Total eclipse will turn the Moon red
Sen—A total lunar eclipse will turn the Full Moon an orangey-red this week in a spectacle that can be enjoyed across the Americas and Pacific, weather permitting.
It happens because the Moon will pass directly through the shadow of the Earth in space on this particular orbit, rather than just dodging it as is usually the case.
Technically the whole of the eclipse occurs on 15 April by the standard of Universal Time (UT, also known as GMT). In practice this means it will be the evening of the 15th for Pacific regions west of the International Dateline, but still the 14th for American observers in the west of the USA.
Sadly for Europe, Africa and most of Asia, there is nothing to see. The Moon will be slipping into the only slightly darkened outer shadow just as the Moon is low and about to set from western Europe and Africa. Half a world away it is a similar situation for Japan and the Philippines because the Moon will be rising just as it is exiting this lighter region of shadow.
This outer, lighter shadow is called the penumbra and is where the Earth blocks some of the Sun’s light but not all of it. If you were standing on the Moon, you would see the Sun partially covered by the Earth.
A guide showing the passage of the eclipse as the Moon moves through the Earth's shadow. For the convenience of US observers, timings are given as Eastern Daylight Time (EDT) rather than UT. Diagrams for other time zones are available here. Image credit: Fred Espenak/www.MrEclipse.com
Within the penumbra is a darker central shadow called the umbra, produced where the Sun is totally blotted out by the Earth. When the Moon glides into this, it will turn a deep shade of orange or red.
You can usually still see the Moon at totality, even though there is no direct sunlight. This is due to the scattering of sunlight through the Earth’s atmosphere and onto the Moon. Just how deep a red it becomes depends on the amount of dust in our own atmosphere, so you will just have to wait and see!
First contact with the Earth’s pale grey outer penumbral shadow occurs just after 04.53 UT, and the Moon is completely enveloped a little over an hour later.
Since the penumbra is faint, all that is likely to be noticed during that period is a slight darkening of the Moon’s leading (left-hand) edge. At 05.58 UT the Moon makes first contact with the umbra, i.e. it begins to enter the darkest part of the shadow.
Totality starts just before 07.07 UT, when the Moon is completely immersed in the umbra. Totality lasts for about 78 minutes. Just after 08.24 UT, the Moon’s leading edge emerges from the umbra into the relative brightness of the penumbra, ending totality and it exits the dark umbra completely at 09.33 UT. It leaves the penumbra too at 10.37 UT.
During the eclipse the Moon will lie in Virgo, with planet Mars not far away and shining brightly, so this is a good chance to compare the orange-red colours of the two objects.
Steadily-held binoculars are the best instruments with which to enjoy lunar eclipses, but you can enjoy with just your eyes. Check the progress of the umbra’s edge across the familiar lunar features and the colour of the Moon, as the event proceeds.
NASA guide to understanding lunar eclipses. Credit: NASA Goddard