T Aurigae (or Nova Aurigae 1891) was a

nova A nova (plural novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", which is Latin for "new") that slowly fades over weeks or months. Causes of the dramati ...

, which lit up in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Auriga AURIGA (''Antenna Ultracriogenica Risonante per l'Indagine Gravitazionale Astronomica'') is an ultracryogenic resonant bar gravitational wave detector in Italy. It is at the Laboratori Nazionali di Legnaro of the Istituto Nazionale di Fisica Nuclea ...

in 1891. Thomas David Anderson, an amateur astronomer in

Edinburgh Edinburgh ( ; gd, Dùn Èideann ) is the capital city of Scotland and one of its 32 Council areas of Scotland, council areas. Historically part of the county of Midlothian (interchangeably Edinburghshire before 1921), it is located in Lothian ...

, 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 (

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

4.74). He mistook the star for

26 Aurigae 26 Aurigae is a binary star system in the northern constellation of Auriga. It is visible to the naked eye as a faint star with an apparent visual magnitude of 5.41. The distance to this system remains poorly constrained. The new Hippar ...

, 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 (the Astronomer Royal of Scotland) 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. TAugLightCurve

Strope and Schaefer report that the peak brightness of T Aurigae was magnitude 4.5,. Pre-discovery images on

photographic plate Photographic plates preceded photographic film as a capture medium in photography, and were still used in some communities up until the late 20th century. The light-sensitive emulsion of silver salts was coated on a glass plate, typically thinn ...

s allowed the a light curve beginning in late 1891 to be constructed. AAVSO data shows that T Aurigae's quiescent magnitude is 15.3. In 1958 observations of the stars forming T Aurigae with the Crossley telescope showed that it is an

eclipsing binary A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in wh ...

, with a period of 4.9 hours, and an eclipse depth of 0.18 magnitudes. T Aurigae was the third nova that was discovered to be a short period eclipsing binary, and that discovery led to increased speculation that the nova phenomenon was connected to close binary star pairs. Today it is believed that all novae are binary stars, with a "donor" star orbiting a

white dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes fro ...

. The stars are so close to each other that matter is transferred from the donor star to the white dwarf.

Nebula

T Aurigae is surrounded by an emission nebula ( shell) which is roughly elliptical (25 arc seconds by 19 arc seconds in size) and resembles a planetary nebula. Its 3-dimensional shape is similar to a prolate ellipsoid, but it has a central waist, making it shaped somewhat like a peanut. Santamaria ''et al.'' obtained images of this shell from 2016 through 2019 and by comparing those images to archival images dating back to 1956, they were able to determine that the shell is expanding at about 0.01 arc seconds per year, corresponding to an expansion velocity of about 350 km/sec.

References

External links

* https://web.archive.org/web/20050912175943/http://www.tsm.toyama.toyama.jp/curators/aroom/var/nova/1600.htm Novae Auriga (constellation) 1892 in science Aurigae, T 036294

1841 Events January–March * January 20 – Charles Elliot of the United Kingdom, and Qishan of the Qing dynasty, agree to the Convention of Chuenpi. * January 26 – Britain occupies Hong Kong. Later in the year, the first census of the i ...

Durchmusterung objects {{var-star-stub