As if searching through the cosmos like a detective on an intense investigation looking for an ancient piece of evidence, the Hubble Space Telescope has identified an extraordinary happening happening in a star system close by, named Fomalhaut, only 25 light-years from our own planet earth a massive collision of planetesimals that resulted in an incandescent dusting of debris.
One of the brightest stars in the constellation Piscis Austrinus has been found to have a complicated system of debris disk orbits around it. This debris disk is produced during the birth of the star and comprises snowball状objects as well as rock.Photograph taken recently with the Hubble telescope also revealed the appearance of a new point of brightness dubbed “circumstellar source 2 ” (cs2). Astronomer Paul Kalas of the University of California, Berkeley, noted, “This point of light was not in all of our previous Hubble images, which means we have just witnessed a violent collision between two massive objects.”
And this is in fact not the first occurrence of this phenomenon within the system of Fomalhaut. Another bright object was believed to be a planet in the year 2008, named Fomalhaut b. Later, it was found that this object was called “circumstellar source 1” or (cs1) – this is an area of dusty debris caused by an explosion of the same kind. The occurrence of cs2 in the immediate next region and still in the same outer ring of the area of dusty debris is rather surprising, considering that this phenomenon is expected only once in 100,000 years and in this system of Fomalhaut, two have already been found in two decades.
On the basis of brightness and rates of expansion of objects, both cs1 and cs2 objects were formed by the collision of objects of approximate size 60 kilometers. On the basis of these results, it has been revealed that approximately 300 million objects exist within the Fomalhaut system. The collision is taking place within a dynamic environment, and the gravitational interactions would comprise planetary resonance.
The dynamics underlying such collisions are also quite complex. Moreover, during the early stages of formation of planets within young star systems, the role of debris disks as reservoirs of planetesimals is also relevant, which are later upsets through the role of gravitational resonances. Even within our Solar System, as a matter of fact, the ν6 secular resonance with the planet Saturn is one such important cause through which asteroids get transported to Earth-crossing orbits. Within an exoplanetary system such as that of Fomalhaut, such events may also be at play, resulting in the augmentation of collisions within a specific region of the disk.
It is worth noting that if cs1 and cs2 are indeed close to each other in space, then it is suggestive that the dynamics which are at play during these collisions are localized on scales which may result in the trapping of planetesimals in mean-motion resonances with an unseen planet. Once the Collision occurs, the dust debris forms soon after that. This dust debris begins small and bright, but it keeps on increasing in size since the radiation pressure from the star pushes the smaller dust particles outwards, which may form an elongated or cometary form of the debris debris. This was seen in the case of CS1.
In the case of CS2, the formation of the dust debris, as well as the “dust avalanche” triggered by the collision among the debris in the belt that brightens up the whole system, would be eagerly observed by the scientists. The high resolution in the visible section of the electromagnetic spectrum, provided by Hubble’s imaging capabilities, has been essential in the search for these transient objects. The coronograph assists in the reduction of light from Fomalhaut, making it easier for the observer to identify subtle details associated with the debris disk. However, since Hubble is now an old mission, new technology is being employed jointly, as in the case of the new “James Webb Space Telescope” (Webb). The “Near-Infrared Camera” (NIRCam) in this new telescope can produce spectra for cs2, which determines the scale for dust particle sizes as well as the presence of water ice.
The previous findings have massive implications for exoplanets. “Dust clouds such as cs1 and cs2 may look like a planet reflecting light,” which is another major point for direct imaging mission projects in focusing their cameras on earth-like planets. According to Kalas, “A big dust cloud can fool observers for many years and may look like a planet.” The ability for observation to differentiate real planets from other transient objects may play a pivotal role for new mission projects in becoming successful. Within a time frame of just two occasions, Hubble has placed Fomalhaut as a “natural laboratory for understanding the physical processes underlying asteroid planetary collisions.” Firstly, this will help explain more clearly “the violent adolescence of planetary systems, as well as provide a deeper understanding for the origins of planets and potentially ‘life-bearing’ planets within the resulting chaos.”
