Asteroids have been hot this week. Just days after discovering the first asteroid with rings, astronomers reported the discovery of a new dwarf planet that orbits farther from the sun than anything else ever seen. It’s called 2012 VP113, but the discovery team prefers the more playful ‘VP’ or ‘Biden’ for short.
2012 VP113 gets no closer than 7.4 billion miles or 80 times Earth’s distance from the sun. That’s more than twice Pluto’s distance. But the mind reels when you realize that 2012 VP113 loops out to 44 billion miles (70 billion km) distance when at it most distant point from the sun plying an orbit that takes 4,000 years to complete!
Assuming average reflectivity, 2012 VP113 is 280 miles (450 kilometers) in diameter, potentially placing it in the dwarf planet category like Pluto and several other largish solar system objects too small to be planets but large enough for gravity to have crunched them into spherical shapes.
‘Biden’ joins the previous distance record holder, Sedna, as one of only two bodies found in the inner Oort Cloud, a reservoir comets, some of which eventually find their way into the inner solar system to the delight of skywatchers.
“The detection of 2012 VP113 confirms that Sedna is not an isolated object; instead, both bodies may be members of the inner Oort Cloud, whose objects could outnumber all other dynamically stable populations in the Solar System,” authors Scott Sheppard and Chadwick Trujillo wrote in their discovery paper, published this week in Nature.
The known solar system is divided into half a dozen zones: the inner, rocky planets which includes the Earth; the inner asteroid belt where the traditional rocky asteroids reside; the giant outer planets; the Kuiper Belt, reaching from 2.8-4.6 billion miles from the sun, that includes Pluto and countless other icy asteroids; the inner Oort Cloud that Sedna and ‘Biden’ call home and finally the remote outer Oort Cloud located between 5,000 and 100,000 times Earth’s distance from the sun.
Billions of icy, inert comets are believed to exist in this last, more remote region of the solar system. Disturbed by the gravity of passing stars, Oort Cloud comets can “drop in” to the inner solar system. Their orbital periods can easily be a million years or longer.
But back to 2012 VP113 and Sedna. Because only a tiny amount of sky has been examined for faint objects like these two planetary dwarfs,Trujillo and Sheppard estimate that some 900 objects with similar orbits and up to 620 miles (1000 km) across are still waiting to be found.
The total population of the inner Oort Cloud may be even larger than the inner asteroid belt and Kuiper Belt combined. Most intriguingly, some of these objects could be as big as Earth or Mars. Only their extreme faintness makes their discovery a painstaking process, says Sheppard.
The similarity in the orbits of Sedna, 2012 VP113 and several other objects in the Kuiper Belt suggests that an unknown massive body perhaps even larger than Earth exerts a gravitational influence on the bunch. But before Planet X aficionados jump out of their seats, don’t forget the results of NASA’s WISE satellite survey. Seeing the sky in infrared light, which can reveal even cold, dark objects at great distances across the solar system, nothing even close to a planet-sized object was discovered.
WISE’s two complete infrared sweeps of the sky found that no object the size of Saturn or larger exists out to a distance of 930 billion miles from the sun and no object larger than Jupiter exists out to 2.4 trillion miles. That doesn’t negate the possibility that something Earth-sized remains hidden in that profound darkness.
Who knows?? What’s perhaps most fascinating in all of this is how our view of the solar system has matured from nine planets to a much more complex place with room for many more possibilities than we might have imagined a generation ago.