Context:
Scientists observed a ferocious class of black holes called quasars that demonstrate “time dilation” in the early universe, showing how time then passed only about a fifth as quickly as it does today.
About Quasars:
- Quasars are extremely active supermassive black holes found at the centers of galaxies.
- They are millions to billions of times more massive than our sun.
- These black holes draw in matter with their strong gravitational pull and emit intense radiation, including high-energy particle jets.
- They are surrounded by a glowing disk of matter.
- Quasars’ brightness allows scientists to study the early stages of the universe, as they can be observed from great distances.
Findings of the Study:
- In their study, scientists looked at 190 very bright objects in space called quasars.
- These quasars were from a time about 1.5 billion years after the Big Bang, which created the universe.
- The scientists compared the brightness of these ancient quasars to the brightness of quasars we see today.
- They found that certain changes that happen in quasars today happened five times slower in the ancient ones.
- This tells us that time used to pass more slowly in the early universe compared to now.
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About Black Hole:
- A black hole is a place in space where gravity pulls so much that even light can not get out.
- The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying.
- Because no light can get out, people can’t see black holes. They are invisible. Space telescopes with special tools can help find black holes.
How Big Are Black Holes?
- Black holes can be big or small.
- Small black holes: Scientists think the smallest black holes are as small as just one atom. These black holes are very tiny but have the mass of a large mountain.
- Mass is the amount of matter, or “stuff,” in an object.
- Stellar black hole:
- Its mass can be up to 20 times more than the mass of the sun.
- There may be many, many stellar mass black holes in Earth’s galaxy. Earth’s galaxy is called the Milky Way.
- Supermassive black holes:
- These black holes have masses that are more than 1 million suns together. Scientists have found proof that every large galaxy contains a supermassive black hole at its centre.
- The supermassive black hole at the centre of the Milky Way galaxy is called Sagittarius A.
How Do Black Holes Form?
- Scientists think the smallest black holes formed when the universe began.
- Stellar black holes are made when the center of a very big star falls in upon itself, or collapses. When this happens, it causes a supernova. A supernova is an exploding star that blasts part of the star into space.
- Scientists think supermassive black holes were made at the same time as the galaxy they are in.
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News Source: The Hindu
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July 5, 2023
