Discovery! Possible Dwarf Planet Found Far Beyond Pluto’s Orbit

What is a dwarf planet? Some astronomers have been asking that question after Pluto was demoted from planethood almost a decade ago, partly due to discoveries of other worlds of similar proportions.

Today, astronomers announced the discovery of 2012 VP113, a world that, assuming its reflectivity is moderate, is 280 miles (450 kilometers) in size and orbiting even further away from the sun than Pluto or even the more distant Sedna (announced in 2004). If 2012 VP113 is made up mostly of ice, this would make it large (and round) enough to be a dwarf planet, the astronomers said.

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CrazyNeutrino said:

Discovery! Possible Dwarf Planet Found Far Beyond Pluto’s Orbit

What is a dwarf planet? Some astronomers have been asking that question after Pluto was demoted from planethood almost a decade ago, partly due to discoveries of other worlds of similar proportions.

Today, astronomers announced the discovery of 2012 VP113, a world that, assuming its reflectivity is moderate, is 280 miles (450 kilometers) in size and orbiting even further away from the sun than Pluto or even the more distant Sedna (announced in 2004). If 2012 VP113 is made up mostly of ice, this would make it large (and round) enough to be a dwarf planet, the astronomers said.

“First, a bit about 2012 VP113. Its closest approach to the Sun is about 80 astronomical units … The detection of 2012 VP113 confirms that Sedna is not an isolated object; instead, both bodies may be members of the inner Oort Cloud”.

Let me start the reply by taking a look at Sedna. Sedna has an orbit of 11,400 years, an orbit that ranges from 76.4 AU at closest approach to a massive 937 AU at greatest distance. It has a diameter of 1000 km. The distance of 937 AU is very close to the start of the Oort cloud.

2012 VP113 has an orbit ranging from 80.6 to 446 AU, a little closer.

Now let’s look at data of the minor planet centre for other long period objects. (I’ll have to do that later)

> Now let’s look at data of the minor planet center for other long period objects. (I’ll have to do that later)

Object , Perihelion(AU) , Aphelion(AU)
2013 BL76 , 8.374 , 2482
2012 DR30 , 14.542 , 2406
2013 AZ60 , 7.908 , 2008
2006 SQ372 , 24.172 , 1487
2000 OO67 , 20.791 , 1106
Sedna , 76.136 , 989
…
2012 VP113 , 79.852 , 472

That makes Sedna the 6th furthest known minor planet (by semi-major axis), and 2012 VP113 is the 13th nearest. So, what’s special about 2012 VP113 ?

Well, one answer is that 2012 VP113 is the second brightest (absolute magnitude), and therefore second largest, of the distant minor planets. To get any brighter you have to go much closer, to
2005 QU182 , 36.932 , 185

The other answer, and the one that really sets 2012 VP113 apart, is that with a perihelion of 79.852 it’s the Solar System object with the largest perihelion. ie. it has the furthest closest distance from the Sun of any known minor planet. Sedna comes second.

Could 2012 VP113 really be a dwarf planet? Here I look at http://en.wikipedia.org/wiki/List_of_possible_dwarf_planets

Nothing with an absolute magnitude exceeding 5 could be a dwarf planet. 2012 VP113 has an absolute magnitude of 4.1.

Vesta is not a dwarf planet despite its absolute magnitude of 3.2. Ceres is, with its absolute magnitude of 3.36. But rocky asteroids have a much higher albedo than objects from the outer solar system, so outer-solar-system objects (trans-neptunian and scattered disk) can be dwarf planets at larger absolute magnitude. The The International Astronomical Union (the bastards who demoted Pluto) have only accepted four other outer-solar-system objects as dwarf planets, those with an absolute magnitude below 1. They should at least by now also have added in Sedna, 2007 OR10, Orcus, Quaoar, Ixion, 2002 TX300 and 2002 AW197. Lets picket the next meeting of the IAU.