Friday, February 21, 2014

Black Widow Pulsars With a deadly embrace - Video

Spinning 390 times a second, PSR J1311−3430 periodically swings its radio (green) and gamma-ray (magenta) beams past Earth in this artist's concept. 

The pulsar heats the facing side of its stellar partner to temperatures twice as hot as the sun's surface and slowly evaporates it. 

Credit: NASA's Goddard Space Flight Center

Black widow spiders and their Australian cousins, known as redbacks, are notorious for their tainted love, expressed as an unsettling tendency to kill and devour their male partners.

Astronomers have noted similar behaviour among two rare breeds of binary system that contain rapidly spinning neutron stars, also known as pulsars.

Roger Romani
"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.

The Kavli institute is operated jointly by Stanford and SLAC National Accelerator Laboratory in Menlo Park, Calif.

Black widow systems contain stars that are both physically smaller and of much lower mass than those found in redbacks.

So far, astronomers have found at least 18 black widows and nine redbacks within the Milky Way, and additional members of each class have been discovered within the dense globular star clusters that orbit our galaxy.

Learn how astronomers discovered PSR J1311−3430, a record-breaking black widow binary and the first of its kind discovered solely through gamma-ray observations. 

Credit: NASA's Goddard Space Flight Center

One black widow system, named PSR J1311-3430 and discovered in 2012, sets the record for the tightest orbit of its class and contains one of the heaviest neutron stars known.

The pulsar's featherweight companion, which is only a dozen or so times the mass of Jupiter and just 60 percent of its size, completes an orbit every 93 minutes, less time than it takes to watch most movies.

Initial estimates put the neutron star at about 2.7 solar masses, but more recent studies allow a range of values extending down to 2 solar masses, still among the highest-known for neutron stars.

When a massive star explodes as a supernova, the crushed core it leaves behind – a neutron star—squeezes more mass than the sun into a ball no larger than Washington, D.C.

When young, an isolated neutron star rotates tens of times each second—or a few thousand revolutions per minute, and generates beams of radio, visible light, X-rays and gamma rays that astronomers observe as pulsed emission whenever the beams sweep past Earth.

They also generate powerful outflows, or "winds," of high-energy particles. The power for all this derives from the neutron star's rapidly spinning magnetic field, and over time, as solitary pulsars wind down, their emissions fade.

Thirty-two years ago, astronomers discovered a new, much faster class of pulsars. With rotation periods of 10 milliseconds or less, these neutron stars spin at astonishing speeds, up to 43,000 rpm.

Today, more than 300 of these so-called millisecond pulsars have been cataloged. While young pulsars usually appear in isolation, more than half of millisecond pulsars have a stellar partner, suggesting that interactions with a normal star can rejuvenate an older, slower neutron star.

But how did isolated millisecond pulsars get their groove back?

Enter black widows and their kin.

Read the full article here

No comments:

Post a Comment