Astrosat solves cosmic puzzle involving 7 bn-year-old star cluster

 India's first space observatory, Astrosat, has solved a cosmic puzzle involving a 7 billion-year-old star cluster located in a far corner of the universe.

An on-board instrument known as UVIT (ultra-violet imaging telescope), with an extraordinary ability to look at the stars and galaxies, helped researchers solve the riddle which baffled the scientific community for a decade.

A star in the cluster NGC 188 has been a puzzle as it is red in visible light, implying that it is a cool star, but it is dazzling in UV, which implies that it is very hot at the same time. “Now, with Indian UVIT data, scientists have nailed the problem — it turns out that this star is actually a binary system, of a hot and a cool star,” Biman Nath, an astrophysicist at the Raman Research Institute, Bengaluru, told DH.

The first set of scientific results from the Astrosat mission were presented before the Indian scientific community last week at a meeting of the Astronomical Society of India at Srinagar. Nath is the chairman of the scientific organising committee, which reviewed these results before they were presented.

Detected first in 1995, the cosmic riddle involves stars that belong to the class of “sub-dwarf”. It remained a mystery from the beginning.

Astrosat data showed that these 2 stars were not individual stars, but binaries. This means each one is found to be consisting of a very hot star and a cooler star. The properties of the hot component were also derived using the Indian data, for the first time.

“The evolutionary process of these 2 systems is being studied based on the data collected by the UVIT and ground-based telescopes. The Astrosat would aid in solving many such mysteries in future,” said Annapurni Subramanian, professor, Indian Institute of Astrophysics, Bengaluru, who was part of the team that analysed the UVIT data.

Launched on September 28, 2015, the Indian space observatory spent just about 7 months in space and has begun to show its ability to the scientific community.

Other instruments on-board Astrosat too are throwing up exciting observations. For instance, the hard X-ray instrument CZTI witnessed a gigantic gamma ray burst soon after the window of the telescope was opened.

Apart from the expected results, Astrosat found out additional surprising information for the astronomers. “For the next 10 years, it would be the best X-ray instrument in space,” Nath said.