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Time lapse photo of the movement of 2012 VP113 (color digitally added)

Time lapse photo of the movement of 2012 VP113 (color digitally added)

Astronomers today announced the discovery of a new dwarf planet at the edge of the solar system. Until the appropriate nomenclatural bodies settle on a snappier name, the tiny body will be known by the unwieldy moniker of 2012 VP113. The little planetoid is estimated to measure about 450 kilometers in diameter (so it is much smaller than other plutoids like Haumea (which is approximately 2,000 km x 1,500 km x 1,000 km). Speaking of Haumea, which has a mysterious pink spot, the new object (which I’ll call VP113, for short) is also suspected to be light pink because radiation causes the frozen gases to decay to that color.

Even when it is closest to the sun, the little planetoid is still 12 billion kilometers (7.4 billion miles) distant from our home star–but at the farthest extent of its orbit 2012 VP113 is a whopping 70 billion kilometers (44 billion miles) from Sol. That’s almost a thousandth of a light year! The irregular orbit takes 44,000 Earth years to complete—which means one year there is a very long time!

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You might be wondering why I am taxing your brain with obscure snowballs, but, astronomers are very interested in VP113 because of what it might reveal about the origins of the solar system. In 1951, the Dutch-born astronomer, Gerard Kuiper, predicted the existence of a vast cloud of icy objects at the remote edge of the solar system. The Kuiper belt has indeed been discovered—it is a belt of dust and icy objects approximately between Neptune and Pluto. In 1950, a Dutch astronomer, Jan Hendrik Oort revived an idea from the 1930s (from Estonian Ernst Öpik) that there was a huge spherical cloud of comets, vapor, and icy planetoids at the edge of the solar system—beyond even the orbits of miniature planets Eris, Sedna, and VP113. [I don’t know why all the scientists who theorized about the solar system’s icy edges were northern Europeans].

kuiper_oort.en

The discovery of VP113 proves the existence of the inner Oort cloud and provides astronomers with a source of information about the objects in the Oort cloud. Additionally the extremely strange orbits of VP113 and Sedna begin to suggest that an alien star disturbed the Oort cloud in the past—or that there may still be an Earth sized planet at the true edge of the solar system.

The Dwarf Planet Haumea

The Dwarf Planet Haumea

Haumea is a dwarf planet located in the Kuiper belt.  The little planetoid was discovered in December 2004 by a team of Caltech astronomers.  It is about a third the size of Pluto.  The team initially called it “Santa” but, in keeping with the IAU’s naming convention for Kuiper belt objects they eventually named the worldlet after a matronly fertility goddess from Hawaiian mythology.

Artist's conception of Haumea and its pink spot

Artist’s conception of Haumea and its pink spot

Although Haumea is typical of other dwarf planets in the Oort cloud in that it is a hunk of rock covered with ice, there are a couple of very unique things about the body.  Most notably Haumea is shaped like a lozenge (as opposed to being mostly spherical like other planets).   Astronomers believe that Haumea has sufficient gravity to overcome the compressive strength of its material.  In other words it chould be approximately spherical, however the planet is rotating with such velocity that it has become spindle shaped—like a water balloon thrown in a rifling spiral.

2003EL61art

The extreme rapidity of Haumea’s rotation is its other defining characteristic.  It rotates more rapidly than any planetlike object with a diameter greater than 100 kilometers.   Haumea rotates completely every 3.9 hours so days there are incredibly short (although its huge orbit takes 283 years to complete—so years are long).  It is believed that Haumea’s breakneck spin comes from a titanic collision with some other Oort belt object.  Haumea’s two dinky moons were probably also created by the impact.  Haumea has a large red spot on it–perhaps because of the presence of minerals–or the fractured perturbance left by an impact.

Artist's Interpretation of Sedna (Credit: Gemini artwork by Jon Lomberg)

After the discovery of Pluto in 1930, there was a long hiatus in discovering objects of comparable size. Then in 2003, a team of astronomers led by Mike Brown of Caltech discovered a distant icy sphere which was quickly heralded as “the tenth planet.”  Mike Brown announced the discovery on his website along with his team’s rationale for naming the object.  He wrote “Our newly discovered object is the coldest most distant place known in the Solar System, so we feel it is appropriate to name it in honor of Sedna, the Inuit goddess of the sea, who is thought to live at the bottom of the frigid Arctic Ocean.

It turns out that Sedna is only one of many similar snowball-like planetoids beyond Neptune.  In fact, Ferrebeekeeper has already described the dwarf planet Eris (named after the Greek goddess of Strife) which is the largest currently known Kuiper belt object.  Sedna was the first to be discovered since Pluto and it sparked a debate about such objects which ultimately resulted in Pluto’s downgrade to dwarf planet.  Sedna also has some unique features which make it remarkable in its own right.

The orbit of Sedna (red) set against the orbits of Jupiter (orange), Saturn (yellow), Uranus (green), Neptune (blue), and Pluto (purple)

Sedna takes 11,400 years to complete its orbit around the sun and its bizarre highly elliptical orbit has given rise to much conjecture among astronomers.  Although some astronomers believe it was scattered into a skewed orbit by the gravitational influence of Neptune, other astronomers believe it originated in the inner Oort cloud and was never close enough to Neptune to be affected by the giant’s gravity.  Some scientists speculate that its lengthy orbit may have been caused by a passing star (perhaps from the sun’s birth cluster).  A few theorists have gone one step further and conjectured that Sedna is from a different solar system and was captured by our Sun billions of years ago.  A final school contends that Sedna is evidence of an unknown giant planet somewhere in the depths of space (!).

A photo of Sedna taken from a powerful telescope on Earth

We don’t know much about Sedna except that is probably 1,200–1,600 km in diameter and that its surface is extremely red.  After Mars, Sedna is one of the reddest astronomical objects in our solar system.  This color comes from the profusion of tholins covering the methane and nitrogen ice of which the little world is formed.  Tholins are large, complex organic molecules created by the interaction of ultraviolet light on methane and other simple hydrocarbons.  It is believed that early Earth (prior to obtaining an oxidizing atmosphere) was rich in Tholins and they are one of the precursors to the rise of life.

Ceres (optimized image from the Hubble Space telescope)

Today’s post topic is located in the depths of space far far away from the bats, pumpkins, and haunted deserts I have been writing about for October. The dwarf planet Ceres is located in the midst of the asteroid belt between Jupiter and Mars.  The only dwarf planet in the inner solar system, Ceres is only 950 km (590 miles) in diameter, but it is sufficiently large to have become spherical from its own gravity (and it is by far the largest asteroid). Named after Ceres (Demeter), the mythological goddess of growing things whose daughter was abducted by Hades and who gave the secrets of agriculture to humankind through the farmer Triptolemus, the dwarf planet was discovered in 1801 by Italian astronomer Giuseppe Piazzi, a Roman Catholic priest of the Theatine order.  Ceres was the first asteroid to be discovered and it comprises a third of the asteroid belt’s total mass.

A comparison of the sizes of the Earth, Moon, and Ceres

The nebular hypothesis proposes that the solar system formed as a great cloud of space dust and gas coalesced into a disk which then further coagulated into small clumps, then into planetesimals, then into moon-sized planetary embryos, and finally into planets. Ceres is one of the few (or maybe the only) planetary embryos which formed four and a half billion years ago but somehow did not get smushed together with other like bodies to form a planet or hurled off into deep space. The dwarf planet probably consists of a rocky core surrounded with an icy mantle of frozen water.  Ceres is believed to contains 200 million cubic kilometers of water–more fresh water than in all the lakes, rivers, clouds, swamps, ponds (and everything else) on Earth. The Hubble telescope has photographed several mysterious surface features on Ceres including a dark spot believed to be a crater (now informally named after Piazzi) and several bright spots, the nature of which is unknown.

Image of the bright spots on Ceres (taken by the Hubble Space telescope)

Astronomers are profoundly curious about Ceres and hope to better understand the history of the solar system by examining this surviving planetary embryo.  Additionally, the chemical makeup of Ceres is similar to that of Earth. Scientists seeking extraterrestrial life have concentrated on Europa and Mars, but Ceres is next on their short list.

Astronomers will soon have some of their answers about Ceres.  The asteroid probe Dawn is currently orbiting the asteroid Vesta–but its mission there is scheduled to end in July of 2012.  At that point Dawn will power up its ion thrusters and fly to Ceres. In February of 2015 Dawn will enter permanent orbit around the little planet and we will finally have some of our answers.

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