14 DAY TRIAL // A group of astronomers with the European Southern Observatory (ESO) recently used the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to study the protoplanetary disk around the nearby young star Beta Pictoris. The study revealed the presence of a large cloud of carbon monoxide gas orbiting the new star, something that is theoretically improbable.
The team says that any carbon monoxide (CO) around a freshly-formed star would get immediately destroyed by the intense starlight and radiation emissions released by that star. Beta Pictoris is estimated to be extremely young, just 8 to 20 million years old. It lies 63.4 light-years away, and it is already the second-brightest star in the constellation of Pictor.
The new study proposes that an active process must be replenishing the CO cloud around the star, otherwise there is nothing to explain its very existence. Frequent collisions between comets or other small icy objects may explain this replenishment process, but detecting such events is very difficult.
Beta Pictoris is a common astronomical target due to its proximity to Earth, as well as the fact that it has a confirmed extrasolar planet in its orbit. The alien world orbits its parent star at a distance of around 1.2 billion kilometers (745 million miles), slightly smaller than Saturn's distance from the Sun.
Astronomers believe that the presence of CO in the protoplanetary disk may be a good sign that any worlds yet to develop around this star may one day become habitable. Carbon monoxide itself is harmful to life, but the type of cometary bombardment that may be taking place near Beta Pictoris could be similar to the one that made Earth a proper place for the emergence and development of life.
Any CO that appeared during the formation of the star should have theoretically been destroyed within a century. Seeing it 20 million years later is definitely a sign that the chemical is being constantly replenished. “Unless we are observing Beta Pictoris at a very unusual time, the carbon monoxide must be continuously replenished,” says Bill Dent, an ESO astronomer with the Joint ALMA Office.
“The most abundant source of carbon monoxide in a young solar system is collisions between icy bodies, from comets up to larger planet-sized objects,” says the researcher, who was the lead author of a new paper detailing the findings. The work is published in the March 6 issue of the journal Science.
“To get the amount of carbon monoxide we observe, the rate of collisions would be truly startling – one large comet collision every five minutes. To get this number of collisions, this would have to be a very tight, massive comet swarm,” comments study coauthor Aki Roberge, an astronomer with the NASA Goddard Space Flight Center (GSFC) in Greenbelt, Maryland.
But undoubtedly the greatest mystery related to the recent ALMA observations is the position and shape of the CO, which lies in a single clump, some 13 billion kilometers (8 billion miles) away from Beta Pictoris. That is the equivalent of three times the average distance between Neptune and the Sun.
“Either the gravitational pull of an as yet unseen planet similar in mass to Saturn is concentrating the cometary collisions into a small area, or what we are seeing are the remnants of a single catastrophic collision between two icy Mars-mass planets,” comments University of Cambridge astronomer Mark Wyatt, another coauthor of the Science paper.