Posted on 02/18/2006 2:19:53 AM PST by vincenteblackshadow
How big is a black hole? ------------------------ There are at least two different ways to describe how big something is. We can say how much mass it has, or we can say how much space it takes up. Let's talk first about the masses of black holes.
There is no limit in principle to how much or how little mass a black hole can have. Any amount of mass at all can in principle be made to form a black hole if you compress it to a high enough density. We suspect that most of the black holes that are actually out there were produced in the deaths of massive stars, and so we expect those black holes to weigh about as much as a massive star. A typical mass for such a stellar black hole would be about 10 times the mass of the Sun, or about 10^{31} kilograms. (Here I'm using scientific notation: 10^{31} means a 1 with 31 zeroes after it, or 10,000,000,000,000,000,000,000,000,000,000.) Astronomers also suspect that many galaxies harbor extremely massive black holes at their centers. These are thought to weigh about a million times as much as the Sun, or 10^{36} kilograms.
The more massive a black hole is, the more space it takes up. In fact, the Schwarzschild radius (which means the radius of the horizon) and the mass are directly proportional to one another: if one black hole weighs ten times as much as another, its radius is ten times as large. A black hole with a mass equal to that of the Sun would have a radius of 3 kilometers. So a typical 10-solar-mass black hole would have a radius of 30 kilometers, and a million-solar-mass black hole at the center of a galaxy would have a radius of 3 million kilometers. Three million kilometers may sound like a lot, but it's actually not so big by astronomical standards. The Sun, for example, has a radius of about 700,000 kilometers, and so that supermassive black hole has a radius only about four times bigger than the Sun.
I thank God, too, that I am not blind.
I'm confused about all of the concern about vision this morning, but if you are all thanking God, then I'll join in. Thank God for making all of this matter in all of its forms, even compressed.
Well, honestly, I found his timing for getting on board rather odd. New Freeper as of today, and his first article is about Black holes?? Hmmmmm.....
The volume of a sphere with a 3km radius is 113.1 km3; the volume of a sphere with a 30km radius is 113,097 km3. That would make it more like 1,000 times the volume.
10 x volume (1131 km3) would be a radius of 6.46 km.
The volume is irrelevant -- what is important is the force due to the mass in the black hole and the escape velocity. After a bit of algebra, you obtain the Schwarzschild radius, where R = 2 * G * Mass * c^-2. Therefore, a 10-solar-mass black hole has a radius 10 times greater than a 1-solar-mass black hole.
Thank you I see your point. But, hey would I have been right if we were talking about cheese balls? :-)
OBTW: You must be the reason I couldn't get the Freeper name I wanted back in 1998. Freegards.
Black holes suck...
Oh yeah, uh, sorry about that. I should have signed up in leet-speak.
/\/\1|<3|)
PS -- yes, you would have been right with cheese balls. One of the mysteries of black holes is how they do not behave "intuitively."
Newton never saw that coming.
Astronomer announces shortlist of stellar candidates for habitable worlds
EurekaAlert | 02/18/06 | Earl Lane
Posted on 02/18/2006 4:26:06 PM EST by KevinDavis
http://www.freerepublic.com/focus/f-news/1581281/posts
Looking for other Earths? Here’s a list
msnbc.com | 02/19/06 | Alan Boyle
Posted on 02/19/2006 3:10:25 PM EST by KevinDavis
http://www.freerepublic.com/focus/f-news/1581745/posts
Five Out of Five Researchers Agree: Earth's Solar System Special
SPACE.com | 31 March 2005 | Sara Goudarzi
Posted on 03/31/2005 7:27:51 PM EST by Heartlander
http://www.freerepublic.com/focus/f-news/1375038/posts
Typically, the most sought after characteristic of a planet is its habitability. A habitable planet has liquid water on its surface, explained Margaret Turnbull of the Carnegie Institute of Washington. Thus far, 90% of all detected alien planets have host stars that can flare and sterilize the surface of the planet. Furthermore, planets, which are that close to their host star, would be in a synchronous orbit. This means that only one side of the planet would face the host star and all potential water on that side would evaporate and go to its "dark" side.
Whoops, wrong planet. Please delete message #11.
Meet the Indian who took on Stephen Hawking
Rediff.com | August 03, 2004 10:06 IST | Rediff.com
Posted on 08/03/2004 1:16:56 AM EDT by CarrotAndStick
http://www.freerepublic.com/focus/f-news/1183887/posts
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