Alpherg, designated as Eta Piscium, is the brightest star in the zodiacal constellation of Pisces, the celestial fish.
Key Facts & Summary
- Alpherg is situated at around 350 light-years / 107 parsecs away from the Sun in the thin disk population of the Milky Way.
- It is the brightest star in Pisces, having an apparent magnitude of +3.611.
- This star is a Gamma Cassiopeiae variable, displaying brightness variations over periods.
- Alpherg is a binary star composed out of two stars designated as A and B.
- The primary star is a G-type giant star of spectral type G7 IIIa. It has a weak magnetic field or around 0.4 gausses.
- The companion is a faint star that has an apparent magnitude of 7.51.
- Alpherg is bigger and more massive than our Sun. It has around 3.78 solar masses and 26.48 solar radii.
- This star is around 457 times brighter than our Sun. It is also cooler, having temperatures of only 4,937 K.
- The surface gravity on this star is 2.20 cgs.
- Alpherg has a radial velocity of 13.60 km / 8.4 mi per second, and a rotational velocity of 8.4 km / 5.2 mi per second.
- It is a very young star, being only 220 million years old.
- Alpherg would appear brighter to us if not for the interference of interstellar dust.
- The system’s binary nature was discovered in 1878 by amateur astronomer S. W. Burnham.
- The fainter companion takes 850 years to orbit the primary star once. Its orbit has an eccentricity of 0.47.
- The constellation of Pisces is quite faint, however, it is the 14th largest constellation in the sky, stretching for around 889 square degrees.
- Regardless, this constellation hosts a number of interesting stars and deep-sky objects.
- The best time to view them is during November.
Eta Piscium bore the traditional names Al Pherg and Kullat Nunu. At the time that the vernal equinox entered into Pisces, this star system was located in the first ecliptic constellation of the Neo-Babylonians.
Nunu was the Babylonian word for fish, while Kullat referred to either the bucket or the cord that holds the fish together. In 2016, the IAU officially approved the name Alpherg for the Eta Piscium primary star.
Alpherg formed roughly 220 million years ago from an interstellar medium of gas and dust. Gravity pulled the swirling gas and dust together and resulted in the brightest star in Pisces, Alpherg.
Distance, Size, and Mass
Alpherg is situated at around 350 light-years / 107 parsecs away from our Solar System. It is quite a faint star. The physical characteristics of the fainter companion star are currently unknown.
In regards to the primary star, it is both more massive and also larger than our Sun. Alpherg has 3.78 solar masses, or 378% of our Sun’s mass, and 26.48 solar radii, or 2,648% of our Sun’s radius. Thus, it is more than 40 times bigger than our Sun.
Alpherg is a G-type giant star of spectral type G7 IIIa. It has a weak magnetic field with a strength of only 0.4 G. Alpherg is quite an energetic star, being 457 times brighter than our Sun.
It has an apparent magnitude that varies from +3.611 to 3.83, and an absolute magnitude of -1.52. Its companion star is even fainter, having an apparent magnitude of 7.51. Alpherg would appear brighter to us if not for the interference of interstellar dust.
Alpherg has a radial velocity of 13.60 km / 8.4 mi per second, and a rotational velocity of 8.4 km / 5.2 mi per second. Despite its huge energy output, Alpherg is cooler than our Sun, having temperatures of only 4,937 K.
Alpherg is a binary star composed out of two stars designated as A and B. It has an orbital period of roughly 850 years, a semimajor axis of 1.2 arc seconds, and an eccentricity of 0.47.
Alpherg is located in the northern zodiacal constellation of Pisces, the celestial fish. It is the brightest star in this constellation, being the star in the cord near the tail of the Northern Fish. The constellation of Pisces is relatively faint and devoid of bright stars.
Pisces is among the 48 Greek constellations first listed by the Greco-Roman astronomer Ptolemy, in his 2nd century Almagest. It is among the largest constellation in the sky, being the 14th largest out of the 88 modern constellations, occupying an area of around 889 square degrees.
Pisces is the Latin plural for “fish”, and the constellation itself is associated with the myth of Aphrodite and her son Eros, who were either rescued by two fishes, or they shape-shifted into fishes to flee from the monster Typhon. Currently, there are around 13 confirmed stars in Pisces that host planets.
Some interesting stars in Pisces, apart from its brightest star Alpherg, are Van Maanen’s star, Alrescha, Fumalsamakah, Delta Piscium, Epsilon Piscium, Revati, Torcular, Omega Piscium, and Gamma Piscium, among many others.
The constellation of Pisces also hosts some interesting deep-sky objects, such as the colliding galaxies NGC 520, the spiral galaxy NGC 488, the CL 0024+1654 galaxy cluster, the radio galaxy 3C 31, the Pisces Dwarf Galaxy, or the CGCG 436-030 spiral galaxy, among many others.
Pisces is located in the first quadrant of the northern hemisphere (NQ1) and can be seen at latitudes between +90o and -65o. The best time to observe the stars and deep-sky objects in Pisces is during the month of November.
Did you know?
- The Chinese knew Alpherg as You Geng Er – the Second Star of Official in Charge of the Pasturing.
- The Official in Charge of the Pasturing is a Chinese asterism that consists of Alpherg, Rho Piscium, Pi Piscium, Omicron Piscium, and 104 Piscium.
- The ancient Babylonians called a part of Pisces – DU.NU.NU – the fish cord, or ribbon, as evidenced in the first-millennium BC texts known as the Astronomical Diaries.
- The constellation of Pisces is associated with the German legend of Antenteh, who owned just a tub and a crude cabin when he met a magical fish. They offered him a wish, which he refused, however, his wife persuades him to return to the fish and ask for a beautifully furnished home. They granted this wish, but his wife was not satisfied. She then asked to be a queen and have a palace, and this wish was granted. The wife then wanted to become a goddess, but the fish became angry and took the palace and home, leaving the couple with the tub and cabin once again. The tub in this story is sometimes recognized as the Great Square of Pegasus.
- The stars in Pisces were incorporated into several Chinese constellations, such as Wai-ping, or Koui-siou.