The APACHE Project
APACHE stands for “A Pathway towards the Characterization of Habitable Earths”. This means that the major goal of the so-called APACHE Project is to discover and possibly describe the main features of Earth-like planets orbiting other stars. Earth-like, in this context, doesn’t necessarily mean “very similar” to the Earth. It rather means planets “not too far” from the Earth for mass and size – Super-Earths, for instance – and hopefully located in the Habitable Zone. More generally, the APACHE Project is aimed at discovering exoplanets around closeby stars, with the transit method. Among all stellar kinds, APACHE focuses at M dwarfs. These stars are ubiquitous in the Galaxy but they are very faint, so our knowledge about them and the possible planets they host grew up significantly only in recent times.
The inspiration to establish the APACHE Project was drawn from MEarth, a project developed in the US that has already discovered the super-Earth GJ 1214b (Charbonneau et al. 2009, Nature, 462, 891). APACHE aims at being a sort of Europe-based counterpart of MEarth, although the two pojects differ from one another in several respects. In fact, APACHE targets at bright, early-type M dwarfs (about MEarth see Nutzman & Charbonneau 2008).
APACHE’s kick off is planned for December 2011. By that time, a long-term automated photometric survey of thousands of dwarf M-stars in the solar neighbourhood will start. First of all, it is necessary to decide which stars to observe. M dwarfs, we said. But which ones? An Input Catalogue of a few thousand M dwarf stars is being developed these days. Which are good criteria in building such a catalogue? A proper height above the horizon, for example. Moreover, special care must be taken about faint or active stars, or fast rotators. They are difficult targets for spectroscopic observations, in the case that radial velocities were needed. No constraints were put forth about metallicity. Actually, several studies point out that metallicity strongly correlates with planets occurrence, but to date this has been well verified for GFK dwarfs. For M dwarfs, the evidence is not that compelling. Rather, APACHE aims at casting light upon this issue considering both high and low metallicity stars.
Although the major aim is to discover planets, this survey will allegedly supply a huge amount of data about M dwarfs themselves. This will help to cast light upon major observational features of these stars, such as variability, rotation, or metallicity itself.
APACHE is located at the Astronomical Observatory of the Autonomous Region Aosta Valley (OAVdA), in northwestern Italy,in the Alpine region, quite close to France and Switzerland. Its location at 1630 m above sea level, well sheltered from the light pollution of the Padan Plain, makes the OAVdA a valuable site for astronomical observations. APACHE is a joint project between OAVdA and INAF-OATo (Turin Astronomical Observatory, affiliated to the Italian National Institute of Astrophysics).
The OAVdA is home to other astronomical researches, namely the study and characterization of bodies of the Asteroid Belt, the study of the solar corona and the photometry of Blazars (the latter is currently in stand-by). These topics contribute to the high research standards OAVdA has attained in time.
OAVdA also promotes a wide-ranging activity of didactics and divulgation directed to school students and the public. The OAVdA astrophysicists carry on lectures, lessons, astrophysical laboratories and guided tours of the night sky thanks to the equipments the OAVdA is endowed with. In particular, a set of seven Cassegrain 25 cm telescopes is utilized to introduce people to the wonders of the night sky.
(Author: Davide Cenadelli)