Small Kuiper Belt Objects are Surprisingly Rare

According to new research at the Southwest Research Institute, the concentration of small objects in the Kuiper Belt is quite low.

The discovery was made by the renowned New Horizons spacecraft of NASA. It has the privilege of taking a first close-up look at the Pluto. Similarly, it also explored Ultima Thule which holds great importance and holds the key to the knowledge of solar system evolution. New Horizons also visited the objects in the Kuiper Belt and found something extremely strange about them.

Kuiper Belt

Kuiper Belt is also known as the ‘Edgeworth Kuiper Belt’. It is a circumstellar disc which exists in the outer part of the solar system after extending from the orbit of Neptune. In simple words, it is a much larger (20 to 200 times in scale) asteroid belt. This donut-shaped region of icy bodies was named after a Dutch-American astronomer, Gerard Kuiper. The first Kuiper Belt Object (KBO) discovered was named as ‘Albion’. More than a thousand KBOs have been found since this discovery and it is believed that over a hundred thousand more KBOs exist in the area. Astronomers believe some objects have rather odd orbits which can extend up to 100 Astronomical Units (AU) from the Sun.  

The Latest Discovery and its Significance

New Horizons discovered a small number of craters on Charon, Pluto’s largest moon. This observation made astronomers believe that the objects are quite rare in this asteroid belt. Kelsi Singer, a member of the Southwest Research Institute (SRI), referred to that and said,

“These smaller Kuiper Belt Objects (KBOs) are much too small to really see with any telescopes from such a great distance. New Horizons flying directly through the Kuiper Belt and collecting data there was key to learning about both large and small bodies of the Belt. This surprising lack of small KBOs changes our view of the Kuiper Belt and shows that either its formation or evolution, or both, were somewhat different than those of the asteroid belt between Mars and Jupiter. Perhaps the asteroid belt has more small bodies than the Kuiper Belt because its population experiences more collisions that break up larger objects into smaller ones.”

New Horizons and Kuiper Belt

Along with its main mission of studying the Pluto system, New Horizons is also tasked with understanding the structure and make-up of the Kuiper Belt. The typical planetary models of our solar system show that our solar system formed 4.6 billion years ago as a result of the gravitational collapse of a molecular cloud, while our star and planets formed from some of the material that collapses. The name given to this process is ‘Accretion’.

Craters on a body in the solar system point towards the presence of smaller bodies near it which likely crashed into the bigger body at some point.  Since Pluto is quite far from Earth, the detailed observation was not possible until the 2015 flyby of New Horizons. The observations show the presence of mountains that are almost 4 km tall. Geologic activity has altered the surface of the planet significantly. However, massive nitrogen glaciers are still present. Dr. Alan Stern talked about that in the following words:

“This breakthrough discovery by New Horizons has deep implications. Just as New Horizons revealed Pluto, its moons, and more recently, the KBO nicknamed Ultima Thule in exquisite detail, Dr. Singer’s team revealed key details about the population of KBOs at scales we cannot come close to directly seeing from Earth.”

View of the Kuiper Belt

Singer acknowledged that these shocking findings did change their view of the Kuiper Belt. She mentioned that this surprising lack of small KBOs shows that either its formation or evolution or both, were somewhat different than those of the asteroid belt between Mars and Jupiter. Perhaps the asteroid belt has more small bodies than the Kuiper Belt because its population experiences more collisions that break up larger objects into smaller ones. She concluded the discovery by saying,

“With the successful flyby of Ultima Thule early this year, we now have three distinct planetary surfaces to study. This paper uses data from the Pluto-Charon flyby, which indicate fewer impact craters than expected. And preliminary results from Ultima Thule support this finding.”

Now that the spacecraft is past the Ultima Thule, it will continue to study the Kuiper Belt and update the existing data we have on the ‘belt’. New Horizons is expected to remain operational till 2030 and astronomers are hopeful it find more fascinating stuff in the Kuiper Belt.