Two-faced star reveals a pulsar’s surprising bulk | Science News

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Two-faced star reveals a pulsar’s surprising bulk

An ultramassive pulsar is frying its stellar companion

9:00am, May 31, 2018
illustration of a pulsar and companion star

PICK A SIDE  A pulsar (starburst illustrated in lower right) heats just one side of its companion star in this binary system called PSR J2215+5135. The duality helped astronomers weigh the pulsar, and showed it’s one of the most massive ever seen.

A two-faced star just helped weigh an extra-massive pulsar.

The star takes about four hours to orbit its companion, a fast-spinning stellar corpse called a pulsar that’s about 10,000 light-years from Earth. That means the pair’s orbital dance is tight enough that the star always shows the same face to the pulsar, similar to how the moon is oriented to Earth.

Radiation from the pulsar has fried the near side of the companion star to a scorching 7800° Celsius, Manuel Linares of the Polytechnic University of Catalonia in Barcelona and colleagues report May 23 in the Astrophysical Journal. That’s as hot as an A-type star, which are typically around twice the mass of the sun and burn at higher temperatures. But the side facing away from the pulsar is just roughly 5400° Celsius, similar to stars like the sun.

Linares and colleagues also measured the Doppler

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