Free Astronomy Magazine March-April 2018

10 MARCH-APRIL 2018 EXOPLANETS until complete evaporation. In short, the two CfA studies warn against easy enthu- siasm, even if, as researchers themselves point out, their conclusions do not entirely exclude the possibility that life forms may exist around TRAPPIST-1 or other red dwarfs. Shortly after the publication of these works, near the middle of August last year, the results of another study con- ducted by Adam Burgasser (University of California, San Diego) and Eric Mamajek (NASA / JPL) were published in The Astro- physical Journal . The goal was to establish the TRAPPIST-1’s age, a fundamental datum to understand the extent to which its plan- etary system can be hostile or favourable to life. To obtain a reliable estimate, the two researchers took into account some key parameters, such as the speed at which the dwarf orbits around the galactic centre (a speed that increases with age), its atmo- spheric composition (also the quantity of metals increases with age), and the num- ber of harsh flares that occurred during the observation periods. All of the parameters considered indicate that the age of TRAP- PIST-1 is significantly higher than that of the Sun and is likely between 5.4 and 9.8 billion years old. Such an advanced age af- fects both negatively and positively the possible habitability of those worlds. On the negative side, in such a long period of A rtist’s im- pression of the TRAPPIST-1 system, showcas- ing all seven planets in various phases. When a planet transits across the disk of the red dwarf host star, as two of the planets here are shown to do, it creates a dip in the star’s light that can be detected from Earth. [NASA]