Indian astronomers discover stars hotter than Sun

Sun is hot, really hot. The surface of the sun is burning at more than 5000 degrees Celsius. At the core, it is even hotter. But group of Indian astronomers have now found stars that are hotter than the Sun.

These stars, eight in all, belong to a rare class called 'MRPs' or Main-sequence Radio Pulse emitters. The Pune-based astronomers have discovered the stars by using Giant Metrewave Radio Telescope (GMRT) located near Pune.

The group of scientists, led by astronomers from the Pune-based National Centre for Radio Astrophysics (NCRA), discovered the rare class of radio stars that are hotter than the Sun with unusually strong magnetic fields and much stronger stellar wind, it said. In a press release, the NCRA said the team had also discovered three more such stars in the past using the GMRT. Thus, of the total 15 MRPs known so far, 11 were discovered with the GMRT, of which eight were discovered in 2021 alone, thanks to the wide bandwidth and high sensitivity of the upgraded GMRT, the release said. "These discoveries are the fruits of an ongoing survey with the GMRT, which was launched specifically for the purpose of solving the mystery of MRPs," it said. 

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The success of the GMRT programme has revolutionised the notion about this class of stars, and has opened up a new window to study their exotic magnetospheres, the NCRA said. 

The MRPs are stars hotter than the Sun with unusually strong magnetic fields, and much stronger stellar wind. Due to this, they emit bright radio pulses like a lighthouse, the research outfit said. Though the first MRP was discovered in 2000, it was only due to the high sensitivity of the upgraded GMRT (uGMRT) that the number of such stars known have increased multiple times in recent years, with 11 of the 15 discovered using the high-tech telescope, the NCRA said. 

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The success of the survey with the uGMRT suggest that the current notion that MRPs are rare objects may not be correct. Rather, they are probably more common, but are difficult to detect, it said. This is due to the fact that the radio pulses are visible only at certain times, and the phenomenon is mostly observable at low radio frequencies, the release said. 

"This is the frequency range where the uGMRT stands out as the most sensitive telescope in the world. The high sensitivity of the uGMRT and its ability to make high resolution images were instrumental in enabling the recovery of the pulsed signal from the different types of radiation coming from the sky. 

"This, combined with a strategic observation campaign, allowed the astronomers to overcome the difficulties, and reveal the true nature of these objects," the release said.

(With inputs from agencies)