LOL!! This post makes for some good, informative reading. I guess Freelancer attracts a lot of astrophysicists =).

FYI I did find a file labeled "Black Hole" in my Freelancer folder, the stuff inside made some refercence to the Omega 13 system, which doesn't exist as far as I know.

Oh, and I won't debate black holes with you guys. I find it immensely interesting, but it's not my specialty. = ).

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But wouldn't the überhuge black hole like "suck" away all the stars? (Hell, I don't really know that much about this, but that's why I'm so interested, I wanna learn)

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While I'm sure there are plenty of posts on this subject, here's the basic info again.

Black holes can be viewed as the same as any other celestial bodies such as stars and planets. Any object in orbit stays in orbit and cannot tell from the gravitational force if it is indeed orbiting a black hole.

All the "sucking away" and "relativity" are noticeable near (very near) the black hole's vicinity. As an example, if our sun were to turn into a black hole right now, we won't notice any difference for about 10 minutes, then the sky turns black, and that's about it. Nothing else would happen (albeit it'll get very cold).

Edited by - Zamboni on 13-04-2003 17:22:52

Hi Ferror,

The NUKER team of astronomers have a website with data and observations they gathered with various instruments like the Hubble Space Telescope: http://www.noao.edu/noao/staff/lauer/nuker.html

Very interesting reading on what they are finding in the center of galaxies.

If you wonder why a supermassive black hole in the center of a galaxy isn't sucking everything up into it, all you need to do is understand a little bit about orbital mechanics. Here's the easy explanation:

The stars orbiting a black hole do not fall in because they have enough forward speed to sustain their orbits. The best analogy is the Space Shuttle-- When the shuttle needs to de-orbit and re-enter Earth's atmosphere, it has to fire retrorockets to slow down its forward speed to cause its orbit to decay , so it will spiral in and fall towards the earth.

What the NUKER team is finding is that the stars near the center of the galaxy are orbiting something invisible at VERY fast speeds. That's why they are not falling into the supermassive black hole.

From the period of the stars' orbit (how fast it takes to complete one circle) and how much do those stars weigh, one can calculate the gravitational force keeping them in those orbits. And from the gravitational force, one can calculate the mass of the invisible object. It works out to an object with the mass of a few million suns-- A supermassive black hole.

Just like Zamboni says, outside the black hole's event horizon, the gravity from black holes are not different from the gravity of a star. The gravity still obeys Newton's laws and orbital mechanics still apply.

Hope this helps.



Edited by - Chandrasekhar Limit on 13-04-2003 22:58:27

So actually it's just like our solarsystem, exept the sun being the supermassive blackhole, and the planets being the stars?

I know I'm dumb, but you spoke of "blackholes absorbing time & space". If their gravity can even absorb time, why are the stars unaffected?

"So actually it's just like our solarsystem, exept the sun being the supermassive blackhole, and the planets being the stars?"

Yes, in essence, the Milky Way galaxy is a macro-sized version of our solar system (an oversimplification, but it'll do).

Stars are not affected because the really WEIRD phenomena described by general relativity only occur around the singularity, which lies INSIDE the black hole's event horizon.

> blackholes absorb time and space

to Ferror:

That wasn't something I wrote (at least I don't see it in my posts above, heh heh).

That whole deal with blackholes destroying time and space happens ONLY inside the event horizon (where light can't escape). Outside the event horizon, one can treat a black hole's gravity just like that of any other star.

Outside the event horizon, what gravity more accurately does is *distort* space and time, NOT "absorb". This is an occurrance with all objects with mass.

A good example would be our very own sun-- It is very massive, so it exerts a lot of gravitational force on all objects around it. And the effects of its gravity distorting space and time can be seen-- Light from stars are bent as they pass by the sun (due to the distortion in space-time), which changes the stars' apparent position in the sky. This has been confirmed by astronomers during solar eclipses when the glare of the sun is a bit less so some stars can be seen.

We can actually use this phenomenon to our advantage. Recently, the Hubble Space Telescope used this "gravitational microlensing" effect to photograph galaxies 12 billion light years away, using a more nearby galaxy as a gravitational lens to "focus" the image. Very interesting indeed.

Here are some links:

How the Chandra X-ray observatory was used to detect the supermassive black hole at the center of our galaxy: http://www.space.com/scienceastronomy/c ... 30106.html

How the Hubble used gravitational microlensing to take photos of faraway galaxies: http://www.newscientist.com/news/news.jsp?id=ns99993244

To answer your other question, yes indeed basically all the other stars in the galaxy orbit around that super massive black hole at the center like a macro version of the solar system.

HTH!




Edited by - Chandrasekhar Limit on 14-04-2003 00:56:14

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but you spoke of "blackholes absorbing time & space".

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Blackholes do not "absorb" time nor space. A black hole only bends space time.
If you want more deatils or explanations, I suggest you read books. Here are a few suggestions:
A Brief History of Time - Stephen Hawking
Hyper Space - Michio Kaku
Black Holes, Wormholes & Time Machines - Jim Al-Khalili

There are numerous other ones that I can't name off the top of my head... But the few books above should quell your curiosity.

Ok.... here is the deal.


all of these are possiblities for a dead star.....

Brown dwarf

stars that are too small to cause exotic gravitational collapse end up here. Ball of cooling hydrogen and helium.

White dwarf

the star is held in ballence by electron pressure. it is about the size of a planet. if the collapsed star was originally <1 solar mass it will become a white dwarf.

Nutron star

The star is held in place by atomic pressure (all of the atomic nuclui are touching) . In essence it is just a big ball of nutrons.... or if you want to think of it as one really really big atom. It is about the size of a city. this will happen if the star was originally >1 solar mass but less then 3 solar masses.

Quark star (this one is theoritical... science must speculate)

The star is held in place by Quark pressure. Quarks are the particals that make up protons and nutrons. quark stars are really small and very heavy. You don't want one of these landing on your foot. the star would be around 2.75 solar masses. This is a rare one bub.

Black Hole

Nothing is strong enough to hold up equilibrium. It just collapese into a singularity. Things are NOT sucked in like a movie. things will orbit it just fine.

Red Dwarf (not a collapsed star)

A really cool smeged up show from the UK.



geeked out astronomy student,
Poly

Greetings, fellow astronomy enthusiast.

Good definitions you provided there, except one:

The current theory behind Brown Dwarfs are that they were never stars to begin with because they do not have enough mass to cause enough gravitational pressure to fuse plain stock 1-proton-0-neutron hydrogen. Basically these would be gas giants with up to 12 Jupiter masses I think (I'll have look that up).

The more massive BDs can fuse some Deuterium and Tritium though because those fuse more easily than stock Hydrogen, but those are very small quantities compared to stock Hydrogen, and so they have a residual infrared signature but emit no visible light.

So basically Brown Dwarfs were stillborn and never became stars, or so the current evidence and theory suggests..