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NASA Takes Step Forward In Planet Finding
Spy der Mann wrote to mention a piece at Physorg.com about a major breakthrough in planet finding. From the article: "On a crystal clear, star-filled night at Hawaii's Keck Observatory in Mauna Kea, NASA engineers successfully suppressed the blinding light of three stars, including the well-known Vega, by 100 times. This breakthrough will enable scientists to detect the dim dust disks around stars, where planets might be forming. Normally the disks are obscured by the glare of the starlight. Engineers accomplished this challenging feat with the Keck Interferometer, which links the observatory's two 10-meter (33-feet) telescopes. By combining light from the telescopes, the Keck Interferometer has a resolving power equivalent to a football-field sized telescope. The 'technological touchdown' of blocking starlight was achieved by adding an instrument called a 'nuller.' "
A bit of unfortunate news: I recently read in an article that the ice cap on top of the high peak of Mauna Kea has been melting, as a result of global warming.
As the ice cap melts, the foundations of many observatories, Keck being one of them, is starting to shift, and they may have to be abandoned in a few years. What a great setback to science that could be.
Cost? Ability to get large objects into space is about nil right now. And even when it is possible, cost is astronomical (sad pun intended). I believe in the order of $20,000 per pound (156,800 british pounds per stone for those of you on the other side of the pond). Rather expensive.
See my journal for slashdot ID's by year. Mine created in 2005. http://slashdot.org/journal/289875/slashdot-ids-by-year
Actually, yes. It uses the interference patterns between the light received at the two (or more) telescopes to give resolution many times that of the individual instruments. http://en.wikipedia.org/wiki/Interferometry
Be relentless!
Article is here. I haven't tried this myself, it looks like a lot of work.
Finally, since I haven't seen a one sentence synopsis, a nulling interferometer does a careful job making the on-axis starlight received by two telescopes interfere destructively, while off-axis light from circumstellar emission passes through the system. This instrument is designed to study dust emission analogous to the zodiacal light in our own solar system.
Dobson didn't invent anything! Alt-Az mounts have been around for hundreds of years! At least say you have a 8" NEWTONIAN on a Dobsonian mount!
> Can this be programmed into cheap telescopes for well known light sources?
:-(
No. The technology required to combine two light beams in
a coherent way is wa-a-a-y more expensive than a "cheap"
telescope. One must be able to control the length of the
two paths of light to a small fraction of wavelength of
the light. In the case of ordinary visible light, that
means "a small fraction of about 500 nm". That's the
hard part
> Is this the answer to light pollution?
Again, no. If you can perform interferometry, you
can in effect reduce the size of the field of view, if
you wish, and therefore reduce the noise contributed
by background light; but for most purposes, you
still want to see more than just point sources,
which means a reasonable field of view, which
means that there is still plenty of noise from the
background.
Alas.
Michael Richmond "This is the heart that broke my finger."
mwrsps@rit.edu http://stupendous.rit.edu
Except that using the moon blocking the light (as in an eclipse) isn't a good analogy for a nuller. The nulling interferometer doesn't have to put in anything to block the light-- it adjusts the relative phase of light on two different paths so that the on-axis light cancels out, but the off axis light doesn't. There are different instruments that work more like an eclipse, where a stop is used to block the startlight but not the planet light.
Here's the how and why of it:
Bring two beams of light from the same star (but separate telescopes) together, with exactly half a wavelength of extra pathlength added to one of the beams, and the light from one beam will cancel out the light from the other. It's a consequence of the wave-like behavior of photons.
This happens only for light very close to the optical axis. Light coming from something close to the star won't cancel. So you can use this "nulling" effect to study faint things very close to bright stars.
The easiest things to see this way are companion stars and massive, dusty disks. Our Sun has a dust disk around it - the Zodiacal Disk - but it's not very massive and doesn't capture much sunlight, so it would be hard to see with an instrument like the Keck Nuller from a planet around a nearby star. But it might turn out that the Sun's disk is atypically thin; we know that some other Main Sequence stars have dust disks orders of magnitude more massive and brighter than the Sun's.
A bright dust disk can easily outshine an Earthlike planet. NASA doesn't want to launch a mult-billion dollar space planet-finder, only to discover it can't see planets because it's blinded by by dust around their parent stars.
So the Keck Nuller was built to study a sample of Sun-like stars to find out how common massive dust disks actually are, and whether they pose a problem to a planet-finder mission. The technology being developed for the Keck Nuller along the way will go into the space-based planet finder.
So did those smarty scientists figure out a distinction for planets, then? Is Pluto a real planet or not?
Any coherent body large enough to be detected from such a distance is not likely to be near the debate threashold of size. (At least not on the small end, but "failed stars" may present classification difficulties on the higher end.)
Table-ized A.I.