View Full Version : Discussion: This Star Just Shut Down

2004-Jun-28, 04:54 PM
SUMMARY: Astronomers have found a white dwarf star which has shut down its fusion reactor very recently - perhaps only 100 years ago. By probing this star with the Chandra X-Ray Observatory and the Far Ultraviolet Spectroscopic Explorer (FUSE), astronomers see that its heart is completely stripped of hydrogen and helium; the surface is largely carbon and oxygen, heated to 200,000 degrees. Nothing like this has ever been seen. Our own Sun will eventually become a star like this, after it has expended all of its hydrogen fuel.

What do you think about this story? Post your comments below.

2004-Jun-28, 05:06 PM
It's always interesting seeing stories about observing objects near critical points in the stellar life cycle. There's a lot to learn from this one.

2004-Jun-28, 06:58 PM
Refresh my memory - how far away is this particular star? If we "know" that this star shut down within the last 100 years, doesn't that mean it is only a few light years away, and we have been observing it for at least 100 earth-years? Even X-ray emissions travel at the speed of light, don't they?

Or maybe I'm missing something here.

2004-Jun-28, 08:01 PM
Originally posted by Zeb@Jun 28 2004, 06:58 PM
Or maybe I'm missing something here.
Hi Zeb,

What you are missing is that science writers write about astronomical events as we see them. We are seeing this star as it looked 100 years after it shut down. The star is probably ten thousnad lightyears away, and the uncertainty in its distance is greater than 100 light years. How would you express it? If you can think of a good way that isn't cumbersome you'll be helping science writers everywhere.

2004-Jun-28, 08:09 PM
Actually I don't think that's what he meant antoniseb. If the star is only 100 years or so removed from the time it was burning hydrogen, then 100 years ago its light must have been seen in the sky.

Mind you, I don't know how far away the star is, so I have no idea what its luminosity would have been. Maybe below naked eye visibility?

2004-Jun-28, 08:48 PM
Nice discovery, if this star has recently lost it's outer layers shouldn't there be something detectable left to see of those layers, like a nebula or disk?


Martin Barstow (Coauthor on the
2004-Jun-29, 08:32 AM
Its nice that this result has generated so much discussion. This is a really unique object and we know of no other white dwarf like it.

Should this star have a nebula? Thats a really good question. It doesnt seem to have one and a planetary nebula should certainly appear at some time during the production of a white dwarf. However, when the nebula might appear and for how long it would remain visible depends on a number of factors, including the surrounding density of interstellar gas. We know of a lot of very hot young white dwarfs that do not have nebulae, so H1504+65 is not peculiar in that sense. Also, the production of a nebula is not necessarily connected with the end of nuclear fusion. Some nuclear burning could still be going on while the star is losing its outer layers.

The distance is uncertain, but probably about 1500 light years.

Martin Barstow
University of Leicester
Co-Author of the research.

2004-Jun-29, 11:24 AM
what r the chances of magnesium reacting with carbon and producing alternate energy source and r we also looking into the opportunity of finding if the temperature cools down in near future (star terms) and perhaps start some steller formation.

2004-Jul-17, 05:23 PM
Since this star is pretty much not nearing, but is rather at, the end of its life cycle, we should be keeping a very close watch on it.

2004-Jul-20, 01:20 PM
This object is the featured story on the Chandra website.
A little more detail is given than in the original story. Also there is a nice image [is it actually the object, or is it a stock image of a bright blue thing?].

Astronomers Reveal Extinct Extra-Terrestrial Fusion Reactor (http://chandra.harvard.edu/press/04_releases/press_062804.html)