NASA's Hubble Space Telescope has spotted several comets diving toward a young star located about 95 light-years away from planet Earth.
Vaporized Remnants Of Disintegrated Comets
More aptly called exocomets because they were found outside of the solar system, the space rocks were not directly seen plunging into the 23-million-year-old star called HD 172555.
Their presence was inferred based on the nearby gas that was detected by the Hubble telescope. Scientists believe that the gas is the vaporized remnants of the icy nuclei of the comets.
The Hubble detected silicon and carbon gas in the star's light. At the speed of 360,000 miles per hour that the gas was moving across the face of the young star, astronomers think that Hubble is likely seeing material from comet-like objects that broke apart after streaking across the star's disk.
The gaseous debris is widely dispersed in front of the stars and is easy to see because it has very large structures. Carol Grady, from NASA's Goddard Space Flight Center, explained that this is in marked contrast to finding small transiting exoplanets, which require astronomers to look for tiny tips in the starlight.
Beta Pictoris Moving Group
HD 172555, which is part of a group of stars called the Beta Pictoris Moving Group, represents the third extrasolar system where astronomers have found these exocomets.
The Beta Pictoris Moving group is the closest star system to our planet and is possibly a breeding ground for terrestrial planets. Scientists are interested in studying it because of its proximity to our planet. At least 37. 5 percent of the more massive stars present in the group have a directly imaged planet or infalling star-grazing bodies.
Gravitational Steering
The presence of the doomed exocomets offers circumstantial evidence for a process known as gravitational steering by a Jupiter-size planet, wherein comets that get deflected by the gravity of the massive planet are catapulted into the star.
The mechanism hints of past and present activities of the comets in our solar system and may possibly explain how infalling comets could have transported water to our planet and the other planets in the solar system.
Scientists have already found similar phenomena in the solar system in the form of comets that routinely plunge into our sun.
Commonly Occurs In Young Star System
Grady said that the sun-grazing comets in the solar system and the star-diving comets in the three extrasolar systems mean that the activity may commonly occur in young star systems. She said that seeing these events offers insight into what likely happened in the early days of the solar system when the comets pelted into Earth and other inner solar system bodies.
"This activity at its peak represents a star's active teenage years," Grady said. "These star-grazing comets may make life possible, because they carry water and other life-forming elements, such as carbon, to terrestrial planets."
Grady and colleagues presented these findings at the meeting of the American Astronomical Society in Grapevine, Texas on Jan. 6.
