Astronomy

Astronomy? Find a galaxy of information here.

Upgrade to Britannica Online

Take a tour, New improved britannica online

Imagine Britannica's 32-volume encyclopedia online right there for you, plus full access to articles. Amazing content, written by world experts, that you can cite for projects and assignments.

Click here for Britannica shop

Vulcan

Hypothetical planet within the orbit of Mercury. It was predicted in 1859 by Urbain-Jean-Joseph Le Verrier (1811–77) to account for an unexplained component of the precession of Mercury's orbit. Sightings were reported between 1859 and 1878, but these were not confirmed subsequently by observations made either during solar eclipses or when the planet was predicted to cross the Sun. The anomalies of Mercury's orbit were later explained by Albert Einstein's general theory of relativity.

Find more information on Vulcan. Upgrade to Britannica Online for more on Vulcan.

  • Britannica, just as colourful as Singapore
  • Singapore is a legendary city. Britannica has a legendary reputation for knowledge. With just a few clicks you can access all the quality information you can trust, online.