NS: Hints of lightweight dark matter particle found in space

[bystander]

Hints of lightweight dark matter particle found in space
New Scientist | Space | Physics & Math | 28 Oct 2010

Hints of a lightweight dark matter particle have been found in the gamma-ray glow at the Milky Way's heart. The particle's apparent mass lines up with tentative signals of dark matter in two direct-detection experiments on Earth, but other researchers caution that conventional sources – such as pulsars – may be responsible for the gamma-ray light instead.

The Milky Way is thought to be awash in dark matter, an as-yet-unidentified substance that makes up more than 80 per cent of the matter in the universe. Although dark matter has been detected by its gravitational tug on stars and galaxies, many of its fundamental properties are still unknown.

One way to study dark matter is to look for the gamma-ray light produced when dark matter particles meet and annihilate one another, producing a cascade of other particles and radiation. Since dark matter particles rarely interact, the best place to look for this light is at the centres of galaxies, where concentrations of dark matter particles are densest.

The Milky Way's centre seems to be aglow with the light from dark matter annihilation, say Dan Hooper of the Fermi National Accelerator Laboratory in Batavia, Illinois, and Lisa Goodenough of New York University in New York City.

Has Dark Matter Finally Been Seen? Time Will Tell
Space.com | Science | 27 Oct 2010

This view of the gamma-ray sky is constructed from one year of Fermi Large Area Telescope (LAT) observations. The blue color includes the extragalactic gamma-ray background. The map shows the rate at which the LAT detects gamma rays with energies above 300 million electron volts — about 120 million times the energy of visible light — from different sky directions. Brighter colors represent higher rates. [i](Credit: NASA/DOE/Fermi LAT Collaboration)[/i]

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In a new finding that could have game-changing effects if borne out, two astrophysicists think they've finally tracked down the elusive signature of dark matter.

This invisible substance is thought to make up much of the universe — but scientists have little idea what it is. They can only infer the existence of dark matter by measuring its gravitational tug on the normal matter that they can see.

Now, after sifting through observations of the center of our Milky Way galaxy, two researchers think they've found evidence of the annihilation of dark matter particles in powerful explosions.

"Nothing we tried besides dark matter came anywhere close to being able to accommodate the features of the observation," Dan Hooper, of the Fermi National Accelerator Laboratory in Batavia, Ill., and the University of Chicago, told SPACE.com. "It's always hard to be sure there isn't something you just haven't thought of. But I've talked to a lot of experts and so far I haven't heard anything that was a plausible alternative."

Hooper conducted the analysis with Lisa Goodenough, a graduate student at New York University.

Dark Matter Annihilation in The Galactic Center As Seen by the Fermi Gamma Ray Space Telescope

• arXiv.org > hep-ph > arXiv:1010.2752 > 13 Oct 2010 > Dan Hooper, Lisa Goodenough