Aries
Aries is a constellation recognized since ancient times, characterized by its faint star pattern that resembles a ram. It is part of the zodiac, a group of twelve constellations that align with the sun's apparent path across the sky, known as the ecliptic. Aries is best observed during the Northern Hemisphere's late winter months and is located between the constellations Pisces and Taurus. This constellation features notable stars such as alpha Arietis (Hamal), an orange giant, and two binary stars, Sheratan and Mesarthim.
Historically, Aries has been associated with various myths across different cultures, with the most famous Greek tale involving a ram that rescued two children, leading to the ram's transformation into this celestial figure. The constellation plays a significant role in tracking seasonal changes, as it marks the point of the vernal equinox, traditionally celebrated as the arrival of spring. In modern astronomy, Aries continues to be of interest for its deep-sky objects, including galaxies and variable stars, contributing to our understanding of the universe.
Aries
FIELDS OF STUDY: Stellar Astronomy; Observational Astronomy
ABSTRACT: The constellation Aries is a group of stars best seen in the Northern Hemisphere. Its main stars appear to form a line with a bent end, a pattern some ancient people thought resembled a ram. Aries contains a few bright stars, double stars, and variable stars, as well as distant galaxies and nebulae. It is the source of numerous meteors seen entering Earth’s atmosphere. Long ago, constellations such as Aries guided agriculture and religion; in modern times, astronomers study them to learn about the universe.
The Ram Constellation
Since ancient times, people have scanned the sky and searched for images among the stars. These images helped shape myths and spiritual narratives as well as mark the changing seasons of the year. Since 1930, the International Astronomical Union (IAU) has recognized eighty-eight constellations, the boundaries of which were set by astronomer Eugène Delporte (1882–1955). Among the best known of these is Aries, which is shaped like a line with a bent end. Ancient cultures interpreted this shape in many different ways, most famously as a ram.
Aries is also famous for its inclusion in the zodiac, a group of twelve or thirteen constellations intersected by the path the sun appears to travel with respect to the stars over the course of a year. This path, called the ecliptic, is an illusion caused by Earth’s orbit around the sun. Since ancient times, many cultures have ascribed mystical or spiritual significance to the zodiac.
Modern astronomers locate constellations by measuring their position relative to the celestial equator, the projection of Earth’s equator onto the night sky. Aries has a declination of approximately +20 degrees and a right ascension of 2.66 hours. Declination and right ascension correspond to latitude and longitude on Earth.
Attributes of Aries
Aries is a Northern Hemisphere constellation that is best seen during the late winter months of November and December. It is located between fellow zodiacal constellations Pisces to the east and Taurus to the west. Below Aries is Cetus, the whale; above it is Musca Borealis, the northern fly, a constellation no longer officially recognized by astronomers. Other constellations nearby include Perseus, named for the ancient Greek mythological hero, and Triangulum (the triangle). Aries is roughly average in size among the constellations, ranking thirty-ninth largest of the eighty-eight major stellar groups recognized by modern astronomers. Despite its considerable span, Aries can be challenging to see because it is a relatively faint constellation with only a few bright stars.
Three of the brightest stars in the constellation make up the head and horn of the ram. These stars are alpha Arietis (known as Hamal), beta Arietis (Sheratan), and gamma Arietis (Mesarthim). Hamal is an orange giant, twice as massive and fifteen times as wide as the sun. It is the brightest star in the constellation. Observers in many areas can see Hamal with the naked eye, even though it is about sixty-six light-years from Earth. The name Hamal comes from an Arabic word meaning "the lamb." Sheratan is slightly dimmer, and viewing it may require the use of binoculars in some areas.
Sheratan and Mesarthim are both notable for being binary stars. A binary star is a system in which two stars in close proximity revolve around a common center of mass. There are several other binary stars in Aries, including epsilon Arietis, lambda Arietis, iota Arietis, and tau1 Arietis. Other stars in the constellation are variable stars, which is a star whose apparent brightness varies, sometimes greatly and unpredictably.
Like many other constellations, Aries also features an array of deep-sky objects such as nebulae (clouds of gas and dust) and galaxies. Some of the galaxies in or near Aries exhibit widely varying shapes and behaviors. These galaxies include elliptical (oval), spiral, and interacting forms. (The gravitational forces of interacting galaxies act on one another.) Two of the most notable spiral galaxies in Aries are New General Catalog 697 (NGC 697) and New General Catalog 772 (NGC 772, also known as Arp 78). The galaxy New General Catalog 1156 (NGC 1156) is considered an irregular galaxy because its form cannot be classified as any of the regular galactic shapes. The galaxy New General Catalog 877 (NGC 877) is the brightest in a cluster of eight interacting galaxies.
The constellation is home to multiple planets of interest in several solar systems. These include gas giants and super-Earths, many of which have been discovered only in the twenty-first century. Among these are two planets discovered in 2019 that orbit the red dwarf Teegarden's Star. Teegarden's Star b is a super-Earth with a mass of 1.05 Earths, while Teegarden's Star c is another super-Earth with a mass of 1.11 Earths.
Aries is also the point of origin for several meteor showers, mostly in the months of May and June. Some of these meteor showers are unusual because they can be seen during the daytime.
The Flying Ram and Golden Fleece
The star pattern now identified as Aries has a long history reaching back through many cultures. Although the constellation is now mostly known as a ram, various civilizations long ago created their own interpretations. For some people in the Marshall Islands, the stars represented a porpoise. To the Maya people, they formed the shape of an ocelot, a wildcat native to Central and South America.
Despite the varied interpretations, most of the stories that contribute to the popular mythology of Aries originated in ancient Greece. These stories differ in their details, but most deal with an extraordinary ram that rescued two children from danger. In these myths, the Theban king Athamas took a new queen, who schemed to have the king’s son Phrixus and daughter Helle killed. The air nymph Nephele took pity on the endangered children and, with the help of Hera, goddess of marriage, arranged for their rescue. The gods dispatched a flying ram to Athamas’s kingdom. The ram, known as Chrysomallus, picked up Phrixus and Helle to deliver them to safety. Along the way, Helle fell from the flying ram and drowned in a strait near modern-day Istanbul, Turkey, which was subsequently named Hellespont in her honor. Phrixus survived, arriving with the ram in the land of Colchis. There, Phrixus showed his gratitude by sacrificing the ram to the chief god, Zeus, in a sacred grove.
In a later myth, the fleece of the sacrificed ram turned to gold and became a prized possession of the king Aeetes. A hero named Jason and a group of adventurers known as the Argonauts embarked on a quest to capture the coveted fleece. Meanwhile, the spirit of Chrysomallus the ram had flown into the sky to assume a place among the stars, becoming the constellation Aries. Ancient astronomers claimed that the constellation is fairly dim because the ram had lost its sparkling golden coat.
Another, lesser-known Greek myth provided an alternate origin story for the constellation Aries. In this tale, the god of revelry, Dionysus, was lost in the desert. Just when he seemed doomed to die of thirst and hunger, Dionysus spotted a ram that led him to a well full of life-giving water. The grateful god then honored the ram by placing it among the stars.
Aries’s Importance in Modern Times
Modern astronomers and stargazers value the constellations for their unique beauty as well as the scientific information they can provide about the universe beyond Earth. Constellations are important for mapping the stars and planets of the universe as well as studying the different space objects within the stellar patterns. Like the other constellations, Aries contains several objects of astronomical interest.
Since early times, Aries has been important for tracking the progress of the seasons. In ancient times, the sun touched Aries on the first day of spring, the vernal equinox. People rejoicing in the new year would celebrate the appearance of Aries in the night sky. Even in the twenty-first century, the location of the sun at vernal equinox is called the "First Point of Aries." That name is outdated, however, since the motion of Earth’s axis has shifted the position of the sun at vernal equinox into the Pisces constellation.
One of the many stars in Aries, HD 19445, provided an important lesson for modern scientists. Astronomers studying this star in 1951 determined that it had relatively little iron, calcium, and other materials once believed common in all stars. Since HD 19445 is an extremely old star, astronomers were able to deduce that in the earliest days of the galaxy, iron and calcium were rare. Only over time did the stars create these vital materials that helped form not only Earth but also the human body.
PRINCIPAL TERMS
- celestial equator: the imaginary line in the night sky that follows Earth’s equator, dividing the celestial sphere in half.
- constellation: a region of space defined by a pattern of stars that can be seen in the night sky from Earth.
- declination: the north-south position of a celestial body relative to the celestial equator, expressed in degrees of arc.
- 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: the east-west position of a celestial body when viewed from the Earth’s equator, defined in relation to the vernal equinox (one of two points at which the ecliptic intersects the celestial equator) and expressed in hours and minutes.
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