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Hal Kibbey
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Last modified: Tuesday, July 1, 2008

STAR TRAK

Saturn meets Mars in evening twilight

Planets


FOR IMMEDIATE RELEASE
July 1, 2008

BLOOMINGTON, Ind. -- Saturn and Mars will have a close encounter low in the western sky an hour after sunset on July 9 and 10. Watch each evening for the first ten days of the month as red-orange Mars is lured away from a dalliance with the bright white star Regulus in the constellation Leo the Lion. Nearby on the left (south) will be even brighter Saturn, and what planet could resist that?

On July 5 and 6, the crescent moon will join the party. By July 9 and 10, when Saturn and Mars are closest, many telescopes will show both planets in the same field of view. The group will break up after that, with both planets setting in bright twilight by month's end. They won't be that close again until 2022.

The latest images from the surface of Mars, where the Phoenix spacecraft landed in May, can be seen at http://www.nasa.gov/mission_pages/phoenix/main/index.html.

Jupiter will dominate the night sky all month during July, reaching opposition (opposite the sun in our sky) on July 9, when it will rise in the east at sunset and set in the west at dawn. The best time to observe the great planet during July will be in the middle of the night, when it will be highest in the south. Even then it will be lower than usual, which may blur the view a bit for telescopes.

Mercury will be visible with binoculars just above the east-northeastern horizon about 45 minutes before sunrise on July 1. It will remain there for the first two weeks of the month before disappearing into the solar glare.

Venus will finally begin a tantalizingly slow return to the evening sky during July. By month's end it will be a few degrees above the west-northwestern horizon shortly after sunset.

Viewing information and graphics for the planets are available at http://www.space.com/spacewatch/.

Meteor shower

The southern branch of the Delta Aquarid meteor shower will peak before dawn on July 27, with meteors appearing several nights before and after the peak as well. The long bright streaks will seem to come from a point in the constellation Aquarius in the southern sky during the hours just before morning twilight. In a dark sky there might be as many as 20 meteors per hour at the peak, with only minor interference from the waning moon.

Aphelion

On July 4, Earth will reach its greatest distance from the sun for the year, called aphelion. Those trying to beat the summer heat in the Northern Hemisphere may find it hard to believe that we're about 3 percent farther from the sun than we were in January. Those experiencing winter in the Southern Hemisphere will be easier to convince. It's a good way to demonstrate how much Earth's tilt on its axis affects our daily lives.

Noctilucent clouds

A beautiful phenomenon of the twilight sky called noctilucent clouds is sometimes visible in the Northern Hemisphere during summer. These wispy clouds form when water vapor condenses onto meteoric dust particles about 50 miles above Earth's surface. Noctilucent clouds are so thin that they can't be seen in daylight. They appear only when the sun is just below the horizon, either in the northwest after sunset or in the northeast before sunrise, when the background sky is dark enough but there is still some light. Look for delicate bluish-white veils above the place where the sun is below the horizon. These gauzy clouds are easy to distinguish from regular clouds, which appear dark against the morning or evening twilight. Numerous photographs of noctilucent clouds can be seen at http://www.polarx.net/NoctilucentClouds.htm.

Moon phases

The moon will be new on July 2, at first quarter on July 10, full on July 18, and at third quarter on July 25.