Slashdot Mirror
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.' "
I've replicated the same feat at home using a device I call a "lens cap", except I can significantly beat the 100x reduction of star brightness.
I'll entertain all bids on this technology...
When will we get all our instruments to examine space...in space? I can't imagine a scientific reason to look from the crust of a planet for anything in deep space.
a beowulf clust... oh, sorry... Just had to do it!
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!
It is a good father-son hobby. I built my own 8" newtonian about 27 years ago, dad and I spent a lot of time grinding the mirror, heading down to Meade to buy parts, eyepieces, an equatorial mount, etc. I learned more about my father during that nine month project than I had in my previous sixteen years of existence on this ball of dirt we call the earth.
:-)
We had many years of eyepiece time enjoying and documenting our observations
I still have that telescope, and I think of my recently-departed father whenver I use it.
Oh, yeah, we both learned early on not to drink and grind optics.
-Scott
My other sig is a Glock
I wish the New York Jets had a 'nuller' for stopping some technical touchdowns of their own.
"show me all the blueprint show me all the blueprint show me all the blueprints"
The question I have to ask is why are we looking for planets?! It's almost as if we've totally leapfrogged the part where we actually find a way to get INTO space and TO planets. It's like we're kids looking through the window of a bar wanting to taste beer. Instead of looking at beer and wondering if it tastes good, we kids should be forging some fake id's and finding out for ourselves.
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.
A "nuller" AKA bluetack.
Can this be programmed into cheap telescopes for well known light sources?
Is this the answer to light pollution?
I'm guessing that the answer is "no" and "no", respectively, but I'd be interested to find out why not.
Literalism isn't a form of humor, it's you being irritating.
Unless the people in them were, for some reason too advanced for us to know how, storing the energy emitted by the star, a Dyson sphere would be re-emitting all the energy emitted by the star, but at a lower temperature. Therefore, Dyson spheres should be visible in infrared.
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!
Wow, don't go out on a limb or anything...
"Action without philosophy is a lethal weapon; philosophy without action is worthless."
> 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
Wow, planet finding, so that's what NASA was hookin' up with Google for...
Right now this is something only astronomers are really interested in. It's kind of sneaking under the radar of the public at large. They are going to get a big shock someday. When the first truly Earth-like planet is discovered, with unambiguous signs of a living biosphere (for example, lots of free oxygen in the atmosphere), the psychological impact will be huge.
You don't think so? You think it can't really matter because visiting such a planet, or even sending a robot probe, is too far beyond our capabilities? Logically that may be true, but there's more than logic at work.
Try to imagine what it was like when Galileo pointed his primitive telescope skyward and realized planets weren't mere specks of light -- there were worlds up there! Even though nobody had any idea how to reach them, everyone's view of the universe had to change. From Galileo's time right up through the early 20th century, imaginations ran wild, and every celestial sphere was imagined to be inhabited. There were jungles on Venus, canals on Mars!
In the last 60 years or so, in some ways our view of the universe has regressed. Now we've looked around our solar system, and it's been a bit of a letdown. Mere specks of light have been replaced by barren balls of rock, or ice, or gas. In their minds, people have started sliding outer space back into the category of the uninteresting and unimportant.
When the first news comes back of an Earth-like planet. . . when one is shown to have life. . . when we get a fuzzy image of another cloud-swirled blue marble out there somewhere. . . It'll be just like Galileo all over again. Nobody will have any clear idea how to reach those worlds, but imaginations will run wild. And I think that's a good thing.
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.