Weird Sunset On Monday, June 10th, the Moon will glide in front
of the Sun as it sets over parts of North America.
You've probably seen so many that you hardly notice any more. But, if you live in North America, pay attention next Monday for something extraordinary as twilight approaches.
The setting Sun will be a crescent.
Above: On Dec. 14, 2001, George W. Fleenor captured this image of a partially eclipsed Sun setting at Siesta Beach in Sarasota, Florida. [more]
If you decide to skip dessert and dash outside for a glimpse, don't look directly at the eclipse. Even when our star is partially covered, it's still bright enough to blind you. Instead, use a safe solar filter like #14 or higher welding glasses to protect your eyes.
Better yet, project an image of the Sun onto a screen through binoculars or a telescope. But, be careful! Never look through the optics. Keep your eyes on the projection screen, not on the eyepiece. Adjust the focus knob until projected sunspots appear crisp and sharp. Almost anything can serve as a screen -- a paper plate or a light-colored wall, for example.
Eclipses that happen low in the sky are easy to observe indoors, too. Simply find a room with a west-facing window and draw the shades. Any tiny crack or opening will cast an outline of the crescent Sun onto the far wall.
Above: projecting an image of the Sun is a safe and sometimes artistic way to experience an eclipse. These images were captured by Science@NASA readers (left to right) Matt Sharpe, Evan J. Gnam, and Ben Walden during the 2000 Christmas eclipse. [more]
The partial eclipse will last about two hours. Unfortunately, sky watchers along the eastern edge of North America won't see any of it. In Miami, Washington D.C. and New York City, for example, the eclipse begins and ends after nightfall. However, almost everyone in the United States west of Atlanta can see some of the event (weather permitting). Observers in the south and central U.S. are best-placed to see a deep eclipse at sunset.
There are a few places, mostly in the Pacific Ocean, where the Moon will cross the Sun dead-center on June 10th (or June 11th, because of the International Date Line). For about one minute, a bright "ring of fire" will surround the Moon. It's what astronomers call an annular eclipse.
The "path of annularity" is long and narrow. It stretches nearly 15,000 km across the Pacific Ocean -- from the coast of Mexico near Puerto Vallarta to the waters east of Indonesia. Only a few Pacific islands (Saipan and Tinian are the largest among them) lie inside the path, which is barely 78 km across at its widest point. Guam is nearby but not quite inside. Sky watchers there will experience a deep partial eclipse, with 97.5% of the Sun covered.
Right: Sky and Telescope magazine prepared this map (Copyright 2002, Sky & Telescope) of eclipse circumstances across the Pacific Ocean. We recommend their article "June's Transpacific Solar Eclipse" for more information about the event outside North America.
Annular eclipses shouldn't be confused with total eclipses. Total eclipses happen when the Moon completely covers the Sun's surface. Then, the faint solar corona springs into view -- a breathtaking sight by all accounts. On June 10th, the Moon is too small to cover the whole Sun. The Sun's dazzling outer limb will peek out all around the Moon. It will be very bright, and eye safety measures are essential.
Relatively few people will experience the annular phase of this month's eclipse. It's simply too remote. Nevertheless, plenty of sky watchers in North America will enjoy the partial phase: a lovely and very weird sunset. Don't miss it!
Editor's note: This story is crafted for North Americans and stresses the view from the continental United States. For additional details about the eclipse in other parts of the world see "June's Transpacific Solar Eclipse" from Sky & Telescope (external site).more information
Annular Solar Eclipse of June 10th, 2002 -- (GSFC) detailed information about the eclipse from Goddard's Fred Espenak.
Above: Click to view a full-sized map of eclipse circumstances across North America.
June's Transpacific Solar Eclipse -- (Sky & Telescope) If you enjoy watching sunsets, you have all the more reason to do so on June 10th.
Annular vs. Total Eclipses: Lovely solar eclipses are possible because of a lucky coincidence. Although the Sun is about 400 times larger than the Moon, it is also about 400 times farther away. From our point of view, the Sun and the Moon seem to be the same size: 0.5 degrees wide -- but not always! The Moon's orbit around our planet is an ellipse, not a circle, so the width of the Moon waxes and wanes each month by ±7%. Earth's orbit around the Sun is elliptical, too. The angular diameter of the Sun varies by ±2% throughout the year. When the Moon happens to be the same size as or bigger than the Sun, total eclipses are possible. When the Moon is smaller, eclipses can be only annular or partial. On June 10th, the Moon will be smaller than the Sun, and the maximum eclipse will be annular.
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