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A protoplanetary nebula or preplanetary nebula [27] (PPN, plural PPNe) is an astronomical object which is at the short-lived episode during a star's rapid evolution between the late asymptotic giant branch (LAGB) phase and the subsequent planetary nebula (PN) phase.
Planetary nebulae, represented here by the Ring Nebula, are examples of emission nebulae. An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. The most common source of ionization is high-energy ultraviolet photons emitted from a nearby hot star .
The nebula measures around two light years long from end to end, and contains a central white dwarf with an apparent magnitude of 11. The inner layers of the nebula were formed some 1,500 years ago. [4] The two ends of the nebula are marked by FLIERs, lobes of fast moving gas often tinted red in false-color pictures. [5]
A 6" telescope with a magnification around 100x will reveal a slightly bluish disk, while telescopes with a primary mirror at least 16" in diameter may reveal slight color and brightness variations in the interior. [4] This nebula has an elliptical shape with a triple-shell structure. The brightest is the main shell, which spans 12″ × 18 ...
This image of the Carina nebula shows only dust, ionized gases, and stars. Here are some puzzles and brainteasers to challenge your family and friends with, either in person or over video chat.
Reflection nebula are usually blue because the scattering is more efficient for blue light than red (this is the same scattering process that gives us blue skies and red sunsets). Reflection nebulae and emission nebulae are often seen together and are sometimes both referred to as diffuse nebulae. Some 500 reflection nebulae are known.
A dark nebula or absorption nebula is a type of interstellar cloud, particularly molecular clouds, that is so dense that it obscures the visible wavelengths of light from objects behind it, such as background stars and emission or reflection nebulae.
IC 5146 (also Caldwell 19, Sh 2-125, Barnard 168, and the Cocoon Nebula) is a reflection [2] /emission [3] nebula and Caldwell object in the constellation Cygnus. The NGC description refers to IC 5146 as a cluster of 9.5 mag stars involved in a bright and dark nebula.