Q43933

NGC 40, also known as the Bow-Tie Nebula or Caldwell 2, is a planetary nebula located around 5280 light years (1619 parsecs) from Earth in the Constellation of Cepheus. The nebula is about one light-year across. It was discovered by William Herschel on November 25, 1788.

The nebula formed due to a dying star ejecting its outer layers of gas leaving behind a small, hot stellar remnant known as a white dwarf. Radiation from the star causes the shed outer layer to heat to about 10,000 degrees Celsius and become visible as a planetary nebula. About 30,000 years from now, scientists theorize that NGC 40 will fade away, leaving only a white dwarf star approximately the size of Earth.