Why is it in the News?

Northwestern University recently confirmed that the brightest gamma-ray burst ever recorded, GRB 221009A, was caused by the collapse and explosion of a massive star.

About GRB 221009A:

• GRB 221009A, also known as Swift J1913.1+1946, is the brightest gamma-ray burst ever detected, estimated to be ten times brighter than the previous record holder.
• The burst itself lasted around seven minutes, but its effects were observable for over ten hours.
• GRB 221009A originated from a galaxy estimated to be 2.4 billion light-years away, yet it was powerful enough to influence Earth's atmosphere.
• This exceptionally bright burst emitted across a vast range of the electromagnetic spectrum, providing a unique opportunity for scientists to study this rare phenomenon in detail.
• The cause of the burst is attributed to the collapse of a massive star, but scientists are still investigating why it was so much brighter than other gamma-ray bursts.

What are Gamma-ray Bursts?

• Gamma-ray bursts (GRBs) are the most powerful explosions in the universe.
• These brief flashes of high-energy light result from some of the universe's most explosive events, including the birth of black holes and collisions between neutron stars.
• Lasting a few milliseconds to several minutes, GRBs can be hundreds of times brighter than an average supernova, making them as luminous as a million trillion suns.
• Thus, when a GRB erupts, it briefly becomes the brightest source of electromagnetic radiation in the observable universe.
• Gamma Ray Bursts are difficult to study because they are so short-lived.
• They were first detected by the Vela satellites, which were designed to detect nuclear tests during the Cold War.
• It was only years after their detection that they were declassified.
• The location of gamma-ray bursts within their host galaxy and their surrounding environment informs us as to the formation and evolution of the progenitor system, providing insight into stellar evolution and star formation across the age of the universe.

What causes a gamma-ray burst?

• The cause of a gamma-ray burst depends on how long it lasts.
• GRBs that last less than two seconds are caused by the merger of two neutron stars or the merger of a neutron star and a black hole.
• Longer GRBs, which can last hours, are triggered when a massive star collapses and births a black hole.
• In both cases, GRBs result from jets of particles accelerated to around 99.9% of the speed of light.

How powerful are gamma-ray bursts?

• In just a few seconds, a gamma-ray burst can emit as much energy as the sun will put out over its entire 9 billion-year lifetime

Do gamma-ray bursts happen in the Milky Way?

• GRBs seem to be most closely associated with galaxies that are in the midst of intense star formation, a period that our galaxy seems to have matured out of 2 billion to 3 billion years ago.
• However, the Milky Way is filled with the supernova remnants that mark the deaths of massive stars, indicating that our galaxy was once home to GRBs.

Why is it in the News?

India's AstroSat space telescope has achieved a significant milestone by detecting more than 600 Gamma-Ray Burst (GRB), each marking the death of a massive star or merging of neutron stars.

About ISRO’s AstroSat:

• AstroSat is the first dedicated Indian astronomy mission aimed at studying celestial sources in X-ray, optical, and UV spectral bands simultaneously.
• One of the unique features of the AstroSat mission is that it enables the simultaneous multi-wavelength observations of various astronomical objects with a single satellite.
• AstroSat, with a lift-off mass of 1515 kg, was launched by the Indian launch vehicle PSLV from Satish Dhawan Space Centre, Sriharikota, on September 28, 2015, into a 650 km orbit inclined at an angle of 6 degrees to the equator.
• The minimum useful life of the AstroSat mission is expected to be 5 years.
• It carried a total of five scientific payloads, enabling imaging and studying the temporal and spectral properties of galactic and extra-galactic cosmic sources in a wide range of wavelengths on a common platform.
• The scientific objectives of AstroSat’s mission are:
• To understand high energy processes in binary star systems containing neutron stars and black holes.
• Estimate magnetic fields of neutron stars.
• Study star birth regions and high energy processes in star systems lying beyond our galaxy.
• Detect new briefly bright X-ray sources in the sky.
• Perform a limited deep-field survey of the Universe in the Ultraviolet region.
• At present, all the payloads are operational and are observing the cosmic sources.