemos
Wed Jun 04 21:44:22 BST 2008
A more organised medium is more compact. Conscious beings are the summit of organisation. Hence, the vacuum in the galactic vicinity of the Earth must be the most compact and its gravity tug ("dark energy") will be strongest.By Tim
Thu Jun 05 07:49:48 BST 2008
Ah yes, I understand. So the most compact vacuum in the universe must be in the vicinity of your head?By Charles
Fri Jun 06 06:24:02 BST 2008
"A more organised medium is more compact. Conscious beings are the summit of organisation. Hence, the vacuum in the galactic vicinity of the Earth must be the most compact and its gravity tug ("dark energy") will be strongest."By Acoyauh
Thu Jun 05 16:07:25 BST 2008
Sorry, but I still don't see references, the math or even the logic in it. It seems it's just a coment you pulled out of your sleeve.By Polemos
Thu Jun 05 17:40:56 BST 2008
"Sorry, but I still don't see references, the math or even the logic in it."By Anonymous
Thu Jun 05 19:31:43 BST 2008
"References? What references can I provide when I am the first who has ever had this idea?"By Polemos
Thu Jun 05 21:36:11 BST 2008
The primary virtue of a theory is its compliance with the first principles. If a theory complies with a thousand of external evidences but does not comply with a single first principle, the theory is wrong.By Whipster
Mon Jun 09 11:18:04 BST 2008
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