* Astronomy

NULLING MODE AT KECK OBSERVATORY
First results from a new scientific instrument at W. M. Keck Observatory are helping scientists understand the physics behind recurrent novae, a type of cataclysmic star system. The results are overturning long-standing assumptions about powerful explosions called novae and have produced the first unified model for a nearby nova called RS Ophiuchi.

We were getting ready for a routine engineering run when all of a sudden the nova went off. It was very bright and easy to observe, so we took this opportunity and turned it into gold - team member Marc Kuchner of NASAs Goddard Space Flight Centre in Greenbelt, Md.

The nulling mode of the Keck Interferometer is part of the NASA-funded Keck Interferometer, which combines starlight using two 10-meter  telescopes. In this mode, the interferometer suppresses the blinding light of a star so researchers can study the surrounding environment. The instrument helps researchers observe very faint objects near bright sources and produces ten times more resolving power than a single Keck telescope working alone. It is the only instrument of its kind in operation.
The nulling mode was developed to search for dust around nearby stars, which make finding planets around these stars more difficult.

If the dust were by itself, it would be easy to detect with Keck.  But the star is so much brighter, that something has to be done to block the light, which is what the nuller does. But this technique turns out to be useful for lots of other kinds of objects, including this one, where dust is near a star that just went nova - Dr. Rachel L. Akeson, Keck Interferometer project scientist at the Michelson Science Centre at Caltech.

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Geoff Marcy has looked at 85 different stars this evening, but he has yet to actually see a single one of them.
The giant Keck telescope he is using, on the summit of Hawaii's Mauna Kea volcano, is sending images straight to a digital camera, to be analysed by a computer.

"There are no eyepieces anywhere. In fact, we don't have an eyepiece for the Keck telescope" - Geoff Marcy , astronomy professor at the University of California, Berkeley.
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A new sodium laser is giving 50 times more sky coverage to the atmospheric-correcting technology known as adaptive optics on the Keck II telescope at Mauna Kea, Hawaii. The laser lets scientists explore most of the sky with adaptive optics and gives them the capability to study objects that were previously too faint to be seen with the system. Since 1999, Keck Adaptive Optics has provided 10 times more resolving power than what could otherwise be achieved from the ground. The results are producing infrared images from the ground comparable – and often better – than those taken from space.

"This has been the most exciting technological and scientific breakthrough for the Observatory in the last decade. It may forever change the way we do astronomy from the ground. We are entering a new, extraordinary era of discovery" - W. M. Keck Observatory Director Fred Chaffee.

After just one year of regular scientific use, the Keck Laser Guide Star Adaptive Optics system is producing spectacular results and advancing research in several fields of astronomical study. Findings include the discovery of new asteroids, moons and planetoids in our solar system, the detection of new brown dwarf binary systems -- including a strange new kind of binary, observations of physical processes taking place near a supermassive black hole, and new findings about extremely distant supernovae and young galaxies.

The technique of adaptive optics uses visible light from a bright star to measure and correct for atmospheric distortions at infrared wavelengths. But only about two percent of the sky has stars bright enough to use with adaptive optics. The Keck Laser Guide Star system overcomes this limitation by creating an artificial star anywhere in the sky. The W. M. Keck Observatory is the only 8 meter class facility in the world currently providing this capability to observers.

"The wish list for astronomers is pretty simple. First, they want the highest-quality images that can possibly be obtained. Second, they want to look anywhere they want to in the sky. The laser guide star makes both these wishes come true" - Dr. David Le Mignant, adaptive optics scientist at the W. M. Keck Observatory.

Operating at nearly 1,000 times a second, the Keck adaptive optics system minimizes the blurring effects of Earth’s atmosphere to provide infrared images 10 times better than what can be achieved from the ground. Without any correcting technology, the best telescopes on Earth are limited to an average “seeing” ability, or resolving power, of about 0.5 arcseconds, the equivalent of being able to distinguish an object the size of a blueberry from 4 kilometres away. But with adaptive optics, atmospheric blurring is removed, producing a resolving power of about 50 milliarcseconds or better. This improvement is like looking at a penny from 4 kilometres away and being able to read the words, “ONE PENNY” stamped on the coin.

"We are shattering a limitation for ground-based observations -- astronomers can now uncover and study fine structures in extremely faint objects anywhere, within and beyond our galaxy. This new data will particularly complement present deep sky surveys which study the formation of galaxies in the universe" - Dr. Le Mignant.

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