A new study has revealed that a young star in the nearest star system, known to astronomers as the Beta Pictoris Moving Group, is being bombarded by a host of objects believed to be exocomets. The inward flight of the objects could, according to the study from NASA's Goddard Space Flight Center, be indicative of the phenomenon of sun-grazing comets that might be prevalent in young star systems.
Space.com reported this week that Carol Grady and a NASA research team at the Goddard Space Flight Center in Greenbelt, Maryland, announced that, with the use of the Hubble Space Telescope, exocomets had been detected diving toward the star HD 172555. The exocomets, so called because they are cometary bodies that exist outside the solar system, appear to be moving inward toward HD 172555, found not through direct detection, but due to observations made of nearby gases, which are a by-product of what remains after a disintegrating comet comes into close contact with a Jupiter-sized planet.
The comets' inward momentum is a result of what astronomers refer to as "gravitational stirring," which is the process of the gigantic planet's catapulting force that flings the far-smaller comet toward a parent star. The same process has occurred in the solar system and can be observed when sun-grazing comets plunge into the sun. NASA astronomers say that the occurrence is fairly routine.
"Seeing these sun-grazing comets in our solar system and in three extrasolar systems means that this activity may be common in young star systems," Carol Grady, lead author of the study from NASA's Goddard Space Flight Center, said in the statement (which can be found at Hubblesite). "This activity at its peak represents a star's active teenage years. Watching these events gives us insight into what probably went on in the early days of our solar system, when comets were pelting the inner solar system bodies, including Earth. In fact, these star-grazing comets may make life possible, because they carry water and other life-forming elements, such as carbon, to terrestrial planets."
The theory of comets striking the Earth over and over to supply a young planet with water is nothing new and easily transferable to exoplanets. So, too, is the theory -- called "panspermia" -- of comets bearing life-introducing elements, proteins, and amino acids and/or incubated or dormant living organisms to seed a hospitable planet's surface. But the HD 172555 findings are the second such detection around a young star, thus far, and is suggestive that the phenomenon is fairly common.
The star itself, located in the Beta Pictoris Moving Group (which is the closest star system to Earth) could be a breeding ground for terrestrial planets, Grady surmised in the statement. The star, for which the group is named, has been found to have a gas giant planet in its protoplanetary disk (an accretion disk formed in orbit around a young star made of gas and dust).
Still, Grady and the NASA researchers do not know for certain if the objects diving toward HD 172555 are actually comets.
Although the gaseous leftovers in the far system is consistent with cometary material, astronomers still have yet to detect the tell-tale chemical fingerprints of oxygen and hydrogen to confirm that comets were their creative agent.
"Hubble shows that these star-grazers look and move like comets, but until we determine their composition, we cannot confirm they are comets," Grady said in the statement. "We need additional data to establish whether our star-grazers are icy like comets or more rocky like asteroids."
In other recent findings, as reported by redOrbit, astronomers at the University of Berkeley and Clarion University announced that their research has detected six stars around distant stars that suggest exocomets may be just as common throughout the galaxy as exoplanets. Researchers based the deduction on the discovery of 10 stars, which include the most recent findings, that display exocomets in their orbits. Those same stars having massive surrounding disks of potential planet-forming collections of gas and dust.
The comets are "sort of the missing link in current planetary formation studies," said Barry Welsh, a research astronomer at U.C. Berkeley´s Space Sciences Laboratory.
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