In a paper published in the journal Nature, available online here (abstract only to non-subscribers), astronomers report the discovery of a sub-kilometer Kuiper Belt Object (KBO). The discovery was made using a stellar occultation (that is, a star’s light blocked by an object). The problem is that such sub-kilometer sized Kuiper Belt Objects have been predicted to exist in larger quantities than yet discovered. These astronomers also provide an explanation of why the occurence of such small KBOs is so low. It appears to be related to a process known as “collisional erosion.”
The Hubble Space Telescope (HST) has been valuable in the search for solar system objects — including worldlets well beyond the orbit of Neptune. This region is called the Kuiper Belt and it’s a vast ring of icy debris. Material in this debris ranges from dust-sized particles up to objects the size of miniature worlds — the so-called Kuiper Belt Objects (KBOs).
Recently, scientists studying archived HST pointing system data found the telltale signature of a tiny KBO that lies some 6.7 billion kilometers (4.2 billion miles) from Earth. At roughly 975 meters (3,200 feet) across, it is the smallest KBO ever found. It is also the first observational evidence for a population of comet-sized bodies in the Kuiper Belt that are being ground down by collisions. What this means is that icy debris particles in this part of the solar system collide and break apart. This results in changes in the population of objects in the Kuiper Belt. These changes can be as simple as cracks and craters or involve more complex processes like heating and melting, which alters the chemical composition of the objects. Thus, over the course of 4.56 billion years, the Kuiper Belt has evolved quite a bit from its “pristine” state, right after the formation of the Solar System.
Studying this region also has implications for the study of such rings around other stars, something ELSE that Hubble does very well. Its observations of nearby stars show that a number of them have Kuiper Belt-like disks of icy debris encircling them. These disks are the remnants of planetary formation, just as our own KBO is the icy repository of material left over after the Sun and planets formed more than 4.5 billion years ago. Studying our own and distant KBO populations help scientists understand the evolutionary history of planetary systems, particularly such icy debris disks. For these distant stars, Hubble scientists predict that over billions of years the debris should collide, grinding the KBO-type objects down to ever smaller pieces that were not part of the original debris population. For more information on this discovery, visit the news announcement about it at the Hubble Space Telescope web site page.