▲ Conceptual diagram of a Kuiper Belt object with debris expelling from a collision. Source: Dan Durda, FIAAA.
NASA, the American space agency, launched the New Horizons probe in January 2006 to become the first human to explore Pluto. After a long journey of nine and a half years, New Horizons observed Pluto and its satellites and transmitted them to Earth in July 2015. Thanks to this, scientists have confirmed that Pluto, a small icy body at the end of the solar system, is a mysterious icy body with a more complex topography than expected.
But New Horizons’ mission did not end there. New Horizons observed ‘486958 Arrowot’, an icy asteroid in the outer solar system in 2019. This asteroid was not originally a target in the mission, but was accidentally discovered close to New Horizons’ flight path and was added to the mission. Thanks to this, scientists had the opportunity to directly explore the ‘Kuiper Belt’, which is the most distant celestial body among the celestial bodies to which humanity has sent probes so far.
The Kuiper Belt is a collection of icy celestial bodies outside the orbit of Neptune in the solar system and is estimated to be distributed approximately 30 to 50 AU (1 AU is the distance between the Earth and the Sun, 150 million km). Short-period comets (comets with an orbital period of 2 to 200 years) are mainly known to originate here. However, because it is a collection of small celestial bodies far from the sun, there are many more aspects that have not yet been discovered.
A research team led by Alex Donner of the University of Colorado analyzed data from New Horizons and found evidence that the actual size of the Kuiper Belt is much larger than expected. The research team discovered clues that could help estimate the size of the Kuiper Belt using the Venetia Burney Student Dust Counter (VBSDC) mounted on New Horizons.
This device measures the density of very fine dust in space. Of course, this alone cannot directly prove the existence of Kuiper Belt objects, but it can provide important clues. This is because when icy asteroids in the Kuiper Belt collide with each other, they have no choice but to blow dust into the surrounding area.
Space dust above a certain concentration means that the Kuiper Belt is still not over. Therefore, the size of the Kuiper Belt can be indirectly measured by measuring the dust density along the flight path of New Horizons as it moves further away from the Sun.
The results of the study showed that the size of the Kuiper Belt was larger than expected, extending up to a distance of 80 AU. Most asteroids are more than millions of kilometers away from each other and are usually small with diameters of tens of kilometers or less, making direct observation from Earth difficult, but there are more small icy bodies in the outer solar system than expected.
Because New Horizons’ nuclear batteries are expected to operate until 2040, future data analysis is expected to reveal the exact size of the Kuiper Belt. I am curious about what new facts New Horizons will uncover as it continues its exploration mission after exploring Pluto and Arrokot, which is essentially the last asteroid.
Gordon Jeong Science Columnist [email protected]