Syllabus: GS3/Space
Context
- The researchers presented a new method to measure the properties of black holes by using the effects they have on light flowing around them (Light Echo).
What is a Black Hole?
- A black hole is an extremely dense object whose gravity is so strong that nothing, not even light, can escape it.
- It does not have a surface, like a planet or star. Instead, it is a region of space where matter has collapsed in on itself.
- This catastrophic collapse results in a huge amount of mass being concentrated in an incredibly small area.
- Formation: A black hole is formed when a really massive star runs out of fuel to fuse, blows up, leaving its core to implode under its weight to form a black hole.
- The centre of a black hole is a gravitational singularity, a point where the general theory of relativity breaks down, i.e. where its predictions don’t apply.
- A black hole’s great gravitational pull emerges as if from the singularity.
Light Echo
- A light echo is a phenomenon in which light from a distant astronomical source (such as a star, supernova, or active galactic nucleus) reflects off nearby structures, such as interstellar dust clouds, and returns to Earth after a delay.
- Significance:
- Thus, according to the study, scientists can use light echoes as a new and independent way to the masses and spins of black holes.
- The task of measuring a black hole’s mass and spin is quite tedious because all the matter, hot gases, and the radiation swirling around the object complicate observations and make signals harder to extract from the noise.
- Light is affected differently and light echoes could offer a better signal-to-noise ratio.
| Do You Know? – Known black holes fall into two classes: 1. Stellar mass: around 20 times the Sun’s mass or more; 2. Supermassive: 100,000 to billions of times the Sun’s mass; 3. Middleweight black holes may exist between these classes, but none have been found to date. – Spaghettification: As objects approach the event horizon of a black hole, they’re horizontally compressed and vertically stretched, like a noodle. – Sagittarius A*: Sagittarius A* is more than 25,000 light years from Earth – nearest supermassive black hole, with an estimated mass millions of times that of the Sun. 1. Often abbreviated by researchers to Sgr A* (pronounced “Sagittarius A star”), it sits in the constellation of Sagittarius at the heart of the Milky Way. |
Rotating Black Hole
- A rotating black hole is also called a Kerr black hole.
- There are two event horizons, the outer and the inner.
- The region of space in-between the two horizons is the ergosphere.
- Anything inside the ergosphere will be dragged by the black hole and rotate with it but it can still escape.
- However, anything inside the inner event horizon can never escape.
- Scientific Significance: We can extract rotational energy from a rotating black hole.
- If something is sent inside of the ergosphere, and split it up into two parts, one goes in the black hole while the other comes out.
- The part coming out can be made to have a much higher speed, hence higher energy.
Source: TH
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