Wednesday, October 5, 2011

The Perfeclty Resonant, Triple-Member System of Kepler-18

Certainly no prognostication to astronomical findings, Kepler has conceded and discovered a new member to the family of exoplanets, this one rather paradisaical in orbital resonance. The system is triplex, comprised of two Neptunian exoplanets, and one in close resemblance to earth; with thanks to a team of researchers (led by Bill Cochran of The University of Texas) where this finding will be published in the special Kepler issue of The Astrophysical Journal Supplement Series in November.

Each planet is different and the system may house more than three members than discovered, the team announces. The star, as we know it "Kepler-18," is rather in similarity to our Sun, as it is just approximately ten percent larger, and is three percent less massive. The three exoplanets have veritably epigrammatic orbits, all smaller than the orbit of Mercury, which is not at all uncommon: seldom found are exoplanets with larger orbits (with respect to the exceptions). 

According to the information released by Kepler, Kepler-18b is the closest planet, orbiting its host star in the period of approximately 3.5 days. Kepler considered it a 'super-earth,' in that it is about 6.9 times the mass of earth, and twice its size, as the other two planets are nowhere as similar.Kepler-18c orbits the star in comparatively 7.6 days, with having a mass of ~17 earths and is about 5.5 times the size of the blue planet. Kepler-18d obits Kepler-18 with sixteen earth-masses, is seven times earth's size and orbits in 14.9 days. Kepler graciously provides orbital maps and animations for us to enjoy: 16b, 16c, (I can't find 16d). But, the thing to consider is the resonance.

Orbital resonance is perhaps one of the most 'perfect' things about the way objects orbit around another. As most basically defined, orbital resonance (as referred to in celestial mechanics) is the phenomenon where two orbiting bodies 'exert a regular, periodic gravitational influence on each other,' causing their orbits to be analogous by a ratio of different numbers. One of the most common resoniatic* are the resonances of a few of Jupiter's moons, Ganymede, Europa and Io: 1:2:4. Explained: every time Ganymede makes one orbit, Europa makes two, and Io makes three. Simplicity!

In this exoplanetary system, Kepler-18c makes two orbits for every one made by Kepler-18c (therefore the ratio is 1:2). During transits, however, they are not in resonance, for they "are not staying exactly on that orbital period," Cochran says. "One is slightly early when the other one is slightly late, [then] both are on time at the same time, and then vice-versa." When they are not viewed in transit, though, "it means they're interacting with each other," Cochran explains. "When they are close to each other ... they exchange energy, pull and tug on each other." How does Kepler find planets (I don't trust Wikipedia but this is written well)?

In order to find such a rare, and nonetheless special(!) exoplanetary system, Cochran and his team had to do much; using the Polamar 5-meter Hale Telescope, they took a very high-resolution speculation at the orbitary* triplet to note its characteristics. "We successively went through every possible type of object that could be there," Cochran says. "There are limits on the sort of objects that can be there at different distances from the star."

As astronomers gaze into more telescopes, more exoplanet have been found, are being found, and will be found than they could have ever dreamed of in the past years or so. Kepler-18b, c, and d are just an introduction to what is to come

To learn more: Major Source (not the only source, per contra) McDonald Observatory, University of Texas at Austin (2011, October 5). "Kepler spacecraft discovers new multi-planet solar system." ScienceDaily. Retrieved October 5, 2011, from­ /releases/2011/10/111004132817.htm &
*adj. forms of common nouns, etc.--please note that I made this word up to fit where it supposed to!

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