A comet has come under unprecedented scrutiny after NASA managed to capture images of SWAN every 4 minutes for 40 days, even catching a glimpse of the mysterious interstellar visitor 3I/ATLAS
Comets tend to race through our skies too fast for us to study them well, but a NASA spacecraft has achieved a unique feat with Comet C/2025 R2 (SWAN), following it closely as it drifted through the solar system for over a month.
SWAN was spotted in September when Ukrainian amateur astronomer Vladimir Bezugly noticed the icy visitor as a bright blob near the sun. The comet came closest to Earth in late October, just 25.10 million miles (40.38 million km) away, almost visible with the naked eye and easily seen with binoculars or a small telescope.
NASA‘s PUNCH mission tracked the new comet on its journey, snapping a pic every four minutes for 40 days. That near-continuous stare “may be the longest any comet has been tracked” with such frequency, said NASA. PUNCH is a set of four microsatellites studying the edge of the sun.
“Other comets have been tracked at once-per-day cadence for years,” said Craig DeForest, the principal investigator for the PUNCH mission at the Southwest Research Institute in Colorado. “What’s new here is the few-minute cadence of observation.”
Just a day after its discovery, when Bezugly spotted it in images from the sun-watching Solar and Heliospheric Observatory (SOHO), the comet reached perihelion, its closest point to the sun, passing at a distance of 46.74 million miles (75.20 million km).
A video gathers hundreds of PUNCH images from August 25 to October 2 to show the comet glide between two bright objects: Mars at the top and the star Spica in the constellation of Virgo at the bottom. Because the images were not fully processed before being combined, boundaries between individual snaps remain visible as thin black seams, the statement read.
Early images revealed the comet’s bluish-green coma, created as the sun‘s heat vaporized the comet’s ices in a process called sublimation. The gas and dust released were swept backward by the solar wind, forming the glowing tail captured in various images.
By mid-September, the coma had taken on an unusual triangular “hammerhead” shape, a distortion astronomers often link to a fragmenting nucleus, as outgassing from multiple pieces can stretch a normally round coma into a lopsided form.
At the same time, Comet C/2025 R2 (SWAN) happened to share the same swath of sky with the notorious interstellar visitor 3I/ATLAS. In the PUNCH time-lapse, 3I/ATLAS appears briefly near the end of the sequence, zipping left to right beneath SWAN.
As Comet C/2025 R2 (SWAN) moves leftward in the images, its tail is pushed in the same direction by the solar wind, making the comet appear to drift “backward”, said NASA.
Comet tails act as natural tracers of the solar wind, a continuous stream of charged particles flowing away from the sun.
“Watching the sun’s effects from multiple vantage points — and with different types of instruments — is what gives us a complete picture of the space environment,” said Gina DiBraccio, a heliophysicist and acting director of the Solar System Exploration Division at NASA’s Goddard Space Flight Center in Maryland.
“We use these same tools to track and analyse how space weather impacts our astronauts, our spacecraft, and our technology here on Earth.”
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