Free Astronomy Magazine July-August 2020

39 JULY-AUGUST 2020 in 2019 and early 2020, Boccaletti and a team of astronomers from France, Taiwan, the US and Belgium set out to capture a clearer picture by turning the SPHERE instrument on ESO’s VLT in Chile toward the star. The SPHERE images are the deepest images of the AB Aurigae system obtained to date. With SPHERE's powerful imaging system, astronomers could see the fainter light from small dust grains and emissions coming from the inner disc. They confirmed the pres- ence of the spiral arms first detected by ALMA and also spotted another remarkable feature, a ‘twist’, that points to the presence of ongoing planet formation in the disc. “The twist is expected from some theoret- ical models of planet formation,” says co-author Anne Dutrey, also at LAB. “It corresponds to the connec- tion of two spirals — one winding inwards of the planet’s orbit, the other expanding outwards — which join at the planet location. They allow gas and dust from the disc to accrete onto the forming planet and make it grow.” ESO is constructing the 39-metre Ex- tremely Large Telescope, which will draw on the cut- ting-edge work of ALMA and SPHERE to study extrasolar worlds. As Boc- caletti explains, this powerful telescope will allow as- tronomers to get even more detailed views of planets in the making. “We should be able to see directly and more precisely how the dynamics of the gas contributes to the formation of planets,” he con- cludes. T his image shows the disc around the young AB Aurigae star, where ESO’s Very Large Telescope (VLT) has spotted signs of planet birth. Close to the centre of the image, in the inner region of the disc, we see the ‘twist’ (in very bright yellow) that scientists believe marks the spot where a planet is forming. This twist lies at about the same distance from the AB Aurigae star as Neptune from the Sun. The image was obtained with the VLT’s SPHERE instrument in po- larised light. [ESO/Boccaletti et al.] SPACE CHRONICLES T his video starts by showing a wide-field view of a re- gion of the sky in the constellation of Auriga. It then zooms in to show AB Auriga, a young star system where ESO’s Very Large Telescope has spotted signs of planet birth. [ESO/Boccaletti et al./L. Calçada, Digitized Sky Survey 2, N. Risinger (skysurvey.org ). Music: Konstantino Polizois] wake of a boat on a lake,” explains Emmanuel Di Folco of the Astro- physics Laboratory of Bordeaux (LAB), France, who also participated in the study. As the planet rotates around the central star, this wave gets shaped into a spiral arm. The very bright yellow ‘twist’ region close to the centre of the new AB Aurigae image, which lies at about the same distance from the star as Neptune from the Sun, is one of these disturbance sites where the team believe a planet is being made. Observations of the AB Aurigae system made a few years ago with the Atacama Large Millimeter/sub- millimeter Array (ALMA), in which ESO is a partner, provided the first hints of ongoing planet formation around the star. In the ALMA im- ages, scientists spotted two spiral arms of gas close to the star, lying within the disc’s inner region. Then, !