What is the Smallest Star?



What is the Smallest Star?

By Amy Lyons

Have you ever wondered what the smallest star you can see with your own eyes is? How about how small a star can become?

First, let’s begin with a basic definition of a star: a star is an object that has enough mass and pressure within its core that it kindles fusion, the compression of hydrogen atoms into helium. Though less hydrogen is required for smaller stars, hydrogen is still necessary to initiate solar fusion.

Fusion is an exothermic process, meaning that energy is released, so this process produces the energy required to counteract the force of gravity pulling everything inwards towards the center of the star. This is what will result in the size of the star, and what keeps the star from collapsing upon itself.

We use the Sun as a standard for measuring other stars, and the Sun is 1 solar mass, as well as 1 solar luminosity and 1 solar diameter. Using this standard, we can evaluate the comparative size and brightness of other stars.

Even a red dwarf, a star that is only 7.5% of a solar mass, can still fuse hydrogen in its core. An example of a red dwarf is Proxima Centauri, a star approximately 12.3% the mass of the Sun. Although it is the closest star to Earth, Proxima Centauri is too dim to be seen without a telescope.

Unfortunately, there are no red dwarves that can be seen by the naked eye, but the smallest star one may view is 61 Cygni, which is 66% the size of the sun, and only 11.4 light years away. Epsilon Eridani is 74% of the size of the Sun, Alpha Centauri B is 87%, and then there’s the Sun itself, being the 4th smallest star one may see with the naked eye. Among all the smallest stars that we are aware of, the Sun is enormous, though it is still considered a small star.

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