Almost completed the selection of the fields that will be observed by PLATO. The paper: “The PLATO field selection process. I. Identification and content of the long-pointing fields” of V. Nascimbeni (INAF – OA Padova) published by A&A)
Since the discovery of the first planet orbiting another star (51 Pegasi b, discovered in 1995), it has always been one of the main objective of the exoplanetary science to discover an Earth sibling. Such a planet must have a mass similar to that of the Earth, and it must orbit around its star in the “habitability zone”, which is the range of distance from the central star at which liquid water can exist on the surface of rocky planets. Despite these conditions do not necessarily mean that the planet is habitable (for instance, Venus meets both requirements but it is definitely not habitable), the discovery of a Earth sibling may constitute a step forward the search for life in other planets.
The M-class mission of the European Space Agency PLATO (PLAnetary Transits and Oscillations of stars), whose lunch is planned on 2026, aims at finding exoplanets similar to Earth. The satellite will perform its search using the transits technique, which consists in detecting periodic dimming of the light of stars caused by the transit of theirs planets in front of them along our line of sight. To fulfill its objective, PLATO has been designed in order to observe a huge field of view (approximately a 49°×49° area) obtaining fine photometry of bright stars with a very good precision. The high photometric precision is required in order to detect the transit of small planets (it is intuitive that the smaller the planet, the smaller the area of stellar surface covered by the planet, the less intense is the dimming of stellar radiation). PLATO will achieve these requirements thanks to 24 20-cm telescopes which will observe in 4 groups of six telescopes partially overlapping field of views.
During its mission, PLATO will monitor two fields for 1-2 years. This will constitute the Long-duration Observation Phase of its mission,and thus the two fields are called “LOP fields”. Together with the two LOP fields, other fields will be observed for shorter periods, in order to observe about 40% of the whole sky by the end of its mission. The determination of the LOP fields is thus one of the crucial steps of the mission preparation phase, and the success of the mission depends in part from this. The paper: “The PLATO field selection process. I. Identification and content of the long-pointing fields” of V. Nascimbeni (INAF – Astronomical Observatory of Padua), recently appeared on Astronomy & Astrophysics, describes the selection criteria that the two fields must meet, and define a quantitative metric which is aimed at maximizing the scientific return of the mission. The authors have thus selected two LOP fields, one in the Northern and one in the Southern sky, that meet the criteria define by this metric. The two fields contain 243 planets discovered to date, and in particular the northern field partially overlaps with the field observed by Kepler, one of the NASA missions dedicated to the search of exoplanets. The two fields also contain 19 stellar clusters with an age ranging between 100 million years and 1.5 billion years, and 12 eclipsing binaries which have already been studied in details, and that will constitute a benchmark for studies of this class of sources with PLATO. The selection of the two fields has been made with the collaboration also of the astronomers S. Benatti and L. Prisinzano of INAF – Astronomical Observatory of Palermo.
The figure (click here to visualize the entire image) shows the positions in the sky of the two LOP fields in blue. The grayscale map shows the density of the stars brighter than G=13.5 mags. included in the Third Data Release of the Gaia mission. The fields observed by other missions dedicated to the search of exoplanets are also indicated: CoRoT (red), Kepler (magenta), Kepler/K2 (green) and the TESS continuous viewing zone (yellow). The red crosses mark the celestial poles.
Mario Giuseppe Guarcello ( follow mguarce) ( youtube)
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