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A Meteor Shower and a Shy Planet
updated: May 24, 2014, 11:00 AM

By Chuck McPartlin

This weekend in Santa Barbara's skies there are two astronomical events that may be worth looking at. No telescopes are necessary; simple eyeballs will do. Images in this article are from Starry Night Pro and NASA.

I'm usually hesitant to promote meteor showers, especially newly predicted ones, because they often prove to be duds, or people don't get away from light sources and miss the fainter meteors, and end up disappointed. There's a meteor shower this Friday night and Saturday morning that could potentially be quite a show, though, and the hours aren't too onerous. Just remember - no guarantees!

There's a periodic comet discovered in 2004, called 209P/LINEAR, that's a dim telescopic object this month. It orbits the Sun once every 5.1 years. Looking back at what the history of its orbit was like, orbital dynamicists have postulated that the Earth may pass through a cloud of debris left behind by the comet in the 1700s. If this does indeed pan out, we may get a rate of hundreds of meteors per hour between about 11 PM on Friday night through 1 AM on Saturday morning, May 24. If you don't want to venture out and feed the mosquitos, you can even catch it on webcasts accessible through the Sky and Telescope link below.

To improve your chances of seeing the meteors that do occur, go to a dark location with a good view of the sky, and plop down with your feet to the north. The radiant point is in the obscure northern constellation Camelopardalis, the Giraffe. Meteors may show up in any part of the sky, but they will appear to be radiating from a spot 12 degrees down and left of Polaris. Just face where the Big Dipper would be pouring its contents, and lie back or sit down looking at as much sky overhead as you can.

Our second event is guaranteed to happen, and viewing it will only depend on the weather. On Saturday and Sunday evening, just after sunset, look for the elusive planet Mercury as twilight descends.

Not many people have seen Mercury, because it never strays more than 28 degrees from the rising or setting Sun, and is thus shrouded in the glow of twilight. This weekend, it will be at its greatest elongation for the year, at about 23 degrees away. Because of the tilt of the Earth's axis relative to the ecliptic, the fundamental plane of our solar system, Mercury's altitude above our horizon does not correspond to its elongation, but in the evening skies of spring and morning skies of autumn, the plane of the ecliptic is most nearly perpendicular to our horizon, so Mercury is higher.

Jupiter will be the brightest object in that part of the sky, and Mercury will be along the line from Jupiter to where the Sun set. Castor and Pollux will be above and right from Jupiter, and Procyon to its left. Capella will shine above and right of Mercury. At 8:30 PM, Mercury will be about 14.5 degrees above a hypothetical flat horizon. Ten degrees is about the span of your fist held at arm's length, a proportion that holds true for most people.

Mercury is the smallest of the eight major planets, with a diameter of just 3031 miles. That's not a Band-Aid on Mercury - that's just the part of Mercury that didn't get imaged by the Mariner 10 spacecraft in 1974/1975. Mercury is the closest planet to the Sun at only 36 million miles, and it's named for a guy with wings on his feet because it orbits the Sun in only 88 days. Despite its proximity to the Sun, it's not the hottest planet. Venus takes that prize with its thick blanket of carbon dioxide atmosphere. Nonetheless, Mercury's sunlit side is toasty, reaching 800 degrees Fahrenheit. With no atmosphere to speak of, the side of the planet facing away from the Sun cools to -261 Fahrenheit. Dress in layers if you plan to visit.

Booking your hotel room by the Mercurian year will seem cheaper, since Mercury's axial rotation rate of 59 days combines with its 88 day orbit to put the Sun in its sky for 2 Mercurian years at a time, the longest solar day of all the planets. Plan on losing weight, not only from the sauna, but from Mercury's lower surface gravity, only 39% of Earth's. Your mass, alas, remains the same.

Mercury was the swift Messenger of the Gods, and the NASA wonk who came up with the name of the current spacecraft mission to Mercury should get a medal. It's MESSENGER, for MErcury Surface, Space ENvironment, GEochemistry, and Ranging. MESSENGER has mapped the entire surface of the planet, returning plenty of great images. Craters on Mercury are named after artists and musicians, but prior to receiving their final monikers, the following craters got some humorous temporary code names.

This was the "telephone handset" crater. In a few years, nobody will know what the heck that means.

This, naturally, was the "Mickey Mouse" crater. I would have expected that on Pluto.

And, lastly, the "Bigfoot" craters. Without asbestos slippers, he's probably back in the Washington rainforest cooling his heels.

References for a Cloudy Evening

Sky and Telescope May Meteors




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