by Ann » Thu Aug 18, 2016 2:13 pm
Chris Peterson wrote:
Actually, Perseus originates from our own Solar System. Constellations are historically defined by 2D asterisms, and in modern usage by 2D boundaries on the sky. In the 3D context of the Universe, they don't exist. So actually, saying the meteors have a radiant in a constellation makes perfect sense from a purely local standpoint. It is not an illusion that the meteors appear to originate from a single point on the sky (unless you want to classify the vanishing point of parallel lines as an "illusion").
Most certainly constellation Perseus is a human-made creation, but the Alpha Perseus Cluster is not.
Wikipedia wrote:
The Alpha Persei Cluster, also known as Melotte 20 or Collinder 39, is an open cluster in the constellation of Perseus. To the naked eye, the cluster consists of several blue spectral type B type stars. The most luminous member is the ~2nd magnitude white-yellow supergiant Mirfak, also known as Alpha Persei. Bright members also include Delta, Epsilon, Psi, 29, 30, 34 and 48 Persei. The Hipparcos satellite and infrared color-magnitude diagram fitting have been used to establish a distance to the cluster of ~172 pc.[2][3] The distance established via the independent analyses agree, thereby making the cluster an important rung on the cosmic distance ladder. The age of this cluster is about 50-70 million years.[1][4]
So although for example Beta Persei, Algol, has nothing whatsoever to do with the Alpha Perseus Cluster, the cluster in itself is a physical grouping in its own right. Boomer is correct to point out that while it looks as if the radiant point of the Perseids is very near the Alpha Persei Cluster, in reality the cluster and the Perseids have nothing to do with one another.
Ann
[quote="Chris Peterson"]
Actually, Perseus originates from our own Solar System. Constellations are historically defined by 2D asterisms, and in modern usage by 2D boundaries on the sky. In the 3D context of the Universe, they don't exist. So actually, saying the meteors have a radiant in a constellation makes perfect sense from a purely local standpoint. It is not an illusion that the meteors appear to originate from a single point on the sky (unless you want to classify the vanishing point of parallel lines as an "illusion").[/quote]
Most certainly constellation Perseus is a human-made creation, but the Alpha Perseus Cluster is not.
[quote][url=https://en.wikipedia.org/wiki/Alpha_Persei_Cluster]Wikipedia[/url] wrote:
The Alpha Persei Cluster, also known as Melotte 20 or Collinder 39, is an open cluster in the constellation of Perseus. To the naked eye, the cluster consists of several blue spectral type B type stars. The most luminous member is the ~2nd magnitude white-yellow supergiant Mirfak, also known as Alpha Persei. Bright members also include Delta, Epsilon, Psi, 29, 30, 34 and 48 Persei. The Hipparcos satellite and infrared color-magnitude diagram fitting have been used to establish a distance to the cluster of ~172 pc.[2][3] The distance established via the independent analyses agree, thereby making the cluster an important rung on the cosmic distance ladder. The age of this cluster is about 50-70 million years.[1][4][/quote]
So although for example Beta Persei, Algol, has nothing whatsoever to do with the Alpha Perseus Cluster, the cluster in itself is a physical grouping in its own right. Boomer is correct to point out that while it looks as if the radiant point of the Perseids is very near the Alpha Persei Cluster, in reality the cluster and the Perseids have nothing to do with one another.
Ann