Distant dwarf planet ‘Snow White’ may be third largest of its kind

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The orbit of 2007 OR10 compared to the orbit of Eris, Pluto, and the outer planets
[credit: Gravity Simulator by Tony Dunn]

What the report doesn’t say is that the second largest dwarf planet Eris is a close neighbour of “Snow White”. Eris completes 52 orbits of the Sun to every 53 of “Snow White”. Both have highly inclined orbits.

A faraway object nicknamed “Snow White” is considerably larger than scientists had thought, and is in fact the third-largest dwarf planet in the solar system, a new study suggests.

Snow White is about 955 miles (1,535 kilometers) in diameter rather than 795 miles (1,280 km) wide as previously believed, according to the new study. That makes it the largest still-unnamed object in our solar system, NASA officials said. (The dwarf planet has not yet been formally named and currently goes by the placeholder designation 2007 OR10.)

NASA released a new video of the dwarf planet Snow White along with its new size figures. If the new measurement is accurate, the only known dwarf planets bigger than Snow White are Pluto and Eris, which are 1,475 miles (2,374 km) and 1,445 miles (2,236 km) across, respectively.

A mysterious dwarf planet

Snow White orbits the sun every 547.5 years on an extremely elliptical path, getting as close to the star as 33 astronomical units (AU) and as far away as 101 AU. One AU is the average distance from Earth to the sun — about 93 million miles, or 150 million km. For perspective, Pluto orbits the sun at an average distance of 39.5 AU, and completes one lap every 248 years.

The size revision should help researchers better understand Snow White’s composition and evolution, researchers said. For example, the object probably has an even darker surface than scientists had thought (because a larger amount of area is reflecting the same amount of light).

Artist’s illustration of 2007 OR10, nicknamed “Snow White.” Astronomers suspect that its reddish color is due to the presence of irradiated methane.

Previous observations had suggested that Snow White is reddish, perhaps because of the presence of methane ices. The new results bolster this interpretation, researchers said.

“Our revised larger size for 2007 OR10 makes it increasingly likely the planet is covered in volatile ices of methane, carbon monoxide and nitrogen, which would be easily lost to space by a smaller object,” lead author András Pál, of Konkoly Observatory in Budapest, Hungary, said in a statement. “It’s thrilling to tease out details like this about a distant, new world — especially since it has such an exceptionally dark and reddish surface for its size.”

The team also determined that the object is rotating extremely slowly, completing one spin every 45 hours. Snow White’s surface brightness also appears to vary from place to place, researchers said.

Full Space.com report: Mysterious Dwarf Planet ‘Snow White’ Much Bigger Than Thought: Study
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A few facts:
2007_OR10
Aphelion 100.84 AU (15.085 Tm) (Q)
Perihelion 33.015 AU (4.9390 Tm) (q)
Semi-major axis 66.925 AU (10.0118 Tm)
Orbital period 547.51 yr (199,978 d)
Inclination 30.9434° (i)

ERIS
Aphelion 97.651 AU
Perihelion 37.911 AU
Semi-major axis 67.781 AU
Orbital period 558.04 yr (203,830 d)
Inclination 44.0445°