Image Credit & Copyright: Vangelis Souglakos
In the northern hemisphere, on a clear night you have the ability to view one of the most beautiful star clusters in the night sky; the Perseus double. One look at this object resolves itself as a duo of open star clusters containing a few hundred stars each. The double was discovered, or at least cataloged in 130 BC by Greek astronomer Hipparchus. The stars within this formation, based on luminosity and color, prove to be much hotter and younger than that of our Sun. Add their close proximity and any detective would be certain that they were formed of the same star forming region. The double is cataloged into two NGC components; NGC884 on the left is slightly larger than NGC869 and it’s also decorated with a few red giant stars. NGC869 on the right is the brighter denser cluster of the two.
The cluster is easy to find if you are at all familiar with the basic constellations. If you can identify the classic “W” of Cassiopeia, follow the two stars Navi and Ruchbah in a straight line down to the double. Also as the asterism of the Big Dipper sets in the northwest, Perseus rises in the northeast.
Here’s a fun little story behind this duo. Perseus; the mythological Greek symbol for adventure. The son of Zeus and Danae he was a demigod though not immortal. When challenged by King Polydectes to slay Gorgons (Medusa), he was given a helmet, shield and curved sword with studded jewels in the handle by other gods; namely Athena and Hermes. Perseus did indeed behead Medusa but he didn’t stop there. He also saved Andromeda (Daughter of Cepheus and Cassiopeia and future wife to Perseus) who was chained to a rock, left as a sacrifice by Zeus’s brother Poseidon to the sea monster Cetus. His reward for his amazing deeds, the gods placed Perseus among the stars……One hand holding the head of Medusa and in the other, the jewel studded sword, represented by the double cluster.
NAME: Perseus Double Cluster, Caldwell 14, NGC 884 (Chi Persei), NGC 869 (h Persei).
WHAT IS IT?: Double open star cluster.
HOW FAR AWAY IS IT?: NGC 884 is 7600 light years distant while NGC 869 is 6800 light years distant. They are both hurtling toward Earth, blue shifted at about 22 kilometers per second.
HOW BIG IS IT?: NGC884 is approximately 35’ arcminutes in size while NGC869 is approximately 29’ arcminutes in size on the night sky. They are each roughly 70 light years in diameter.
HOW OLD IS IT?: NGC884 is listed as 3.2 million and NGC869 is listed as 5.6 million years old, making them very young.
APPARENT MAGNITUDE?: Each are approximately at an apparent magnitude of around 4.5 which makes them observable with your eyes alone in a dark location.
WHERE IS IT? (General): Constellation Perseus (Circumpolar). If you know the constellation Cassiopeia, follow the stars Navi and Ruchbah as they point directly down at the double.
WHERE IS IT? (Exact RA/DEC J2000): NGC884 = RA: 02h 22m 32s Dec: +57d 08′ 39″. NGC869 = RA: 02h 19m 04s Dec: +57d 08′ 06″.
Vangelis Souglakos Astrophotography: http://www.celestialpixels.com/Star-Clusters/