"Quarks, matter's smallest known building blocks, don't reveal themselves
easily. Scientists can study them only by colliding subatomic particles
so that they break into their constituent quarks.
But these stick back together again an instant later,and the show is over.
Quark stars contain quarks liberated from
the confines of neutrons, subatomic particles that contain triplets of
quarks. Quark stars are also called strange stars because they contain a
type of quark called strange quarks.
Now, researchers suggest there is another way to study quarks, by
examining certain super-dense stars called neutron stars.
These are so compact that a teaspoon full of their material would weigh
billions of tons.
The density creates such high pressure at the core that quarks
sometimes could be squeezed out of their usually tight groupings,
and become free. This liberation, called quark deconfinement,
would turn a normal neutron star into a "quark star."Astronomers
have already found a few objects that they theorize may be
quark stars.
But Rachid Ouyed, an astrophysicist at the University of
Calgary in Canada and a group of colleagues also propose
that their formation could release massive amounts of energy,
producing a type of implosion they call a "quark nova."
That, they add, may help explain certain hitherto
mysterious cosmic blasts.
"Quark stars are the only place we would expect to see quarks
ranging free in nature," said Ouyed.
His group plans to present findings of their theoretical
studies June 5 at the American Astronomical Society meeting in Calgary.
Most likely to become quark stars are fast-spinning neutron
stars with masses between 1.5 and 1.8 times that of our sun, they
calculated. Thus one in every hundred known neutron stars could
actually be a quark star.
"If our theory turns out to be correct, then we could see two
quark-novae every day," said Ouyed, adding that quark stars
may be fairly common.
Quark stars probably look like normal neutron stars except
they don't emit certain radio waves, the researchers argue.
This peculiarity has already been noted in a class of neutron stars
described as "radio-quiet," about seven of which are known.
Thus, these may be quark stars, the scientists say.
The theory may also explain another puzzling
phenomenon known as gamma ray bursts, the group claims—explosions
that occasionally let out, in a few seconds, about a million times
as much energy as our sun does in a year.
Ouyed argues that these may be linked to quark-novae.
In computer simulations, he and colleagues have predicted how
a neutron star's magnetic field would change as it becomes a
quark star. The simulations, also to be presented at the meeting,
show an explosion with energy comparable to that of
gamma ray bursts."