In November 2005 the European Space Agency (ESA) launched the Venus Express on a three-year mission to study the surface and atmosphere of Venus, our sister planet.

Venus is closest to Earth in size and mass of all the planets. It lies about three-quarters of the Earth’s distance from the Sun. Here, however, any similarity ends. Its surface temperature is around 900 degrees, hot enough to melt lead! The extreme temperature is blamed by many on a ‘runaway greenhouse effect.’

Solar energy reaches the surface of planets mostly in the form of visible light but is radiated back into space as infrared radiation or heat. Certain materials have the ability to block the escape of infrared rays and heat builds up. One of these is glass, hence, the analogy to greenhouses. Another is the gas carbon dioxide, a so-called greenhouse gas. The atmosphere of Venus contains 96 percent carbon dioxide and, as a result, almost no energy escapes and heat has built up to the hellish conditions found at its surface.

By contrast the Earth’s atmosphere contains about 0.035 percent carbon dioxide, which plays an unknown and controversial role in the warming trends now being observed. Simple chemistry dictates, however, that as carbon dioxide builds up in the Earth’s atmosphere, things are going to get hotter!

Focus on the planets

Mercury may be found early in the month on the east-northeast horizon, just beneath far brighter Venus, about a half hour before sunrise.

Venus shines brightly in the pre-dawn northeast sky where it remains all month. The two stars to the upper left of Venus are Castor and Pollux of Gemini while Mercury is directly below as August opens.

Mars starts the month low in the west about 30 minutes after sunset and, as August wanes, becomes lost in the Sun’s dying glow. The best opportunity to get a last look at Mars before winter will be on the 25th of the month when a thin crescent moon lies slightly to its upper left.

Jupiter is now the brightest ‘star’ in the sky and may be found well up on the southwest horizon at dusk where it remains until midnight as August opens. Viewers with telescopes will be treated to Jupiter’s four major moons moving around and across the face of the giant planet.

Saturn makes its appearance in the morning sky during the third week of the month. Look for the ringed planet in the northeast half an hour before sunrise on Aug. 22 where it is sandwiched between Venus and Mercury.

Uranus is found in the south just after midnight where it is nestled among the stars of Aquarius. Binoculars should afford a glimpse of its green-blue disk.

Neptune offers its best viewing possibilities for the year as it lies high in the south after midnight among the stars of Capricornus. A telescope will be needed to spot the blue-gray disk of Uranus, which lies some 2.7 billion miles from Earth.

Pluto is also high in the south after midnight where skilled viewers can find it with the aid of a star chart such as the one in the May issue of Sky & Telescope.

August events

1 Sunrise, 5:21 a.m.; sunset, 8:02 p.m. Today is Lammas, or “loaf mass,” a cross-quarter day marking the midpoint between the summer solstice and fall equinox.

2 Moon in first quarter, 4:45 a.m. Look for Jupiter to the upper right of the moon in the southwest about an hour after sunset.

4 The orange-red star to the upper right of the moon tonight is Antares.

9 Full moon, 6:55 a.m. The full moon of August is called the Fruit Moon, Grain Moon, or Green Corn Moon. If you are up during the pre-dawn hours, look to the northeast where brilliant Venus lies just above Mercury. To the duo’s upper left are Castor and Pollux while Procyn lies far to the lower right.

10 The Sun enters Leo on the ecliptic. The moon is at perigee or nearest approach to the Earth today.

12 The Perseid meteor peaks around this date and viewers could expect up to 30 meteors per hour, but the waning gibbous moon will wash many of them out. Perseid meteors are fast, bright and often leave persistent trails.

16 Moon in last quarter, 9:52 p.m.

22 The northeast horizon affords a spectacular sight about a half hour before sunrise. Starting from the top, Venus, Saturn and Mercury form a line to the horizon with the thin crescent moon to their immediate left.

25 The moon is at apogee, or greatest distance from the Earth, while situated to the left and slightly above Mars. Check out this last chance to view the Red Planet on the western horizon before it vanishes until winter.

26 Venus and Saturn have a very close approach to each other on the pre-dawn northeast horizon.

31 Moon in first quarter, 6:56 p.m. This is the second time this lunar phase occurs in August. Sunrise, 5:56 a.m.; sunset, 7:15 p.m.

Send astronomical queries to Clair Wood at cgmewood@aol.com or care of the Bangor Daily News, Style Desk, P.O. Box 1329, Bangor, Maine 04402.