The Owl Cluster (NGC 457) - A Bright Open Star Cluster in Cassiopeia

Basic Information

• Name: Owl Cluster (NGC 457), also known as the E.T. Cluster.
• Type: Open Star Cluster
• Location: Constellation Cassiopeia
• Distance from Earth: Approximately 7,900 light-years.
• Apparent Magnitude: 6.4, making it visible with binoculars and small telescopes.
• Age: Estimated to be around 20 million years old.

Physical Characteristics

• The Owl Cluster is a young open star cluster, containing a mix of bright and faint stars.
• Two prominent stars, Phi Cassiopeiae (magnitude 5) and HD 7902 (magnitude 7), are often imagined as the "eyes" of the owl, giving the cluster its name.
• The cluster spans about 13 arcminutes in the sky and contains over 100 stars, many of which are hot, blue stars typical of young clusters.

Discovery and History

• The Owl Cluster was discovered by William Herschel on August 18, 1780, using a 6.2-inch reflector telescope.
• It was cataloged as VII 42 in Herschel's deep-sky catalog.
• The cluster is also nicknamed the E.T. Cluster due to its resemblance to the famous extraterrestrial character from Steven Spielberg's movie.

Observational Highlights

• Visibility: Best observed during the autumn and winter months in the Northern Hemisphere when Cassiopeia is high in the sky.
• Best Observing Tools: Binoculars or a small telescope can easily reveal the cluster's bright stars and its distinctive "owl-like" shape.
• Nearby Objects: The Owl Cluster is located in a rich star field in Cassiopeia, making it a great target for stargazers exploring the region.

Interesting Facts

1. Shape and Name: The cluster's "owl-like" appearance is due to the arrangement of its stars, with the two bright "eyes" and fainter stars forming the "wings."
2. Young Age: At only 20 million years old, the Owl Cluster is relatively young compared to other open clusters.
3. Cultural Connection: Its nickname, the E.T. Cluster, adds a fun pop-culture connection for amateur astronomers.

How to Locate the Owl Cluster

1. Find Cassiopeia: Locate the constellation Cassiopeia, which is shaped like a "W" or "M" in the northern sky.
2. Use a Star Map: The Owl Cluster is located near the star Ruchbah (Delta Cassiopeiae). A detailed star map or astronomy app can help pinpoint its exact location.
3. Enhance Visibility: Observing from a dark-sky location will improve your view of the cluster's fainter stars.