Somewhere in the universe’s expanse another livable planet probably exists. It may not be that far - astronomically speaking - from man’s own solar system.
Differentiating that planet's light from its star, however, can be challenging. But an international team led by UC Santa Barbara physicist Benjamin Mazin has built a new instrument to locate planets around the nearest stars. It is the world's largest and most progressive superconducting camera. The team's research has been published in the journal Publications of the Astronomical Society of the Pacific.
The team, which includes Dimitri Mawet of the California Institute of Technology and Eugene Serabyn of the Jet Propulsion Laboratory in Pasadena, California, developed a device named DARKNESS (the DARK-speckle Near-infrared Energy-resolved Superconducting Spectrophotometer), the first 10,000-pixel integral field spectrograph engineered to overcome the limits of traditional semiconductor detectors. It utilizes Microwave Kinetic Inductance Detectors that, along with a large telescope and an adaptive optics system, enable direct imaging of planets around neighboring stars.
"Taking a picture of an exoplanet is extremely challenging because the star is much brighter than the planet, and the planet is very close to the star," said Mazin, who holds the Worster Chair in Experimental Physics at UCSB.
Sponsored by the National Science Foundation, DARKNESS is an endeavor to overcome certain of the technical limitations to detecting planets. It can take the equivalent of numerous frames per second without any dark current or read noise, which is among the main sources of error in other instruments. It also has the ability to establish the wavelength and arrival time of every photon. This time domain information is crucial for telling apart a planet from scattered or refracted light known as speckles.
This technology will lower the contrast floor so that we can detect fainter planets. We hope to approach the photon noise limit, which will give us contrast ratios close to 10-8, allowing us to see planets 100 million times fainter than the star. At those contrast levels, we can see some planets in reflected light, which opens up a whole new domain of planets to explore. The really exciting thing is that this is a technology pathfinder for the next generation of telescopes.
DARKNESS has been designed for the 200-inch Hale telescope at the Palomar Observatory near San Diego, California. DARKNESS serves as both the science camera and a focal-plane wave-front sensor, speedily measuring the light and then transmitting a signal back to a rubber mirror that can form into a new shape 2,000 times a second. This process cleans up the atmospheric warp that causes stars to twinkle by curbing the starlight and enabling higher contrast ratios between the planet and star.
During the past year and a half, the team has used DARKNESS on four runs at Palomar to sort out bugs. The researchers will return in May to gather more data on specific planets and to show their progress in enhancing the contrast ratio.
Our hope is that one day we will be able to build an instrument for the Thirty Meter Telescope planned for Mauna Kea on the island of Hawaii or La Palma. With that, we'll be able to take pictures of planets in the habitable zones of nearby low mass stars and look for life in their atmospheres. That's the long-term goal and this is an important step toward that.