APOD: 2021 April 28 - North Star: Polaris and Surrounding Dust

Good morning, Rallypoint. Today's Astronomy Picture of the Day (APOD) is titled "North Star: Polaris and Surrounding Dust." In our Northern Hemisphere, finding Polaris is fairly simple. Look for the Big Dipper, and follow the two guide stars in its cup to Polaris. But what is this "intergalactic flux nebula" stuff? That sets us off on a small story.

An early episode of the TV show "Cosmos" flashes back to the 18th century where British astronomer William Herschel was walking on the beach with his son, John. John asks his father if he believes in ghosts. To the boy's surprise, his father says "Yes, I do." When pressed to explain himself further, William Herschel said "Oh no, not the human kind. But look up and you can see a sky full of them."

What Herschel was talking about has become known as the Intergalactic (some say Integrated) Flux Nebula (IFN), or interstellar medium. From 1783 to 1811, Herschel compiled a catalog of 52 regions of the sky where he observed the "floor" brighter than the surrounding areas. Almost a century would pass before Herschel's catalog would be read by Father Johann Hagen, Director of the Vatican Observatory. Father Hagen would eventually claim to have surveyed each of the 52 "nebulosities" identified by Herschel. The scientific community greeted these claims with derision because the features were not photographically detectable.

As you can see, that has changed. No wonder William Herschel believed in ghosts.