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  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.

August 2014 night sky

—Charlie Christmann

Neptune

Neptune is the outermost “official” planet in our solar system. It orbits thirty times farther from the sun than Earth taking 164.8 years to complete its orbit. On September 23, 1846, Urbain Le Verrier and Johann Galle used mathematical calculations to predict the location of an unknown planet perturbing Uranus’ orbit. The planet was discovered when a student at the Berlin Observatory used drawings of the night sky and current observations to locate an object that had moved slightly from its charted location.

Interestingly, Galileo made drawings of the sky in December 1612 that showed Neptune. Unfortunately, the planet had just started its retrograde motion and appeared stationary in the sky. Galileo falsely assumed Neptune to be a star and is not credited with the discovery.

This month, Neptune can be found in the constellation Aquarius, very near the place it was observed at its discovery. And since its 1846 discovery, Neptune has made just one orbit of the sun.

If you want to look for this blue orb, you will need a telescope. Even though it is at opposition, closest to Earth and in line with Earth and the sun, it is still very dim at magnitude 7.8, about seven times dimmer than good eye sight under dark skies can see. On August 15, at 2:00 a.m., Neptune will be due south about 45 degrees above the horizon.

New Horizons

Pluto officially lost its status as the ninth planet in our solar system in 2006; however, some astronomers still dispute that decision. That controversy may be resolved in less than a year as NASA’s New Horizons spacecraft speeds toward a rendezvous and fast flyby of Pluto. The probe is currently near the orbit of Neptune, though Neptune is nowhere close, and within three hundred million miles of its target.

Between 1979 and 1999, Pluto orbited closer to the sun than Neptune. Its orbit is much more elliptical than the inner planets, is inclined 17 degrees to orbits of the other planets, and needs 248 years to complete. Since 1978, five moons have been discovered: Charon (1978), Hydra (2005), Nix (2005), Kerberos (2011), and Styx (2012). Charon is more than half the size of Pluto, leading some to call this a dual dwarf planet system with three moons.

Since its launch in 2006, New Horizons has made its way past Jupiter in 2007 for a boost in velocity and a change in its direction. When it reaches Pluto, it will not have much time to make its observations—it will be moving at more than thirty thousand miles per hour with respect to the Pluto.

From there, New Horizons will attempt to observe other objects in the icy Kuiper belt, a region believed to hold the source of many comets and perhaps several hundred dwarf planets. After that mission ends, it is hoped that there will be enough power to observe the heliosphere before it escapes the solar system into interplanetary space.

Rosetta

Another spacecraft, launched in March of 2004, is on a mission to catch up with, and orbit, comet 67P/Churyumov-Gerasimenko (no, I can’t pronounce it either). The European Space Agency’s Rosetta mission is within a month of its close encounter. The spacecraft is close enough to begin to send back detailed images of the comet’s 2.2×2.5 mile nucleus.

The plan is to orbit the comet’s nucleus in August, then send down a small lander in November to sample the surface. Rosetta is currently about halfway between Mars and Jupiter, inbound toward the sun. Rosetta will accompany the comet as it rounds the sun in July 2015.

A recent image, received in mid-July at a distance of about 7,450 miles, shows the task of finding a landing site is going to be more difficult than planned—67P is no ordinary comet. It appears to be two objects fused together. Scientists do not have an explanation, yet, for its weird shape, but over the next month, as Rosetta gets closer to orbiting, more details may give us some clues. If not, perhaps, in November, the lander will offer some information.

Today, the comet is located in the constellation Sagittarius and is a very dim 19th magnitude object. It is not expected to be visible without a telescope, so we will need to rely on our robotic eyes to enjoy this comet.

More information about the Rosetta mission is available from NASA at rosetta.jpl.nasa.gov and the ESA at sci.esa.int/rosetta/. Keep watching the websites; the ESA has just announced that the arrival of Rosetta will be webcast on August 6. Specifics will be announced later.

 
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