SPACE/COSMOS
Why some objects in space look like snowmen
Gravitational collapse may explain the origin of contact binaries in the Kuiper Belt, MSU simulation finds
image:
This image was taken by NASA's New Horizons spacecraft on Jan. 1, 2019 during a flyby of Kuiper Belt object 2014 MU69, informally known as Ultima Thule. It is the clearest view yet of this remarkable, ancient object in the far reaches of the solar system – and the first small "KBO" ever explored by a spacecraft.
view moreCredit: NASA
Astronomers have long debated why so many icy objects in the outer solar system look like snowmen. Michigan State University researchers now have evidence of the surprisingly simple process that could be responsible for their creation.
Far beyond the violent, chaotic asteroid belt between Mars and Jupiter lies what’s known as the Kuiper Belt. There, past Neptune, you’ll find icy, untouched building blocks from the dawn of the solar system, known as planetesimals. About one in 10 of these objects are contact binaries, planetesimals that are shaped like two connected spheres, much like Frosty the Snowman. But just how these objects came to be without the help of a magic silk hat was an open question.
Jackson Barnes, an MSU graduate student, has created the first simulation that reproduces the two-lobed shape naturally with gravitational collapse. His work is published in the Monthly Notices of the Royal Astronomical Society.
Earlier computational models treated colliding objects as fluid blobs that merged into spheres, making it impossible to form these unique shapes. Thanks to MSU’s Institute for Cyber-Enabled Research, or ICER, and its high-performance computing cluster, Barnes’ simulations produce a more realistic environment that allows objects to retain their strength and rest against one another.
Other formation theories involve special events or exotic phenomena that, while possible, aren’t likely to happen on a regular basis.
“If we think 10 percent of planetesimal objects are contact binaries, the process that forms them can’t be rare,” said Earth and Environmental Science Professor Seth Jacobson, senior author on the paper. “Gravitational collapse fits nicely with what we’ve observed.”
Contact binaries were first imaged up close by NASA’s New Horizons spacecraft in January 2019. These images prompted scientists to take another look at other objects in the Kuiper belt, and it turned out that contact binaries accounted for about 10 percent of all planetesimals. These distant objects float mostly undisturbed and safe from collisions in the sparsely populated Kuiper belt.
In the early days of the Milky Way, the galaxy was a disc of dust and gas. Remnants of the galaxy’s formation are found in the Kuiper Belt, including dwarf planets like Pluto, comets and planetesimals.
Planetesimals are the first large planetary objects to form from the disc of dust and pebbles. Much like individual snowflakes that are packed into a snowball, these first planetesimals are aggregates of pebble-sized objects pulled together by gravity from a cloud of tiny materials.
Occasionally as the cloud rotates, it falls inward on itself, ripping the object apart and forming two separate planetesimals that orbit one another. Astronomers observe many binary planetesimals in the Kuiper belt. In Barnes’ simulation, the orbits of these objects spiral inward until the two gently make contact and fuse together while still maintaining their round shapes.
How do these two objects stay together throughout the history of the solar system? Barnes explains they’re simply unlikely to crash into another object. Without a collision, there’s nothing to break them apart. Most binaries aren’t even pocked with craters.
Scientists long suspected that gravitational collapse was responsible for forming these objects, but they couldn’t fully test the idea. Barnes’ model is the first to include the physics needed to reproduce contact binaries.
“We’re able to test this hypothesis for the first time in a legitimate way,” Barnes said. “That’s what’s so exciting about this paper.”
Barnes expects his model will help scientists understand binary systems of three or more objects. The team is also working to create a new simulation that better models the collapse process.
As more NASA missions explore uncharted realms of the solar system, Jacobson and Barnes suspect Frosty may have more distant cousins yet to be found.
Simulation of gravitational collapse [VIDEO] |
Jackson Barnes created this computer simulation showing how a contact binary’s two-lobed shape could be formed by gravitational collapse.
Jackson Barnes created this contact binary in a computer simulation showing how the two-lobed shape could be formed by gravitational collapse.
Credit
Michigan State University Jacobson Lab
This short movie shows the view of Kuiper Belt object 2014 MU69 (nicknamed Ultima Thule) as seen by NASA's New Horizons spacecraft from Dec. 7, 2018 to Jan. 1, 2019. During the approach, Ultima Thule transforms from a faint dot 20 million miles (31 million kilometers) away, indistinguishable from thousands of background stars, to a newly revealed world unlike any seen before, from a range of 5,000 miles (8,000 kilometers). The sequence consists of actual New Horizons images, taken at discrete intervals during the approach, supplemented with computer-generated intermediate frames in order to make a smooth movie. Time slows down during the movie to show clearly both the slow initial phases of the approach and the very rapid final stages. The final image is a parting crescent view of Ultima Thule, taken 10 minutes after closest approach occurred at 12:33 a.m. EST on Jan. 1.
Credit
NASA
Journal
Monthly Notices of the Royal Astronomical Society
Article Title
Direct contact binary planetesimal formation from gravitational collapse
Article Publication Date
19-Feb-2026
STEM IS DEI
PhD student maps mysterious upper atmosphere of Uranus for the first time
image:
Paola Tiranti of Northumbria University
view moreCredit: Northumbria University/Barry Pells
A Northumbria University PhD student has led an international team of astronomers in creating the first-ever three-dimensional map of Uranus's upper atmosphere, revealing how the ice giant's unusual magnetic field shapes spectacular auroras high above the planet's clouds.
Using the James Webb Space Telescope, led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency), Paola Tiranti and her colleagues observed Uranus for nearly a full rotation, detecting the faint glow from molecules up to 5,000 kilometres above the cloud tops.
The observations provide the most detailed picture yet of where the planet's auroras form and how energy moves through its atmosphere.
The study, published today (19 Feb) in Geophysical Research Letters, also confirms that Uranus's upper atmosphere has continued to cool over the past thirty years – a trend that has been surprising scientists for over three decades.
Auroras occur when energetic particles become trapped in a planet's magnetic field and strike the upper atmosphere, releasing energy that creates a signature glow.
Using Webb's Near-Infrared Spectrograph, the team mapped out the temperature and density of ions in Uranus's ionosphere, a region where the atmosphere becomes ionised and interacts strongly with the planet's magnetic field.
The measurements revealed that temperatures peak between 3,000 and 4,000 kilometres above the cloud tops, whilst ion densities reach their maximum around 1,000 kilometres.
Speaking about the findings, lead author Paola Tiranti said: “This is the first time we've been able to see Uranus's upper atmosphere in three dimensions. With Webb's sensitivity, we can trace how energy moves upward through the planet's atmosphere and even see the influence of its lopsided magnetic field.”
Uranus's magnetosphere is one of the strangest in the Solar System. Unlike Earth, where the magnetic field is relatively aligned with the planet's rotation axis, Uranus's magnetic field is tilted by nearly 60 degrees and offset from the planet's centre. This means its auroras sweep across the surface in complex ways.
The Webb observations detected two bright auroral bands near Uranus's magnetic poles, together with a distinct depletion in emission and ion density between them – a feature likely linked to how magnetic field lines guide charged particles through the atmosphere. Similar darkened regions have been seen at Jupiter, where magnetic field geometry controls particle flow.
Webb's data also confirmed that Uranus's upper atmosphere is still cooling, extending a trend that began in the early 1990s. The team measured an average temperature of around 426 kelvins (about 150 degrees Celsius), lower than values recorded by ground-based telescopes or previous spacecraft observations.
Understanding why Uranus is cooling, despite being so far from the Sun, could provide crucial insights into how ice giant planets regulate their atmospheric temperature.
Paola Tiranti said: “By revealing Uranus's vertical structure in such detail, Webb is helping us understand the energy balance of the ice giants. This is a crucial step towards characterising giant planets beyond our Solar System.”
The study is based on data from JWST General Observer programme 5073, led by Dr Henrik Melin of Northumbria University, which used the telescope's Integral Field Unit on 19 January 2025 to observe Uranus for 15 hours.
Planetary scientists from Northumbria University's Solar and Space Physics peak of research excellence have been involved in a number of research projects using data from Webb, specifically exploring the upper atmospheres of our solar system's giant gas planets – Jupiter, Saturn, Uranus and Neptune.
- Deep space telescope captures Neptune's auroras for the first time
- Unveiling Jupiter's upper atmosphere
- Uranus aurora discovery promises new riches from James Webb Space Telescope
- Telescope to provide insight into Solar System light shows
- Telescope reveals unexpected activity above Jupiter's Great Red Spot
The James Webb Space Telescope is the world's premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
Uranus (January 2025)
Credit
ESA/Webb, NASA, CSA, STScI, P. Tiranti, H. Melin, M. Zamani (ESA/Webb)
Paola Tiranti of Northumbria University
Credit
Northumbria University/Barry Pells
Journal
Geophysical Research Letters
Method of Research
Imaging analysis
Subject of Research
Not applicable
Article Title
JWST Discovers the Vertical Structure of Uranus' Ionosphere
Article Publication Date
19-Feb-2026
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