Context: NASA’s James Webb Space Telescope is providing insights into the chaotic events unfolding around the supermassive black hole Sagittarius (Sgr) A*, at the center of our Milky Way galaxy.
Relevance of the Topic: Prelims: Sagittarius (Sgr) A*; Terms associated with black holes; James Webb Space Telescope.
Major Highlights:
- James Webb has allowed astronomers to observe the region around the black hole Sagittarius (Sgr) A*, for extended periods for the first time.
- The region around Sgr A* was seen active, rather than remaining in a steady state.
- A constant flickering of light from its accretion disk (swirling disk of gas surrounding the black hole) and occasional bright flares were observed.
- Significance: The observations are providing insight into how black holes interact with their surrounding environments.
About Sagittarius A*
- Sagittarius (Sgr) A* is the supermassive black hole at the Galactic Center of the Milky Way.
- Supermassive black holes are found at the centres of most galaxies including the Milky Way.
- Their origin is not exactly understood, but may involve accretion of matter, merger or collapse of massive gas clouds.
- Their masses range from millions to billions of times the sun’s mass.
- Sgr A* possesses roughly four-million-times the mass of our sun and is located about 26,000 light years from the Earth.
- Sgr A* is a bright and very compact astronomical radio source. It is not as active as some at the centres of other galaxies.
What are Black Holes?
- Black holes are the regions of spacetime where gravity is so strong that nothing (including light and other electromagnetic waves) has enough energy to escape. The boundary of no escape is called the event horizon.
- Formation: A black hole forms when a massive star (at least three times the mass of our Sun), exhausts its fuel, explodes in a supernova, and collapses under gravity into an incredibly dense core called a singularity.
Key terms related to black holes
| S.No. | Terms | Description |
| 1. | Singularity | - The centre of a black hole is a gravitational singularity. It is a point where the predictions of general theory of relativity do not apply. |
| 2. | Accretion Disc | - Accretion disc is a flat, rotating structure of matter (gas, dust, or other material) that forms around a black hole. The material in the accretion disc spirals inwards due to the gravitational attraction of the black hole. - As the matter spirals inward, it gets heated up due to friction and emits various forms of electromagnetic radiation (including visible light, X-rays, gamma rays and radio waves). - About 90% of the accretion disk’s material falls into the black hole, while the rest is ejected back into space. |
| 3. | Event Horizon (a point of no return) | - The event horizon is like a boundary around a black hole (around the singularity). - Once anything (matter, energy, light) crosses this boundary, it can not escape unless it travels faster than the speed of light (which is impossible). |
| 4. | Ergosphere | - The Ergosphere is a bigger sphere, outside the event horizon of a black hole, where matter can enter and then return (escape the black hole's gravitational pull), if they are moving with speeds very close to the speed of light. |
About James Webb Space Telescope (JWST)
- World’s most advanced telescope launched in 2021 designed to conduct infrared astronomy.
- It is the largest infrared telescope ever built (6.5 metre primary mirror). It detects near-infrared and mid-infrared wavelengths to observe faint and distant objects.
- Location: Orbits the Sun at L2 Lagrange point (1.5 million km from Earth)
- It is equipped with high-resolution and high-sensitivity instruments, enabling investigations such as:
- observation of the first stars and the formation of the first galaxies (almost to the beginning of the universe.
- detailed atmospheric characterisation of potentially habitable exoplanets.
- JWST can see further than Hubble Telescope and is considered as its successor.
- Collaborative Project of: National Aeronautics and Space Administration, European Space Agency and Canadian Space Agency.
