Everything you need to know about observing the transit of Mercury on 11 November
On Monday 11 November 2019 the tiny planet Mercury will pass between Earth and the Sun. Jamie Carter looks at how, why and where to observe this rare event
To the Romans, the planet Mercury was Mercurius, the messenger of the gods. To modern astronomers, it’s the smallest, hottest and fastestmoving planet in the Solar System, and the one that’s nearest to the Sun. Rarely glimpsed by sky-watchers because it’s usually lost in the Sun’s glare, Mercury will nevertheless provide one of the most arresting celestial sights of 2019 when, on Monday 11 November, it will pass across the face of the Sun. It’s an event that’s among the rarest of predictable astronomical phenomena.
From Earth, only Mercury and Venus, the two innermost planets in the Solar System, can be seen to transit the Sun’s disc. For observers in the UK the event will begin around 12.35pm and continue past sunset, at around 16.22pm. Even though the UK won’t get the best view of the event, it will be well worth trying to observe it through a solar telescope, not least because you don’t need to witness the whole thing; a short observation will do (and with 75 per cent chance of cloud cover in mid-November that’s probably a realistic goal). But also because it won’t happen again until 13 November 2032.
Of course, Mercury’s trip across the Sun isn’t the only transit we get to see. A more famous event is the transit of Venus, an event that last occurred in 2012. But even if you consider the transit of Mercury to be a smaller and less impressive affair, it’s something of a moot point since the next transit of Venus doesn’t take place for another 98 years. Besides, observing the transit of Mercury can be just as rewarding.
Starting small
“I thought it was going to be a very small dot because Mercury is 1/150th the diameter of the Sun, and I thought there was no way I would see it with my three-inch refractor,” says Eric Emms, an amateur astronomer and member of The Baker Street Irregular Astronomers in London, who observed a previous transit. “I was surprised at how