October 27, 2011
Astronomers Size-Up Dwarf Planet Eris
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The European Southern Observatory (ESO) announced on Wednesday that astronomers have accurately measured the diameter of the dwarf planet Eris for the first time.
The planet, according to ESO, appears to have a reflective surface, which suggests it is uniformly covered in a thin layer of ice.
Astronomers made observations as Eris passed in front of a faint background star, which is an event that will not happen again until 2013.
“Observing occultations by the tiny bodies beyond Neptune in the Solar System requires great precision and very careful planning. This is the best way to measure Eris´s size, short of actually going there,” Bruno Sicardy, the lead author of the paper published in the journal Nature, said in a statement.
Eris was identified as a large object in the outer Solar System in 2005, and its discover was one of the factors that led to the classification of dwarf planets.
The surface of Eris reflects 96 percent of the light that falls on it, which is even brighter than fresh snow on Earth. ESO said this bright surface makes Eris one of the most reflective objects in the Solar System, along with Saturn's icy moon.
“This layer of ice could result from the dwarf planet´s nitrogen or methane atmosphere condensing as frost onto its surface as it moves away from the Sun in its elongated orbit and into an increasingly cold environment,” Emmanuel Jehin, who contributed to the study, said in a press release.
The new observations allow the astronomers to estimate that the surface temperature of Eris is -396.4 degrees Fahrenheit on the side of the planet that faces the sun.
“It is extraordinary how much we can find out about a small and distant object such as Eris by watching it pass in front of a faint star, using relatively small telescopes," Sicardy said in a press release. "Five years after the creation of the new class of dwarf planets, we are finally really getting to know one of its founding members."
Image 1: This artist's impression shows the distant dwarf planet Eris. New observations have shown that Eris is smaller than previously thought and almost exactly the same size as Pluto. Eris is extremely reflective and its surface is probably covered in frost formed from the frozen remains of its atmosphere. Credit: ESO/L. CalÃ§ada
Image 2: This artist's impression shows the distant dwarf planet Eris in the distance with its moon Dysnomia in the foreground. New observations have shown that Eris is smaller than previously thought and almost exactly the same size as Pluto. Eris is extremely reflective and its surface is probably covered in frost formed from the frozen remains of its atmosphere. Dysnomia appears to be a darker and less reflective body. Credit: ESO/L. CalÃ§ada
Image 3: This artist´s impression shows the shadow of the dwarf planet Eris as it was crossing the Earth during the occultation during November 2010. The regions along the path saw a faint star briefly disappear as its light was blocked by Eris. Studies of where the event was seen, and for how long, have allowed astronomers to measure the size of Eris accurately for the first time. Surprisingly, they find it to be almost exactly the same size as Pluto and that it has a very reflective surface. Credit: ESO/L. CalÃ§ada
On the Net:
- Video 1 - Principle of the Occultation
- Video 2 - Shadow Path Of Dwarf Planet Eris
- Video 3 - Dwarf Planet Eris and its Moon Dysnomia
- Video 4 - Dwarf Planet Eris During the Occultation