July Skies

Mercury is positioned between Earth and the sun and cannot be seen during the first part of July. During the last two weeks of the month, this little planet can be spotted to the lower left of bright Venus, near the east-northeast horizon in the pre-dawn sky.

Brilliant Venus shines as the “Morning Star,” low in the east-northeast before sunrise. Although it is not the planet closest to the sun, Venus is the warmest planet in our solar system. Its dense atmosphere traps heat, resulting in surface temperatures that can reach 870 degrees F.

Reddish Mars appears in the late evening twilight sky. Look for it low in the southwest, near dimmer Spica, a blue giant star. Observe the difference in colors between these two objects.

Jupiter is behind the sun in relation to Earth and cannot be seen this month.

Saturn glows in the south-southwest as the evening twilight fades. Throughout the month, Mars approaches closer and closer to the ringed planet. Saturn is the most distant planet which can be seen without optical aid.

The Delta Aquarids Meteor Shower is only rated as an average shower but this year a thin crescent moon will set early in the evening, ensuring a dark sky for viewing the show. It peaks this year on the night of July 28-29. Best viewing will be from a very dark site between midnight and the predawn hours.

ANTARCTIC

ASTRONOMY

Selecting a site to build a major new observatory is not an easy job and several important things have to be taken into account. The level of “seeing” at the site is probably the most important consideration. Poor seeing is usually the result of warm and colder air mixing and flowing together, causing air turbulence. A site with excellent seeing will produce sharp images while the images taken at a site with poor seeing will be blurry. However, there are other factors to consider. The percent of nights with cloud cover, annual rainfall and humidity levels, seismic activity, the amount of air pollution, average wind speeds, and many other things have to be considered. Usually, just to make life interesting, the least comfortable and most remote places on Earth turn out to be the most suitable astronomical sites.

Antarctica is the highest, coldest, windiest and most forbidding continent on Earth. So, as luck has it, the world’s best site for astronomical viewing is located high on the Antarctic plateau. This site, called Dome C, produces better seeing conditions than the best observatories in Chile, the Canary Islands and Hawaii. Dome C has extreme cold and low humidity, very little air pollution, a high percentage of cloud free nights, and low infrared sky emission. These factors combine to produce astronomical viewing conditions that, in some wavelengths, are equal to those in space.

Although the Dome C region has the very best conditions for astronomical observations, the atmosphere above the Amundsen-Scott South Pole Station is nearly as good. Located at the South Pole, this site is a year-round facility that includes an observatory equipped to study solar astronomy, cosmology, neutrino and gamma ray astronomy, meteorology, cosmic rays, aurora observations, and high-altitude atmospheric studies.

Antarctica is also the best place in the world to find meteorites, those extraterrestrial objects that survive passage through our atmosphere and land on Earth’s surface. It is estimated that nearly 30,000 meteorites, each weighing over 3.5 ounces, strike Earth’s surface each year. The great majority of these sink in the oceans, which cover over 70 percent of Earth’s surface. Many of the meteorites that land in Antarctica become frozen into the vast ice sheets that gradually flow from the center of the continent toward the coastlines. In some regions, large patches of ice become stranded behind mountain ranges and eventually flow in an upward direction. When the ice becomes eroded by strong Antarctic winds, the meteorites are exposed and can be collected. Meteorites from the moon and Mars, after being buried in the ice for thousands of years, have been discovered in Antarctica.

Although most of Antarctica is a pristine environment, humanity has already contaminated certain regions. Some areas are loaded with old batteries, chemicals, rusting cables and pipes, asbestos, transformers and building materials. One example is Australia’s abandoned Wilkes Station, where over 3,000 rusting fuel drums, many still loaded with oil and various chemicals, are leaking hazards.

The problem at Wilkes has continued to grow over the past 45 years and it will take at least 10 years and many millions of dollars to clean it up. However, although an international agreement exists that all trash generated in Antarctica should be brought back to the country that generated it, the logistics and money required are astronomical.

Editor’s note: This monthly guide to the stars is from the Marshall Martz Mem-orial Astronomical Associa-tion and The Post -Journal and OBSERVER. For further information, contact the M.M.M.A.A. at www.martzobservatory.org.