Pisces

FIELDS OF STUDY: Astronomy; Observational Astronomy

ABSTRACT: Pisces is a constellation, or pattern of stars, in the Northern Hemisphere. The large yet dim constellation is also part of the astronomical zodiac, along with twelve other constellations. As part of the zodiac, Pisces plays a particularly important role in the March equinox. The constellation resembles two fish that are joined together by a cord. Different myths, including those within Greek and Roman mythology, surround the constellation. The stars that make up Pisces include eta Piscium, gamma Piscium, alpha Piscium, beta Piscium, and Van Maanen’s Star. Pisces also contains the spiral galaxy known as Messier 74.

Part of the Zodiac

Pisces is one of the eighty-eight constellations that are officially recognized by the International Astronomical Union (IAU). It is also one of twelve constellations of the astronomical zodiac. These are the constellations through which the sun appears to travel over the course of a year. The sun’s apparent path through the zodiac is called the ecliptic.

The sun passes in front of Pisces from about March 12 to April 19 each year. The eleven other constellations that make up the astronomical zodiac are Aquarius, Aries, Cancer, Capricornus, Gemini, Leo, Libra, Sagittarius, Scorpius, Taurus, and Virgo.

Main Features

Pisces is Latin for "fish," plural. The Pisces constellation is located in the first quadrant of the Northern Hemisphere, northeast of the constellation Aquarius and northwest of the constellation Cetus. It is also bordered by the constellations Andromeda, Aries, Pegasus, and Triangulum.

Pisces is the fourteenth largest of the eighty-eight constellations, occupying a V-shaped area of 889 square degrees. It has a right ascension of 0.85 hours and a declination of +11.08 degrees. The constellation resembles two fish that are swimming in opposite directions, joined together by a cord.

Pisces is visible between the latitudes of 90 degrees north (the North Pole) and 65 degrees south. It is best seen in early November about 9 p.m., although it is difficult to locate with the naked eye because of its dim stars and its large area. Typically, a dark country sky is necessary to see the constellation. To find Pisces, it helps to first find the marker called the Great Square of Pegasus, which is part of the constellation Pegasus. The Circlet of Pisces, also called the head of the Western Fish, is located to the south of the Square of Pegasus. The Eastern Fish, which appears as though it is jumping upward, is located to the east of the Square of Pegasus. From the Southern Hemisphere or the northern tropics, however, the Eastern Fish looks like it is diving downward.

The principal stars that make up Pisces are eta Piscium, gamma Piscium, alpha Piscium, beta Piscium, and Van Maanen’s Star. Also called Alpherg or Kullat Nunu, eta Piscium, is a bright giant star and is the brightest star in the constellation. It is 316 times brighter than the sun and lies 294 light-years from Earth. Gamma Piscium is a yellow giant that is approximately 130 light-years away. Alpha Piscium, also known as Alrisha or Alrescha (the cord), is a pair of white dwarf stars 139 light-years from Earth. It is located where the two fish of Pisces are tied together at their tails. Beta Piscium, also called Fum al Samakah (mouth of the fish), is located about 492 light-years away. Van Maanen’s Star was discovered by and named after the Dutch astronomer Adrian van Maanen in 1917. Only 14 light-years away, Van Maanen’s Star is the closest single white dwarf to the sun.

History and Myths

Pisces was first described by the Babylonians, who also saw the constellation as two fish connected by a cord. The Greek astronomer Ptolemy (ca. 100–ca. 170) included Pisces in his list of forty-eight constellations.

There are several different myths about Pisces. It is believed that Greek and Roman myths about the goddess Aphrodite (Venus to the Romans) were inspired by the myth of Atargartis, the Syrian goddess of love and fertility who appeared as half woman, half fish. In one Greek myth, two Syrian river fish, Ikhthyes or Ichthyes, are associated with Aphrodite and her son Eros. While trying to escape the monster Typhon (Typhoeus), Aphrodite and Eros change into fish and enter the Euphrates River. They tie themselves together with a cord so they will not lose each other. A different Greek myth states that the two fish led Aphrodite and Eros to safety by carrying them on their backs. Similar Roman myths associate the two fish with Venus and Cupid, the Roman versions of Aphrodite and Eros.

Significance

Ancient people believed that zodiac constellations such as Pisces were especially significant. Pisces was not always considered the first constellation of the zodiac; the sun used to seem to pass through the constellation Aries on the vernal equinox instead. However, due to precession—the gradual change in the orientation of Earth’s axis—the sun began appearing in Pisces on the equinox in 68 BCE and will continue to do so until 2597 CE. This period is commonly referred to as the Age of Pisces. In 2597, the sun will seem to pass through the constellation Aquarius on the vernal equinox, and the Age of Aquarius will begin.

Modern astronomers are particularly interested in another distinguishing feature of Pisces: Messier 74 (M74), which is a grand-design spiral galaxy, or a spiral galaxy with a clear, organized spiral structure. M74 was discovered by Pierre Méchain (1744–1804) in 1780 and was later cataloged by Charles Messier (1730–1817). It is located between alpha Arietis and eta Piscium and is about equal in size to the Milky Way galaxy. The supernovas SN 2002ap and SN 2003gd have been observed in M74.

In 2014, astronomers discovered an exoplanet—a planet orbiting a star outside of our solar system—in the constellation. The planet, named GU Pisces b, orbits its star at a distance more than two thousand times that of Earth's orbit around the sun. As a result, GU Pisces b takes about eighty thousand years to make one full revolution. Astronomers have discovered more than five thousand exoplanets as of 2022. Sixty-eight of those have been found in Pisces.

PRINCIPAL TERMS

• constellation: a pattern of stars, developed by humans, that can be seen in the night sky from Earth.
• declination: a space object’s angular distance north or south of the celestial equator.
• International Astronomical Union: an association of professional astronomers from all over the world who define astronomical constants while promoting research, education, and discussion on important astronomical topics.
• right ascension: a space object’s longitudinal arc along the celestial equator, measured eastward from the vernal equinox.

Bibliography

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"Messier 74." SEDS Messier Database. SEDS-USA, 14 Aug. 2013. Web. 8 May 2015.

Plotner, Tammy. "Pisces." Universe Today. Fraser Cain, 30 Dec. 2008. Web. 4 May 2015.

Ridpath, Ian. "Pisces: The Fishes." Ian Ridpath’s Star Tales. Author, n.d. Web. 4 May 2015.

Ridpath, Ian, and Wil Tirion. Stars and Planets: The Most Complete Guide to the Stars, Planets, Galaxies, and the Solar System. 4th ed. Princeton: Princeton UP, 2007. Print.

Zimmermann, Kim Ann. "Pisces Constellation: Facts About the Fishes." Space.com, 22 Jan. 2018, www.space.com/21456-pisces-constellation.html. 14 June 2022.