Moving shadows around a planet-forming star

This star has a spiral disk of dust around it. Processes in the inner disk – winds, or swirls or clashes of pebbles – seem to be casting shadows on the outer disk.

A team of mainly Dutch astronomers said on November 9, 2017 that it has observed moving shadows on a dust disk around a young star designated HD135344B. The star is 450 light-years away. It’s in a formation stage and shows striking spiral arms. On multiple days, the astronomers captured an image of this star and its dust disk. They used the SPHERE instrument on the Very Large Telescope in Chile, which can block the image of a central star in order to capture orbiting exoplanets or the details of dust disks like this one, with the goal of learning more about star formation. These astronomers believe that processes in the inner disk cast their shadows at the outer disk.

The astronomers published their findings November 9 in the peer-reviewed Astrophysical Journal. Their statement explained:

The discovery builds on an earlier publication in which the researchers made one image of the disk. By making multiple images, the astronomers clearly saw variations in the shadows. As a result, they could study the shadows in more detail …

The astronomers saw subtle variations of brightness in the outer dust disk. They presume this is because the gas and dust in the inner disk quickly turn around the star. The astronomers do not know yet which process causes the quick turning of the dust.

Astronomer Tomas Stolker is the first author of the paper about the shadows. He said the turning of the dust may be due to:

… winds, or swirls or clashes of pebbles.

The astronomers expect 1 or more large exoplanets – Jupiter-like worlds – to emerge from this dust disk eventually. Read more about this research from

View larger. | Dust disk around the star HD 135344B. The star itself is removed from the picture. Image via Tomas Stolker/

Bottom line: For several days, astronomers imaged the young star HD 135344B and its dust disk. They saw moving shadows on the disk, which they believe is caused by a turning of the gas and dust in the star’s inner disk. Hence we learn more about the process by which stars and planets form.

Deborah Byrd