Please Tweet #AskNASA Why haven't you taken a photo of Planet Eris in over 10 years? Planet/Dwarf Planet ERIS was originally declared Planet X or Planet 10 by the International Astronomical Union & then stripped of the title along with Pluto. Eris is so amazing it disrupted all of Astronomy & how we think of the Solar System. It's so Amazing the ESA & NASA haven't really talked about it or taken a photo of it in over 10 years. That's weird.
God bless everyone,
@newTHOR on twitter
more info on Eris
Eris (minor-planet designation 136199 Eris) is the most massive and second-largest dwarf planet[g] known in the Solar System. It is also the ninth-most-massive known body directly orbiting the Sun,[g] and the largest known body in the Solar System not visited by a spacecraft. It is measured to be 2,326 ± 12 kilometers (1,445.3 ± 7.5 mi) in diameter. Eris is 27% more massive than dwarf planet Pluto, though Pluto is slightly larger by volume. Eris' mass is about 0.27% of the Earth's mass.
Eris was discovered in January 2005 by a Palomar Observatory-based team led by Mike Brown, and its identity was verified later that year. It is a trans-Neptunian object (TNO) and a member of a high-eccentricity population known as the scattered disk. It has one known moon, Dysnomia. As of February 2016, its distance from the Sun is 96.3 astronomical units (1.441×1010 km; 8.95×109 mi), roughly three times that of Pluto. With the exception of some comets, Eris and Dysnomia are currently the second-most-distant known natural objects in the Solar System, [h] the farthest object being V774104 discovered in November 2015 at 103 AU.
Because Eris appeared to be larger than Pluto, NASA initially described it as the Solar System's tenth planet. This, along with the prospect of other objects of similar size being discovered in the future, motivated the International Astronomical Union (IAU) to define the term planet for the first time. Under the IAU definition approved on August 24, 2006, Eris is a "dwarf planet", along with objects such as Pluto, Ceres, Haumea and Makemake, thereby reducing the number of known planets in the Solar System to eight, the same as before Pluto's discovery in 1930. Observations of a stellar occultation by Eris in 2010 showed that its diameter was 2,326 ± 12 kilometers (1,445.3 ± 7.5 mi), not significantly different from that of Pluto. After New Horizons measured Pluto's diameter as 2372±4 km in July 2015, it was determined that Eris is slightly smaller in diameter than Pluto.[
Eris was discovered by the team of Mike Brown, Chad Trujillo, and David Rabinowitz on January 5, 2005, from images taken on October 21, 2003. The discovery was announced on July 29, 2005, the same day as Makemake and two days after Haumea, due in part to events that would later lead to controversy about Haumea. The search team had been systematically scanning for large outer Solar System bodies for several years, and had been involved in the discovery of several other large TNOs, including 50000 Quaoar, 90482 Orcus, and 90377 Sedna.
Routine observations were taken by the team on October 21, 2003, using the 1.2 m Samuel Oschin Schmidt telescope at Palomar Observatory, California, but the image of Eris was not discovered at that point due to its very slow motion across the sky: The team's automatic image-searching software excluded all objects moving at less than 1.5 arcseconds per hour to reduce the number of false positives returned. When Sedna was discovered, it was moving at 1.75 arcsec/h, and in light of that the team reanalyzed their old data with a lower limit on the angular motion, sorting through the previously excluded images by eye. In January 2005, the re-analysis revealed Eris's slow motion against the background stars.
Follow-up observations were then carried out to make a preliminary determination of Eris's orbit, which allowed the object's distance to be estimated. The team had planned to delay announcing their discoveries of the bright objects Eris and Makemake until further observations and calculations were complete, but announced them both on July 29 when the discovery of another large TNO they had been tracking, Haumea, was controversially announced on July 27 by a different team in Spain.
More observations released in October 2005 revealed that Eris has a moon, later named Dysnomia. Observations of Dysnomia's orbit permitted scientists to determine the mass of Eris, which in June 2007 they calculated to be (1.66±0.02)×1022 kg, 27%±2% greater than Pluto's.