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Planetary nebula Reference Libraries

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Star
2004-10-19 04:45:42

Star -- A star is a self-gravitating sphere of plasma in hydrostatic equilibrium that generates energy in its interior through the process of nuclear fusion. Energy from this process radiates into space as electromagnetic radiation and neutrinos. Star formation and evolution As learned by star formation astronomers, stars are born in molecular clouds, regions of higher density of...

Planetary Nebula
2004-10-19 04:45:42

Planetary Nebula -- A planetary nebula is an astronomical object that usually appears nebulous and disk-like in low-resolution observations. Because of this appearance, similar to the appearance of planets in early observations, the "planetary" adjective was attached and has since been retained for historical consistency. According to current observations and models, planetary nebulae...

Nebula
2004-10-19 04:45:42

Nebula -- in astronomy, observed manifestation of a collection of highly rarefied gas and dust in interstellar space. Prior to the 1960s this term was also applied to bodies later discovered to be galaxies, e.g., the so-called Great Nebula in the constellation Andromeda. In 1864, William Huggins confirmed William Herschel's conclusion that nebulae are not swarms of stars by determining that...

Saturn Nebula
2004-10-19 04:45:40

Saturn Nebula -- The layers of the Saturn Nebula give a complex picture of how this planetary nebula was created. The above picture, taken in April 1996 and released last week, allows a better understanding of the mysterious process that transformed a low-mass star into a white dwarf star. A computer model indicates that the central star of NGC 7009 first expelled the green gas that now...

Ring Nebula
2004-10-19 04:45:40

Ring Nebula -- Discovered by Antoine Darquier de Pellepoix in 1779. The famous ring nebula M57 is often regarded as the prototype of a planetary nebula, and a showpiece in the northern hemisphere summer sky. Recent research has confirmed that it is, most probably, actually a ring (torus) of bright light-emitting material surrounding its central star, and not a spherical (or ellipsoidal)...

Owl Nebula
2004-10-19 04:45:40

Owl Nebula -- Dicovered by Pierre Mchain in 1781. The Owl Nebula M97 is one of the fainter objects in Messier's catalog, discovered by Pierre Mchain on February 16, 1781. In his description of this object, Charles Messier also mentions two other nebulous objects that he (and Mchain) have seen at about the same time, but which he had not added in his printed catalog version of 1781 (in...

Hourglass Nebula
2004-10-19 04:45:40

Hourglass Nebula -- This is an image of MyCn18, a young planetary nebula located about 8,000 light-years away, taken with the Wide Field and Planetary Camera 2 (WFPC2) aboard NASA's Hubble Space Telescope (HST). This Hubble image reveals the true shape of MyCn18 to be an hourglass with an intricate pattern of "etchings" in its walls. This picture has been composed from three separate images...

Dumbbell Nebula
2004-10-19 04:45:40

Dumbbell Nebula -- Discovered by Charles Messier in 1764. The Dumbbell Nebula M27 was the first planetary nebula ever discovered. On July 12, 1764, Charles Messier discovered this new and fascinating class of objects, and describes this one as an oval nebula without stars. We happen to see this one approximately from its equatorial plane (approx. left-to-right in our image); from...

Word of the Day
call-note
  • The call or cry of a bird or other animal to its mate or its young.
'Call-note' is newer than 'bird-call,' which originally referred to 'an instrument for imitating the note of birds' but now also refers to 'the song or cry of a bird.'
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