Black Holes and their original star

In summary, black holes have a very strong gravitational pull due to their immense mass, which can be compared to the original star from a distance. However, the gravitational pull becomes irresistible at the event horizon, making it impossible for anything to escape once it crosses this point. While black holes may seem more exciting and popular in media, their true nature cannot be fully explained by Newtonian physics and they should not be portrayed inaccurately in fiction. Additionally, objects do not get "sucked in" to a black hole unless they are in a close orbit, as the black hole is relatively small and objects can miss it at a distance.
  • #1
Johnnb
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Black holes suck in everything around them. My 5 year old knows that one. It's all over TV, etc. But what about the original star? Wouldn't that have just as much gravity? Wouldn't it do the same thing with the strength? Is it just that black holes are more exciting to talk about?
 
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  • #2
Johnnb said:
Black holes suck in everything around them. My 5 year old knows that one. It's all over TV, etc. But what about the original star? Wouldn't that have just as much gravity? Wouldn't it do the same thing with the strength? Is it just that black holes are more exciting to talk about?

From a distance, the gravitational effect of a black hole is very similar to that of the original star, but you can get a LOT closer to it (remember Newtonian field is -Gm/r2 where r is the distance to the center) so the field strength gets very much stronger. In General Relativity, it doesn't just get stronger but it effectively becomes irresistible at the "event horizon", so you can't just swing round and back out again.

They don't really "suck in" things at a given distance any more than a non-black hole of the same mass, but anything that gets too close is not going to get away again.

Representations of black holes in fiction are generally totally non-scientific and should be ignored.
 
  • #3
Your comment answers my question. In essence, it sounds like black hole are just more "sexy" for the science type channels for the most part. It seems like they all have a new show about black holes every month.
 
  • #4
Johnnb said:
Your comment answers my question. In essence, it sounds like black hole are just more "sexy" for the science type channels for the most part. It seems like they all have a new show about black holes every month.

They do make interesting TV!

Its important though to remeber BH's cannot be properly described by Newtonian physics.

The crucial part to remember is that at a distance black holes gravity are the same as any other body of mass, but once something crosses the Event Horizon - even a photon, its never getting out, essentially the gravity is so extreme that all world lines lead further into the BH.
 
  • #5
One other important thing to realize about black holes is that until matter gets into a rather close orbit, they don't actually suck anything in. If you are a fast-moving bit of matter coming into the vicinity of a black hole, chances are you'll just end up missing the black hole entirely, simply because the black hole is very, very small. But if you find yourself in a relatively close orbit, well, then you'll progressively lose energy to gravitational radiation and spiral inward into the black hole.
 

FAQ: Black Holes and their original star

What is a black hole?

A black hole is a region in space where the gravitational pull is so strong that nothing, including light, can escape from it. This happens when a massive star dies and collapses in on itself, creating a point of infinite density called a singularity.

How are black holes formed from stars?

Black holes are formed when a massive star runs out of fuel and can no longer support itself against its own gravity. The star then collapses and its core becomes so dense that it creates a black hole.

Can we see black holes?

No, we cannot see black holes directly because they do not emit any light. However, we can detect their presence by observing the effects they have on surrounding matter, such as the distortion of light or the emission of X-rays.

How do black holes affect their surrounding stars and galaxies?

Black holes can have a strong influence on their surrounding stars and galaxies. They can pull in matter from nearby stars, causing them to orbit around the black hole. This matter can also form an accretion disk around the black hole, emitting strong X-ray radiation. In some cases, black holes can also merge with other black holes, releasing enormous amounts of energy in the form of gravitational waves.

Can a black hole "die"?

Black holes do not technically "die", but they can evaporate over an extremely long period of time. This process, known as Hawking radiation, occurs when particles near the event horizon of a black hole are pulled apart and one particle falls into the black hole while the other escapes. This results in a slow decrease in the black hole's mass until it eventually disappears.

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