PUNCH tracks a new comet: C2025 R2 (SWAN)
This is a PUNCH Science Nugget
PUNCH detected comet SWAN weeks before its discovery last week (11-Sep-2025). Tracking the comet is a warmup for tracking the upcoming 3I interstellar comet, which will enter the PUNCH FOV this weekend (21-Sep). Where the comet appears as a point, its astronomical magnitude is shown at lower right of the panel. Some other objects are labeled too.
Last week, astronomers announced a new comet, designated C/2025 R2 (SWAN), that was discovered in Lyman-α images from the SOHO spacecraft. Since mid-August, PUNCH has been observing this comet, along with every other object within 45° of the Sun. PUNCH collects data at a 4-minute cadence in polarized light and at an 8-minute cadence in unpolarized light.
We have created a montage showing once-per-day close-up frames, highlighting the comet’s appearance. To form its “virtual instrument”, PUNCH combines and calibrates data from four separate spacecraft. The included starfield close-ups demonstrate that our data pipeline is functioning well, as the Science Operations Center (SOC) team continues to refine it.
PUNCH’s resolution is similar to that of the human eye, but it is far more sensitive. In a single image, PUNCH can detect small, bright objects that are up to 100 times fainter than the faintest star visible to the naked eye under ideal conditions (astronomical magnitude 10.5+).
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