Alien Planet Safari

Discussion in 'Strategic Forces' started by LETHALFORCE, Jan 18, 2010.

  1. LETHALFORCE

    LETHALFORCE Moderator Moderator

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    Alien Planet Safari

    Alien Planet Safari

    The premiere observatory of the next decade, the James Webb Space Telescope, will launch in 2014 in search of "big game"--namely, the first stars and galaxies ever formed in our Universe. But the "little game" could turn out to be just as interesting. There's a dawning awareness among astronomers that the world's largest infrared telescope is going to be a canny hunter of planets circling faraway stars.
    "Webb was originally conceived to search for the first galaxies and address the big cosmological questions associated with them, but we now know it can contribute powerfully to the planet hunt," says Mark Clampin of NASA's Goddard Space Flight Center.

    "Exoplanets are tremendously exciting. The field is changing literally by the day. I gave a talk on exoplanets the other day, and in the time between writing and delivering the speech, astronomers announced 30 new planets!"

    The Webb telescope is the tool for carrying out detailed, high precision follow-up studies of these new planets other telescopes are flushing out of hiding. And such planets are sneaky - hiding in the glare of their own "suns."

    "It's like trying to find a firefly's flash in the beam from a lighthouse," says Jonathan Gardner, Webb Deputy Senior Project Scientist from Goddard. "But there are ways to do it!"

    One way is called "transit science," which means studying the light from a star when a planet passes in front of the star.

    "Webb will measure the total light the star emits and then measure the amount of light when the planet crosses in front," explains Gardner. "This telescope can even detect brightness changes that occur when the planet passes behind the star. With some Doppler measurements from ground-based surveys, all this information helps us determine the planet's mass and radius, and then astronomers can start to think about the planet's composition."

    "We can also do spectroscopy during the transit," Gardner continues. "We measure the spectrum of the starlight before the transit, then again when the starlight is filtered through the planet's atmosphere during the transit."

    The starlight changes as it goes through the planet's atmosphere.

    "By comparing the two spectra for the star (in and out of transit), we can extract the planet's spectrum and learn about the planet's atmosphere," says Clampin. "We have to collect a lot of infrared light - a billion or more photons - for each spectral element to isolate features. Webb is perfect for this kind of study."

    The telescope's huge 25 m2 collecting area can round up the herd of photons needed. And because Webb will be kept extremely cold thanks to its enormous sunshade and its location at the L2 Lagrange point, no extraneous source of heat will contaminate signals from the cosmos.

    "We're thrilled at Hubble's science, but we need low thermal background to see the faint infrared things we want to see," says Clampin. "And Hubble starts to see its own thermal signature at a certain point because it's not a very cold telescope.

    "Webb will show us what the 'exoplanet zoo' looks like. This telescope will be very good at observing and taking spectra of gas giant planets, and we can take some spectral data on smaller planets, too, about Neptune-sized. Our telescope will also zoom in to study newly discovered super Earths' - planets bigger than Earth but smaller than Neptune."

    Webb can also find planets on its own. "The Webb telescope will use a technique called coronagraphy to look for gas giant planets," says Gardner.

    "A star's light is so brilliant that it outshines any nearby planet by a million to a billion to 1, but inside three of Webb's four cameras there's a black spot the light can't go through. We'll put the star behind the black spot so we can see the planet next to the star. It's like when a car is driving toward you at night with its high beams on, and you use your hand to block out that light so you can see the road."

    "Our eventual goal is to look for chemical evidence of life on some of these new planets. But we're not sure yet how well we'll be able to do that."

    "Can Webb find signs of life on a planet like Earth?" asks Clampin. "The answer is probably not. A true Earth twin would be too small to emit enough infrared light from its atmosphere for Webb to pick up."

    "Still, every time scientists make statements like that, someone proves them wrong. Transit science is changing so fast, it's hard to say exactly what wonders Webb's hunt will turn up."
     
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  3. LETHALFORCE

    LETHALFORCE Moderator Moderator

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    JWST to Engage in Exoplanetary 'Safari' - The observer will be the most complex ever built - Softpedia

    JWST to Engage in Exoplanetary 'Safari'

    The observer will be the most complex ever built By Tudor Vieru, Science Editor



    Scheduled for launch in 2015, the James Webb Space Telescope will arguably be one of the most complex pieces of technology ever sent to the Earth's orbit. Its massive antenna was constructed in such a way that it would be able to peer back into the earliest history of the Universe, and identify the first stars and galaxies that were formed after the Big Bang. Even though this line of investigations is its main objective, the team behind JWST believes that the telescope will also be able to detect a host of exoplanets, orbiting distant, far-away stars. In addition, the scientists also believe that James Webb's amazing resolution will allow them to look at the chemical composition of these exoplanets.

    “Webb was originally conceived to search for the first galaxies and address the big cosmological questions associated with them, but we now know it can contribute powerfully to the planet hunt. Exoplanets are tremendously exciting. The field is changing literally by the day. I gave a talk on exoplanets the other day, and in the time between writing and delivering the speech, astronomers announced 30 new planets!” Mark Clampin, an expert at the NASA Goddard Space Flight Center, in Greenbelt, Maryland, explains. The James Webb will observe the Cosmos in infrared wavelengths, and is destined to be the successor of the renowned Hubble Space Telescope.

    But the JWST could also work together with other observatories, such as NASA's newly launched WISE mission, or the Kepler planet-hunting telescope. These instruments, as well as others, could analyze potential exoplanets superficially, and then send their coordinates to the James Webb telescope. This type of collaboration would ensure that the maximum amount of scientific data is extracted from the space objects. The problem is that the exoplanets are hiding in the light of their parent stars. “It’s like trying to find a firefly’s flash in the beam from a lighthouse. But there are ways to do it!” GSFC Webb Deputy Senior Project Scientist Jonathan Gardner explains.

    “Webb will measure the total light the star emits and then measure the amount of light when the planet crosses in front. This telescope can even detect brightness changes that occur when the planet passes behind the star. With some Doppler measurements from ground-based surveys, all this information helps us determine the planet’s mass and radius, and then astronomers can start to think about the planet’s composition,” the scientist adds. “By comparing the two spectra for the star (in and out of transit), we can extract the planet’s spectrum and learn about the planet’s atmosphere. We have to collect a lot of infrared light – a billion or more photons – for each spectral element to isolate features. Webb is perfect for this kind of study,” Clampin concludes, quoted by Space Fellowship.
     

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