Which is the Closest Star to the Earth?

When asked this question, astronomers and science teachers give a two part answer. Of course, there is only one star that is closest to the Earth so there is only one correct answer – the Sun. But people who ask this question aren’t considering the Sun as a “star.” They are seeking the closest star to the Earth, among those we see in the night sky.

To the Stars

Aside from the Sun, the star that is closest to the Earth is Alpha Centauri. In the vast reaches of space distances are measured according to how long it would take light to travel, since light moves faster than anything else we know about. Even with that measurement it would take light 4.37 years to travel to Alpha Centauri. In comparison, it would take only eight minutes to travel to the Sun at the speed of light.

To get a better idea about the distances, it might help to know that the Sun is about 93 million miles (approximately 150 million kilometers) from Earth, while the distance to Alpha Centauri would have to be measured in billions of miles. Scientists use kilometers to estimate distances in space and state that Alpha Centauri is 41.5 trillion kilometers from Earth.

Stars and Distance

Now that you know that our Sun is a star and is the closest to Earth, with Alpha Centauri coming in a distant second, you might think that Alpha Centauri would appear as the brightest point of light in the night sky. But this isn’t the case. It may be the closest in distance but it is only number three or four in terms of brightness and visibility. Other stars are a bit farther away from Earth but put out more light than this closer star.

Let’s confuse things a bit more. Alpha Centauri is commonly recognized as the closest single star other than the Sun. But it is actually made up of three separate bodies of light that are very close to each other (in space terms). Using strong telescopes, astronomers have found that Alpha Centauri is composed of parts A and B, and a third piece – Proxima Centauri. The best measurements show that this smaller section of the overall Alpha Centauri mass is 4.22 light years from Earth, making it the closest. Alpha Centauri A and Alpha Centauri B are 4.37 light years away. Since these are the main parts of this star formation scientists use the latter measurement when answering the question – Which star is closest?

Beyond the Alpha Centauri star formation is Barnard’s Star – 5.96 light years. The next nearest is Wolf 359 – 7.78 light years. Some people have heard of the next two in line – Sirius A and Sirius B at 8.58 light years. The “top ten” list of stars closest to the Earth is completed by Luyten-8 A and Luyten-8 B at 8.73 light years, and Ross 154 – 9.68 light years. Most stars are billions of miles away, yet they sometimes seem bright enough to reach out and touch!