Sunday, December 4, 2011

Exoplanetary Statistics are Challenged: Eighteen New Exoplants Discovered

Exoplanetary research has become one of the most studied field of astronomy since the first discovery of such a planet was discovered years ago (1991). More and more astronomers have been locating new candidates and more and more graduates graduate college with degrees in this field. Now, astronomers have perfected instruments and results are pouring in faster than ever: eighteen new exoplanets candidates have been confirmed, and each orbiting a planet with more mass than the sun.

Although not discovered by the Kepler Telescope, a telescope designed for the purpose of discovering planets outside our solar system, the exoplanets are the largest group to be discovered by the Keck Observatory of Hawai'i. The astronomers survey more than three-hundred stars for "wobbles," which means a planet. A "wobble" is the act of an exoplanet passing in front of (transiting), but not occulting, a star, letting astronomers on earth note that difference in light emitted by the star. These only work if the exoplanetary system is edge-on to earth. Light curves are plotted to show this "wobble," which looks like the dip below. It dips down, becasue the light from the star drops down when the planet transits it, and blocks a portion of light.

Light curve of exoplanet WASP-19b; Credit ESO

Research astronomers at the Keck Observatory have been looking at stars more massive than the sun, those of which are A stars on the HR Diagram. Our sun is a G star, and in order of high mass (O, B, A, F, G, K, M) O is the highest and M is the lowest. We can see that an A star has greater mass than a type G star. With using the wobble method for detecting planets (as explained above), astronomers have found eighteen exoplanets orbiting different stars greater than the mass of our sun.

"It's the largest single announcement of planets in orbit around stars more massive than the sun, aside from the discoveries made by the Kepler mission," says John Johnson, assistant professor of astronomy at Caltech and the first author on the team's paper, which was published in the December issue of The Astrophysical Journal Supplement Series. "It's nice to see all these converging lines of evidence pointing toward one class of formation mechanisms." There's another interesting twist, he adds: "Not only do we find Jupiter-like planets more frequently around massive stars, but we find them in wider orbits."Many exoplanets orbit very close to their stars, but now we see planets about 0.7 AU from their sun, about 65,069,121.3 miles; although rather short on astronomical scales, this is far for exoplanets. This is a significant discovery in itself!

For what reason are astronomers interested in such systems? It is actually a matter of the creation of our own, which is what they're after. If they can find different exoplanetary systems at different stages of development, then maybe they can decipher the origin of our own and how it was created. It seems like an easy process but astronomers have really not uncovered anything yet. This is why exoplanetary research has skyrocketed.

But these Jupiter-like planets have formed very close to their stars, considerably controversial in astronomers' theory of planetary development. They state that Jupiter-like planets are cool and are formed very far away from their sun; these exoplanets have disproved that!, and astronomers wish to know why. Their orbits are also circular; interestingly rare, becasue most found already have elliptical (highly elliptical) paths.

Astronomers wish to know the answers to all these puzzling questions, becasue these exoplanets that rebel against the proposed theories of planetary formation, are those which orbit around high-mass stars. John Johnson concludes with a unique metaphor: "I liken it to a garden—you plant the seeds and put a lot of work into it," he says. "Then, a decade in, your garden is big and flourishing. That's where I am right now. My garden is full of these big, bright, juicy tomatoes—these Jupiter-sized planets."

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