To Mercury By Way Of Slinky Crescent

Use the young moon to help you find Mercury tonight (March 29). Created with Stellarium

Catch any northern lights last night? It wasn’t easy. A low glow and a few faint rays appeared in the northern sky early just after the end of evening twilight. I also saw some glow early this morning just before the start of dawn. Forecasts still call for a G1 or minor geomagnetic storm (Kp=5) this early evening before activity drops off. Thank you, coronal hole, for sponsoring these nightly treats!

Mercury is the smallest planet (just 3,032 miles across or 1.4 times the size of the moon) and orbits closest to the sun. One year on the planet lasts just 88 days. Credit: NASA

Yesterday, you may have spotted the return of the space station while out waiting for aurora. Tonight, it’ll swing by again, and you’ll have a great opportunity to catch the planet Mercury during its best evening appearance of the year for northern hemisphere skywatchers. The planet looks like a brightish star shining all by itself about 10° high or one fist above the western horizon 40-45 minutes after sunset.

What makes tonight special is that the beautiful-in-its-own-right moon, a skinny 2-day-old crescent, will shine one fist or 10° to the left of the planet. How convenient is that? Find the moon, find Mercury. So easy.

This photo of Mercury was taken by NASA’s orbiting MESSENGER space probe. The prominent rayed crater at center right is Debussy, named for French composer Claude Debussy. It’s 53 miles (85 km) across.  The average temperature on the sunny side of Mercury is 800° F, but it dips down to 290° below zero on the night side. With no atmosphere to speak of and no water to retain daytime heat, temperatures get frigid. The planet also rotates very slowly — one spin takes 176 days, Mercury’s day is twice the length of its year! Credit: NASA

Mercury will remain nicely placed for viewing for another week and a half before fading and dropping back toward the sun. The planet is that friend you wish would stay longer but unfortunately has business to attend to. The moon climbs higher each night, the crescent thickens, transforms to half — a cycle that never tires the eyes.