Hubble has rediscovered an old gem recently, imaging a planetary nebula found in the constellation of Sagittarius using a new mix of filters which, by highlighting emissions from ionized oxygen and hydrogen, have given us the most vibrant image to date.
Planetary nebulae such as “Little Gem”, also known as NGC 6818, are formed when smaller stars, such as our Sun, eject their outer layers as they come toward the end of their lives. Since the material is not shed evenly, the resulting luminescent clouds of matter can be found in all sorts of intriguing and complex shapes. Little Gem appears to have knotty, filament-like structures with distinct layers of material.
The nebula is made up of a huge cloud of gas (roughly half a light-year across) that engulfs its “tiny” central star, which can be seen most clearly in an early image of the nebula published in 1918 by H.D. Curtis from the Lick Observatory.
H.D. Curtis/Publications of the Lick Observatory 1918.
Hubble’s Wide Field Planetary Camera 2 has previously imaged the nebula before, but used different filters.
Hubble Wide Field Planetary Camera 2/NASA.
The most recent image by the same camera shows Little Gem in all its glory.
[H/T NASA & The ESA].