Answer: Friedrich Bessel

Friedrich Bessel was born in the late 18th century in Germany, the son of a civil servant and one of many children in a large family. As a boy, he was apprenticed to the import-export firm of Andreas Kulenkamp and Sons where he quickly earned a name for himself as a bit of a mathematical prodigy. There he helped keep the books and focused heavily on navigation since the movement of ships was key to the success of the business. He soon found himself studying astronomy as a method for determining longitude to help plot courses for the ships.

It should come as no surprise then, given his avid and early interest in both mathematics and navigation using the stars, that Bessel would not only go on to be a well-esteemed mathematician and astronomer (as well as a physicist and geodesist), but that he would be the first person to measure a significant astronomical distance with a high level of accuracy: the distance between two stars.

Specifically, Bessel is credited with being the first astronomer to effectively and accurately measure the distance between two stars by means of parallax. In 1838, he measured the distance from Earth’s sun to the star 61 Cygni at 10.3 light years. Today, with more refined measurements, we now know the distance to be 11.4 light years—but despite the 9.6 percent error in the calculation, the methodology and accuracy were unheard of at the time.