• Using NASA’s James Webb Space Telescope, a team of astrophysicists has gained the longest, most detailed glimpse yet of a supermassive black hole at the center of the Milky Way.

• They found that the swirling disk of gas and dust (or accretion disk) orbiting the central supermassive black hole, called Sagittarius A*, is emitting a constant stream of flares with no periods of rest. 

• While some flares are faint flickers, lasting mere seconds, other flares are blindingly bright eruptions, which spew daily. There also are even fainter changes that surge over months.

• To conduct the study, researchers used Webb’s NIRCam (Near-Infrared Camera) to observe Sagittarius A* for a total of 48 hours in 8 to 10-hour increments across one year. This enabled them to track how the black hole changed over time.

• The new findings could help physicists better understand the fundamental nature of black holes, how they get fed from their surrounding environments, and the dynamics and evolution of our own galaxy.

• The study was published in The Astrophysical Journal Letters.

What is a black hole?

• A black hole is born when a large star collapses in on itself. Far from being a “hole”, they are instead incredibly dense objects with a gravitational pull so strong that nothing, not even light, may escape them. As they suck in matter such as gas, dust and space debris, they form an accretion disk — a churning mass of super-accelerated particles that are among the brightest objects in the Universe — around them.

Scientists generally believe that there are two types of black holes. The more common stellar black holes — up to 20 times more massive than the Sun — form when the centre of a very big star collapses in on itself.

• Supermassive black holes are at least a million times bigger than the Sun and their origins are uncertain.

James Webb Space Telescope

• James Webb Space Telescope (JWST) is the world’s premier space science observatory. It is the largest, most powerful space telescope ever built.

• JWST was launched on December 25, 2021 on an Ariane 5 rocket from Europe’s Spaceport in French Guiana, South America.

• It reached its lookout point 1.6 million kilometers from Earth in January 2022.

• Then the lengthy process began to align the mirrors, get the infrared detectors cold enough to operate and calibrate the science instruments, all protected by a sunshade the size of a tennis court that keeps the telescope cool.

• It is designed to answer fundamental questions about the universe and to make breakthrough discoveries in all fields of astronomy.

• A joint effort with ESA (European Space Agency) and the Canadian Space Agency, the Webb observatory is NASA’s revolutionary flagship mission to seek the light from the first galaxies in the early universe and to explore our own solar system, as well as planets orbiting other stars. 

• JWST is the scientific successor to the iconic Hubble and Spitzer space telescopes. It is built to complement and further the discoveries of Hubble, Spitzer, and other NASA missions by accessing the near infrared and mid-infrared wavelengths with unprecedented resolution. 

• It is named after NASA’s second administrator, James E. Webb, who headed the agency during part of the Apollo era, from February 1961 to October 1968. The mission was previously known as the Next Generation Space Telescope (NGST).

• JWST is about 100 times more sensitive than Hubble and is expected to transform understanding of the universe and our place in it.

• JWST carries four state-of-the-art science instruments with highly sensitive infrared detectors of unprecedented resolution. It studies infrared light from celestial objects with much greater clarity than ever before.

(The author is a trainer for Civil Services aspirants.)