Discussion: LISA Will Watch Snacking Black Holes

[Fraser]

SUMMARY: A new space observatory called the Laser Interferometer Space Antennae, or LISA, will help help astronomers watch black holes as they gorge on new matter, growing larger in the process. These binges are thought to cause gravitational waves, which are ripples in spacetime. LISA consists of three spacecraft separated by 4.8 million km (3 million miles) which keep track of their relative positions very carefully. As the gravitational waves pass, the spacecraft should move relative to each other, like boats floating on the ocean when a wave goes past. LISA should launch in 2008, and will hopefully detect several black hole events a year.

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[antoniseb]

It will be interesting to have LISA out there. A positive result will be a pretty major blow to the anti-GR alternative theorists. I wonder is LISA by itself can provide a strong direction to the source.

[Svemir]

Finally an experiment that, if succeded, can provide answers to several fundamental questions about the nature.
1. I hope they can account for contamined data as random movements coused by solar wind and electric currents ( EU model will be tested too :-)).
We are talking about nanometers here!
2. The experiments can show wether the gravitational waves are transversal or longitudal, IF they exist.
Remember, Einstein was not sure in 1905 that they exist, and they are not really needed in SR.
Ability to pont to the source is crucial here(that is why there are 3 probes, I guess).
3. The speed of gravity (whatever gravity means) can be confirmed to be c.
The question can be left open in the case of "unconclusive results".
I doubt it can be confirmed to be 10^10 m/s.
4. I hope the spacecrafts have some kind of spectrograph onboard. It could ,perhaps, confirm or dissmiss CREIL or other causes of redshift.

[antoniseb]

Originally posted by Svemir@Jan 19 2005, 09:41 AM
4. I hope the spacecrafts have some kind of spectrograph onboard. It could ,perhaps, confirm or dissmiss CREIL or other causes of redshift.

I'm not sure what you mean by spectrograph, or how that would help. There are other spacecraft that are up there collecting portions of the electro-magnetic spectra. If you mean gravitional-wave frequency, I'm sure LISA is designed to report it.

[Svemir]

An apparatus for photographing or mapping a spectrum.
I mean, those cpacecrafts will measure distance (4.8 million km) between each other by laser beams, right?
I imagine that any change in frequency of those beams will be effect of "tired" light (no change, no "tired" light once for all).
I mean, IF it can be measured.

[antoniseb]

Originally posted by Svemir@Jan 20 2005, 07:29 AM
An apparatus for photographing or mapping a spectrum.
I mean, those cpacecrafts will measure distance (4.8 million km) between each other by laser beams, right?
I imagine that any change in frequency of those beams will be effect of "tired" light (no change, no "tired" light once for all).
I mean, IF it can be measured.

There will be no spectroscopic equipment in these spacecraft. It will be a fairly simple setup that gives them the ability to maintain distance and orientation to high precision, and to observe the peaks and troughs of interference of the very narrow frequency band of light given off by the most stable lasers they could construct.

As to tired light, I don't think it exists, but even the most ardent supporters of the idea wouldn't think it detectable over a five million kilometer path through interplanetary space, and they think it would be constant, and not the sort of several millisecond cyclic rise and fall expected in gravity waves.

[The Bad Astronomer]

Fraser, in your summary you say LISA will launch in 2008. Actually, it's a pathfinder mission that may launch then; basically a testbed to make sure the technology works. LISA itself is many years away from that launch date! It is planned for launch in 2011, and it'll probably be later than that by a year or two (my guess).

[tonne]

Originally posted by The Bad Astronomer@Jan 21 2005, 09:16 PM
Fraser, in your summary you say LISA will launch in 2008. Actually, it's a pathfinder mission that may launch then; basically a testbed to make sure the technology works. LISA itself is many years away from that launch date! It is planned for launch in 2011, and it'll probably be later than that by a year or two (my guess).

Thanks for the update

there's also a bit of info on these sites

http://www.esa.int/export/esaSC/SEM5TDWO4H...HD_index_0.html

http://www.srl.caltech.edu/lisa/news.html