SN 1994I
Encyclopedia
SN 1994I is a Type Ic supernova
discovered on April 2, 1994 in the Whirlpool Galaxy
by amateur astronomers Tim Puckett and Jerry Armstrong of the Atlanta Astronomy Club
. Type Ic supernova are a rare type of supernova
that result from the explosion of a very massive star that has shed its outer layers of hydrogen
. The explosion results in a highly luminous
burst of radiation that then dims over the course of weeks or months. SN 1994I was a relatively nearby supernova, and provided an important addition to the then small collection of known Type Ic supernova. Very early images were captured of SN 1994I, as two high school students in Oil City
, Pennsylvania
serendipitously took images of the Whirlpool Galaxy using the 30-inch telescope at Leuschner Observatory
on March 31, 1994, which included SN 1994I just after it began to brighten.
, a Type II supernova
, and a Type Ic supernova. Supernova types are observationally distinguished by the presence or absence of spectral line
s, with hydrogen
being the most important diagnostic. After a week of more data being collected, consensus grew among observers that SN 1994I was a Type Ic.
By chance, observations of SN 1994I were obtained before its discovery was reported. High school students Heather Tartara and Melody Spence requested observations of the Whirlpool Galaxy on March 29 and 31, 1994. Their request was made through the Hands-On Universe program, which allows elementary and high school students to request observations on automated telescopes. Their images captured the Whirlpool Galaxy just before and after SN 1994I began to brighten, and are some of the earliest data recorded for a supernova.
to balance the inward force of self-gravity. Yet all Type I supernova are distinguished by their lack of hydrogen absorption lines, and Type Ic also lack the presence of helium
lines. Initial failure to detect hydrogen or helium led to SN 1994I being classified as a Type Ic. Follow-up observations showed very weak helium absorption features, and thus SN 1994I seems to bridge the two classes, though it is still considered one of the best examples of a Type Ic supernova. There are two proposed mechanisms for removing the hydrogen. One suggests that the progenitors of Type Ib and Ic may be Wolf-Rayet star
s, as they produce stellar wind
s that could blow away the hydrogen. The other possibility is mass transfer to a companion star
. The proximity of SN 1994I allowed for detailed comparison of models to the observations. These comparisons showed that SN 1994I was consistent with having lost its outer layers to a companion.
Type Ib and Ic supernovae
Types Ib and Ic supernovae are categories of stellar explosions that are caused by the core collapse of massive stars. These stars have shed their outer envelope of hydrogen, and, when compared to the spectrum of Type Ia supernovae, they lack the absorption line of silicon...
discovered on April 2, 1994 in the Whirlpool Galaxy
Whirlpool Galaxy
The Whirlpool Galaxy is an interacting grand-design spiral galaxy that is estimated to be 23 ± 4 million light-years from the Milky Way Galaxy. in the constellation Canes Venatici...
by amateur astronomers Tim Puckett and Jerry Armstrong of the Atlanta Astronomy Club
Atlanta Astronomy Club
The Atlanta Astronomy Club is one of the largest organizations of beginner and amateur astronomers in the South Eastern United States. The club seeks to provide enjoyment and education to the public through amateur astronomy.-Founding:Dr...
. Type Ic supernova are a rare type of supernova
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...
that result from the explosion of a very massive star that has shed its outer layers of 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...
. The explosion results in a highly luminous
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
burst of radiation that then dims over the course of weeks or months. SN 1994I was a relatively nearby supernova, and provided an important addition to the then small collection of known Type Ic supernova. Very early images were captured of SN 1994I, as two high school students in Oil City
Oil City
Oil City may refer to:in the United States*Casper, Wyoming, nicknamed "The Oil City"* Oil City, California, community in Kern County, California* Oil City, Kentucky, community in Barren County, Kentucky* Oil City, Louisiana, town in Caddo Parish, Louisiana...
, Pennsylvania
Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...
serendipitously took images of the Whirlpool Galaxy using the 30-inch telescope at Leuschner Observatory
Leuschner Observatory
Leuschner Observatory, originally called the Students' Observatory, is an observatory operated by the University of California, Berkeley. The observatory was built in 1886 on the Berkeley campus. For many years, it was directed by Armin Otto Leuschner, for whom the observatory was renamed in 1951...
on March 31, 1994, which included SN 1994I just after it began to brighten.
Discovery and observations
SN 1994I was independently discovered by multiple observers, with the first reports from amateur astronomers Tim Puckett and Jerry Armstrong, followed within the hour by reports by amateurs Wayne Johnson and Doug Miller, Richard Berry, and Reiki Kushida. It was confirmed quickly by Michael Richmond and Alex Filippenko using the Berkeley Automated Imaging Telescope at Leuschner Observatory, who noted that SN 1994I was particularly blue. Initial reports disagreed on the nature of the supernova, with different teams claiming that it was a Type Ia supernovaType 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...
, a Type II 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...
, and a Type Ic supernova. Supernova types are observationally distinguished by the presence or absence of spectral line
Spectral line
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from a deficiency or excess of photons in a narrow frequency range, compared with the nearby frequencies.- Types of line spectra :...
s, with 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...
being the most important diagnostic. After a week of more data being collected, consensus grew among observers that SN 1994I was a Type Ic.
By chance, observations of SN 1994I were obtained before its discovery was reported. High school students Heather Tartara and Melody Spence requested observations of the Whirlpool Galaxy on March 29 and 31, 1994. Their request was made through the Hands-On Universe program, which allows elementary and high school students to request observations on automated telescopes. Their images captured the Whirlpool Galaxy just before and after SN 1994I began to brighten, and are some of the earliest data recorded for a supernova.
Characteristics
The progenitors of Type Ib, Ic, and II supernovae are commonly called core-collapse supernovae, as they result from massive stars that cannot produce enough pressurePressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
to balance the inward force of self-gravity. Yet all Type I supernova are distinguished by their lack of hydrogen absorption lines, and Type Ic also lack the presence of helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
lines. Initial failure to detect hydrogen or helium led to SN 1994I being classified as a Type Ic. Follow-up observations showed very weak helium absorption features, and thus SN 1994I seems to bridge the two classes, though it is still considered one of the best examples of a Type Ic supernova. There are two proposed mechanisms for removing the hydrogen. One suggests that the progenitors of Type Ib and Ic may be Wolf-Rayet star
Wolf-Rayet star
Wolf–Rayet stars are evolved, massive stars , which are losing mass rapidly by means of a very strong stellar wind, with speeds up to 2000 km/s...
s, as they produce stellar wind
Stellar wind
A stellar wind is a flow of neutral or charged gas ejected from the 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 spherically symmetric.Different types of stars have...
s that could blow away the hydrogen. The other possibility is mass transfer to a companion star
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...
. The proximity of SN 1994I allowed for detailed comparison of models to the observations. These comparisons showed that SN 1994I was consistent with having lost its outer layers to a companion.