India's Himalayan Telescope observes one of the most energetic objects in the universe

The Indian Astronomical Observatory located in Hanle of Ladakh has joined hands with 10 other global telescopes to observe the brightening of BL Lacertae (BL Lac), a blazar located about 950 million light years away from Earth.

A team led by post-doctoral fellow Aditi Agarwal from the Raman Research Institute has now studied the brightening of BL Lac, which was first discovered almost a century ago and has been slowly inching close to the maxima. These are compact structures showing anomalous luminosity from time to time.

The study has been published on the preprint server Arxiv and is yet to be peer-reviewed.

Astronomers had in July 2020 suspected that BL Lac was beginning to flare up and the 11 telescopes including the Himalayan Chandra Telescope located in Ladakh’s Hanle were targeted at the blazar for 84 days.

About blazar:

A blazar is a type of galaxy that is powered by a humongous black hole and is among one of the brightest and most powerful objects in the universe. They are known for emitting highly energetic particles and radiation, including gamma rays, X-rays, and radio waves.

Words from the researchers:

Researchers said that the deviation in their brightness levels can vary and last either for a few hours, days, weeks or even months. The team used the global pool of telescopes to pick up the electromagnetic emissions that are visible across the radio, microwave, infrared, optical, ultra-violet, X-ray, and gamma wavelengths.

“As time progressed, it was observed that the flare was becoming brighter gradually, indicating that BL Lac was turning more active. For the first time on August 21, 2020, BL Lac’s brightness reached its maximum. This was captured well by the Modified Dall–Kirkham telescope located in Krak³w, Poland,” said Agarwal, lead author of the paper.

"These new parameters shall form the basis for future multispectral studies of BL Lac,” Agarwal highlighted.

More insights about the observations:

The observations revealed that the brightness of BL Lac increased from magnitude 14 to 11.8 and the international team of researchers calculated the source’s magnetic field, which was found to range from 7.5 Gauss to 76.3 Gauss during the flare.

The Ministry of Science Technology in a statement said that the calculations, never possible before, were solely performed because of the availability of Terabytes of datasets obtained from the battery of the telescope.