SN 2005gj
Encyclopedia
SN 2005gj was a supernova
located approximately 864 million light years (265 million parsec
s) away from Earth. It was discovered on September 29, 2005, by the Sloan Digital Sky Survey
and the Nearby Supernova Factory
. 2005gj was noted because it had qualities of both type Ia and type IIn supernovae, and because hydrogen
emission lines were found in its spectrum (see hydrogen spectral series
). These hydrogen lines, which were found on the spectrum at redshift
z=0.0613, are thought to be indicative of interactions with a circumstellar medium (CSM; a donut-shaped, nebula
-like ring of matter around a star) by the supernova's ejected matter or white dwarf
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, 2005jg'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
s can be progenitors of thermonuclear supernovae.
2005gj was also noted for its overluminosity. With a light curve
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
contend that the incidence of a quark nova, a very luminous process involving the degeneration of neutron
s into their constituent quark
s, could explain the unusual magnitude of the luminosity.
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
located approximately 864 million light years (265 million parsec
Parsec
The parsec is a unit of length used in astronomy. It is about 3.26 light-years, or just under 31 trillion kilometres ....
s) away from Earth. It was discovered on September 29, 2005, by the Sloan Digital Sky Survey
Sloan Digital Sky Survey
The Sloan Digital Sky Survey or SDSS is a major multi-filter 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 was named after the Alfred P...
and the Nearby Supernova Factory
Nearby Supernova Factory
The Nearby Supernova Factory 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 understanding of the expanding universe and "Dark Energy."The project began...
. 2005gj was noted because it had qualities of both type Ia and type IIn supernovae, and because hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
emission lines were found in its spectrum (see hydrogen spectral series
Hydrogen spectral series
The emission spectrum of atomic hydrogen is divided into a number of spectral series, with wavelengths given by the Rydberg formula. These observed spectral lines are due to electrons moving between energy levels in the atom. The spectral series are important in astronomy for detecting the presence...
). These hydrogen lines, which were found on the spectrum at redshift
Redshift
In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum...
z=0.0613, are thought to be indicative of interactions with a circumstellar medium (CSM; a donut-shaped, nebula
Nebula
A nebula is an interstellar cloud of dust, hydrogen gas, helium gas and other ionized gases...
-like ring of matter around a star) by the supernova's ejected matter or white dwarf
White dwarf
A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...
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, 2005jg'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
Luminous blue variable
Luminous blue variables, also known as S Doradus variables, are very bright, blue, hypergiant variable stars named after S Doradus, the brightest star of the Large Magellanic Cloud. They exhibit long, slow changes in brightness, punctuated by occasional outbursts in brightness during substantial...
(LBV) hypergiant
Hypergiant
A hypergiant is a star with a tremendous mass and luminosity, showing signs of a very high rate of mass loss.-Characteristics:...
s can be progenitors of thermonuclear supernovae.
2005gj was also noted for its overluminosity. With a light curve
Light curve
In astronomy, a light curve is a graph of light intensity of a celestial object or region, as a function of time. The light is usually in a particular frequency interval or band...
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
University of Calgary
The University of Calgary is a public research university located in Calgary, Alberta, Canada. Founded in 1966 the U of C is composed of 14 faculties and more than 85 research institutes and centres.More than 25,000 undergraduate and 5,500 graduate students are currently...
contend that the incidence of a quark nova, a very luminous process involving the degeneration of neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
s into their constituent quark
Quark
A quark is an 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 nuclei. Due to a phenomenon known as color confinement, quarks are never directly...
s, could explain the unusual magnitude of the luminosity.