SN 1993J is 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 ...

observed in

Bode's Galaxy Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a grand design spiral galaxy about 12 million light-years away in the constellation Ursa Major. It has a D25 isophotal diameter of . Because of its relative proximity to the Milky Way g ...

. It was discovered on 28 March 1993 by amateur astronomer Francisco Garcia Diaz in Lugo,

Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...

. At the time, it was the second-brightest

Type II supernova A Type II supernova or SNII (plural: ''supernovae'') results from the rapid collapse and violent explosion of a massive star. A star must have at least eight times, but no more than 40 to 50 times, the mass of the Sun () to undergo this type ...

observed in the twentieth century behind

SN 1987A SN 1987A was a Type II supernova in the Large Magellanic Cloud, a dwarf satellite galaxy of the Milky Way. It occurred approximately from Earth and was the closest observed supernova since Kepler's Supernova in 1604. Light and neutrinos ...

, peaking at a visible

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

of 10.7 on March 30, with a second peak of 10.86 on April 18. SN1993JLightCurve

The spectral characteristics of the supernova changed over time. Initially, it looked more like a Type II supernova (a supernova formed by the explosion of a giant star) with strong

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 ...

spectral line A spectral line is a weaker or stronger region in an otherwise uniform and continuous spectrum. It may result from emission (electromagnetic radiation), emission or absorption (electromagnetic radiation), absorption of light in a narrow frequency ...

emission, but later the hydrogen lines faded and strong

helium Helium (from ) is a chemical element; it has chemical symbol, symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert gas, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling point is ...

spectral lines appeared, making the supernova look more like a Type Ib. Moreover, the variations in SN 1993J's luminosity over time were not like the variations observed in other Type II supernovae but did resemble the variations observed in Type Ib supernovae. Hence, the supernova has been classified as a

Type IIb supernova A Type II supernova or SNII (plural: ''supernovae'') results from the rapid collapse and violent explosion of a massive star. A star must have at least eight times, but no more than 40 to 50 times, the mass of the Sun () to undergo this type ...

, an intermediate class between Type II and Type Ib. The scientific results from this supernova suggested that Type Ib and Ic supernovae were actually formed through the explosions of giant stars through processes similar to what takes place in Type II supernovae. The supernova was also used to estimate a distance of 8.5 ± 1.3 Mly (2.6 ± 0.4 Mpc) to Bode's Galaxy.

Light echo image:Light Echo Corrected.png, 309x309px, Reflected light following path B arrives shortly after the direct flash following path A but before light following path C. B and C have the same apparent distance from the star as seen from Earth. A ligh ...

es from the explosion have subsequently been detected. The progenitor of SN 1993J was identified in pre-explosion ground-based images. The progenitor was observed to be a K-type supergiant star, with an excess in the

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

possibly due to surrounding hot stars or a hot binary companion. While the supernova is located in a region populated by young massive stars, late-time photometry with the

Hubble Space Telescope The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...

and spectroscopy with the Keck 10m-telescope presented by Maund and collaborators revealed the presence of the long-suspected B-supergiant companion star.

References

External links

Video of artist's impression of the SN 1993J binary progenitor system

Light curves and spectra
on th
Open Supernova Catalog
* {{DEFAULTSORT:SN 1993j Supernovae 19930328 Ursa Major