Pluto is almost in the camera sights of the New Horizons deep space probe! It is scheduled to arrive on July 15. This event is especially exciting for me. I’ve had an endless fascination for the far off Dwarf planet all my life. It has caused me much frustration seeing Pluto in my pictures and through my telescope as a bright spot in a field of view filled with stars. I can only find it because it shifts position a bit each night.
It was originally discovered by Clyde Tombaugh in 1930 as the ninth planet of the solar system. In recent years it has been reclassified as a Dwarf planet. He spent several years comparing photographic plates taken nights apart, trying to find a small bright spot shifting position. Calculations suggested that something was gravitationally tugging at the orbit of Neptune, so there must be another planet out there in the area he was searching. Pluto is part of the Kuiper Belt, a collection of large and small debris that stretches from Neptune to the far reaches of the solar system.
Dim Pluto is 41 times the distance of the Earth to the Sun. Very little was known about it until the late 1970s. In 1978 planetary astronomers discovered that Pluto had a Moon. It orbited close to Pluto and at that distance, was very difficult to see. It was later named Charon. Our technology has advanced remarkably since then and investigation of their orbital interactions have revealed details on their mass, density, reflectivity (albedo) and even rough outlines of surface features.
One surprise was that Pluto had an outer layer of methane around a large core of rock. Objects out at that distance are expected to have a water ice outer layer and indeed, Charon has a small rocky core surrounded by ice. That could only happen as a result of a collision with a large object far back when the solar system was young. Pluto has a very thin atmosphere of methane and a polar cap. Its surface features don’t remain the same but seem to shift about. So far five moons have been found orbiting Pluto.
By far the biggest discovery that has resulted from studying Pluto is the existence of the Kuiper belt. The vast number of objects that were and are being discovered every day came as a surprise. Many of these orbiting objects are near Pluto in size and more are being found as our telescopes grow larger. Some are as large as 1000 kilometers and can, in their own right, be classified as Dwarf planets. They come in all compositions both standard and exotic.
From all these discoveries, many I don’t have space to describe, arose a push to send a probe out there to investigate what has become a very complex and complicated, even bizarre, celestial situation and region. New Horizons was launched in 2006 on its epic five billion kilometer journey. This year observations began in January and it has been taking pictures and measuring the makeup of the area surrounding Pluto. It will make its closest approach on July 15 when it passes between the orbit of Charon and Pluto. That’s pretty good aiming! I try to visualize it by picturing me sitting on a beach in Newfoundland with a six shooter and trying to hit a dime at the top of a building in Vancouver!
Huge amounts of data will be collected and transmitted to Earth but the mission won’t end there. New Horizons will continue on farther into the Kuiper belt where many more discoveries will be made.
There are several names for the full moon on July 1. One name is the Full Thunder Moon. Thunder storms are most frequent during this time of summer. Buck deer have their horns pop out of their foreheads this month too. Thus – we have the Full Buck Moon. Haying gets going too and we might as well add the Full Hay Moon to our list! There’s another full moon this month on the 31st and that happens once in a Blue Moon. As a matter of fact it is called a Blue Moon event and is suppose to happen rarely. Actually, it’s not all that rare! A truly rare event occurs when dust particles in the Earth’s atmosphere cause the Moon to appear blue in colour.
On July 3 the Earth is at Aphelion. That means it is at its farthest distance from the Sun. Remember that it is the tilt of the Earth as it orbits the Sun that causes our seasonal changes, not its distance from the Sun.
Looking west about an hour after sunset on July 4, you will see Venus and Jupiter about two degrees apart with the star Regulus above and to the left of the close pair.
On the 6th, Pluto is at opposition or its closest approach to the Earth.
Venus is at its brightest on July 10. It is at a staggering - 4.7 magnitude. Magnitude brightness increases as the number becomes lower. When a number goes negative, the object is very bright indeed.
On July 17, 18 and 19, the crescent Moon, Venus, Jupiter and Regulus are tightly grouped together shortly after sunset in the west.
Saturn is well placed all this month for observing.
Don’t forget to watch for news on the Pluto flyby of the New Horizons spacecraft.
By the way, whenever I observe Pluto through my telescope, I try to make out Mickey Mouse and his loyal dog Pluto. After all, Walt Disney named Mickey’s hound after Clyde Tombaugh’s discovery of distant Pluto.
The Beginner’s Observer’s Guide by Leo Enright is available at the Sharbot Lake Pharmacy or by contacting the Royal Astronomical Society of Canada www.rasc.ca/publications, subscriptions for our very own excellent Canadian astronomy magazine, Sky News, are also available from RASC..