SN 2005df was a

Type Ia supernova A Type Ia supernova (read: "type one-A") is a type of supernova that occurs in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf. The other star can be anything from a giant star to an even smaller white ...

in the

barred spiral galaxy A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. Bars are found in about two thirds of all spiral galaxies, and generally affect both the motions of stars and interstellar gas within spiral galaxi ...

NGC 1559 NGC 1559 is a barred spiral galaxy in the constellation Reticulum. It is also a Seyfert galaxy. Although it was originally thought to be a member of the Dorado Group, subsequent observations have shown that it is in fact not a member of any gala ...

, which is located in the southern

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 ...

Reticulum Reticulum is a small, faint constellation in the southern sky. Its name is Latin for a small net, or reticle—a net of crosshairs at the focus of a telescope eyepiece that is used to measure star positions. The constellation is best viewed bet ...

. The event was discovered in Australia by

Robert Evans Robert Evans (born Robert J. Shapera; June 29, 1930October 26, 2019) was an American film producer, studio executive, and actor, best known for his work on '' Rosemary's Baby'' (1968), '' Love Story'' (1970), ''The Godfather'' (1972), and ''Chi ...

on the early morning of August 5, 2005 with a 13.8 magnitude, and was confirmed by A. Gilmore on August 6. The supernova was classified as Type Ia by M. Salvo and associates. It was positioned at an offset of east and north of the galaxy's nucleus, reaching a maximum brightness of 12.3 on August 18. The supernova luminosity appeared unreddened by dust from its host galaxy. The progenitor was a carbon-oxygen

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 ...

close to the

Chandrasekhar limit The Chandrasekhar limit () is the maximum mass of a stable white dwarf star. The currently accepted value of the Chandrasekhar limit is about (). White dwarfs resist gravitational collapse primarily through electron degeneracy pressure, compared ...

, making a merger scenario unlikely. Modelling of the explosion shows a low central density for a hydrogen accretion scenario, suggesting the donating companion was a

helium star A helium star is a class O or B star (blue), which has extraordinarily strong helium lines and weaker than normal hydrogen lines, indicating strong stellar winds and a mass loss of the outer envelope. '' Extreme helium stars'' (EHe) entirely lack ...

or a tidally-disrupted white dwarf. Alternatively, the progenitor may have undergone some form of central mixing.

References

External links

Light curves and spectra
on th
Open Supernova Catalog

{{DEFAULTSORT:SN 2005df Supernovae Reticulum 20050804 2005 in science