Mercury Spins around the Sun

Mercury, the smallest and fastest planet in the solar system, has reached the end of its journey across the face of the sun – we won’t see it again until 2019.

Skywatchers across the globe have enjoyed an opportunity to see Mercury transit the Sun.

It was the third such pass of 14 this century; Mercury will not make another transit until 2019 and then 2032.

Social media were abuzz on Monday with images of the unusual spectacle.

The event is impossible – and dangerous – to view with the naked eye or binoculars, but astronomy groups worldwide are offering the chance view it through filtered telescopes.


Mercury spins around the Sun every 88 days, but its orbit is tilted relative to the Earth’s. It is that discrepancy which makes it relatively rare for the three bodies to line up in space.


NASA is offering several avenues for the public to view the event without specialized and costly equipment, including images on, a one-hour NASA Television special, and social media coverage.

Some people were watching the live views from space and ground telescopes online. Mercury appeared as a small black dot as it crosses the edge of the sun and into view at 7:12 a.m. The planet made a leisurely journey across the face of the sun, reaching mid-point at approximately 10:47 a.m., and exiting the golden disk at 2:42 p.m. The entire 7.5-hour path across the sun was visible across the Eastern United States – with magnification and proper solar filters – while those in the West can observe the transit in progress after sunrise.


The entire staff of the Royal Observatory at Greenwich, all the passionate amateur astronomers of the Flamsteed Society, and many anxious members of the public, spent the weekend obsessively refreshing the Met Office weather forecast app – but the threat never changed, the skies over London would have 100% cloud cover, and the best chance of observing the transit of Mercury before 2049 would be lost.

When the Observatory’s many clocks struck noon, and the skies overhead were still an improbable Mediterranean blue, the elation was tangible.

“Every time we have a big event over London, we expect the weather to turn on us,” astronomer Tom Kerss said. High over his head, light too dazzling to look at was pouring through the slot in the dome through which the Great Equatorial Telescope peered, trained on the sun after almost a century of looking at the moon and stars.