Mercury's last transit was in May of 2016, and the next one is on the morning of Monday, November 11, visible from Santa Barbara.
Prof. Mike Cruise, president of the Royal Astronomical Society said, "This is a rare event, and we'll have to wait 13 years until it happens again.Transits are a visible demonstration of how the planets move around the Sun". During a transit, the interceding body is not sufficiently large to cover whatever it's moving in front of. Plus, find resources for engaging students in this rare celestial event!
Mercury's orbit around the Sun takes 88 days to complete and it passes between the Earth and Sun every 116 days. One team used the transits to indirectly calculate the effect of tidal forces of the Moon on Earth.
After observing the transit of Mercury in 1677, Edmond Halley predicted that transits could be used to accurately measure the distance between the Sun and Earth, which wasn't known at the time. This phenomenon is what makes nearby objects appear to shift more than distant objects when you look out the window of a vehicle, for example.
In 2004 and 2012, Earth was treated to some rather spectacular transits of Venus.
"When Mercury is in front of the Sun, we can study the exosphere close to the planet", said NASA scientist Rosemary Killen.
So far, two NASA space probes have visited Mercury, Mariner 10 in 1974 and 1975, and MESSENGER, which orbited the planet from 2011 until a deliberate crash landing in 2015. That knowledge is valuable to astronomers hoping to use the transit method to spot exoplanets around distant stars. It's important to use a Sun filter from a reputable vendor; you'll also need a telescope that is capable of at least a 50x zoom. Do not look directly at the Sun without a certified solar filter.
The transit of Mercury will be partly or fully visible across much of the globe.
In fact, the only places it can't be seen from are Australia and most of Asia and Alaska, according to NASA's Jet Propulsion Laboratory.
The transit of Mercury on November 11, 2019, begins at 4:35 a.m. PST (7:35 a.m. EST), but it won't be visible to West Coast viewers until after sunrise. A pinprick of darkness will puncture a small hole in the sunlight as the planet traverses the solar disk during a 5.5-hour stretch, starting at 7:35 a.m.
Mercury will cut a diagonal path left to right across the sun on Monday, entering at bottom left (around the 8 hour mark on a clock) and exiting top right (around the 2 hour mark).