Content provided in partnership with

The sky in July and August

Natural History, July-August, 2004 by Joe Rao

Mercury is tough to see in July. The period from the 6th until the 22nd offers observers the best chance to see the planet; binoculars make it much easier. On those evenings the planet shines above the west-northwestern horizon and sets about seventy-five minutes after the Sun. At the same time, though, it fades by half, from magnitude -0.6 to 0.2. Mercury passes just 0.2 degrees north of Mars on the evening of the 10th and glows more than six times brighter than the Red Planet, which is likely to be visible only through binoculars, if at all. On the 26th Mercury reaches its greatest apparent angular distance from the Sun for the year, 27 degrees to the east of our star. Nevertheless, for northern observers the elongation is unfavorable, because Mercury is well to the south of the Sun and not far above the horizon at sunset.

Most Popular Articles in Reference: The importance of understanding organizational culture; Credit card attitudes and behaviors of college students; What factors attract foreign direct investment?; Libraries Need Relationship Marketing - mutual interest marketing concept, ...; How to set performance goals: employee reviews are more than annual critiques; More »

Throughout August, Mercury is approaching inferior conjunction; it passes between our planet and the Sun on August 26. Hence the planet cannot be seen all month.

Venus, the brightest of all planets, is quite spectacular as July begins; it rises in the east-northeast just as dawn breaks. It is still rather low in the east-northeast when it fades away in the growing light of day. As the month progresses, it rapidly leaps upward into high dawn brilliance. By the 14th Venus is rising in total darkness while shining at its greatest brilliancy (magnitude -4.5). A telescope shows it as a thick crescent. Venus shines so radiantly that in clear air it remains easily visible to the naked eye even after sunrise, if you carefully note where to look before dawn.

During August, Venus rises one and a half to two hours before the start of morning twilight, mounting a little higher in the eastern sky with each passing day. Those watching for Perseid meteors [see below] can enjoy the sight of Venus and the nearby crescent Moon on the mornings of the 11th and 12th. Venus reaches greatest western elongation from the Sun, 46 degrees, on the 17th.

Mars shines in stark contrast to its appearance last summer, when everybody was watching it as it made its historically close approach to Earth. This summer the Red Planet is pretty much on hiatus. Although still an evening object, it's much too close to the Sun to be readily visible. Nevertheless, you might look for it on the evening of July 10, when it passes within less than half a full Moon's diameter of Mercury.

Jupiter is the brightest of the evening planets in early July. Anyone with a clear view to the west can't miss it in the fading twilight. But Jupiter is heading down toward the horizon, finishing a yearlong apparition that peaked late last winter. By the end of July the planet is wrapped in the haze of the western horizon while evening twilight is still bright. Jupiter stands well to the lower right of the crescent Moon on the evening of the 21st.

In August, Jupiter continues its fast departure into the west after sundown. As the planet fades, you may need binoculars to pick it out of the bright twilight glare; in the end, though, the glare wins out. The planet is invisible throughout the final week of the month.

As July begins, Saturn, too, is lost in solar glare, and it reaches conjunction with the Sun on the 8th. It re-emerges above the east-northeastern horizon about one and a half hours before sunrise by the end of the month.

During August, Saturn becomes easier to see. By midmonth it rises in the constellation Gemini, the twins, about two and a half hours before the Sun, so the planet is well above the eastern horizon as dawn breaks. On the morning of the 13th it seems to hover about five degrees to the right of a crescent Moon.

In July the Moon waxes full on the 2nd at 7:09 A.M. It wanes to last quarter on the 9th at 3:34 A.M. and becomes new on the 17th at 7:24 A.M. It waxes to first quarter on the 24th at 11:37 P.M., and becomes full for a second time in July on the 31st at 2:05 P.M. The second full Moon in a calendar month is sometimes called a blue Moon--as in "once in...."

In August the Moon wanes to last quarter on the 7th at 6:01 P.M. and becomes new on the 15th at 8:24 P.M. It waxes to first quarter on the 23rd at 6:12 A.M. Our satellite waxes full on the 29th at 9:22 P.M.

The most famous of all meteor showers, the Perseid meteor shower, is expected to peak on the night of August 11-12. It never fails to provide an impressive display and, because of its summertime appearance, most meteors seen by those who are not astronomy buffs are Perseids. The Perseids are fast and bright and often leave persistent trails. Unfortunately for people who go to bed early, the best views are from midnight until the first light of dawn. If the skies are clear, find a place free of bright lights and tall obstructions, look overhead and toward the northeast, and you could see as many as fifty to a hundred shooting stars an hour.

The meteors are known as Perseids because they appear to shoot outward from the constellation Perseus. The Finnish astronomer Esko Lyytinen suggests that a short-lived burst--lasting perhaps forty minutes--of high Perseid activity might take place on August 11 at 4:50 P.M., as the Earth passes very close to a trail of dust that was shed by Comet Swift-Tuttle--the source of the Perseids--in 1862. If anything unusual takes place, observers from eastern Europe to western China are in the best position to see it.

The sky in July and August

Natural History, July-August, 2004 by Joe Rao

Find Research Guides for:

Find Featured Titles for: Home & Garden

Most Popular Articles in Reference

Most Popular Publications in Reference