Monday, December 20, 2010

Significant Solstice

Tonight there is a full moon, and to top it off we'll have the rare treat of a total eclipse!
Our family is excited to observe this, because 1--we'll have excellent darkness and 2--it starts at just 8:30pm Alaska time, peaking around 10:30. We don't even have to get up in the middle of the night to see it! I plan on taking photos and hopefully will get some good ones that I can share here.
Here is a lot more detailed information about what will be happening:
The last Total Lunar Eclipse visible over North America was back in February, 2008. And since we were clouded out that night, our family hasn't seen one since August, 2007! If you have a clear night in your area, I'd encourage everyone to stay up late for this one, or at least wake up with the kiddos, since this will be the last Total Eclipse of the Moon visible over the USA until April 15, 2014! You can be sure our kids will do a lot of growing between now and then, so make sure they take advantage of this opportunity!

A total eclipse of the Moon occurs when the Full Moon slips behind the Earth and passes into the Earth's shadow, lining up perfectly with the Earth and the Sun. In my opinion, the most interesting parts of a lunar eclipse are the partial stages -- the ingress when the Moon is entering the Earth's shadow, and the egress, when the Moon is departing. You can notice the changes over a period of minutes, especially as totality approaches, and it can be quite exciting!

During the partial stage, the curvature of the Earth's shadow can usually be seen across the face of the Moon. This is one of the classical proofs that the Earth is round, as noted by Aristotle in 350 B.C. Try to observe this for yourself [tonight or early tomorrow morning]!

Though all of North America and most of the Pacific will be able to see the entire eclipse, this one will favor observers to the west, on the west coast of the USA and Canada, and in Alaska and Hawaii, being visible during earlier hours of the evening.

Ingress begins when the Moon enters the Earth's penumbra (or partial shadow) at 5:27 UT, which corresponds to 12:27 AM EST and 9:27 PM PST on the evening of December 20. Not much is clearly visible during the penumbral stage, except the brightness of the Moon is somewhat dimmed. If one could be on the Moon's surface during an eclipse, one would see the disc of the Sun begin to slip behind the Earth, cutting off more and more of the Sun's bright rays as the eclipse progresses.

The main event begins when the Moon makes contact with the Earth's umbra (or full shadow) at 6:32 UT, corresponding to 1:32 AM EST and 10:32 PM PST [or about 9:30 Alaska time!]. Though not much is visible at this exact time, a dark edge will be seen on the Full Moon as the Earth's shadow begins to sweep across the Moon's surface. For the next hour or so, a partial eclipse of the Moon will be visible, as the Moon is swallowed by the shade of the Earth.

Totality begins at 7:40 UT, which is 2:40 AM EST and 11:40 PST [or 10:40 AK]. During this time, the Full Moon is completely covered by the Earth's shadow. During totality, it is common to see a murky red glow on the face of the Moon. This is the result of red sunlight being filtered through the Earth's atmosphere onto the Moon's surface.

Believe it or not, when the Sun appears orange at sunrise and sunset, and paints the clouds and the landscape with shades of pink, the Sun's orange rays that don't touch the ground keep radiating out into space and shine on the Moon during eclipse! It's as if the Earth's atmosphere acts as a red filter to remove all the Sun's light except for the reddish shades. If one could be on the Moon during a total lunar eclipse, the Earth would appear as a black circle surrounded by a red ring representing all the sunrises and sunsets!

For the December 21 eclipse, totality ends at 8:53 UT, which is 3:53 AM EST and 12:53 AM PST. After that, the Moon's egress through the partial phases will continue through 10:01 UT, or 5:01 AM EST and 2:01 AM PST. These are no doubt some rude hours for people in the eastern USA and Canada, but earlybirds might be up and around before sunrise on the morning of December 21, and should make it a point to catch the departing partial stage. If you are up that early, be sure to also look for the bright morning star Venus, which is currently blazing in the pre-sunrise sky.
(from "Classical Astronomy Update" newsletter, thanks mom for sending it to me! You can subscribe here )

This article by MSNBC has some details about what to expect, and also tips for taking good photos.

1 comment:

Mallory said...

Awesome! My sister is in Hawaii right now, I just texted her to tell her to check the times and try to get good pictures (since the article you posted said Hawaii will be able to see it well, too). We probably won't be able to see it well here in Cincinnati, because we have so much cloud cover in the winter!

Linked Within

Related Posts Plugin for WordPress, Blogger...