A total eclipse of the moon will be visible throughout North America starting just before midnight on Nov. 28, according to U-M astronomer Richard G. Teske.
“Lunar eclipses occur during the time of full moon when the sun, Earth and moon all line up with the moon behind Earth, hidden within the shadow cast by our planet,” Teske says.
During November’s eclipse, the full moon will first touch the darkest part of Earth’s shadow at 11:40 p.m. Nov. 28. Observers can watch Earth’s curved shadow slowly cover the moon as it enters the shadow at a speed of 2,300 miles an hour. Mid-eclipse will occur at 1:26 a.m. By 3:12 a.m. the event will be over with the moon fully illuminated again.
Teske says that we’re usually unaware of Earth’s shadow, because there is nothing in empty space for it to be cast upon. “If a huge movie screen were placed opposite the sun, we’d see the screen brilliantly illuminated by sunlight with a dark circle on it—Earth’s shadow—about three times the moon’s width,” Teske says. “The moon acts like a roving piece of movie screen; it spends most of its time in bright sunlight but sometimes orbits into the shadow’s darkness.”
Lunar eclipses no longer have important scientific value and are not intensively observed by astronomers. Teske says this is because “the space age has transformed the moon from a distant astronomical body into a nearby, well-understood object. American spacecraft have crashed into it, landed on it, circled it and photographed more than 99 percent of it. Astronauts have walked its surface and brought back moon rocks.”
While enjoying November’s event, Teske recommends that observers watch for color changes as the eclipse progresses. The shadow’s rim usually has a reddish tint, an effect caused when sunlight grazing Earth’s edges passes through the surrounding atmosphere. All colors of sunlight except reds are filtered out by the air. This is the same effect that dyes the rising or setting sun red.
The moon will probably be dimly visible during totality, because some sunlight traversing Earth’s atmosphere can be refracted or “bent” into even the darker parts of the shadow where it weakly illuminates the moon, according to Teske.
While the moon is in deepest shadow, Teske says, observers may notice two famous star clusters nearby. At first, moonlight will make it difficult to see them, but as the moon dims, fainter stars gradually will appear. “Above and to the right of the eclipsed moon are the Pleiades—a compact, glittering group of stars about 420 light-years away,” Teske says. “Below the eclipse are the Hyades, a larger grouping only 140 light-years from us. Both clusters are populated by more than 100 stars of greatly differing brightnesses, but our eyes pick out only the brightest few in each.”
