See CfA Release 2011-24 Thursday, Sept. 8, 2011.
Excerpt: Cambridge, MA. Usually, running five minutes late is a bad thing since you might lose your dinner reservation or miss out on tickets to the latest show. But when a planet runs five minutes late, astronomers get excited because it suggests that another world is nearby.
NASA’s Kepler spacecraft has spotted a planet that alternately runs late and early in its orbit because a second, “invisible” world is tugging on it. This is the first definite detection of a previously unknown planet using this method. No other technique could have found the unseen companion.
“This invisible planet makes itself known by its influence on the planet we can detect,” said astronomer Sarah Ballard of the Harvard-Smithsonian Center for Astrophysics (CfA). Ballard is lead author on the study, which has been accepted for publication in The Astrophysical Journal.
“It’s like having someone play a prank on you by ringing your doorbell and running away. You know someone was there, even if you don’t see them when you get outside,” she added.
Both the seen and unseen worlds orbit the Sun-like star Kepler-19, which is located 650 light-years from Earth in the constellation Lyra. ...
The first planet, Kepler-19b, transits its star every 9 days and 7 hours. It orbits the star at a distance of 8.4 million miles, where it is heated to a temperature of about 900 degrees Fahrenheit. Kepler-19b has a diameter of 18,000 miles, making it slightly more than twice the size of Earth….
If Kepler-19b were alone, each transit would follow the next like clockwork. Instead, the transits come up to five minutes early or five minutes late. Such transit timing variations show that another world’s gravity is pulling on Kepler-19b, alternately speeding it up or slowing it down. … the planet Neptune was discovered similarly.…
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