Armed with a new method for validating multiple-planet solar systems, scientists have identified a new batch of 715 previously unknown exoplanets. This raises the total of verified planets to 1,700.
The Kepler space telescope finds planets by recording how a star's brightness drops when a planet passes in front of it, as seen from Earth. This is called the transit method of planet discovery. The new discovery technique, called validation by multiplicity, involves identifying a pattern of several planets appearing in the same solar system. The planets move in circular orbits, as opposed to a group of stars, which would orbit each other chaotically. The method works because exoplanets orbit in a flat plane as do the planets of Earth’s solar system. [Gallery: A World of Kepler Planets]
The group of 715 newly discovered exoplanets orbit 305 stars. The bulk of the discoveries are planets between the size of Earth and Neptune.
Earth's solar system lies between two major spiral arms of the Milky Way. Kepler's planet search is conducted in a narrow wedge-shaped volume of space that stretches out ahead of Earth's solar system as it orbits the galaxy. Stars in the search volume are therefore at about the same distance from the center of the galaxy as we are.