NASA Sees Orbiting Stars Flooding Space With Gravitational Waves
31 May 2005 13:57:33 UTC
Topic 189271
(moderation:
PRESS RELEASE
Date Released: Monday, May 30, 2005
Source
NASA Sees Orbiting Stars Flooding Space With Gravitational Waves
A scientist using NASA's Chandra X-ray Observatory has found evidence that two white dwarf stars are orbiting each other in a death grip, destined to merge.
The data indicate gravitational waves are carrying energy away from the star system at a prodigious rate, making it a prime candidate for future missions designed to directly detect these ripples in space-time.
Einstein's General Theory of Relativity predicted a binary star system should emit gravitational waves that rush away at the speed of light and cause the stars to move closer together. As the stars move closer together, the orbital period decreases, and it can be measured by Chandra. The orbital period of this system is decreasing by 1.2 milliseconds every year. This is a rate consistent with the theory that predicted loss of energy due to gravitational waves.
The system is known as RX J0806.3+1527 or J0806. The white dwarf pair in J0806 might have the smallest orbit of any known binary system. The stars are only about 50,000 miles apart, a fifth of the distance from the Earth to the moon. As the stars swirl closer together, traveling in excess of one million mph, the production of gravitational waves increases.
"If confirmed, J0806 could be one of the brightest sources of gravitational waves in our galaxy," said Tod Strohmayer of NASA's Goddard Space Flight Center, Greenbelt, Md. He presented data today at the American Astronomical Society meeting in Minneapolis. "It could be among the first to be directly detected with an upcoming space mission called LISA, the Laser Interferometer Space Antenna," he added.
White dwarfs are remnants of stars that have used up all their fuel. Along with neutron stars and black holes, white dwarfs are called compact objects, because they pack a lot of mass into a small volume. The white dwarfs in the J0806 system each have an estimated mass of one-half the sun, yet are only about the size of Earth.
Optical and X-ray observations of J0806 showed periodic variations of 321.5 seconds, barely more than five minutes. The observation in J0806 is most likely the orbital period of the white dwarf system. However the possibility that it represents the spin of one of its white dwarfs cannot be completely ruled out.
"It's either the most compact binary known or one of the most unusual systems we've ever seen. Either way it's got a great story to tell," Strohmayer said.
Strohmayer's Chandra X-ray observations tighten orbital decay estimates made through optical independent observations by other research teams. Strohmayer's data will be published in an upcoming issue of The Astrophysical Journal.
NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.
For additional Chandra information and images on the Internet, visit:
http://www.spaceref.com/news/viewpr.html?pid=16974
NASA Sees Orbiting Stars Flooding Space With Gravitational Waves
)
PRESS RELEASE
Date Released: Monday, May 30, 2005
Source
Marshall Space Flight Center
NASA Sees Orbiting Stars Flooding Space With Gravitational Waves
A scientist using NASA's Chandra X-ray Observatory has found evidence that two white dwarf stars are orbiting each other in a death grip, destined to merge.
The data indicate gravitational waves are carrying energy away from the star system at a prodigious rate, making it a prime candidate for future missions designed to directly detect these ripples in space-time.
Einstein's General Theory of Relativity predicted a binary star system should emit gravitational waves that rush away at the speed of light and cause the stars to move closer together. As the stars move closer together, the orbital period decreases, and it can be measured by Chandra. The orbital period of this system is decreasing by 1.2 milliseconds every year. This is a rate consistent with the theory that predicted loss of energy due to gravitational waves.
The system is known as RX J0806.3+1527 or J0806. The white dwarf pair in J0806 might have the smallest orbit of any known binary system. The stars are only about 50,000 miles apart, a fifth of the distance from the Earth to the moon. As the stars swirl closer together, traveling in excess of one million mph, the production of gravitational waves increases.
"If confirmed, J0806 could be one of the brightest sources of gravitational waves in our galaxy," said Tod Strohmayer of NASA's Goddard Space Flight Center, Greenbelt, Md. He presented data today at the American Astronomical Society meeting in Minneapolis. "It could be among the first to be directly detected with an upcoming space mission called LISA, the Laser Interferometer Space Antenna," he added.
White dwarfs are remnants of stars that have used up all their fuel. Along with neutron stars and black holes, white dwarfs are called compact objects, because they pack a lot of mass into a small volume. The white dwarfs in the J0806 system each have an estimated mass of one-half the sun, yet are only about the size of Earth.
Optical and X-ray observations of J0806 showed periodic variations of 321.5 seconds, barely more than five minutes. The observation in J0806 is most likely the orbital period of the white dwarf system. However the possibility that it represents the spin of one of its white dwarfs cannot be completely ruled out.
"It's either the most compact binary known or one of the most unusual systems we've ever seen. Either way it's got a great story to tell," Strohmayer said.
Strohmayer's Chandra X-ray observations tighten orbital decay estimates made through optical independent observations by other research teams. Strohmayer's data will be published in an upcoming issue of The Astrophysical Journal.
NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.
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please click the Graphic for more information[/url]
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For additional Chandra information and images on the Internet, visit:
http://chandra.harvard.edu/
http://chandra.nasa.gov/
http://www.spaceref.com/news/viewpr.html?pid=16974
Thanks Byron for this great
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Thanks Byron for this great Science Report
additional Info
Astronomers find best gravitational wave prospect
Greetings from Germany NRW
Ulli
[img]http://boinc.mundayweb.com/one/stats.php?userID=380 [/img]
Awesome find.... and I'm sure
)
Awesome find.... and I'm sure we'll find more like it. But...
So these two guys are 1/5th the distance from the earth to the moon apart.
There was another article that came out in Jan 04 about 2 pulsars that were found to be about 2 times the distance from the earth and moon apart, and their predicted rate of closure was 7mm per day.... 85 million years before they merge.
Here's the original article, and here's a follow-up article from today!
So (seriously) how long will these two new white dwarfs (currently closing at 2 feet per day) take before LIGO can "see" the "chirp" as they spiral into each other during the last few seconds, expelling relatively huge amounts of (hopefully detectable) gravitational energy?
(and jokingly)
500,000 miles... 7mm/day... 85 million years
50,000 miles... 2ft/day... ???? years.
I'm sure the calculation is not so linear but I'm VERY roughly guestimating approximately 1/72th of 85 million or ~1.1 million years.
Ummm... that's a long time. I hope LISA is truly senstive enough to meet that "10 year" detection goal. Else, I certainly hope we've progressed well beyond LISA in the next million years. :-) Even if it was more exponential and the time to white dwarf impact was 1/72^2 that of the pulsars, I still don't think my computer will be crunching for the next 16,000 plus years. I gotta be able to use it some time!
"No, I'm not a scientist... but I did stay at a Holiday Inn Express."
Can our project detect the
)
Can our project detect the gravity waves or do we have to wait for the satellite LISA?
Can our project detect the
)
Can our project detect the gravity waves or do we have to wait for the satellite LISA?
If I've actually learned anything from reading the webpages and watching the videos, then I'll take a shot and say that I believe the answer is "for these stars, we'll have to wait for LISA".
The gravity waves of those stars in their current orbits are at a frequency too low for the LIGOs to detect. In a million years or more, as they gradually close in and begin their final spirals too merge, their speed of orbit will rise, and with that the frequency of the gravity waves. The LIGOs' frequency range only goes down far enough to detect stars that are relatively near the final stages of merging. LIGOs will mostly "hear" just the final upward "chirp" of the gravity wave frequency rising rapidly before the stars merge.
I believe the principal problem is that the length of the arms in the LIGOs are limited by their earth bound nature, and the natural vibrations of the earth itself create "noise" at the lower frequencies we would need to listen to for these stars in their current orbit. LISA won't have the length limitations, and will be in a "noiseless" environment... and will probably have a better technology detectors.
(Somebody correct me if I'm wrong, please.)
This is NOT to say that the current LIGOs won't detect anything. It's just that current technology limits the "window" in which a LIGO CAN detect gravity waves, but our participation is still important to help further the effort. Of all the ___@home projects, I think this one is closest to true science.
As for single body objects... like pulsars... I would venture a guess that even though they may be high enough in frequency to fall within the LIGO detection range, they are probably not asymetric enough in shape (like a binary system would be) to create gravity waves that are "loud" enough to be heard.
I highly recommend these links to various video lectures and slides... (with credits to those who made the original posts!)
An excellent, easy to follow webcast lecture by Dr. Barry Barish, director of LIGO at Caltech, and well worth the 60 minutes.
Another good two part lecture series by Alan Weinstein, Caltech/LIGO... slightly more technical.
part 1
part 2
More lengthy and advanced... Kip Thorne's full course on Gravitational Waves in the form of a series of downloadable webcast lectures and slides.
It's all good!
"No, I'm not a scientist... but I did stay at a Holiday Inn Express."
Some More
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Some More information
posted: 06 June 2005
06:18 am ET
By Michael Schirber
www.space.com/science
Staff Writer
"Those waves have still not been detected directly, but there is indirect evidence," said Tod Strohmayer, who presented the results here last week at a meeting of the American Astronomical Society meeting.
Strohmayer, of NASA's Goddard Space Flight Center, presented data from the Chandra X-ray Observatory that shows the time between the X-ray blips is decreasing by 1.2 milliseconds every year. The implication is that the dwarfs are orbiting faster and faster, as they gradually fall into each other at a rate of one inch per hour.
Read the full story here:
http://www.space.com/scienceastronomy/050606_binary_dwarfs.html
Can our project detect the
)
Can our project detect the gravity waves or do we have to wait for the satellite LISA?
Broader amplifying info for this question (from another post by Ben Owen)...
The first search of the S3 data didn't find a pulsar, but it did find a lot of strange effects from the instrument in the data. These need to be cleaned out before there's any chance of detecting an astrophysical signal. You folks, with your hot-running CPUs, did the important work of finding them so that they could be removed. We were expecting some of this (like 60Hz and all its friends from the electric company), but there was more than expected. So now you are all running S3 data again, but it is a cleaner version of S3.
And now an answer to the related question of where this is all going: LIGO has been operational for several years now, in the sense of being able to measure strains. But it is a very complicated instrument (absolutely unprecedented in some respects) and therefore it is not a matter of just switching on. The first time you do that, it's not very sensitive. You track down one of the many subsystems which is giving the most trouble and beat down the noise from that subsystem. Then the instrument is a little more sensitive, and you look for the next thing, and so on. Sometimes you have to invent something completely new to get past a sticking point.
The result of this is that LIGO has been shooting toward its target sensitivity for the last few years. It is now very close to that sensitivity. S3 is within a factor of a few. The S4 data, which is in the can and being prepped for analysis, is within a factor of two. S5, which will start later this year, will be at (or at some frequencies a little beyond) target sensitivity. Also, S5 will not be a few weeks' run between equipment upgrades; it will be a solid year, and that also improves the chances of detection.
We may not be detecting gravity waves, yet... but we're helping the project get closer to doing it.
"No, I'm not a scientist... but I did stay at a Holiday Inn Express."
Barkster, You wrote: If
)
Barkster,
You wrote:
If I've actually learned anything from reading the webpages and watching the videos, then I'll take a shot and say that I believe the answer is "for these stars, we'll have to wait for LISA".
This is true - for that particular binary star system. At least for the next few million years. LIGO is sensitive to things like that at the very end, before the stars collide.
And:
I believe the principal problem is that the length of the arms in the LIGOs are limited by their earth bound nature, and the natural vibrations of the earth itself create "noise" at the lower frequencies we would need to listen to for these stars in their current orbit. LISA won't have the length limitations, and will be in a "noiseless" environment... and will probably have a better technology detectors.
All that is true, but if you look at the projected noise curves the strain amplitude is about the same for LISA as it is for LIGO. The main thing is that there are more sources, many of which are already observed (including the indirect effects of gravitational radiation). To take this binary star system as an example, LISA sees it for a million years (or whatever) while LIGO sees only the last few minutes. Clearly if you extrapolate this to the population of similar star systems, LISA will see a lot while LIGO is hunting carefully for just one.
But for some other things - like pulsars - LIGO has a shot at detecting them, while LISA can't (or mostly can't).
As for single body objects... like pulsars... I would venture a guess that even though they may be high enough in frequency to fall within the LIGO detection range, they are probably not asymetric enough in shape (like a binary system would be) to create gravity waves that are "loud" enough to be heard.
It's true that the asymmetries (quadrupoles) for isolated pulsars are much smaller than for binaries, but some of them can be "loud" enough for LIGO. Basically it has to do with populations. Single neutron stars are much more common than binaries, so even though the typical signal emitted by an object will be weaker, the typical object emitting the signal will be much closer. Thus the signal received at the detector can be comparable, if the numbers work out.
The subject of deriving those numbers is very complicated, but I'll summarize it by saying that LIGO is looking for pulsars within our own galaxy. (Actually, right now, since the S3 data is still not up to full sensitivity, it's a pretty small fraction of our own galaxy.) LIGO is already sensitive to merging binaries out beyond the local group of galaxies, and is edging towards the outskirts of the large Virgo cluster of galaxies.
Right now the odds of something being within the sensitive range of the instrument are pretty slim, but they are improving as the range improves. You'll see more in Bruce's "report card" that he is writing up.
Stay tuned,
Ben
Awesome, Ben... I learn
)
Awesome, Ben...
I learn more every time. Thanks!
My confidence meter is up, again. Three "True, but..."s are a lot better than three "Your wrong"s. I almost feel unburdened about the "layman's guide" post, now.
Bring on that S4 data!
Glenn
"No, I'm not a scientist... but I did stay at a Holiday Inn Express."