New Telescope Optics Can Directly View Exoplanets By Hiding Interfering Starlight

By Rebecca Boyle
June 11th, 2012
popsci.com

Sifting Starlight These two images show HD 157728, a nearby star 1.5 times larger than the sun. The star is centered in both images, and its light has been mostly removed by an adaptive optics system and coronagraph belonging to Project 1640, which uses new technology on the Palomar Observatory’s 200-inch Hale telescope to spot planets.

For now, the thousands of potential exoplanets discovered in the past two years are little more than curvy dips on a graph. Astronomers using the Kepler Space Telescope pick them out by examining the way they blot out their own stars’ light as they move through their orbits. But if astronomers could block out the stars themselves, they may be able to see the planets directly. A new adaptive optics system on the storied Palomar Observatory just started doing that — it’s the first of its kind capable of spotting planets outside our solar system.

The new system is called Project 1640, and it creates dark holes around stars that may harbor planets. It removes the blinding glare of starlight so astronomers can see the exoplanets. This is extremely hard to do, said Charles Beichman, executive director of the NASA Exoplanet Science Institute at Caltech. “Imagine trying to see a firefly whirling around a searchlight more than a thousand miles away,” he said in a statement.

Coronagraphs are used to block out starlight so scientists can see what lurks around the stars. But even when you block the brightest light, about half of it can still fuzz up an image, creating speckles and background light that will interfere with images of potential planets. To address this speckly starlight, Project 1640 uses the world’s most advanced adaptive optics system, and four separate instruments on Palomar’s 200-inch Hale telescope that image the infrared light generated by young, warm planets orbiting stars.

Beta Pictoris: This image of the star Beta Pictoris shows a huge planet orbiting the star. The pale blue dots at the center are the planet, shown in two orbital configurations. The black disk is where the star would be; it’s blocked by a coronagraph. But more starlight is visible at the sides, which could potentially be outshining other, smaller planets in this solar system. A new adaptive optics system can remove this shine, too, unveiling new worlds around distant stars.

Its adaptive optics system can make more than 7 million active mirror deformations per second, with a precision level better than one nanometer. Its wave front sensor, which detects the atmosphere-caused deformations of light hitting the telescope, is also sensitive to a nanometer. As the system detects perturbations in the light waves coming into the telescope, it continually adjusts and deforms to block out the light as effectively as possible.

The system can resolve objects 1 million to 10 million times fainter than the object at the center of the image, which is usually the star. With that level of sensitivity, astronomers may be able to see planets.

Now that it’s up and running, as of late June, astronomers have embarked on a three-year survey of hot young stars. The planets they will detect with this method will probably be large hot Jupiters, and so unlikely to contain life — but their moons potentially could. In any event, it’s likely to be yet another major player in the planet-hunting business.

NASA Telescope Confirms Alien Planet in Habitable Zone

By Mike Wall, SPACE.com Senior Writer

MOUNTAIN VIEW, Calif. — NASA’s planet-hunting Kepler spacecraft has confirmed the discovery of its first alien world in its host star’s habitable zone — that just-right range of distances that could allow liquid water to exist — and found more than 1,000 new explanet candidates, researchers announced today (Dec. 5).

The new finds bring the Kepler space telescope’s total haul to 2,326 potential planets in its first 16 months of operation.These discoveries, if confirmed, would quadruple the current tally of worlds known to exist beyond our solar system, which recently topped 700.

The potentially habitable alien world, a first for Kepler, orbits a star very much like our own sun. The discovery brings scientists one step closer to finding a planet like our own — one which could conceivably harbor life, scientists said.

“We’re getting closer and closer to discovering the so-called ‘Goldilocks planet,'” Pete Worden, director of NASA’s Ames Research Center in Moffett Field, Calif., said during a press conference today. The newfound planet in the habitable zone is called Kepler-22b. It is located about 600 light-years away, orbiting a sun-like star.

Kepler-22b’s radius is 2.4 times that of Earth, and the two planets have roughly similar temperatures. If the greenhouse effect operates there similarly to how it does on Earth, the average surface temperature on Kepler-22b would be 72 degrees Fahrenheit (22 degrees Celsius).

Hunting down alien planets
The $600 million Kepler observatory launched in March 2009 to hunt for Earth-size alien planets in the habitable zone of their parent stars, where liquid water, and perhaps even life, might be able to exist.

Kepler detects alien planets using what’s called the “transit method.” It searches for tiny, telltale dips in a star’s brightness caused when a planet transits — or crosses in front of — the star from Earth’s perspective, blocking a fraction of the star’s light.

The finds graduate from “candidates” to full-fledged planets after follow-up observations confirm that they’re not false alarms. This process, which is usually done with large, ground-based telescopes, can take about a year.

The Kepler team released data from its first 13 months of operation back in February, announcing that the instrument had detected 1,235 planet candidates, including 54 in the habitable zone and 68 that are roughly Earth-size.

Of the total 2,326 candidate planets that Kepler has found to date, 207 are approximately Earth-size. More of them, 680, are a bit larger than our planet, falling into the “super-Earth” category. The total number of candidate planets in the habitable zones of their stars is now 48.

To date, just over two dozen of these potential exoplanets have been confirmed, but Kepler scientists have estimated that at least 80 percent of the instrument’s discoveries should end up being the real deal.

More discoveries to come
The newfound 1,094 planet candidates are the fruit of Kepler’s labors during its first 16 months of science work, from May 2009 to September 2010. And they won’t be the last of the prolific instrument’s discoveries.

“This is a major milestone on the road to finding Earth’s twin,” Douglas Hudgins, Kepler program scientist at NASA headquarters in Washington, D.C., said in a statement.

Mission scientists still need to analyze data from the last two years and on into the future. Kepler will be making observations for a while yet to come; its nominal mission is set to end in November 2012, but the Kepler team is preparing a proposal to extend the instrument’s operations for another year or more.

Kepler’s finds should only get more exciting as time goes on, researchers say.

“We’re pushing down to smaller planets and longer orbital periods,” said Natalie Batalha, Kepler deputy science team lead at Ames.

To flag a potential planet, the instrument generally needs to witness three transits. Planets that make three transits in just a few months must be pretty close to their parent stars; as a result, many of the alien worlds Kepler spotted early on have been blisteringly hot places that aren’t great candidates for harboring life as we know it.

Given more time, however, a wealth of more distantly orbiting — and perhaps more Earth-like — exoplanets should open up to Kepler. If intelligent aliens were studying our solar system with their own version of Kepler, after all, it would take them three years to detect our home planet.

“We are getting very close,” Batalha said. “We are homing in on the truly Earth-size, habitable planets.”

You can follow SPACE.com senior writer Mike Wall on Twitter: @michaeldwall. Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcomand on Facebook.