Stargazers are in for a treat next month, for the first “Transit of Mercury,” in three and a half years, and the last one to be seen here for the next three decades.
Just what is a “Transit of Mercury?” We asked retired Pensacola State College astronomer Wayne Wooten.
“Mercury and Venus can, on rare occasions, can pass directly between us and the sun and appear as little black dots moving across the sun’s face,” Wooten said. “We’ll have a chance for Mercury to do it on Veterans’ Day, November the 11th, 2019.”
If the weather cooperates, Wooten recommends you take the time to observe the transit – because the next one is in 2049 – and be sure to use eye protection as you would with a solar eclipse. Plus, you have to get up pretty early that morning.
“For us locally we’ll get to see the whole kit-n-caboodle,” said Wooten. “First contact of Mercury with the sun will be at 6:35 a.m. And it will take it five and a half hours to go all the way across the sun, leaving the sun at noon.”
The Escambia Amateur Astronomers will set up telescopes outside the Pensacola State College Planetarium on Monday for the public to observe.
“We’ll have safety filtered telescopes outside the planetarium; bring your smart phones and cameras. Normally, we would say we’d also be observing a lot of other stuff happening on the sun; but it is ‘solar minimum [little if any solar activity].’ Maybe we’ll get lucky [by Nov. 10] and there will be a few sunspots.”
Transits of Mercury with respect to Earth are much more frequent than transits of Venus, with about 13 or 14 per century -- in part because Mercury is closer to the Sun and orbits it more rapidly. Looking way, way ahead, Venus’ next solar transit will occur in December, 2117. Wooten says the Earth has a similar event.
“Any of the outer planets can occasionally see us go in front of the sun, said Wooten. “The only one that’s actually been observed with, is one of our robots on Mars a few years ago.”
The transit phenomenon is relatively common across the solar system, says Wooten, because the plane of the planets is “amazingly flat.”
“From Mercury all the way up through Neptune, the planets’ orbits don’t tilt more than about six or seven degrees above or below the sun’s equator,” Wooten said. “So, all of those planets are subject to, on occasion, passing in front of the sun as viewed from the outer planets.”
As mentioned, the next Mercury Transit after next month’s isn’t for another 30 years from where we stand. But Wooten does say there’s another one before that elsewhere.
“Actually, if you are willing to travel the world you would be able to pick up another one I think, in 2034,” said Wooten. “But for us here, if you want to stay over on the Western Hemisphere, the next one for us here will be 2049.”
More information on the Mercury Transit – and other features of the universe – can be found in Wayne Wooten’s monthly column at www.wuwf.org.
“My latest column for the November Sky goes into more detail and shows spectacular photographs taken by astronomy club member Tom Dracon,” said Wooten. “Tiny Mercury, only a third of the size of the earth, with a much larger sunspot – which was in fact bigger than the earth.”
Transits of Mercury currently occur only in the months of May or November, because the orbits of Mercury and Earth around the sun are slightly tilted relative to one another -- only overlapping at two points, known as nodes.