NASA Announces Discovery of 30-Year-Old Black Hole 195
broknstrngz tips news of an announcement today from NASA about the discovery of a black hole in the M100 galaxy, roughly 50 million light-years from Earth. The discovery is notable because, if confirmed, it's now the youngest known black hole, born from the remains of a supernova we observed in 1979. Bad Astronomer Phil Plait explains why scientists think it collapsed to a black hole, rather than a neutron star: "The way a neutron star emits X-rays is different than that of a black hole. As a neutron star cools, the X-ray emission will fade. However, a black hole blasts out X-rays as material falls in; that stuff forms a flat disk, called an accretion disk, around the black hole. As this matter falls onto the newly created black hole, it gets heated to unimaginable temperatures — millions of degrees — and blasts out X-rays. In that case, the X-rays emitted would be steady over time. What astronomers have found is that the X-rays from SN1979c have been steady in brightness over observations from 1995 – 2007. This is very strong evidence that the star’s core did indeed collapse into a black hole." He also warns that we're not certain quite yet, and we'll have to keep our eye on it to make sure it's not a pulsar.
Accretion DIsks ? (Score:3, Interesting)
Neutron Stars can have accretion disks too. (LSI 31 303 is supposed to have one, for example.)
So I am not sure I see why that is determinative. Off to read the article.
Re:Because everyone else will say it too... (Score:5, Interesting)
There's an obvious universal frame of reference: measure everything relative to the place where the big bang happened. Your choice of axes is somewhat arbitrary, though.
This is a common misunderstanding of the big bang theory.
There is no center. It didn't start at a "location". The entire universe is evenly expanding, from everywhere.
They common analogy is to reduce the 3D space of the universe to a 2D example. Imagine two points on the 2D surface of a balloon. One point is you ("the observer"), the other point is something distant, like a star, that you are observing. Now inflate the balloon. The result is that the two points move apart, because space (the rubber of the balloon) is expanding. A line drawn between the two points would be longer and longer. Note that neither point is "special". Both points observe the same symmetric effect: the other point moving away.
The real universe is a lot like this, except instead of a 2D surface expanding, it's a 3D volume expanding. There's no "center", all of the points move away from each other. From the point of view of each observer, they are the center.
More accurately speaking, each observer is the center of their own private spherical "observable" universe expanding away from them. The center of the universe is your own head. 8)
Re:Because everyone else will say it too... (Score:4, Interesting)
"Are you suggesting that there's a global frame of reference?"
No, but he could argue that there's in fact a *privileged* frame of reference with regards of age: the one centered on the object to be dated.
Re:Because everyone else will say it too... (Score:3, Interesting)
A common (probably simplified) model for the universe is a 3-sphere (i.e. the set of points equidistant from a single point in 4 dimensions). A more familiar 2-sphere (e.g. a basketball) is the set of points equidistant from a single point in 3 dimensions. Imagine that you were a being that can only perceive 2 spatial dimensions. You would perceive a sphere as being a world in which you could travel in a straight line in any direction, and you would return to your starting point (i.e. either any point is the centre, or none of them are -- you can't visit the "real" centre). Similarly, we are beings who can only perceive 3 spatial dimensions. If the universe is a 3-sphere, then we could travel in a straight line away from Sol in any direction, and we would eventually return here. The universe may well have a geometric centre, but we can't visit it.
The expanding universe can be modelled by increasing the radius of a 3-sphere with time. At t = 0, the whole universe occupies a infinitesmal point in 4D space. As the universe "inflates", the "area" of the 3-sphere's "surface" increases (or, if you like, the 3D volume of the universe increases). This volume increase occurs evenly and at the same rate at all points in space.
The GP is entirely correct. You need to engage your brain.
Re:Because everyone else will say it too... (Score:3, Interesting)
Time is pretty meaningless when you're talking about black holes. The closer you get to the thing, the slower time goes. The only frame of reference in regards to time that has any meaning is ours, observing it.