Those gazing up into the sky on Wednesday night are set to witness an unusual event: a super worm moon that coincides with the equinox.
It will be the third time this year a full moon has occurred near to the moon’s closest approach to the Earth – making it a supermoon – and will be the last such event in 2019. Those venturing out can expect to see the moon looming larger than usual in the night sky.
Its unusual moniker is rooted in agricultural practices and is a nod to the emergence of worms in the soil around the time of the March full moon, although it is not the only sobriquet applied to a full moon in March: such an event is also known as a sap moon.
“A lot of the names that are used to describe the full moons throughout the year come from a native North American tradition so things like the appearance of wolves or the snow,” said Tom Kerss, an astronomer at the Royal Observatory Greenwich.
However, it isn’t only the name that makes this lunar event different: this supermoon will occur on the same night as the northern hemisphere’s spring equinox where day and night are of the same duration – albeit with full illumination taking place at just before 2am GMT, a few hours after the equinox itself.
“We don’t always have, during the equinox, a full moon, it can be any phase of the moon,” said Dr Emily Brunsden, director of the University of York’s Astrocampus.
Sophie Yeomans, a meteorologist at the Met Office, said there is a good chance that sky-gazers, particularly in England, will be able to catch a glimpse of the super worm moon.
“Western Wales might be quite difficult, north-west England, some parts of Northern Ireland and Western Scotland I think might struggle a bit,” she said. “Elsewhere there will be gaps in the cloud, it’s just a matter of waiting.”
Kerss said it is a rare event for a supermoon to coincide with the equinox. “We have been looking at the records for the occurrence of what we call supermoons today. The last time that this occurred so close to the point of the equinox was in the year 1905, in March over 100 years ago,” he said, although he noted the term “supermoon” is a recent term. “It looks to us that the next time we see this with the spring equinox, at least, won’t occur until the year 2144. So for most of us this could be called a once in a lifetime coincidence.”