The Crab Nebula 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. The nebula was discovered by English astronomer John Bevis in 1731. It corresponds with a bright supernova recorded by Chinese astronomers in 1054 as a guest star. The nebula was the first astronomical object identified that corresponds with a historically-observed supernova explosion.
The Helix Nebula is a planetary nebula (PN) located in the constellation Aquarius. Discovered by Karl Ludwig Harding, most likely before 1824, this object is one of the closest of all the bright planetary nebulae to Earth. The distance, measured by the Gaia mission, is 655±13 light-years. It is similar in appearance to the Cat's Eye Nebula and the Ring Nebula, whose size, age, and physical characteristics are similar to the Dumbbell Nebula, varying only in its relative proximity and the appearance from the equatorial viewing angle. The Helix Nebula has sometimes been referred to as the "Eye of God" in pop culture, as well as the "Eye of Sauron".
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 Cat's Eye Nebula is a planetary nebula in the northern constellation of Draco, discovered by William Herschel on February 15, 1786. It was the first planetary nebula whose spectrum was investigated by the English amateur astronomer William Huggins, demonstrating that planetary nebulae were gaseous and not stellar in nature. Structurally, the object has had high-resolution images by the Hubble Space Telescope revealing knots, jets, bubbles and complex arcs, being illuminated by the central hot planetary nebula nucleus (PNN). It is a well-studied object that has been observed from radio to X-ray wavelengths. At the centre of the Cat's Eye Nebula is a dying Wolf Rayet star, the sort of which can be seen in the Webb Telescope's image of WR 124. The Cat's Eye Nebula's central star shines at magnitude +11.4. Hubble Space Telescope images show a sort of dart board pattern of concentric rings emanating outwards from the centre.
Cepheus is a constellation in the deep northern sky, named after Cepheus, a king of Aethiopia in Greek mythology. It is one of the 48 constellations listed by the second century astronomer Ptolemy, and it remains one of the 88 constellations in the modern times.
Gamma Cephei is a binary star system approximately 45 light-years away in the northern constellation of Cepheus. The primary is a stellar class K1 orange giant or subgiant star; it has a red dwarf companion. An exoplanet has been confirmed to be orbiting the primary.
Barnard's Loop is an emission nebula in the constellation of Orion. It is part of the Orion molecular cloud complex which also contains the dark Horsehead and bright Orion nebulae. The loop takes the form of a large arc centered approximately on the Orion Nebula. The stars within the Orion Nebula are believed to be responsible for ionizing the loop.
First observed between August 4 and August 6, 1181, Chinese and Japanese astronomers recorded the supernova now known as SN 1181 in eight separate texts. One of only five supernovae in the Milky Way confidently identified in pre-telescopic records, it appeared in the constellation Cassiopeia and was visible and motionless against the fixed stars for 185 days. F. R. Stephenson first recognized that the 1181 AD "guest star" must be a supernova, because such a bright transient that lasts for 185 days and does not move in the sky can only be a galactic supernova.
NGC 7354 is a planetary nebula located in the northern circumpolar constellation of Cepheus, at a distance of approximately 5.5 kly from the Sun. It was discovered by German-born astronomer William Herschel on November 3, 1787. John L. E. Dreyer described it as, "a planetary nebula, bright, small, round, pretty gradually a very little brighter middle".
W Cephei is a spectroscopic binary and variable star located in the constellation Cepheus. It is thought to be a member of the Cep OB1 stellar association at about 8,000 light years. The supergiant primary star is one of the largest known stars and as well as one of the most luminous red supergiants.
The Orion space telescopes were a series of two instruments flown aboard Soviet spacecraft during the 1970s to conduct ultraviolet spectroscopy of stars.
Variable nebulae are reflection nebulae that change in brightness because of changes in their star.
Sh 2-155 is a diffuse nebula in the constellation Cepheus, within a larger nebula complex containing emission, reflection, and dark nebulosity. It is widely known as the Cave Nebula, though that name was applied earlier to Ced 201, a different nebula in Cepheus. Sh 2-155 is an ionized H II region with ongoing star formation activity, at an estimated distance of 725 parsecs from Earth.
Abell 39 is a low surface brightness planetary nebula in the constellation of Hercules. It is the 39th entry in George Abell's 1966 Abell Catalog of Planetary Nebulae of 86 old planetary nebulae which either Abell or Albert George Wilson discovered before August 1955 as part of the National Geographic Society - Palomar Observatory Sky Survey. It is estimated to be about 3,800 light-years from earth and thus 2,600 light-years above the Galactic plane. It is almost perfectly spherical and also one of the largest known spheres with a radius of about 1.4 light-years.
IC 349, also known as Barnard's Merope Nebula, is a nebula which lies 3500 AUs from the star Merope in the Pleiades cluster.
11 Cephei is a single star in the northern constellation of Cepheus, located 184 light years away from the Sun. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.55. The star has a relatively high proper motion, traversing the celestial sphere at the rate of 0.153 arc seconds per annum. It is moving closer to the Earth with a heliocentric radial velocity of −38 km/s.
PV Cephei is a variable star of Orion type located in the constellation of Cepheus at a distance of about 1,100 light-years from Earth. In visible light it varies in brightness from magnitude 17 to 19, making it far too faint to be seen by the naked eye.
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. 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.
Abell 63 is a planetary nebula with an eclipsing binary central star system in the northern constellation of Sagitta. Based on parallax measurements of the central star, it is located at a distance of approximately 8,810 light years from the Sun. The systemic radial velocity of the nebula is +41±2 km/s. The nuclear star system is the progenitor of the nebula and it has a combined apparent visual magnitude of 14.67. During mid eclipse the magnitude drops to 19.24.
HM Sagittae is a dusty-type symbiotic nova in the northern constellation of Sagitta. It was discovered by O. D. Dokuchaeva and colleagues in 1975 when it increased in brightness by six magnitudes. The object displays an emission line spectrum similar to a planetary nebula and was detected in the radio band in 1977. Unlike a classical nova, the optical brightness of this system did not rapidly decrease with time, although it showed some variation. It displays activity in every band of the electromagnetic spectrum from X-ray to radio.
