Free Astronomy Magazine September-October 2020

25 SEPTEMBER-OCTOBER 2020 this system during their search for young, giant planets around stars like our Sun but far younger. The star TYC 8998-760-1 is just 17 million years old and located in the Southern constellation of Musca (The Fly). Bohn describes it as a “very young version of our own Sun.” These images were pos- sible thanks to the high performance of the SPHERE instrument on ESO’s VLT in the Chilean Atacama desert. SPHERE blocks the bright light from the star using a de- vice called coronagraph, allowing the much fainter planets to be seen. While older plan- ets, such as those in our Solar Sys- tem, are too cool to be found with this technique, young planets are hotter, and so glow brighter in in- frared light. By taking several im- ages over the past year, as well as using older data going back to 2017, the research team have con- firmed that the two planets are part of the star’s system. Further observations of this system, including with the future ESO Ex- tremely Large Telescope (ELT), will enable astronomers to test whether these planets formed at their cur- rent location distant from the star or migrated from elsewhere. ESO’s ELT will also help probe the interaction between two young planets in the same system. Bohn concludes: “The possibility that future instruments, such as those available on the ELT, will be able to detect even lower- mass planets around this star marks an important milestone in under- standing multi-planet systems, with potential implications for the history of our own Solar System.” SPACE CHRONICLES tronomers have indi- rectly detected thou- sands of planets in our galaxy, only a tiny frac- tion of these exoplanets have been directly im- aged,” says co-author Matthew Kenworthy, As- sociate Professor at Lei- den University, adding that “direct observations are important in the search for environments that can support life.” The direct imaging of two or more exoplanets around the same star is even more rare; only two such systems have been directly observed so far, both around stars markedly different from our Sun. The new ESO’s VLT image is the first di- rect image of more than one exo- planet around a Sun-like star. ESO’s VLT was also the first telescope to di- rectly image an exoplanet, back in 2004, when it captured a speck of light around a brown dwarf, a type of ‘failed’ star. “Our team has now been able to take the first image of two gas giant companions that are orbiting a young, solar analogue,” says Maddalena Reggiani, a postdoc- toral researcher from KU Leuven, Belgium, who also participated in the study. The two planets can be seen in the new image as two bright points of light distant from their parent star. By taking different im- ages at different times, the team were able to distinguish these plan- ets from the background stars. The two gas giants orbit their host star at distances of 160 and about 320 times the Earth-Sun distance. This places these planets much fur- ther away from their star than Jupiter or Saturn, also two gas gi- ants, are from the Sun; they lie at only 5 and 10 times the Earth-Sun distance, respectively. The team also found the two exoplanets are much heavier than the ones in our Solar System, the inner planet having 14 times Jupiter’s mass and the outer one six times. Bohn’s team imaged ! T he SPHERE instrument on ESO’s Very Large Telescope has cap- tured the first ever image of a young, Sun-like star accompa- nied by two giant exoplanets, located about 300 light-years away from Earth. This animation shows the orbits of the two exoplan- ets, compared with the size of Pluto’s orbit. Note that the yellow circle does not represent Pluto’s real orbit, but rather the size of the orbit, which is calculated based on the dwarf planet's average distance to the Sun. [ESO/L.Calçada /spaceengine.org ] P hD student Alex Bohn led the team that caught the first image of a multi-planet system around a Sun-like star. [Leiden University]