July 2012 Astronomy
From the Trackman Planetarium at Joliet Junior College
On July 4th, Earth will be 94.5 million miles from the sun, the farthest from the sun for the year
(aphelion). Since we will be farthest from the sun for the year, we will be orbiting the sun at the slowest speed for the year, a leisurely 66,000 miles per hour - 1,100 miles slower than in December. (It’s a law of physics that the farther you are from the object you are orbiting, the slower you move.) Ever since the
Summer Solstice on June 20th, we’ve been losing minutes of sunlight each day. At the beginning of July, most of the change will be in sunrise times. But after the first week in July, the sun starts setting earlier every day. During July, we will lose 44 minutes of daylight - 19 minutes of it in the evening.
Venus crossed the sun on June 5th and now is orbiting quickly to the west. Venus and Jupiter are in the eastern sky before sunrise during July. Saturn is still the highlight of the evening sky. The easiest way to find Saturn is to start with the Big Dipper which is overhead in the mid-evening. Follow the curve of the dipper’s handle to a bright star (Arcturus) and continue on until you reach two bright stars that appear less than one hand‘s width apart. The upper one of those two is Saturn. In mid-July, look to the west of
Saturn for Mars. Mars is orbiting to the east faster than Saturn and will catch up with the ringed planet at the end of July. Mercury was farthest east in its orbit on June 30th and is setting after the sun. During
July, Mercury will be orbiting back toward the sun and will pass below the sun on July 28th.
The Big Dipper is high in the sky at mid-evening during July. The two stars that mark the outer edge of the bowl are the pointer stars and if you follow them to the north, you come to Polaris or the North Star.
The North Star marks the end of the handle of the Little Dipper. Most of the stars in the Little Dipper are too dim to see from this area. The Big Dipper is not a constellation, but an asterism. An asterism is part of a constellation. The entire constellation is Ursa Major or the Big Bear. The three stars that make up the
Summer Triangle (Deneb in Vega, Altair in Aquila, and Vega in Lyra) are in the eastern sky in mid-July.
The Milky Way runs between those stars and is visible with binoculars. Just above where the Milky Way meets the southern horizon is Sagittarius - the Archer. Sagittarius looks like a Teapot! To the west of
Sagittarius is another easily recognized constellation - Scorpio the Scorpion.
The full moon in July is on July 3rd. The Native Americans referred to the July full moon as the Full
Thunder Moon.
The International Space Station will not be making any evening passes during July. Tiangong-1, the
Chinese space station will resume evening passes on July 20th. Tiangong-1 is a Chinese space station that is part of the Chinese lunar program. Last month, taikonauts (Chinese astronauts) successfully docked another spacecraft with Tiangong. Docking spacecraft is essential to lunar landings. Onboard was the first female Chinese taikonaut, Liu Yang. Hopefully things have changed in space exploration. In 1982,
Russian cosmonaut Svetlana Savitskaya spent a week aboard the Slayut-7 space station. When she arrived at the space station, the four male cosmonauts greeted her at the hatch with an apron as a
‘Welcome’ gift.
We had good attendance at the planetarium for the transit of Venus and everyone got excellent cell phone photos from our projected image. Dr. Noella D’Cruz provided a professional narration of the transit.
The next big sun event we will be watching is a partial eclipse of the sun on October 23, 2014.
On August 6th, the Mars Curiosity Rover will land on the surface of Mars. Because of the size of
Curiosity, NASA had to devise an extremely ambitious landing maneuver employing parachutes, rockets, and cables. There is a video of this sensation and awe inspiring proposed landing on YouTube. www.youtube.com/watch?v=h2I8AoB1xgU <http://www.youtube.com/watch?v=h2I8AoB1xgU>

There are no public shows at the planetarium during the summer months, but we are still doing shows for summer schools and summer camps. Call Christine (815-260-NOVA) between 7 am and noon on
Mondays thru Thursdays for details. Our first public show is scheduled for September 11th.
Art Maurer
Director -Trackman Planetarium
Joliet Junior College
(amaurer@jjc.edu <mailto:(amaurer@jjc.edu> )