What's New: January 2019

A Weekend Lunar Eclipse

The year starts off with a partial solar eclipse visible in East Asia and the North Pacific, with peak eclipse in a remote portion of Siberia.

A much more accessible total lunar eclipse occurs a half of a Moon orbit later, on January 20 – 21. This eclipse will be visible in its entirety from anywhere in the Western Hemisphere, with portions of it visible from parts of Europe, Africa, and the eastern Pacific.

A solar eclipse occurs when the Moon appears to pass between us and the Sun, with the Moon's disk blocking some or all of the Sun behind it. A lunar eclipse happens when the Moon, in its orbit around Earth, happens to pass into Earth's shadow.

As you can imagine, the Earth casts a long, cone-shaped shadow into space. The Moon's orbit around the Earth is tilted with respect to the plane of Earth's orbit around the Sun, so most of the time, the Moon misses the shadow cone, going "above" or "below" it. But on occasions such as this month’s eclipse, the Moon enters the Earth's shadow.

Now for some complications: the Earth’s shadow actually has two parts: the umbra and the penumbra. When the Moon enters the penumbra, points on its surface still see portions of the Sun that are not completely blocked by Earth. Once parts of the Moon are in the umbra, the Earth blocks all direct sunlight from reaching them. In a total lunar eclipse, the entire disk of the Moon passes through the umbra. The entire process takes more than 5 hours, as seen in the diagram below. (The times in the diagram are in Universal Time; please adjust to your time zone as appropriate. For example, Eastern Standard time is UT minus 5 hours.)

total lunar eclipse timeline