Faint Mercury can be spotted during the first week in July. Look for it very low in the west shortly after sunset. It becomes dimmer and it sinks lower toward the horizon each evening and soon disappears into the glare of the sun.
Venus rises in the eastern predawn sky. It appears close to the much fainter red giant star Aldebaran during the first half of the month.
Mars appears in the west-southwest sky as darkness falls. The Red Planet sets around midnight and becomes progressively dimmer each week.
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Bright Jupiter rises in the east-northeast about 3 a.m. early in July. It remains higher in the eastern predawn sky than brilliant Venus. Throughout the month, these two bright planets will continue to pull farther apart.
Saturn, in the southwestern evening sky, moves closer to Mars each day throughout the month. The blue giant star Spica remains close to Saturn all month long. On July 25, the first quarter moon will form a triangle with Saturn and Spica.
PLUTO - WHAT
HAPPENED?
"The U.S. has a spacecraft on its way to Pluto, on to the Kuiper Belt and on to the stars" - Alan Stern, American planetary scientist
For decades, schoolchildren the world over have been taught that there were nine planets encircling our sun. But, Pluto is no longer considered a planet like the other eight planets in the solar system. Advanced technology in the field of astronomy has enabled astronomers to discover objects farther out beyond the orbit of Pluto that are even larger and more massive. This is just one more example of how science changes our understanding of reality as new evidence becomes available. Science, eventually, is self-correcting.
Compared to Earth's diameter of 7,926 miles, Pluto is only 1,485 miles across. This makes Pluto smaller than the moons Ganymede, Titan, Callisto, Io, Earth's moon, Europa and Triton. Also, Pluto isn't very massive, weighing in at only 0.24 percent the mass of Earth. Because of its tiny size and mass, Pluto has been unable to clear out the material near its orbit. For this reason, the International Astronomical Union redefined its definition of "planet" and then demoted Pluto from planet to dwarf planet in 2006.
The IAU's new definition of a planet is an object in our solar system that orbits the sun and is sufficiently large to have become round due to the force of its own gravity. Besides those two conditions, the object must dominate its neighborhood, meaning that it has sufficient gravity to sweep up comets, asteroids and other debris, thereby clearing a path along its orbit. Since Pluto orbits among the icy debris of the Kuiper Belt and has not been able to clear other objects from its orbital neighborhood, it was demoted to the status of a dwarf planet. The only requirements for a dwarf planet are that it is round and it orbits the sun. Pluto actually revolves around the sun in a highly eccentric orbit, compared to the eight classical planets.
It takes Pluto 248 years to complete one full revolution around the sun. Not only is its orbit not within the same plane as the rest of the solar system, its orbit is an elongated ellipse compared to the nearly circular orbits of the eight classical planets. The average temperature on Pluto is 44 degrees above absolute zero. Its thin atmosphere of nitrogen, methane and carbon dioxide freezes onto the tiny dwarf planet's surface when farthest from the sun.
Because it is so small and so remote, Pluto is much too faint to be seen without optical aid. In fact, when looking through all but the largest telescopes, Pluto looks just like a star. The only way amateurs can be sure that they are actually seeing Pluto is to observe the planet's movement against the background of "stationary" stars over successive nights. Pluto will be the only object in the field of view that shows movement from night to night.
Pluto still holds many secrets from us, but this will change in just a few years. In January 2006, NASA launched the New Horizons spacecraft to study Pluto, its moons and objects in what is called the Kuiper Belt. This is a disk-shaped region beyond the orbit of Neptune containing billions of icy objects that range in size from tiny particles to Pluto or larger sized bodies. By launching the spacecraft at that time, New Horizons was able to take advantage of a gravity assist from Jupiter, passing the giant planet at more than 50,000 mph. After 10 years and more than 3 billion miles, the spacecraft is due to reach Pluto in July 2015. Currently, plans are to steer the probe to about 6,000 miles from Pluto. At that distance, if all goes well, cameras onboard the spacecraft should be able to capture surface features as small as 200 feet across. It is just the fifth probe to navigate through interplanetary space so far from the sun. The New Horizons science team wants the probe to reach Pluto as soon as possible because, since 1989, the planet has been moving farther from the sun and, therefore, getting colder. The scientists want the spacecraft to arrive there before Pluto's atmosphere freezes out onto its surface.
Editor's note: This monthly guide to the stars is from the Marshall Martz Memorial Astronomical Association, the Southern Tier Astronomy Recreation Society and The Post-Journal. For further information, contact the M.M.M.A.A. at www.martzobservatory.org or S.T.A.R.S. at www.UpStateAstro.org/stars/stars.html.