The Ring Nebula is a planetary nebula in the mildly northern constellation of Lyra. Such nebulae are formed by a starburst – ionized gas has expelled into the surrounding interstellar medium by a star to form a vast luminous envelope containing the star in its last stages of its evolution before becoming a white dwarf.
The Trifid Nebula is an H II region in the north-west of Sagittarius in a star-forming region in a nearby spiral arm's Scutum-centered part. It was discovered by Charles Messier on June 5, 1764. Its name means 'three-lobe'. The object is an unusual combination of an open cluster of stars, an emission nebula, a reflection nebula, and a dark nebula. Viewed through a small telescope, the Trifid Nebula is a bright and peculiar object, and is thus a perennial favorite of amateur astronomers.
The Dumbbell Nebula is a planetary nebula in the constellation Vulpecula, at a distance of about 1227 light-years. It was the first such nebula to be discovered, by Charles Messier in 1764. At its brightness of visual magnitude 7.5 and diameter of about 8 arcminutes, it is easily visible in binoculars and is a popular observing target in amateur telescopes.
The Eskimo Nebula, also known as the Clown-faced Nebula, Lion Nebula, or Caldwell 39, is a bipolar double-shell planetary nebula (PN). It was discovered by astronomer William Herschel in 1787. The formation resembles a person's head surrounded by a parka hood. It is surrounded by gas that composed the outer layers of a Sun-like star. The visible inner filaments are ejected by a strong wind of particles from the central star. The outer disk contains unusual, light-year-long filaments.
The Whirlpool Galaxy, also known as Messier 51a, M51a, and NGC 5194, is an interacting grand-design spiral galaxy with a Seyfert 2 active galactic nucleus. It lies in the constellation Canes Venatici, and was the first galaxy to be classified as a spiral galaxy. Its distance is estimated to be 31 million light-years away from Earth.
The Sombrero Galaxy is a spiral galaxy in the constellation borders of Virgo and Corvus, being about 9.55 megaparsecs from our galaxy, within the local supercluster. It has a diameter of approximately 15 kiloparsecs, 30% the size of the Milky Way. It has a bright nucleus, an unusually large central bulge, and a prominent dust lane in its outer disk, which is viewed almost edge-on. The dark dust lane and the bulge give this galaxy the appearance of a sombrero hat. Astronomers initially thought that the halo was small and light, indicative of a spiral galaxy, but the Spitzer Space Telescope found that the dust ring around the Sombrero Galaxy is larger and more massive than previously thought, indicative of a giant elliptical galaxy. The galaxy has an apparent magnitude of +8.0, making it easily visible with amateur telescopes, and it is considered by some authors to be the galaxy with the highest absolute magnitude within a radius of 10 megaparsecs of the Milky Way. Its large bulge, its central supermassive black hole, and its dust lane all attract the attention of professional astronomers.
The Little Dumbbell Nebula, also known as Messier 76, NGC 650/651, the Barbell Nebula, or the Cork Nebula, is a planetary nebula in northern constellation Perseus. It was discovered by Pierre Méchain in 1780 and included in Charles Messier's catalog of comet-like objects as number 76. It was first recognised as a planetary nebula in 1918 by the astronomer Heber Doust Curtis. However, there is some contention to this claim, as Isaac Roberts in 1891 did suggest that M76 might be similar to the Ring Nebula (M57), being instead as seen from the side view. The structure is now classed as a bipolar planetary nebula (BPNe), denoting two stars which have burst, leaving neutron star or white dwarf remnants and luminous envelopes. Distance to M76 is currently estimated as 780 parsecs or 2,500 light years, making the average dimensions about 0.378 pc. across.
The Owl Nebula is a starburst ("planetary") nebula approximately 2,030 light years away in the northern constellation Ursa Major. Its light reaching our neighbourhood is about 8,000 years old. It is approximately circular in cross-section with faint internal structure. It was formed from the outflow of material from the stellar wind of the central star as it evolved along the asymptotic giant branch. The nebula is arranged in three concentric shells/envelopes, with the outermost shell being about 20–30% larger than the inner shell. A mildly owl-like appearance of the nebula is the result of an inner shell that is not circularly symmetric, but instead forms a barrel-like structure aligned at an angle of 45° to the line of sight.
NGC 891 is an edge-on unbarred spiral galaxy about 30 million light-years away in the constellation Andromeda. It was discovered by William Herschel on October 6, 1784. The galaxy is a member of the NGC 1023 group of galaxies in the Local Supercluster. It has an H II nucleus.
NGC 2438 is a planetary nebula in the southern constellation of Puppis. Parallax measurements by Gaia put the central star at a distance of roughly 1,370 light years. It was discovered by William Herschel on March 19, 1786. NGC 2438 appears to lie within the cluster M46, but it is most likely unrelated since it does not share the cluster's radial velocity. The case is yet another example of a superposed pair, joining the famed case of NGC 2818.
NGC 246 is a planetary nebula in the constellation Cetus. The nebula and the stars associated with it are listed in several catalogs, as summarized by the SIMBAD database. It is roughly 1,600 light-years away. The nebula's central star is the 12th magnitude white dwarf HIP 3678.
The Veil Nebula is a cloud of heated and ionized gas and dust in the constellation Cygnus.
The Caldwell catalogue is an astronomical catalogue of 109 star clusters, nebulae, and galaxies for observation by amateur astronomers. The list was compiled by Patrick Moore as a complement to the Messier catalogue.
The Herschel 400 catalogue is a subset of William Herschel's original Catalogue of Nebulae and Clusters of Stars, selected by Brenda F. Guzman (Branchett), Lydel Guzman, Paul Jones, James Morrison, Peggy Taylor and Sara Saey of the Ancient City Astronomy Club in St. Augustine, Florida, United States c. 1980. They decided to generate the list after reading a letter published in Sky & Telescope by James Mullaney of Pittsburgh, Pennsylvania, USA.
NGC 2022 is a planetary nebula in the equatorial constellation of Orion, located at a distance of 8.21 kilolight-years from the Sun. It was first observed by William Herschel on December 28, 1785, who described it as: considerably bright, nearly round, like a star with a large diameter, like an ill-defined planetary nebula. In medium-sized amateur telescopes it looks like small grayish patch of light. It is not very bright but it is still easy to spot it in the eyepiece. The object has the shape of a prolate spheroid with a major to minor axis ratio of 1.2, an apparent size of 28″, and a halo extending out to 40″.
NGC 2867 is an elliptical Type II planetary nebula in the southern constellation of Carina, just over a degree to the NNW of the star Iota Carinae. It was discovered by John Herschel on April 1, 1834. Herschel initially thought he might have found a new planet, but on the following night he checked again and discovered it hadn't moved. The nebula is located at a distance of 7,270 light-years from the Sun.
NGC 3195 is a planetary nebula located in the southern constellation of Chamaeleon. It is the most southern of all the bright sizable planetary nebula in the sky, and remains concealed from all northern observers. Discovered by Sir John Herschel in 1835, this 11.6 apparent magnitude planetary nebula is slightly oval in shape, with dimensions of 40×35 arc seconds, and can be seen visually in telescopic apertures of 10.5 centimetres (4.1 in) at low magnifications.
NGC 3242 is a planetary nebula located in the constellation Hydra.
NGC 6905, also known as the Blue Flash Nebula, is a planetary nebula in the constellation Delphinus. It was discovered by William Herschel in 1784. The central star is 14.0 mag. The distance of the nebula, as with most planetary nebulae, is not well determined and estimates range between 1.7 and 2.6 kpc.
NGC 751 is an elliptical galaxy approximately 225 million light-years away from Earth in the constellation of Triangulum. It forms a close pair of interacting galaxies together with the nearby NGC 750 galaxy. The pair is listed as Arp 166 in the Atlas of Peculiar Galaxies.
