Download August 2013 - Joliet Junior College

AUGUST 2013 ASTRONOMY
From the Trackman Planetarium at Joliet Junior College
Venus dominates the western sky after sunset. At mid-August, Venus is 6 times
brighter than the brightest star (Sirius) and will continue to move to the east and
brighten until November. Saturn is a yellow-colored star low in the southwestern sky
after dark. Venus is moving toward Saturn and will be within 4 degrees of the ringed
planet at mid-September. Mars and Jupiter rise before the sun in the morning. Jupiter
will be back in the evening sky in November. Mars won’t be back in the evening sky
until next spring. Mercury is in the morning sky and will cross behind the sun on
August 24th.
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We are halfway through astronomical summer. The Celtic cross quarter day of
Lughnasadh is on August 1st although August 6th is halfway between the first day of
summer and the first day of fall. So, as to be expected, the summer sky is directly
overhead at mid-evening during August. Directly above are three bright stars that form
the summer triangle. They are Deneb, Altair, and the brightest of the three, Vega. The
Milky Way runs between these three stars and down to the horizon at Sagittarius - a
constellation that looks like a teapot. At the spout of the teapot is the black hole that is
in the center of our galaxy. To the right of Sagittarius is Scorpio which looks like a
scorpion. The Big Dipper has moved around and is now in the western sky after sunset.
In the northeastern sky is the “W’ that marks the constellation of Cassiopeia. To the
right of Vega is Hercules and the Hercules globular cluster. The globular cluster is
hundreds of thousands of stars in a tight group. It appears as a fuzz ball in binoculars.
The star Deneb in Cygnus is one of the summer triangle stars and is a huge star that is
more than 108 times larger than our sun. Distance estimations vary, but 1,700 light
years is about average. That means if you were on Deneb with a telescope large enough
to see Earth, you would see what was going on in the year 313. The light reflecting off
Earth, along with the light reflected off people and things on the Earth’s surface in the
year 300, is just arriving at Deneb. Low in the summer sky is the constellation of
Ophiuchus. Between November 30th and December 17th, the sun is in Ophiuchus and
yet it doesn’t appear on any astrological charts. Therefore, if you were born between
November 30th and December 17th you don’t have a horoscope.
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The Perseid Meteor shower peaks on the evening of August 12th. The meteor shower
should be active for a week before and a few days after the August 12th peak. The
Perseids are left over debris - normally about the size of a grain of sand - from the last
passing of Comet Swift Tuttle in 1992. In clear skies you can expect to see 60 to 80
meteors per hour. The meteors are small pieces of rock and/or stone that enter the
Earth’s atmosphere at 70 to 100 miles above the surface. When they encounter the
atmosphere they are traveling at about 132,000 mph and the friction causes them to
burn. Occasionally a large meteor will enter the atmosphere and create a fireball as it
crosses the sky. It was a fireball that exploded above Chelyabinsk in Russia last
February. (Trivia - some of the gold medals to be awarded at the 2014 Winter Olympics
will have a piece of the Chelyabinsk meteorite embedded in the gold.) The Perseid
Meteor Shower peaks after midnight and the best time to look is between 10:30 pm and
4:00 am on the 13th. Look low in the northeast after dark. The waxing crescent moon
will set about 10 pm and won’t interfere with meteor watching. If you go out to see the
meteors on the night of the 11th, look for the International Space Station crossing low in
the northwest sky at 8:50 pm.
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The full moon is on August 20th. The August full moon was called the Sturgeon moon
by the Native Americans because the large sturgeon fish of the Great Lakes and other
major lakes were more easily caught at this time of year.
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Neptune will be at opposition - its farthest from the Earth - on August 27th. Neptune
will be 2.7 billion miles from us. Neptune is barely visible in a medium size telescope.
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The sun starts August in the constellation of Cancer and on August 10th it moves into
Leo.
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The first public show of the new season is on September 3rd at 7:30 pm. The show is
about the seasonal sky. If the skies are clear, we will go outside after the show and tour
the real sky.
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The number of sunspots peaks every 11 years and we are at the peak for sunspot
activity this year. Unfortunately - and unexplainably - this has been the lowest sunspot
maximum in over 100 years.
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Art Maurer
Director -Trackman Planetarium
Joliet Junior College
([email protected])