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Relax, it's only April

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Relax, it's only April

The five brightest planets are converging in the western sky for an eye-popping show in May 2002.

NASA

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see captionApril 24, 2002: It's on the radio, in the newspapers and on TV: the planets are aligning! I can't go anywhere lately without people approaching me about it. "Where should I look?" they ask. "Did I miss it?"

I tell them all the same thing: "Relax, it's only April."

The planets are indeed converging in the western sky this month. Just after sunset you can spot Mercury, Venus, Mars, Saturn and Jupiter -- the five brightest planets -- in a line stretching upwards from the western horizon half-way to overhead. It's a pleasing sight.

Right: Four planets and the Moon over San Diego, CA, on April 14, 2002. Credit: Dennis Mammana.

But the best is yet to come ... in May.

That's when Mercury, Venus, Mars and Saturn will form an eye-catching cluster in the constellation Taurus. Jupiter will hover above them in Gemini, just one constellation away. No binoculars or telescopes are required to see them. All you need are your eyes and a clear view of the western horizon.

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Between now and April 30th, Jupiter (half-way up the western sky) and Venus (closer to the horizon) are the attention-getters. Giant Jupiter is bright, and Venus is even brighter. The cloud-covered second planet from the Sun is so dazzling that it is often mistaken for a UFO or a landing airplane. A line drawn between Venus and Jupiter will pass, more or less, through dimmer Mars and Saturn.

Sky watchers who dash outside just after sunset this week can spot Mercury, too. It's that "star" below Venus shining through the glow of the setting Sun. Mercury is climbing higher in the sky each night and, by May 1st, it will remain visible for more than one hour after sunset.

I plan to go outside every night after dinner between May 1st and 7th. Throughout that week, the red star Aldebaran, Mercury, Venus, Saturn and Mars will fit within a circle about 10 degrees across. (Ten degrees is about the width of your fist held at arm's length.) Each night will offer something different and beautiful: On May 3rd, for example, Mars and Saturn will lie a scant 2.5 degrees apart. On May 4th, Mercury reaches its greatest apparent distance from the Sun and makes its closest approach to the other planets. On May 5th, Mars, Saturn and Venus will form a triangle just 3 degrees on each side. And so on....

see captionLeft: The western sky as seen from mid-northern latitudes just after sunset on May 5, 2002.

The planets will begin to disperse during the second week of May. Mercury and Saturn will move toward the Sun where they will disappear from view -- Mercury first, then Saturn by month's end. Venus will move in the opposite direction, away from the Sun and toward Jupiter. Those two bright planets are destined for a dazzling close encounter in early June, but that's another story.

On May 10th -- mark this date on your calendar -- Venus has another rendezvous. As the sky fades to black that Friday evening, Venus and Mars will pop out of the twilight a mere one-third of a degree apart. (The tip of your pinky held at arms length is about twice that wide.) It's a rare opportunity to peer through a telescope and see two planets at once! Glaring white Venus will shine about 100 times brighter than butterscotch Mars, but no matter -- both will be visible.

Another date to remember is May 14th. That's when Earth's moon will glide by Venus with less than a degree between them at closest approach. By itself the Moon would seem remarkable: it will be a slender crescent, mostly dark. Yet the "dark" part of the Moon will be faintly glowing with "Earthshine" -- that is, sunlight reflected from our own planet. Together with Venus, such a Moon is simply indescribable.

Below: A crescent Moon with Earthshine on April 14, 2002. Credit: Sal Viviano. [more]

see captionIf you miss the Venus-Moon encounter on May 14th, don't worry. There will be another one much like it a month later. But if you miss the 5-planet gathering between May 1st and 7th, you'll have to wait 58 years to try again.

Why so long?

Two of the five brightest planets (Venus and Mercury) are always close to the Sun, which means that a gathering of Mercury, Venus, Mars, Jupiter and Saturn can only happen if the Sun is nearby. Usually our glaring star spoils the show. Indeed, that's exactly what happened two years ago on May 5, 2000, when the same 5 planets bunched together with the Sun in the middle. No one could see a thing. The next time they converge far enough from the Sun to be seen as easily as we can see them in May 2002, the date will be July 2060.

So relax, it's only April. Just don't miss May.

more information

The Planets in 2002: A Rare Dance of Planets (Sky & Telescope); A Bonanza for Planet Watchers (Abrams Planetarium);

These sky maps show the appearance of the western sky after sunset from mid-northern latitudes: April 25, May 1, May 2, May 3, May 4, May 5, May 6, May 7, May 10, May 14, 2002.

What about the Southern Hemisphere? The planets are aligning there, too, but the tight trio of Saturn, Venus and Mars is closer to the horizon when the Sun sets in early May. The gathering is harder (but not impossible) to see south of the equator.

see caption

Above: The five brightest planets gathered together two years ago, too. But the Sun spoiled the view. This extraordinary coronagraph image comes from the Solar and Heliospheric Observatory. The blue disk in the middle blocks the glare of the Sun (denoted by a white circle) and reveals Mercury, Venus, Saturn and Jupiter. Mars is just outside the image's field of view. [more]

Earthshine -- (Science@NASA) Northern spring is the best time to spot one of the loveliest sights in the heavens: Earthlight reflected from the Moon.

2002 Spring Planets Gallery -- from SpaceWeather.com


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