A nova is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star that slowly fades over weeks or months. Causes of the dramatic appearance of a nova vary, depending on the circumstances of the two progenitor stars. All observed novae involve white dwarfs in close binary systems. The main sub-classes of novae are classical novae, recurrent novae (RNe), and dwarf novae. They are all considered to be cataclysmic variable stars.
Eta Cassiopeiae is a binary star system in the northern constellation of Cassiopeia. Its binary nature was first discovered by William Herschel in August 1779. Based upon parallax measurements, the distance to this system is 19.42 light-years from the Sun. The two components are designated Eta Cassiopeiae A and B.
T Aurigae was a nova, which lit up in the constellation Auriga in 1891. Thomas David Anderson, an amateur astronomer in Edinburgh, reported that he was "almost certain" he saw the nova at 02:00 UT on 24 January 1892, when it was slightly brighter than χ Aurigae. He mistook the star for 26 Aurigae, although he noted to himself that it seemed brighter than he remembered it being. He saw it twice more during the following week. On 31 January 1892 he realized his mistake, and wrote a note to Ralph Copeland reporting his discovery. Professor Copeland immediately reported the discovery via telegram to William Huggins, who made the first spectroscopic observations of T Aurigae on 2 February 1892, when the star was a magnitude 4.5 object. T Aurigae was the first nova to be observed spectroscopically.
HR Lyrae or Nova Lyrae 1919 was a nova which occurred in the constellation Lyra in 1919. Its discovery was announced by Johanna C. Mackie on 6 December 1919. She discovered it while examining photographic plates taken at the Harvard College Observatory. The bulletin announcing the discovery states "Between December 4 and 6 it rose rapidly from the sixteenth magnitude or fainter, to a maximum of about 6.5". It was the first nova ever reported in Lyra, and Mackie was awarded the AAVSO gold medal for her discovery. Its peak magnitude of 6.5 implies that it might have been visible to the naked eye, under ideal conditions.
NQ Vulpeculae also known as Nova Vulpeculae 1976, was a nova that appeared in the constellation Vulpecula in 1976. It was discovered visually at 18:20 UT on October 21, 1976 by English amateur astronomer George Alcock. Its apparent magnitude at the time of discovery was 6.5 It reached its maximum brightness of magnitude 6.0 thirteen days after its discovery, at which point it may have been faintly visible to the naked eye. A few days after maximum brightness, it had faded to magnitude 8.3.
V838 Herculis, also known as Nova Herculis 1991, was a nova which occurred in the constellation Hercules in 1991. It was discovered by George Alcock of Yaxley, Cambridgeshire, England at 4:35 UT on the morning of 25 March 1991. He found it with 10×50 binoculars, and on that morning its apparent visual magnitude was 5. Palomar Sky Survey plates showed that before the outburst, the star was at photographic magnitude 20.6 and 18.25.
V1494 Aquilae or Nova Aquilae 1999 b was a nova which occurred during 1999 in the constellation Aquila and reached a brightness of magnitude 3.9 on 2 December 1999. making it easily visible to the naked eye. The nova was discovered with 14×100 binoculars by Alfredo Pereira of Cabo da Roca, Portugal at 18:50 UT on 1 December 1999, when it had a visual magnitude of 6.0.
QU Vulpeculae, also known as Nova Vulpeculae 1984 Number 2, was the second nova which occurred in 1984 in the constellation Vulpecula. It was discovered by Peter Collins, an amateur astronomer from Cardiff, California at 22:08 UT on 22 December 1984. At the time of its discovery, the nova's apparent magnitude was 6.8. By the next night, Collins reported its brightness had increased to magnitude 5.6, making it visible to the naked eye.
Mu Cassiopeiae, Latinized from μ Cassiopeiae, is a binary star system in the constellation Cassiopeia. This system shares the name Marfak with Theta Cassiopeiae, and the name was from Al Marfik or Al Mirfaq (المرفق), meaning "the elbow". It is dimly visible to the naked eye as a point of light with an apparent visual magnitude of 5.16. The system is located at a distance of 25 light years from the Sun based on parallax, and is moving closer with a high radial velocity of −98 km/s. This star will move into the constellation Perseus around 5200 AD.
U Geminorum, in the constellation Gemini, is an archetypal example of a dwarf nova. The binary star system consists of a white dwarf closely orbiting a red dwarf. Every few months it undergoes an outburst that greatly increases its brightness. The dwarf nova class of variable stars are often referred to as U Geminorum variables after this star.
U Scorpii is a recurrent nova system; one of 10 known recurring novae in the Milky Way galaxy. Located near the northern edge of the constellation Scorpius it normally has a magnitude of 18, but reaches a magnitude of about 8 during outbursts. Outbursts have been observed in 1863, 1906, 1936, 1979, 1987, 1999, 2010, and 2022.
V339 Delphini or Nova Delphini 2013 (PNV J20233073+2046041) is a bright nova star in the constellation Delphinus. It was discovered on 14 August 2013 by amateur astronomer Koichi Itagaki in Japan and confirmed by the Liverpool Telescope on La Palma. The nova appeared with a magnitude 6.8 when it was discovered and peaked at magnitude 4.3 on 16 August 2013. A nova is produced by the fusion of accumulated material on the white dwarf nova progenitor acquired from its companion star. The nova system is thus a binary star, and a classical nova. The white dwarf is a carbon-oxygen white dwarf, with an estimated mass of 1.04±0.02 M☉. There is not yet a consensus about what the binay's orbital period is; estimates range from 3.15 hours to 6.43 hours.
KT Eridani was a bright nova in the constellation Eridanus that produced an outburst in 2009. It was the first classical nova ever detected in that constellation. The nova was discovered at 12:52 UT on 25 November 2009 by K. Itagaki at Yamagata, Japan with a 21 cm patrol telescope. At the time of its discovery, it was a magnitude 8.1 object. The discovery occurred after the nova's peak brightness, but the All Sky Automated Survey system had detected the nova on three earlier occasions, allowing a more complete light curve to be produced. The peak magnitude, 5.4, was seen at 15:10 UT on 14 November 2009.
V5856 Sagittarii, also known as Nova Sagittarii 2016 Number 4, was the 4th and brightest nova that occurred in the constellation Sagittarius during 2016. It was discovered by the All Sky Automated Survey for SuperNovae on 25.02 October 2016, at which time it had an apparent visual magnitude of 13.7. It was independently discovered by Yukio Sakurai of Mito, Ibaraki, Japan on 26.38 October 2016, by which time it had reached magnitude 10.4. It reached its peak brightness of magnitude 5.4, making it visible to the naked eye, on 8 November 2016. The nova occurred within a region of the sky monitored by the OGLE microlensing experiment, and that group reported that no star brighter than magnitude 22 was seen at the nova's position prior to its eruption.
V906 Carinae, also known as Nova Carinae 2018, was a nova in the Milky Way galaxy which appeared in the constellation Carina, near the 5th magnitude star HD 92063. It was discovered on images taken on 20.32 March 2018 by the All Sky Automated Survey for SuperNovae (ASAS-SN] telescope at the Cerro Tololo Inter-American Observatory. The ASAS-SN group assigned the name ASASSN-18fv to the object. The discovery image was saturated, allowing researchers to determine only that the object was brighter than apparent magnitude 10. An earlier image obtained by ASAS-SN on 26.32 March 2018 showed the nova was a magnitude ~10.4 object at that time, and the object was not detected on ASAS-SN images taken on 15.34 March 2018 and earlier.
YZ Reticuli, also known as Nova Reticuli 2020 was a naked eye nova in the constellation Reticulum discovered on July 15, 2020. Previously it was known as a VY Sculptoris type object with the designation MGAB-V207.
V705 Cassiopeiae, also known as Nova Cassiopeiae 1993 was a nova which erupted in the constellation Cassiopeia during 1993. The nova was discovered at 11:17 UT on 7 December 1993 by amateur astronomer Kazuyoshi Kanatsu of Matsue, Japan, who photographed it using a 35mm camera with a 55mm f/2.8 lens. Asteroid 6976 Kanatsu was named after him in honor of this discovery. At the time of its discovery the nova had a photographic magnitude of 6.5. Around 18 December 1993 it flared briefly to magnitude 5.3, and then it returned rapidly to magnitude 6.5. It underwent a series of smaller flares until mid February 1993, after which it began a precipitous decline in brightness.
FM Circini, also known as Nova Circini 2018, was a nova which appeared in the constellation Circinus in 2018. It was discovered by John Search of Chatsworth Island, New South Wales, Australia on 19.708 January 2018, using a DSLR with a 50 mm F/1.2 lens. At the time of its discovery, it had an apparent visual magnitude of 9.1. It was confirmed to be a nova spectroscopically on 21 January 2018. FM Circini reached a peak brightness of magnitude 5.8 on 22 March 2018, making it visible to the naked eye.
IW Andromedae is a binary star system in the northern constellation of Andromeda, abbreviated IW And. It is the prototype of a class of variable stars known as IW And variables, which is an anomalous sub-class of the Z Camelopardalis variables. The brightness of this system ranges from an apparent visual magnitude of 13.7 down to 17.3, which requires a telescope to view. The system is located at a distance of approximately 2,860 light years from the Sun based on parallax measurements.
