COMET SEARCH

Second comet of the decade?

READY TO WITNESS a fantastic glowing sword standing straight up from the recently set Sun? Comet C/2021 O3 (PanSTARRS) could be it. Or it could instead dissolve suddenly in a whimper.

The night of May 2 could go down in history: In deepening twilight, Comet PanSTARRS sits photogenically a few degrees right of Mercury (magnitude 0.6), while the Pleiades star cluster (M45) sparkles between them and a thin crescent Moon full of earthshine smiles just off to the left. Plan for travel if you can. We will have three days’ notice that the performance is on. This is a rare opportunity.

Though PanSTARRS is fading after perihelion on April 21, beneficial geometry kicks in during early May. Dust lights up when we see it in the direction of the Sun. The forward scattering angle is at a minimum on the 4th, similar to what we saw with comets C/2006 P1 (McNaught) and C/1975 V1 (West). In the nights following, the main body shifts up and away into Perseus but the dust swings into alignment.

Ignore the waxing Moon to watch PanSTARRS as long as possible. It slowly fades into binocular range while climbing toward Polaris. On May 10, it passes the picturesque starfield of Perseus’ left arm, which contains the star cluster NGC 1528 and its compact neighbor NGC 1545. Give it a try anyway on the moonglow weekend of May 13 to 15, some 3° from Kemble’s Cascade and NGC 1502.

Although PanSTARRS probably won’t trigger the clickbait hype of media newsfeeds, don’t slip into “Oh, I’ll see it tomorrow” mode and miss out.

Catch Comet PanSTARRS May 2 near M45, the Moon, and Mercury. (The last two are not shown here — see page 32 for their relative positions that day.) Find updated finder charts for the latter half of May on Astronomy.com.