Virgo

FIELDS OF STUDY: Stellar Astronomy; Observational Astronomy

ABSTRACT: Virgo is the largest of the zodiac constellations and the second largest of all the constellations. It consists of fifteen named stars stars and about thirty-five exoplanets, which are planets that are outside of the solar system and orbit a star other than the sun. It also contains numerous deep-sky objects. Virgo can be viewed in the night sky between the months of April and September.

The Virgin Constellation

A constellation is an area of space defined by a group of stars in the night sky that resembles a picture or pattern. In ancient times, people believed these star shapes had spiritual importance. They also helped show the changing of the seasons. In modern times, astronomers study constellations to learn more about the universe. In 1930, the International Astronomical Union (IAU) recognized eighty-eight official constellations and set their boundaries in the night sky.

The constellation Virgo, which means "virgin" in Latin, is tied to agriculture, fertility, fortune, and justice. It is said to look like a woman carrying a bunch of wheat in her left hand. Virgo is one of the constellations in the zodiac, a group of twelve constellations through which the sun appears to pass over the course of a year. The sun’s path through the zodiac is called the ecliptic.

Attributes of Virgo

Virgo is visible in both the Northern and the Southern Hemispheres. The second-largest constellation, it covers 1,294 square degrees and is visible between latitudes 80 degrees north and 80 degrees south. The best time to view it is during the month of May around 10:00 p.m. local time. Virgo is below the constellations Boötes and Coma Berenices and sits west of Leo and east of Libra. Corvus and Crater are just below it and the ecliptic. Its declination is −3.73 degrees from the celestial equator, and its right ascension is 13.2 hours.

Many of the stars in the Virgo constellation are dim, but its brightest star, alpha Virginis, also known as Spica, is easy to find in night sky. Spica represents the bundle of wheat in Virgo’s left hand. Using the Big Dipper in the Ursa Major constellation as a guide, viewers can follow its curved handle to the southeast until they see the bright star alpha Boötis (Arcturus) in Boötes. The next brightest star down is Spica.

Spica is considered the sixteenth-brightest star in the sky, with a visual magnitude of 0.98. It is actually a binary star, or two stars that revolve around a common center of mass. This pair of giant blue stars is located about 260 light-years from Earth. Spica A is ten times as massive and more than 12,000 times as luminous as of the sun. Its companion, Spica B, is only six times as massive as the sun and 1,500 times as luminous.

Gamma Virginis, also known as Porrima or Arich, is the next-brightest star of Virgo. It is also a binary star. The third-brightest star of Virgo is the yellow giant star epsilon Virginis, also known as Vindemiatrix, the grape gatherer. Zeta Virginis (Heze) is a dwarf star that rotates in less than half a day. In 1992, the first exoplanets ever discovered were found orbiting a pulsar in Virgo. As of 2022, thirty-five exoplanets have been found orbiting thirty-two stars in Virgo. This gives Virgo more stars with exoplanets than any other constellation in the sky.

In addition to its fifteen named stars stars, Virgo contains eleven Messier objects as well as other deep-sky objects. Early astronomers searching for comets with telescopes saw objects that were later determined to be nebulae, which are clouds of gases or space dust, and deep-sky objects. During the eighteenth century, French astronomer Charles Messier (1730–1817) catalogued these objects, which were named after him. Among the constellations, Virgo has the second-largest number of Messier objects; Sagittarius has the most, at fifteen. Some of Virgo’s Messier objects (abbreviated M) include Messier 49 (M49), Messier 58 (M58), Messier 60 (M60), Messier 87 (M87), and Messier 104 (M104), the Sombrero galaxy. It also contains New General Catalog 4435 (NGC 4435) and New General Catalog 4438 (NGC 4438), the Eyes galaxies; New General Catalog 4567 (NGC 4567), the Siamese Twins; and the quasar 3C273. A quasar is a very bright object in space that gives off electromagnetic radiation and may get its energy from a massive, central black hole in its galaxy. In addition, Virgo and the constellation Coma Berenices contain the galaxy cluster known as the Virgo Cluster, which has at least two thousand galaxies.

The Virgin Myth

Greek Egyptian astronomer Ptolemy (ca. 100–ca. 170) identified and classified the constellation Virgo in the second century CE. Virgo, the virgin, is associated with several myths. Some link her to agriculture, fertility, fortune, and justice. Virgo is mostly associated with the season of spring. In addition, Virgo is located next to the constellation Libra, the scales of justice, which links Virgo to justice.

In some Greek myths, Virgo is associated with Demeter, also known as the corn goddess of fertility. According to one myth, long ago Earth experienced eternal spring. Then, one day, the god of the underworld, Hades, abducted Demeter’s daughter, Persephone, and Demeter turned her back on her role as goddess of fruitfulness. As a result, Earth saw frigid winters and scorching summers, which deterred growth and new life. Zeus, the king of gods, demanded that Persephone be returned. Persephone was reunited with her mother, but because she ate Hades’s pomegranate, she was obligated to return to the underworld for four months a year. The time she is with Demeter represents spring and summer in the Northern Hemisphere, which is why Virgo can be seen in the sky then. In a similar Babylonian myth, the goddess Ishtar, associated with Virgo, descends to the underworld to retrieve her brother-lover Tammuz.

In another Greek myth, Virgo is associated with Astraia, or Dike, the goddess of justice. According to the myth, Dike lived on Earth during the Golden Age, a time of peace, abundance, and spring. In time, the Bronze Age began and mortals became lawless. Dike tried to reason with the humans, but she eventually fled Earth for the sky.

Modern Astronomical Importance

In ancient times, people used the Virgo constellation to track the changing seasons. Because Virgo was visible in the spring months in the Northern Hemisphere, it helped farmers determine when they could start planting. In modern times, scientists study the stars to determine much about outer space and in turn learn more about Earth.

Virgo made headlines in November 2012 when light from an exploding star, or supernova, in the Virgo Cluster reached Earth. Scientists determined that the star exploded 230 million years ago, during the Triassic period on Earth. They classified the event as supernova 2012ha, or Sherpa. The scientists learned that the supernova was the result of an exploding white dwarf star as large as the sun. They believe that when the star died, its core shrunk to about the size of Earth.

In 2019, astronomers using a series of Earth-based radio telescopes known as the Event Horizon Telescope captured the first-ever image of a black hole. The black hole was churning away at the center of M87, a large galaxy in Virgo. A black hole is the remains of a massive star that collapsed in on itself during its death throes. Its gravity is so strong that nothing can escape, not even light.

PRINCIPAL TERMS

• celestial equator: the imaginary line above Earth’s equator that halves the celestial sphere; it is equally distant from the celestial poles.
• constellation: a region of space defined by a pattern of stars that can be seen in the night sky from Earth.
• declination: a space object’s angular distance north or south of 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: a space object’s longitudinal arc along the celestial equator, measured eastward from the vernal equinox and expressed in hours, minutes, and seconds.

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