The shaving flight of the New Horizons spacecraft past the object still offers us new insights a year later.
On January 1, 2019 New Horizons spacecraft sailed past the bucket seat object Arrokoth. A special day, because the space stone – which at the time was still referred to as Ultima Thule – is the freshest celestial body that we have ever honored with a visit. The shaving flight offered humanity a close-up of an icy remnant from the time the solar system was still forming and also gave us an idea of the vastness of the area beyond the orbit of Neptune. But there’s more. Because data from the mission also offer new insights into how planets and planetesimals – building blocks of planets – were formed.
More about the Kuiper Belt
Arrokoth is one of the thousands of well-known small icy worlds in the Kuiper Belt; a donut-shaped region that is located beyond the orbit of Neptune. The Kuiper belt is quite extensive: it is estimated that it houses hundreds of thousands of icy celestial bodies larger than 100 kilometers. In addition, a sloppy billion comets can be found. The Kuiper belt starts about 30 AU from the sun and is about 20 AU wide. Arrokoth is therefore one of the many icy objects in a vast area. The object is located about 6.5 billion kilometers from the Earth and is about 1 billion kilometers further than Pluto: the dwarf planet that New Horizons skimmed past in 2015. Scientists have never had the opportunity to look at an object at such a great distance from the earth.
Arrokoth
During the shaving flight past Arrokoth, researchers got a better idea of its shape, geology, color and composition. And a new research team is now building on that. “Arrokoth is the furthest, most primitive, and unspoiled object ever explored by spacecraft,” says lead investigator of the New Horizons project Alan Stern. “We knew it would have a unique story to tell. And now it teaches us how planetesimals were formed. We believe that this result represents a significant advance in our understanding of how planets themselves are formed. ”
Planets formation
There are two prevailing theories about how the first planets began to form. The first theory examines how small grains bumped into each other brutally and then stuck to each other. For millions of years, matter accumulated through this type of violent collision, which eventually resulted in planets. The second theory tells how certain areas had a higher density of particles that were pulled together. As a result, material particles collided gently.
Arrokoth formation
Data collected about Arrokoth now gives more insight into which theory is possibly right. The first images of Arrokoth showed that the object consists of two connected “lobes”. In addition, researchers discovered that Arrokoth has a smooth surface and a uniform composition. The team collected more data in the following months. And thanks to advanced computer simulations, researchers got a better picture of how Arrokoth must have formed. Their analysis shows that the lobes were once two separate, small objects. These were very close to each other and turned around each other, and then merged into a large object through a soft collision.
Soft hearted
These findings are interesting. It indicates that Arrokoth originated in a fairly gentle way. “Arrokoth doesn’t look like it was caused by violent clashes, but rather by a complicated dance, in which two objects circled around each other before they merged,” says researcher William McKinnon. And that is quite an exciting find. “It reforms our knowledge and understanding of how planetary bodies form,” concludes researcher Lori Glaze. Two other important features support the conclusion. This is because the uniform color and composition of Arrokoth indicate that the object is formed from a small, uniform cloud of material in the sun nebula, as predicted in the second theory. “Arrokoth has physical characteristics of a celestial body that slowly came together, consisting of” local “matter from the sun nebula,” says researcher Will Grundy. “An object like Arrokoth would not be shaped or look like this in a chaotic environment.”
New Horizons is currently located at a distance of about 7.1 billion kilometers from the earth and whizzes through the Kuiper belt at an unprecedented 50,400 kilometers per hour. Here the spacecraft maps the environment of charged particles and dust. It also keeps its eyes focused on other bucket belt objects that he passes. These are really too far away to study properly, but the team can measure aspects such as certain surface properties and shape. This summer the team will use telescopes to search for new interesting Kuiper belt objects. And, if the amount of fuel permits, a beautiful shaving flight may be undertaken again along one of these objects.
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