Space Telescope Science
Finding lots of dust around stars may not sound like anything astronomers would get excited about. The universe is a dusty place. But dust around a young star can be evidence that planet formation is taking place. This isn’t a new idea. In 1755, German Philosopher Immanuel Kant first proposed that planets formed around our Sun in a debris disk of gas and dust. Astronomers imagined that this process might take place around other stars.
They had to wait until the early 1980s for the first observational evidence for a debris disk around any star to be uncovered. An edge-on debris disk was photographed around the southern star Beta Pictoris. Beta Pictoris remained the poster child for such debris systems until the late 1990s when the Hubble Space Telescope’s second-generation instruments, which had the capability of blocking out the glare of a central star, allowed many more disks to be photographed. Now, they are thought to be common around stars. About 40 such systems have been imaged to date, largely by Hubble.
In this recent image, Hubble uncovers a vast, complex dust structure, about 150 billion miles across, enveloping the young star HR 4796A. A bright, narrow inner ring of dust is already known to encircle the star, based on much earlier Hubble photographs. It may have been corralled by the gravitational pull of an unseen giant planet. This newly discovered huge dust structure around the system may have implications for what this yet-unseen planetary system looks like around the 8-million-year-old star, which is in its formative years of planet construction.