Planetesimals Are Buffeted by Wind in their Nebula, Throwing Debris into Space

This artist's illustration shows planetisimals around a young star. New research shows that planetesimals are blasted by headwind, losing debris into space. Image Credit: NASA/JPL

Before planets form around a young star, the protosolar disk is populated with innumerable planetesimals. Over time, these planetesimals combine to form planets, and the core accretion theory explains how that happens. But before there are planets, the disk full of planetesimals is a messy place.

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Arrokoth is Covered in Bizarre Mounds

The large mound structures that dominate one of the lobes of the Kuiper belt object Arrokoth are similar enough to suggest a common origin. Credit: Southwest Research Institute.

When New Horizons flew past Arrokoth in 2019, it revealed close-up images of this enigmatic Kuiper Belt Object for the first time. Astronomers are still studying all the data sent home by the spacecraft, trying to understand this two-lobed object, which looks like a red, flattened snowman.

Scientists have now identified 12 mounds on Arrokoth’s larger lobe, which are roughly the same size – about 5-kilometers long – as well as the same shape, color, and reflectivity. The scientists think their similar look is because they all formed the same way, where icy material slowly accumulated on the surface of Arrokoth.

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Pluto Team Updates Science From the Solar System’s Edge

Since its last flyby, of the Kuiper Belt object Arrokoth, the New Horizons mission has been exploring objects in the Kuiper Belt as well as performing heliospheric and astrophysical observations. Courtesy: Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute//Roman Tkachenko
Since its last flyby, of the Kuiper Belt object Arrokoth, the New Horizons mission has been exploring objects in the Kuiper Belt as well as performing heliospheric and astrophysical observations. Courtesy: Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute//Roman Tkachenko

Nearly eight years after its historic Pluto flyby, NASA’s New Horizons probe is getting ready for another round of observations made from the icy edge of the solar system — and this time, its field of view will range from Uranus and Neptune to the cosmic background far beyond our galaxy.

Scientists on the New Horizons team shared their latest discoveries, and provided a preview of what’s ahead, during this week’s Lunar and Planetary Science Conference in The Woodlands, Texas.

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New Horizons is so Far From Earth That the Positions of the Stars Look a Little Different From its Perspective

Credit: NASA/JHUAPL

In July of 2015, the New Horizons spacecraft made history when it became the first robotic explorer to conduct a flyby of Pluto. This was followed by another first, when the NASA mission conducted the first flyby of a Kuiper Belt Object (KBO) on December 31st, 2018 – which has since been named Arrokoth. Now, on the edge of the Solar System, New Horizons is still yielding some groundbreaking views of the cosmos.

For example, we here on Earth are used to thinking that the positions of the stars are “fixed”. In a sense, they are, since their positions and motions are relatively uniform when seen from our perspective. But a recent experiment conducted by the New Horizons team shows how familiar stars like Proxima Centauri and Wolf 359 (two of the closest stars in our neighbors) look different when viewed from the edge of the Solar System.

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New Horizon’s Flyby Target 2014 MU69 Gets its Official Name: Arrokoth

Rev. Nick Miles, of the Pamunkey Tribe, opens the 2014 MU69/Arrokoth naming ceremony at NASA Headquarters with a traditional Algonquian song. Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

On July 14th, 2015, the New Horizons made the first-ever flyby of Pluto. As if that wasn’t enough, the mission made history again with the flyby of the Kuiper Belt Object (KBO) 2014 MU69 on December 31st, 2018. This constituted the farthest encounter from Earth with a celestial object, which the team had nicknamed Ultima Thule – a mythical northern island beyond the borders of the known world in Medieval literature.

Unfortunately, this name has generated some controversy due to the fact that it is also the name white supremacists use to refer to a mythical homeland. So with the consent of the tribal elders and representatives of the Powhatan nations, the New Horizons’ team recommended a new name for the KBO. Henceforth, it will be known as “Arrokoth“, the word for “sky” in the Powhatan/Algonquian language.

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