Western Slope Skies - The Planet Mercury

Jan 29, 2016

Credit NASA/JPL (Public Domain)

The planet Mercury is the closest planet to our Sun.  Its average distance from the Sun is only 35 million miles. Mercury has the fastest orbital speed in the Solar System…88 days.  Perhaps this is why the planet is named after the speedy messenger to the Roman gods!

Mercury’s rotation is gravitationally locked to the Sun.  Mercury ROTATES 3 times for every 2 times that it ORBITS the Sun.  A “day” on Mercury is about 59 Earth days long.  Think what Mondays would be like there! The long days and the proximity to the Sun means that Mercury’s temperature varies from MINUS 200 degrees F at night to PLUS 800 degrees F during the day. Most of the detailed scientific information about Mercury was collected from 2011 to 2015 by the NASA MESSENGER mission. 

In February, Mercury is visible in the morning shortly before sunrise in the south-east sky.  It may be easier to see in binoculars or a telescope.  For safety reasons, look for the planet ONLY before sunrise. On the morning of February 6, Mercury, Venus and a waning crescent Moon will form a tight group about 3 degrees in radius or about 2 fingers width. If you do get up early to see Mercury and Venus during the first two weeks of February, take advantage of the opportunity to look for Saturn, Jupiter, and Mars, as well.    You will have seen all five of the planets that are visible to the naked eye at the same time - actually – all 6 – if you consider the one below your feet!  Throw in the Moon for good measure. 

A transit of Mercury across the face of the Sun will occur on May 9 from sunrise to about 1 p.m. (MDT).   Observing the transit REQUIRES the use of safe equipment, such as white light or hydrogen-alpha solar filters.  In addition, the small size of Mercury essentially requires the use of telescope.  We hope to have a public outreach event scheduled for the transit.  Listen to Western Slope Skies in late April for details.

Western Slope Skies is produced by members of the Black Canyon Astronomical Society.  This episode was written and recorded by Bryan Cashion.