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Giant Radio Telescope Tackles Black Holes
Cosmiverse ^

Posted on 04/03/2002 8:18:40 AM PST by Texaggie79

Giant Radio Telescope Tackles Black Holes
April 2, 2002 08:00 CST

Space exploration requires a great deal of imagination. With the international Space Very Long Baseline Interferometry mission (VLBI), supported by NASA until last month, a global team of scientists and engineers not only imagined a telescope larger than Earth, they actually created it.

Black holes are perhaps the most elusive cosmic entity. Although we cannot see black holes, astronomers have confirmed their existence from the behavior of objects near the areas thought to be black holes. To learn more about these giant mysteries, scientists have to get a closer look at them. The very successful international joint mission has propelled astronomers one step closer to understanding the complex mechanisms that control black holes.

Although people generally think of black holes as all-consuming vacuums, they also eject material at speeds nearing the speed of light. The material emits radio waves, which can be detected by radio telescopes.

Right image: Artist's concept of Very Long Baseline Interferometry space and ground radio telescopes that, together, created a virtual telescope three times Earth's diameter.

However, for a radio telescope to be able to observe details as fine as those observed by the Hubble Space Telescope, it has to be roughly 100,000 times larger than Hubble, or about 161 kilometers (100 miles) in diameter, said Dr. David Murphy, a JPL radio astronomer currently visiting the Japanese Space Agency.

To expand the resolution capabilities of ground radio telescopes, many radio telescopes can observe simultaneously to effectively "create" a telescope as big as the array of telescopes. However, even radio telescopes peppered across the globe aren’t sufficient to see the necessary details around black holes.

So a Japanese-built radio telescope in space was added to an array of 40 ground telescopes. The resulting "radio telescope" was as big as the orbit (32,187 kilometers or 20,000 miles). It revealed details in the observed objects more than 100 times finer than the Hubble Space Telescope can see. Sixteen different nations participated in the ambitious five-year mission.

"It was the United Nations of radio astronomy," said Dr. David Meier, a JPL astrophysicist. "To see different countries working together to build a single, very complex instrument was very impressive."

Above image: Radio images taken during the mission near the supermassive black hole in the quasar 1928+738

The project was "perhaps the most complicated science mission ever," according to project scientist Dr. Bob Preston of JPL.

The space telescopes relayed radio signals from the celestial sources to NASA’s Deep Space Network, a set of communication antennas on three different continents, as well as to sites at the U.S. National Radio Astronomy Observatory (NRAO) and in Japan. These signals, along with those received at ground radio telescopes, were recorded on high-density videotape.

The videotapes were then sent to a common facility to be ‘read’ by a correlator that synchronizes tapes from every receiver to within one millionth of a second. With the help of computer software that mimics the focus of a camera, the radio waves become celestial images.

"It’s like looking at a picture made with radio waves by a camera that’s larger than Earth," said Dr. David Meier, JPL astrophysicist. "We are able to zoom into the centers of black holes closer than any other imaging technique."

Left image: The Very Long Baseline Array is a global interferometer combining signals from radio telescopes from the Virgin Islands to Hawaii. This is equivalent to a telescope nearly as large as the earth. Click image to enlarge.

In addition to many awe-inspiring pictures, scientists have gained extensive scientific information from the mission, with results appearing in more than 200 scientific papers. A lot has been learned at the most fundamental level about the environment near super massive black holes. Material escaping in jets from black holes in the center of galaxies was confirmed to be moving nearly at the speed of light. The structure, time-variability and magnetic fields of material near the black holes provided additional clues to the nature of these violent regions of space.

The mission also concentrated its enormous magnification power on other energetic celestial objects, such as pulsars. A pulsar is a neutron star, an extremely dense object formed by a supernova explosion at the end of a massive star's lifetime. The mission also studied molecular masers in star-forming regions. A maser is a cousin of the laser that transmits a highly focused beam of microwave energy.

In the future, radio astronomy will become even more precise. If selected by NASA, the Advanced Radio Interferometry between Space and Earth mission will further the study of supermassive black holes by obtaining images with resolutions 3,000 times greater than NASA's Hubble Space Telescope.

Source: NASA



TOPICS: Astronomy; Science
KEYWORDS: blackholes; crevolist; space

1 posted on 04/03/2002 8:18:40 AM PST by Texaggie79
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To: petuniasevan; edwin hubble; longshadow; blam; jlogajan; A. Pole; e_engineer; Doctor Stochastic...
ping
2 posted on 04/03/2002 8:20:42 AM PST by Texaggie79
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To: VadeRetro; jennyp; junior; longshadow; crevo_list; RadioAstronomer; Scully; Piltdown_Woman...
Ping.
3 posted on 04/03/2002 8:29:50 AM PST by PatrickHenry
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To: PatrickHenry
Pong.
4 posted on 04/03/2002 8:36:23 AM PST by VadeRetro
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To: PatrickHenry
Space exploration requires a great deal of imagination

Even with rudimentary imagination, it is more productive in an atmosphere of deliberate consilience.

5 posted on 04/03/2002 8:44:02 AM PST by RightWhale
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To: RightWhale
I hate "paradigm." I hate "synergy." And now I hate "consilience."
6 posted on 04/03/2002 8:56:26 AM PST by VadeRetro
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To: VadeRetro
I forgot I hate "meme."
7 posted on 04/03/2002 8:57:12 AM PST by VadeRetro
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To: Texaggie79;all
Layman question:

As I understand it, a Black Hole is a "tear" caused in three-dimensional space-time by an infinitely dense object.

All depictions I've ever seen of Black Holes show them to be like infintely deep whirlpools. I assume that these holes "fall off" in all directions, depending on their formation.

So what determines the direction in which a Black Hole forms? Are there variations in the "density" of space-time, such that different Black Holes "fall off" in different directions?

Also, do all known black holes "rotate" in the same direction?

8 posted on 04/03/2002 9:01:02 AM PST by martin_fierro
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To: VadeRetro
Use a word three times in context, and it is yours. :)
9 posted on 04/03/2002 9:07:01 AM PST by RightWhale
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To: RightWhale
Even with rudimentary imagination, it is more productive in an atmosphere of deliberate consilience.

You know what you can do with your "deliberate consilience." If we were doing space exploration in a small, enclosed ship, I suspect we'd have a knife fight before very long.

10 posted on 04/03/2002 9:08:57 AM PST by PatrickHenry
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To: martin_fierro; Radio Astronomer; ThinkPlease; Physicist
As I understand it, a Black Hole is a "tear" caused in three-dimensional space-time by an infinitely dense object.

First, I'm not sure "tear" is a good term for it. Second, space-time is FOUR dimensional (in Special Relativity, at least), not three. A better way to think of it is that all masses cause a localized curvature of spacetime; the bigger the mass, the greater the curvature. A Black Hole forms when the mass is SO large (and the density so high) that the curvature of Space-time becomes infinite.

All depictions I've ever seen of Black Holes show them to be like infintely deep whirlpools. I assume that these holes "fall off" in all directions, depending on their formation.

So what determines the direction in which a Black Hole forms? Are there variations in the "density" of space-time, such that different Black Holes "fall off" in different directions?

There's no "direction" the Black Hole is falling "into." The Black hole is located exactly where the center of mass of the material that formed the Black Hole was just BEFORE the BH formed. Another way to think of it is that the localized Spacetime curvature caused by a mass has no "direction" either; it causes a uniform curvature in all directions. The space-time curvature of the BH is only moreso.

Also, do all known black holes "rotate" in the same direction?

The short answer is I'm not sure, but I expect the rotational distribution of BH is about the same as the rotational distribution of other celestial matter, such as stars, clusters, galaxies, etc. It is interesting that you ask, in that rotation (actually angular momentum) is one of the few physical characteristics a BH has. The others are mass and (I think) electric charge.

I hereby defer to those more knowledgeable than I am on this subject whom I've pinged to revise and extend my remarks as needed to correct any errors or ommissions.

11 posted on 04/03/2002 9:29:34 AM PST by longshadow
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To: PatrickHenry,VadeRetro
Is this National Hate A Word Day?

If we want to use a defined, autolimited language, why not just speak Arabic or French?

12 posted on 04/03/2002 9:33:23 AM PST by RightWhale
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To: longshadow
the localized Spacetime curvature caused by a mass

What if spacetime curvature and mass are coincidental, circumstantial, and are not cause and effect. Or what if spacetime curvature causes mass? There was a comment quite a while back pertaining to the old vortex theory of gravity, that if a planet were not there, say, Jupiter, its gravitational field would still be present, that the presence of gravity causes the planet to form right there. This is just to point out that these are all hypotheses and that flat statements might close some doors to speculation.

13 posted on 04/03/2002 9:42:08 AM PST by RightWhale
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To: longshadow
The others are mass and (I think) electric charge.

I don't think electric charge survives. Just mass and spin. But the mass which was the big bang probably wasn't even spinning, in that there was no reference frame for determining spin.

14 posted on 04/03/2002 9:42:17 AM PST by PatrickHenry
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To: PatrickHenry
Thanks for the ping. Wish he wouldn't have said this,

"It was the United Nations of radio astronomy," said Dr. David Meier, a JPL astrophysicist. "To see different countries working together to build a single, very complex instrument was very impressive."

15 posted on 04/03/2002 9:49:22 AM PST by <1/1,000,000th%
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To: RightWhale
Is this National Hate A Word Day?

Ugly, trendy neologisms are the noiseless equivalent of fingernails on a blackboard.

16 posted on 04/03/2002 9:55:01 AM PST by VadeRetro
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To: RightWhale
Is this National Hate A Word Day?

I don't know, but as long as we're getting things off our chests, there are some constructions I hate:

Boy, those grate on me.

I also hate the word "twee".

17 posted on 04/03/2002 9:55:59 AM PST by Physicist
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To: PatrickHenry; Physicist
I don't think electric charge survives. Just mass and spin. But the mass which was the big bang probably wasn't even spinning, in that there was no reference frame for determining spin.

I'm sure there are THREE parameters that describe a BH; if electric charge ISN'T the third one (after mass and angular momentum), then I'm not sure what it would be...

18 posted on 04/03/2002 10:05:32 AM PST by longshadow
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To: Physicist
.... but you can't convince him to do something. You persuade him to do something.

OR, in more technical terms: "persuade" takes the infinitive; "convince" does not.

19 posted on 04/03/2002 10:07:56 AM PST by longshadow
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To: Physicist
You may have been a pupil in my grandfather's English class. Not your everyday, ordinary English teacher, he knew rules of grammar such as are not often written in textbooks. He corresponded regularly in seven languages, including with a German he met and took prisoner in the trenches in Flanders during WW I.
20 posted on 04/03/2002 10:09:52 AM PST by RightWhale
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To: <1/1,000,000th%
"It was the United Nations of radio astronomy," said Dr. David Meier, a JPL astrophysicist.

He meant they bashed American astronomy all day long, and then went home to the latest issue of "Ap-Jay".

21 posted on 04/03/2002 10:16:12 AM PST by Physicist
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To: PatrickHenry
Ah, here it is; the "Black Hole has No Hair" Theorem:

"Another way of stating this is that outside of the event horizon all properties of the matter that formed it are gone except for the total mass-energy, rotation, and electric charge: this is sometimes called the Black Hole Has No Hair theorem."

22 posted on 04/03/2002 10:17:59 AM PST by longshadow
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To: PatrickHenry; longshadow
Black holes can have electric charge.
23 posted on 04/03/2002 10:18:11 AM PST by Physicist
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To: RightWhale
What if spacetime curvature and mass are coincidental, circumstantial, and are not cause and effect. Or what if spacetime curvature causes mass? There was a comment quite a while back pertaining to the old vortex theory of gravity, that if a planet were not there, say, Jupiter, its gravitational field would still be present, that the presence of gravity causes the planet to form right there. This is just to point out that these are all hypotheses and that flat statements might close some doors to speculation.

Nor can I prove that Invisible Star Goats are NOT pushing the planets around the Sun, instead of reacting to the influence of the spacetime curvature (gravitation).

The point is that General Relativity is a Theory that fits all available evidence and which has survived all attempts at falsification. "Vortex" theories of gravitation notwithstanding, no other gravitational theory can make that claim.

24 posted on 04/03/2002 10:25:17 AM PST by longshadow
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To: martin_fierro
All depictions I've ever seen of Black Holes show them to be like infintely deep whirlpools.

The whirlpools that are drawn around black holes (as in the above illustration) are accretion disks. Accretion disks form because the infalling matter will, in all likelihood, have a nonzero net angular momentum. The angular momenta of the infalling objects all cancel each other in every direction but one (the axis of the disk). The matter left in the disk goes into orbit around the black hole.

The accretion disk of a black hole actually wouldn't look like a normal accretion disk as shown above. This is because light bends around the black hole, with the result that if you are looking at the near side of the disk almost edge-on, you'll be looking at the far side of the disk face-on. It looks sort of like a misshapen LP record with a 90-degree fold in it. (See an example here.)

25 posted on 04/03/2002 10:33:41 AM PST by Physicist
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To: longshadow
The vortex theory of gravity wasn't disproved, but it was replaced with the current theory. Apparently the vortex theory was not as easy to put into mathematical terms at the time, over 100 years ago. It wasn't necessarily wrong, just not particularly useful. The vortex theory of gravity seems to be at the root of R. C. Hoagland's recent journalistic work in digging up old, discarded physics, trying to re-open old lines of inquiry.
26 posted on 04/03/2002 10:33:43 AM PST by RightWhale
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To: Physicist; longshadow
Black holes can have electric charge.

Oh yeah? Well a lot of good it does 'em.

27 posted on 04/03/2002 10:57:18 AM PST by PatrickHenry
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To: Physicist
LOL! That's what I was thinking.
28 posted on 04/03/2002 11:45:32 AM PST by <1/1,000,000th%
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To: RightWhale
The vortex theory of gravity wasn't disproved, but it was replaced with the current theory.

When a new theory supplants an old one, it is usually for a good reason.

The practical issue is that we have yet to find an instance where the current theory of gravitation gives an incorrect result. Hence, there is no basis for "vortex" gravitation (or any other theory) to replace it...... for the moment.

I have a great deal of trouble with Hoagland's stuff; latching onto the "Face on Mars" hysteria, combined with all his conspiratorial speculation he's into, really makes him sound like a lunatic rather than a serious scientist, which he once was.

29 posted on 04/03/2002 12:01:54 PM PST by longshadow
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To: Physicist;longshadow
Ow. Now my head hurts.

<|:)~

30 posted on 04/03/2002 12:27:54 PM PST by martin_fierro
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To: martin_fierro
Ow. Now my head hurts.

Well, that ought to teach you to ask impertinent questions!

Just kidding.... you actually asked some pretty good questions, and there's a wealth of talent roaming around FR who can help explain some of these concepts.

Without folks like you ASKING the questions, nobody would bother answering them.

Or, in the immortal words of the founder of "Faber College" in "Animal House":

"Knowledge is good."

31 posted on 04/03/2002 12:36:52 PM PST by longshadow
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To: longshadow
Just whatever you do, don't put me on Double Secret Probation!
32 posted on 04/03/2002 12:46:52 PM PST by martin_fierro
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To: martin_fierro
Just whatever you do, don't put me on Double Secret Probation!

Didn't you know....... the act of asking a question in itself is grounds for the DSP status!

Respectfully Submitted,

Dean Wormer

33 posted on 04/03/2002 12:50:57 PM PST by longshadow
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To: longshadow
a serious scientist, which he once was.

I don't know if he was ever a scientist. He was certainly a science journalist and planetarium manager. He was very good, too. A scientist? No, not formally. But perhaps in spirit.

The Face on Mars is a joke, not for the purpose of having fun and playing with the gullible, but for encouraging people, meaning Congress and NASA, to let us all share in the exploration of our solar system.

Hoagland's subspace or hyperspace physics, or whatever title he gives it, is not his, he is the journalist. Although the mathematics of the day was not up to the task of dealing with the idea, it may come back, probably in an altered form suitable for computer modelling. Along those lines stay tuned for developments of the fifth dimension out of Princeton and watch for Nima Arkani-Hamed, who may have something to say later.

34 posted on 04/03/2002 1:27:45 PM PST by RightWhale
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To: Texaggie79
VLBI is so cool. I had the opportunity to reduce VLBI data with this sort of thing when I was a wee grad student (and I even published!). I recently came upon the opportunity to possibly do more work along these lines, and I'm contemplating the offer. It's a very exciting field, with great opportunities.
35 posted on 04/03/2002 1:39:57 PM PST by ThinkPlease
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To: RightWhale
Along those lines stay tuned for developments of the fifth dimension out of Princeton and watch for Nima Arkani-Hamed, who may have something to say later.

Speaking of Nima Arkani-Hamed, I had the pleasure of showing him around the physics department here at Penn a couple of weeks ago, when he was the colloquium speaker. His talk was entitled "Deconstructing Dimensions" (in an intentional jab at postmodern blather). While he's famous for proposing that there exist large extra spatial dimensions, in this talk he was talking about eliminating dimensions! The subtitles of his talk were "Extra Dimensions Suck" and "Destroy All Dimensions".

He's come up with a way in which field theories can dynamically generate "apparent" or "effective" extra dimensions that behave so much like the real thing, that the possibility can't be ruled out that there are fundamentally fewer than the four dimensions we believe ourselves to live in.

He even had some experimental tests that could distinguish between real dimensions and "theory space" dimensions. First we have to discover the graviton, though.

36 posted on 04/03/2002 2:03:36 PM PST by Physicist
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To: Physicist
Now it's virtual dimensions, is it? Somehow that doesn't do much to reassure us ordinary people that someone has a clue to what reality might be.
37 posted on 04/03/2002 2:14:01 PM PST by RightWhale
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To: ThinkPlease
VLBI is so cool.

Indeed it is! :)

38 posted on 04/03/2002 2:22:51 PM PST by RadioAstronomer
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To: martin_fierro; longshadow
Ow. Now my head hurts.

Hang around with this crowd and you'll get headaches frequently! LOL

39 posted on 04/03/2002 2:38:20 PM PST by Aracelis
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To: Texaggie79
"... It revealed details in the observed objects more than 100 times finer than the Hubble Space Telescope can see."

Ok... for a standard telescope (approximately):

. resolution (theta) = 1.22 Lambda/Diameter

where theta is the angle of resolution,
Lambda is the wavelengh in meters
and Diameter is the telescope's diameter in meters.

So, the Hubble has an average wavelength (lambda) of half-micron, and a diameter of 2m. (rounded).

Then, if VLBI has an effective diameter (baseline) is 30,000,000 meters (30k km) and the wavelength is decimeter, then it would have 100 times the resolution of Hubble @ half micron wavelength and 2 meter diameter.
Works out to a good approximation.

Amazing... a radio telescope system with 100 times the resolution of Hubble....
Then imagine a visual interferometer system with Earth-moon baseline!!
Images of extra-solar planets.

40 posted on 04/03/2002 3:21:49 PM PST by edwin hubble
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To: ThinkPlease
It's a very exciting field, with great opportunities.

Is there any theoretical or practical limitation that prohibits doing VLBI with OPTICAL instruments?

I should think the resolution would be, dare I say it: absolutely "ASTRONOMICAL!"

41 posted on 04/03/2002 3:45:07 PM PST by longshadow
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To: edwin hubble
Then imagine a visual interferometer system with Earth-moon baseline!! Images of extra-solar planets.

Ah, you beat me to it by 24 minutes!

42 posted on 04/03/2002 3:48:34 PM PST by longshadow
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To: longshadow
Visual wavelength interferometry...br> Yes, it can be done...
Synchronizing, aligning, with an Earth-moon baseline will be the challenge
but by the time we are ready to install on the moon, we would have the technology.

Eventually a baseline of Jupiter-orbit size.

43 posted on 04/03/2002 3:59:33 PM PST by edwin hubble
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To: edwin hubble
Eventually a baseline of Jupiter-orbit size.

Heck, a continent-wide baseline would produce prodigious results at optical frequencies..... why wait?

44 posted on 04/03/2002 4:07:05 PM PST by longshadow
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To: longshadow
Here's a good overview paper on optical interferometry in space, National Academies of Science

Space Science in the Twenty-First Century
Imperatives for the Decades 1995 to 2015
Astronomy and Astrophysics

Nat. Academies overview paper on optical interferometry in space

45 posted on 04/03/2002 4:11:44 PM PST by edwin hubble
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To: edwin hubble
Here's a good overview paper on optical interferometry in space, National Academies of Science

Thanks!

46 posted on 04/03/2002 5:16:59 PM PST by longshadow
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To: longshadow;edwin hubble
We also just hired an optical interferometer guy for one of our instrumentation positions. He's done some pretty neat stuff, and we're definitely looking forward to his work when he gets here. The problem with getting such high resolution in the optical is that you need a source with relatively high surface brightness that you can both see and resolve the source at the same time. There's another guy out there who does optical interferometry of Wolf-Rayet stars, really young stars that are sloughing off their outer atmospheres due to radiation pressure. He found, using local optical interferometry (at Keck, I think), that several Wolf-Rayet stars have companions, an effect that couldn't have been discovered without interferometry. Really cool stuff. Both interferometry and high mass stars in the same project.
47 posted on 04/04/2002 4:57:14 AM PST by ThinkPlease
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To: ThinkPlease
The problem with getting such high resolution in the optical is that you need a source with relatively high surface brightness that you can both see and resolve the source at the same time.

Ah, so extended faint phenomona are not good targets for OI.

Bummer.

48 posted on 04/04/2002 8:35:26 AM PST by longshadow
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