Tuesday, September 20, 2011

CoRoT-2a: The First Exoplanet to Orbit Around Two Suns

Imagine a world with double-sunsets, double-sunrises, and maybe simultaneous dual-solar transits? Although understanding concerning the dual-solar transits is a little too advanced for now (!), CoRoT has located a world that astronomers have only dreamed of. This world, now designated CoRoT-2a, is a planet that orbits a binary star system, which is, stars which orbit each-other. In addition to this matter, it's pretty amazing to find an exoplanet orbiting two stars, which are orbiting each-other (around a hypothetical orbital point). Binary eclipses take place quite often, but yet, this action isn't at all alien.

Similar to CoRoT-2a, astronomers have located and studied intensely the star-exoplanet system of Kepler-16 (there are many animations and a continuation of facts). This is a unique system comprised of the main star (Kepler 16A) with the exoplanet (Kepler 16b) and another star (Kepler 16B) both orbiting around it, while the first star is also orbiting around that imaginary center of the system. In a paper entitled Kepler-16: A Transiting Circumbinary Planet, the authors write in the abstract: "Data from the Kepler spacecraft reveal transits of the planet across both stars, in addition to the mutual eclipses of the stars, giving precise constraints  on the absolute dimensions of all three bodies." Now, this system is quite comparably different to new CoRoT-2a, but both have many things in common.

"This discovery confirms a new class of planetary systems that could harbor life," Kepler principal investigator William Borucki said. "Given that most stars in our galaxy are part of a binary system, this means the opportunities for life are much broader than if planets form only around single stars. This milestone discovery confirms a theory that scientists have had for decades but could not prove until now."

As mentioned before, but not defined; these systems are 'circumbinary.' Astronomically translated, a circumbinary system is one that usually incorporates a binary star pair orbiting around each other with another object, usually a star but in this case an exoplanet, orbiting around those. The model above correctly interprets the definition. Astronomers know of these eclipses that are made by a simple point: they are at our vantage. Every system that we know of (usually) transit stars as viewed from earth. After you think about this fact for a while, you can just imagine the possibilities. If Kepler has located 1235 transiting objects (yet not confirmed) and has 2165 binaries that might be; do not forget that these are just the objects visible in the direction of earth. Therefore, there could be thousands, maybe millions, of other exoplanets transiting not at the vantage point to earth.

NASA describes an eclipse: "When the smaller star partially blocks the larger star, a primary eclipse occurs, and a secondary eclipse occurs when the smaller star is occulted, or completely blocked, by the larger star." During the time of research and discovery of the objects, after the first two objects had been found (on account of their dipping), astronomers noted that even later on, the brightness of this irregular system dipped...which lead to the discovery of a third body. "The additional dimming in brightness events, called the tertiary and quaternary eclipses, reappeared at irregular intervals of time, indicating the stars were in different positions in their orbit each time the third body passed. This showed the third body was circling, not just one, but both stars, in a wide circumbinary orbit." 

Read more HERE
Video (courtesy of NASA) about CoRoT-2a (I a very sorry - I tried to embed the video...blogger didn’t like it...)

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