Astronomical Events Information | 2016 | May
Mars Makes its Closest Approach to Earth
A Chance to Observe Mars! Let’s Use a Telescope!
Mars makes its closest approach to Earth on May 31. At closest approach, the distance between Earth and Mars is 75.28 million kilometers. Mars is the next planet from the Sun after Earth, so it passes the Earth (conjunction), over and over in a cycle of approximately 780 days (roughly 2 years and 2 months). Earth’s orbit is very close to a circle in shape, but Mars’s orbit has a little bit of a squeezed oval shape. Also, because the synodic period (time between conjunctions) is not exactly 2 years, but instead 2 years and 2 months, the place where Earth and Mars pass shifts each time, and the distance at closest approach varies drastically. (The distance during the longest approach is almost twice the distance during the shortest approach.) This closest approach is the shortest since November 20, 2005. The shortest approach of the current series is 57.59 million kilometers in 2018.
The day when Mars is the nearest, called closest approach, gets the most attention. But the distance between Earth and Mars doesn’t change much for several weeks before and after closest approach. Mars is small, with a radius on the order of half of Earth’s radius, so when it is far away the characteristics of its surface can’t be seen very well. But Mars appears large around the time it is closest to Earth, making this is a chance to observe it. Please take this opportunity to observe Mars with a telescope. People who don’t have a telescope might try visiting a public observatory to see Mars with a large telescope.