UH astronomers get closer look at Whirlpool Galaxy


By PETER SUR

Tribune-Herald staff writer

Astronomers with the University of Hawaii Institute for Astronomy unveiled the first image of an eye-in- the-sky instrument that they say will open a new chapter in infrared technology.

The UH 2.2-meter (88-inch) telescope shows the central disk and spiral arms of one of the most picturesque objects in the night sky — the Whirlpool Galaxy — seen head-on from 23 million light-years away.

The monochrome image shows detail in the galaxy’s arms, but what gets astronomers excited is the new 16-megapixel digital sensor on the camera.

“The level of detail revealed by digitally zooming in anywhere in the 16-megapixel image is truly incredible,” said Don Hall, former IfA director and principal investigator on the project.

The image might not be as sharp as an image from the Hubble Space Telescope, but it’s a start. Viewing conditions on Mauna Kea weren’t ideal, the sensor is being created on an experimental basis and it would be sharper with the addition of a laser guide star adaptive optics system. But it’s notable for other reasons.

This is the first time a sensor with so many infrared pixels has been trained on the night sky, and it points the way toward the installation of arrays of the sensors on more advanced telescopes.

The sensor has 16 times the pixel count of an earlier sensor developed by the same team and installed on the Hubble Space Telescope, and it has four times the pixel count of the largest infrared sensors now in use at telescopes around the world.

An imaging device of this size might not sound impressive compared with the latest professional digital cameras from Canon or Nikon, but engineers have had to work around silicon’s insensitivity to infrared radiation. To do this, infrared-sensitive crystals must be electrically connected to each of the 16 million pixels. In addition to this, the pixels had to be made several hundred times larger than the size of pixels in an iPhone, resulting in one of the largest silicone chips ever produced.

The result, described as the culmination of a 20-year, $15 million effort, was the sensor and the image of the Whirlpool Galaxy.

The image field is relatively wide for a Mauna Kea telescope — about half the diameter of the moon.

“By infrared standards, that’s incredible compared to what we’ve been able to do in the past,” Hall said.

He called the sensor a “proof of technology concept.”

The sensor’s development was by the National Science Foundation. Hall said the amount of the reward was slightly less than $7 million, enough to create 20 sensors. Engineers made six sensors for the first run; the sensor that was used to view the Whirlpool Galaxy was the best of the bunch, Hall said. A second run is planned with 10 or so sensors as a precursor to commercial production for professional observatories around the world.

Email Peter Sur at psur@hawaiitribune-herald.com.