A tetrad of Lunar eclipses

March 28, 2014 by Dr. Tony Phillips
Mosaic of the near side of the moon as taken by the Clementine star trackers. The images were taken on March 15, 1994. Credit: NASA

For people in the United States, an extraordinary series of lunar eclipses is about to begin.

The action starts on April 15th when the full Moon passes through the amber shadow of Earth, producing a midnight eclipse visible across North America. So begins a lunar eclipse tetrad—a series of 4 consecutive total eclipses occurring at approximately six month intervals. The total eclipse of April 15, 2014, will be followed by another on Oct. 8, 2014, and another on April 4, 2015, and another on Sept. 28 2015.

"The most unique thing about the 2014-2015 tetrad is that all of them are visible for all or parts of the USA," says longtime NASA eclipse expert Fred Espenak.

On average, occur about twice a year, but not all of them are total. There are three types:

A penumbral eclipse is when the Moon passes through the pale outskirts of Earth's shadow. It's so subtle, sky watchers often don't notice an eclipse is underway.

A is more dramatic. The Moon dips into the core of Earth's shadow, but not all the way, so only a fraction of Moon is darkened.

The video will load shortly

A , when the entire Moon is shadowed, is best of all. The face of the Moon turns sunset-red for up to an hour or more as the eclipse slowly unfolds.

Usually, lunar eclipses come in no particular order. A partial can be followed by a total, followed by a penumbral, and so on. Anything goes. Occasionally, though, the sequence is more orderly. When four consecutive lunar eclipses are all total, the series is called a tetrad.

"During the 21st century, there are 9 sets of tetrads, so I would describe tetrads as a frequent occurrence in the current pattern of lunar eclipses," says Espenak. "But this has not always been the case. During the three hundred year interval from 1600 to 1900, for instance, there were no tetrads at all."

The April 15th eclipse begins at 2 AM Eastern time when the edge of the Moon first enters the amber core of Earth's shadow. Totality occurs during a 78 minute interval beginning around 3 o'clock in the morning on the east coast, midnight on the west coast. Weather permitting, the red Moon will be easy to see across the entirety of North America.

Why red?

A quick trip to the Moon provides the answer: Imagine yourself standing on a dusty lunar plain looking up at the sky. Overhead hangs Earth, nightside down, completely hiding the sun behind it. The is underway.

You might expect Earth seen in this way to be utterly dark, but it's not. The rim of the planet is on fire! As you scan your eye around Earth's circumference, you're seeing every sunrise and every sunset in the world, all of them, all at once. This incredible light beams into the heart of Earth's shadow, filling it with a coppery glow and transforming the Moon into a great red orb.

Mark your calendar for April 15th and let the tetrad begin.

Explore further: New lunar eclipse video released

More information: A complete visibility map of the April 15th lunar eclipse is available online: eclipse.gsfc.nasa.gov/OH/OHfigures/OH2014-Fig01.pdf

Related Stories

New lunar eclipse video released

June 9, 2011

(PhysOrg.com) -- In anticipation of the upcoming lunar eclipse later this month, NASA has released a new video that shows how lunar eclipses work.

LRO observes final lunar eclipse of the year

December 9, 2011

(PhysOrg.com) -- Orbiting 31 miles above the lunar surface, NASA's Lunar Reconnaissance Orbiter (LRO) spacecraft will get a "front-row seat" to the total lunar eclipse on Dec. 10, 2011.

Southern hemisphere to glimpse year's last solar eclipse

November 24, 2011

The tip of South Africa, Tasmania and most of New Zealand will -- weather permitting -- enjoy a partial eclipse of the Sun on Friday although the handful of hardy scientists in Antarctica will get the best view, according ...

Partial lunar eclipse visible in western skies

June 27, 2010

(AP) -- Skygazers got a treat Saturday when a portion of the moon crossed into the Earth's shadow during a partial lunar eclipse visible in the western United States and Canada, the Pacific and eastern Asia.

Recommended for you

Tracing aromatic molecules in the early universe

March 22, 2017

A molecule found in car engine exhaust fumes that is thought to have contributed to the origin of life on Earth has made astronomers heavily underestimate the amount of stars that were forming in the early Universe, a University ...

Sand flow theory could explain water-like streaks on Mars

March 22, 2017

(Phys.org)—A team of researchers from France and the Slovak Republic has proposed a theory to explain the water-like streaks that appear seasonally on the surface of Mars, which do not involve water. In their paper published ...

Ice in Ceres' shadowed craters linked to tilt history

March 22, 2017

Dwarf planet Ceres may be hundreds of millions of miles from Jupiter, and even farther from Saturn, but the tremendous influence of gravity from these gas giants has an appreciable effect on Ceres' orientation. In a new study, ...

Giant magnetic fields in the universe

March 22, 2017

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

adam_russell_9615
not rated yet Mar 28, 2014
The trouble with lunar eclipses is they always happen at night!
jk

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.