It's a Star... No, It's a Planet... Well, Who Knows?

Astronomers have observed a strange object orbiting a distant pulsar that seems to be a former star, stripped down to the mass of a large planet by a hungry stellar companion
.

Chalk this one up as one of the universe's most dysfunctional relationships, a bit like an elderly couple who have drained each other's energy throughout an entire lifetime.

The pulsar is a neutron star about 25,000 light years away from Earth, spinning at an extraordinarily rapid rate of hundreds of times per second. NASA's Swift Burst Alert space-based telescope picked up a flare of X-rays and gamma rays from the ordinarily invisible star on June 7. But a tiny modulation in the X-rays observed tipped scientists off that there was something odd going on.

Their analysis points to a companion object, at least 7 times the size of Jupiter (but unlikely to be more than 30 times its size), orbiting the pulsar once every 54.7 minutes, at a distance slightly less than that of the Earth to the Moon.

Is this a planet? Not exactly, researchers think. More of a star that's fallen on hard times:

"This object is merely the skeleton of a star," says co-discoverer
Craig Markwardt of NASA’s Goddard Space Flight Center in Greenbelt, Md.
"The pulsar has eaten away the (companion) star’s outer envelope, and all the remains is its helium-rich core."

Once upon a time, the pulsar was likely a very massive star, and the orbiting object a nearby star one to three times as large as our own
Sun. The bigger star went supernova, ultimately collapsing into today's rapidly spinning neutron star. The smaller began to "puff up" as it aged, while falling farther into the orbit of its larger companion.

Over time, the two have gotten closer to each other. Researchers believe that the pulsar has stripped off gaseous material from its smaller companion, which periodically falls onto the neutron star, causing outbursts like the one observed by astronomers in June.

Astronomers say they've seen only 8 other such pairs previously, and only one with such a small orbiting companion. Researchers from MIT and
NASA's Goddard Space Flight Center independently observed the body, and are publishing their results jointly in Astrophysical Journal Letters.

NASA Astronomers Find Bizarre Planet-Mass Object Orbiting Neutron Star [NASA]

(Image Credit: Aurore Simonnet/Sonoma State University)