July 20 marked the 50th anniversary of one of the biggest robotic spaceflight achievements in NASA’s history: the landing of the Viking 1 spacecraft on Mars. It was the first […]
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The Chinese Tianwen-2 mission has captured the first imagery of a space object that some astronomers are calling Earth’s “quasi-moon.”
The object was captured in images released by the China National Space Administration (CNSA), after its Tianwen-2 spacecraft reached the tiny asteroid 469219 Kamoʻoalewa. Initially discovered in 2016, the asteroid became the target of a sample return mission launched by China on 28 May 2025.
Officially the CNSA’s second mission under its Planetary Exploration of China Program, Tianwen-2 aims to return close to 100 grams of samples from the surface of the small object.
Quasi-moons are the name astronomers have for small, very distant objects that do not impact our planet’s tides or possess other characteristics associated with our primary moon.
These objects are nonetheless considered moon-like because they remain in our celestial neighborhood for extended periods, providing unique opportunities for studying near-Earth objects (NEOs) like asteroids, and the impact things like solar radiation and gravity have on them.
Although Kamoʻoalewa (also known as asteroid 2016 HO3) is the most well-known of Earth’s quasi-moons, it is one of seven that are currently known to astronomers. Kamoʻoalewa’s orbit is technically also around the Sun, rather than Earth, although its synchronized path keeps it locked closely to Earth’s orbit, thereby justifying its recognition as a “quasi-satellite.”
The object’s size and distance make it an ideal target for studying NEOs, and China leaped at the opportunity with the CNSA’s Tianwen-2 mission.
The Tianwen-2 spacecraft is currently nearing 20 kilometers from the 130 to 330-foot space rock, according to a statement CNSA released on Monday.
Along with a mission update, the CNSA also released new images, which are the first to officially document the object’s appearance. According to current mission timelines, Tianwen-2 will remain in the vicinity of 469219 Kamoʻoalewa until next April, and by sometime in November 2027, its return capsule is expected to reach Earth.
After its study of 469219 Kamoʻoalewa, Tianwen-2 will then make its way with the aid of a gravity assist in the direction of the comet 311P/PANSTARRS, arriving in its vicinity by January 2035.
“Going forward, the probe will gradually conduct more detailed scientific explorations to obtain information on the asteroid’s shape, material composition, and internal structure,” read the CNSA’s statement on Monday.
The agency said its ongoing collection of information will help to provide “support for preparations for sampling,” and the spacecraft will spend the next several months conducting reconnaissance of the asteroid before its sample collection begins, which will combine high-speed maneuvers with the deployment of a specialized robotic arm.
Following their collection, the samples will be delivered to a recovery site in the Gobi Desert after dropping into Earth’s atmosphere in November 2027.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.
China’s Tianwen-2 spacecraft has carried out a series of small propulsive maneuvers following a main burn June 7, setting up an asteroid rendezvous in July.
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Editor’s Note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.
Title: Dynamics of Planetary Rings Under Thermal Forces
Authors: Wen-Han Zhou et al.
First Author’s Institution: The University of Tokyo
Status: Published in ApJL
If you ask anyone what their favourite planet is, the answer you’ll most likely hear is Saturn. Why? Why else than the beautiful and intricate ring system surrounding the gas giant. The other gas and ice giants in our solar system — Jupiter, Uranus, and Neptune — have ring systems themselves but none quite as striking as Saturn’s. Would it surprise you to learn that astronomers’ best models have not yet totally explained why Saturn’s rings look the way they do?
In contrast, it may not surprise you to hear that people have been trying to explain the rings for as long as we have seen them with telescopes. We now know that planetary rings are collections of relatively small particles (think micrometre up to metre sized), most likely having once been the material of a larger body that was disrupted either by collisions or tidal forces. This material, due to the gravity of its local planet, is sculpted into a flat disc where more subtle interactions then lead to substructure forming within the disc such as gaps and ringlets. Many of these substructures are explained by well-understood physics — for example gaps being carved by embedded moonlets or resonances sculpting ring edges — though there remain some outstanding problems in our understanding.
The authors of today’s article set their sights on the problematic inner edge of Saturn’s A ring (Figure 1). They describe some mechanisms — namely the collisions of micrometeoroids within the rings — by which a sharp ring edge can be maintained, but there exists a gap in the understanding of how such an edge can form in the first place. All hope is not lost, though, as today’s authors reintroduce a physical process they call the “eclipse–Yarkovsky” effect, which seems to explain these phenomena.
Figure 1: A horizontally sliced image of Saturn’s rings shows the rich substructure and gaps within the various rings. Saturn, which is not shown here, would be to the left of the image. The authors of today’s article are particularly concerned with the bright and sharp inner (left side) edges of the A and B rings. Click to enlarge. [NASA/JPL/Space Science Institute]
The idea behind this process revolves entirely around light. When sunlight hits a particle within a planetary ring, non-absorbed sunlight imparts a little “bump” onto a particle, ever so slightly altering its trajectory. At the same time, some of the sunlight is absorbed into the particle, which heats it up; light is soon re-emitted via thermal radiation, which, again, can slightly change the trajectory of these tiny particles. From a point on the surface of each ring particle (see rightmost side of Figure 2), the photons from this thermal radiation are all emitted in random directions; however, across the whole surface of the particle there is a net force! These tiny particles are spinning, and so the side just near “sunset” is hottest and emitting the most thermal photons. In this way, the pressure from the sunlight plus the thermal radiation of each particle imparts a net torque on the ring itself which changes the angular momentum of the ring.
Figure 2: Starlight is the main source of light onto the particles that make up a planetary ring (right panel) though reflected light from the planet’s surface hits it too. This light “heats up” the ring and forms an asymmetry as the ring is eclipsed by the planet, which produces a net force. [Zhou et al. 2026]
After today’s authors detailed all of the math involved in this process (and there is a lot), they put it into practice to try to help explain Saturn’s curious rings. Including the eclipse–Yarkovsky effect together with other known effects that drive ring evolution allowed them to reproduce the optical depth profile (how thick the ring looks) of Saturn’s A ring better than ever before (notably the sharp inner edge in Figure 3). On top of this, the effect provides another avenue for moonlet formation in the outer edges of ring systems as the positive torque from the effect drives material out toward and away from the Roche limit.
Figure 3: The authors try to explain the current structure of Saturn’s A ring by initialising it with a Gaussian profile of optical thickness versus radius (black dot-dashed line) and evolving it for 81 million years under different effects. When viscous effects are included (blue dashed line), the ring spreads out, but it’s only when the eclipse–Yarkovsky (EY) effect is included (red line) that the model closely matches the observed data (grey line). [Zhou et al. 2026]
Original astrobite edited by Wasi Naqvi.
About the author, Ryan White:
I am a first-year PhD student at Macquarie University in Australia, working mainly on binary/multiple systems with massive stars (Wolf–Rayets in particular!). Outside of study, I’m probably drinking coffee, baking, reading, or going for a run. You can also find me procrastinating on Bluesky @astroryan.bsky.social.
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Giovanni Cassini was born in Perinaldo, in what is now Italy, on June 8, 1625. Early work on Jupiter and Mars’ rotational periods and the positions of Jupiter’s satellites led to an invitation to Paris and the Academie des Sciences by King Louis XIV; he became director of the Observatorie de Paris in 1671, andContinue reading "June 8, 1625: The birth of Giovanni Cassini"
The post June 8, 1625: The birth of Giovanni Cassini appeared first on Astronomy Magazine.
You wouldn't want to drink from this 2,000-year-old vintage though.
New observatories and spacecraft missions are probing environments in our solar system that could potentially host life but have long remained hidden. Icy moons like Saturn’s Enceladus and Jupiter’s Europa likely contain oceans beneath frozen outer shells. But a layer of ice prohibits space probes from sampling them directly. Exploring these icy moons is almost forensic: Their surfaces keep aContinue reading "Scientists used a method from ecology to identify whether icy moons could hold conditions for life"
The post Scientists used a method from ecology to identify whether icy moons could hold conditions for life appeared first on Astronomy Magazine.
Using spectral data from the Near-Infrared Spectrograph (NIRSpec) onboard the NASA/ESA/CSA James Webb Space Telescope, astronomers analyzed the atmosphere of TOI-199b, a distant Saturn-mass world that is neither frozen nor scorching hot.
The post Webb Detects Methane in Atmosphere of Exo-Saturn TOI-199b appeared first on Sci.News: Breaking Science News.
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