AMHERST, Mass. – On Monday, Nov. 11, the planet Mercury will pass in front of the sun, an event that will not be visible in North America again until 2049, says Stephen Schneider, professor of astronomy at the University of Massachusetts Amherst.
Mercury is so small that a transit can only be seen through a telescope, Schneider points out, but to prevent serious eye damage it is extremely important to view it only using properly designed filters. There is no time during a transit when it is safe to look at the sun directly, and Mercury is too small to be seen through eclipse glasses, he warns.
Weather permitting, UMass astronomers invite the public to the campus’s Sunwheel, where they plan to set up telescopes to safely observe Mercury during its transit progress between 7:36 a.m. to 1:04 p.m., while also explaining what’s happening. During this rare event, the planet will appear as a tiny black dot crossing the face of the sun for several hours.
Mercury orbits the Sun every 88 days, but it is only properly aligned with Earth about a dozen times each century for a transit to be seen, the astronomer says. In addition to the rarity of the alignments making it difficult to witness, one must also be on the daytime side of Earth to see it. The entire 2019 transit is visible from the East Coast of the United States this year, but the next two transits in 2032 and 2039 will occur at night in North America, he adds.
The slight dimming of the light from a star during a transit is of interest to astronomers because it is the method that has been used to detect exoplanets orbiting other stars. Mercury, the planet closest to the sun, is about two-fifths the diameter of Earth. The transit will provide a glimpse of just how large stars are, compared to planets, Schneider explains.
The UMass Amherst Sunwheel is located south of McGuirk Alumni Stadium, just off Rocky Hill Road about one-quarter mile west of University Drive. Visitors to the Sunwheel should be prepared for wet footing.