Beta Pictoris is a young star, roughly 20 million years old, and located about 64 light-years away from Earth. It is surrounded by a vast disk of dust and rubble where planets are still forming—astronomers have already found three. In a new Science study, a team led by Sarah Betti, an astronomer at the Space Telescope Science Institute in Baltimore, used the James Webb Space Telescope to look for ice in this disk. Researchers found both water and carbon dioxide ice.
The water ice is glassy rather than crystalline, and it is mixed with carbon dioxide in roughly the same proportions we see in comets of our own Solar System. This suggests ingredients necessary to form water-rich worlds might be common around young stars.
Beta Pictoris is one of the best studied stars in the sky. Its disk was among the first ever imaged, back in 1984, and we see it almost exactly edge-on, which makes it a natural laboratory for studying how planetary systems grow. It’s what astronomers call a debris disk, where the dust is constantly replenished by collisions among comets and planetesimals, small bodies that are the building blocks of planets.
The outer parts of the disk are far enough from the star that water and other volatile molecules should freeze into solid ice. The disk holds a large reservoir of carbon monoxide gas, which ultraviolet light from the star should destroy within 50 to 300 years. For that gas to still be there, something must keep replenishing it—most likely it’s released from ice when volatile-rich comets collide. The properties of the planet Beta Pictoris b also suggest it formed from ice-rich material.
Yet despite plenty of reasons to suspect the system is full of ice, earlier searches have failed to find it. Attempts to detect water vapor found nothing, and a search for the telltale dip that water ice leaves in starlight at a wavelength of 3 micrometers also failed.
