Delicious Comet Lemmon-cluster Pairing; Moon Greets 7 Sisters At Dawn

Comet C/2012 F6 Lemmon cruises by the open cluster NGC 7789 in Cassiopeia last night July 2, 2013. Click to supersize. Credit: Damian Peach

It’s a beautiful thing when two completely different celestial objects pair up. Seen side by side, we can appreciate the unique qualities of each by contrast with the other. Two fine examples stand out this week.

Comet Lemmon, which has been chugging across the sky for months, pulled up alongside the rich star cluster NGC 7789 this week. The cluster is sandbox of pinpoint stars tucked off to one side of the W of Cassiopeia. I’ve been watching the scene the past two nights through the telescope. Last night both comet and cluster shared the same field of view.

Compared to the pointillistic stellar swarm, the comet looked ghostly and ethereal. And to think that one of these belongs to our solar system and the other resides on the far edge of the galaxy at a whopping 7,600 light years from Earth … well, it simply jazzes the brain cells. What can I say?

Then there’s composition to consider. Comets and the sun are made of virtually the same materials – hydrogen (frozen H2O in a comet’s case) and a dusting of carbon, nitrogen, oxygen, silicon and on and on. Yet comets are cold, relatively uncompressed dust. Not the sun. Put enough dust in one place and gravity will eventually crush it into a sphere hot enough to start its innards burning. A star is born. Interstellar dust left by earlier stellar generations is their common bond.

Watch the moon come up below the Pleiades star cluster tomorrow morning. The crescent will be only three days from new moon. This map shows the sky facing northeast at early dawn. Stellarium

Tomorrow morning we’ll see another auspicious duo. The waning lunar crescent rises at dawn below the Seven Sisters star cluster. Also known as the Pleiades (PLEE-uh-deez), the dipper-shaped group is more closely associated with the winter sky than the summer. In July it re-emerges during morning twilight, stalks the wee hours in August and looks down on earthlings from overhead on December evenings.

You can watch both moon and sisters with the naked eye, but binoculars will enhance the view. Next to the cluster, will the tweezers moon look closer to home than ever before? Take a look and see what you think.