On Tuesday, October 25, 2022 a New Moon will cause a partial solar eclipse for Eurasia. What observers will see depends on where they are, but in the UK about 15% of the Sun will be blocked by the moon right in Russia – where maximum eclipse occurs – an 82% eclipse will be observable.

As well as being an interesting astronomical event – albeit one that demands all of service where solar eclipse safety glasses – it will set up a total lunar eclipse (a.k.a. “Blood Moon”exactly 2 weeks later that will be seen across North America.

Why does the New Moon not block the Sun every single month? What causes solar eclipses? And why does a lunar eclipse follow this solar eclipse?

We’re in a “eclipse season” during which there will be two eclipses—one of the Sun by a New Moon and one of the Full Moon by the Earth.

What is an ‘eclipse season?’

Every 173 days, for between 31 and 37 days, the Moon is lined-up perfectly to intersect the ecliptic—the aptly-named apparent path of the Sun through our daytime sky and the plane of Earth’s orbit of the Sun. The result, of course, is a short season during which two—and occasionally three—solar and lunar eclipses can occur.

Just like clockwork, a solar eclipse or a lunar eclipse marks a point in the orbit of the Earth by the Moon that sets-off a chain of events that then causes the other kind of eclipse half-an-orbit later.

Why there isn’t an eclipse every month

The Moon’s orbit of Earth is tilted by 5º to the ecliptic, but it must cross the ecliptic twice each month. Those two positions are called nodes. Usually it reaches these nodes when the the Sun and Moon seem far apart from our point of view on Earth. This is why an eclipse does not occur each and every New Moon (because the Moon is above or below the Sun) and full Moon (because the Moon is above or below Earth’s shadow).

An eclipse season can only happen when the Moon is perfectly lined-up to intersect the ecliptic. When it does you get two of these:

 

• A lunar eclipse at full Moon when the Earth is between the Sun and Moon, blocking sunlight from reaching the lunar surface.
• A solar eclipse at New Moon when the Moon is between the Earth and Sun.

 

When the Moon reaches one of those nodes to cause on kind of eclipse it’s going to hit the other eclipse node two weeks later. Occasionally it hits a node for third time two weeks after that.

When are the eclipse seasons in 2022?

There are two eclipse seasons in 2022, each of them bringing one partial solar eclipse and one total lunar eclipse:

Eclipse season #1

 

• April 30, 2022: partial solar eclipse (parts of Chile, Argentina and Antarctica will get the best views).
• May 16, 2022: total lunar eclipse (best seen in eastern North America and South America).

 

Eclipse season #2

• October 25, 2022 partial solar eclipse (Europe and the Middle East will get the best views).
• November 7/8. 2022: total lunar eclipse (best seen in western North America and the Pacific).

Note: never look at the partial phases of any solar eclipse without proper eye protection—and that means solar eclipse glasses. Lunar eclipses are completely safe at all times.