Breathe the new worlds

How planetary systems form and evolve? These questions will be answered by ARIEL, if it is selected from a shortlist of three candidates, which the ESA space mission will send into orbit in about ten years.
How planetary systems form and evolve? To receive the answers to these fundamental questions, Italy will give the mission ARIEL, which will investigate the properties of hundreds of planets orbiting stars other than the sun. ARIEL, short for Atmospheric Remote Sensing Infrared Exoplanet Large-survey, is one of the three missions selected last month by European Space Agency as part of the scientific program Cosmic Vision and who will contest the chance to be the fourth mission of the middle class (M) to be launched in ten years. ARIEL program was developed by a consortium of more than 50 institutions from 12 European countries: the UK, Italy, France, Germany, Netherlands, Poland, Spain, Belgium, Austria, Denmark, Ireland and Portugal. The mission was presented on July 16th, at the conference Pathways 2015 being held in Bern, Switzerland, by Giovanna Tinetti, Principal Investigator of ARIEL.


Credit: ESA

“The ultimate nature of extrasolar planets has yet enigmatic aspects: although we found almost 2,000 exoplanets we have not yet found a certain rule that ties the presence, size or orbital parameters of a planet to the properties of its parent star,” says Giusi Micela (INAF Palermo Astronomical -Osservatorio), co-PI of the Italian mission and science team member of ARIEL. “If we want to answer questions about how it is linked to the chemistry of a planet to the environment in which it is made or how its birth and evolution are influenced by the parent star, we need to study a large statistical sample of extrasolar planets. This is precisely for what ARIEL is designed. ”
During the three and a half years of life expectancy of the mission, ARIEL will observe more than 500 extrasolar planets, by reviewing a variety of planetary environments ranging from those of the class ‘hot Jupiter’ to super-Earths. Although some of the observed planets may be habitable, the main objective of the mission will be addressed to the exotic, hot, giants orbiting very close around their star, or stars brighter than our sun.
Hot exoplanets are a natural laboratory of which we want to study the chemistry and the formation of extrasolar planets. In colder planets, gases of a different nature are separated by condensation and are concentrated in distinct cloud layers. Extreme temperatures that occur on hot exoplanets cancel these processes so that the molecular species can circulate all over the red-hot atmosphere of these heavenly bodies.
“An atmosphere well mixed means that it is much easier to observe the chemical composition of the planet. Insight into the chemistry of a planet will allow us to understand how they formed and evolved during the first million years of his life”, explains Diego Turrini (INAF-IAPS), a member of the Science Team’s mission and responsible for studies related to planetary formation.
ARIEL has a main mirror of a meter in diameter to collect the infrared light coming from distant star systems and focus it in a spectrometer. This device scatters radiation in a “rainbow” from which you can extract information about the chemical constituents of the gas present in the atmospheres of the planets during their transit in front of or behind the parent star.
ARIEL will be put into orbit at Lagrange point 2 (L2), a point of gravitational balance beyond the Earth’s orbit, where the spacecraft is sheltered from the sun and has a clear view of the sky. This will allow us to observe and study the most of the extrasolar planets already discovered by other missions.
ARIEL is one of three scientific projects survived the penultimate stage for the selection of ESA space mission that will send into orbit in about ten years.

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