Seeing the Planets

Venus and the Moon

Venus and the Moon

There are eight major planets in our solar system including Earth; Pluto was demoted to the status of a “dwarf planet” in 2008.  The planets are fascinating sights for stargazers.  With no optics, you can watch the five bright planets Mercury, Venus, Mars, Jupiter, and Saturn move slowly with respect to the background stars from day to day and week to week.  The apparent motion of the planets is caused by their revolution around the Sun, as well as the motion of the Earth with respect to the planets.

The two planets closer to the Sun than Earth, Mercury and Venus, appear bright and fast moving in the sky.  When they are visible, they always lie not far from the Sun before sunrise or after sunset.  The outer planets have a little more freedom to move around the sky.  They can be found anywhere on a narrow band around the sky called the ecliptic which passes through the twelve constellations of the zodiac.  All eight major planets always appear in or very near these constellations.

Saturn as it appears in a small telescope

Saturn as it appears in a small telescope

With your unaided eye, you can see Mercury, Venus, Mars, Jupiter, and Saturn.  If you know just where to look, you might see Uranus too.  Binoculars are not powerful enough to reveal much detail on the face of any planet, though they will reveal the four largest moons of Jupiter that move like clockwork around the planet from hour to hour and night to night (see image below).  Saturn’s largest moon, Titan, is also visible in binoculars and any telescope.  But to see any detail of the face of the planets, or to see the phases of Mercury and Venus, you will need a telescope.

To an observer with a small telescope, Mars, Jupiter, and Saturn reveal an astonishing array of detail on their disks.  On Mars, you can see the white polar caps, darker and lighter orange-red rocky and sandy regions, and even the hint of clouds sometimes.  Jupiter and Saturn in a telescope show bands of icy clouds on their faces and occasional oval “spots” which are local storms larger than the Earth.  Saturn has a stunning system of rings which can be seen even in a small telescope.  These rings are barely more than 10 meters thick and are made of small icy particles.  Uranus and Neptune can be resolved into featureless white disks without detail; it’s an accomplishment for a beginner to see these distant and icy giants at all.  Pluto is too faint to see in all but the largest backyard telescopes.

Jupiter and its 4 largest moons in binoculars

Jupiter and its 4 largest moons in binoculars

 Usually at least one bright planet is visible in the night sky, and sometimes two or three are visible at sometime during the night.  You can get more details on which planets are visible each month at:

http://oneminuteastronomer.com/sky-this-month/

Sky and Telescope magazine also has regular updates on the positions of the planets each month.