Eris: The Dwarf Planet

Eris is a dwarf planet located in the scattered disc of our solar system, beyond the orbit of Neptune. It was discovered in 2005 by a team of astronomers led by Mike Brown at the Palomar Observatory.

Initially thought to be larger than Pluto, Eris's discovery sparked a debate in the astronomical community about what constitutes a planet, ultimately leading to the reclassification of Pluto as a dwarf planet in 2006.

Eris is named after the Greek goddess of strife and discord, reflecting the controversy its discovery caused in the scientific community regarding the definition of a planet.

Eris was discovered on January 5, 2005, from data collected on October 21, 2003. The discovery was announced on July 29, 2005, the same day as two other large trans-Neptunian objects: Haumea and Makemake.

The team that discovered Eris consisted of Mike Brown, Chad Trujillo, and David Rabinowitz. They used the Samuel Oschin telescope at Palomar Observatory in California.

Initially designated as 2003 UB313, the object was later named Eris after the Greek goddess of strife and discord. Its moon was named Dysnomia, after the daughter of Eris and the demon goddess of lawlessness.

Eris is one of the largest known dwarf planets in our solar system. It has a highly eccentric orbit that takes it from 38 AU to 97 AU from the Sun, with an orbital period of about 557 years.

Eris has one known moon, Dysnomia, which was discovered in September 2005. The presence of this moon helped astronomers determine Eris's mass through Kepler's third law.

The surface of Eris is highly reflective, suggesting it's covered with methane ice. Its high albedo (reflectivity) makes it one of the brightest objects in the solar system.

The discovery of Eris had a profound impact on our understanding of the solar system. Initially thought to be larger than Pluto, it raised the question: if Pluto is a planet, shouldn't Eris be one too?

This debate led the International Astronomical Union (IAU) to formally define the term "planet" for the first time in 2006. According to the new definition, a planet must:

• Orbit the Sun
• Be massive enough to be rounded by its own gravity
• Have cleared the neighborhood around its orbit

Since Eris, like Pluto, has not cleared its orbital neighborhood, both were classified as dwarf planets. This reclassification demoted Pluto from its status as the ninth planet.