Saturday, June 12, 2010

Mark Your Calendars! Moonwatch Friday, June 18, in Draper Park

Photograph of the moon highlighting the Mare Imbrium. The small white circle underneath the center of the Mare Imbrium is the Capricorn crater.

The Hastings Historical Society in conjunction with a group of local amateur astronomers presents a sky viewing for the whole family at 9PM on Friday, June 18th, in Draper Park. Draper Park is accessible via the Historical Society driveway at 407 Broadway, just south of Washington Avenue. Telescopes will be available, along with knowledgeable astronomers, but you are welcome to bring your own telescope, too. There are no lights in Draper Park, which makes looking at the heavens easier. But we do recommend that you bring a flashlight with you so you can see your way. The event is free and open to the public. If it is raining on Friday, the Moonwatch will take place at the same time on Saturday. For more information, call the Historical Society at 478-2249.

We are told by astronomers in the know that the conditions on Friday will be perfect for viewing the Draper crater, named after Henry Draper, whose observatory in Draper Park is the Historical Society’s home. (For more about Henry Draper and his landmark pictures of the moon, click here.) There are actually two Draper craters, referred to as “Draper” and “Draper C”. They are next to each other and of similar size and are called twin craters. These two cup-shaped depressions on the surface of the moon were made by the impact of an asteroid or some similar celestial projectile. Each of these craters is about five miles in diameter and one mile deep, so if we ever decide to move Hastings and Dobbs Ferry lunarside, we could probably squeeze them both into the Draper crater.

These two “small” craters are at the very southern edge of the Mare Imbrium, which, translated from the Latin, means “Sea of Showers.” The moon has many “maria”, inappropriately named by early astronomers who thought they were real seas full of water. They are, in fact, huge, dark basalt planes made by the eruption of lava onto the moon’s surface. The Mare Imbrium’s circular shape is the result of an object hitting the moon’s surface and leaving behind a crater, which was later filled with lava. This “sea” is almost 700 miles in diameter. On the Earth, a crater this size would encompass New York state, Pennsylvania, most of Virginia, and all of New England except the northern tip of Maine. The impact of this huge object on the moon created several ridges of 4-mile-high mountains along the edge of the crater, and is thought to have caused a series of faults across the entire surface of the moon. In 1971, Apollo 15 landed in the Mare Imbrium and, based on rock samples it collected, scientists have dated the original impact that created the “sea” to 3.85 billion years ago.

If you want to get a good look at the Mare Imbrium, the Draper craters, and other lunar features, join us for the Moonwatch next Friday!

Photograph of the moon showing the Copernicus crater, the “Carpathian Mountains” that mark the southern edge of the Mare Imbrium, and, at the very top of the photograph, the twin Draper craters. (Image used with permission of the Regional Planetary Image Facility, Lunar and Planetary Institute, University Space Research Association, Houston, TX.)

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