Question: How can you tell a planet from a star? Stars twinkle but planets don't, right? Not quite. Twinkling is caused by turbulence in our atmosphere. It tends to affect stars more than planets because stars are further away and have narrower beams of light. But planets can twinkle too especially if they are lower in the sky. So what's a better way to tell a planet from a star?
* Find the ecliptic
The first step is to use location: planets are always found along the ecliptic, an imaginary line in our southern sky that stretches E to W (see above). It marks the plane of the solar system upon which the planets orbit our sun.
Tap the toggle button to see that the ecliptic is high in winter and low in summer. This is due to earth's tilt as it orbits the sun. Notice that the ecliptic goes through a special set of constellations known as the zodiac, or the circle of animals, since many of these constellations are named for animals.
* Look for something out of place
The word planet means to wander. Stars appear fixed in constellations but planets move eastward through the constellations of the zodiac. This motion is too slow to detect in realtime, but it you notice a new 'star' in a constellation where it wasn't before, it's probably a planet.
* Know what you are looking for
It helps to know a thing or two about each planet. This chart lists the planets in order from brightest to dimmest with basic info on how to spot them:
Being blazingly bright, Venus is easy to spot but don't confuse it with Jupiter. And don’t confuse it with the night sky’s brightest star, Sirius, which is far dimmer at magnitude -1.46. To confirm, use a telescope to view its phase.
-2.6
Jupiter is super-bright and easy to spot but don't confuse it with Venus. To confirm, use a binocular to spot its moons or a telescope to view its bands.
-1.7
Mercury is never far from the Sun and can't be viewed at night. It can only be seen when it is far enough from the Sun allowing it to be viewed a little bit above the horizon in twilight right before sunrise or after sunset.
-1.3
Mars is orange-red but don't confuse it with the red stars Aldebaran, Betelgeuse or Antares. Mars varies a lot in brightness based on how far it is from Earth.
+1.1
Saturn looks like a moderately bright pale yellow star. To confirm, use a telescope to view its rings.
+5.7
Although Uranus can be spotted naked-eye, this requires a very dark sky. A binocular or telescope is usually needed.
+7.9
Neptune is so dim that a binocular or telescope is always needed.
* Know when and where to look
The Solar System section of the Star Guide can help you learn when and where on the ecliptic to look for any planet and for any day of the year. Also check out the Sky Map which allows you to explore the planets' locations and movements as you change the time and day. If you notice that a planet is near the Sun in our sky, then you won't be able to view it except, perhaps, right before sunrise or right after sunset.
Finding Planets
