SN 2011fe, initially designated PTF 11kly, was a

Type Ia supernova A Type Ia supernova (read: "type one-A") is a type of supernova that occurs in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf. The other star can be anything from a giant star to an even smaller white ...

discovered by the

Palomar Transient Factory The Palomar Transient Factory (PTF, obs. code: I41), was an astronomical survey using a wide-field survey camera designed to search for optical transient and variable sources such as variable stars, supernovae, asteroids and comets. The projec ...

(PTF) survey on 24 August 2011 during an automated review of images of the

Messier 101 #REDIRECT Pinwheel Galaxy The Pinwheel Galaxy (also known as Messier 101, M101 or NGC 5457) is a face-on, counterclockwise intermediate spiral galaxy located from Earth in the constellation Ursa Major. It was discovered by Pierre Méchain in ...

from the nights of 22 and 23 August 2011. It was located in Messier 101, the

Pinwheel Galaxy The Pinwheel Galaxy (also known as Messier 101, M101 or NGC 5457) is a face-on, counterclockwise intermediate spiral galaxy located from Earth in the constellation Ursa Major. It was discovered by Pierre Méchain in 1781 and was communicated ...

, 21 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 from Earth. It was observed by the PTF survey very near the beginning of its supernova event, when it was approximately 1 million times too dim to be visible to the

naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnification, magnifying, Optical telescope#Light-gathering power, light-collecting optical instrument, such as a telescope or microsc ...

. It is the youngest Type Ia ever discovered. About 13 September 2011, it reached its maximum brightness of

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), ...

+9.9 which equals an absolute magnitude of about -19, equal to 2.5 billion Suns. At +10 apparent magnitude around 5 September, SN 2011fe was visible in small telescopes. As of 30 September the supernova was at +11 apparent magnitude in the early evening sky after sunset above the northwest horizon. It had dropped to +13.7 as of 26 November 2011.

Discovery

The Palomar Transient Factory is an automated telescopic survey that scans the sky for transient and variable astronomical events. Information is fed to the

National Energy Research Scientific Computing Center The National Energy Research Scientific Computing Center (NERSC) is a high-performance computing (supercomputer) research facility that was founded in 1974. The National User Facility is operated by Lawrence Berkeley National Laboratory for th ...

(NERSC) at

Lawrence Berkeley National Lab Lawrence Berkeley National Laboratory (LBNL, Berkeley Lab) is a Federally funded research and development centers, federally funded research and development center in the Berkeley Hills, hills of Berkeley, California, United States. Established i ...

, which computes the information to identify new star events. After the initial observation of the SN 2011fe event, telescopes were used in the

Canary Islands The Canary Islands (; ) or Canaries are an archipelago in the Atlantic Ocean and the southernmost Autonomous communities of Spain, Autonomous Community of Spain. They are located in the northwest of Africa, with the closest point to the cont ...

(

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 ...

) to identify the

emission spectrum The emission spectrum of a chemical element or chemical compound is the Spectrum (physical sciences), spectrum of frequencies of electromagnetic radiation emitted due to electrons making a atomic electron transition, transition from a high energ ...

of light emitted at various stages of the event. Following this, 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 ...

, the

Lick Observatory The Lick Observatory is an astronomical observatory owned and operated by the University of California. It is on the summit of Mount Hamilton (California), Mount Hamilton, in the Diablo Range just east of San Jose, California, United States. The ...

in California, and the

Keck Observatory The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes have aperture primary mirrors, and, when c ...

in Hawaii were used to observe the event in greater detail. SN2011feLightCurve

Although SN 2011fe was initially very faint, it brightened rapidly. On the day it was first imaged, 24 August 2011, it was 1 million times too dim to be visible to the unaided eye. One day later, it was 10 thousand times too dim. The next day it was 6 times brighter than that. On 25 August, the

EVLA The Karl G. Jansky Very Large Array (VLA) is a centimeter-wavelength radio astronomy observatory in the southwestern United States built in the 1970s. It lies in central New Mexico on the Plains of San Agustin, between the towns of Magdalena an ...

radio telescope failed to detect radio emissions from SN 2011fe. While such emissions are common for other types of supernovae, they have never been observed for Type Ia's. Two possible candidates were proposed for the precursor system; however, subsequent analysis appears to rule them out.

Importance of Type Ia supernovae and SN 2011fe

Type Ia supernova events occur when a

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 ...

star accretes enough additional matter to exceed the

Chandrasekhar limit The Chandrasekhar limit () is the maximum mass of a stable white dwarf star. The currently accepted value of the Chandrasekhar limit is about (). The limit was named after Subrahmanyan Chandrasekhar. White dwarfs resist gravitational collapse pr ...

and collapses, triggering runaway fusion and a supernova explosion. Because this collapse happens at a consistent mass, the resulting explosions have very uniform characteristics, and are used as "

standard candle The cosmic distance ladder (also known as the extragalactic distance scale) is the succession of methods by which astronomers determine the distances to celestial objects. A ''direct'' distance measurement of an astronomical object is possible ...

s" to measure the distance to their host galaxies. The exact brightness and behavior of a Type Ia supernova depends on the

metallicity In astronomy, metallicity is the Abundance of the chemical elements, abundance of Chemical element, elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non-Dark matter, dark) matt ...

of its parent star (the fraction of the star composed of elements heavier than

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 ...

and

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 ...

before its evolution into a white dwarf). Because the SN 2011fe event was detected so early, astronomers can gain a more accurate measurement of its initial composition and of its evolution during the supernova explosion, and so refine their models of Type Ia supernova events, resulting in more precise distance estimates for other Type Ia supernova observations. Type Ia supernova standard candles may help provide evidence to support the hypothesis of

dark energy In physical cosmology and astronomy, dark energy is a proposed form of energy that affects the universe on the largest scales. Its primary effect is to drive the accelerating expansion of the universe. It also slows the rate of structure format ...

and the accelerating

expansion of the universe The expansion of the universe is the increase in proper length, distance between Gravitational binding energy, gravitationally unbound parts of the observable universe with time. It is an intrinsic and extrinsic properties (philosophy), intrins ...

. A better understanding of Type Ia supernova behavior may in turn allow theoretical models of dark energy to be improved.

References

External links

Nature: Nearby supernova may illuminate dark energy puzzle

Berkeley Scientists Discover an “Instant Cosmic Classic” SupernovaUSA Today: Nearby supernova blooms into viewSupercomputer and superboffins spot rare baby supernovaLight curves and spectra
on th
Open Supernova Catalog

Supernova SN2001fe
{{2011 in space Supernovae 20110824 Ursa Major