Resolving mysteries about the first stellar parallaxes and distances

In 1838, Friedrich Wilhelm Bessel won the race to measure the first distance to a star other than our Sun via the trigonometric parallax - setting the first scale of the universe.

Recently, Mark Reid and Karl Menten, who are engaged in parallax measurements at radio wavelengths, revisited Bessel's original publications on "His" star, 61 Cygni, published in the Astronomische Nachrichten.

Out of reverence for Bessel, Reid and Menten decided to publish their findings also in the Astronomische Nachrichten.

Bessel had to make his painstaking measurements over nearly 100 nights at his telescope.

In Bessel's time, astronomers had learned to pay attention to measurement errors and to account for them when deriving results from their data.

Naturally, a scientist of Bessel's caliber was well aware to follow any issues that could possibly affect his observations.

Bessel had a superb instrument at his observatory at Konigsberg in Prussia, which came from the genius instrument maker Joseph Fraunhofer and was the last one he built.

Mark Reid became interested in Bessel's original work and studied his papers on 61 Cygni.

Bessel's papers were first published in German, in the Astronomische Nachrichten, although some excerpts were translated into English and appeared in the Monthly Notices of the Royal Astronomical Society.

"Looking over Bessel's shoulder was a remarkable experience and fun," says Mark Reid.