Hubble images TW Hydrae Disc Shadows (annotated)

Comparison images from the NASA/ESA Hubble Space Telescope, taken several years apart, have uncovered two eerie shadows moving counterclockwise across a disc of gas and dust encircling the young star TW Hydrae. The discs are tilted face-on as seen from Earth and so give astronomers a bird’s-eye view of what’s happening around the star. The left image, taken in 2016, shows just one shadow [A] at the 11 o’clock position. This shadow is cast by an inner disc that is slightly inclined to the outer disc and so blocks starlight. The picture on the left shows a second shadow that emerged from yet another nested disc at the 7 o’clock position, as photographed in 2021. What was originally the inner disc is marked [B] in this later view. The shadows rotate around the star at different rates like the hand on a clock. They are evidence for two unseen planets that have pulled dust into their orbits. This makes them slightly inclined to each other. This is a visible-light photo taken with the Space Telescope Imaging Spectrograph. Artificial colour has been added to enhance details.

[Image description: This Hubble Space Telescope Image shows two side-by -side circles that are photos, taken in 2016 and 2021, of nested discs of gas and dust encircling the star TW Hydrae. The view is looking down on top of the discs. In the left image a shadow can be seen at the 11 o’clock position. A later image, on the right, shows two shadows at the 11 o’clock and 7 o’clock positions. This is evidence for two nested discs that are inclined at different angles.]