"Becauseit is so bright, and probably close to Earth, it is a promising target for manytypes of observations," Fox said. If true, the object is 250 to 1,000 light-yearsaway-making it one of the closest known neutron stars. "Thebest guess is that it is still close to its birthplace, and therefore close toEarth," Rutledge said. In order to reach itscurrent position, it had to wander some distance out of the disk. "EitherCalvera is an unusual example of a known type of neutron star, or it is somenew type of neutron star, the first of its kind," Rutledge said.Ĭalvera'slocation high above the plane of our MilkyWay Galaxy is part of its mystery, but researchers think the neutron staris the remnant of a star before exploding as a supernova. Exactly which type of neutron star itis, however, remains a mystery. Rutledge saidthere are no widely accepted alternate theories for objects bright in X-raysand faint in visible light like Calvera.
The teamalso used the ChandraX-ray Observatory, which showed the object as point-like?an observationconsistent with neutron-star appearance. To showthat the object is not associated with any other energy source, the teamtargeted the 8.1-meter Gemini North Telescope in Hawaii on Calvera. "TheSwift observation of this source is what got the show going," said AndrewShevchuk, an astronomy student at Penn State and co-author of the study."As soon as I saw the data, I knew Calvera was a great neutron-starcandidate." TheSwift observations, however, enabled the group to pinpoint the object'sposition more accurately and show that it was not associated with any knownobject.
The groupaimed Swift at the object in August 2006, showing that it was still there andemitting about the same amount of X-ray energy as it had during the 1990s.