Three planets are visible in the current evening sky: Venus, Mars, and Saturn.
But how do you tell a planet from a star?
1) By how it looks.
Whereas stars twinkle, planets generally shine more steadily. Planets can also look very bright—especially Venus. Currently in the western evening sky, it’s the brightest object other than the Moon. Also in the evening sky are Mars and Saturn, which are roughly as bright as the brightest stars appearing near them.
2) By where it is.
Stars appear all over the sky, but you won’t find planets just anywhere. Because they orbit the Sun in roughly the same plane, planets always appear within a certain band in our sky—the zodiac. Right now Venus appears to be near the feet of the Gemini Twins, Mars is about to munched on by Leo the Lion, and Saturn looks like Virgo the Maiden’s earring. (Side note: Many people are familiar with the 12 astrological signs of the zodiac, but there are more than 12 astronomical constellations of the zodiac that planets can appear in. Mercury, for example, was recently hanging out inside the boundary of Cetus the Sea Monster.)
3) By how it moves over time.
Watch a planet night after night, and eventually you’ll notice it appears to wander against the background of the stars. Learn to identify the zodiacal constellations, and then you’ll know that any “extra” star is probably a planet. For an animation of the changing positions of the planets over the next few weeks, view the May 15th Carolina Skies segment on WRAL.
Over the next few months Venus, Mars, and Saturn will appear to close in on one another. See their progress at Morehead Planetarium and Science Center’s next skywatching session on Saturday, June 19. Weather permitting, we’ll be at Jordan Lake’s Ebenezer Church Recreation Area from 9 to 11 p.m.
Amy Sayle is Morehead's Science 360 manager.