On Monday, you can witness Mercury in motion as the tiny planet waltzes across the face of the sun. This celestial dance, known as the transit of Mercury, last occurred in 2016 and will not happen again until 2032. North American skywatchers will have to wait until 2049 for an encore.
“This is a poetic moment to me where you’re seeing Mercury doing this amazing thing: crossing in front of this gigantic ball of nuclear burning that is our sun,” said Jackie Faherty, an astrophysicist at the American Museum of Natural History in New York.
From here on Earth, our solar system’s innermost planet will appear as a black dot cruising over a gigantic glowing red disk — although don’t look directly at it, as staring into the sun will damage your eyes.
But if you’re lucky enough to watch the transit with proper viewing equipment, you’ll be taking part in an astronomical tradition that dates back to at least 1631 when French astronomer Pierre Gassendi observed the phenomenon. You’ll also experience firsthand how astronomers today hunt for exoplanets orbiting stars light years away.
What is a transit of Mercury?
Cosmically speaking, a transit is when a celestial body — like a planet or moon — moves between a larger object and some observers, typically us on Earth.
The most famous transit is a solar eclipse, when the moon passes in front of the sun, like during the 2017 Great American Eclipse. There is also a lunar eclipse, where Earth passes directly between the sun and the moon, casting a reddish shadow on the lunar surface.
Because Earth is the third planet in our solar system, we can see the transits of Mercury and Venus. Mercury transits occur about 13 times every century, according to NASA. Because of Mercury’s and Earth’s orbits and tilts, such crossings tend to occur near May 8 or Nov 10.
Transits of Venus are even rarer. The last one was in 2012 and the next won’t be until 2117.
Where and when can I watch it?
The entire show will take about five hours, 30 minutes. Those watching from the East Coast of the United States will be in luck. The entirety of the transit will be visible during daylight hours.
Viewers on the West Coast of the United States can catch part of the show after the sun rises. People living in South America, western Africa and western Europe will also see much of the event. Parts of Australia and southern and west Asia will also catch some of the trip.
According to timeanddate.com:
— Mercury will make first contact with the sun at 7:35 a.m. Eastern time.
— It will be closest to the sun’s center at 10:20 a.m. Eastern time.
— At 1:04 p.m. Eastern time, the transit will end.
How can I watch the transit of Mercury?
Remember: Do not look at the sun directly. You will damage your eyes.
With proper solar filters, you can view the event through a telescope or binoculars. Check with the manufacturer of your viewing device to find out what the proper filters are.
You can also use binoculars or a telescope to project an image of Mercury as it skids across the sun. Space.com published a guide for making your own safe viewing device.
If you don’t have your own equipment, contact your local science museum, planetarium or astronomical society, which may be hosting a live viewing party. The Amateur Astronomers Association of New York will be hosting public events in several locations around New York City. In Washington, D.C., the Smithsonian Institution’s Phoebe Waterman Haas Public Observatory will also have a public viewing.
If you can’t get to a place that is showing the transit, tune into a livestream using high-powered telescopes:
— NASA will show the event live.
— NASA’s Solar Dynamics Observatory will show a view from its orbiting telescope.
— The Slooh network of telescopes will show the event from the Canary Islands and other observatories across the world.
— The Griffith Observatory in Los Angeles will also stream it live.
What is the scientific significance of a Mercury transit?
After Gassendi made his sighting in 1631, astronomer Edmund Halley (whom Halley’s comet is named after) saw the Mercury transit in 1677 and formulated the idea that you could use transits of Mercury and Venus to calculate the distance from Earth to the sun, according to NASA.
Since then, scientists have traveled across the world using transits to figure out our place in the solar system.
“The transit of Mercury was one of these gigantic scientific experiments to see if we could get the timing down to make this very important measurement of how far away the sun was,” Faherty said.
Some expeditions to follow transits came at great risk to the astronomers involved. During the 1761 transit of Venus, French astronomer Alexandre Guy Pingré was ambushed by British pirates while traveling to the island of Rodrigues in the Indian Ocean near Mauritius, and then hijacked by the British Royal Navy during his trip home to France.
During Monday’s transit of Mercury, there will be citizen science projects across the world. One, the Citizen Transit of Mercury, will try to calculate the distance to the sun using the transit, according to Skyandtelescope.com.
The transit of Mercury provides amateur astronomers with another scientific bonus.
“It’s a representation of one of the most important techniques that’s currently being applied in astronomy to find worlds around other stars,” Faherty said.
NASA’s Kepler space telescope located more than 2,600 exoplanets during its nearly 10 years in service by searching for celestial transits in front of distant stars. A similar experiment, the TESS satellite that currently orbits Earth, is on the hunt to discover potentially 10,000 more exoplanets using the same technique.
By looking at Mercury as it glides across the sun, you too can become a planet hunter within your own solar system.
This article originally appeared in The New York Times.
© 2019 The New York Times Company