Skygazers are gearing up for what is being described as one of the biggest astronomical events of the decade.
The total solar eclipse – when the moon completely blocks the face of the sun – is taking place in the early afternoon of April 8.
The spectacle – which briefly turns the outdoors dark in daytime – will be visible for an estimated 32 million people along a narrow strip of North and Central America.
It will mark the first total solar eclipse visible anywhere in the world since December 2021, and the first seen from the US since August 2017.
Although the total solar eclipse visible won’t be seen from the UK, a partial solar eclipse – where just a chunk of the sun is covered – could be visible in western areas like Cornwall, Wales and Ireland.
A total solar eclipse happens when the moon passes between the sun and Earth, completely blocking the face of the sun
Total solar eclipse is seen near Hopkinsville, Kentucky on August 21, 2017. On April 8, 2024, the moon will cast its shadow across a stretch of the US, Mexico and Canada, plunging millions of people into midday darkness
Dr Greg Brown, astronomer at the Royal Observatory Greenwich, said: ‘For observers in North America, this is your best chance to see a total solar eclipse this decade.
‘Nothing quite compares to the day-turned-night that comes from a total eclipse.’
On April 8, the total solar eclipse will be visible along a ‘path of totality’, starting in Mexico and moving through Texas where it will travel up to New England and finish in Canada.
In any one location along the path of totality, people will see a partial eclipse followed by the total eclipse, and then a partial eclipse again.
Whatever your location along the path of totality, the total eclipse should be visible for about four minutes.
‘North America won’t lie in the path of totality of a solar eclipse again until 2033 when an eclipse will graze Alaska,’ Dr Brown added.
‘The rest of the US and Canada will have to wait for 2044 and 2045 when there will be another pair of solar eclipses to enjoy.’
Like any eclipse, it’s important not to look directly at the sun with the naked eye while the event is happening – not even through sunglasses, binoculars or a telescope.
A simple pinhole projector, solar eclipse viewing glasses, which can be purchased online, or special solar filters are much safer.
According to Dr Brown, a total solar eclipse happens when the moon and the sun line up ‘perfectly’.
He told MailOnline: ‘It’s only when it perfectly lines up, so that the centre of the sun and the centre of the moon pass in front of one another – that’s when you get a total solar eclipse.’
Where the total solar eclipse is visible is known as the point of totality – but this is only the very centre of the moon’s constantly-moving shadow.
Elsewhere in the moon’s shadow, further away from the centre, a partial solar eclipse will be visible on April 8 instead.
‘The partial solar eclipse is because the moon’s centre is slightly above or slightly below the sun’s centre, from our point of view,’ said Dr Brown.
Snapshot during a total solar eclipse: Red line shows the perfect alignment of the centre of the sun (left) and the centre of the moon (middle) with the Earth (right). On Earth, the very centre of the moon’s shadow sees a total solar eclipse (where the whole of the sun is blocked). The rest of the shadow sees a partial solar eclipse (where part of the sun is blocked). People in the rest of the shadow see a partial solar eclipse because the moon’s centre is slightly above or slightly below the sun’s centre, from the viewer’s perspective. In effect, part of the sun ‘peeps out’ because the sun isn’t totally blocking it
The April 8 total eclipse will sweep across the continent, starting in Mexico and moving eastwards through Texas where it will travel up to New England and finish in eastern Canada
Shaded area marks the moon’s shadow moving over the Earth on April 8; people in this area will only see a partial eclipse unless they’re in the path traversed by the black dot right in the centre – in this case they’ll see a total solar eclipse
As Dr Brown explains, another type of solar eclipse – known as the ‘annular solar eclipse’ – can also occur when the sun and moon are perfectly lined up (as viewed from Earth).
An annular solar eclipse is when the moon doesn’t completely cover the sun, resulting in a halo of sunlight known as a ‘ring of fire’ visible around the silhouette of the moon.
Whether we get an annular or total solar eclipse depends simply on the distance of the moon from Earth, Dr Brown said.
Don’t forget that the moon’s orbit around Earth is elongated and not perfectly circular – so there’s points when it’s closer to us than normal.
On April 8, because the moon will be at the closest point to Earth in its orbit (known as ‘perigee’), it will appear bigger – big enough to block out the whole of the moon.
In contrast, during an annular solar eclipse, the moon is not at perigee.
‘In an annular eclipse, the moon is too far away, so it’s not quite large enough to block the entirety of the sun – even if everything lines up perfectly,’ Dr Brown told MailOnline.
It’s worth remembering that the moon is constantly moving – and therefore so will its shadow over Earth on April 8.
The whole shadow, about 4,000 miles wide, will be travelling at around 1,500 miles per hour.
Don’t forget that the moon’s 29.5-day orbit around Earth is elongated (not perfectly circular), so there’s a point when the moon is closer to Earth than the rest of the time (‘perigee’)
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April 8: This colour coded map shows the path of totality as a dashed line in deep pink. It’s here where the whole of the sun will be blocked by the moon. Further out are areas that will see partial eclipse. Here, the percentage of the sun blocked in these colour-coded areas is given
Sadly for Brits, it’s unlikely that much of the UK will see even a partial eclipse on April 8.
In places like Ireland and perhaps Cornwall, Wales and the west of Scotland, a small percentage of the sun – about 5 per cent – will appear blocked by the moon.
But places like London, and other regions further east into mainland Europe, have no chance of witnessing the event.
‘For the most of the UK, we won’t see anything at all, partly because the sun will be below the horizon from out point of view,’ Dr Brown said.
Unfortunately, the next total solar eclipse isn’t visible in the UK for another 66 years.
Occurring on September 23, 2090, it will be the first total solar eclipse visible from Britain since August 11, 1999, and the first visible from Ireland since May 22, 1724.
After April 8, the next solar eclipse is an annular solar eclipse on October 2, but it will only be visible from the southern tips of Argentina and Chile, as well as Easter Island in the southeastern Pacific Ocean.
Other parts of South America including Brazil, Ecuador, Paraguay and Peru as well as Hawaii and New Zealand should see a partial solar eclipse that day.