Holiday Sky Show: Five Planets to Shine in Predawn
for National Geographic News
|December 16, 2004|
A heavenly show awaits stargazers this holiday season: Over the next few weeks sky-watchers can spot five planets in the same nighttime sky.
The planets, visible to the naked eye, will appear spread across the sky in the minutes before dawn. Mercury, Venus, and Mars will shine in the east, while Jupiter will hover overhead, and Saturn will hang in the west.
"It is something that happens every so often," said Deborah Byrd, producer and host of the Earth and Sky syndicated radio series. "Sky-watchers know how special that is."
All five planets were visible in the evening sky in late March and early April. But they won't be seen together again, at least with the naked eye, until 2016.
No special skills or equipment are needed to observe the celestial show.
"You just use your eyeballs. You don't need any binoculars or a telescope," said Kelly Beatty, an editor with Sky and Telescope and Night Sky magazines. "It's [visible] all over North America and over much of the civilized world. Most everyone will be seeing this."
Follow the Sun
Viewers are advised to first look to the east some 45 minutes before sunrise.
"That's late enough so that Mercury is high enough above the horizon [to be visible], but not so late that it becomes too bright for viewing," Beatty said.
Planet-spotters should also direct their attention to the path that the sun travels during the day.
"The planets orbit the sun in a more or less flat plane. So they aren't scattered all over the sky but travel across the sky [along] more or less the same path as the sun," Byrd, the radio producer and host, said. "Try to visualize, from your yard for example, where the sun comes up and where it goes down."
Venus and Jupiter should be easiest to spot. With the exception of the moon, they are the brightest objects in the predawn sky. Venus will hang low in the east.
Dimmer and harder to identify: Mars and Mercury, which will appear near Venus.
Jupiter will shine brightly overhead, and Saturn, though very bright, will share the western sky with the also-bright twin stars of GeminiCastor and Pollux. The brightest of that three-star grouping will be the ringed planet.
(See Earth and Sky's five planets chart here.)
The five planets will share the same nighttime sky until early to mid-January. From December 10 to 28 and again in mid-January, they will also appear in their "correct" order: Mercury, Venus, Mars, Jupiter, and Saturn.
"There's nothing particularly 'correct' about the order," Beatty noted. "But it is the most familiar lineup, as it represents the order that we know them outward from the sun."
Mercury, said to be the most elusive of these visible planets, is the key to the rare joint appearance.
"Mercury is the innermost planet to the sun, and it travels around the sun in only 88 days," Byrd said. "What that means in our sky is that Mercury moves from the morning to the evening sky six times a year. Most other planets don't do that."
The planet also never rises far above the horizon and does so only near dawn and dusk. Most of the time the sun's glare obscures Mercury to the naked eyes of sky-watchers.
"It comes and goes quickly," Byrd added. "The longest you'll ever see it in one place in the sky is a month. But usually it's only [in one location] for a week or ten days. That's why it has the name Mercury, after the fleet-footed messenger god."
During the current convergence, Mercury "is just getting to the place in its orbit where there's the greatest distance between Mercury and the sun on the sky's dome," she said. "That's when we can see it."
The orbiting planets are visible from Earth in part because all are currently on the same side of the sun. They are not, however, in any type of alignment.
"They are not in some kind of straight line in space," Byrd explained, noting that NASA scientists have used computers to project the location of the planets millions of years into the future. "In all that time, there's never a time when all the planets make a straight line in space."
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