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article imageESA's new Plato planet hunter will examine a million star systems

By Robert Myles     Feb 20, 2014 in Science
Warwick - The European Space Agency announced Wednesday that a new space-based observatory to search for planets orbiting alien stars will form the third plank of the ESA’s medium-class (M-class) science missions.
Known as the PLATO mission, PLATO standing for “Planetary Transits and Oscillations of stars,” it was selected by the ESA’s Science Program Committee and will form part of the agency’s Cosmic Vision 2015-25 Program.
Launch of PLATO, aboard a Soyuz rocket from Europe’s Spaceport in Kourou, Guiana, is scheduled to take place no later than 2024. Following its launch, PLATO will embark on a six-year mission once it takes up its permanent observational position at the L2 Lagrange point in space, a virtual point in space in space 1.5 million kilometers beyond Earth as seen from the Sun.
PLATO won’t be the first spacecraft to take advantage of L2 Lagrange positioning. L2 is the current home of the ESA Planck Space Telescope and the future home of NASA’s James Webb Space Telescope.
L2 is perfect for astronomical observation as a spacecraft positioned there is close enough to communicate easily with Earth and can keep the Sun (for solar power) as well as the Earth and moon behind the spacecraft. From L2, any observatory thus has a clear view of deep space.
PLATO’s two key mission objectives are to determine the conditions necessary for planet formation and the emergence of life and how the solar system works.
While the number of exoplanets — planets in other solar systems — discovered has mushroomed in recent years, detailed information on such planets’ composition has been lacking. To date, not a single Earth-like exoplanet in a habitable zone around a star similar to our Sun has been found and characterized. PLATO will be a pioneer in finding new worlds for humanity to explore.
Don Pollacco, from the University of Warwick, UK, who leads the PLATO Science consortium commented, “This is fantastic news for Europe, PLATO will allow the first systematic survey of nearby planets for indications from advanced life forms (as well as slime). A few years ago this would have been science fiction and now it’s coming to pass as science fact.”
Very few exoplanets so far discovered have had their mass, radius and age, all factors needed to properly describe a planet, determined precisely. “The observation of planets in many different states of their evolution will give us clues for the past and the future of our own planetary system,” said Dr. Heike Rauer of DLR, the German Aerospace Center, one of the collaborators on PLATO, “By no means do we know all about the youth of our Solar System.”
PLATO will concentrate its search on stars in relatively close proximity to our solar system. Focusing on such stars, it’ll search for tiny, almost imperceptible, but regular dips in brightness as alien planets transit in front of alien stars, in so doing, temporarily obstructing a small fraction of the starlight.
Using 34 separate small telescopes and cameras, PLATO will search for planets around up to a million stars spread over half of the sky.
As well as observing such planetary transits, PLATO will also investigate seismic activity in the stars. The aim is to build up a precise characterization of the host sun of each planet discovered, including its mass, radius and age.
Such space-based observations will be coupled with ground-based radial velocity observations, allowing a planet’s mass and radius to be calculated. From that, the density of such exoplanets can be calculated which gives an indication of the planet’s composition. The extremes are small rocky worlds, similar to Earth or Mars, or gas giants, like Jupiter or Neptune.
But within that range there are oddities, which, for all we know, may be the norm. Equally, there may be no “typical” solar system. Either way, PLATO will shed light on these distant planetary systems.
Measuring both the radius and the mass of a planet allows astronomers to distinguish between a “mini-Neptune” with a high gas content, but low density, and a rocky planet with an iron core like Earth. Without that information the habitability of a planet can’t be ascertained. Some exoplanets already found are classed as “super-Earths,” with sizes and masses considerably larger than Earth’s. Life, if it exists on such worlds, is likely to be very different to that on Earth since gravitational forces would be much greater as a consequence of the planet’s size.
PLATO will identify and study thousands of exoplanetary systems but will concentrate on discovering and characterizing Earth-size planets and super-Earths in the habitable zone of their parent star — the so-called “Goldilocks zone,” neither too hot nor too cold — the distance from the star where liquid surface water could exist.
The newly announced mission is a logical progression for the ESA, building on the agency’s Corot mission that carried out a three-year search for exoplanets. PLATO will also complement the ESA’s CHEOPS — CHaracterizing ExOPlanet Satellite — mission due to launch in 2017.
Data from the ESA’s recently launched Gaia, billion star surveyor, mission will help point PLATO toward thousands of exoplanet systems so that their precise characteristics can be logged.
The PLATO mission becomes the third medium mission in prospect. In 2011, ESA selected Solar Orbiter and Euclid as its first M-class projects. Solar Orbiter will launch in 2017 and will get up close to our Sun, studying it and the solar wind from a distance of less than 5 million kilometers. Euclid, slated for launch in 2020, will also involve NASA. It will concentrate on dark energy, dark matter and the structure of the universe.
More about Esa, European space agency, Plato, Exoplanets, alien planets
 
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