[Xin (OP)]

Hi all...new member here. Was curious about something, and figured this might be the best place to find the answer:

Are there things that are immune to the effect of gravity? Black holes emit x-rays, right? So I'm assuming that x-rays are not affected by gravity, but how is that possible? I'm just a science neo-pyte, so excuse my ignorance here

Aren't x-rays, radio waves, and even light just particles? We know that light is indeed affected by Gravity, but why aren't the x-rays coming from black holes? Is Gravity (and the other forces) a particle?

-Xin

[neilep]

Hi Xin...(pronounced with a 'z' yes ?)

Welcome.

That's a great question, I am going to cover up the fact that I don't know the answer by saying that I will leave it for the experts to answer.....DOH !!

Nice Blog by the way...like you thoughts on Man creating God.

Hopefully you'll remain here a while.



Men are the same as women.... just inside out !!

[another_someone]

quote:Originally posted by Xin

Hi all...new member here. Was curious about something, and figured this might be the best place to find the answer:

Are there things that are immune to the effect of gravity? Black holes emit x-rays, right? So I'm assuming that x-rays are not affected by gravity, but how is that possible? I'm just a science neo-pyte, so excuse my ignorance here

Aren't x-rays, radio waves, and even light just particles? We know that light is indeed affected by Gravity, but why aren't the x-rays coming from black holes? Is Gravity (and the other forces) a particle?

-Xin

X-rays are not immune to gravity.

X-rays do not leave black holes.

As things fall into black holes, in their death throws, they emit x-rays.  We do not see them once they enter a black hole, only up the the point of falling in.

The most common case of large amounts of x-rays from black holes are when a black hole is twinned with an ordinary star, each orbiting around each other as a binary pair.  As the black hole strips the gasses from the surface of the ordinary star, those gasses accelerate as they pass through the event horizon, and it is those gases that are emitting the x-rays.

George

[neilep]

THANK You for the explanation George !

Is it possible for a star or any other body to orbit a black hole indefinitely ? or will it always devour it's satellites ?

Just before I press submit I'm just pondering if a body could orbit a black hole reliably, especially with all that stellar stuff falling into it !

Men are the same as women.... just inside out !!

[another_someone]

quote:Originally posted by neilep

Is it possible for a star or any other body to orbit a black hole indefinitely ? or will it always devour it's satellites ?

Just before I press submit I'm just pondering if a body could orbit a black hole reliably, especially with all that stellar stuff falling into it !

I cannot see any reason why, if the orbital velocity is right, it should not orbit indefinitely.  The only thing I am not sure of is if tidal forces will effect the orbital speed.

While a star is burning, it will be throwing off exhaust gases (or Sun is sending a constant stream of high speed gas past the planets of the solar system), and this will be sucked into the companion black hole.

It all depends a lot on how close the star and black hole are.  A star close to a black hole will be more effected by tidal forces than a star orbiting at a greater distance.

But, apart from vague descriptions, this is getting out of my depth, and really needs Ian to answer (who I see has not posted since the 21st – maybe he's on holiday).

George

[Xin (OP)]

Thanks Neil! Yeah Xin is pronounced with a "z"...a play on the word "Zen". And thanks for the comment about my blog. I love thinking of odd ideas and generally being cryptic. Having a Creative Writing degree will do that Which is why I've joined this forum. I've been lurking and became fascinated with all the neat things I can learn here that ought to help me create more realistic and interesting stories/ideas for my blog.

And thanks George for the lesson. I had always thought Black Holes were detectable because they beamed out x-rays like how stars produce light. So I guess, as far as we know, there is no known particle, wave, etc. that is immune to the effects of gravity?

[another_someone]

quote:Originally posted by Xin

So I guess, as far as we know, there is no known particle, wave, etc. that is immune to the effects of gravity?

As far as current theory stands, if it has energy, it must be susceptible to gravity.

George

[Ray hinton]

is that right that a lot of black holes are only detected,because of the effect they have on things around them.

measure twice,cut once.

[another_someone]

There is absolutely no way of being certain a black hole exists.

The only property one can see of a black hole is its gravitational field, and one can only see that gravity by the effect it has on surrounding matter.  If one sees a strong gravitational field in a compact space and nothing there that is visible, then it assumed to be a candidate for a black hole.

http://imagine.gsfc.nasa.gov/docs/science/know_l2/black_holes.html

quote:

If We Can't See Them, How Do We Know They're There?

Since black holes are small (only a few to a few tens of kilometers in size), and light that would allow us to see them cannot escape, a black hole floating alone in space would be hard, if not impossible, to see. For instance, the photograph above shows the optical companion star to the (invisible) black hole candidate Cyg X-1.
However, if a black hole passes through a cloud of interstellar matter, or is close to another "normal" star, the black hole can accrete matter into itself. As the matter falls or is pulled towards the black hole, it gains kinetic energy, heats up and is squeezed by tidal forces. The heating ionizes the atoms, and when the atoms reach a few million degrees Kelvin, they emit X-rays. The X-rays are sent off into space before the matter crosses the Schwarzschild radius and crashes into the singularity. Thus we can see this X-ray emission.
Binary X-ray sources are also places to find strong black hole candidates. A companion star is a perfect source of infalling material for a black hole. A binary system also allows the calculation of the black hole candidate's mass. Once the mass is found, it can be determined if the candidate is a neutron star or a black hole, since neutron stars always have masses of about 1.5 times the mass of the sun. Another sign of the presence of a black hole is random variation of emitted X-rays. The infalling matter that emits X-rays does not fall into the black hole at a steady rate, but rather more sporadically, which causes an observable variation in X-ray intensity. Additionally, if the X-ray source is in a binary system, the X-rays will be periodically cut off as the source is eclipsed by the companion star. When looking for black hole candidates, all these things are taken into account. Many X-ray satellites have scanned the skies for X-ray sources that might be possible black hole candidates.
Cygnus X-1 is the longest known of the black hole candidates. It is a highly variable and irregular source with X-ray emission that flickers in hundredths of a second. An object cannot flicker faster than the time required for light to travel across the object. In a hundredth of a second, light travels 3000 kilometers. This is one fourth of Earth's diameter! So the region emitting the x-rays around Cygnus X-1 is rather small. Its companion star, HDE 226868 is a B0 supergiant with a surface temperature of about 31,000 K. Spectroscopic observations show that the spectral lines of HDE 226868 shift back and forth with a period of 5.6 days. From the mass-luminosity relation, the mass of this supergiant is calculated as 30 times the mass of the Sun. Cyg X-1 must have a mass of about 7 solar masses or else it would not exert enough gravitational pull to cause the wobble in the spectral lines of HDE 226868. Since 7 solar masses is too large to be a white dwarf or neutron star, it must be a black hole.

However, there are arguments against Cyg X-1 being a black hole. HDE 226868 might be undermassive for its spectral type, which would make Cyg X-1 less massive than previously calculated. In addition, uncertainties in the distance to the binary system would also influence mass calculations. All of these uncertainties can make a case for Cyg X-1 having only 3 solar masses, thus allowing for the possibility that it is a neutron star.
Nonetheless, there are now about 10 binaries for which the evidence for a black hole is much stronger than in Cygnus X-1. The first of these, an X-ray transient called A0620-00, was discovered in 1975, and the mass of the compact object was determined in the mid-1980's to be greater than 3.5 solar masses. This very clearly excludes a neutron star, which has a mass near 1.5 solar masses, even allowing for all known theoretical uncertainties. The best case for a black hole is probably V404 Cygni, whose compact star is at least 10 solar masses. With improved instrumentation, the pace of discovery has accelerated over the last five years or so, and the list of dynamically confirmed black hole binaries is growing rapidly.

George

[ukmicky]

Gravity has no effect on the photon. Gravity affects the space that the photon is travelling through which affects us as the observer, but as far as the photon is concerned which is travelling through the bent space its totally unaffected.its feeling no pull of gravity its still travelling in a straight line and still travelling at the speed of light.

its our view of it through distorted space which is distorted by gravity.

[another_someone]

quote:Originally posted by ukmicky

Gravity has no effect on the photon, gravity only affects the space that the photon is travelling through . the bending of space can change how we view the photon ie its frequency  (gravitational redshift).however as far as the photon is concerened which is travelling through the bent space its tollally unaffected, its our view of it through distorted space which is distorted

Michael

But is not that also equally true for the effects of gravity on anything.  The relativistic view of gravity is that it is not a force, in the conventional sense (hence why it is so difficult to integrate into quantum theory), but is merely a warping of space – but this is not something that is exceptionally true of a photon.

The discussion had avoided relativity insofar as anything that differs between relativistic and non-relativistic perspectives is within this context more quantitative rather than qualitative in its observable effects.

George