Mercury is set to make a transit across the sun on Monday morning for the last time until 2032. A pinprick of darkness will puncture a small hole in the sunlight as the planet traverses the solar disk during a 5.5-hour stretch, starting at 7:35 a.m. Eastern time. And while you won't be able see it without protective glasses and heavy-duty telescope equipment, there are still plenty of ways to enjoy the show.
- What's a transit?
Remember the famous solar eclipse of Aug. 21, 2017? You probably donned a pair of ISO-certified, polycarbonate glasses and stared up at the sky in wonder. That happened because the moon briefly blocked the sun. In a narrow path of totality, day turned to night as the sunlight was extinguished.
This time around, it will be Mercury standing in front of the sun. Mercury is actually a little bigger than the moon - it's about 874 miles larger in diameter. But Mercury is much farther from Earth. That's what makes it look so tiny from Earth.
As such, even though Mercury will pass in front of the sun, it won't be able to block much sunlight. That's what distinguishes a transit from an eclipse. During a transit, the interceding body is not sufficiently large to cover whatever it's moving in front of.
- Where will it be visible?
The transit will begin shortly after sunrise on the East Coast. By the time the sun rises on the West Coast, the transit will be well underway, with Mercury nearing its deepest venture into the solar disk. The transit will wrap up at 1:04 p.m. Eastern time.
In Europe and western Asia, the transit will occur during sunset. Over most of South America and the eastern United States/Canada, the whole event will coincide with the daylight hours, meaning the sun will be visible during the entire event.
For the Pacific Coast, it's a sunset transit.
Australia, the Maritime Continent, Southeast Asia, much of China and the Koreas will miss out on the event entirely.
- Will eclipse glasses work?
Nope. The tiny dot you're looking for is just too small to see, even with eye protection. According to NASA, "Your best bet is a telescope with a certified sun filter, but other options include solar projection boxes and sun funnels."
You should never, under any circumstances, stare directly at the sun without proper protection. Though it may be tempting in this case, because mercury is so small in comparison to the sun, you should not combine eclipse glasses and binoculars. That could cause permanent and irreversible eye damage.
- How can I safely enjoy the show?
Live-streaming the event is probably your best option. NASA's Solar Dynamics Observatory, which is a space-based instrument staring at the sun, will be capturing imagery as Mercury photobombs the sun. You can tune into the live stream here. NASA and the European Space Agency also will provide updates from the Solar and Heliospheric Observatory (SOHO).
A few readers have asked about producing pinhole cameras as they did for the eclipse. Unfortunately, that won't work in this case, either, because of the relative size of the two objects. Instead, projections using protectively covered telescopes could work, according to Space.com.
- When's the next one?
Mercury transits occur 13 times per century, and the next one is slated for Nov. 13, 2032. Mercury transits typically happen in May or November. That's mainly because of how Earth aligns with Mercury's orbit.
In 2004 and 2012, Earth was treated to some rather spectacular transits of Venus. Our second planet from the sun, which is much larger and closer, appeared more noticeably on the solar disk. (Unfortunately, the next transit of Venus isn't until 2117.)