PLATO, or the PLanetary Transits and Oscillations of stars mission, will search a million stars, looking for Earth-like planets. 

The satellite holds 34 telescopes and cameras, each just five inches in diameter. Images collected by the tools can be combined in any manner, giving astronomers a chance to observe both bright and dim objects. PLATO contains the largest camera sensor network ever flown in space. The 136 charge-coupled devices (CCD's) have a combined surface area of nearly 10 square feet. 

The space observatory is designed and managed by the European Space Agency. A Soyuz rocket is due to lift the telescope network to space in 2024. Mission life is estimated at six years. 

By looking for small, periodic drops in brightness of stars, this network of telescopes could indicate an Earth-like planet passing between its home star and the Earth. 

Such planets could harbor life if they exist within the habitable zone surrounding their star. This is the range of distances at which liquid water would be likely to exist on these rocky worlds. Such study  could add insight into what astronomers know about our own planetary family. 

"PLATO, with its unique ability to hunt for Sun-Earth analogue systems, will build on the expertise accumulated with a number of European missions... Its discoveries will help to place our own Solar System's architecture in the context of other planetary systems," Alvaro Giménez, ESA's Director of Science and Robotic Exploration, said.

Even small worlds create measurable seismic activity on the surface of stars, and PLATO will be able to measure this effect. By combining this data with the radial velocity of the objects, the spacecraft can measure the size and mass of a planet. From there, it is easy to calculate the density, which can provide insight into the composition of the planet. Astroseismology also offers researchers a chance to measure the age of the star. 
Finding new planets is no longer a rare event. But, this mission offers astronomers an opportunity they have not had before now.  

"In the last 20 years more than one thousand exoplanets have been discovered, with quite a few multi-planetary systems among them. But almost all of these systems differ significantly from our Solar System in their properties, because they are the easiest-to-find examples. PLATO firmly will establish whether systems like our own Solar System, and planets like our own Earth are common in the galaxy," Heike Rauer, from the German aerospace center DLR. said

PLATO is one of three medium-class science missions to be selected by the ESA as part of their Cosmic Vision 2015-25 Programme.

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