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You could think of it as the real dancing with the stars. Two white dwarf stars have been found twirling around each other to make a complete orbit in less than every 13 minutes. And they provide a chance to test ideas about general relativity and gravitational waves. The system is described in a paper accepted by the Astrophysical Journal Letters. [Warren Brown et al., "A 12 minute Orbital Period Detached White Dwarf Eclipsing Binary"]
One of the stars is about the size of Earth, but has more than half the mass of the sun. A penny as dense as the star would weigh half a ton here. The other star is about 60 times our size and has about half the mass of its companion.
Astronomers estimate that the partners will collide in about 900,000 years. At that time, they could form a stable binary star, or merge into a single, rapidly spinning white dwarf, or go supernova. In the meantime, they provide a place to look for gravitational waves. Because they’re not exchanging mass now, gravitational waves should account for the loss of energy that brings them closer every year. Which for each of them around the other is just a few podcasts long.
—Steve Mirsky
[The above text is a transcript of this podcast.]
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8 Comments
Add CommentDo we not know their mass? If they are both > 0.7 MSun then their merger will exceed the Chandrasekhar limit and they will go nova.
Reply | Report Abuse | Link to thisNova smova, isn't the point that it is a rare opportunity to gain insight into gravity? I say they will turn into provolone cheese, and my theory is just as valid as yours and just as irrelevant for a 900,000 years in the future outcome. The point again, is a chance to study long-term gravity waves and gravity effects; I say great discovery! - we can use the cheese!
Reply | Report Abuse | Link to thisI'd be surprised if the waves produced by this drowning couple can be felt on the passing ocean liner "Milky Way"...
Reply | Report Abuse | Link to thisNo, but the point is any net loss of energy in that system HAS to be a result of gravity wave emission. Any other process between them would just be a net transfer (for instance tidal effects, which could transfer angular momentum from rotation of one/both partners into orbital angular momentum). Perhaps we'll be able to set observational bounds on how much of this energy is being emitted. Detecting the actual gravity waves would be nice, but if we see an energy loss identical to the energy these waves should have by theory, it is still pretty handy. Might be MORE interesting if the observations contradict GR. We already pretty much know GR isn't a complete theory. Measuring where it failed would be a useful thing.
Reply | Report Abuse | Link to thisThanks for explaining the GR perspective - I think get the general idea now, presuming the orbital periods diminish as expected.
Reply | Report Abuse | Link to thisThe linked report's abstract does state:
"...this system would be detected by the proposed LISA gravitational wave mission in the first week of operation. This system’s [expected] rapid change in orbital period will provide a fundamental test of general relativity."
I think that current efforts to detect distant gravitational waves within the Earth's gravitational field at its surface are completely misguided. I'm exceedingly skeptical that even a space mission within the gravitational field of the Sun can successfully detect a faint gravitational signal that has passed through the complex, locally varying gravitational environment of the Milky Way, but perhaps I'm wrong...
"I say they will turn into provolone cheese, and my theory is just as valid as yours and just as irrelevant for a 900,000 years in the future outcome." really, stars turning into cheese is just as valid as a supernova? That is a pretty ignorant thing to say. You think long timescales makes things impossible to predict? Best to have a clue what you are talking about before criticizing others.
Reply | Report Abuse | Link to thisOh, 900,000 years, can we human live that long and see the effects? I believe if it were, the most prestigeous subject in college, no cosmosollege, will be the astronomy...
Reply | Report Abuse | Link to this'Any net loss of energy in that system HAS to be a result of gravity wave emission'. Not necessarily true. Energy can be lost via other channels. E/M radiation for example.
Reply | Report Abuse | Link to thisEnergy can be transferred from one object to the other through tidal effects. Though this is an example of gravity radiation in action it would cause the orbit to 'decay' in the sense that the bodies would tend to separate rather than get closer.