Distant Wanderer

After a great journey, a long-hidden member of our solar system has returned. Not since the 9th century, when Charlemagne ruled as Emperor of the Holy Roman Empire and Chinese culture flourished under the Tang Dynasty, has this small icy world re-entered the realm of the outer planets.

This distant wanderer is among first of its kind discovered with data from the Dark Energy Survey (DES). Now officially known as 2013 TV158, it first came into view on October 14, 2013, and has been observed several dozen more times over the following 10 months as it slowly traces the cosmic path laid out for it by Newton’s law of gravitation. We see this small object move in the animation to the left, comprised of a pair of images taken two hours apart in August, 2014.

It takes almost 1200 years for 2013 TV158 to orbit the sun, and it is probably a few hundred kilometers across – about the length of the Grand Canyon.

In eight more years, it will make its closest approach to the sun – still a billion kilometers beyond Neptune. At this distance, the sun would shine with less than a tenth of a percent of its brightness here on earth, and would appear no larger than a dime seen from a hundred feet away.

That’s what high noon looks like on 2013 TV158.

Then it will begin its six-century outbound journey, slowly fading from the view of even the most powerful telescopes, eventually reaching a distance of nearly 30 billion kilometers before pirouetting toward home again sometime in the 27th century.

This object is just one of countless tiny worlds that inhabit the frozen outer region of the solar system called the Kuiper Belt, an expanse 20 times as wide and many times more massive than the asteroid belt between Mars and Jupiter. The dwarf planet Pluto also calls the Kuiper Belt its home. The orbits of Jupiter, Pluto and 2013 TV158 around the sun can be seen in the image to the lower right.

Scientists believe that these Kuiper Belt Objects, or KBOs, are relics from the formation of the solar system, cosmic leftovers that never merged into one of the larger planets. By studying them, we can gain a better understanding of the processes that gave birth to the solar system 4.5 billion years ago.

Because they are so distant and faint, KBOs are extremely difficult to detect. The first KBO, Pluto, was discovered in 1930. Sixty-two years would pass before astronomers found the next one. Astronomers have identified well over half a million objects in the main asteroid belt between Mars and Jupiter. To date, we know of only about 1500 KBOs.

DES is designed to peer far beyond our galaxy, to find millions of galaxies and thousands of supernovae, but it can also do much more. DES records images of ten specific patches of the sky each week between August and February. These images are a perfect hunting ground for KBOs, which move slowly enough that they can stay in the same field of view for weeks or even months. This allows us to look for objects that appear in different places on different nights, and eventually track the orbit over many nights of observations.

So far we’ve searched less than one percent of the DES survey area for new KBOs. Who knows what other distant new worlds will wander into view?

Det. D. Gerdes