Eris, the largest dwarf planet known, was discovered in an ongoing survey at Palomar Observatory’s Samuel Oschin telescope by astronomers Mike Brown, Chad Trujillo (Gemini Observatory), and David Rabinowitz (Yale University).

In Greek mythology, Eris is the goddess of  warfare and strife. She stirs up jealousy and envy to cause fighting and anger among men. At the wedding of Peleus and Thetis, the parents of the Greek hero Achilles, all the gods with the exception of Eris were invited, and, enraged at her exclusion, she spitefully caused a quarrel among the goddesses that led to the Trojan war.

In the astronomical world, Eris stirred up a great deal of trouble among the international astronomical community when the question of its proper designation led to a raucous meeting of the IAU in Prague.

At the end of the conference, IAU (International Astronomical Union)  members voted to demote Pluto and Eris to dwarf-planet status, leaving the solar system with only eight planets.

The satellite or moon of Eris has received the official name Dysnomia, who in Greek mythology is Eris’ daughter and the demon spirit of lawlessness. As Dysnomia is a bit of a mouthful, its always abbreviated simply as satellite Dy, for short.

As promised for the past year, the name Xena (and satellite Gabrielle) were simply placeholders while awaiting the IAU’s decision on how an official name was to be proposed.

As that process dragged on, however, many people got to know Xena and Gabrielle as the real names of these objects and are sad to see them change.

This new dwarf planet is the largest object found in orbit around the sun since the discovery of Neptune and its moon Triton in 1846. It is larger than Pluto, discovered in 1930.

Like Pluto, the new dwarf planet is a member of the Kuiper belta, (swarm of icy bodies beyond Neptune in orbit that orbit around the sun). Until this discovery Pluto was frequently described as "the largest Kuiper belt object” in addition to being a dwarf planet. Pluto is now the second largest Kuiper belt object, while this is the largest currently known.

The dwarf planet is the most distant object ever seen in orbit around the sun, even more distant than Sedna, another dwarf planet discovered almost 2 years ago.

Eris is almost 10 billion miles from the sun and more than 3 times more distant than the next closest planet, Pluto .scientists think that the bright surface and uniform white coloring of the planet both have the same cause.

In the last less than ten years scientists say the planet is as far away from the sun as it ever gets, and thus as cold as it ever gets.

At this distance from the sun even the planet’s atmosphere is frozen solid. (In fact if the earth was to be taken that far away from the sun its atmosphere would freeze solid, too!).

In 280 years the planet will be the closest it ever gets -- a factor of almost 2.6 times closer. The absolute temperature on the planet will rise over the next 280 years by a factor of  1.6 (which is the square root of 2.6).

The current temperature of (a quite cold) 405 degrees below zero will be but a distant memory at this point when the temperatures will be a balmy 360 degrees below zero.

While both of these temperatures seem frigid beyond imagination, to methane and nitrogen (the likely components of the atmosphere of the planet eris), the difference between the two is the difference between frozen solid and evaporating into the atmosphere and takes more than twice as long to orbit the sun as Pluto.

The diameter of Eris has been measured to be 2,397 km, give or take 100 km, using images from the Hubble Space Telescope). The size of an object depends on its absolute magnitude and the albedo (the amount of light it reflects). Although resolving such small objects is at the very limit of Hubble’s capabilities, sophisticated image processing techniques used by scientists such as deconvolution (a software-based process by which one can re-focus an out of focus image.

Deconvolution occurs after image acquisition, and uses nearest-neighbor algorithms to extract information out of blurred regions of an image to clean up these regions,  they then appear to be closer to, if not actually in the same plane of focus as the rest of the image can be used to measure such angular sizes fairly accurately).

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