Comet 12P/Pons-Brooks and (on the right) M33, the Triangulum Galaxy, from March 21. Through binoculars, the comet was a barely-visible fuzzy blob; the photo above, with 27 minutes of exposure time, reveals a lot more than the eye could see. Pons-Brooks will be in the sky for a couple of months to come but will be invisible from North America, setting before it gets dark, after mid-April. It's expected to reach peak brightness around April 21 and will be closest to the Earth on June 2, but visible then only from the Southern hemisphere. Click the picture above to see more portraits of this celestial visitor.
Pons-Brooks, which comes around every 71 years, is named after the two most prolific comet-hunters of the 1800s, Jean-Louis Pons and William Robert Brooks, who independently spotted the comet on successive visitations in 1812 and 1883. Once its orbit was calculated, it was recognized as an unnamed comet that had also been observed in the 1300s and 1400s.
The arrangement of objects painted on the sky here gives little hint of the depth involved. Pons-Brooks was 150 million miles away when this picture was taken, 50% farther away than the Sun. It takes light 13 minutes to travel this distance, so the comet was 13 light-minutes away—which, in more familiar terms, is 0.000026 light years. The bright star on the left, 91 Piscium, is 350 light years away, and faint stars in the photo might be a few thousand light years away. M33, in contrast, is 2.7 million light years away. Pons-Brooks is pretty far away in this picture, but M33 is 100 billion times farther away than the comet. It's kind of like the galaxy is the Moon, the stars are bugs on your windshield . . . and the comet is a smear on your contact lens.
