Get ready for a rare astronomical event: Mercury will transit the Sun on Monday, in a spectacle that only happens around 13 times a century.
The best part? Most of the world, including the United States, will be able to see it. The transit is expected to take around 7.5 hours, starting at approximately 12:12 pm GMT, hitting the midpoint at around 15:45, and coming out on the other side at around 19:42.
Anyone who wants to view our system’s smallest planet will need a telescope or high-powered binoculars outfitted with a solar filter - absolutely never look directly at the sun without a filter. The planet will appear as a small black dot moving across our the sun.
The last time stargazers saw the journey was in 2006. While Mercury’s orbit around the Sun is only 88 days long and it passes between our star and the Earth every 116 days, the event is rare: Due to Mercury’s titled orbit around the sun, we only catch it passing across the sun every couple of years. The next transit will occur in 2019.
While the transit could be a treat for casual viewers, astronomers will be using it to further research into the Sun and Mercury itself. Scientists from the Solar Heliospheric Observatory (SOHO) and the Solar Dynamics Observatory (SDO) will use the event to help calibrate instruments that will be used to study how the Sun changes over time. Since they know exactly where Mercury is going to be, and because it’ll appear as an opaque dot, they can figure out how the equipment should be set up.
“It used to be hard to observe transits,” SOHO Project Scientist Joseph Gurman said in a statement. “If you were in a place that had bad weather, for example, you missed your chance and had to wait for the next one. These instruments help us make our observations, despite any earthly obstacles.”
Scientists will also use the transit to study Mercury’s atmosphere, which is the thinnest in the solar system.