NGC 6826

NGC 6826
A Hubble Space Telescope (HST) image of NGC 6826. Credit: HST/NASA/ESA.
Observation data (Epoch J2000)
Right ascension	19h 44m 48.2s[1]
Declination	+50° 31′ 30.3″[1]
Distance	~2000 ly
Apparent magnitude (V)	8.8[2]
Apparent dimensions (V)	27″ × 24″[2]
Constellation	Cygnus
Physical characteristics
Radius	0.22 x 0.20 ly[2]
Other designations	HD 186924, SAO 31951,[1] Caldwell 15
See also: Planetary nebula, Lists of nebulae

NGC 6826 (also known as Caldwell 15) is a planetary nebula located in the constellation Cygnus. It is commonly referred to as the "blinking planetary", although many other nebulae exhibit such "blinking". When viewed through a small telescope, the brightness of the central star overwhelms the eye when viewed directly, obscuring the surrounding nebula. However, it can be viewed well in the peripheral vision (averted vision), which causes it to "blink" in and out of view as the observer's eye wanders.

A distinctive feature of this nebula are the two bright patches on either side, which are known as FLIERs, or Fast Low-Ionization Emission Regions. They appear to be relatively young, moving outwards at supersonic speeds. According to Bruce Balick (University of Washington), "some of their observed characteristics suggest that they are like sparks flung outward from the central star late in the very recent past (a thousand years ago). Yet their shapes ... seem to suggest that they are stationary, and that material ejected from the star flows past them, scraping gas from their surfaces. Future Hubble observations will monitor any changes in the positions of FLIERs to resolve this issue. In either case, the formation of FLIERs cannot be easily explained by any models of stellar evolution."^[3]

See also

• List of NGC objects
• Planetary nebulae

References

1. ^ ^{a b c} "SIMBAD Astronomical Database". Results for NGC 6826. http://simbad.u-strasbg.fr/Simbad. Retrieved 2007-04-17. 
2. ^ ^{a b c} "Stellar Scenes Image Collection". NGC 6826. http://www.ne.jp/asahi/stellar/scenes/object_e/ngc6826.htm. Retrieved 2007-10-05. 
3. ^ "astroimages.org". NGC 6826 : The Blinking Nebula. http://www.astroimages.org/ccd/ngc6826.html. Retrieved 2007-10-05. 

External links

• The Hubble European Space Agency Information Centre Hubble picture and information on NGC 6826
• NGC 6826 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images