It’s hard to evaluate the major astronomical event coming up on Monday, November 11, 2019. It certainly sounds spectacular: the planet Mercury will visibly cross the face of the Sun. The next such transit won’t occur until 2032. Bob Berman has information on when and how to see this rare astronomical event.
What Does Mercury Transit Mean?
Mercury, the planet closest to our Sun, will “transit” or pass directly in front of the Sun! As Mercury passes beween the Sun and Earth, it appears as a tiny black dot moving across a bright solar disk.
The word “transit” may sound familiar because in 2004 and 2012 we saw transits of Venus, which anyone could observe with their naked eye using proper protection such as standard solar eclipse glasses. Only Venus and Mercury—planets that orbit the Sun inside of Earth’s orbit—ever transit the Sun, as seen from Earth.
When Can You See the Mercury Transit 2019?
An additional “plus” is that most or all of this transit will be visible from the entirety of North and South America except for Alaska.
The middle of the event, which indeed will be seen from absolutely all those places, happens at 10:20 AM Eastern Time, or 7:20 AMPST. With the help of some special equipment (detailed below), anyone who can see the Sun can look for a small, perfectly round black dot near the Sun’s center.
How long Does the Mercury Transit Last?
If you wish to watch the entire transit, this one lasts about 5-1/2 hours. Here is more detail by time zone:
Eastern Time: Mercury will come into view on the Sun’s face at 7:36 A.M.EST, transit across the Sun’s orb at 10:20 A.M.EST, and exit around 1:04 P.M. EST.
Central Time: Mercury will come into view on the Sun’s face at 6:36 A.M.CST, transit across the Sun’s orb at 9:20 A.M.CST, and exit around 12:04 P.M. CST.
Mountain Time: The Sun is below the horizon at first, but will transit across the Sun’s orb at 8:20 A.M.MST, and exit around 11:04 A.M. MST.
Pacific Time: The Sun is below the horizon at first, but will transit across the Sun’s orb at 7:20 A.M.PST, and exit around 10:04 A.M. PST.
How to Safely View the Transit of Mercury
If you want to see the transit of Mercury for yourself you must be very careful. We’re talking about staring at the Sun. Those who observed one or both of the Venus transits not too many years ago may wonder why this is a challenge. It’s because Mercury is only half the size of Venus and is also twice as far from us. All told, it appears only one quarter Venus’s size, and this makes it only visible through a telescope.
Therefore, it’s critical to view through telescopes with solar filters. Specifically:
The telescope must have a full aperture sun-blocking filter. Back in the bad old days more than 40 years ago, many telescope manufacturers who were either oblivious to the hazard or are less afraid of lawsuits, routinely supplied a “solar filter” to be screwed onto an eyepiece. If you happen to have one of these old instruments stored in the basement, don’t use it. They’d let the sun’s image be fully amplified by the telescope’s optics so that enormous heat was focused onto those filters. If it would suddenly crack under the stress, well, say goodbye to the sight in that eye. So, you need the kind of filter the covers the entire aperture of the telescope tube, blocking the light before it ever reaches the main mirror or lens. If you’ve got that, you’re in business.
There are also specially designed solar telescopes that would be perfect for this. If you know someone who has one, ask them what they’re doing Monday.
Watch Online: Those who lack the proper equipment can watch it for free on their computer screens on Web sites such as Slooh.com, where you’ll hear me supply some of the narration. Through Slooh’s highly-specialised solar telescope, you can not only see the entire transit but also view solar features such as huge plumes of superheated plasma spewing out from the Sun’s limb as Mercury transits its face.
Since Mercury completely circles the Sun four times every year, you’d think it would cross the Sun’s face frequently. Alas, its orbit is tilted a full seven degrees from edgewise so that it aligns perfectly between the Earth and the Sun only 13 times per century. The next opportunity to witness a transit of Mercury will be in 2032.
So it’s rather a rare event indeed. It’ll probably make headlines. But is it visually spectacular? You be the judge.