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An independent monthly newspaper serving the community since 1988
  Night Sky
 

Enjoy the starry night skies
Be a considerate neighbor. Reduce nighttime glare.
Shield your outside lights downward.
Let the stars light up the night.

February 2016 night sky

—Charlie Christmann

The Outer Solar System

It was 86 years ago, on February 18, 1930, that New Mexican Clyde Tombaugh discovered a tiny pinprick of light had move between two images from his telescope. That point of light would, for a time, become the ninth planet in our solar system: Pluto.

In the 1840s, a French mathematician Urbain Le Verrier specialized in celestial mechanics, predicted that an eighth planet existed because Uranus had an orbit that could not be explained without the existence of something further out. Le Verrier calculated an orbit and current location for his predicted planet. The result was the discovery of Neptune.

In 1906, Percival Lowell founded the Lowell Observatory in Flagstaff and began looking for a suspected ninth plant, “Planet X”. By 1909, Lowell and William Pickering had calculated a possible location for their planet. Even with this prediction, no large planet was discovered by Lowell’s death in 1916. Unknown to Lowell, he had captured two images of a new planet in March and April of 1915, the one we know today as Pluto. There had been 14 other pre-discovery images made of Pluto, the earliest known image was taken in August of 1909. Pluto was officially named on May 25, 1930.

In keeping with the naming of planets, Pluto was named for the Greek god of the underworld. He was the son of Kronos and Rhea. After the Titians were overthrown, the universe was divided into three parts, each ruled by Pluto and his two brothers, Zeus and Poseidon. Pluto ruled his realm with his wife Persephone and his three-headed dog. He is also considered the god of jewels since these come from beneath the earth.

It soon became apparent that Pluto was not large enough to perturb Neptune’s orbit, yet a thorough search failed to find the missing “Planet-X.” As astronomers continued their explorations of the outer solar system, smaller bodies were found farther out than Pluto in a region known as the Kuiper Belt. These included Ceres, Pallas, Juno, and Vesta. In June of 2005, Cal Tech astronomers announced their discovery of Eris. This was the beginning of the end for Pluto’s planet status. Eris, though a bit smaller in size than Pluto, was more massive. These smaller bodies were reclassified as “dwarf planets”.

But, Pluto reigned large in 2015 with the images and data being received from the New Horizons spacecraft. While not all of the data collected by the probe will be received until later this year, Pluto has already given science some surprises. Pluto has a nitrogen atmosphere extending to almost one thousand miles above its surface. Giant glaciers of nitrogen, carbon monoxide, and methane ices flow from the heart-shaped Sputnik Planum region. Mountains of water ice, frozen as solid as granite, tower above the surface; some are possible cryogenic volcanos spewing a slushy mixture of ices. Much of the surface is spotted by pock marks—created by the sublimation of nitrogen ice. As for the color of Pluto, it is a reddish brown with a light gray heart-shaped region and yellowish North Pole.

Even after their exhaustive search of the outer solar system based upon Le Verrier’s and Lowell’s calculations, no Planet-X has been seen. Yet, as of January 20, 2016, new calculations are being made with the prediction of a large planet lurking in the outer regions of the Kuiper belt. Our solar system may still have a ninth planet. If this planet exists, modern predictions are for a planet at least ten times Earth’s mass in a 10,000 to 20,000 year elliptical orbit. The planet would never get closer than two hundred astronomical units to the sun (an astronomical unit is the average distance between the sun and the Earth). There are no images of this potential planet, yet astronomers need it to explain the perturbations in many of the other known Kuiper Belt objects. If it exists, the planet probably formed along with the outer gas giant planets, but got too near Jupiter and was flung to the neither regions of the solar system.

If a ninth planet, larger than Earth, but smaller than Neptune is out there, it may be difficult to spot, even with infrared telescopes. That far from the sun is a very cold and dark place. Some of the largest Earth-based telescopes are on the hunt. If anything is found, you will read about it here.

 
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