The Hubble Space Telescope has spotted evidence of ‘kamikaze’ comets plummeting straight into a young star just 95-light years away from Earth.
Researchers suspect these doomed exocomets are ‘catapulted’ to their demise in the 23-million-year-old star by a mysterious Jupiter-sized planet that lurks somewhere nearby.
This phenomenon, known as ‘gravitational stirring,’ could provide insight on the ways falling comets once brought water to Earth and other planets in the ancient solar system, and thus made life possible.
According to NASA, the young star called HD 172555 is the third extrasolar system in which scientists have detected ‘doomed, wayward comets.’
And, each system has been young, at under 40 million years old.
The exocomets spotted by Hubble weren’t seen directly – instead, the space telescope captured their gaseous spectral ‘fingerprints,’ or, what’s thought to be the vaporized remnants of their icy nuclei.
Astronomers say these events are likely caused as the exocomets are deflected by the gravity of an unseen Jupiter-sized planet.
Similar phenomenon have been detected in our own solar system, as sun-grazing comets fall into the sun.
‘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,’ said lead author Carol Grady, of Eureka Scientific Inc and NASA’s Goddard Spaceflight Center.
‘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.’
HD 172555 is a part of a collection of stars known as the Beta Pictoris Moving Group, all born from the same stellar nursery.
The researchers say this is the second member of the group that harbors comets of this kind; Beta Pictoris, the group’s namesake, also devours exocomets that get too close.
Scientists have also spotted a young gas-giant planet within the star’s debris disk.
This star group is the closest bunch of young stars to Earth, and at least 37.5 percent of the larger ones have either a directly imaged planet, such as 51 Eridani b in the 51 Eridani system, or star-grazing bodies falling into them.
At this age, these starts should be building terrestrial planets, Grady said.
French researchers first spotted the exocomets using data from 2004-2011 captured by the European Southern Observatory’s HARPS (High Accuracy Radial velocity Planet Searcher) planet-finding spectrograph.
Grady’s team then followed up in 2015 using Hubble’s Space Telescope Imaging Spectrograph (STIS) and the Cosmic Origins Spectrograph (COS).
During the study, they conducted spectrographic analyses in ultraviolet light, allowing the space telescope to identify the signature of certain elements.
Two observations were made by the telescope, separated by six days, revealing silicon and carbon gas in the starlight.
The gas was moving at about 360,000 miles per hour across the star face.
This is likely the remnants of the exocomets after they broke apart, creating a gaseous debris that disperses across the front of the star.
‘As transiting features go, this vaporized material is easy to see because it contains very large structures,’ Grady said.
‘This is in marked contrast to trying to find a small transiting exoplanet, where you’re looking for tiny dips in the star’s light.’
Hubble had a clear view of the activity, the researchers say, with the HD 172555 debris disk slightly inclined to the telescope’s line of sight.
In future observations, the team plans to look for oxygen and hydrogen, which would confirm the identity of these objects as comets.
‘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.
‘We need additional data to establish whether our star-grazers are icy like comets or more rocky like asteroids.’