NGC 457
An open cluster in Cassiopeia known as the Owl or E.T. Cluster.
NGC 457 is an open star cluster located in the northern constellation Cassiopeia. It goes by several alternative names: Caldwell 13, the Dragonfly Cluster, the E.T. Cluster, the Owl Cluster, the Kachina Doll Cluster, and the Phi Cassiopeiae Cluster. German-British astronomer William Herschel first spotted it on August 18, 1780, using a 6.2-inch reflector telescope, and recorded it as object VII 42. Amateur astronomers find it easy to observe, even with small telescopes under light-polluted skies.
The cluster lies more than 7,900 light-years from the Sun and is estimated to be about 21 million years old. Its popular nicknames—Owl Cluster and E.T. Cluster—come from its resemblance to the movie character, with two bright stars forming the "eyes": Phi Cassiopeiae (magnitude 5, spectral type F0) and HD 7902 (magnitude 7). Whether Phi Cassiopeiae actually belongs to the cluster is uncertain; if it does, it would rank among the brightest known stars, outshining Rigel. For perspective, the Sun placed at that same distance would appear at only magnitude 17.3. The next brightest member is the red supergiant variable star V466 Cassiopeiae. The cluster contains a rich field of roughly 150 stars between magnitudes 9 and 13, with about 60 confirmed as true members.
Quick Facts
- Epoch
- J2000.0
- Ra
- 01 · 19 · 32.6
- Dec
- +58 · 17 · 27
- Constellation
- Cassiopeia
- Dist Ly
- 7.922 kly
- Dist Pc
- 2.429 kpc
- Appmag V
- 6.4
- Names
- Owl Cluster, E.T. Cluster, Caldwell 13, Cr 12, Mel 7, OCL 321, Lund 43, H VII-42, h 97, GC 256
Facts from the source article.
Lore & Background
NGC 457 lies over 7,900 light years from the Sun and has an estimated age of 21 million years. Amateur astronomers sometimes refer to it as the Owl Cluster or the E.T. Cluster due to its resemblance to the movie character. Two bright stars, Phi Cassiopeiae (magnitude 5, spectral type F0) and HD 7902 (magnitude 7), can be imagined as eyes. It is not yet clear if Phi Cassiopeiae is a true member of the cluster; if it is, it would be one of the brightest stars known, surpassing Rigel in luminosity. For comparison, the Sun at the same distance as Phi Cassiopeiae would shine at just magnitude 17.3. The next brightest star is the red supergiant variable star V466 Cassiopeiae. The cluster features a rich field of about 150 stars of magnitude 9 to 13, with about 60 stars identified as true members.
Reader's Guide
NGC 457 holds significance as a readily observable open cluster that remains accessible even under light-polluted skies with small telescopes. Its distinctive arrangement of two bright foreground stars—Phi Cassiopeiae and HD 7902—has inspired multiple popular nicknames among amateur astronomers, reflecting its perceived resemblance to an owl or the character E.T. The uncertainty surrounding Phi Cassiopeiae's membership adds to the cluster's interest: if it is a member, its luminosity would place it among the most intrinsically bright stars known, far outshining Rigel. The cluster's age of 21 million years and distance of over 7,900 light years place it among the younger, more distant open clusters in the Milky Way. Its rich field of about 150 stars in the magnitude 9–13 range, with roughly 60 confirmed members, provides a rewarding target for visual observation and astrophotography. The presence of the red supergiant variable V466 Cassiopeiae further enriches the cluster's stellar population. Discovered by William Herschel in 1780, NGC 457 remains a staple of amateur astronomy and a subject of ongoing study regarding stellar membership and evolution.
Did You Know?
- NGC 457 is also known as the Dragonfly Cluster, E.T. Cluster, Owl Cluster, Kachina Doll Cluster, or Phi Cassiopeiae Cluster.
- The cluster contains about 60 identified true members out of a field of roughly 150 stars.
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