As the eclipse plunges the UK and other places into darkness this Friday, two other rare if less spectacular celestial events will be taking place, too: a Supermoon and the Spring equinox.

A Supermoon, or perigee moon, happens when the full or new moon does its closest fly-by of the Earth, making it look bigger than it normally does. And the spring equinox refers to the time of the year when the day and night are of equal duration, mid-way between the longest and shortest days.

The solar eclipse refers to a phenomenon where the sun and moon line up, so that the latter obscures the former. And while it won’t be affected by the two other events, it is rare that the three events happen even individually.

Supermoon

Most of the time, there are between three and six Supermoons a year. There is set to be six in 2015, two of which have already happened. The next will take place on March 20, the day of the eclipse, and the others will come in August, September and October.

In pictures: The biggest supermoon of 2014 Show all 12 1 /12 In pictures: The biggest supermoon of 2014 In pictures: The biggest supermoon of 2014 Perigee moon The supermoon rises above the U.S. Marine Corps War Memorial in Arlington, Virginia Getty Images In pictures: The biggest supermoon of 2014 Perigee moon The full moon descends behind the Nossa Senhora da Penha Church in Rio de Janeiro, Brazil YASUYOSHI CHIBA/AFP/Getty Images In pictures: The biggest supermoon of 2014 Perigee moon The supermoon, rises at Ipanema beach in Rio de Janeiro, Brazil YASUYOSHI CHIBA/AFP/Getty Images In pictures: The biggest supermoon of 2014 Perigee moon In images from NASA, this supermoon is seen over the The Peace Monument on the grounds of the United States Capitol in Washington, DC Bill Ingalls/NASA via Getty Images In pictures: The biggest supermoon of 2014 Perigee moon The supermoon rises through the clouds behind the 'Motherland' statue, part of the WWII memorial complex, in Kiev, Ukraine AP In pictures: The biggest supermoon of 2014 Perigee moon The supermoon appears behind the Torrelodones Tower in the city of Torrelodones, near Madrid, Spain Pablo Blazquez Dominguez/Getty Images In pictures: The biggest supermoon of 2014 Perigee moon People gather in the park as the perigee moon rises in Madrid AP In pictures: The biggest supermoon of 2014 Perigee moon A view of perigee moon rising behind The Shard in London PA In pictures: The biggest supermoon of 2014 Perigee moon The supermoon is seen rising over New York City from Weehawken, New Jersey, USA EPA In pictures: The biggest supermoon of 2014 Perigee moon The supermoon rises through the clouds behind the "Motherland" statue, part of the WWII memorial complex, in Kiev, Ukraine AP In pictures: The biggest supermoon of 2014 Perigee moon The perigee moon is seen on August 10, 2014 from Arlington, Virginia. AFP/Getty Images In pictures: The biggest supermoon of 2014 Perigee moon The pictures of the supermoon taken by cosmonaut Oleg Artemyev from space Twitter/ Oleg Artemyev

Eclipses can only happen at new moon, when the moon appears is entirely in shadow. And the spectacular Supermoon images that are often spotted can only happen when the moon is full, since it can only be seen then.

As a result, only the last three Supermoons of this year will be visible — because the moon is new rather than full on March 20, it won’t be seen. But it will be gliding past us closer than ever, and its shadow will be visible as it blocks out the sun on Friday morning.

Spring equinox

The equinox will also happen on March 20. While it won’t have any discernable, direct impact on how the solar eclipse looks, it will contribute to a rare collision of three unusual celestial events.

On March 20, the Earth’s axis will be perpindecular to the sun’s rays — which only happens twice a year, at the two equinoxes. After that, it will start tipping over, making the days longer in the northern hemisphere.

As such, the equinox has long been celebrated as a time of beginning and renewal, by a number of historic cultures, and is linked to Easter and Passover.