NGC 7662


In Andromeda

From Jim Kaler's STARS; Return to Planetary Nebulae

NGC 7662 NGC 7662
"Exceedingly bright" (Curtis), but small. The bright inner portion of this classic "double shell" planetary nebula in Andromeda (about 4.5 degrees southwest of Lambda Andromedae) averages only 15 seconds of arc across, rendering it difficult to see detail. The outer portion extends to a diameter of some 30 seconds, but it is faint and harder to see. On the left is Curtis's Lick drawing, made from several photographic images. The right hand picture shows the much more detailed Hubble view, though even that is a bit fuzzy (and not very blue). The bright inner ring, expanding at a speed of 30 kilometers per second, seems to have been produced by a hot wind from the central star shovelling the nebular gas in front of it. At an uncertain distance of perhaps 2500 light years (estimated from the angular expansion coupled with expansion velocity of nearly 30 kilometers per second), the outer portion stretches across roughly 0.4 light years, the about half that much. The distance, though, could be half again as great.

The hot, blue 13th magnitude (13.2) central star, with a temperature of 110,000 Kelvin, is still heating at a roughly constant luminosity of 1000 or so times that of the Sun. It will shortly turn the corner and begin to cool and fade as a nascent white dwarf.

Left: Image and quote by H. D. Curtis from Publications of the Lick Observatory, Volume 13, Part III, 1918. Right: Howard Bond (STScI) and NASA/ESA.