The planetary nebula NGC 3242 in Hydra is frequently called the "ghost of Jupiter" because it resembles the disk of Jupiter. It is also sometimes referred to as the Eye Nebula or the "CBS eye."
William Herschel discovered this planetary nebula on February 7, 1785. John Herschel observed it from the Cape of Good Hope, South Africa, in the 1830s, numbered it as h 3248, and included it in the 1864 General Catalogue as GC 2102.
NGC 3242 can be easily observed with amateur telescopes, and appears as a 7.7-magnitude blue-green oval about 16" x 26" in diameter. In larger instruments, the Ghost of Jupiter shows as a bright inner disk embedded in a much larger faint halo, measuring 1250" or about 20.8 arc minutes in diameter. The bright inner nebula is described as looking like an eye by Burnham, and the outer shell gave rise to its popular name, as it is of about the apparent size of Jupiter. The stellar remnant white dwarf visible at the center, cataloged as HD 90255, is of visual magnitude 12.1.
In reality, the Ghost of Jupiter has little to do with Jupiter (or any other planet!) A planetary nebula is created by a star like the Sun, which has completed fusion in its core, and thrown off its outer layers to create a brief but beautiful cosmic display. NGC 3242 is light-years across, and much farther away than the 40-light-minute distance to Jupiter. Astronomers have estimated NGC 3242 to be about 1,400 light-years away, although its distance is not well known; another estimate is some 2,500 light years.