December 24, 2011

Watch a new Moon meet Venus Monday evening

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Here’s an after Christmas gift for skygazers. Monday evening, December 26th a two day old thin crescent Moon will appear about 6 degrees NNW (right) of brilliant planet Venus above the southwestern horizon. Head outdoors as twilight falls and watch for glistening Venus just left of the Moon’s tipped “Chesire Cat” grin as the sky darkens. The other bright object in the sky will be Jupiter high in the south to your left.

Take time and let the sky darken and you’ll be treated to the soft glow of the Moon’s disc in “earthshine” which is sunlight reflecting off the Earth.

Make note of the Moon’s position above your SW horizon and I’ll have an interesting observing exercise for you which will show you the tilt of the Earth’s axis and the ecliptic which is the plane of the solar system.

Graphic shows the southwestern horizon Monday, 26 December, 6pm local time, prepared with  YourSky

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“Christmas Comet” survives encounter with Sun

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A unique “sungrazer” comet was discovered in early December by Australian amateur astronomer Terry Lovejoy. Comet Lovejoy (C/2011 W3) is unusual because it grazed the Sun, actually flying through the 7 million degree solar corona for about an hour, and survived. Comet Lovejoy surprised the astronomy community by surviving it’s encounter with the Sun on December 16th.
The comet is a member of the Kreutz family of sungrazing comets.

Its putting on quite a show in the early morning sky and may remain a naked eye object into early January. That’s the good news. The not so good news, depending on your location, is that Lovejoy is visible primarily in the southern hemisphere.

If you’d like to try to observe comet Lovejoy watch the southeastern horizon 45 minutes before sunrise. The tip of the comet’s tail may just be visible to observers in the extreme southern U.S.

IMAGE ABOVE: Astronaut Dan Burbank captured this image of Comet Lovejoy from the International Space Station on December 21, 2011.

Watch a time lapse video of comet Lovejoy’s encounter with the Sun from NASA’s Solar and Heliographic Observatory

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December 20, 2011

The December solstice…the reason for the season!

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December 22nd marks the winter solstice in the northern hemisphere and the summer solstice south of the equator. It’s the first day of winter here in the north, the first day of summer in the south. Here in the northern hemisphere the solstice is the “shortest” day of the year with the fewest hours of daylight. On Thursday the days will start getting longer.

You might have the impression that the days are already getting longer and that is because the earliest sunsets were the first two weeks of December. This is because more people see sunsets than sunrises. Sunsets are already happening a minute or two later. The order of events at winter solstice is earliest sunset, shortest day then latest sunrise which will occur January 5th.

At the December solstice the northern hemisphere is tilted away from the Sun, the southern tipped toward our star. At the spring and fall equinoxes the Sun is above the equator. This is the reason we have seasons! Interestingly, Earth is closest to the Sun on January 4th and furthest on July 4th!

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