NASA’s Hubble Detects First-Ever Spin Reversal of Tiny Comet - UNIVERSE

Astronomers using NASA’s Hubble Space Telescope have found evidence that the spinning of a small comet slowed and then reversed its direction of rotation, offering a dramatic example of how volatile activity can affect the spin and physical evolution of small bodies in the solar system. This is the first time researchers have observed evidence of a comet reversing its spin. 

The object, comet 41P/Tuttle-Giacobini-Kresák, or 41P for short, likely originated in the Kuiper Belt, and was flung into its current trajectory by Jupiter’s gravity, now visiting the inner solar system every 5.4 years.

After its 2017 close passage around the Sun, scientists found that comet 41P experienced a dramatic slowdown in its rotation. Data from NASA’s Neil Gehrels Swift Observatory in May 2017 showed the object was spinning three times more slowly than it had in March 2017 when it was observed by the Discovery Channel Telescope at Lowell Observatory in Arizona.

A new analysis of follow-up Hubble observations has shown the spin of this comet took an even more unusual turn.

Hubble images from December 2017 detected the comet spinning much faster again, with a period of approximately 14 hours, compared to the 46 to 60 hours measured by Swift. The simplest explanation, researchers say, is that the comet continued slowing until it almost stopped, and was then forced to spin in the near-opposite direction by outgassing jets on its surface.

The science paper detailing this finding published Thursday in The Astronomical Journal.

This artist’s concept depicts comet 41P, a tiny Jupiter-family comet, as it approached the Sun and frozen gases began to sublimate and shoot material off into space.

Illustration: NASA, ESA, CSA, Ralf Crawford (STScI)

Small, temperamental nucleus

Hubble also constrains the size of the comet’s nucleus, measuring it at around 0.6 miles across (about a kilometer), or about three times the height of the Eiffel Tower. 

This is especially small for a comet, making it easy to torque, or twist.

As a comet approaches the Sun, heat causes frozen ices to sublimate, venting material into space. 

“Jets of gas streaming off the surface can act like small thrusters,” said paper author David Jewitt of the University of California at Los Angeles. “If those jets are unevenly distributed, they can dramatically change how a comet, especially a small one, rotates.”

The comet was originally spinning in one direction, but gas jets pushing against that motion gradually slowed it down. Because the jets kept pushing, they ultimately caused the comet to start rotating in the opposite direction.

“It’s like pushing a merry-go-round,” said Jewitt. “If it’s turning in one direction, and then you push against that, you can slow it and reverse it.”

Evidence of rapid evolution

The study also shows that the comet’s overall activity has declined significantly since earlier returns. During its 2001 perihelion passage, 41P was unusually active for its size. By 2017, its gas production had decreased by roughly an order of magnitude.

This change suggests that the comet’s surface may be evolving quickly, possibly as near-surface volatile materials become depleted or covered by insulating dust layers.

Most changes in comet structure occur over centuries or longer. The rapid rotational shifts observed in comet 41P provide a rare opportunity to witness evolutionary processes unfolding on a human timescale. 

Modeling based on the measured torques and mass loss rates suggest that continued rotational changes could eventually lead to structural instability for comet 41P. If a comet spins too rapidly, centrifugal forces can overcome its weak gravity and strength, potentially causing fragmentation or even disintegration.

“I expect this nucleus will very quickly self-destruct,” said Jewitt.

Yet, comet 41P has likely occupied its present orbit for roughly 1,500 years. 

This artist’s concept depicts comet 41P as it approached the Sun and frozen gases began to sublimate off the comet’s surface. This animation only depicts one jet, but this comet may have multiple streams of material ejecting into space. This jet is pushing against the comet’s spin, then forcing it in the opposite direction. Small fragments of the comet are also shown spewing into space.

Animation: NASA, ESA, CSA, Ralf Crawford (STScI)

Archival find

Hubble has been collecting imaging and spectroscopic data from across the cosmos for over 35 years, and all of those observations are available in the Mikulski Archive for Space Telescopes, a central repository for data from more than a dozen astronomical missions, including Hubble.

Jewitt found these observations while browsing the archive, and realized they were yet-to-be analyzed. 

By making NASA’s science data open to all, observations made years, or even decades ago, can be revisited to answer new scientific questions. In many cases, scientists continue to make discoveries not just with new observations, but by mining the archive built over decades of space exploration.  

Source: NASA's Hubble Detects First-Ever Spin Reversal of Tiny Comet - NASA Science

North Sea wind farms may be reshaping sediment flows by 1.5 million tons a year - Earth - Earth Sciences - Environment

Credit: Unsplash/CC0 Public Domain

Offshore wind farms are an important pillar of the European Union's strategy for renewable energy—by 2050, the EU aims to increase capacity in the North Sea more than tenfold. A new study by the Helmholtz-Zentrum Hereon shows that the expansion of wind farms can alter the natural transport and deposition of sediments on a large scale and over the long term. The German Bight is particularly affected. The researchers have published their findings in the journal Nature Communications Earth & Environment.

Redistribution of sediment and carbon

Suspended particles are constantly being moved around the North Sea, originating from the stirring-up of local seabed sediments by waves and currents, as well as from material carried in from the Atlantic Ocean through the English Channel, or from rivers. This material travels through repeated cycles of settling and resuspension until it finally accumulates as mud in calmer areas where currents are weak.

Offshore wind turbines are barriers in the air and in the water. They influence the stratification of the sea into warmer and colder water layers and slow down currents over a wide area throughout the North Sea. These factors determine how mud and organic particles are transported through the ocean and where they deposit. Hereon researchers have now discovered that existing wind farms in the North Sea are already causing a significant spatial redistribution of these sediments. This affects up to 1.5 million tons of mud annually—and the carbon bound within it.

Sediments consist in part of the remains of dead marine animals and plants. This organic material contains particulate organic carbon (POC), which sinks to the seafloor with the particles and can be stored there for centuries. The seafloor is therefore referred to as a carbon sink. Oceans thus make an important contribution to global carbon sequestration and help mitigate climate change.

German Bight is particularly affected

The researchers used a new computer model that, for the first time, combines calculations of the atmosphere, waves, currents, and sediment transport in the North Sea. The data is based on previous Hereon studies on the impact of offshore wind turbines on air and ocean currents.

"Our simulations suggest that these amounts will accumulate increasingly over the coming decades as offshore wind farms expand. This could affect the long-term functioning of the ecosystem and carbon storage in the North Sea," says the study's lead author, Jiayue Chen, from the Hereon Institute of Coastal Systems—Analysis and Modeling. Notably, about 52% of the total sediment redistribution occurs in the German Bight. "This highlights this region as particularly affected."

As a next step, the researchers plan to investigate how these changes specifically affect particularly sensitive coastal areas like the Wadden Sea, which relies on a continuous supply of sediment to compensate for rising sea levels. They are also examining how these effects influence the role of the ocean as a carbon sink.

"With an improved understanding of sediment distribution and carbon storage in the North Sea, we can assess long-term risks to coastal stability, navigational safety in shipping, and the functioning of ecosystems in the German Bight," says Chen. "Our findings provide a valuable foundation for the sustainable expansion of offshore wind energy and help decision-makers in politics, business, and industry to plan new wind farms in an environmentally friendly way." 

Provided by Helmholtz Association of German Research Centres  

by Torsten Fischer, Helmholtz Association of German Research Centres

edited by Lisa Lock, reviewed by Robert Egan 

Source: North Sea wind farms may be reshaping sediment flows by 1.5 million tons a year 

Can AI understand literature? Researchers put it to the test - Computer Sciences - Machine learning & AI

Credit: Pixabay/CC0 Public Domain

Even with all the recent advances in the ability of large language models (like ChatGPT) to help us think, research, summarize, and learn complex and technical texts, how do they fare in understanding storytelling and literature? These questions around interpretive nuance remain.

Columbia Engineering researchers are addressing these issues through a novel, ethically grounded evaluation framework. Their work, published on the arXiv preprint server, was recognized with the Best Paper Award in 2025 at the Transactions of the Association of Computational Linguistics (TACL), highlighting its methodological rigor and contribution to the field.

"Before we can place real trust in LLMs' analytical abilities, we need careful evidence of what they can and cannot do," said Kathleen McKeown, the Henry and Gertrude Rothschild Professor of Computer Science at Columbia Engineering. She and Associate Professor Lydia Chilton led the team that worked on this research project.

"If LLMs are to serve as tools for human inquiry, we must first understand the depth and the limits of their analytical capabilities, including in domains like narrative and literature."

A new evaluation framework

The study evaluated the performance of state-of-the-art language models—GPT-4, Claude-2.1, and LLaMA-2-70B—on the task of summarizing short fiction. Unlike many prior evaluations that relied on publicly available texts that may be included in model training data, this project introduced a controlled, original dataset.

The researchers collaborated directly with published authors, who contributed their previously unpublished short stories. These authors then assessed the quality of the summaries generated by the models.

Using both quantitative and qualitative methods informed by narrative theory, the analysis revealed that all three models generated faithfulness errors in over 50% of cases and consistently struggled with specificity and the interpretation of complex subtext or nonlinear narrative structures.

"Models can seem like they understand a story, but their outputs are ultimately unpredictable because they rely on probabilities," said Melanie Subbiah, the lead author of the paper, and a sixth-year Ph.D. student at Columbia in the McKeown lab.

"A trained human literary analyst would produce consistently strong insights, but even the best model is only about 50/50—essentially a coin flip—in giving a reliable analysis for any given story."

The findings underscore the limitations of current LLMs in intellectual and creative contexts that demand close reading and interpretive sensitivity.

While such systems can serve as useful tools, the researchers caution against relying on them for nuanced literary analysis or other tasks requiring deep contextual understanding. Subbiah believes their work "reinforces the value of human-centered, expert-informed evaluation."

Beyond the empirical findings

Ethical considerations were integral to the study. Participating authors were provided full transparency regarding the use of their work and feedback, were compensated for their contributions, and had their intellectual property carefully protected. The project deliberately focused on narrative understanding and analysis rather than text generation, reflecting "a commitment to responsible and respectful research practices."

The project presents a novel methodology for evaluating language models on content that is guaranteed to be absent from their training data.

By working directly with domain experts, in this case, professional authors, the study demonstrates an approach that enables more reliable assessment of a model's interpretive and analytical capabilities. This framework offers a replicable model for future research on narrative understanding and other forms of expert-driven evaluation.

"The hope is that expert human insight will guide how we evaluate LLMs, keeping people at the center of technology development," said Subbiah. 

Provided by Columbia University 

by Bernadette O. Young, Columbia University

edited by Sadie Harley, reviewed by Robert Egan 

Source: Can AI understand literature? Researchers put it to the test

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Watch the Skies - It’s Fireball Season! Answering Your Meteor Questions

Sometimes, space comes to us! Texas, Ohio, California, Michigan – these are just a few of the states where folks have recently seen the skies illuminate with bright streaks of light. For those lucky enough to spot a fireball, or “shooting star,” the moment can feel awe-inspiring and exciting, and many of you have been sharing stunning visuals from these events. At NASA, where watching the skies is part of our everyday mission, we’ve noticed the excitement, and we’re here to answer some of the most common questions we’re seeing about these celestial celebrities. 

A very bright daytime fireball was observed by witnesses from the northeast U.S. and Canada the morning of March 17, 2026. The fireball – caused by a small asteroid nearly 6 feet in diameter and weighing about 7 tons – moved southeast at 45,000 mph before fragmenting over Valley City. The fragments continued on to the south, producing meteorites in the vicinity of Medina County, Ohio.

NOAA 

There seem to be a lot of fireballs lighting up the sky lately – is this unusual?  

While it may seem like meteor reports and sightings have been more frequent recently, it is not out of the ordinary. In the northern hemisphere, we’re in peak “fireball season.” From February through April, the appearance rate of these very bright meteors can increase by as much as 10% to 30%, especially around the weeks of the March equinox. Exactly why is not known. Some astronomers think the Earth passes through more large debris at this time of year, causing an uptick in fireball sightings. 

Another likely reason it may feel like meteor sightings are increasing is that more of us have cameras at the ready — from smartphones to doorbell cameras to dashboard cameras — making it easier than ever to capture and share these fleeting cosmic events when they happen. 

How common are meteor sightings on Earth? 

Meteors are actually quite common. – They occur all the time, and fireballs can be seen on any given night. But they often occur over the ocean or unpopulated areas with no witnesses, or during the daytime, making them difficult to spot. Viewers who catch a clear view of one in the dark skies above are treated to a spectacular sky show – but one that is hardly rare.  

Meteors, meteoroids, meteorites … what’s the difference?  

• A meteoroid is a small rock or particle traveling through space, usually a piece of a comet or asteroid.
• A meteor refers to the streak of light in the sky that appears when a meteoroid enters Earth’s atmosphere and disintegrates.
• A meteor shower occurs when meteoroids that have a common origin (like debris from a comet) and very similar orbits enter the atmosphere.
• A meteorite is a piece of space rock that survives the trip through the atmosphere and lands on the ground. 
• A fireball – the brightest of them all – is a meteor that shines brighter than the planet Venus. They are caused by particles that are larger than the ones producing “normal” meteors. Sometimes fireballs are called bolides – the words are interchangeable and refer to the same phenomenon.
• Read more about these and other space rocks. 

How does NASA watch for meteors? Can NASA predict when one will appear?  

NASA watches the skies for objects of all sizes with a network of specialized telescopes across the United States. Its planetary defense network, for example, is specifically tasked by our government to find and track asteroids that are 140 meters and larger. These objects are big enough to penetrate Earth’s atmosphere and could cause widespread damage. Meteoroids are much smaller. Almost impossible to track in space, they cannot survive passage through the atmosphere intact and pose no real hazard to ground-dwellers. 

Where do these meteors and meteorites come from?  

Most meteorites that make it to the ground here on Earth are pieces of small asteroids (or big meteoroids) that have fragmented on their way through the atmosphere. Through laboratory tests, scientists can determine the meteorite type, how long it was in space and its origin. Most meteorites come from the asteroid belt between Mars and Jupiter, but occasionally we will get some that clearly came from the Moon or Mars. These are extremely rare! 

Why do some meteors make a “boom” noise? 

Some meteors you can hear! Meteors travel through Earth’s atmosphere at hypersonic speeds – far exceeding the speed of sound. This immense speed creates a wave of pressure which, combined with the friction and heat that can cause the rock to fragment, can result in a loud, explosive sound, often called a sonic boom, that can be heard on the ground. Additionally, the fragmentation of the fireball unleashes large amounts of energy, which also generates a pressure wave that can produce a very loud boom, even shaking houses. 

So, the next time you catch a streak of light traveling across the night sky, you’ll know more about how to identify what you’re looking at. As we continue on through fireball season, keep your cameras at the ready, your curiosity high, and your eyes on the skies!    

Source: It’s Fireball Season! Answering Your Meteor Questions  - NASA

Building facade solar panels on outside walls can generate power while cutting cooling costs - Energy & Green Tech

Spatial and temporal characteristics of FIPV generation in meeting building electricity demand. Credit: Nature Climate Change (2026). DOI: 10.1038/s41558-026-02606-z

A team of Chinese researchers has modeled the potential global benefits of installing solar panels on outside building walls, a concept known as facade-integrated photovoltaics (FIPV). They found that solar panels installed on building facades not only generate substantial electricity but also reduce cooling demand, thereby reducing carbon emissions and improving urban climate adaptation.

The study, conducted by Prof. Yao Ling's team at the Institute of Geographic Sciences and Natural Resources Research of the Chinese Academy of Sciences, is published in Nature Climate Change.

As climate change intensifies heat exposure and extreme weather and increases electricity demand in cities, climate-resilient urban development has become a global priority. Buildings account for a large share of urban energy use and emissions. Solar photovoltaics provide a partial solution but are mainly deployed on rooftops, leaving vast vertical building surfaces largely underused.

In this study, the researchers developed a global model to quantify the energy and climate benefits of FIPV.

Using information on building geometry, exposed area, and meteorological data, the researchers simulated the electricity generation potential of FIPV worldwide. They then evaluated the influence of FIPV on buildings' heating and cooling demand. In addition, they analyzed carbon mitigation and climate adaptation benefits by linking generation–demand interactions on an hourly basis.

Assuming the most plausible deployment scenario, the researchers concluded that FIPV could generate about 732.5 TWh of electricity annually worldwide and reduce building electricity demand by 8.1% on average. They also showed that these combined benefits could translate into meaningful economic and climate gains, with more than 80% of simulated districts showing reductions in net lifetime electricity expenditures.

The study estimated that the reduction in cumulative carbon emissions could reach 37.7 Gt CO₂ if FIPV adoption reached its maximum potential by mid-century. To achieve this goal, however, targeted policies, adaptive planning, and locally informed strategies would be required due to variations in urban morphology, climate conditions, building characteristics, and socioeconomic circumstances. 

Provided by Chinese Academy of Sciences 

by Chinese Academy of Sciences

edited by Gaby Clark, reviewed by Robert Egan 

Source: Building facade solar panels on outside walls can generate power while cutting cooling costs 

Satellite Spots a Spawn - NASA Earth Observatory - EARTH

Water along the coast of Vancouver Island is brightened by a herring spawn in this image acquired on February 19, 2026, by the OLI (Operational Land Imager) on Landsat 9.

NASA Earth Observatory/Lauren Dauphin

Spawning season has sprung for Pacific herring (Clupea pallasii) in the waters off British Columbia, Canada. From mid-February through early May each year, thousands of the small, silvery fish congregate in shallow coastal areas around Vancouver Island and create a spectacle sometimes visible to satellites.

Sheltered waters in Barkley Sound, on the southwestern side of Vancouver Island, are regular sites for spawn events. On February 19, 2026, the Landsat 9 satellite caught a glimpse of early-season activity underway along the shore near Forbes Island. In these events, female herring produce eggs that stick to a variety of materials, from kelp and seagrass to rock surfaces. Males release a sperm-containing fluid called milt into the water, giving it a cloudy green or turquoise look.

A herring spawn clouds the water along the coast of Vancouver Island near the village of Salmon Beach on February 19, 2026.

Photo by Ryan Cutler

Spawns near Forbes Island have been observed most years since the 1970s, according to Fisheries and Oceans Canada (DFO) records. “Herrings prefer spawning locations that are more protected, have rocky substrate, and allow them to select areas with reduced salinity,” said Jessica Moffatt, biologist with the Island Marine Aquatic Working Group (IMAWG), which works to strengthen First Nations fisheries through traditional knowledge, modern science, and management guidance. “Barkley Sound hits the sweet spot” in many of these regards, she said, adding that collective memory, predation pressure, and other factors also play a role in spawn size and location.

Spawning events last from several hours to several days. At Forbes Island in 2026, local observers saw that fish were staging in the area by February 13 (schools can arrive up to two weeks before spawning, Moffatt noted), and activity was reported to IMAWG from February 19 to February 21.

Along with changes in water color, spawns often come with increased wildlife presence, which can include whales and sea lions swimming nearby and eagles, wolves, and bears lurking on shore. After spawning, the fish will migrate back to summer feeding areas in deeper, more nutrient-rich waters, sometimes sticking with their same large school for several years.

A herring spawn event near Forbes Island in Barkley Sound brightens nearshore waters on February 19, 2026.

Photo by Ryan Cutler

Records of spawn activity have historically been constrained by the timing of aerial and dive surveys, the availability of reports from remote locations, and fisheries priorities. But observations by satellites, including Landsat, can help monitor herring activity over larger areas and longer periods of time. Researchers at the University of Victoria in Canada have used decades of satellite observations to augment historical spawn records and develop methods to streamline future detections.

Herring and their roe are valuable both as a cultural food source and harvest practice by First Nations and for British Columbia’s commercial fisheries. As a forage fish species, Pacific herring are vital to salmon and other marine life, and a fuller picture of the locations of spawning areas could provide clues about changes in the marine ecosystem.

NASA Earth Observatory images by Lauren Dauphin, using Landsat data from the U.S. Geological Survey. Photos by Ryan Cutler. Story by Lindsey Doermann. 

Source: Satellite Spots a Spawn - NASA Science