From August to October, NASA’s PUNCH (Polarimeter to Unify the Corona and Heliosphere) mission tracked comet 2025 R2 (SWAN) — one of the thousands of comets discovered in images from the SOHO (Solar and Heliospheric Observatory) spacecraft, a joint mission between NASA and ESA (European Space Agency) that launched 30 years ago Tuesday.
Capturing a new image of the comet every few minutes, PUNCH’s observations may be the longest any comet has been tracked with such frequency, says the mission’s principal investigator, Craig DeForest of the Southwest Research Institute in Boulder, Colorado.
“Other comets have been tracked at once-per-day cadence for years,” DeForest said. “What’s new here is the few-minute cadence of observation.”
Comet 2025 R2 (SWAN) was first spotted by Ukrainian amateur astronomer Vladimir Bezugly on Sept. 11 in images taken by the SWAN (Solar Wind Anisotropies) instrument aboard SOHO. Over 5,000 comets have been discovered — many by citizen scientists — in SOHO images over its three decades of operation.
After comet SWAN’s discovery, scientists looked to see whether PUNCH had also spotted the comet and found it in PUNCH images taken as early as Aug. 7. Comet SWAN continued to appear in PUNCH’s field of view until early October, with the mission capturing a new image of it every four minutes through Oct. 5.
Over that time, PUNCH watched the comet’s tail grow, shrink, and flicker under the influence of the solar wind, a never-ending stream of particles flowing outward from the Sun. The PUNCH mission is designed to study how the solar wind travels out from the S …