Kepler Spacecraft Discovers 'Invisible Planet'

[n2doc]

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 see," 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 12th-magnitude star is well placed for viewing by backyard telescopes on September evenings.


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http://www.dailygalaxy.com/my_weblog/2011/09/kepler-spacecraft-discovers-invisible-planet.html

[didact]

1. Another article....

Kepler-19b, which orbits the Sun-like star Kepler-19 650 light-years from Earth in the constellation Lyra, has been found to have an 'invisible' world tugging on it.

How do astronomers know, since it's invisible? Kepler-19b alternately runs late and early in its orbit, the first definite detection of a previously unknown planet using this method. No other technique could have found the unseen companion. Kepler-19 is a 12th-magnitude star and can be seen by backyard telescopes on September evenings.

NASA's Kepler spacecraft locates planets by looking for a star that dims slightly as a planet transits the star, passing across the star's face from our point of view. Transits give one crucial piece of information; the planet's physical size. The greater the dip in light, the larger the planet relative to its star. However, the planet and star must line up exactly for us to see a transit.

http://www.science20.com/news_articles/kepler19c_invisible_world_caught_pulling_another_planet-82433