Black supermoon 2015: when is it and can I see it?
Today's black supermoon will coincide with a solar eclipse, prompting a rash of amateur astronomy
With 2015's solar eclipse done and dusted - and in most parts of the UK obscured by cloud - attention now turns to Friday's second celestial events. This evening heralds the third supermoon of 2015, but it too may prove something of a disappointment.
When is the 2015 supermoon?
We've already had two supermoons so far this year, and the third will occur this evening. After today's event, there will be three more this year, in August, September and October.
What is a supermoon?
Supermoon events cause the moon to appear bigger and brighter than usual. They occur when the moon is full or new when its elliptical orbit reaches its closest point to Earth – known as the perigee. When in perigee, the moon is 360,000km away from us, about 50,000km closer than when it is at its apogee, the furthest it gets from Earth.
What's special about a black supermoon?
A black supermoon occurs when the perigee coincides with a new moon rather than a full moon. The result is significantly less spectacular: instead of an extra large, bright moon, all we can see is a slightly larger dark spot in the sky where the moon should be. For most observers, there will be nothing to see at all.
Where did the name come from?
Astrologer Richard Nolle coined the term, back in 1979. As Nasa scientist James Garvin explains in International Business Times: "It is called a supermoon because this is a very noticeable alignment that, at first glance, would seem to have an effect. The 'super' in supermoon is really just the appearance of being closer."
How often do they happen?
Unlike other celestial events, supermoons are actually relatively common. They generally happen around once a year, though there were three last summer and there will be a total of six in 2015.
What is the best way to view supermoons?
Although today's supermoon can't be seen, the last three supermoons of this year will be visible. Lunar buffs at Space.com recommend viewing them just after the moon rises or before it sets, when it is close to the horizon. If you watch as it dips behind buildings or trees, an optical illusion is produced, which makes the moon seem even larger than it really is.
How did people regard supermoon events in the past?
An old European old wives’ tale suggested that when the moon entered a new phase it was a favourable time to start a new business, The Examiner says. Black supermoons were regarded as particularly auspicious, the site says.
Pagan traditions suggest that black supermoons were good times to cast spells or perform rituals. And Germanic tribes believed that supermoons drew their power from the deity Frigg, who lived on the moon.
Will these supermoons have any impact on earth?
Full and new moons generally cause spring tides, so those who live on the coast could experience higher tides than normal for this time of year. Speculation that a previous supermoon caused the Japanese earthquake has been dismissed by Nasa. However, British coastguards have blamed a previous supermoon for the stranding of several ships.