Guernsey Press

Rare chance to see Mercury transit the sun

YESTERDAY presented a once in a 13-year chance to see Mercury transit across the sun.

Published
Picture By Peter Frankland. 11-11-19 Observatory. Mercury passing inbetween the Earth and the Sun..Open day at La Societe Guernesiaise Astronomical Observatory. Jean Dean peers through a telescope.. (26327087)

Visitors flocked to see the rare cosmic event at the island’s observatory.

Webcams, solar projector boxes, internet live streams and telescopes all pointed towards the sun showed the tiny pinprick of Mercury traverse the diameter of the sun.

Astronomy section member Jean Dean said: ‘This is a significant event because the two inner planets do not cross very frequently.

‘Mercury only does about 13 times every century and Venus only twice. The next time Mercury will is in 2032 and the next time Venus will is 2117 which I doubt very many of us will see at all.

‘So it is quite a rare astronomical event.

‘Historically, astronomer Johanne Kepler predicted that Mercury would transit across the sun back in 1631, he did not actually live to see this.

‘But some astronomers did and when the prediction proved correct it was the first time man had got some true understanding of the stars.

‘Later, British astronomer Edmund Halley discovered that if the transition is observed through different points on the Earth then with some simple trigonometry it is possible to work out the distances to points in the solar system.’

Picture By Peter Frankland. 11-11-19 Observatory. Mercury passing inbetween the Earth and the Sun..Open day at La Societe Guernesiaise Astronomical Observatory. Jenny Webster peers through a telescope.. (26327083)

Fellow member Elaine Mahy was up at the Rue du Lorier observatory with her invention she calls the ‘solar projector box’.

‘I made it about four years ago for a solar eclipse which turned out to be very cloudy but I realised in 2016 that it came in very handy for the transition of Mercury.

‘It is just a scope in a cardboard box that reflects light onto a white board at the rear of box allowing the human eye to observe the sun. It is quite rudimentary but highly effective, I always enjoy hearing people’s reactions to seeing it,’ said Ms Mahy.

The next time Mercury transits across the sun will be 2032.

Picture By Peter Frankland. 11-11-19 Observatory. Mercury passing inbetween the Earth and the Sun..Open day at La Societe Guernesiaise Astronomical Observatory. Taken through a telescope.. (26327091)

Then it will be more easily viewable in most of Asia, Europe, Africa, Australia, and South America.

However, people in North America will have an even longer wait – the next Mercury transit visible there will not happen until 2049.