“Perfect alignment” between Sun, Mercury and Earth visible from Portugal on Monday

It’s a rare planetary transit – and one that should be easily visible from Portugal next Monday (May 9): the moment when the Sun, planets Mercury and Earth “perfectly align” – a must-see on any star-gazer’s calendar.

With Nasa transmitting the seven-hour passage of Mercury between Earth and the Sun over the Internet, here Lisbon’s Astronomical Observatory will be providing telescopes in front of the C8 Science Faculty at the University of Lisbon, as well as in Tapada da Ajuda.

Whether or not the transit – starting 13 minutes after midday and ending at 7.41pm – will be easy to follow will depend very much on weather conditions.

Diário de Notícias explains that the “point of greatest proximity” will be at 3.56pm – but that given the difference in size between the Sun and Mercury, the passing will appear as no more than a black dot.

This is the kind of planetary event that happens only a few times every century, explains DN.

The last time it happened was in 2006, and the next two occasions will be 2019 and 2032.

The paper stresses that no-one should try and view the transit without specially-filtered telescopes or binoculars.

As Nasa’s Louis Mayo explained: “Astronomers get excited when any two things come close to each other in the heavens”.
The fact that this involves three celestial bodies “is a big deal”.

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