Our solar system has hundreds of moons. Only one is visible to the unaided eyes — our moon. It is easy to see and goes through its phases each month. A few moons are visible in binoculars and more require a telescope. Most of them, however, are so small and far away that they are not visible in amateur astronomer telescopes.

A moon is a celestial body that is orbiting another body besides the sun. If we tour the planets, they have some of the moons. Mercury and Venus have no moons and the Earth has one. Mars has two moons: Phobos and Deimos, both apparently captured asteroids. The giant planets have many more known moons than the inner planets. Jupiter currently has a total of 79 and Saturn leads the parade with 82. Uranus has 27 and Neptune has 14, bringing our total to 205, but there are many more.

Dwarf planets have some moons, too. Pluto has five, Eris has one, Haumea has two. Ceres and Makemake have none. The asteroids may also have moons. Astronomers have found 435 moons that orbit asteroids.

Jupiter’s four Galilean moons, Io, Europa, Ganymede, and Callisto, are visible in good binoculars. You need to use a tripod. Titan, orbiting Saturn, is also easily seen in a modestly sized telescope. A few more are available to folks with a very large telescope.

The Insperity Observatory is again taking reservations for public nights on the first Friday each month. Instructions are on the website: humbleisd.net/observatory.

Aaron Clevenson
Author: Aaron ClevensonEmail: This email address is being protected from spambots. You need JavaScript enabled to view it.
I am the observatory director at the Insperity Observatory in Humble ISD. I am also an adjunct astronomy professor at Lone Star College-Montgomery where I teach solar system astronomy and stars and galaxies astronomy. I am the author of the astronomy textbook, “Astronomy for Mere Mortals.” I am a past president of the North Houston Astronomy Club, and was the chair of Astronomy Day in Southeast Texas in 2015 and 2016. He is an observing program director with The Astronomical League, coordinates their Master Observer Progression Awards, and has authored six of their observing programs.

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