The Orion Nebula is a diffuse nebula situated in the Milky Way, being south of Orion's Belt in the constellation of Orion, and is known as the middle "star" in the "sword" of Orion. It is one of the brightest nebulae and is visible to the naked eye in the night sky with apparent magnitude 4.0. It is 1,344 ± 20 light-years (412.1 ± 6.1 pc) away and is the closest region of massive star formation to Earth. The M42 nebula is estimated to be 24 light-years across. It has a mass of about 2,000 times that of the Sun. Older texts frequently refer to the Orion Nebula as the Great Nebula in Orion or the Great Orion Nebula.
The Triangulum Galaxy is a spiral galaxy 2.73 million light-years (ly) from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC (New General Catalogue) 598. With the D25 isophotal diameter of 18.74 kiloparsecs (61,100 light-years), the Triangulum Galaxy is the third-largest member of the Local Group of galaxies, behind the Andromeda Galaxy and the Milky Way.
NGC 2264 is the designation number of the New General Catalogue that identifies two astronomical objects as a single object: the Cone Nebula, and the Christmas Tree Cluster. Two other objects are within this designation but not officially included, the Snowflake Cluster, and the Fox Fur Nebula. All of the objects are located in the Monoceros constellation and are located about 720 parsecs or 2,300 light-years from Earth. Due to its relative proximity and large size, it is extremely well studied. NGC 2264 is sometimes referred to as the Christmas Tree Cluster and the Cone Nebula. However, the designation of NGC 2264 in the New General Catalogue refers to both objects and not the cluster alone. In December 2023, NASA released Christmas holiday-related images by the James Webb Space Telescope, including the Christmas Tree Galaxy Cluster and others.
An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. It is typically in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundreds of light years, and density from a few to about a million particles per cubic centimetre. The Orion Nebula, now known to be an H II region, was observed in 1610 by Nicolas-Claude Fabri de Peiresc by telescope, the first such object discovered.
The Rosette Nebula is an H II region located near one end of a giant molecular cloud in the Monoceros region of the Milky Way Galaxy. The open cluster NGC 2244 is closely associated with the nebulosity, the stars of the cluster having been formed from the nebula's matter.
The Tarantula Nebula is a large H II region in the Large Magellanic Cloud (LMC), forming its south-east corner.
The Pinwheel Galaxy is a face-on spiral galaxy 21 million light-years from Earth in the constellation Ursa Major. It was discovered by Pierre Méchain in 1781 and was communicated that year to Charles Messier, who verified its position for inclusion in the Messier Catalogue as one of its final entries.
The Eagle Nebula is a young open cluster of stars in the constellation Serpens, discovered by Jean-Philippe de Cheseaux in 1745–46. Both the "Eagle" and the "Star Queen" refer to visual impressions of the dark silhouette near the center of the nebula, an area made famous as the "Pillars of Creation" imaged by the Hubble Space Telescope. The nebula contains several active star-forming gas and dust regions, including the aforementioned Pillars of Creation. The Eagle Nebula lies in the Sagittarius Arm of the Milky Way.
The Whirlpool Galaxy, also known as Messier 51a (M51a) or 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. It is 7.22 megaparsecs away and 23.58 kiloparsecs (76,900 ly) in diameter.
The Carina Nebula or Eta Carinae Nebula is a large, complex area of bright and dark nebulosity in the constellation Carina, located in the Carina–Sagittarius Arm of the Milky Way galaxy. The nebula is approximately 8,500 light-years (2,600 pc) from Earth.
Hodge 301 is a star cluster in the Tarantula Nebula, visible from Earth's Southern Hemisphere. The cluster and nebula lie about 168,000 light years away, in one of the Milky Way's orbiting satellite galaxies, the Large Magellanic Cloud.
The Sculptor Galaxy is an intermediate spiral galaxy in the constellation Sculptor. The Sculptor Galaxy is a starburst galaxy, which means that it is currently undergoing a period of intense star formation.
A starburst is an astrophysical process that involves star formation occurring at a rate that is large compared to the rate that is typically observed. This starburst activity will consume the available interstellar gas supply over a timespan that is much shorter than the lifetime of the galaxy. For example, the nebula NGC 6334 has a star formation rate estimated to be 3600 solar masses per million years compared to the star formation rate of the entire Milky Way of about seven million solar masses per million years. Due to the high amount of star formation a starburst is usually accompanied by much higher gas pressure and a larger ratio of hydrogen cyanide to carbon monoxide emission-lines than are usually observed.
NGC 6822 is a barred irregular galaxy approximately 1.5 million light-years away in the constellation Sagittarius. Part of the Local Group of galaxies, it was discovered by E. E. Barnard in 1884, with a six-inch refractor telescope. It is the closest non-satellite galaxy to the Milky Way, but lies just outside its virial radius. It is similar in structure and composition to the Small Magellanic Cloud. It is about 7,000 light-years in diameter.
NGC 1316 is a lenticular galaxy about 60 million light-years away in the constellation Fornax. It is a radio galaxy and at 1400 MHz is the fourth-brightest radio source in the sky.
NGC 2080, also known as the Ghost Head Nebula, is a star-forming region and emission nebula to the south of the 30 Doradus (Tarantula) nebula, in the southern constellation Dorado. It belongs to the Large Magellanic Cloud, a satellite galaxy to the Milky Way, which is at a distance of 168,000 light years. NGC 2080 was discovered by John Frederick William Herschel in 1834. The Ghost Head Nebula has a diameter of 50 light-years and is named for the two distinct white patches it possesses, called the "eyes of the ghost". The western patch, called A1, has a bubble in the center which was created by the young, massive star it contains. The eastern patch, called A2, has several young stars in a newly formed cluster, but they are still obscured by their originating dust cloud. Because neither dust cloud has dissipated due to the stellar radiation, astronomers have deduced that both sets of stars formed within the past 10,000 years. These stars together have begun to create a bubble in the nebula with their outpourings of material, called stellar wind.
The Flame Nebula, designated as NGC 2024 and Sh2-277, is an emission nebula in the constellation Orion. It is about 1350 light-years away. At that distance, the Flame Nebula lies within the Orion B cloud of the larger Orion Molecular Cloud Complex.
NGC 1893 is an open cluster in the constellation Auriga. It is about 12,400 light years away. The star cluster is embedded in the Tadpole Nebula.
NGC 2404 is a massive H II region inside NGC 2403, a spiral galaxy in Camelopardalis. It was discovered on February 2, 1886 by Gulliaume Bigourdan. NGC 2404 is approximately 940 ly in diameter, making it one of the largest H II regions so far known. It is the largest H II region in NGC 2403, and lies at the outskirts of the galaxy, making for a striking similarity with NGC 604 in M33, both in size and location in the host galaxy. This H II region contains 30-40 Wolf-Rayet stars, and unlike the Tarantula Nebula, but similar to NGC 604, NGC 2404's open cluster is probably much less compact, so it probably looks like a large stellar association. This H II region is probably only a few million years old.
