Supermoon: A spectacle in the sky tonight

Why this full moon is called a supermoon, and how it is different from other supermoons

Published:November 14, 2016 12:29 am
supermoon Closest full moon and Farthest full moon
The moon’s elliptical orbit means that its distance from Earth varies throughout the year; the full moon closest to Earth appears 14 per cent large than the farthest from the planet. (Source: NASA website)

What is a supermoon?

When the moon is full as it makes its closest pass to Earth, it is known as a supermoon.

Why “closest” pass?

The moon’s orbit around Earth is slightly elliptical, so sometimes it is closer and sometimes farther away from the planet. The average distance between Earth and the moon is 384,500 km but the actual distance varies throughout the year, between 363,396 km and 405,504 km (Figure 1). To be called a supermoon, the moon has to be both at its closest distance from Earth as well as full.

Are supermoons rare?

Not really. One in about every 14 full moons is a supermoon, University of Wisconsin astronomer Jim Lattis told Reuters. By the time 2016 ends, it will have seen three supermoons — on October 16, November 14, December 14.

So what makes Monday’s event so significant?

The fact that it will be the closest in recent memory. On November 14, 2016, the full moon will be 356,508 km from Earth, the closest since January 1948, when it was nearly 47 km closer. There won’t be another such supermoon until 2034, when it will be even closer to Earth, at 356,445 km.

When exactly on Monday?

At 6:23 am EST (11:23 am GMT), which would make it around 4:53 pm IST, or before sunset in most parts of India. Not that it matters, because the size will not look very different after nightfall — or even on the evening after.

How large?

The full moon will appear 14 per cent larger in diameter than when seen at the farthest point (Figure 2). It will also be 30 per cent brighter than the smallest full moon, though only 15% brighter than the average full moon.

Can one afford to miss it?

It would takes an expert eye to distinguish between this supermoon and the next. So if a casual viewer misses it, he or she can make up by viewing the next supermoon, in December. The fact that the differences are so subtle has, in fact, led to some astronomers questioning the fuss about Monday. NASA planetary geologist Noah Petro, on the other hand, told AP, “Ultimately, people should be more geared toward just getting outside and enjoying it.” What counts, he said, is getting people “talking, thinking and caring about the moon”.

 

Compiled from a post on NASA website & AP and Reuters reports