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What's in the sky: July

Follow constellations across the sky


July is a great month for stargazing. Evenings are pleasant, and many of us are involved in outdoor activities such as camping. Yes, it gets dark late, but once it does get dark, celestial wonders such as the summer Milky Way beckon overhead.

One July evening activity that many of us will be involved in during July is celebrating our national birthday on July 4. If you're waiting for the sky to get dark and that fireworks show to start, check out the stars that begin to show in that darkening sky. If you have a view of the low, western horizon, at about 9:45 or 10 p.m., look for three "stars" in a line, quite close together. Closest to the horizon is Regulus, the brightest star in the constellation Leo. Above and to the left of Regulus is the planet Mars. Late last December, Mars was at its closest approach to Earth, and appeared quite bright (and noticeably red) in our sky. Mars is now about three times as far from the Earth as it was in December, and will soon depart the night sky. Above and to the left of Mars is Saturn, the ringed planet. Saturn also is fading; it had its closest approach in February. Saturn is the brightest of these three, and should show up first as skies darken.

By July 10, Mars will be located very close to Saturn, and then will move to the left of Saturn in the rest of the month. Both planets will leave our evening skies in August.

Gazing southeast on July 4, you may see a very bright star above the horizon. That is the giant planet Jupiter. Jupiter will reach its closest 2008 approach on July 9. It will stay low, only about 15 degrees above the horizon. Jupiter is particularly impressive because of its four large Moons. Io, Europa, Callisto, and Ganymede are easily visible in telescopes and visible with binoculars. They'll be visible as tiny stars, lined up along Jupiter's equator. Larger binoculars (those with 50mm lenses, and seven or 10 power helps) work the best. From night to night, you will see the Moons change position as they orbit the planet. For example, if you look on July 4, Io and Ganymede will be to Jupiter's left, with Europa and Callisto on the right. On July 5, only Ganymede will be on Jupiter's left, with both Io and Europa close to the planet's right side, and Callisto far out to the right. Astronomy magazines and many websites include charts with which you can find the location of the Moons.

Skies will be nice and dark on July 4; new Moon will have occurred just two days before, on July 2. If you have a really good view of the low, western sky on July 4, look for it near the horizon, below and to the right of Regulus. It will be a tiny sliver of a crescent, difficult to pick up in twilight. Watch the Moon grow larger and brighter as it moves across the night sky between July 2 and July 17, when full Moon occurs. The full Moon will be located just to the left of Jupiter on July 17.

Constellations continue their march across the sky in July. Leo the Lion departs in the west. In the east, Pegasus and Capricornus begin to appear. Pegasus is easily identifiable by its "great square," with four almost identically bright stars making up the corners of an almost perfect square. See if you can pick it out, rising above the horizon at mid-month. It will be located below the tip of the Northern Cross if you are looking east.

As I mentioned earlier, many of us will be spending time camping in summer. In our modern society, that is one of the few times that many people are outside, away from the lights of civilization, for an extended time period. I've often heard people in this situation exclaim, "I've never seen so many stars" when they look at the night sky. The reason is simple; our eyes become adapted to the dark. After we have spent a few minutes away from light, we can see noticeably more in the dark. After about half hour in darkness, our eyes can be thousands of times as sensitive to dark, and we're able to see much more in the sky. So if you find yourself up late this summer, in a dark, rural area, spend some time looking up!


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