Archive for December, 2009

Woman Beats The Crap Out Of A Would Be Thief

December 8th, 2009

Rumor has it that the first dark matter particle has been found!

December 8th, 2009

Dark Matter

The physics blogs are abuzz with rumors that a particle of dark matter has finally been found.

If it is true, it is huge news. Dark matter is thought to make up 90 per cent of the universe’s mass and what evidence there is for it remains highly controversial. That’s why any news of a sighting is seized upon.
The Cryogenic Dark Matter Search experiment is one of several designed to look for the tell-tale signature of dark matter particles passing through. No one is sure what a dark matter particle will look like, though theory gives some pointers.
Most of the experiments have been designed to look for elusive massive particles called WIMPS that barely register as they pass through matter, because the only forces they experience are gravity and the weak nuclear force.
CDMS is located deep underground in the Soudan mine in Minnesota, to protect it from the hail of cosmic rays that would otherwise wash out any dark matter signal.
Earlier this year, the collaboration published a paper in Physical Review Letters (vol 102, p011301) based on two series of experiments between October 2006 and July 2007. They found nothing.
So researchers have been waiting eagerly for the next chapter of the story – maybe with more time, more experience running their detector and a sprinkling of luck, the team would spot a dark matter particle.
The gossip mill went into overdrive after a rumor leaked out that the CDMS collaboration has had a paper accepted by the journal Nature. Word is that the paper will appear in the 18 December issue.

Nature is an unusual place for particle physicists to publish their papers and this has prompted speculation that the news must be big.
A few physicists I know say that talks have hurriedly been scheduled for 18 December at SLAC National Laboratory, the University of California Santa Barbara and Fermilab – all prominent institutions within the CDMS collaboration.
We’ll have to wait and see if the rumors turn out to be true. Even if not, with NASA’s Fermi satellite looking for dark matter in space and the Large Hadron Collider up and running, 2010 could be the year we finally crack the dark matter mystery.

Via: New Scientist

Some black holes may actually be ‘quark stars’

December 7th, 2009

black hole, quark star

Think black holes are strange? Understandable, considering these powerhouses of the universe (many times heavier than our sun) are collapsed stars with gravity so strong that even light cannot escape their grasp.

But maybe they’re not “strange” enough, some astrophysicists suggest. “Stellar” black holes, ones only a few times heavier than the sun, may actually be something even weirder called a quark star, or “strange” star.

A physics team led by Zoltan Kovacs of the University of Hong Kong sizes up the issue in the current Monthly Notices of the Royal Astronomical Society. Quark stars are only theoretical right now, but “the observational identification of quarks stars would represent a major scientific achievement,” Kovacs says.

If quark stars exist, it could prove a theory that normal matter – the stuff of people, planets and stars – isn’t stable and could help explain the existence of the “dark matter” that fills much of the universe.

First suggested in 1970, a strange star is a collapsed star that doesn’t quite crumple enough to turn into a full-fledged black hole and yet is too heavy to become a so-called neutron star (at least 1.4 times heavier than the sun.) Neutron stars do exist, as astronomer Jocelyn Bell showed with the discovery of a pulsar, a spinning neutron star that streams particles from its poles.

In a quark star, gravity would be so strong that it squeezes the subatomic particles called quarks right out of the protons and neutron building blocks of the original star’s atoms. That would leave behind a solid mass of quark stuff called strange matter, hence the name “strange star.”

Earlier in the decade, astronomers suggested that a neutron star called RX J1856, about 400 light-years away (one light-year is about 5.9 trillion miles) was about one-third too small and might be a quark star. But a 2004 Nuclear Physics B journal report showed the star’s intense magnetic field explained its size, so it really was a neutron star.

So, if size alone won’t reveal a quark star, what will? In the new study, Kovacs and his colleagues, Cheng Kwong-sang and Tiberiu Harko, analyze the disks of dust and gas circling supposed black holes. Whipped to high speeds by the intense gravity of a black hole, these disks are thought to heat to high temperatures and emit powerful radiation. For a quark star, the radiation would be about 10% less than predicted around a black hole, they find. And a quark star would give off a dim light (called bremsstrahlung emission), unlike a black hole, emitted by a thin layer of electrons on its surface.

The complete article can be read at USAToday.com