My friend and fellow medical retiree, AD Smith, sent me picture of a planetary nebula last week. It seemed vaguely familiar, but there are several thousand in the plane of the Milky Way galaxy, and I’ve only seen a dozen with my instruments, and pictures of only a few dozen more.
Planetary nebulae are so-called because 18th century astronomers thought that they looked like planets rather than stars. Indeed, many of them do appear as disks rather than points of light as do stars. In fact, they are not planets but rather shells of ionized gas ejected from a dying star. Stars like our Sun and perhaps up to 8x heavier eventually exhaust their hydrogen fuel and begin to fuse helium atoms to make elements such as carbon and oxygen. Eventually, they pass through a Red Giant phase and then shrink down into white dwarf stars. You can get the whole story here. It’s pretty interesting and doesn’t require a degree in physics.
The brighter planetary nebulae get fanciful names like The Owl Nebula, The Ring Nebula, The Helix Nebula, The Eye of Sauron, The Eskimo Nebula, and so forth. NGC1501 is a planetary nebula in the constellation Camelopardalis – a large, faint constellation said to represent a giraffe. This nebula is quite faint despite being reasonably close to us at a mere ~5K LY distance. It is sometimes called the Oyster Nebula. Its central star appears to be a binary (two-star) system.
To the Southwest of NGC1501 is NGC1502 – an open cluster some 4K LY from Earth. I captured both objects in a single camera field last night. The images below show the bluish NGC1501 with its somewhat frothy central region, the open cluster NGC1502, and then the entire field showing both NGC1501 and -2. The basic image is the composite of 39, 240-second frames taken with the backyard 5″ astrograph at ISO800.
