Perseus

Astronomers created this map by measuring the locations of natural radio sources known as masers (pink dots in pullouts at right) and dust clouds (blue dots).

Figure 2. Astronomers created this map ofthe Perseus arm by measuring the locations of natural radio sources known as masers (pink dots in pullouts at right) and dust clouds (blue dots). At upper right, a shaded region shows the previously believed shape of the Perseus arm, demarcated by a combination of masers and dust clouds. New measurements (middle right) show that some of these dust clouds are much closer or farther from the Sun than originally thought. As a result, the Perseus arm may be much clumpier and less well-defined (lower right). Credits: Joshua Peek (STScI), Robert L. Hurt (Caltech, IPAC), Leah Hustak (STScI).

Perseus (abbreviation: Per), the Hero and rescuer of Andromeda from the jaws of Cetus, is a large northern constellation, bordering on Aries to the north and Taurus to the south. The figure of Perseus is thought to hold the head of Medusa in his hand (the star Beta Per representing her evil eye).

As well as a number of interesting stars, most notably Algol, Perseus boasts the Little Dumbbell Nebula, the Double Cluster, and another large, bright open cluster, M34 (NGC 1039), which can be seen with the naked eye on a dark night and can be resolved by a small telescope even at low power (magnitude 5.5; diameter 35 arcminutes; distance 1,400 light-years; RA 02h 42.0m, Dec +42° 47'). See below for details of the constellation's brightest stars.

Perseids

The radiants of the Perseids, shown in red.

The Perseids are a major annual meteor shower visible for a week or so before and after peaking on 12 August each year, the date on which Earth crosses the orbit. The maximum hourly rate is about 70 meteors. They appear to radiate from the constellation Perseus, from which they take their name. This shower is associated with Comet Swift-Tuttle (discovered in 1862, reappeared in 1992) and consists of debris left by the comet along its orbit. Typical velocity of a Perseid meteor is about 68 km (42 miles) per second.

Perseus arm

The Perseus arm is one of the spiral arms of our Galaxy, the nearest part of which lies in the direction of Perseus at a distance of about 7,000 light-years. The Perseus arm winds around to the other side of the Galaxy. Recent research suggests that it is much clumpier and less well-defined than previously thought. (Figure 2)

Perseus Cluster

Perseus Cluster. Wendelstein Observatory.

The Perseus Cluster (Abell 426) is a diffuse, irregular cluster of galaxies, containing about 500 members and located about 250 million light-years away, that is dominated by and centered on the Seyfert galaxy NGC 1275 associated with the radio source Perseus A. The mass of cluster has been estimated at 200 trillion solar masses.

Perseus-Pisces Supercluster

The Perseus-Pisces Supercluster is one of the largest known structures in the universe. Even at a distance of 250 million light-years, this chain of galaxy clusters extends more than 40° across the northern winter sky.

Stars in Perseus brighter than magnitude 4.0
star	vis mag	abs mag	spec type	distance (ly)	RA (h m s)	Dec (° ' ")
Alpha (Mirfak)	1.79	-4.51	F5Ib	592	03 24 19	+49 51 40
Beta (Algol)	2.09v	-0.18	B8V	93	03 08 10	+40 57 21
Zeta	2.84	-4.56	B1Ib	982	03 54 08	+31 53 01
Epsilon	2.90	-3.10	B0.5V+A2V	538	03 57 51	+40 00 37
Gamma	2.91	-1.51	G8III+A2V	256	03 04 48	+53 30 23
Delta	3.01	-3.04	B5III	528	03 42 55	+47 47 15
Rho (Gorgonea Terti)	3.32v	-1.68	M3III	325	03 05 11	+38 50 25
Eta (Miram)	3.77	-4.29	K3Ib	1,330	02 50 42	+55 53 44
Nu	3.77	-2.39	F5II	557	03 45 12	+42 34 43
Kappa (Misam)	3.79	1.10	K0III	112	03 09 30	+44 51 27
Omicron (Atik)	3.84	-4.44	B1III	1,480	03 44 19	+32 17 18
Tau (Kerb)	3.93	-0.48	G4II+A4VI	248	02 54 15	+52 45 45
Xi (Menkib)	3.98	-4.70	O7Iae	1,770	03 58 58	+35 47 28