Mars Plays Tag With A Star Cluster

August 27, 2009

I hope you had a chance to see two of the moons of Jupiter cast their shadows on the face of the giant planet last night. I fought sleep and took my telescope outside to catch the show, and it did not disappoint. Even in my little 4-inch refractor, I could easily see the shadows of Europa and Ganymede. And I saw a third small dark spot I’ve yet to explain. Did anyone else see that third spot? Whatever it was, it was all a lovely sight.

There are more cosmic rendezvous to come this week. On Saturday morning, Mars plays tag with the lovely open cluster M35 in Gemini just before dawn.

M35 is one of the prettiest open star clusters in the sky, and it will make a fine spectacle with Mars in the same field of view of a low-power telescope or binoculars.

This part of the sky also marks the position of the summer solstice, the spot where the sun sits at its most northern excursion above the celestial equator on the first day of summer in the northern hemisphere (and winter in the south). The Sun has moved eastward since then of course, and M35 rises earlier each night with the rest of the northern winter constellations. The summers seem to pass faster each year, do they not?

Also, not far from M35, as recounted on p. 26 of Stargazing for Beginners, is the spot where William Herschel discovered the planet Uranus in 1781, and “at one stroke doubled the breadth of the sun’s dominions”. This part of the sky is rich with stars, where Gemini dips its feet in the stream of the winter Milky Way.

A similar event happens again just before dawn on September 1 and 2. That’s when the brilliant Venus lies a degree away from the ancient open star cluster M44 in the constellation Cancer. While M44 is less impressive than M35, Venus is most certainly much brighter than Mars.

If you’re an early riser, try to see for yourself these two splendid conjunctions of bright planets and star clusters in the pre-dawn sky.

Posted in Celestial Objects, Solar System Observing