The name “Eris” comes from Greek mythology. She was the goddess of discord. In fact, her name means “strife” or “discord” in Greek. In ancient times, she occasioned the fall of Troy. It happened in the following manner.
When the Nereid Thetis married Peleus, the Greek gods and goddesses were invited to attend. Quite understandably, Eris was not invited. After all, no one wants to have discord in their marriage.
In revenge, Eris crashed the wedding banquet. As the Olympian divinities were eating, she threw a golden apple into their midst. To the apple, the following note was attached: “For the fairest.”
Hera, Athene, and Aphrodite contended for the prize. They asked Zeus to decide, but he wisely refused. Instead, a Trojan prince named Paris was the appointed judge.
Each of the three goddesses promised to reward Paris if he would decide in her favor. Aphrodite promised to give him the most beautiful girl in the world as his wife. Paris found this irresistible, even though he already enjoyed the love of a nymph called Oenone. So he decided in favor of the goddess of love.
Unfortunately, the most beautiful girl in the world was Helen, the wife of Menelaus, king of Sparta. With the help of Aphrodite, Paris stole the Spartan matron and carried her off to Troy.
Their adultery bore bitter fruit. The Greeks assembled a mighty armada, besieged Troy for ten years, and eventually sacked the city.
In recent years, Eris continued to foster quarrels, and she was not content to occasion the destruction of a single city. This time she caused the downfall of an entire planet. It happened in the following manner.
Nine planets used to dance around our sun. Mercury, Venus, Mars, Jupiter, and Saturn delighted the ancients with their nocturnal wanderings. European astronomers discovered two more. William Herschel discovered Uranus. Later John Adams, Urbain Leverrier, and Johann Galle all had a hand in the discovery of Neptune.
Finally, American astronomers got into the act. Percival Lowell suggested the existence of a ninth planet beyond the orbit of Neptune and used its supposed effects on the orbit of Neptune as a basis for calculating its position in the sky. He looked in vain, but Clyde Tombaugh, his fellow American, managed to find it after his death. It was called Pluto after the Roman god of the dead.
Toward the end of the 20th century, Pluto suffered a series of blows that began to shatter its prestige. Astronomers began to discover large heavenly bodies beyond the orbit of Neptune. They were collectively called trans-Neptunian objects or Kuiper belt objects, after the astronomer Gerard Kuiper.
A further complication arose when Brown, Trujillo, and Rabinowitz discovered a trans-Neptunian object that seemed to be larger than Pluto. Its discovery occasioned so much controversy that it eventually received the name Eris. If Pluto were a planet, it would obviously be unfair to withhold planetary status from Eris. But if Eris is a planet, what about Quaoar and other large trans-Neptunian objects? Where would astronomers draw the line?
Eventually, the discovery of Eris caused the fall of Pluto from planetary status. By a decree of the International Astronomical Union, Pluto was demoted to a new class of celestial bodies called dwarf planets. Eris, which was originally dubbed the tenth planet of the solar system, was also demoted to dwarf planet status. Other members of this select group are the asteroid Ceres and the Kuiper belt objects Makemake and Haumea.
However, controversy continued. Many Americans did not like to see their planet demoted, and many protested.
Eris, the cause of both ancient and modern quarrels, continues to trouble the world, even though she has been banished to a distant region far beyond the orbit of Neptune.
A Few Observations on Eris
Since trans-Neptunian objects are so far away from the Earth, it is difficult to get accurate estimates of their size. Astronomers are no longer sure that Eris is larger than Pluto. If a spacecraft manages to visit Eris, we may be surprised by the results.
According to Wikipedia, many astronomers do not classify Eris as a Kuiper Belt object. Its orbit is more eccentric than Quaoar and other Kuiper belt objects, and its aphelion lies way beyond the Kuiper Belt, the outer limit of which is about 50 astronomical units from the Sun. For this reason, many astronomers apply the term scattered disk objects to Eris and other bodies with similar characteristics. In this classification system, Kuiper belt objects and scattered disc objects together form the class known as trans-Neptunian objects.
Dysnomia is a satellite of Eris. It was discovered in 2005 by Mike Brown and others, not long after the discovery of Eris.
“The New Solar System” by Patricia Daniels
University of Oklahoma: The Marriage of Peleus and Thetis
Wikipedia: Eris (Dwarf Planet)
StarChild: Eris – a Dwarf Planet
Wikipedia: Kuiper belt
Wikipedia: Scattered disk