New laser brings clear viewing at Keck Observatory

KAILUA-KONA — A new cutting-edge laser system is taking the twinkle out of the stars for the W.M. Keck Observatory telescopes — but in a good way.

The $4 million laser guide star deployed on Dec. 1 is allowing the scopes’ 10-meter lens to capture “almost perfect” detail of the celestial bodies, with images five times as sharp as the Hubble Space Telescope, the Waimea-based observatory announced on Tuesday.

“We started this process back in 2008,” said Keck’s optical scientist Peter Wizinowich. “It’s taken a long time to develop.”

Here’s how it works: The laser is beamed into the night sky, where it energizes a layer of sodium atoms in the mesosphere roughly 60 miles above the Earth’s surface. The interaction of the laser and naturally occurring sodium atoms creates a glowing artificial star, a near-Earth reference point with sufficient brightness that astronomers can use to adjust their lens for the atmospheric distortion that both causes blurring of their images of space and also creates the twinkling we see when we look at the stars from our own yards.

Keck corrects for these “ripples” in the light with a 6-inch deformable mirror that adjusts 1,000 times a second.

Stars bright enough to allow scientists to measure the atmospheric distortion are rare. Astronomers can project the artificial star and make their measurements and adjustments anywhere in the sky they wish to gaze, said Wizinowich.

This latest advance in adaptive optics will help astronomers more accurately measure the distance between stars, and aid the study of so called “brown dwarfs,” bodies which emit light but are too small to be stars and too large to be planets.

The advance will also help astronomers in the search for “dark matter” and understanding of its structure and properties, among a host of other advantages, Wizinowich said. Dark matter, one of science’s greatest mysteries, cannot be seen but is known to exist — and comprise a huge share of the universe — in part because of its gravitational effect on matter that we can see.

Adaptive optics are not a new thing. Although the new laser is much more powerful, efficient, compact and stable, its forerunner was commissioned on the Keck II telescope as far back as 2004. That early piece of equipment helped astronomers discover the black hole at the center of the Milky Way.

“We implemented the dye laser on Keck II and a solid state laser on Keck I,” Wizinowich said. “Both of these systems were much more experimental in nature and we had to invest considerable effort into making them reliable for routine operation.”

The Next Generation Laser System is the third generation of lasers at Keck Observatory, which has been pioneering the technology on big telescopes, said Keck project manager Jason Chin, in a press release. The laser is a collaboration of W.M. Keck Observatory and the European Southern Observatory, which operates telescopes in northern Chile.

Keck decommissioned the Mauna Kea facility’s dye laser in October to make way for the new technology. The old laser took five to six hours to become operational once it was turned on; the new laser has that time down to five minutes. Manufactured by TOPTICA of Germany and MPBC of Canada, the laser uses a fraction of the power while increasing performance by a factor of 10, according to Keck.