Published in A&A the paper describing the catalog of the candidate targets for the PLATO mission: “The all-sky PLATO input catalogue” of M. Montalto (Unipd/INAF-OAPd)

According to the data released by NASA, to date (2021 October 1st) we have confirmed 4525 exoplanets in 3357 planetary systems. The vast majority of these planets (75%) were discovered with the methods of transits, while about 20% with that of radial velocity. With the former technique, planets are discovered when they transit in front of their stars along our line of sight. During these transits, the planet partially obscures the star, inducing a very small dimming of stellar luminosity. By analysing transits and their shapes, it is also possible to derive the size of the planet compared with that of the star and to obtain information on its orbit. With the radial velocity technique, instead, planets are discovered by observing periodic oscillations of the stars with respect to their rest positions due to the mutual planet-star gravitational attraction. With this technique is also possible to estimate the mass ratio between star and planet. However, both techniques are sensitive to large planets in close orbits around low-mass stars. For this reason, to date only 166 terrestrial planets were discovered.

 

The search of Earth-like exoplanets is one of the main challenge for modern astronomy. To be considered really similar to Earth, these planets must also orbit around their stars at the right distance to host liquid water on their surfaces (e.g. they must lie in the “habitability zone” of the stars). This search will be the main scientific objective of the satellite Plato, the third medium-class mission included in the Cosmic Vision of the European Space Agency (ESA), which will be launched in 2026. Plato will be equipped with 26 telescopes with an aperture of 20 cm, each capable of observing a field of 40 degrees in diameter (just as a comparison, the diameter of the full Moon is about half a degree), monitoring a large number of stars in the Solar neighbourhood in order to search terrestrial planets with the transit technique.

 

This whole battery of telescopes will allow Plato to have a huge field of view of about 2100 square degrees. The observations will thus be too large to be continuously downloaded on Earth. For this reason, Plato targets will be selected before the observations. The catalog of sources that may be observed by Plato (the all-sky PLATO input catalogueasPIC1.1) has been compiled by a team of astronomers led by M. Montalto (Physics Department “Galileo Galilei”, University of Padua, and INAF – Astronomical Observatory of Padua), and described in the paper: “The all-sky PLATO input catalogue“, recently appeared on Astronomy and Astrophysics. The catalog contains 2378177 FGK stars and 297362 M stars, with an average distance of 1400 light years for the FGK stars and 482 light years for the M stars. The catalog includes data retrieved from the Second Data Release of Gaia observations (positions, parallaxes, proper motions, photometry), together with other photometric data and stellar parameters (mass, temperature, radius, and extinction) derived from photometry. From this catalog will be selected both the targets and the fields that will be observed by Plato. Among the coauthors, the astronomers L. Prisinzano and S. Benatti (INAF – Astronomical Observatory of Palermo), which are strongly involved in Plato.

 

The figure (click here to visualize the entire image) shows the distribution of the stars in the asPIC1.1 catalog in galactic coordinates (which means that the Galactic plane is at the center of the image horizontally), with marked the possible fields selected to date for deep Plato observations.

 

Mario Giuseppe Guarcello  ( follow mguarce) ( youtube)

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