Astronomers are uncovering newfound planets in orbit around other stars at a meteoric rate these days. The tally of known planets outside the solar system now stands at more than 450, of which about 50 have been discovered just this year. That pace promises to increase as NASA's Kepler mission carries out its multiyear survey of a large patch of stars; the campaign has already located several hundred planetary candidates for follow-up study and confirmation.
At the same time that missions such as Kepler are hard at work using proved detection methods, researchers are looking to expand the exoplanetary tool kit by demonstrating new ways of locating distant worlds. One method that has been discussed for years but has yet to bear fruit is known as transit timing—if a planet passes in front of its host star so that it blocks out a small but detectable fraction of the star's light, researchers can time the arrival of that partial eclipse, known as a planetary transit. An ordinary, unperturbed orbit will bring the planet around at regular intervals, but the presence of an additional unseen planet can disrupt an exoplanet's orbit, leading to slight variations in the timing of its transit.
In a new study a team of researchers in Germany, Poland and Bulgaria has used transit timing of a known massive exoplanet to identify a hypothetical, much smaller companion. If the hypothetical planet could be confirmed—by no means a sure thing—it would be the first exoplanet to be located by variations in transit timing. The paper, which is available at the online preprint repository arXiv.org, has been accepted for publication in the Monthly Notices of the Royal Astronomical Society.
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