This
colourful bubble is a planetary nebula called NGC 6818, also known as
the Little Gem Nebula. It is located in the constellation of Sagittarius
(The Archer), roughly 6000 light-years away from us. The rich glow of
the cloud is just over half a light-year across — humongous compared to
its tiny central star — but still a little gem on a cosmic scale. When
stars like the Sun enter retirement, they shed their outer layers into
space to create glowing clouds of gas called planetary nebulae. This
ejection of mass is uneven, and planetary nebulae can have very complex
shapes. NGC 6818 shows knotty filament-like structures and distinct
layers of material, with a bright and enclosed central bubble surrounded
by a larger, more diffuse cloud. Scientists believe that the stellar
wind from the central star propels the outflowing material, sculpting
the elongated shape of NGC 6818. As this fast wind smashes through the
slower-moving cloud it creates particularly bright blowouts at the
bubble’s outer layers. Hubble previously imaged this nebula back in 1997
with its Wide Field Planetary Camera 2, using a mix of filters that
highlighted emission from ionised oxygen and hydrogen (opo9811h). This
image, while from the same camera, uses different filters to reveal a
different view of the nebula. A version of the image was submitted to
the Hubble’s Hidden Treasures image processing competition by contestant
Judy Schmidt.
What's happening in December on Romance - Sweet to
Heat
30 – SPOTLIGHT – Love in the Key of C
31 - Blog Closed for Holidays
