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Three Largest Stars Identified
mOoZik writes "BBC News is reporting that astronomers have identified the three biggest stars known to science, having diameters of more than 1.5 billion km. If they were located in the same place as our own Sun - at the centre of the Solar System - the stars would stretch out further than the orbit of Jupiter!"
YES, they can be that thin.
m
If I may be lazy and just give you a URL:
http://www.astronomynotes.com/evolutn/s5.ht
There are lies, damned lies, and statistics.
Don't worry about it. These giants are big, but not necessarily massive enough to go supernova at the end of their lives.
Besides, hypothetically, even if it were to explode like a supernova, it won't affect us much. Here is the number:
d = distance to the closest giant (5200light-yr)
E = total energy arising from supernova (1e51erg or something like that)
The energy receied at the Earth is
E / (4 *pi *d*d).
Now compare this number with the energy we receive every second from the Sun:
E_sun / (4 * pi * r*r)
where r is the distance between the Earth and the Sun (1.5e13 cm). You do the math, then the ratio of these two quantities comes out to be:
[E/(4*pi*d*d)] / [E_sun/(4*pi*r*r)] ~ 2.4
So all we get from this supernova is about 2 seconds worth of energy received from the Sun. And I'll tell you that the actual energy received from the supernova is much, much smaller.
Several other posts have danced around the question a little bit, without answering it directly. It's a good question.
While these stars are big, filling a large volume of space, the article doesn't mention their mass. This is the ultimate determinant of what becomes a black hole and what doesn't.
Stars have gravity trying to pull everything into the center off it's mass. In physics pressure is basically equal to temapture, so as all the mass is squezed together, it heats up and begins nuclear fission. This creates a lot of heat, and the star's mass tries to expand. Gravity and pressure find a happy meidum and that is how the star ends up a particular size.
As the star burns it's fuel, it has to get hotter or it will stop 'burning', due to the way nuclear fusion works. Eventually it will burn up its fuel and prssure will not balance gravity, and the whole star will collapse. If it is really heavy, say several times the mass of the sun, it will probably collapse into a black hole. If it is slightly heavier than our sun, it might end up as a very dense neutron star. Otherwise, it will end up as a white dwarf, a small star that is somewhat like a ember left over after a campfire. If a star is really massive it can also explode in a supernova to lose some weight and avoid becomming a black whole.
As I mentioned, the article doesn't say what the mass of the star is, but it's probably a safe bet that is above the black hole limit. When it finishes burining its fuel, it will likely go supernova and/or become a black hole.
HA! I just wasted some of your bandwidth with a frivolous sig!
supernovae . The collapse of these massive stars may produce a neutron star or a black hole .
For a detailed example of supernovae -> black hole, click here.