Stars vs Planets: How to Tell Them Apart in the Night Sky
Is that bright dot in the sky a star or a planet? Learn the key differences between stars vs planets in the night sky with our helpful guide!
We’ve all looked up at the night sky and marvelled at the sparkling points of light scattered above us, but it can be easy to forget that not all of them are stars! In fact, some of the very brightest “stars” you can see might actually be planets, right here in our Solar System. Spotting planets with the naked eye is easier than you might think – if you know what to look for! In this article, we’ll pit stars vs planets and break down all the key differences, examining why they behave differently in the sky and how you can identify them during your next stargazing session!
What Are Stars?
Stars are massive, luminous spheres of hot plasma held together by gravity. Our Sun is the closest star to Earth and gives us a clue about what stars truly are – gigantic nuclear furnaces burning hydrogen into helium. The stars you see in the night sky are located light-years away from Earth and come in a huge variety of sizes, temperatures, and colours.
They produce their own light through nuclear fusion, which means the light they emit has travelled an enormous distance before reaching your eyes. Because of this, many stars appear to twinkle due to interference from Earth’s atmosphere affecting the faint starlight.
What Are Planets?
Planets, by contrast, are celestial bodies that orbit stars. In our case, that’s the Sun. Unlike stars, planets don’t produce their own light – instead, they reflect sunlight. This is one of the key reasons they look different in the night sky.
Five planets are most commonly visible to the naked eye from Earth: Mercury, Venus, Mars, Jupiter, and Saturn. Quite often, you can easily post most of these objects, just so long as you know when and where to look. Because they’re much closer to us than the stars, they shine more steadily and can appear quite bright from here on Earth.
Stars vs Planets: Key Differences
Both stars and planets appear as points of light in the sky, so how can you tell the difference? Fortunately, when you’re comparing stars vs planets, there are several easy ways to tell them apart:
Twinkling vs Steady Light
One of the most reliable ways to differentiate between stars and planets is how their light behaves. Stars appear to twinkle, especially when they’re close to the horizon. This twinkling, or “scintillation”, is caused by Earth’s turbulent atmosphere bending the star’s light in various directions.
Planets, on the other hand, shine with a steadier, more consistent light. Because they’re so much closer to Earth and present a larger disc in the sky (even if we can’t resolve it with the naked eye), the light from planets is far less affected by atmospheric distortion.
Brightness and Colour
Planets are often among the brightest objects in the night sky, sometimes even outshining stars. Venus, for example, is frequently called the “Evening Star” or “Morning Star” because of its amazingly bright appearance at dawn and dusk. Jupiter and Mars can also appear very bright – in fact, Jupiter may even cast faint shadows, albeit in very dark conditions.
Stars vary in brightness, but generally, they’re dimmer than the planets that are visible to the naked eye. Some stars also show subtle colour differences, including blue, white, yellow, orange, or red, depending on their temperature. Planets also have colour, but it’s usually less vibrant. That said, Mars often appears reddish, while Saturn may show a golden hue through binoculars or a small telescope.
Position and Movement
Stars form fixed patterns in the sky – what we call constellations – that remain relatively unchanged night after night. They move as a group across the sky due to Earth’s rotation, but their relative positions remain stable.
Planets, however, are constantly on the move. The word “planet” comes from the Greek planētēs, meaning “wanderer”, because planets change position relative to the stars. They travel along a path in the sky known as the ecliptic, which means you’ll usually find them in or near the zodiac constellations.
Over days and weeks, you can watch planets shift their positions against the starry background. Occasionally, you might even witness a planetary conjunction, when two planets appear close together in the sky.
Apparent Size and Shape Through a Telescope
If you have access to a telescope, the distinction becomes way clearer. Stars still appear as tiny points of light no matter how much you zoom in – they’re simply too far away. But planets will start to appear as small discs. With a good telescope, you can even spot Jupiter’s moons, Saturn’s rings, and the phases of Venus.
When and Where to See Planets
The best times to see planets vary depending on their orbits and positions relative to Earth. Here are some general tips:
- Venus is often visible near sunrise or sunset. It’s one of the brightest objects in the sky.
- Mars has a reddish tint and is best seen every two years when it’s closest to Earth.
- Jupiter is extremely bright and easy to spot. Look for it high in the sky in the evening.
- Saturn is a bit dimmer but you can find it close to Jupiter when they’re both visible.
- Mercury is tricky, as it stays close to the Sun. It’s best viewed shortly after sunset or before sunrise.
To find out which planets are visible tonight, use an astronomy app like the OSR Star Finder App, which overlays constellations and planets on your phone’s display in real-time.
Observing the Night Sky: Equipment Tips
You don’t need expensive gear to tell stars and planets apart, but a few tools can really elevate your experience:
- Binoculars: Perfect for beginners, binoculars make planets like Jupiter and its moons easier to spot.
- Telescopes: Even a small telescope can reveal details like Saturn’s rings or Mars’ red surface.
- Star Charts: Traditional or digital charts help you learn the layout of the sky.
- Apps and Augmented Reality: Modern stargazing apps let you identify objects in real-time, making learning fun and accessible.
Stars vs Planets: A Closer Connection to the Cosmos
Next time you’re looking up at the night sky, take a closer look: are you seeing a shimmering star or a steady-shining planet? With a little practice, you’ll soon be able to tell the difference. Understanding these heavenly bodies brings us one step closer to understanding the universe. Whether you’re watching a meteor shower, admiring the constellations, or pointing out Saturn’s rings through a telescope, you’re participating in a timeless tradition of cosmic curiosity.
And if you’d like to make that connection even more special, why not name a star for someone you care about? It’s a beautiful way to mark a moment under the stars – and now you’ll know exactly what to look for when you go searching for it!
