Gemini Adaptive Optics System Revolutionizes Astrophotography

by Tammy Plotner on January 9, 2012

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Gemini South laser guide star system propagating as the Milky Way rises.

When it comes to astrophotography, most of us would think that space-based telescopes like the Hubble are the epitome of imagining. However, there’s something new to be said about being “grounded”. On December 16, 2011, the Gemini South telescope in Chile revealed its first wide-field, ultra-sharp image… the product of a decade of hard work. By employing a new generation of adaptive optics (AO), the scope produced an incredible look into the densely concentrated globular cluster, NGC 288, and captured stars at close to the theoretical resolution limit of Gemini’s massive 8-meter mirror.

The Gemini Multi-conjugate adaptive optics System (GeMS for short), produced an incredible vision… one of incredible resolution. This new system will allow astronomers to study galactic centers and their black holes – as well as the life patterns of singular stars – with incredible clarity. It’s the largest amount of area ever captured in a single observation – one that’s ten times larger than any adaptive optics systems has ever been able to capture before. It has cause quite a stir in the astronomical community. When Space Telescope Science Institute director Matt Mountain saw the first light image, he praised the GeMS instrument team: “Incredible! You have truly revolutionized ground-based astronomy!”

As the director of the Gemini Observatory, Dr. Mountain was around when the project first began 10 years ago. He was responsible for assembling the team, including Francois Rigaut as the lead scientist to develop the GeMS instrument. And, Rigaut was there for first light… “We couldn’t believe our eyes!” Rigaut recalls. “The image of NGC 288 revealed thousands of pinpoint stars. Its resolution is Hubble-quality – and from the ground this is phenomenal.” Of course, one of the most amazing aspects of the image was how widely spaced the stars appeared, to which Rigaut comments: “This is somewhat uncharted territory: no one has ever made images so large with such a high angular resolution.”

Gemini South’s “first light” image from GeMS/GSAOI shows extreme detail in the central part of the globular star cluster NGC 288. The image, taken at 1.65 microns (H band) on December 16, 2011, has a field-of-view 87 x 87 arcseconds. The average full-width at half-maximum is slightly below 0.080 arcsecond, with a variation of 0.002 arcsecond across the entire field of the image. Exposure time was 13 minutes. Insets on the right show a detail of the image (top), a comparison of the same region with classical AO (middle; this assumes using the star at the upper right corner as the guide star), and seeing-limited observations (bottom). The pixel size in the latter was chosen to optimize the signal-to-noise ratio while not degrading the intrinsic angular resolution of the image. North is up, East is right.

Even though this is an incredible insight, some members of the scientific team which use the Gemini telescope are a bit more reserved in their comments. According to University of Toronto astronomer Roberto Abraham, one of a community of hundreds of astronomers worldwide who uses the 8-meter Gemini telescopes for cutting-edge research: “This is fan-freaking-tastic!!!!!!!” Exuberant? Of course! Even the environmental conditions remained as perfect as they could be for the first run of the GeMS equipment. “We were lucky to have clear weather and stable atmospheric conditions that night,” said Gemini AO scientist Benoit Neichel. “Even despite interruptions of the laser propagation due to satellites and planes passing by, we obtained our first image with the system. It was surprisingly crisp and large, with an exquisitely uniform image quality.”

How is it accomplished? GeMS employs five laser guide stars, three deformable mirrors and a full arsenal of computers to provide a near diffraction limited image to the Gemini South Adaptive Optics Imager (GSAOI, built by the Australian National University) and the infrared-sensitive imager attached to it. This means the smallest detail that can be resolved measures about 0.04 to 0.06 arcsecond over a field of 85 arcseconds squared. Compared to 0.5 arcsecond “seeing limited” at a good viewing location, that’s phenomenal! Once resolution was solved, the next problem was extending the field of view through a technique called Multi-Conjugate Adaptive Optics (MCAO) – an endeavor which borrowed technology from other scientific fields, such as medical imaging.

“MCAO is game-changing,” Abraham said. “It’s going to propel Gemini to the next echelon of discovery space as well as lay a foundation for the next generation of extremely large telescopes. Gemini is going to be delivering amazing science while paving the way for the future.”

Original Story Source: Gemini Observatory News. For Further Reading: Gemini News Release.

About 

Tammy is a professional astronomy author, President Emeritus of Warren Rupp Observatory and retired Astronomical League Executive Secretary. She’s received a vast number of astronomy achievement and observing awards, including the Great Lakes Astronomy Achievement Award, RG Wright Service Award and the first woman astronomer to achieve Comet Hunter's Gold Status.

Anonymous January 9, 2012 at 11:07 PM

Damn nice. Once again the Aussies are fitting out the big scopes with their most cutting edge tech!

IVAN3MAN_AT_LARGE January 10, 2012 at 12:10 AM

Aussie, Aussie, Aussie! Oi! Oi! Oi! ;-)

Anonymous January 10, 2012 at 2:21 AM

Very very cool indeed… Good to see the Aussies performing in astronomy, especially as South Africa is gonna be so busy with the SKA… :P (I know the decision hasn’t come down yet…)

Anonymous January 10, 2012 at 7:06 AM

When I first looked at the picture, I tought it’s like from TV advertisment – with adaptive optics / without AO

Nikolay Kulinich January 10, 2012 at 8:31 AM

News +5!

zetetic elench January 10, 2012 at 1:35 PM

wow, nice results. that’s gotta be satisfying eh? LASERS find yet another application.

Anonymous January 10, 2012 at 1:50 PM

If this technology becomes widespread, as I suspect it may very well do, is the Hubble at risk of becoming completely redundant?

Anonymous January 10, 2012 at 2:49 PM

Not really. Space based observatories have the advantage that they can look at a point for longer than a few hours (providing that the earth doesn’t go in the way). Ground based scopes must stop observations at dawn.
A second point is that the atmosphere blocks a lot of light (apart from optical, of course, where the atmosphere is 100% transparent). It may be that we do not need optical telescopes any more in space, but most parts of infrared and other wavebands are only accessible from space.

However, I am quite sure that the E-ELT will be outfitted with this system or an upgrade (they plan to use 4 guide stars!).

Prof. Michael O. Zimmermann Ph January 10, 2012 at 11:15 PM

Please, the E-VLT and the new E-ELT have, resp. will use the technology.

Anonymous January 11, 2012 at 4:46 PM

I don’t understand you comparison of image quality. If this 8-meter telescope “captured stars at close to the theoretical resolution limit of Gemini’s massive 8-meter mirror” then why is the image only approaching Hubble resolution quaility with Hubble small mirror?

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