Although experts advise against staring directly into the sun, astronomers and space fans will want to find a safe way to do so on May 9, when the solar system's smallest planet, Mercury, will cross the face of the sun in the Mercury transit.
"Astronomers get excited when any two things come close to each other in the heavens," said Louis Mayo, program manager at NASA's Goddard Space Flight Center in Greenbelt, Md., who calls the event a "big deal."
Mercury is a strange, dark world with signs of a history punctuated by volcanic eruptions and tectonic activity. It makes its way around the sun in just 88 days, and its orbit - tilted at about seven degrees with respect to the Earth's - means that it passes directly between us and the sun when its orbital planes intersect with that of our planet's, which is referred to as a transit.
There are only 13 or 14 Mercury transits each century, and typically, you must be at the right location on Earth in order to view it from beginning to end, which is usually several hours. However, the May 9 transit will be visible in its entirety from Europe and most of the Americas.
Unlike Venus, Mercury is far too small to be visible against the sun without magnification, meaning that you're going to need some gear to catch a glimpse of it. Alternatively, you can head to organized transit viewing events, which are being hosting by many astronomy clubs at universities, or check out the European Space Agency (ESA) website for their webstream of live images from space.
The May 9 transit will take place just after 7 a.m. EDT (11 a.m. GMT) and will end just before 3 p.m. EDT (7 p.m. GMT). For those on the west coast, it will begin at sunrise and conclude at approximately 11:30 a.m. PDT (2:30 p.m. EDT; 6:30 p.m. GDT on May 10). Although the exact times listed above will vary a bit, you can expect to see the transit within these time frames.
The last time that a Mercury transit occurred was in 2006, and it won't happen again until 2019, and then after that in 2032, so make sure to catch a glimpse, unless you're willing to wait it out for another chance.
