By Adam England
Mercury – “The Messenger of the Gods” – races around the Sun every 88 days, and was observed by nearly every known ancient culture for being the most mobile object in the sky. It reaches its greatest Western elongation on April 11th, making it most visible and highest above the horizon in the morning sky. It can be spotted low on the Eastern horizon just before sunrise.
Mercury was so named after the Roman deity who was the god of communication and travel, among other things. The very root of the name is thought to stem from the prefix merĝ- meaning border, as he guided souls to the underworld. As viewed from Earth, the planet Mercury never strays far from the horizon, moving along the border of day and night in its quick orbit of the Sun.
The closeness to the sun has proven a double-edged sword to the little planet, stripping away its atmosphere and baking the surface, which is heavily cratered and similar in appearance to the Moon. This indicates little or no tectonic activity for billions of years. The temperatures on the surface range from 800°F in daytime to below -280°F at night.
Being so close to the sun has also made it very difficult to study from Earth or with spacecraft. NASA probes Mariner 10 visited in 1974-75 and MESSENGER collected over 100,000 images from 2011-15. The ESA and JAXA launched BepiColombo in 2018 to continue study of the planet, with planned observations from 2021-28. These include an experiment to verify Einstein’s theory of general relativity with extremely high accuracy like never before.
If you would like to learn more about the sky, telescopes, or socialize with other amateur astronomers, visit us at www.prescottastronomyclub.org or Facebook @PrescottAstronomyClub to find the next star party, Star Talk, or event.
Adam England is a local insurance broker who moonlights as an amateur astronomer, writer, and interplanetary conquest consultant. Follow his rants and exploits on Twitter @AZSalesman or on Facebook @AenglandLM.
IMAGE: Courtesy of NASA MESSENGER mission.