NGC 300
Encyclopedia
NGC 300 is a spiral galaxy
in the constellation
Sculptor
. It is one of the closest galaxies to the Local Group
, and probably lies between us and the Sculptor Group
. It is the brightest of the five main spirals in the direction of the Sculptor Group. It is inclined at an angle of 42° when viewed from earth and shares many characteristics of the Triangulum Galaxy
.
NGC 55
have traditionally been identified as members of the Sculptor Group
, a nearby group of galaxies in the constellation of the same name. However, recent distance measurements indicate that these two galaxies actually lie in the foreground. It is likely that NGC 300 and NGC 55 form a gravitationally bound pair.
estimated the distance to NGC 300 to be 5.41 Mly (1.66 Mpc). By 1992, this had been updated to 6.9 Mly (2.1 Mpc) by Freedman et al. In 2006, this was revised by Karachentsev et al. to be . At about the same time, the tip of the red giant branch (TRGB) method was used to produce an estimate of using edge detection and using maximum likelihood. These results were consistent with estimates using near-infrared photometry of Cepheid variable
s by Gieren et al. 2005 that provided an estimate of . Combining the recent TCGB and Cepheid estimates the distance to NGC 300 is estimated at .
image obtained on May 14, 2008, amateur astronomer L.A.G. Berto Monard discovered an interesting bright optical transient (OT) in NGC 300 that is designated NGC 300-OT. It is located at RA
: and DEC
: in a spiral arm containing active star formation. Its broad-band magnitude was 14.3 in that image. An earlier image (from April 24, 2008), taken just after NGC 300 reemerged from behind the sun, evidenced an already brightening OT at ~16.3 magnitude. No brightening was detected on a February 8, 2008 image or on any earlier ones. The transient's peak measured magnitude was 14.69 on May 15, 2008.
At discovery, the transient had an absolute magnitude of , making it faint in comparison to a typical core-collapse supernova but bright in comparison to a classical nova. Additionally, the photometric and spectroscopic properties of the OT imply that it is not a luminous blue variable
either. Since its peak, brightness dropped smoothly through September 2008 while becoming continuously redder. After September 2008, brightness continued to fall at a lower rate in the optical spectrum but with strong Hα emissions. Further, the optical spectrum is mostly made up of fairly narrow Hydrogen Balmer and Ca II emission lines coupled with strong Ca II H&K absorption. Research into historical Hubble
images provide an accurate upper bound on the progenitor star's brightness. This suggested a low-mass main sequence
star as progenitor with the transient resulting from a stellar merger similar to red Galactic nova V838 Monocerotis
. Analysis of historical images of the area of the OT suggest with 70% certainty that the progenitor formed in a burst of stars around 8–13 Myr ago and implies the progenitor's mass to be 12–25 M⊙
assuming the OT is due to an evolving massive star.
However, in 2008 a bright mid-infrared progenitor to the transient was discovered in historical Spitzer
data. This was a star that was obscured by dust, with energy distribution analogous to a black-body of AU and radiating at K
with . This demonstrated that the transient was associated with an energetic explosion of a low-mass ≈ 10 M⊙
star. The transient's low luminosity as compared to typical core-collapse supernova, combined with its spectral attributes and dust covered properties, make it nearly identical to NGG 6946
's SN 2008S.
The spectrum of NGC 300-OT observed with Spitzer shows strong, broad emission features at 8 μm and 12 μm. Such features are also seen in Galactic carbon-rich
protoplanetary nebulae.
Two sets of independent follow-up spectroscopy data suggested that this was again another optical transient rather than a supernova, possibly an outbursting Luminous Blue Variable
star according to one spectrum, as earlier predicted from the nature of the candidate mid-infrared progenitor. The transient faded by 0.5-0.7 mag in 9 days, much faster than the 2008 transient in NGC 300.
source at the core of NGC 300 is designated NGC 300 X-1. Astronomers speculate that NGC 300 X-1 is a new kind of Wolf-Rayet
black hole
binary system
similar to the confirmed such system IC 10
X-1. Their shared properties include an orbital period
of ~30 hours and x-ray brightness of ~1 erg
s.
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...
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....
Sculptor
Sculptor (constellation)
Sculptor is a small and faint constellation in the southern sky. It represents a sculptor. It was introduced by Nicolas Louis de Lacaille in the 18th century. He originally named it Apparatus Sculptoris , but the name was later shortened.-Notable features:No stars brighter than 3rd magnitude are...
. It is one of the closest galaxies to the Local Group
Local Group
The Local Group is the group of galaxies that includes Earth's galaxy, the Milky Way. The group comprises more than 30 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy...
, and probably lies between us and the Sculptor Group
Sculptor Group
The Sculptor Group is a loose group of galaxies near the south galactic pole. The group is one of the closest groups of galaxies to the Local Group; the distance to the center of the group from the Milky Way is approximately 3.9 Mpc....
. It is the brightest of the five main spirals in the direction of the Sculptor Group. It is inclined at an angle of 42° when viewed from earth and shares many characteristics of the Triangulum Galaxy
Triangulum Galaxy
The Triangulum Galaxy is a spiral galaxy approximately 3 million light years from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC 598, and is sometimes informally referred to as the Pinwheel Galaxy, a nickname it shares with Messier 101...
.
Nearby galaxies and group information
NGC 300 and the irregular galaxyIrregular 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...
NGC 55
NGC 55
NGC 55 is a barred irregular galaxy located about 7 million light-years away in the constellation Sculptor. Along with its neighbor NGC 300, it is one the closest galaxies to the Local Group, probably lying between us and the Sculptor Group.-Nearby galaxies and group information:NGC 55 and the...
have traditionally been identified as members of the Sculptor Group
Sculptor Group
The Sculptor Group is a loose group of galaxies near the south galactic pole. The group is one of the closest groups of galaxies to the Local Group; the distance to the center of the group from the Milky Way is approximately 3.9 Mpc....
, a nearby group of galaxies in the constellation of the same name. However, recent distance measurements indicate that these two galaxies actually lie in the foreground. It is likely that NGC 300 and NGC 55 form a gravitationally bound pair.
Distance estimates
In 1986, Allan SandageAllan Sandage
Allan Rex Sandage was an American astronomer. He was Staff Member Emeritus with the Carnegie Observatories in Pasadena, California. He is best known for determining the first reasonably accurate value for the Hubble constant and the age of the universe.-Career:Sandage was one of the most...
estimated the distance to NGC 300 to be 5.41 Mly (1.66 Mpc). By 1992, this had been updated to 6.9 Mly (2.1 Mpc) by Freedman et al. In 2006, this was revised by Karachentsev et al. to be . At about the same time, the tip of the red giant branch (TRGB) method was used to produce an estimate of using edge detection and using maximum likelihood. These results were consistent with estimates using near-infrared photometry of Cepheid variable
Cepheid variable
A Cepheid is a member of a class of very luminous variable stars. The strong direct relationship between a Cepheid variable's luminosity and pulsation period, secures for Cepheids their status as important standard candles for establishing the Galactic and extragalactic distance scales.Cepheid...
s by Gieren et al. 2005 that provided an estimate of . Combining the recent TCGB and Cepheid estimates the distance to NGC 300 is estimated at .
NGC 300-OT
On a CCDCharge-coupled device
A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...
image obtained on May 14, 2008, amateur astronomer L.A.G. Berto Monard discovered an interesting bright optical transient (OT) in NGC 300 that is designated NGC 300-OT. It is located at RA
Right ascension
Right ascension is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. The other coordinate is the declination.-Explanation:...
: and DEC
Declination
In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Declination in astronomy is comparable to geographic latitude, but projected onto the celestial sphere. Declination is measured in degrees north and...
: in a spiral arm containing active star formation. Its broad-band magnitude was 14.3 in that image. An earlier image (from April 24, 2008), taken just after NGC 300 reemerged from behind the sun, evidenced an already brightening OT at ~16.3 magnitude. No brightening was detected on a February 8, 2008 image or on any earlier ones. The transient's peak measured magnitude was 14.69 on May 15, 2008.
At discovery, the transient had an absolute magnitude of , making it faint in comparison to a typical core-collapse supernova but bright in comparison to a classical nova. Additionally, the photometric and spectroscopic properties of the OT imply that it is not a luminous blue variable
Luminous blue variable
Luminous blue variables, also known as S Doradus variables, are very bright, blue, hypergiant variable stars named after S Doradus, the brightest star of the Large Magellanic Cloud. They exhibit long, slow changes in brightness, punctuated by occasional outbursts in brightness during substantial...
either. Since its peak, brightness dropped smoothly through September 2008 while becoming continuously redder. After September 2008, brightness continued to fall at a lower rate in the optical spectrum but with strong Hα emissions. Further, the optical spectrum is mostly made up of fairly narrow Hydrogen Balmer and Ca II emission lines coupled with strong Ca II H&K absorption. Research into historical Hubble
Hubble 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...
images provide an accurate upper bound on the progenitor star's brightness. This suggested a low-mass main sequence
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...
star as progenitor with the transient resulting from a stellar merger similar to red Galactic nova V838 Monocerotis
V838 Monocerotis
V838 Monocerotis is a red variable star in the constellation Monoceros about 20,000 light years from the Sun, and possibly one of the largest known stars. The previously unknown star was observed in early 2002 experiencing a major outburst. Originally believed to be a typical nova eruption, it...
. Analysis of historical images of the area of the OT suggest with 70% certainty that the progenitor formed in a burst of stars around 8–13 Myr ago and implies the progenitor's mass to be 12–25 M⊙
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
assuming the OT is due to an evolving massive star.
However, in 2008 a bright mid-infrared progenitor to the transient was discovered in historical Spitzer
Spitzer Space Telescope
The Spitzer Space Telescope , formerly the Space Infrared Telescope Facility is an infrared space observatory launched in 2003...
data. This was a star that was obscured by dust, with energy distribution analogous to a black-body of AU and radiating at K
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
with . This demonstrated that the transient was associated with an energetic explosion of a low-mass ≈ 10 M⊙
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
star. The transient's low luminosity as compared to typical core-collapse supernova, combined with its spectral attributes and dust covered properties, make it nearly identical to NGG 6946
NGC 6946
NGC 6946, , is an intermediate spiral galaxy about 22 million light-years away, on the border between the constellations Cepheus and Cygnus. It was discovered by William Herschel on September 9, 1798...
's SN 2008S.
The spectrum of NGC 300-OT observed with Spitzer shows strong, broad emission features at 8 μm and 12 μm. Such features are also seen in Galactic carbon-rich
Carbon star
A carbon star is a late-type star similar to a red giant whose atmosphere contains more carbon than oxygen; the two elements combine in the upper layers of the star, forming carbon monoxide, which consumes all the oxygen in the atmosphere, leaving carbon atoms free to form other carbon compounds,...
protoplanetary nebulae.
SN 2010da
On May 23, 2010, Monard discovered another transient object of 16th magnitude, denoted as SN 2010da. The optical transient was detected 15".9 west and 16".8 north the center of the galaxy at coordinates 00 55 04.86 -37 41 43.7.Two sets of independent follow-up spectroscopy data suggested that this was again another optical transient rather than a supernova, possibly an outbursting Luminous Blue Variable
Luminous blue variable
Luminous blue variables, also known as S Doradus variables, are very bright, blue, hypergiant variable stars named after S Doradus, the brightest star of the Large Magellanic Cloud. They exhibit long, slow changes in brightness, punctuated by occasional outbursts in brightness during substantial...
star according to one spectrum, as earlier predicted from the nature of the candidate mid-infrared progenitor. The transient faded by 0.5-0.7 mag in 9 days, much faster than the 2008 transient in NGC 300.
Binary black hole system
The x-rayX-ray astronomy
X-ray astronomy is an observational branch of astronomy which deals with the study of X-ray observation and detection from astronomical objects. X-radiation is absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets, and...
source at the core of NGC 300 is designated NGC 300 X-1. Astronomers speculate that NGC 300 X-1 is a new kind of Wolf-Rayet
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...
black hole
Black hole
A black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that...
binary system
Binary system (astronomy)
A binary system is an astronomical term referring to two objects in space which are so close that their gravitational interaction causes them to orbit about a common center of mass. Some definitions A binary system is an astronomical term referring to two objects in space (usually stars, but also...
similar to the confirmed such system IC 10
IC 10
IC 10 is an irregular galaxy in the constellation Cassiopeia. It was discovered by Lewis Swift in 1887. Nicholas U. Mayall was the first to suggest that the object is extragalactic in 1935. Edwin Hubble suspected it might belong to the Local Group of galaxies, but its status remained uncertain for...
X-1. Their shared properties include an orbital period
Orbital period
The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of...
of ~30 hours and x-ray brightness of ~1 erg
Erg
An erg is the unit of energy and mechanical work in the centimetre-gram-second system of units, symbol "erg". Its name is derived from the Greek ergon, meaning "work"....
s.
External links
- Confirmation image of SN 2010da (2010-05-24) / Wikisky DSS2 zoom-in of same region
