NGC 6826 (also known as
Caldwell
Caldwell may refer to:
People
* Caldwell (surname)
* Caldwell (given name)
* Caldwell First Nation, a federally recognized Indian band in southern Ontario, Canada
Places
Great Britain
* Caldwell, Derbyshire, a hamlet
* Caldwell, East ...
15) is a
planetary nebula
A planetary nebula (PN, plural PNe) is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives.
The term "planetary nebula" is a misnomer because they are unrelated to ...
located in the
constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The origins of the e ...
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 using
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
Fast Low-Ionization Emission Region
A Fast Low-Ionization Emission Region, or FLIER, is a volume of gas with low ionization, moving at supersonic speeds, near the symmetry axis of many planetary nebulae. Their outflow speeds are significantly higher than the nebulae in which they a ...
s, or FLIERS. They appear to be relatively young, moving outwards at supersonic speeds.
The central star of the planetary nebula is an
O-type star
An O-type star is a hot, blue-white star of spectral type O in the Yerkes classification system employed by astronomers. They have temperatures in excess of 30,000 kelvin (K). Stars of this type have strong absorption lines of ionised helium, st ...
with a
spectral type
In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...
of O6fp.
[
]
Gallery
File:NGC_6826_"Blinking_Eye".jpg
See also
* List of NGC objects
The following is a list of NGC objects, that is objects listed in the New General Catalogue (NGC). It is one of the largest comprehensive astronomical catalogues for deep sky objects such as star clusters, nebulae, and galaxies.
* List of NGC objec ...
* Planetary nebulae
A planetary nebula (PN, plural PNe) is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives.
The term "planetary nebula" is a misnomer because they are unrelated ...
References
External links
*
*
{{Cygnus (constellation)
Cygnus (constellation)
Planetary nebulae
6826
015b
015B () is a South Korean music duo that debuted in 1990 and went on to become one of the country's most popular acts of the early 1990s. The group name which means literally "A crow flies across the sky" and it consists of brothers Jeong Seok-won ...