NASA spacecraft tracks comet SWAN in incredible 40-day timelapse — and even glimpses interstellar invader 3I/ATLAS (video)

Comets are famous for making brief, dramatic appearances in our skies, but one icy wanderer just received an unprecedented level of attention from one of NASA's newest spacecraft.

For nearly 40 days, NASA's PUNCH mission imaged the recently-discovered Comet C/2025 R2 (SWAN) every four minutes as it drifted through the inner solar system. That near-continuous stare "may be the longest any comet has been tracked" with such a frequency, according to a recent NASA announcement.

"Other comets have been tracked at once-per-day cadence for years," Craig DeForest, the principal investigator for the PUNCH mission at the Southwest Research Institute in Colorado, said in the statement. "What's new here is the few-minute cadence of observation."

The video above stitches together hundreds of PUNCH images taken from Aug. 25 to Oct. 2, showing the comet gliding 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.

Comet C/2025 R2 (SWAN) was first spotted in September by Ukrainian amateur astronomer Vladimir Bezugly, who noticed the icy visitor a bright blob close to the sun while scanning publicly available images from the sun-watching Solar and Heliospheric Observatory (SOHO). Just a day after its discovery, the comet reached perihelion, its closest point to the sun, passing at a distance of 46.74 million miles (75.20 million km) of our star.

Early images had revealed the comet’s bluish-green coma, created as the sun's heat vaporized the comet's ices in a process called sublimation. 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 now-famous interstellar visitor 3I/ATLAS. In the PUNCH time-lapse below, 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," the NASA statement noted.

Comet tails act as natural tracers of the solar wind, a continuous stream of charged particles flowing outward from the sun and shaping the space environment throughout the solar system.

"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," Gina DiBraccio, a heliophysicist and acting director of the Solar System Exploration Division at NASA's Goddard Space Flight Center in Maryland, said in the same statement.

"We use these same tools to track and analyze how space weather impacts our astronauts, our spacecraft, and our technology here on Earth."

In late October, the comet made its closest approach to Earth at 25.10 million miles (40.38 million km), putting it on the cusp of naked-eye visibility and easily within reach of binoculars and small telescopes.