Free Astronomy Magazine January-February 2019

18 JANUARY-FEBRUARY 2019 SPACE CHRONICLES dant — comprising about 15% of the stars in the nearby universe. SPECULOOS is designed to explore 1000 such stars, including the near- est, brightest, and smallest, in search of Earth-sized habitable planets. “SPECULOOS gives us an unprece- dented ability to detect terrestrial planets eclipsing some of our small- est and coolest neighbouring stars,” elaborated Michaël Gillon of the University of Liège, principal investi- gator of the SPECULOOS project. “This is a unique opportunity to un- cover the details of these nearby worlds.” SPECULOOS will search for exoplan- ets using the transit method, follow- ing the example of its prototype TRAPPIST-South telescope at ESO’s La Silla Observatory. That telescope has been operational since 2011 and detected the famous TRAPPIST-1 planetary system. As a planet passes in front of its star it blocks some of the star’s light — essentially causing a small partial eclipse — resulting in a subtle but detectable dimming of the star. Exoplanets with smaller host stars block more of their star’s light during a transit, making these periodic eclipses much easier to de- tect than those associated with larger stars. Thus far, only a small fraction of the exoplanets detected by this method have been Earth- sized or smaller. However, the small size of the SPECULOOS target stars combined with the high sensitivity of its telescopes allows detection of Earth-sized transiting planets lo- cated in the habitable zone. These First light for SPECULOOS by ESO T he SPECULOOS Southern Ob- servatory (SSO) has been successfully installed at the Paranal Observatory and has ob- tained its first engineering and cali- bration images — a process known as first light. After finishing this commissioning phase, this new array of planet-hunting telescopes will begin scientific operations, starting in earnest in January 2019. SSO is the core facility of a new exo- planet-hunting project called Search for habitable Planets EClipsing ULtra-cOOl Stars (SPECULOOS), and consists of four telescopes equipped with 1-metre primary mirrors. The telescopes — named Io, Europa, Ganymede and Callisto after the four Galilean moons of Jupiter — will enjoy pristine observing condi- tions at the Paranal site, which is also home to ESO’s flagship Very Large Telescope (VLT). Paranal pro- vides a near-perfect site for astron- omy, with dark skies and a stable, arid climate. These telescopes have a momentous task — SPECULOOS aims to search for potentially habit- able Earth-sized planets surrounding ultra-cool stars or brown dwarfs, whose planetary populations are still mostly unexplored. Only a few exoplanets have been found orbit- ing such stars, and even fewer lie within their parent star’s habitable zone. Even though these dim stars are hard to observe, they are abun- planets will be ideally suited for fol- low-up observations with large ground- or space-based facilities. “The telescopes are kitted out with cameras that are highly sensitive in the near-infrared,” explained Laeti- tia Delrez of the Cavendish Labora- tory, Cambridge, a co-investigator in the SPECULOOS team. “This radia- tion is a little beyond what human eyes can detect, and is the primary T he telescopes of the SPECULOOS Southern Ob- servatory gaze out into the stunning night sky over the Atacama Desert, Chile. [ESO/ P. Horálek]