Astronomers studying two rare types of binary systems containing rapidly spinning neutron stars called pulsars have observed some unique behavior -- these pulsars consume their mates.
Black widow spiders and their Australian cousins, known as redbacks, are infamous for their tainted love as they have an unsettling tendency to kill and devour their male partners. According to astronomers, they have observed the same behavior among the two binary systems in question.
“The essential features of black widow and redback binaries are that they place a normal but very low-mass star in close proximity to a millisecond pulsar, which has disastrous consequences for the star,” said Roger Romani, a member of the Kavli Institute for Particle Astrophysics and Cosmology, an institute jointly run by Stanford University and SLAC National Accelerator Laboratory in Menlo Park, Calif.
At least 18 black widow and nine redback binary systems have been found within the Milky Way so far, and additional members of each class have been discovered within the dense globular star clusters that orbit our galaxy.
According to astronomers, more than 300 millisecond pulsars have been cataloged so far, and more than half of them have a stellar partner, suggesting that interactions with a normal star can rejuvenate an older and slower pulsar.
“The high-energy emission and wind from the pulsar basically heats and blows off the normal star's material and, over millions to billions of years, can eat away the entire star,” Alice Harding, an astrophysicist at NASA, said in a statement. “These systems can completely consume their companion stars, and that's how we think solitary millisecond pulsars form.”
One black widow system, named PSR J1311-3430 (J1311, for short), that was discovered in 2012, sets the record for the tightest orbit of its class, and contains one of the heaviest pulsars known. On the other hand, the companion star in the system is only a dozen times the mass of Jupiter and just 60 percent of its size.
Astronomers used NASA's Fermi Gamma-ray Space Telescope to examine J1311 and found that the side of the star facing the pulsar was heated to more than 21,000 degrees Fahrenheit -- more than twice as hot as the sun's surface -- while the cooler side was glowing at a temperature of 5,000 degrees Fahrenheit, which is almost half the sun's surface temperature.
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