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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.
The nebula is known as S 142 in the 1959 Sharpless catalog (Sh2-142). [2] It is extremely difficult to observe visually, usually requiring very dark skies and an O-III filter. The NGC 7380 complex is located at a distance of approximately 8.5 kilolight-years from the Sun , in the Perseus Arm of the Milky Way .
NGC 6445, also known as the Little Gem Nebula or Box Nebula, is a planetary nebula in the constellation Sagittarius. It was discovered by William Herschel on May 28, 1786. [ 6 ] The distance of NGC 6445 is estimated to be slightly more than 1,000 parsecs based on the parallax measured by Gaia , which was measured at 0.9740 ± 0.3151 mas.
A typical planetary nebula is roughly one light year across, and consists of extremely rarefied gas, with a density generally from 100 to 10,000 particles per cm 3. [40] (The Earth's atmosphere, by comparison, contains 2.5 × 10 19 particles per cm 3.) Young planetary nebulae have the highest densities, sometimes as high as 10 6 particles per ...
The Eagle Nebula (catalogued as Messier 16 or M16, and as NGC 6611, and also known as the Star Queen Nebula) is a young open cluster of stars in the constellation Serpens, discovered by Jean-Philippe de Cheseaux in 1745–46.
The kinematic age of a planetary nebula can be estimated from its expansion speed. According to González-Santamaría and his colleagues, the expansion speed of NGC 2792 is 20 km/s, which gives it a kinematic age of 3.5 thousand years. According to a more recent publication, its expansion speed is 20.2 km/s. [6]
The Crab Nebula (catalogue designations M1, NGC 1952, Taurus A) is a supernova remnant and pulsar wind nebula in the constellation of Taurus.The common name comes from a drawing that somewhat resembled a crab with arms produced by William Parsons, 3rd Earl of Rosse, in 1842 or 1843 using a 36-inch (91 cm) telescope. [6]
NGC 1501 (also known as the Camel's Eye Nebula [3] or the Oyster Nebula [4]) is a complex planetary nebula located in the constellation of Camelopardalis, it was discovered on 27 August 1787 by William Herschel.