Astro Bob: Gossamer moon joins Mercury on May 2
The two-day-old crescent lines up with Mercury and the Pleiades Monday night. A bright comet was supposed to join the scene, but it recently disintegrated.
If you haven't seen Mercury yet, it's fading. Why not take advantage of Monday night's moon for a helping hand? The two-day-old crescent will stand about 4.5 degrees above and left of the elusive planet. Point your binoculars at the moon (a gorgeous sight in itself), focus sharply, then slide about one binocular field of view to the lower right. You should see a single bright star — that's what you're after!
In early May, the planet shines about magnitude 0.8. Although it's growing in size as it gets closer to the Earth, Mercury's also getting fainter because its phase has waned from full to crescent. Through a small telescope it will appear 27% illuminated Monday night. The moon is much thinner — only about 5% lit. Further down in the sky below Mercury you'll find the Pleiades. All three look best in binoculars.
I wanted to bring you good news about Comet PanSTARRS. Had it survived its close brush with the sun April 21 at a distance of 26.7 million miles (43 million kilometers), it might have been bright enough to see in binoculars at around magnitude 5.
Instead, it appears to have lost its head. Astronomers have detected only a faint, glowing cloud of debris — a sure sign that it has begun to disintegrate. Gravitational tides from the sun, coupled with intense heating, were too much for the friable object. Comet experts weren't particularly surprised because PanSTARRS was small to begin with. Still, it's disappointing news.
You win some, you lose some. As Comet PanSTARRS arcs farther from the sun in the coming nights, I'll try to spot it anyway. Even crumbling comets are fascinating to watch. Everything is a process, and the more steps of the process we see, however faint or obscure, the better our understanding of the natural phenomenon.
"Astro" Bob King is a freelance writer for the Duluth News Tribune.