Following up on yesterday’s news about spectrometer advances at the Automated Planet Finder installation at Lick Observatory comes news of a different kind of telescope breakthrough. A radio telescope in Shanghai was linked via computer network to a five telescopes in Europe and another in Australia to study the active galaxy 3C273. A galaxy with a major black hole at its core is obviously interesting, but what stands out in the recent experiment is the working procedure. Never has very long baseline interferometry been pushed to such extremes.
Image: Widely spaced telescopes combine their data to boost resolution, creating a kind of ‘world telescope.’ Credit: Paul Boven/JIVE. Satellite image: Blue Marble Next Generation, courtesy of NASA Visible Earth (visibleearth.nasa.gov).
The idea of interferometry is straightforward: Combine signals from multiple telescopes to produce higher resolution data than could be obtained by any of the telescopes individually. Spread your telescopes out widely and use enough of them and the resultant image approximates what you would see from a single telescope with the diameter of your interferometer array. A telescope the size of Earth? Earth’s diameter is 12,750 kilometers, and the most widely spaced telescopes in the test were 12,304 kilometers apart, so in a way, yes.
“This is the first time we’ve been able to instantaneously connect telescopes half a world apart,” says Tasso Tzioumis (Australia Telescope National Facility). And the key word is indeed ‘instantaneous.’ Working with data streaming at 256 MB per second, researchers could combine the signals at a European research center, feeding them into a digital processor before forwarding them to Xi’an, China, where they were observed by experts at an advanced networking conference.
Thus another example of the transformative effect of computer networking on astronomical observation. We’ve had very long baseline interferometry in our arsenal for a while now, but linking widely separated telescopes used to take weeks or even months to produce solid data, as Dr. Tzioumis notes in this news release:
“We used to record data on tapes or disks at each telescope, along with time signals from atomic clocks. The tapes or disks would then be shipped to a central processing facility to be combined.”
Now we’re doing the job almost in real time thanks to the massive computer power and network links deployed for the purpose. Such results remind us that even as we plan for more ambitious space-based telescopes, the results we’ll be able to obtain from observatories here on Earth should continue a sharp climb in range and accuracy. Then consider how space missions like the ESA’s DARWIN will use interferometry in separating a planetary signature from a distant star’s light. The more we polish the technique now, the more remarkable the results to come.
For more on interferometry and its significance, check this podcast featuring Dr. Tzioumis. Also see this statement from the Joint Institute for Very Long Baseline Interferometry (JIVE) in The Netherlands.
What I find more than a little weird is that, if this keeps up, we might spot actual life bearing worlds around other stars before we even do a reasonable search of our own solar system for life. Imagine being able to say ‘yes there is life on planet x of star y’ which is 100 trillion kilometers away when we have to yet rule out life on mars 100 million kilometers away, or europa only a couple of hundred million kilometers away. Just incredible.
More than a little weird is right! From a slightly different angle, I always assumed as of twenty years or so ago that we would need a fast interstellar flyby probe to really get a good look at any extrasolar planets we wanted to investigate. Now it’s becoming clear that we’ll have pretty solid information long before we send an interstellar probe anywhere, and can choose our target list with great precision. Wondrous…
Umm, you can’t do interferometry like this since the photodetectors don’t store phase so you don’t get destructive interference. At least from my layman understanding. You’d have to keep it optical the whole way, and the path length matters…
Ah, the key of course here is that it’s radio astronomy, where the antennas *can* store the phase!
It’d be a tad harder with visible frequencies! :)
Hi All
What’s new is that the scopes are linked up data-wise in almost real time. Whole Earth Radio Telescopes have been used in interferometry for quite a few years now – the baseline can be extended by using radio telescopes on satellites too.
Now here’s a dream tiger fantasy: set up a couple more telescopes on the moon (poles?) and synthesize a 250000 mile aperture! The resolution would boggle he mind.
High Resolution Radio Astronomy Using Very Long Baseline Interferometry
Authors: Enno Middelberg, Uwe Bach
(Submitted on 20 Mar 2008 (v1), last revised 22 Mar 2008 (this version, v2))
Abstract: Very Long Baseline Interferometry, or VLBI, is the observing technique yielding the highest-resolution images today. Whilst a traditionally large fraction of VLBI observations is concentrating on Active Galactic Nuclei, the number of observations concerned with other astronomical objects such as stars and masers, and with astrometric applications, is significant. In the last decade, much progress has been made in all of these fields. We give a brief introduction into the technique of radio interferometry, focussing on the particularities of VLBI observations, and review recent results which would not have been possible without VLBI observations.
Comments: 77 pages, needs aas_macros.sty, accepted by Reports on Progress in Physics
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0803.2983v2 [astro-ph]
Submission history
From: Enno Middelberg [view email]
[v1] Thu, 20 Mar 2008 07:28:33 GMT (800kb,D)
[v2] Sat, 22 Mar 2008 22:26:22 GMT (800kb,D)
http://arxiv.org/abs/0803.2983
January 31, 2009
China Building Huge 500-Meter Radio Telescope
Written by Nancy Atkinson
Official ground-breaking ceremonies took place for a gigantic new 500 meter diameter radio telescope in China which will allow astronomers to detect galaxies and pulsars at unprecedented distances.
The $102 million facility, known as the Five-hundred-meter Aperture Spherical Telescope (FAST), will have a collecting area more than twice as big as the 305 meter diameter radio telescope at Arecibo Observatory in Puerto Rico, which has been the world’s largest since it opened in 1964. Not only that, the new telescope will also have the ability to change its shape and move the position its focus.
Like Arecibo, the new telescope will sit in a natural depression that already is close to the shape of the collecting surface, simplifying the support structure and shielding the telescope from stray human-generated radio waves. The location is quite remote, about 170 km by road from the Guizhou Province’s provincial capital Guiyang, making it unusually radio-quiet, says Nan Rendong, FAST chief scientist and a researcher from the National Astronomical Observatories at the Chinese Academy of Sciences, in an article in Physicsworld.com.
The site’s potential for long, uninterrupted observations — coupled with the telescope’s huge size, which will give it twice the sensitivity of Arecibo — means that researchers there will be able to detect objects like weak, fast-period pulsars that are too faint to be measured accurately by smaller instruments.
“The FAST science impact on astronomy will be extraordinary,” Nan said, adding that although the telescope is located in China, once it is completed in 2014 it will be open to astronomers from around the world.
Full article here:
http://www.universetoday.com/2009/01/31/china-building-huge-500-meter-radio-telescope/