NGC 1309
Encyclopedia
NGC 1309 is a spiral galaxy
located approximately 120 million light-year
s away in the constellation
Eridanus
. It is about 75,000 light-years across; about 3/4s the width of our own galaxy, the Milky Way
. Its shape is classified as SA(s)bc, meaning that it has moderately wound spiral arms and no ring.
Bright blue areas of star formation
can be seen in the spiral arms, while the yellowish central nucleus contains older-population star
s. NGC 1309 is one of over 200 members of the Eridanus Group
of galaxies.
(HST) during August and September 2005 using the B (blue: 435 nm)
, V (visual: 555 nm)
and I (infrared: 814 nm)
filters. The image is a square capturing 2.9 x 2.9 arcminutes of sky (roughly 100,000 light-years per side). Note: the smaller galaxies visible in the image are in the distant background; they are not satellites.
Supernova
SN 2002fk was discovered jointly by Reiki Kushida of the Yatsugatake South Base Observatory, Nagano Prefecture, Japan; and Jun-jie Wang and Yu-Lei Qiu of the Beijing Astronomical Observatory on Sept. 17.719 UT
.
When it was discovered it was magnitude
~15.0; it was estimated to have reached maximum magnitude of ~13.0 before fading away. It was a Type Ia supernova
(i.e., the progenitor star was white dwarf
). White dwarfs are older stars that have used up almost all of their main fuel (the lighter elements such as hydrogen
and helium
). SN 2002fk's spectra
showed no indications of hydrogen, helium or carbon; instead ionized calcium, silicon, iron and nickel were found.
Spiral galaxy
A spiral galaxy is a certain kind of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae and, as such, forms part of the Hubble sequence. Spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as...
located approximately 120 million light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s away 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....
Eridanus
Eridanus (constellation)
Eridanus is a constellation. It is represented as a river; its name is the Ancient Greek name for the Po River. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations. It is the sixth largest of the modern...
. It is about 75,000 light-years across; about 3/4s the width of our own galaxy, the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
. Its shape is classified as SA(s)bc, meaning that it has moderately wound spiral arms and no ring.
Bright blue areas of star formation
H II region
An H II region is a large, low-density cloud of partially ionized gas in which star formation has recently taken place. The short-lived, blue stars forged in these regions emit copious amounts of ultraviolet light, ionizing the surrounding gas...
can be seen in the spiral arms, while the yellowish central nucleus contains older-population star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s. NGC 1309 is one of over 200 members of the Eridanus Group
Eridanus Group
The Eridanus Group, sometimes called the Eridanus Cloud, is a nearby loose grouping of galaxies at a mean distance of approximately 75 Mly in the constellation Eridanus...
of galaxies.
Image
The image on the right is a composite of 25 hours of exposures taken by the Hubble Space TelescopeHubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
(HST) during August and September 2005 using the B (blue: 435 nm)
Photometric system
In astronomy, a Photometric system is a set of well-defined passbands , with a known sensitivity to incident radiation. The sensitivity usually depends on the optical system, detectors and filters used. For each photometric system a set of primary standard stars is provided.The first known...
, V (visual: 555 nm)
Photometric system
In astronomy, a Photometric system is a set of well-defined passbands , with a known sensitivity to incident radiation. The sensitivity usually depends on the optical system, detectors and filters used. For each photometric system a set of primary standard stars is provided.The first known...
and I (infrared: 814 nm)
Photometric system
In astronomy, a Photometric system is a set of well-defined passbands , with a known sensitivity to incident radiation. The sensitivity usually depends on the optical system, detectors and filters used. For each photometric system a set of primary standard stars is provided.The first known...
filters. The image is a square capturing 2.9 x 2.9 arcminutes of sky (roughly 100,000 light-years per side). Note: the smaller galaxies visible in the image are in the distant background; they are not satellites.
SupernovaSupernovaA 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...
2002fk
SN 2002fk was discovered jointly by Reiki Kushida of the Yatsugatake South Base Observatory, Nagano Prefecture, Japan; and Jun-jie Wang and Yu-Lei Qiu of the Beijing Astronomical Observatory on Sept. 17.719 UTUniversal Time
Universal Time is a time scale based on the rotation of the Earth. It is a modern continuation of Greenwich Mean Time , i.e., the mean solar time on the Prime Meridian at Greenwich, and GMT is sometimes used loosely as a synonym for UTC...
.
When it was discovered it was 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...
~15.0; it was estimated to have reached maximum magnitude of ~13.0 before fading away. It was 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...
(i.e., the progenitor star was 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...
). White dwarfs are older stars that have used up almost all of their main fuel (the lighter elements such as 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...
and 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...
). SN 2002fk's spectra
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 :...
showed no indications of hydrogen, helium or carbon; instead ionized calcium, silicon, iron and nickel were found.