¡SkyCaramba! Weekly astronomy blog for the week ending April 12, 2014
The first of four consecutive total lunar eclipses happens the night of April 14 to 15 for most of the Americas and the Pacific. Parts of the Americas, the Pacific, and Australia get part of the event as the moon is rising or setting.
The very beginning of the eclipse is at 04:53 Universal Time on April 15. That will be 11:53pm on the 14th in the Central Time Zone of the United States. As the eclipse starts, the moon passes into the penumbra or outer part of Earth’s shadow. It will be several minutes—maybe more than a half hour—before you see the lighting difference.
As an orange hue slowly sweeps across the moon, the moon heads to the inner part of Earth’s shadow which it enters at 05:58. This is when the partial phase starts. You won’t have any trouble noticing the dark area crossing the moon. Every minute or two, you’ll see the dark area called the umbra is covering more of the lunar surface.
Keep watching until 07:06 and the moon will be completely in the umbra. That’s the darkest part of Earth’s shadow. Now, totality begins. It lasts until 08:24. Even during the total phase, you may see that one side of the moon is darker than the other and that the darkest area sweeps across the moon. That happens because even when the moon is deepest in the earth’s shadow, some sunlight refracts through Earth’s atmosphere and reaches the moon.
As the moon emerges from our planet’s shadow, you’ll see a reversal of what has happened so far. From 08:24 to 09:33, the umbra crosses the moon and leaves the lunar disk. Then until 10:37, the penumbra crosses the disk and leaves too.
If you could be on the moon during a total lunar eclipse, you’d see the sun passing behind Earth. During penumbral phase, the sun would stick out from behind Earth. On any part of the moon that is in the earth’s umbra, Earth would completely cover the sun. But at all times, there’d be an orange-red ring of sunlight refracting through the earth’s atmosphere.
For reasons that aren’t entirely understood, you may see colors other than orange or yellow crossing the moon during an eclipse. A few eclipses have been very deep red. Others have been greenish. Everything from clouds, to industrial pollution, to volcanic ash could be affecting sunlight on its way through the air to the moon. This phenomenon isn’t predictable. You should look at the eclipse yourself just in case it’s unusual.
During the next year-and-a-half, there will be three more total lunar eclipses: October 8, 2014, April 4, 2015, and September 28, 2015. If for whatever reason you can’t see the one this month, I hope you can make the best of the next three chances.