SN 2002bj
Encyclopedia
SN 2002bj was the explosion of a star in the galaxy
NGC 1821, located in the constellation
Lepus
. The explosion was discovered by Jack Newton in scans of images produced by Tim Puckett. (It was independently discovered by the Lick/Tenagra Observatory as part of their combined supernova search program.) Initially it had an apparent magnitude
of about 14.7 and was categorized as a Type IIn supernova
.
However, in 2008 Dovi Poznanski discovered that the spectrum more closely resembled a Type Ia supernova
. Further, the energy output was much lower than a typical supernova and the luminosity dropped at a dramatic
pace.
A team consisting of Poznanski, Joshua Bloom, Alex Filippenko and others concluded that it was a new category of exploding star. This system is believed to consist of a binary pair of white dwarf
stars, with helium being transferred from one dwarf to the other. The accreted helium exploded in a thermonuclear reaction on the surface of the more massive white dwarf, resulting in the observed outburst. In this sense, it was akin to a nova
explosion, although the magnitude of the explosion was a thousand times greater. In 2007, Lars Bildsten et al.. had predicted this category of explosion would occur in AM Canum Venaticorum
-type
binary systems.
NGC 1821 is an irregular galaxy
categorized as type IB(s)m. It is apparent magnitude
14.5 and has a redshift
of 0.012029. This galaxy is located about 48 megaparsecs from the Earth
.
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
NGC 1821, located in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
Lepus
Lepus (constellation)
Lepus is a constellation lying just south of the celestial equator, immediately south of Orion. Its name is Latin for hare. Although the hare does not represent any particular figure in Greek mythology, Lepus was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it...
. The explosion was discovered by Jack Newton in scans of images produced by Tim Puckett. (It was independently discovered by the Lick/Tenagra Observatory as part of their combined supernova search program.) Initially it had an apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
of about 14.7 and was categorized as a Type IIn supernova
Type II supernova
A Type II supernova results from the rapid collapse and violent explosion of a massive star. A star must have at least 9 times, and no more than 40–50 times the mass of the Sun for this type of explosion. It is distinguished from other types of supernova by the presence of hydrogen in its spectrum...
.
However, in 2008 Dovi Poznanski discovered that the spectrum more closely resembled a Type Ia supernova
Type Ia supernova
A Type Ia supernova is a sub-category of supernovae, which in turn are a sub-category of cataclysmic variable stars, that results from the violent explosion of a white dwarf star. A white dwarf is the remnant of a star that has completed its normal life cycle and has ceased nuclear fusion...
. Further, the energy output was much lower than a typical supernova and the luminosity dropped at a dramatic
pace.
A team consisting of Poznanski, Joshua Bloom, Alex Filippenko and others concluded that it was a new category of exploding star. This system is believed to consist of a binary pair of 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...
stars, with helium being transferred from one dwarf to the other. The accreted helium exploded in a thermonuclear reaction on the surface of the more massive white dwarf, resulting in the observed outburst. In this sense, it was akin to a nova
Nova
A nova is a cataclysmic nuclear explosion in a star caused by the accretion of hydrogen on to the surface of a white dwarf star, which ignites and starts nuclear fusion in a runaway manner...
explosion, although the magnitude of the explosion was a thousand times greater. In 2007, Lars Bildsten et al.. had predicted this category of explosion would occur in AM Canum Venaticorum
AM Canum Venaticorum
AM Canum Venaticorum is a cataclysmic variable star in the constellation of Canes Venatici. It is the type star of its class of variables, the AM CVn stars....
-type
binary systems.
NGC 1821 is an irregular galaxy
Irregular galaxy
An irregular galaxy is a galaxy that does not have a distinct regular shape, like a spiral or an elliptical galaxy. The shape of an irregular galaxy is uncommon – they do not fall into any of the regular classes of the Hubble sequence, and they are often chaotic in appearance, with neither a...
categorized as type IB(s)m. It is apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
14.5 and has a 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...
of 0.012029. This galaxy is located about 48 megaparsecs from the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
.