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Astronomers map the shadows cast on a protoplanetary disk by a close binary system

November 27, 2018

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V4046 Sgr is a young 20 Myr old binary star. It also hosts a protoplanetary disk. Using the instrument SPHERE, a planet finder mounted at the Very Large Telescope (Chile), a team leaded by Valentina D’Orazi (OAPD/INAF), which includes Alice Zurlo (UDP), discovered that the secondary star is casting a shadow on the protoplanetary disk.

Shadows found in the circumvolution disc of the V4046 Sgr system (20 million years old). This intriguing phenomenon is related to the eclipse of the central binary system: when the primary star partially eclipses the secondary stars, the flow that illuminates the disk surface is significantly reduced. Credits: V. D'Orazi / Sphere / Inaf — Shadows found in the circumvolution disc of the V4046 Sgr system (20 million years old). This intriguing phenomenon is related to the eclipse of the central binary system: when the primary star partially eclipses the secondary stars, the flow that illuminates the disk surface is significantly reduced. Credits: V. D’Orazi / Sphere / Inaf

Using the phase difference due to light travel time they managed to measure the flaring of the disk and the geometrical distance of the system. The distance is in very good agreement with the value obtained from the Gaia mission’s Data Release 2 (DR2), and flaring angles of α = (6.2 ± 0.6)° and α = (8.5 ± 1.0)° for the inner and outer disk rings, respectively. This technique opens up a path to explore other binary systems, providing an independent estimate of distance and the flaring angle, a crucial parameter for disk modelling.