Free Astronomy Magazine July-August 2016

JULY-AUGUST 2016 PLANETOLOGY particularly near to Earth. This category of objects is quite heterogeneous in being formed by small-sized real stars and failed stars, all sharing a surface temperature lower than 2700 K (the term ‘ultracool’ is quite relative as they are still very hot ob- jects). These dwarfs account for 15% of the star-like objects surrounding the Sun and thus form a significant population. The models interpreting the origin and evolution of ultracool dwarfs and their pro- toplanetary disks predict the existence of a considerable number of rocky planets lo- cated on orbits very close to their central ob- ject. Before now, however, researchers have never been able to discover a single one of them, since ultracool dwarfs are more easi- ly investigated in the infrared rather than in the so-called white light (the one visible to our eyes), which is within the operating range of most ground telescopes. TRAPPIST was specifically designed for observations in the near infrared, allowing to see ultra- cool dwarfs hundreds of times more bril- liant than they appear in the visible. Thanks to the outstanding performance of this small instrument, a group of researchers led by Michaël Gillon (Institut d'Astrophy- P anoramic view of some facilities at La Silla Observatory, with in the fore- ground the open dome of the TRAnsiting Plan- ets and Plane- tesImals Small Telescope. [ESO] A nice time-lapse of the transit of Mercury across the Sun, shot from Palermo, Italy, by Alessio Vaccaro and Egidio Di Bianca on 9 May 2016. As per the sequence of the event (1,320 frames), the authors used an apo- chromatic refractor, a solar filter, two unmodded Canon cameras and a GoPro.