WHAT'S UP: See the Double Cluster near Cassiopeia

Oct 7, 2011


In antiquity, Cassiopeia was a queen, a queen sitting on her throne in the sky. To most people nowadays — perhaps we’re less sophisticated now — Cassiopeia looks like a giant “W.”

Cassiopeia and the stars near it never rise or set for observers in the mid-latitudes and farther north. Stars that are close enough to the North Star so they don’t dip low enough to set below the northern stretches of the horizon are called circumpolar. The beauty of circumpolar objects is that they are visible anytime of year.

This time of year in the evening, a couple of hours after sunset, Cassiopeia sits about halfway between the northeast point on the horizon and the point directly overhead.

Each of the five vertices of the Cassiopeia “W” is marked by a bright star, but now the “W” is tipped up about 45 degrees on the right.

Let’s number the stars from left to right 1, 2, 3, 4 and 5. For example, star 3 is the middle star that joins the two “Vs” that make the “W”; star 2 is the bottom of the first “V.”

To star-hop to the Double Cluster from Cassiopeia, remember “3, 2, there you go.” (I just made that up, and it doesn’t rhyme, I know — unless you pronounce “go” more like “goo”).

The idea here is to extend a line from star 3 through star 2 out of Cassiopeia, about the same distance as stars 2 and 3 are separated, and there you go: the Double Cluster.

The thousands of stars in the Double Cluster will overflow the field of view of a small telescope.

The hot, blue stars in these clusters all formed between 75 million and 150 million years ago, making them infants sharing a stellar nursery. The clusters themselves are both about 7,000 light-years away; and are associated with the stars, dust and gas that form the plane of our Milky Way galaxy.

It is also known that the clusters and our sun are moving toward one another at the stately rate of about 45,000 mph.

And while you’re out there looking for the Double Cluster the next couple of nights, keep your eyes peeled for shooting stars. On Saturday and Sunday evenings, Earth passes through a stream of debris in space left behind by a comet called  21P/Giacobini-Zinner. This produces the Draconid meteor shower.

Most years, the Draconids are unimpressive, but sometimes they are spectacular. Some meteor experts are predicting that this will be an outburst year for the Draconids.

Here’s to clear skies and a few more warm nights.

— By Doug Furton, a member of the physics faculty at GVSU. Send questions and suggestions to dgf@inbox.com.


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