For the first time, scientists have definitively discovered an “invisible” alien planet by noticing how its gravity affects the orbit of a neighboring world. NASA’s Kepler space telescope detected both alien planets, which are known as Kepler-19b and Kepler-19c. Kepler spotted 19b as it passed in front of, or transited, its host star. Researchers then inferred the existence of 19c after observing that 19b’s transits periodically came a little later or earlier than expected. The gravity of 19c tugs on 19b, changing its orbit. According to scientists the discovery of Kepler-19c marks the first time this method, known as transit timing variation, or TTV. Kepler has been incredibly successful using this so-called transit method, spotting 1,235 candidate alien planets in its first four months of operation.
Kepler-19b a world 650 light-years away from Earth is in the constellation Lyra. Kepler-19b has a diameter about 2.2 times that of Earth, and orbits 8.4 million miles (13.5 million kilometers) from its parent star. The planet likely has a surface temperature around 900 degrees Fahrenheit (482 degrees Celsius). Researchers know little about Kepler-19c at the moment. It takes the alien world 160 days or less to zip around its host star, and 19c’s mass could range from a few times that of Earth to six times that of Jupiter.