Viewing Alien Exoplanets Directly

 Exoplanets  

After many years of research and development, it is now becoming possible to not only detect alien exoplanets, but to view them directly.  As the list of exoplanets grows, we are getting more and more details of these potential homes for future generations.

After decades of development, construction, and testing, new instruments for directly imaging and analyzing planets around other stars are coming online, and letting us see from distant worlds directly.

University of Arizona researchers recently snapped images of a planet outside our solar system with an Earth-based telescope using essentially the same type of imaging sensor found in digital cameras instead of an infrared detector. Although the technology still has a very long way to go, the accomplishment takes astronomers a small step closer to what will be needed to image earth-like planets around other stars.

"This is an important next step in the search for exoplanets because imaging in visible light instead of infrared is what we likely have to do if we want to detect planets that might be suitable for harboring life."

"This is an important next step in the search for exoplanets because imaging in visible light instead of infrared is what we likely have to do if we want to detect planets that might be suitable for harboring life," said Jared Males, a NASA Sagan Fellow in the UA's Department of Astronomy and Steward Observatory.

One group at NASA plans to construct a starshade, a giant structure designed to block the glare of stars so that future space telescopes can take pictures of planets.

Actually taking a picture of an exoplanet has proven an immensely difficult task. Picking out the dim light of a planet from a star billions of times brighter is akin to finding a needle in a cosmic haystack, especially when the planet in question is a small, rocky world similar to Earth. In order to achieve this feat, researchers are developing techniques to block out the starlight while preserving the light emitted by the planet. This is called starlight suppression.

NASA’s starshade engineers are optimistic that refining their technology could be the key to major exoplanet discoveries in the future. “A starshade mission would allow us to directly image Earth-size, rocky exoplanets, which is something we can’t do from the ground,” says Jeremy Kasdin, a Princeton researcher who is the Principal Investigator of the starshade project. “We’ll be able to show people a picture of a dot and explain that that’s another Earth.”

Another instrument, called the Gemini Planet Imager (GPI), was designed, built, and optimized for imaging faint planets next to bright stars and probing their atmospheres. It will also be a powerful tool for studying dusty, planet-forming disks around young stars.

It is one of the most advanced such instrument to be deployed on one of the world’s biggest telescopes – the 8-meter Gemini South telescope in Chile.

“Even these early first-light images are almost a factor of 10 better than the previous generation of instruments. In one minute, we are seeing planets that used to take us an hour to detect,” says Bruce Macintosh of the Lawrence Livermore National Laboratory who led the team that built the instrument.

GPI detects infrared (heat) radiation from young Jupiter-like planets in wide orbits around other stars, those equivalent to the giant planets in our own Solar System not long after their formation. Every planet GPI sees can be studied in detail.

“With GPI we directly image planets around stars – it’s a bit like being able to dissect the system and really dive into the planet’s atmospheric makeup and characteristics,” says Macintosh.

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GPI carried out its first observations last November – during an extremely trouble-free debut for an extraordinarily complex astronomical instrument the size of a small car. “This was one of the smoothest first-light runs Gemini has ever seen” says Stephen Goodsell, who manages the project for the observatory.

Recently the GPI was also involved in discovering the first Earth-sized exoplanet orbiting within the habitable zone of another star along with the W. M. Keck Observatory. The initial discovery, made by NASA's Kepler Space Telescope, is one of a handful of smaller planets found by Kepler and verified using large ground-based telescopes. It also confirms that Earth-sized planets do exist in the habitable zone of other stars.

“Exoplanets are extraordinarily faint and difficult to see next to a bright star,” notes GPI chief scientist Professor James R. Graham of the University of California who has worked with Macintosh on the project since its inception. GPI can see planets a million times fainter than their parent stars. Often described, ‘like trying to see a firefly circling a streetlight thousands of kilometers away,’ instruments used to image exoplanets must be designed and built to “excruciating tolerances,” points out Leslie Saddlemyer of NRC Herzberg (part of the National Research Council of Canada), who served as GPI’s systems engineer. “Each individual mirror inside GPI has to be smooth to within a few times the size of an atom,” Saddlemyer adds.

The Gemini Planet Imager’s first light image of Beta Pictoris b
Image Source - Gemini Observatory

The team is currently undertaking a large-scale survey, looking at 600 young stars to see what giant planets orbit them. GPI will also be available to the whole Gemini community for other projects, ranging from studies of planet-forming disks to outflows of dust from massive, dying stars.
Looking through Earth’s turbulent atmosphere, even with advanced adaptive optics, GPI will only be able to see Jupiter-sized planets. But similar technology is being proposed for future space telescopes.

“Some day, there will be an instrument that will look a lot like GPI on a telescope in space,” Macintosh projects. “And the images and spectra that will come out of that instrument will show a little blue dot that is another Earth.”


SOURCE  Coconut Science Lab, Gemini Observatory

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