Wednesday, November 28, 2012

Naked black widow star with orbital period shorter

Although Earth takes 365 days to complete its orbit, the newly discovered pulsar does PSRJ1311-3430 in just 93 minutes, making it the neutron star in a binary system with the shortest orbital period calculated to date. It is also the first discovery of a millisecond pulsar conducted through its gamma-ray emission.

The peculiarities of this new order they are listed in the journal Science.

This type of binary systems they are popularly known as "Black Widows" because during the dance that made the pulsar and its companion star around the center of mass, the strong wind of particles emitted by the first causes the gradual vaporization second. The researcher of the Institute of Space Sciences (CSIC joint center and the Institute of Space Studies of Catalonia) Hadasch Daniela, who has participated in the work, compares this phenomenon with "the great female devours the male spider, smaller, after mating.”

One of the major characteristics of the research lies in the very nature of the find because, for the first time, is based on the gamma radiation emitted by the pulsar. Hadasch says: "So far, pulsars with millisecond rotation period could only be detected by their radio emissions."

The team led by researchers at the Max Planck Institute (Germany) has developed a new analysis method by which it was possible to monitor this type of radiation. Meanwhile, Andrea Caliandro, a researcher in the same center as Hadasch and research collaborator, comments: "The vapor cloud generated by the pulsar companion star absorbs most of their radio emissions, which has hindered its discovery ".

Caliandro confident that "the new methodology developed in this research will facilitate the discovery of these elusive stellar objects."

A fast dance

During the 93 minutes that PSR J1311-3430 takes to travel its orbit, it rotates almost 2.8 million times on itself, since its period of rotation is just 2.56 milliseconds, making it one of the fastest of the cosmos and the first to be detected through its gamma radiation.

Only about one in every million of its rotations, the pulsar emits a single photon that achieves the Fermi telescope. The research team used data collected over four years by the gamma-ray space observatory.

Meanwhile, accompanying the star PSR J1311-3430 "has proved unusually dense" says Hadasch. While its diameter is only 88,000 kilometers, approximately 60% of the size of Jupiter, its mass is about eight times that of the planet. These figures give it a density 30 times that of the Sun

This star, whose core is helium, would decrease gradually as it is heated and evaporated by the pulsar radiation. By contrast, the mass would be detached by the pulsar assimilated, increasing its rotational speed. Both partners, located in the constellation Centauries, are separated by only 520,000 kilometers, equivalent to 1.4 times the distance between Earth and the Moon.

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