Next week a ‘blood moon’ will be visible across large parts of parts of North America.
On Wednesday morning at 6:25am Eastern time the moon will pass into Earth’s shadow, making it appear red.
The event will last about an hour and, owing to the moon’s position in its orbit, will be 5.3 per cent larger than the previous blood moon on 15 April.
The event is the second in a sequence of four blood moons called a tetrad, which occur in six-month intervals.
The next will happen on 4 April 2015 and the last on 28 September 2015.
For the latest blood moon the moment of greatest eclipse will occur at 6:54am Eastern time, after starting at 6:25am, while the eclipse lasts a total of 59 minutes – ending at 7:53am.
Owing to the orientation of the moon the southern half will appear much darker than the northern half because it will lie deeper in Earth’s shadow.
It will be most visible in the northwestern third of America, where all stages can be witnessed.
Farther east in the US, various phases will occur after moonset.
None of the eclipse will be visible from Europe, Africa or the Middle East though.
It’s not often that we get a chance to see our planet’s shadow, but a lunar eclipse gives us a brief glimpse.
During these rare events, the full Moon rapidly darkens and then glows red
At the eclipse’s peak the moon will enter the Earth’s full shadow, the umbra.
At this stage, the Earth’s atmosphere will scatter the sun’s red visible light, the same process that turns the sky red at sunset.
As a result, the red light will reflect off the moon’s surface, casting a reddish rust hue over it.
Although there are four lunar eclipses in fairly close proximity, the event is not that common.
On average there are two eclipses a year but some are penumbral – which means the moon only passes through the outer portion of Earth’s shadow – so the effect is much less noticeable.
And other eclipses see just a shadow cast on the moon with no red effect.
This ‘blood’ appearance comes from the refraction of the sun’s light through Earth’s atmosphere – much like what is seen at a sunset or sunrise.
Eclipses do not follow any particular pattern though, so getting four ‘blood moons’ in a row is rare.