What Is the Difference Between Star and Planet

By Mary Smith. Updated: January 16, 2017
What Is the Difference Between Star and Planet

Do you know the difference between star and planet? Unless you are an expert in astronomy, it's difficult to tell just by looking up at the sky. But the truth is that stars and planets are two types of celestial bodies with very different origins and functions. If you're curious about this topic, then at we will explain what they are and the difference between star and planet.

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What is a star?

A star is a huge collection of plasma and gases united by the law of gravity. It emits a huge amount of energy as light and heat as a result of the thermonuclear fusion occurring at its core.

What is a planet?

A planet is a celestial body that orbits around a star. Planets can be rocky or gaseous or even a combination of the two. A planet also has its own force of gravity that is strong enough to hold it together, but not strong enough to create a thermonuclear reaction. In essence, what distinguishes it from a star is that it does not emit its own light.

How are stars formed?

The stars we see in the sky are millions of light years away. And they are mature enough for us to be able to see them. Stars begin life as a cloud of atoms, such as hydrogen. Over time they become denser until the pressure is such that it causes a nuclear reaction, which creates hydrogen helium. At that moment, the star begins to emit light and, thus, that is how a star is born.

What Is the Difference Between Star and Planet - How are stars formed?

How are planets formed?

Regarding the origin of planets, it is thought that they were formed at the same time as the parent star. As the material becomes bound to the dense core of what will be a star, other small centers of gravity are formed near the orbit of that star. These centers, or proto-planets, will become larger and larger, eventually colliding with each other until the star reaches maturity. After this, a planet takes on its definitive form.

What Is the Difference Between Star and Planet - How are planets formed?

Main differences between stars and planets

  • Stars are huge collections of gas that have a nuclear reactor in their own nucleus. Planets, even large ones, do not have a reactor.
  • Stars are formed first; planets are formed within the orbit of the star as it matures.
  • When the star reaches its maximum density, it begins to shine, something that planets cannot do.
  • If you want to tell the difference at first sight, this means that stars will twinkle in the dark, you will also always find them in the same position, as they don't orbit around the universe and you'll find stars are bigger than planets in the sky.

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