Difference Between Similar Terms and Objects

Difference between Galaxy and Solar System

the center Galaxy of Cat's Eye

The center Galaxy of Cat's Eye

Galaxy vs Solar System

The solar system and a galaxy are two different terms but sometimes are confused with one another. To understand the solar system, one should know the definition of a star system. A star system is a system in which planets orbit around a massive star. This is due to the gravitational attraction that is present in between them. A solar system is a specific kind of star system in which the Sun is at the centre. The solar system consists of anything that orbits the sun or orbits the planets which orbit the sun. The moon of earth, for example, is a part of our solar system. A galaxy, on the other hand, is a huge collection of stars that are held together by gravitational attraction. There can be a 100 million to over a trillion stars within a galaxy. It consists of interstellar gas, star clusters and numerous star systems. Many star systems can be part of a single galaxy but not the other way around.

Perhaps the biggest difference between a solar system and a galaxy is their size. While the solar system is just a light year across, a galaxy is typically up to 100,000 light years in length. One light year means that it takes light one year to travel this distance. The analogy of the composition of the solar system and a galaxy can be drawn by imagining a gigantic piece of paper with hundreds of millions of dots on it. The solar system would be a single dot on such a paper, where as Milky Way, the galaxy in which the solar system resides, would constitute all the dots on the paper.

Galaxies usually have a massive black hole at its centre. However, there is no black hole present at the centre of the solar system. In fact the solar system cannot accommodate such a massive thing within it.

Galaxies consist of dark matter. Dark matter is basically a type of matter which has gravitational effects that have been detected. The dark matter however cannot be visibly seen because it does not emit any radiation. Contrary to this, no such thing has been identified in our solar system.
In a solar system planets orbit the centre, where as in a galaxy many star systems orbit around the centre of the galaxy. Considering the solar system, the planets orbit the Sun, and the Sun in turn orbits the centre of Milky Way.

Galaxies are categorized according to their shapes and the material which constitutes them. This gives birth to different classifications in which they can be put such as elliptical, spiral or irregular. A solar system however has not been further classified into any such shapes.

Another difference is that the distances between a solar system and another star system is much less than the distance between one galaxy and another galaxy. This is because a galaxy has many stars that are clustered together, the distance between two stars systems from such a cluster will be much less than the distance between the two clusters each having a different centre.


Many solar systems can be part of a galaxy but a galaxy cannot be part of a solar system.
The length of the solar system is many magnitudes smaller than the length of a galaxy.
A solar system contains one star around which planets orbit, where as a galaxy can contain from a 100 million to over a trillion stars.
Solar system consists of a Sun at its centre, where as a galaxy usually has a black hole at its centre.
A galaxy can contain dark matter where as the solar system does not.
In a solar system planets orbit the sun on the other hand, within a galaxy star systems orbit around the centre of the galaxy.
A galaxy can be of different shapes, where as the solar system has a particular shape.
The distance between a solar system and another such system is much less than the distance between two galaxies.

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1 Comment

  1. The word planetary system would more accurately describe a system of planets orbiting around a central star. We are the only planetary that should be called a Solar System because only our star is the Sun (Sol). Additionally, there are planetary systems that are part of a larger star system like Alpha Centauri. In this case, Alpha Centauri is a binary star system (two stars that orbit each other). Each of these main stars can have their own planets, even though they orbit each other. Then there is Proxima Centauri which orbits both Alpha Centauri A and B. Overall I think this is a very helpful article but Solar Systems and Galaxies are best differentiated when you can also include star systems as an in-between example.

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