SN 2003fg, nicknamed the Champagne Supernova, was an unusual Type Ia

supernova A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...

. It was discovered on 24 April 2003 with the Canada-France-Hawaii Telescope and the

Keck Telescope The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes have aperture primary mirrors, and, when c ...

, both on

Mauna Kea Mauna Kea (, ; abbreviation for ''Mauna a Wākea''); is a dormant Shield volcano, shield volcano on the Hawaii (island), island of Hawaii. Its peak is above sea level, making it the List of U.S. states by elevation, highest point in Hawaii a ...

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

, and announced by researchers at the

University of Toronto The University of Toronto (UToronto or U of T) is a public university, public research university whose main campus is located on the grounds that surround Queen's Park (Toronto), Queen's Park in Toronto, Ontario, Canada. It was founded by ...

. The supernova occurred in a galaxy some 3.5 billion light-years from Earth. David Branch gave its nickname ''Champagne'' because its discovery could lead to new insights on type Ia supernovae, and is thus cause for celebration. It was unusual because of the mass of its progenitor. According to the current understanding,

white dwarf A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...

stars explode as Type Ia supernovae when their mass approaches 1.4

solar mass The solar mass () is a frequently used unit of mass in astronomy, equal to approximately . It is approximately equal to the mass of the Sun. It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxie ...

es, termed 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 (). The limit was named after Subrahmanyan Chandrasekhar. White dwarfs resist gravitational collapse pr ...

. The mass added to the star is believed to be donated by a companion star, either from the companion's

stellar wind A stellar wind is a flow of gas ejected from the stellar atmosphere, upper atmosphere of a star. It is distinguished from the bipolar outflows characteristic of young stars by being less collimated, although stellar winds are not generally spheri ...

or the overflow of its

Roche lobe In astronomy, the Roche lobe is the region around a star in a binary system within which orbiting material is gravitationally bound to that star. It is an approximately teardrop-shaped region bounded by a critical gravitational equipotential, ...

as it evolves. However, the progenitor of SN 2003fg reached two

es before exploding. The primary mechanism invoked to explain how a white dwarf can exceed the Chandrasekhar mass is unusually rapid

rotation Rotation or rotational/rotary motion is the circular movement of an object around a central line, known as an ''axis of rotation''. A plane figure can rotate in either a clockwise or counterclockwise sense around a perpendicular axis intersect ...

; the added support effectively increases the critical mass. An alternative explanation is that the explosion resulted from the merger of two white dwarfs. The evidence indicating a higher than normal mass comes from the

light curve In astronomy, a light curve is a graph (discrete mathematics), graph of the Radiance, light intensity of a celestial object or region as a function of time, typically with the magnitude (astronomy), magnitude of light received on the ''y''-axis ...

and spectra of the supernova—while it was particularly overluminous, the kinetic energies measured from the spectra appeared smaller than usual. One proposed explanation is that more of the total kinetic energy budget was expended climbing out of the deeper than usual potential well. This is important because the brightness of Type Ia supernovae was thought to be essentially uniform, making them useful "

standard candle The cosmic distance ladder (also known as the extragalactic distance scale) is the succession of methods by which astronomers determine the distances to celestial objects. A ''direct'' distance measurement of an astronomical object is possible ...

s" in measuring distances in the universe. Such an aberrant Type Ia supernova could throw distances and other scientific work into doubt; however, the light curve characteristics of SN 2003fg were such that it would never have been mistaken for an ordinary high-redshift Type Ia supernova.

References

External links

Light curves and spectrum
on th
Open Supernova Catalog
*
'Champagne supernova' challenges understanding of how supernovae work - University of TorontoCosmos Magazine - ''"Rebellious supernova confronts dark energy"'''Champagne Supernova' breaks astronomical rules - CBCAstronomy: Champagne supernova - ''Nature''
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