Cometary surprises delight
COMETS ARE notoriously unpredictable. In 2023, that worked in our favor, with three particularly notable comets stealing attention.
The year opened with what we expected to be its best comet: C/2022 E3 (ZTF), which reached perihelion — the closest point to the Sun in its orbit — on Jan. 12. On Feb. 1, ZTF passed closest to Earth, coming within about 0.3 astronomical unit of our planet. (One astronomical unit, or AU, is the average Earth-Sun distance.) During its visit, ZTF ultimately reached magnitude 4.5 and developed a well-defined anti-tail seen in many photographs.
Magnitude 4.5 is also the brightness our next visitor, 12P/PonsBrooks, is expected to reach in April this year, weeks before perihelion. That’s when, as first noted by amateur astronomer Dave Weixelman, it will appear some 24.5° from the Sun during the total solar eclipse April 8.
But Pons-Brooks wasn’t willing to wait for fame. On July 20, 2023, observer Elek Tamás went looking for the then-magnitude 16.6 comet — and discovered an outburst had catapulted it to magnitude 11.6. By early October, the comet had faded only slightly — and underwent a second outburst Oct. 5, reaching roughly the same magnitude as in July. Both times, the comet displayed a unique “horned” or horseshoe shape, earning it the nickname “devil comet.” According to comet researcher Richard Miles (who spotted the second outburst), PonsBrooks has had similar flare-ups during past visits to the inner solar system. Perhaps it’s had yet another since this issue went to press!
Avid skywatchers already know we’ve saved the best for last: Comet ZTF was not 2023’s best. That title goes to C/2023 P1 (Nishimura), which burst onto the scene Aug. 12 when Japanese amateur astronomer Hideo Nishimura of Kakegawa, Japan, spotted it in Gemini, already at magnitude 10.4 and 1 AU from the Sun. Nishimura passed closest to Earth a month later, before rounding the Sun at a perihelion distance of just 0.23 AU on Sept. 17, peaking at an impressive magnitude 2.5. After perihelion, it disappeared from Northern Hemisphere skies and could only be picked up below the equator as it faded quickly on its way back to the outer solar system.
Its appearance was brief and it was never an easy naked-eye object due to its low elevation. Nonetheless, Nishimura was the definitive winner of 2023’s cometary crown.