Astro Bob: Venus tiptoes by M35, the Gemini Cluster
With Venus as tour guide, skywatchers can spot a bright star cluster in Gemini. Although the recent aurora failed to show, another blast is on the way for May 10-11.
We always like it when the moon and bright planets help us find new things in the sky. For the next few nights Venus will perform that duty by guiding us to the open star cluster M35 in the constellation Gemini the twins. M35 is a loose assemblage of stars held together by their mutual gravitational attraction. Like a flock of migrating birds, the stars all "fly in formation" as they circle the galactic center.
The "M" in M35 refers to the 18th century French comet hunter Charles Messier. While searching for his favorite quarry (comets!) with his 4-inch refracting telescope he would often stumble across other objects. To avoid mistaking them for comets during future hunts he measured their positions, described their appearance and cataloged the lot. M35 is his 35th entry in a list of 110 deep-sky objects.
Every winter, when the cluster climbs high in the southern sky atop Orion, I stop by with my telescope to gawk. If the night sky is a traveling art show that passes through town every year, M35 is must-see masterpiece.
A sparkling sight in a telescope, the bunch is bright enough to pick out in 35mm or larger binoculars. I can track it down easily enough in my 8x40s when there's no moon around. The cluster looks like a fuzzy patch with a few stars twinkling through the mist — at first. The longer you gaze the more faint suns come into view and the richer its appearance becomes.
M35 is located in the foot of Castor, one of the Gemini twins, at a distance of nearly 3,000 light-years from Earth. The light we see tonight left the cluster around 1000 B.C. just as the Iron Age was getting underway and the world's population numbered about 50 million. It's now 8 billion.
Although it has the same apparent size as the full moon its true diameter is 11 light-years or about 66 trillion miles. That's half again the distance from Earth to the brilliant star Sirius. M35 is something of a youngster as well — it 400-plus members coalesced from massive cloud of dust and gas about 175 million years ago, when dinosaurs were a common sight on Earth.
To see M35 wait until it's fairly dark — near the end of twilight about 1 1/2 hours after sunset is a good time. Point your binoculars at Venus, carefully focus and then look below the planet in the same field of view for a small clutch of stars. If you spot the cluster you can add it to your Messier list. I'm betting you've all seen the most famous M-object of all, the Pleiades star cluster, also known as M45.
So what happened to that big aurora?
I was as disappointed as you were that the aurora was a no-show the night of May 7-8. There was activity but not at the predicted time. But hey, we have another shot. A coronal mass ejection from a May 7 solar flare is en route and expected to arrive the afternoon of Wednesday, May 10 and reverberate through the night. I've read various reports, but at least a G1 (minor) storm is expected with aurora visible from the northern states and Canada in the lower half of the northern sky. Moonrise happens after 2 a.m. on May 11 so no worries there. Watch my Facebook page for the latest prognostications.