#### Serendipity

##### Well-Known Member

See Object spotted speeding through the universe after being thrown out by a black hole

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See Object spotted speeding through the universe after being thrown out by a black hole

The thing I can't get my head around is the speed of the thing - 1,700km per second!

This can happen, hurled by a black hole, that's a galactic fastball.

So, if you see that thing coming right at you, with its breakneck speed of 1,700km/sec, and assuming for simplicity sake this star has about the same diameter as our sun (1,393,000km), you will need to move (1,393,000/2)=696,500km aside to get out of its way (not mentioning heat or radiation). The sun will need 696,500/1,700 = 409.7 seconds to cover that distance.The thing I can't get my head around is the speed of the thing - 1,700km per second!

Just don't wait too long is all I'm saying.

Not science fiction, but I am trying to write a non-fiction book about the latest discoveries in space science, and what that means for us.so who's up for writing a bit of science fiction about this?

In this example, it's simply the latest of a number of "high velocity stars" that have been recently detected. There's now a section on Wikipedia about them: Stellar kinematics - Wikipedia

I'd like to know when your book on space discoveries is published.Not science fiction, but I am trying to write a non-fiction book about the latest discoveries in space science, and what that means for us.

In this example, it's simply the latest of a number of "high velocity stars" that have been recently detected. There's now a section on Wikipedia about them: Stellar kinematics - Wikipedia

Black holes don't ever throw out anything? Isn't that the very nature of what a black hole is?

It would have to orbit it too fast and be slungshot...? , once pulled in there'd be no escape.

*Now I await the true experts to be thoroughly refuted....*

Actually reasonably slow.The thing I can't get my head around is the speed of the thing - 1,700km per second!

Let me explain.

The escape velocity of an object to leave our solar system, from the vicinity of the Earth, is approximately 42 km/s.

The equations for escape velocity are proportional to the square root of the mass of the object you want to escape and the inverse of the distance.

So, Saggitarius A is about 4 million times more massive than our sun. Therefore if you were at 1 Astronomical unit from the black hole, you would need to increase your velocity by 2000 times, or ~84,000 km/s to escape the system!

This star is 'only' doing 1,700 km/s! This seems to imply that this star must at about 2,500 A.U. away from the black hole for it to be flung out. That seems a lot...but remember that 1 light year is 63,241 A.U. so it's still 'in the neighbourhood' in astronomical terms.

Still can't get my head around it, VB.Actually reasonably slow.

Let me explain.

The escape velocity of an object to leave our solar system, from the vicinity of the Earth, is approximately 42 km/s.

The equations for escape velocity are proportional to the square root of the mass of the object you want to escape and the inverse of the distance.

So, Saggitarius A is about 4 million times more massive than our sun. Therefore if you were at 1 Astronomical unit from the black hole, you would need to increase your velocity by 2000 times, or ~84,000 km/s to escape the system!

This star is 'only' doing 1,700 km/s! This seems to imply that this star must at about 2,500 A.U. away from the black hole for it to be flung out. That seems a lot...but remember that 1 light year is 63,241 A.U. so it's still 'in the neighbourhood' in astronomical terms.

Space is empty-ish and the speed of light is much, much faster. I suppose I've just got used to throwing things about at vast speeds in my physics imaginationStill can't get my head around it, VB.

Ok. Well this recent thread by @Daysman shows how light from the sun takes 45 minutes to reach Jupiter, travelling at 300 000 km a second. So divide that by 1700km per second -- or multiply it or whatever.

Someone do the math, just don't ask me -- how long would this rogue star take to reach Jupiter, if launched from the sun?

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Visualizing the speed of light...

I get five-and-a-half days? So ... not so very fast really, in the eventual scheme of things?

Someone do the math, just don't ask me -- how long would this rogue star take to reach Jupiter, if launched from the sun?

Something Google threw at me today... https://www.visualcapitalist.com/visualizing-the-speed-of-light-fast-but-slow/

www.sffchronicles.com

I get five-and-a-half days? So ... not so very fast really, in the eventual scheme of things?

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I used Excel and some very wonky numbers, but about 130 hours.Ok. Well this recent thread by @Daysman shows how light from the sun takes 45 minutes to reach Jupiter, travelling at 300 000 km a second. So divide that by 1700km per second -- or multiply it or whatever.

Someone do the math, just don't ask me -- how long would this rogue star take to reach Jupiter, if launched from the sun?

## Visualizing the speed of light...

Something Google threw at me today... https://www.visualcapitalist.com/visualizing-the-speed-of-light-fast-but-slow/www.sffchronicles.com

I get five-and-a-half days? So ... not so very fast really, in the eventual scheme of things?

1700 km/s is about 0.5% the speed of light, so there's a fair difference.

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However, Googling tells me it is in fact. 778,547,200km.

778,547,200 / 1,700 = 457,968.9 sec = 7,632.8 mins = 127.2 hrs = 5.3 days.

Or 300,000 / 1,700 = 176.47 * 45 mins = 7,941.1 mins = 132.3 hrs = 5,5 days.

A difference of 6hrs, but I guess the 45 mins isn't exactly right, just like the 810mln km wasn't.

Not counting acceleration.

Hopefully enough time to duck when I see it coming, lol ...

Tx for that VB, it's a change-up after all. )