Most Unusual Structures In The Universe Swift J1357.2
Space

Most Unusual Structures In The Universe: Swift J1357.2

Swift J1357.2 is located almost 5,000 light-years from Earth in the constellation of Virgo. It makes a complete orbit around the center of the system’s mass in the shortest orbital period known of at this time, just in 2.8 hours. The system was discovered in 2011 and almost immediately became the subject of great interest of scientists.

In such systems (there are now about a couple dozen of them), the substance of a luminous star is pulled out by a black hole, forming an accretion disk around it. Periodically, the disk substance is heated by tidal forces and “sheds” energy in the form of a powerful flash.

An unusual feature of Swift J1357.2 is that the flash period slowly fluctuates between 2 and 10 minutes. This strange behavior has never been seen in any other object. The situation was complicated by the fact that the brightness of the flashes is about 10 thousand times less than the brightness of the faintest luminous stars, respectively, they need a powerful technique to study them.

The South African SALT telescope, which has a 10-meter diameter mirror, was used for observation. During the observation period, the telescope recorded the spectra of Swift J1357.2 with a 100-second shutter speed. The total session duration was 1 hour of net time.

“These spectra were staggering. They showed ionized helium in a state that had never been seen in such systems before. It should be dense, and hot — about 40,000 degrees. More notably, the spectral objects were shifted to blue (due to the Doppler effect), indicating that the radiation sources were moving at a speed of about 600 km/s. But we were struck by the fact that these spectral features were only visible during optical dips in the light curve. we interpreted this completely unique property as a consequence of deformation or pulsation in the inner accretion disk that rotates around the black hole at the edge of the event horizon,” says one of the study participants, Professor Phil Charles from the University of Southampton.

The primary reason for the change in the flash period is probably that the ionized gas enters the accretion disk not continuously, but in portions with a period of about 8 minutes. The reasons for this are still unclear.

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