Caldwell 22
The process begins when, after billions of years of nuclear fusion, the star starts to shut down. Gravity (no longer balanced by the outward pressure created by nuclear fusion) compresses the stellar core. The star’s outer layers of gas puff away into space, creating a planetary nebula (so named because these objects often resemble planetary orbs when viewed through a small telescope). At the center lie the remains of the original star’s compressed core, a small white dwarf. One day the Sun will meet a similar fate, but it has enough fuel to last another 6 billion years or so.
This image was taken using Hubble’s Wide Field and Planetary Camera 2 in 2000. Astronomers compared this image to earlier Hubble images of Caldwell 22 to study how the nebula expanded and changed.
Caldwell 22 was discovered by astronomer William Herschel in 1784. It is located in the constellation Andromeda and has a magnitude of 8.3. The nebula is well placed for observing in autumn night skies from the Northern Hemisphere. In the Southern Hemisphere, look for it low in northern skies in the spring. The nebula can be viewed in telescopes of all sizes, but it might be mistaken for a star at low magnification. Higher magnifications will better distinguish the nebula. A medium-sized telescope shows Caldwell 22 well, but the nebula’s central star will remain hidden from all but the largest telescopes.
Credit: NASA, ESA and A. Hajian (University of Waterloo)
For more information about Hubble’s observations of Caldwell 22, see:
chandra.harvard.edu/photo/2012/pne/
For Hubble's Caldwell catalog site and information on how to find these objects in the night sky, visit:
www.nasa.gov/content/goddard/hubble-s-caldwell-catalogRelevantní obrázky
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NGC 7662NGC 7662 je planetární mlhovina v souhvězdí Andromedy vzdálená od Země přibližně 3 900 světelných let. Objevil ji anglický astronom William Herschel 6. října 1784. Se svou magnitudou 8,3 patří mezi nejjasnější planetární mlhoviny severní oblohy. Na obloze se nachází v západní části souhvězdí asi 2,5° jihozápadně od hvězdy ι And s magnitudou 4,3. .. pokračovat ve čtení