Israeli scientists discover evidence of a strange star

JERUSALEM — Weizmann Institute scientists have discovered signs of the existence of a star in our galaxy that is made from compressed quarks.

This new "strange star," if finally identified, will confirm the existence of a new class of celestial bodies that Professor Edward Witten of the Institute for Advanced Study in Princeton, N.J., predicted nearly 15 years ago.

Its crucial component is the "strange quark" — one of six types of quarks, which are the tiniest building blocks of matter.

In research published in the Jan. 12 issue of "Physical Review Letters," Professor Vladimir Usov of the Rehovot institute's condensed matter physics department outlined the last of three characteristics that could enable astronomers finally to identify examples of "strange stars."

"Only a handful of the heavenly bodies observed in our galaxy are probably `strange stars,' but they would constitute a totally new class of celestial objects with extraordinary properties," he said.

The three unique features he set down would distinguish them from the more common neutron star, even though both types look very similar. There are nearly 1,000 neutron stars in the earth's galaxy, and about 1 percent may be "strange stars," said Usov; so may be some of the 20 or so enigmatic bodies that astronomers think are black holes.

If "strange stars" are positively identified by Usov's criteria, this would settle a major dispute in particle physics on the existence of matter composed of quarks — the most stable matter in the universe.

But quarks rarely exist as separate entities, and it's possible to get only a brief glimpse of their existence in high-energy particle accelerators. So "strange stars" would offer scientists their only chance to observe a large and stable "piece" of quark matter.

Usov used theoretical calculations to identify the three unique behaviors of these stars: the energy of X-rays emitted by a "strange star" is 10 to 100 times greater than that emitted by a neutron star; these X-rays are fired in pulses from a "strange star"; and the "strange star" contains a small amount of electrons in addition to the quarks, creating a very strong electrical field over its surface.

The Weizmann expert said that one likely candidate for a "strange star" is located near the center of the galaxy and believed by many to be a black hole. But, because it meets his three criteria, he believes it could be a "strange star."