A team of astronomers from Germany, Bulgaria, and Poland has used a brand-new technique called “Transit Timing Variation” (TTV) to discover an exoplanet with 15 times the mass of Earth in the WASP-3 system, located in the constellation Lyra, 700 light-years from the Sun.
This technique was proposed several years ago, and its core involves observing the transits of exoplanets. During a transit, a planet moves in front of its host star, temporarily blocking a portion of the star’s light. By detecting many such exoplanets, the Kepler and CoRoT space telescopes are also using this method to search for Earth-like planets.
If a large exoplanet has already been discovered, the gravitational pull of other potentially existing smaller planets will act upon it, causing deviations in its regular transit period. The “Transit Timing Variation” technique works by comparing the differences between theoretical calculations and actual observations to infer the existence of other members in the planetary system.
To this end, the team used two telescopes with apertures of 90 cm and 60 cm to study the transit process of WASP-3b, which has a mass 630 times that of Earth. Based on the detected variations in the transit timing of WASP-3b, they inferred that there is another planet in this system with a mass 15 times that of Earth (equivalent to the mass of Uranus), with an orbital period of 3.75 days. It has been named WASP-3c.
This is the first exoplanet discovered using the Transit Timing Variation method. Its effectiveness for low-mass planets makes it promising for discovering Earth-mass exoplanets. In some cases, an Earth-mass planet can cause the transit timing of a giant planet to vary by up to one minute.
About WASP-3c:
http://exoplanet.eu/planet.php?p1=WASP-3&p2=c
http://www.centauri-dreams.org/?p=13303
(Source: Amateur Astronomer, Issue 2010.08, Executive Editor: Li Jian)