Venus and Saturn are the showpieces in the western sky after sunset over the next few weeks.
Venus reaches its greatest brilliancy around July 12 at a dazzling magnitude of -4.6 making it the brightest nighttime object in the skies, second only to the Moon. In the telescope observers note the diminishing crescent phase and increase in apparent size of Venus. Over the month of July Venus will shrink from being a crescent 35 percent illuminated to nine percent lit.
Venus is in conjunction (pairs up) with Saturn on July 1 with the two planets just under one degree apart. The brilliant white radiance of Venus outshines the much fainter yellowish glow of the Ringed Planet by a brightness of nearly 100 times. As July begins Venus resides about 10 degrees above the western horizon an hour after sunset. Toward the end of July Venus will disappear into the twilight as seen from our northerly latitude once the sun goes down.
Saturn and Venus pair up once again in the morning sky in mid-October in the constellation of Leo the Lion.
As darkness falls Jupiter can be easily spotted low above the southern horizon. Its bright yellowish glow (magnitude -2.5) makes this giant planet stand out easily amongst the stars of the constellation of Ophiuchus. The orange coloured star Antares in Scorpius can be seen about five degrees below Jupiter. A small telescope will easily reveal the Galilean moons of Jupiter (Io, Europa, Ganymede and Callisto). The astronomer Galileo was the first to observe these satellites orbiting Jupiter with his telescope in 1610. This observation was the final proof that the sun was the center of the solar system rather than the Earth. Observers will find that the features of the Jovian atmosphere may not be as clear as in past years. This is due to the fact that Jupiter is located so far south (in declination) in the sky so the planet only manages to get 20 degrees above the horizon as seen from our latitude. This means that the light from Jupiter must pass through more of our atmosphere before it reaches us. The dust, humidity and pollution in the air can seriously degrade the image seen in the telescope.
The Red Planet Mars can be seen about 30 degrees above the eastern horizon an hour before sunrise by the middle of July. The reddish colour identifies the planet amongst the stars in the constellation of Aries. Mars will appear featureless in the telescope due to its greater distance and small apparent size at present. Observers will get much better views of the Red Planet as Mars approaches its opposition in December.
Look for the moon as a waning crescent about five degrees above Mars an hour before sunrise on July 9. A waxing gibbous moon can be seen to the lower left of the star Antares and Jupiter after sunset on July 25.
The Earth revolves around the sun in an
elliptical orbit so we are closer to the sun at one point and farthest at the
opposite point. On July 6 the Earth is
at its furthest distance from the sun (aphelion) at a distance of 152,097,053
km. Since we are tilted towards the sun
this time of year we receive more hours of sunlight each day warming the
northern hemisphere despite the increased distance from the sun. It is the Earth’s tilt towards the sun that
effects the seasons rather than the relatively small variation (3.3 percent) in
earth to sun distances. The Earth will
make its closest approach to the sun (perihelion) in six months on
Clear Skies
Ted Bronson