NASA Time-Lapse Shows Rare Transit of Mercury With 'Unusually Quiet' Sun

NASA has released timelapse footage of the rare transit of Mercury that took place on November 11. Footage taken by the space agency's Solar Dynamics Observatory (SDO) provides "a particularly clear view" of the event, with an "unusually quiet" sun in the background.

The next transit of Mercury—where the planet passes directly between the Earth and our sun—will be 2032. After that, transits will take place in 2039 and 2049.

A video posted by NASA Astronomy Picture of the Day (APOD) showed the planet, which appeared to be a small black dot, moving across the sun from left to right. The video shows five and a half hours of footage condensed down to just 13 seconds.

"Mercury usually passes over or under the sun, as seen from Earth, but last month the Solar System's innermost planet appeared to go just about straight across the middle," the APOD caption said. "Although witnessed by planet admirers across the globe, a particularly clear view was captured by the [SDO] in Earth orbit."

The sun is currently in a "solar minimum"—part of its 11-year cycle where surface activity drops and fewer sunspots appear. The background sun was unusually quiet and showed no sunspots," NASA said.

Because of our position in the solar system, we can only ever see Mercury and Venus transit the sun. Transits of Mercury take place around 13 times per century. Venus transits are much rarer—the last one took place in 2012 and there will not be another until 2117.

According to Lyle Tavernier, an educational technology specialist at NASA's Jet Propulsion Laboratory, studying transits can help scientists find new exoplanets—planets outside our solar system. When a planet passes in front of a star it causes a dip in brightness. If this dip happens at regular intervals, it suggests an object is orbiting it. So far NASA has discovered over 2,700 exoplanets using this technique, Tavernier said, adding the space agency is currently surveying 200,000 more stars in the hope of finding 10,000 more exoplanets.

mercury transit
Transit of Mercury on November 11. The next transit will be in 2032. NASA/Bill Ingalls

Studying transits can also help us better understand the outermost part of the atmospheres of Mercury and Venus—their exospheres. "Some objects, like the Moon and Mercury, were originally thought to have no atmosphere. But scientists have discovered that these bodies are actually surrounded by an ultrathin atmosphere of gases called an exosphere," he wrote. "Scientists want to better understand the composition and density of the gases in Mercury's exosphere, and transits make that possible."