WAUKESHA, WI – On the morning of December 25, three planets will form a close grouping low in the southeastern sky.
30 minutes before sunrise – just before opening presents – you’ll be able to see Mercury, Venus, and Mars at the same time. Use Venus – the brightest of the trio – to help you locate the other planets. Mercury will appear 2° to the left of Venus. (2° is approximately the width of one finger held at arm’s length.) Mercury will be easy to identify because it will be the second-brightest object in that part of the sky.
Mars will lie 11.5° to the upper right of Venus, nearly six times as far as Mercury. (Use your closed fist held at arm’s length to approximate this distance.) On December 25, Mars is about as faint as it can get, more than 100 times fainter than Venus. By next summer, however, Mars again will be easy to see as it blazes in the evening sky.
Don’t confuse Mars with Antares, the brightest star in Scorpius the Scorpion. Antares lies 5.5° to the lower right of Venus. On Christmas morning, Antares will be slightly brighter than Mars.
Seen through a small telescope, these planets resemble the changing Moon phases throughout the month. Venus appears almost full – 92 percent of its face is illuminated. Mercury, on the other hand, appears like a quarter Moon, with only half of its disk illuminated.
For general information on planets, click here. Even closer after Christmas
If you watch Venus and Mercury after Christmas, you’ll notice they get closer. On the morning of December 29, Mercury will be only 1.2° from Venus – nearly twice as close as the pair appears on Christmas.
Astronomy magazine staff members are interviewed regularly on television, radio, and print media. We are experienced in translating high-level astronomy jargon into easy-to-understand language – we bring the out-of-this-world down to Earth.
December 20, 2004