Hubble reveals a giant cosmic "Bat Shadow"

Shadows on Earth can be mysterious and disturbing, but when they happen in space, they can convey information that we might not know otherwise. In a stellar nursery called the Serpens Nebula, at nearly 1,300 light-years away, a young star's shadow play reveals the secrets of his invisible disk forming a planet. The near infrared vision of NASA's Hubble Space Telescope captured the shadow projected by the bright light of the nascent star blocked by this disk.

Named HBC 672, this Sun-like star is surrounded by a ring of dust, rocks and ice, a disk too small and too far to be seen, even by Hubble. But like a little fly walking in the beam of a flashlight shining on a wall, its shadow is projected largely on the cloud in which it was born.

In this Hubble image, the function – nicknamed the "Bat Shadow" – covers about 200 times the length of our solar system. It is visible in the upper right of the image.

"This is an analogue of what the solar system looked like when it was only 1 or 2 million years ago," said Klaus Pontoppidan, astronomer at the same time. Institute of Space Telescope Sciences (STScI) in Baltimore, Maryland. "For all we know, the solar system has already created a shadow like this."

The presence of a shadow means that the disc is viewed almost marginally. This is something that could not be known otherwise because of the great distance of the disc from us, which makes it too small to be seen by Hubble.

The shadow of the disc is similar to that produced by a cylindrical shade. The light escapes from the top and bottom of the shadow, but along its perimeter, dark cones of shaded form. Although the disc that creates the shadow is a common object around young stars, the combination of an outline vision angle and the surrounding nebula is rare.

Scientists can use the shadow to determine the shape of the disc. For example, they now know that the disc is swollen, which implies that it is full of essence. Although most of the shadow is completely opaque, scientists can look for color differences along its edges, in which light enters. They can use the shape and color of the shade to determine the size and composition of the dust grains suspended in the disc.

"These shadows are not easily visible in visible light, but the star discs and shadows they project onto the surrounding nebula can be easily detected in infrared light," said Max Mutchler, researcher and instrument expert at STScI. "This infrared bat shadow reveals the properties of the small dusty disk and the much larger nebula."

The shadow is an example of what the future James Webb Space Telescope will be able to study in more depth. "Webb's power lies in its ability to see the dust and gases in these disks to understand the material that makes up these planet-forming environments," said STScI scientist Alexandra Lockwood.

A similar-looking shadow phenomenon emanates from another young star, at the top left of Hubble's image. Bottom right, what seems to be a void is probably part of a cloud in the foreground. The double red star light inside the "void" is partially blocked by this cloud.

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