Yale astronomers have discovered a low-mass, low-density exoplanet orbiting a distant star whose orbit boasts some fascinating and extreme characteristics. The yearly period of the exoplanet, known as PH3c, varies enormously from one orbit to another, and so eclectic are these orbits that it was undetectable by conventional exoplanet hunting techniques that rely on a periodic dip in the light of the parent star.
The exoplanet was discovered by the Planet Hunter program, an initiative that allows more than 300,000 citizen scientists to review data from the Keplar space telescope to scan for patterns that would otherwise be overlooked by computer algorithms. The program is co-ordinated by Yale and the University of Oxford and to date has discovered over 60 exoplanets since its inception in 2010.
"It harnesses the human dimension of science," states Debra Fischer, head of the exoplanets group at Yale and co-author of the paper. "Computers can’t find the unexpected, but people can, when they eyeball the data."
The project's most recent discovery sits 2,300 light years from Earth and owes its unusual orbit to an extreme version of a gravitational quirk that is at work in every solar system, including our own. All planets are affected by the gravitational pull of their immediate celestial neighbors. For our planet the effects are very slight, with bodies such as Mars and Jupiter distorting Earth's orbital period by roughly a second each orbit. However, the gravitational influence of PHC3's neighbors is far more significant, altering the exoplanet's orbital period by roughly 10.5 hours over the course of only 10 orbits.
The discovery of PHC3 also allowed the group to better characterize the celestial bodies on either side of the elusive orb. It was discovered that the outer planet had a mass greater than that of Saturn, while the innermost of the trio had a rocky composition similar to Earth's. Interestingly, the length of the inner planet's year is 1.91 times shorter than that of PHC3's, whilst the length of the outer planet's year was 1.91 times longer.
Joseph Schmitt, Yale grad student and lead author on the paper concludes, "We’re not sure if this is just a coincidence or whether this might tell us something about how the planets were formed."
A paper detailing the team's findings is available in The Astrophysical Journal.
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