Observatory pinpoints rare neutron star
HILO » Astronomers used the Gemini North observatory on Mauna Kea and space telescopes to discover a rare "isolated neutron star" spraying X-rays in the solar system's cosmic neighborhood, according to an article prepared for the Astrophysical Journal.
Puzzled by some aspects of the astronomers' discovery, and inspired by a movie reference, authors Robert Rutledge, Derek Fox and Andrew Shevchuk named their neutron star "Calvera" after a marauding cinema bandit. Seven other isolated neutron stars had previously been discovered and were named the "Magnificent Seven" after the 1960 movie, in which a character called Calvera was the main bad guy.
Neutron stars are objects that were once real stars but in their old age blew up, leaving only a scrap of enormously dense rock spewing X-rays and gamma rays.
Calvera is probably only a few miles in diameter, yet a thumb-size piece of it weighs millions of tons.
Rutledge, at McGill University in Montreal, became suspicious about the object eventually named Calvera when he compared a catalog of 18,000 X-ray sources with corresponding visible light sources. Calvera, he discovered, did not show a visible light source.
In August 2006, Fox, at Pennsylvania State University, mission operations center for the Swift space telescope, turned the X-ray portion of the instrument toward the strange object.
"As soon as I saw the data, I knew Calvera was a great neutron star candidate," he told Space.com.
Gemini North on Mauna Kea granted the team viewing time to rule out any companion object with Calvera. The Chandra space X-ray telescope was used for further proof that Calvera is "isolated."
Only seven other neutron stars have been discovered without companions, the "Magnificent Seven." All of those are in or near the disk of the Milky Way galaxy.
Calvera showed itself as an outlaw again, located well above the disk in an area called the "galactic halo."
And it is not far away, somewhere between 250 and 1,000 light-years distant.
The exact distance depends on Calvera's exact nature, which the astronomers have not figured out yet.