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Deep in the Core
meehawl writes "A video of what is currently thought to be the closest star to the supermassive black hole at the centre of our galaxy. The star orbits the black hole in a highly elliptical orbit with a period of 15 years or so, but at its closest approach it swings within 17 light hours of the black hole (around three times the distance between the Sun and Pluto). In the video, you can see the star ricochet past its closest approach to the black hole. This slingshot effect enabled astronomers to further pinpoint the mass of the black hole, which is confidently estimated at 2 million suns or so. The mass observation, coupled with the size constraints observed, indicates the object at the centre of the galaxy is definitely composed of some exotically dense form of matter."
The http://arxiv.org/abs/astro-ph/0210426:linkedarticl e says the "enclosed point mass" (read: black hole) has a mass of 3.7 million solar masses, +- 1.5M solar masses. Not 2M solar masses, as the article summary indicates. For most people, myself included, this is a meaningless distinction, but in the interest of scientific accuracy, I thought I'd mention it.
High-speed Road Trip (18.000KPH)
but seriously, since it is revolving around the black hole, does that mean it is slowly being sucked in?
Revolving is kind of a 2 dimensional way to look at it. Instead it is orbiting, which is actually a perpetual fall. So the short answer is..."yes, it is not being sucked in". Really, I would have no idea how to do the math (as most of the variable are too...variable). But basically, for every object that can be orbited you can figure out a minimum sustainable orbit versus one that is catastrophic.
Apparently you haven't studied these things. The universe is 13.7 billion years old, it takes light from even the nearest star years to reach us, the Earth's mass is only a fraction of Jupiter's, Jupiter's mass is only a fraction of the sun's, the sun's mass is only a fraction of some other stars that exist, and on and on. So the general idea is that a lot of the things in the universe are a lot bigger than you and me and our tiny planet. So if a star (and just think how much mass is in a star compared to you) orbits something in 15 years, you don't think it's just a bit interesting that it covers about half of its entire orbit in one fifteenth of the total time?
Esoteric reference.
Anybody else get a plain black screen for the video?
Running Media Player Classic, I get diddly squat in the way of moving dots.
Of course, I suppose I could just be looking at the black hole itself......
"City hall" in German is "Rathaus" Kinda explains a few things......
Knowing, not speculating, that this star is orbiting to within 17 light hours of a given point and and that the whole path is an elipse which is about 10 light days across on it's long axis, that star is reaching orbital speeds approaching .01c on the return swing. So it's definitely orbiting something *very* massive, and we obviously don't "see" something there.
Pretty strong evidence, if not conclusive confirmation, of the existance of a black hole there. If anyone wants to debate the existance of black holes, they're going to need to come up with some pretty interesting theories to explain that kind of movement.
Even people that believe in pre-destiny look both ways before crossing the street.
How is the video not as it appears? You didn't expect the video to be in real time, did you? Among non-crackpots, there is no longer much debate about whether or not black holes exist. The alternatives have either been ruled out observationally, or have serious problems on theoretical grounds. Disclaimer: IAAA.
According to the original paper from 2002, the star is nowhere near close enough to be "tidally disrupted", so it's just orbiting. (What it says is that even at closest approach, it's still 70x too far way.)
With all those stars whipping around, though, it wouldn't be hard to get the occasional star either entirely ejected, or potted right in. More usually, an orbit would be changed so that it approaches closely enough on each orbit to have a bit of mass (say, a trillion tons) stripped off, and gets used up over the course of a few thousand years. Of course at some point we wouldn't be able to see it any more, so there could be a bunch of those happening right now.
Probably most of the mass moving near it is non-radiating low-density plasma whose motion is controlled less by gravitation than by unimaginably intense electromagnetic fields. We see stars, but there's lots else going on in there we can't see.
Black holes don't have special sucking power... it's just normal gravity. Just as a planet can orbit a star, or a star can orbit another star, a star can orbit a black hole. It will behave exactly as if it were orbiting a planet of an equal mass, as long as it's going fast enough to maintain orbit.
The caveat is that if one gets too close to the black hole, within what is termed the 'event horizon', then there is no turning back. Not even light escapes (generally speaking -- Stephen Hawking would be a more appropriate speaker on the subject.) This star does not appear to be doing that since it's still orbiting, and we can see it.
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It would be a stable orbit, except this is a pretty unusual situation. It's in a pretty dense neighborhood, so the star may interact with other stars or other matter. Such collisions will often take energy out of the orbit. Also, as seen with orbiting pulsars, the star loses some energy due to gravitational radiation. There could be magnetic fields that put a brake on things over long periods of time. If the star gets too close, tidal distortion becomes significant.
There are plenty of forces that could cause the star to spiral in. The calculations are left to the reader. I am sure people will be watching for changes in the orbit.
Fiat Lux.
it takes light from even the nearest star years to reach us
Umm, 8 minutes, actually.
"We returned the General to El Salvador, or maybe Guatemala, it's difficult to tell from 10,000 feet"
Google it.
--
make install -not war
But basically, for every object that can be orbited you can figure out a minimum sustainable orbit versus one that is catastrophic.
Definitely, good post. I believe you refer to escape velocity, which is represented by the equation: escape velocity = sqrt(2GM/r) where G is the gravitational constant, M is the mass of the the object which the potentially escaping object orbits, and r is the distance between the center of mass in the body being orbited and the point at which escape velocity is calculated (at different points in the orbit, the necessary velocity would fluctuate). Orbits in which the object's velocity is less than escape velocity are said to be bound, and those in which it exceedes it are said to be unbound. At that point, the path of the escaping body is no longer elliptical, but rather hyperbolic.
More information at http://en.wikipedia.org/wiki/Escape_velocity
Actually I was talking about the time it takes the star to complete its orbit. Which is written in the top left corner going from 1992 to 2005+. Maybe timeline is not the best word, but the point is the video is not in real time, and that fact is made clear thanks to those time numbers.
Your statement is witty, insightful, and more importantly, correct. It's only logical that an hour later your comment remains unmoderated.
/. reader smile today, friend.
Know that your effort was not in vain: you made at least one
No.
Examples of the real images are readily available (from near-infrared speckle imaging). It would be a herky, jerky, incomplete mess to the general public, however, to make a video of the actual data, hence the rendered movie. You can see, in the zoom in, the data points of actual observations used to determine the orbit of the key star. Scientists aren't trying to hide a thing. They're just trying to present their results in the clearest, most comprehensible way. Give them some credit for that. Scientists hide very little, as a general rule. We usually have to beg people to listen. Slashdot is a nice exception.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
No, actually. http://en.wikipedia.org/wiki/Kepler#Kepler.27s_law s
Kepler's elliptical orbit law: The planets orbit the sun in elliptical orbits with the sun at one focus.
Kepler's equal-area law: The line connecting a planet to the sun sweeps out equal areas in equal amounts of time.
Kepler's law of periods: The time required for a planet to orbit the sun, called its period, is proportional to the long axis of the ellipse raised to the 3/2 power. The constant of proportionality is the same for all the planets.
heat == infrared photon, which like optical photons,cannot escape a black hole. however, heat can be generated from the accretion disc of matter being pulled into the hole. e.g. gas being ripped off a nearby star and orbiting the hole.
Most of the things you bring up have been discredited at some level. Some of Halton Arp's "associated" systems in particular have been quite strongly discredited. It's not a matter of wanting one thing or another, it's just that the evidence you cite isn't very compelling to most of us. And when it's a small handfull of folks crying about something, they die off and we don't worry about it anymore. If they really have something, they can make their case in a compelling way and people will listen. Arp, in particular, did some very good work in the distant past, but not so recently.
Some people can't give up their ideas, and some people like to be contrary. That's just not good enough.
If you take this stuff too seriously, you're being sucked in by a bunch of crap. My primary area of research these days is in quasar-host galaxy relationships, and I've got hundreds of examples of quasars with stars at exactly the same redshift. A lot of the things you cite just look stupid to most of us these days.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
If a black hole can create a gravitational force so powerful it can suck in light, doesn't that mean that when the light is being sucked in it is travelling faster than light towards the black hole?
No, as light doesn't speed up and slow down in empty space. Instead, it changes frequency. Light travelling towards a black hole (or any other gravitating object) gets blue-shifted.