Hubble sees a cosmic bat flapping its wings deep in the Serpens Nebula

Out in the depths of the Serpens Nebula, located 1,300 light-years away, lurks a strange creature. Here, where stars are born amid swirling dust and gas, lies a young star HBC 672, also known as the Bat Shadow. This star is famous for appearing to have shadowy wings extending out from it, and now scientists using the Hubble Space Telescope have spotted something curious: These wings appear to be flapping.

Bat Shadow (2018 Observation)
This image shows only the feature which was nicknamed the Bat Shadow. It is the shadow of a protoplanetary disc orbiting the star in the center of the image. NASA, ESA, K. Pontoppidan

Astronomers first observed the shadow of HBC 672 in 2018, and theorized the star has a planet-forming disk around it which, although not observed directly, casts a shadow onto a cloud behind it. And now, seeing this shadow move, they think that it could be caused by a planet passing through the disk and warping it, which in turn warps the shadow.

“You have a star that is surrounded by a disc, and the disc is not like Saturn’s rings — it’s not flat. It’s puffed up,” lead author Klaus Pontoppidan explained in a statement. “And so that means that the light from the star, if it goes straight up, can continue straight up — it’s not blocked by anything. But if it tries to go along the plane of the disc, it doesn’t get out, and it casts a shadow.”

Serpens Nebula, seen by HAWK-I
This image shows the Serpens Nebula as seen by the HAWK-I instrument installed on the Very Large Telescope of the European Southern Observatory. The filters used by HAWK-I to create this image cover wavelengths similar to the filters used by Hubble. ESO

Even though the disk itself is too small and far away to be seen by Hubble, the researchers believe that it is saddle-shaped, which would explain the apparent movement of the shadow. “If there were just a simple bump in the disk, we’d expect both sides of the shadow to tilt in opposite directions, like airplane wings during a turn,” team member Colette Salyk said in the statement.

The shadow is absolutely massive, at around 200 times the diameter of our solar system. In fact, it’s so large that it takes around 45 days for light from the star to travel to its edge.

The findings will be published in the Astrophysical Journal.

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