I took a great walk in the woods yesterday. Many trees were still blanketed with snow from our Thanksgiving Day storm. As I kicked through the fluffy white clods, I thought of Comet Hartley 2 and its carbon dioxide-propelled geysers shooting out chunks of snow into outer space. Were they soft and airy like the stuff rubbing against my boots? Whatever the texture, you probably couldn’t build a snowman with Hartley 2 snow. In the cold, near-zero pressure environment of outer space, it would hardly make “good packing”.
This weekend the comet did a do-si-do between two very pretty binocular star clusters in the constellation of Puppis (PUP-is) the Stern located just east of the more familiar Canis Major the Greater Dog. We know Canis Major primarily through Sirius, the brightest star in the sky and one of the easiest to find. Shoot a line southward (to the left) of Orion’s Belt and you’ll hit Sirius straightaway. With the moon rising in the wee hours for the remainder of the week, you can see the two clusters – M46 and M47 – if you’re up and about at midnight or later. M47’s the brighter and visible to the naked eye from a dark sky location. It’s neighbor, M46, is about the same size but looks misty because it has far more fainter stars than bright ones. These side by side star clusters are two of the 110 objects in Charles Messier’s famous 18th century catalog of clusters, galaxies and nebulae – hence their “M” designations.
Comet Hartley 2 has been fading since earlier this fall and will require binoculars with an aperture or lens diameter of at least 50 mm to see. You can find your binocular’s aperture by looking on the barrel or near the focusing mechanism.Â For example, 7×50 indicates a magnification of seven times and an aperture of 50 mm or about 2-inches. The comet is now around 7th magnitude and looks like a dimly glowing patch in binoculars. Telescopes will still show its bright center or nucleus blazing away inside the larger, fainter coma. I’ve included a finding chart belwo suitable for both binocular and telescope users.