Eris

Eris is one of the largest known dwarf planets in the Solar System. It was discovered on 5 January 2005 by Mike Brown from the California Institute of Technology, Chad Trujillo from the Gemini Observatory, and David Rabinowitz from Yale University during observations of the outer Solar System at the Palomar Observatory. The data used for its discovery were obtained from observations dated 21 October 2003. Initially named 2003 UB313, this celestial body was popularly referred to by the name of the television character Xena. On 14 September 2006, the International Astronomical Union (IAU) officially named the dwarf planet Eris, after the Greek goddess of discord. Its moon was named Dysnomia, after the goddess of lawlessness and daughter of Eris.

The discovery of Eris reignited debates over Pluto’s planetary status, leading the IAU in 2006 to reclassify Pluto as a dwarf planet. As a result, the number of planets in the Solar System was reduced to eight, with Pluto, Ceres, and Eris now categorized as dwarf planets.

Image of Eris (NASA)

Physical Properties and Structure

Eris has an equatorial diameter of approximately 2,400 kilometres, which is about one-fifth the diameter of Earth and slightly smaller than Pluto. Its mass is estimated at 1.66 × 10²² kg, making it about 27 percent more massive than Pluto. Surface temperatures range from -217 °C (-359 °F) to -243 °C (-405 °F), and the surface is likely composed of rocky and icy material.

Very little is known about its internal structure, but surface and atmospheric observations suggest similarities to Pluto. Due to its great distance from the Sun, Eris’s atmosphere largely collapses and freezes onto the surface as snow. When it reaches its closest point to the Sun in its orbit, the atmosphere sublimates again. No current information is available regarding its magnetosphere.

Orbit and Rotation

Eris takes approximately 557 Earth years to complete one orbit around the Sun. Its orbit is highly inclined, at an angle of 44 degrees relative to the ecliptic, and extends beyond the Kuiper Belt into the scattered disc region. Its day length is approximately 25.9 hours, similar to that of Earth.

Satellites

Eris has one known satellite, Dysnomia. Dysnomia’s diameter is estimated to be less than 150 kilometres, and it orbits Eris at a distance of approximately 37,370 kilometres. It completes one orbit in 15 to 16 days. It is believed to have formed from material ejected by a collision, similar to the process thought to have created Earth’s Moon.

Potential for Life

Due to its extremely cold surface conditions, the possibility of life existing on Eris is considered very low.

Dwarf Planets in the Solar System and Comparison

Eris is one of the dwarf planets in the Solar System, along with Pluto and Ceres.

• Pluto: Discovered in 1930, it has a diameter of approximately 2,390 kilometres and is composed mostly of ice and rock. Its orbit is highly inclined and eccentric, completing one revolution around the Sun in 248 years. Pluto’s largest moon is Charon, and the system is known as the only tidally locked planet-moon pair. Pluto also has two smaller moons, Nix and Hydra.

• Ceres: Discovered in 1801, it is the largest and most massive object in the asteroid belt. It has a diameter of approximately 950 kilometres and accounts for about one-third of the total mass of the asteroid belt.

Formation and Location

Eris resides beyond the Kuiper Belt in a region known as the scattered disc. This distant region contains thousands of icy and rocky bodies left over from the early Solar System and is home to trans-Neptunian objects or plutoids.

The discovery of Eris prompted a reevaluation of the structure of the Solar System and the definition of a planet, marking a significant milestone in modern astronomy.

^{Dwarf Planet Eris} (Pixabay)