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How do I distinguish a planet from a star?
Home » Astronomy » Observing the Planets » How do I distinguish a planet from a star?Because a planet will always appear in a constellation of the zodiac, it’s important to learn their stars. Planets don’t really appear to the unaided eye like a star. The light from a star is generated by the star itself—appearing to “twinkle.” The light from a planet looks different —it’s reflected—shining steadily.
Mercury can be difficult because the sky is never really dark when it appears. It’s a dusty reddish color, no brighter than the stars around it. Nothing in the sky—except for the Sun and Moon—outshines Venus! It reflects 68% of the sunlight off its atmosphere and shines with a steady, white light. Mars appears reddish. When far away, it’s small and dim—yet it will be one of the brightest objects in the night as we draw closer.
Jupiter is far brighter than most stars. It will call attention to itself. Saturn is slightly dimmer, glowing with a creamy, yellow light. Uranus is just barely visible unaided—like a tiny, greenish disc no bigger than a star. Neptune is blue and in binoculars it will also look like a small, steady disc. Pluto is a very dim, stellar-sized point and can only be seen with a larger telescope.
A small telescope will show you the phases of both Mercury and Venus, while a pair of binoculars will reveal the dark equatorial bands and four Galilean moons of Jupiter. Bigger binoculars will reveal the ring-shape of Saturn, but even beginners’ telescopes will clearly show its ring system and brighter Moons. The same small telescope will capture Mars as a small red marble when it’s far away; yet reveal dark markings and bright polar caps when it is close. No matter what size telescope or binoculars you use, Uranus and Neptune are so very distant that the best you will ever see is a small, softly colored disc.
Do you think a large telescope would make the planets easier to study? Not necessarily. Seeing details on planets is possible with a small telescope when the conditions are right. Larger aperture only improves resolving power—it can’t change bad seeing. You don’t need a giant telescope to find enough details on our solar system neighbors to keep you interested for the rest of your life!
Take the time to enjoy the planets. Even if you just use your eyes...
Related Observing the Planets Articles
- Observing the Planets - Introduction
- Can I observe the Planets with just my eyes?
- Where do I look for the Planets?
- When should I look for the Planets?
- Why do some planets seem to move differently?
- How do I distinguish a planet from a star?