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

PASADENA, Calif. — NASA’s Spitzer Space Telescope has imaged a wild creature of the dark — a coiled galaxy with an eye-like object at its center.

The galaxy, called NGC 1097, is located 50 million light-years away. It is spiral-shaped like our Milky Way, with long, spindly arms of stars. The “eye” at the center of the galaxy is actually a monstrous black hole surrounded by a ring of stars. In this color-coded infrared view from Spitzer, the area around the invisible black hole is blue and the ring of stars, white.

The black hole is huge, about 100 million times the mass of our sun, and is feeding off gas and dust along with the occasional unlucky star. Our Milky Way’s central black hole is tame by comparison, with a mass of a few million suns.

“The fate of this black hole and others like it is an active area of research,” said George Helou, deputy director of NASA’s Spitzer Science Center at the California Institute of Technology in Pasadena. “Some theories hold that the black hole might quiet down and eventually enter a more dormant state like our Milky Way black hole.”

The ring around the black hole is bursting with new star formation. An inflow of material toward the central bar of the galaxy is causing the ring to light up with new stars.

“The ring itself is a fascinating object worthy of study because it is forming stars at a very high rate,” said Kartik Sheth, an astronomer at NASA’s Spitzer Science Center. Sheth and Helou are part of a team that made the observations.

In the Spitzer image, infrared light with shorter wavelengths is blue, while longer-wavelength light is red. The galaxy’s red spiral arms and the swirling spokes seen between the arms show dust heated by newborn stars. Older populations of stars scattered through the galaxy are blue. The fuzzy blue dot to the left, which appears to fit snuggly between the arms, is a companion galaxy.

“The companion galaxy that looks as if it’s playing peek-a-boo through the larger galaxy could have plunged through, poking a hole,” said Helou. “But we don’t know this for sure. It could also just happen to be aligned with a gap in the arms.”

Other dots in the picture are either nearby stars in our galaxy, or distant galaxies.

This image was taken during Spitzer’s “cold mission,” which lasted more than five-and-a-half years. The telescope ran out of coolant needed to chill its infrared instruments on May 15, 2009. Two of its infrared channels will still work perfectly during the new “warm mission,” which is expected to begin in a week or so, once the observatory has been recalibrated and warms to its new temperature of around 30 Kelvin (about minus 406 degrees Fahrenheit).

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, also in Pasadena. Caltech manages JPL for NASA. Spitzer’s infrared array camera, which made the observations, was built by NASA’s Goddard Space Flight Center, Greenbelt, Md. The instrument’s principal investigator is Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics.