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<< Previous   of   Next >> (click to enlarge)   ADVERTISEMENT   CONTACT THE HERALD Melanie Munk, Features Editor munk@heraldnet.com   Published: Sunday, December 21, 2008 Starwatch: Venus provides a 'Christmas star' By Mike Lynch Special to The Herald It's the most wonderful time of the year, as one of the sage, old Christmas songs proclaims. Astronomically, I love it. I can begin my stargazing and my brand new love, astrophotography by 6 p.m. It's not as warm below the starry skies this time of year, but at least for avid backyard astronomers there's much less sleep deprivation. Even if you're not an astro-nut like I am, you can't help but enjoy the beauty of the Everett night skies during the holiday season. The bright wonderful constellation Orion the Hunter is on the rise in the east with his squadron of surrounding bright constellations, such as Taurus, Gemini and others. It's also a lot of fun this time of year to see a brilliant "Christmas star" in the east during the early morning hours. That Christmas star is actually a planet, Jupiter or Venus depending on the year. Unfortunately, this year neither one of these planets are up before dawn. About the only celestial object that comes close in the predawn heavens is the bright star Arcturus, perched high above the southeastern horizon. Even though Arcturus is one of the brightest stars in the sky any time of the year, it just doesn't cut it as a Christmas star. So to find a Christmas star of 2008, you have to resort to looking in the early evening, but you don't have to look very hard. The bright planet Venus will leap out at you in the southwestern sky. It pops into view in the early twilight skies and stays above the horizon until after 8 p.m. It can be your celestial companion as you head to and from holiday parties or go in search of last-minute Christmas presents. Venus is so bright that if you're really out in the boonies where it's super-dark, it can cast a faint shadow. Venus is so bright this Christmas for a couple of reasons. For one thing,Venus is making its closest approach to Earth as both planets orbit our home star, the sun. Venus is less than 80 million miles away and will get a lot closer to us as we go into 2009. The principle reason, though, is that Venus has a very thick and highly reflective cloud cover that beams a lot of reflected sunlight. It would even be brighter if the entire sunlit half of Venus were facing Earth, but because of the celestial geometry of the sun, Earth and Venus, we're only seeing a "half Venus." Through a small telescope or a good pair of binoculars you'll see that Venus is half-moon shaped. In the next several months Venus will take on a crescent shape. Honestly, the changing shapes of Venus are the only real reason to direct your telescope toward the planet named after the Roman goddess of love. The clouds hide everything on its surface below. Even though Venus may serve as the Christmas star for 2008, and it may add to that warm, fuzzy holiday feeling, Venus's physical nature is not warm and fuzzy at all. It has a poisonous atmosphere and is hotter than a place I don't like to mention this time of year. That cloud cover you see obscuring Venus is made of sulfuric acid. There's even occasional lightning in the acid rainclouds. You certainly wouldn't want to spend a lot of time floating in those clouds. It would be really rough on your complexion. Most of Venus's atmosphere is composed of heavy duty carbon dioxide, making Venus a poster child for global warming. Most of the sun's light and radiation is bounced away by Venus's highly reflective clouds but some sunlight manages to fight its way through the thick clouds and heat up the planet's rugged surface of mountains and valleys. Most of the infrared radiation that rises in response to the sun's heating, however, is absorbed by the carbon dioxide in the atmosphere. That drives up the temperature in the Venusian atmosphere which in turn greatly heats up the surface. The end result; Venus is one dark, hot place with surface temperatures topping 900 degrees. It's by far the hottest planet in our solar system to walk around on. To add to the awfulness of hanging out on Venus, the atmospheric pressure is 90 times that of Earth's surface. It's a poisonous pressure cooker. Forget about astronomical reality, though, and just enjoy our view of Venus as the bright friendly star of Christmas 2008. Have a wonderful holiday season. Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis and author of the book, "Washington Starwatch," available at bookstores and at his Web site www.lynchandthestars.com The Everett Astronomical Society welcomes new members and puts on public star parties. The Web site is members.tripod.com/everett_astronomy. READER COMMENTS Be the first to comment. You must be a registered user and verify your e-mail address to post comments to blogs or articles on HeraldNet. To register, click here. To read other terms and conditions, click here. Log out

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