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New Kind of Gravitational Wave Source Detected? (nature.com)
"Scientists possibly detected an entirely different type of gravitational wave [source]," writes schwit1. "Gossip over potential detection of colliding neutron stars has astronomers in a tizzy," reports Nature:
Astrophysicists may have detected gravitational waves last week from the collision of two neutron stars in a distant galaxy -- and telescopes trained on the same region might also have spotted the event. Rumours to that effect are spreading fast online, much to researchers' excitement. Such a detection could mark a new era of astronomy: one in which phenomena are both seen by conventional telescopes and 'heard' as vibrations in the fabric of space-time. "It would be an incredible advance in our understanding," says Stuart Shapiro, an astrophysicist at the University of Illinois at Urbana-Champaign...
The Laser Interferometer Gravitational-Wave Observatory (LIGO) in Louisiana and Washington state has three times detected gravitational waves -- ripples in the fabric of space-time -- emerging from colliding black holes. But scientists have been hoping to detect ripples from another cosmic cataclysm, such as the merger of neutron stars, remnants of large stars that exploded but were not massive enough to collapse into a black hole.
One astronomer tweeted last week that "merging neutron-neutron star is the initial call," while Nature adds that the same rumor had already been circulating privately, according to "some astronomers who do not want to be identified."
Friday Ligo announced cautiously that "We are working hard to assure that the candidates are valid gravitational-wave events, and it will require time to establish the level of confidence needed to bring any results to the scientific community and the greater public. We will let you know as soon we have information ready to share."
The Laser Interferometer Gravitational-Wave Observatory (LIGO) in Louisiana and Washington state has three times detected gravitational waves -- ripples in the fabric of space-time -- emerging from colliding black holes. But scientists have been hoping to detect ripples from another cosmic cataclysm, such as the merger of neutron stars, remnants of large stars that exploded but were not massive enough to collapse into a black hole.
One astronomer tweeted last week that "merging neutron-neutron star is the initial call," while Nature adds that the same rumor had already been circulating privately, according to "some astronomers who do not want to be identified."
Friday Ligo announced cautiously that "We are working hard to assure that the candidates are valid gravitational-wave events, and it will require time to establish the level of confidence needed to bring any results to the scientific community and the greater public. We will let you know as soon we have information ready to share."
But a new reason for them being formed.
If builders built buildings the way programmers wrote programs, then the first woodpecker would destroy civilization.
NO, NO, NO! A gravitational wave is a gravitational wave. The correct title of the article should have be "New source of gravitational waves detected". The new source is binary neutron star merging as compared to binary black hold merging.
DGDanforth
Consider that a wave implies that something is oscillating, otherwise you don't have a wave at all. Scientists can't even explain what is oscillating when these supposed gravitational waves occur, which is a huge problem
Um, they can and have. The curvature of spacetime is what's rippling, and the observable effect is changes in distance and/or timeflow. It's a consequence of the general theory of relativity.
LOL. Did you know that spacetime is a block universe in which nothing happens?
That your mind is to small to accept that our four normal dimensions are local phenomena that vary, and that there is no universal distance or clock to satisfy your belief in them, well, that's no skin off my back. Just don't run for congress, 'k?
In a more simplistic way, IMHO, their name is self-explanatory.
Water waves are variations in the height of water. A kind of shock-wave is variations on the air pressure around you, etc.
So, gravitational waves are variations on the gravity field around you and, of course, this has an impact on space time as we understand it nowadays and it can be measured now that we have more precise instruments.
At least, that's how I understand it without much research on the subject. Please elaborate if I am too simplistic since I assume that you are better documented than myself on the topic.
Anyway, there is a classical story on the NTP forums of a guy measuring time going slower; he had 2 atomic clocks and was going on a trip across the States. He left one home and he put the other one in the trunk of his car. When he got back home, he could see that the clock that had been accelerated and decelerated physically had gone slower compared to the one that was left home while the clocks wouldn't diverge when left side by side.
-thx
Everything I write is lies, read between the lines.
The measurement of direction depends on having three detectors spaced well apart. They compare the time of arrival of each wave pulse at the detectors and get a direction. It's not nearly accurate enough to be a single galaxy, but if there is a new very bright source of gamma rays/X-rays/... in the right general direction appearing at the right time, it's a reasonable working hypothesis that they are related.
I'm not a gravitational wave astronomer (or any other kind) but I know some physics and I am interested in the details of highly precise astronomical instruments. LIGO can, and does, measure variations in the length of the arms of the interferometer of the order of 10^-18 meters. There are many techniques needed to achieve this accuracy -- extremely stable laser sources where neither the power level nor the phase varies by much more than the inevitable statistical variation due to the beam being made up of photons; very powerful lasers so that that statistical noise is as small as possible in comparison with the total signal; the path is between very solid quartz mirrors VERY carefully suspended in a vacuum, with active damping of some vibration frequencies and active control of the mirror temperature; the beam bounces up and down the tunnels many times, so that the effective path length is longer; etc. etc.. In normal operation the paths are adjusted until the signals from the two arms precisely cancel one another out (destructive interference) and then any change in path lengths, even if only a very tiny fraction of a wavelength, shows up as a small fraction of the very powerful beams not interfering destructively, but instead being detected by a very sensitive detector, etc. etc,
It's a triumph of laser engineering and should be celebrated.
The supernova signal is due to the time it takes the photons to get out through the remains of the exploding star. They are reabsorbed and reemitted multiple times in this jouney. The neutrinos come straight from the core and mostly escape directly.
I heard they don't have enough detectors to triangulate the source based on speed of light delays. Also the reason we can't find meteors headed towards us is because we can't watch 100% of the sky at a time; not even close in fact. So combine those two facts and how do they have any remote idea whatsoever what the source might have been?