The Fate of the First Known Black Hole

sciencehabit writes "Cygnus X-1 bears its name because it was the first source of x-rays found in the constellation Cygnus. In 1971, astronomers discovered that the x-rays came from the direction of a bright blue star whirling around a mysterious dark object. They speculated that the x-rays were resulting from material being torn away from the bright star and falling onto the dark object, perhaps a black hole. This year, astronomers established that Cygnus X-1 does indeed harbor a black hole, a dead star whose great gravity lets nothing, not even light, escape. Now that result has inspired a forecast for the system's future: The black hole will swallow even more mass from an unfortunate star circling it, then likely dash away on its own when its companion explodes."

Comments

There's an important lesson for physicists in this

[idontgno]

Never, ever, EVER bet against Rush. Ever.

Steven Hawking, I'm looking at you.

if black holes attract light

[decora]

then does light also attract black holes?

that is, does light exert a gravitational force on other celestial entities?

then, the next question, how fast is that force of gravity propagated?

Re:if black holes attract light

[Ambitwistor]

Light gravitates, albeit very weakly. Everything gravitates.

Changes in the gravitational field propagate at the speed of light, according to relativity theory. This has never been measured directly (although the LIGO observatory is being upgraded to hopefully do so). But the 1993 Nobel Prize in physics was awarded for astronomical work that demonstrated this indirectly.

Re:if black holes attract light

[GrumpySteen]

"Since photons contribute to the stress-energy tensor, they exert a gravitational attraction on other objects, according to the theory of general relativity."

Source

Feel free to scroll down to reference #85 for the references listings if you should want to make sure that Wikipedia has summarized them correctly.

Re:if black holes attract light

[Ambitwistor]

As another poster pointed out, photons possess energy and therefore gravitate. This is a corollary of relativistic mass-energy equivalence (E=mc^2).

Re:if black holes attract light

[Chris Burke]

Any item with mass possesses gravity. Light consists of photons, which are massless, and therefore do not exert gravity.

Any item with mass possesses gravity, and light consists of photons, which have energy and therefore mass. The mass of a system is directly proportional to its energy content, as energy is lost so too must mass. An object emitting photons is losing energy and therefore mass, an object absorbing photons is gaining energy and therefore mass.

Photons have no rest mass as far as we know, but that's not the same thing. The total mass of a system containing photons is greater, due to the photon's energy, than a system without. Photons on their own are energy, and therefore exhibit mass, however tiny, and therefore themselves bend space time.

Re:if black holes attract light

[Chris Burke]

This is a corollary of relativistic mass-energy equivalence (E=mc^2).

A lot of people (and I sympathize because I was one of them for years) mistakenly believe that E=mc^2 is about the energy content of matter, and how you could convert mass to energy via, say, matter/anti-matter annihilation. Which when thought of as converting one form of energy to another is true, but hides the deeper truth: Matter isn't just a type of energy that has mass, all energy has mass, they are really the same thing.

Re:if black holes attract light

[Ambitwistor]

The point is that gravitons are not tachyons. In all quantum theories of gravitation they're massless spin-2 particles, which travel at the speed of light.

Re:if black holes attract light

[Talderas]

Who let Keanu Reeves on Slashdot?

Come on. Speak up. I promise I will give you 10 seconds to run before the lynch mob starts.

Re:if black holes attract light

[SleazyRidr]

It's a Bill Hicks bit. I don't know what show it was part of, but I can tell you that it was sampled on the hidden track on one of Tool's albums.

Re:There's an important lesson for physicists in t

[Anonymous Coward]

I think Steven Hawking's Speak and Spell should be auto tuned to Geddy Lee's High Falshetto.....

Sounds familliar

[Anne_Nonymous]

>> that result has inspired a forecast for the system's future: The black hole will swallow even more mass from an unfortunate star circling it

So basically, they're modeling based on our economy?

Sagittarius A*

[bcrowell]

You actually don't have to be a complete kook to doubt that solar-mass bodies like Cygnus X-1 are black holes. There are all kinds of other hypothesized objects that they could be, including black stars, gravastars, fuzzballs, quark stars, boson stars, and electroweak stars. These are all long-shots, but they exist in certain reasonably well-motivated physical theories.

For skeptics, I believe the evidence is stronger that Sagittarius A* is a black hole than that Cygnus X-1 is. Sag A* is the supermassive black hole at the center of our galaxy. Sag A* has been proved by indirect but very strong evidence to have an event horizon, which is essentially the defining characteristic of a black hole. (A singularity without an event horizon would be something different; the big bang singularity is an example of that.) It may become possible in the near future to do direct imaging of Sag A*'s event horizon, which would be direct proof that it's a black hole. There are fundamental reasons why we will never be able to do anything like that with any other black hole besides Sag A*, using foreseeable technology.

Actually, the referenced paper says something else

[tlambert]

Actually, the referenced paper says something else.

They specifically talk about the LIGO II http://www.ligo.org/ gravity wave observatory. And yes, they believe that a gravity wave can be detected without having the ability to detect individual gravitons as baryonic particles.

Also, for what it's worth, it'd be possible to check one way or the other for several billion dollars worth of equipment: three large masses arranged in a scalene triangle with laser interferometers acting as a target plane, with another mass to target the plane at an angle of about 45 degrees relative to the face of the plane would either demonstrate a time base variance between the target masses -- or not. You have to keep the target masses relatively close to each other.

The speed limit on the mass after the slingshot would be about 240,000 KPH. To overcome that problem and get higher speed (we need relativistic speeds for crossing the plane), you need two more masses: one the size of the mass you sling-shotted, the other relatively smaller. From the reference frame of the large and small mass, the are effectively being dropped together onto a stationary object at 240,000 KPH. This will be enough to catapult the smaller mass up to relatavistic speeds for collision with the virtual plane. We don't care if the large slingshot mass and the large target mass survive, we just want the momentum transfer. Here's a nice little demo of the process: http://www.physics.org/interact/physics-to-go/extra-bounce/index.html

--Terry

Re:There's an important lesson for physicists in t

[Daetrin]

Invisible to telescopic eye
Infinity, the star that would not die

All who dare to cross her course
Are swallowed by a fearsome force

Re:Actually, the referenced paper says something e

[bcrowell]

They specifically talk about the LIGO II http://www.ligo.org/ [ligo.org] gravity wave observatory. And yes, they believe that a gravity wave can be detected without having the ability to detect individual gravitons as baryonic particles.

Yes, and the existence of gravitational waves has already been proved indirectly by the Hulse-Taylor binary pulsar system, which is losing energy at exactly the rate predicted by general relativity. There is really no doubt about the existence of gravitational waves, either theoretically or empirically. LIGO is cool because it could open the door to a new way of doing astronomy, not because there is doubt about the existence of gravitational waves.

Re:There's an important lesson for physicists in t

[Canazza]

So... if they were right about that... what does that mean for us in 101 years time?