Looking Up: Looking for the Double Cluster
This is a great time to see the Double Cluster. It is near the marvelous “M” shape of Cassiopeia in the northern sky and can be seen with just your eyes.
If the sky is sufficiently free of light pollution and there is no moon, you should be able to see a “fuzzy patch.” Whether you find it or not with eyes alone, grab a pair of binoculars and have a look.
Remarkable about the stars of the Double Cluster is not their brilliance to unaided eyes but their unusual pairing, appearing like nearly identical twins next to one another.
Binoculars will show them plainly, as a pair of compact bursts of stars. A small telescope at low magnification offers a stunning view. The stars will appear brighter and you will see more of them.
With a telescope, you can closely inspect and count the cluster stars, enjoy tracing their patterns and look for colors (a few of the faint stars are red). Higher magnification may show one cluster at a time; a slight nudge will take your telescope to the other cluster.
The two star clusters are approximately 7,500 light years away (one is 7,600 and the other 6,800); that's how many years it takes for their light to reach us traveling in excess of 186,000 miles a second. (The Pleiades are only about 450 light years away.)
These clusters are within the bounds of the constellation Perseus, an ancient Greek folk hero situated between the constellation Andromeda, Perseus’ mythological lover, and the constellation Cassiopeia, representing Andromeda's royal mother. The Double Cluster, to the Greeks, represents the jeweled handle of Perseus’s sword.
Observed from antiquity as a curious patch of light, its true nature as a double assembly of stars was not revealed until William Herschel first examined it with a telescope in the early 19th century.
To find the Double Cluster, first locate Cassiopeia. The five brightest stars form an unmistakable 'M' which appears to be tipping, balancing on one end, at around 8 p.m. in mid-November. Binoculars will help you find the Double Cluster as you slowly scan to the right of the lower portion of the 'M.' The clusters are only a little farther from the 'M' as it is between any of two stars marking the four 'legs' of Cassiopeia's 'M.'
Star clusters abound in the galaxy. A small telescope will help you locate scores of them along the star-studded Milky Way band. No optical aid is needed at all to see the beautiful Pleiades star cluster, its six or seven brightest stars easily seen, compacted close together. The Pleiades may be seen high in the east on autumn evenings. Lower left of the Pleiades is an even larger but dimmer star, the Hyades. This group traces a 'V' shape but on its side when seen in the east.
Astronomers list the two members of the Double Cluster as NGC 884 and NGC 869. The New General Catalog, one of several databases, identifies and locates thousands of star clusters, galaxies and nebulous patches found among the constellations.
There ought to be a common name for the Double Cluster. After all, we don't call the Pleiades “Cluster” or “Single Cluster”! Maybe you would like to think of a name and share it with me. Your suggestions may be included in the next column; who knows, one may catch on! Send your suggestion to email@example.com. Let me know if you've seen the Double Cluster and what you thought!
New moon is on November 22.
Keep looking up!