New Delhi: Astronomers have discovered a violent collision in one of the many debris disks surrounding a newborn star in the constellation of Piscis Austrinus
called Fomalhaut. The star is at a distance of only 25 lightyears from the Earth, was formed around 440 million years ago, and is one of the brightest objects in the night sky. It is brighter and more massive than the Sun, and collapsed from a dense clump of dust and gas. There are several belts of leftover material surrounding it. In 2008, scientists first spotted a candidate exoplanet dubbed Fomalhaut b, which now appears to be an expanding cloud of debris, the result of colliding planetesimals.
Illustration of the collision. (Image Credit: NASA, ESA, STScI, Ralf Crawford (STScI)).
This debris cloud has been dubbed circumstellar source 1 (CS1). While looking for CS1 in follow-up observations, the researchers were surprised to discover a second source of light, that also appears to be a dust cloud, the result of another collision, which has now been dubbed CS2. The astronomers are witnessing the assembly of planets in orbit around the star, and such interactions are believed to have been common in the debris disk surrounding the newborn Sun during the infancy of the Solar System. The two debris clouds are in close proximity to each other, which is a mystery in itself.
Observations challenge theories
If the collisions were random between asteroids and planetesimals, then the two circumstellar sources should not have been in such close proximity, positioned along the inner portion of the outer debris disk. Only one collision ever 100,000 years or so are predicted by the model, while the astronomers have spotted two in a span of 20 years. The researchers estimate that the objects that produced both the dust clouds measured around 60 km across, with an estimated 300 million such objects in orbit around Fomalhaut. Such debris clouds can be a source of false positives for those hunting exoplanets. The researchers plan to continue tracking the evolution of the debris clouds.
