SN 2005gj was a

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 ...

located approximately 864 million

light year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distance, astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by t ...

s (265 million

parsec The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (AU), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...

s) away from Earth. It was discovered on September 27, 2005, by the

Sloan Digital Sky Survey The Sloan Digital Sky Survey or SDSS is a major multi-spectral imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project began in 2000 a ...

and the

Nearby Supernova Factory The Nearby Supernova Factory (SNfactory) is a collaborative experiment led by Greg Aldering, designed to collect data on more Type Ia supernovae than have ever been studied in a single project before, and by studying them, to increase understandin ...

. 2005gj was noted because it had qualities of both type Ia and type IIn supernovae, and because

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

emission line A spectral line is a weaker or stronger region in an otherwise uniform and continuous spectrum. It may result from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used ...

s were found in its spectrum (see

hydrogen spectral series The emission spectrum of atomic hydrogen has been divided into a number of ''spectral series'', with wavelengths given by the Rydberg formula. These observed spectral lines are due to the electron making transitions between two energy levels i ...

). These hydrogen lines, which were found on the spectrum at

redshift In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and increase in frequency and e ...

z=0.0613, are thought to be indicative of interactions with a circumstellar medium (CSM; a donut-shaped,

nebula A nebula (; or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral, or molecular hydrogen and also cosmic dust. Nebulae are often star-forming regions, such as in the Pillars of Creation in ...

-like ring of matter around a star) by the supernova's ejected matter or

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 ...

progenitor. Such emission lines are extremely rare in Type Ia supernovae – only one other Type Ia, SN 2002ic, has been observed to exhibit the same properties. However, 2005gj's CSM interaction was much stronger and more clearly observed than 2002ic's. The mass-loss history 2005gj's hydrogen lines suggest has been cited as evidence that luminous blue variable (LBV)

hypergiant A hypergiant ( luminosity class 0 or Ia+) is a very rare type of star that has an extremely high luminosity, mass, size and mass loss because of its extreme stellar winds. The term ''hypergiant'' is defined as luminosity class 0 (zero) in the MK ...

s can be progenitors of thermonuclear supernovae. 2005gj was also noted for its overluminosity. With a

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 ...

that maximised 14–47 days after the initial observation, it was three times more luminous than SN 1991T (which was, at the time of its 1991 discovery, the brightest Ia supernova on record), 1.5 times more luminous than SN 2002ic, and close to 100 times more luminous than previously thought possible. Scientists Denis Leahy and Rachid Ouyed from the

University of Calgary {{Infobox university , name = University of Calgary , image = University of Calgary coat of arms without motto scroll.svg , image_size = 150px , caption = Coat of arms , former ...

contend that the incidence of a quark nova, a very luminous process involving the degeneration of

neutron The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...

s into their constituent

quark A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nucleus, atomic nuclei ...

s, could explain the unusual magnitude of the luminosity.

References

External links

Light curves and spectra
on th
Open Supernova Catalog
{{DEFAULTSORT:SN 2005gj Supernovae Cetus

See also

References

External links