| NGC 300 | |
|---|---|
 NGC 300 imaged by ESO'sLa Silla Observatory | |
| Observation data (J2000epoch) | |
| Constellation | Sculptor |
| Right ascension | 00h 54m 53.48s[1] |
| Declination | −37° 41′ 03.8″[1] |
| Redshift | 0.000480[1] |
| Heliocentric radial velocity | 144 ± 1 km/s[1] |
| Distance | 6.07 ± 0.23Mly (1.86 ± 0.07Mpc)[2][a] |
| Apparent magnitude (V) | 9.0[1] |
| Characteristics | |
| Type | SA(s)d[1] |
| Mass | (2.9 ± 0.2) × 1010 M☉ |
| Size | 55,200ly (16.92kpc) (estimated)[1] |
| Apparent size (V) | 21.9′ × 15.5′[1] |
| Other designations | |
| ESO 295- G 020,IRAS 00525-3757,2MASX J00545347-3741037,MCG -06-03-005,PGC 3238,Caldwell 70[1] | |
NGC 300 (also known asCaldwell 70 or theSculptor Pinwheel Galaxy[3]) is aspiral galaxy in theconstellationSculptor. It was discovered on 5 August 1826 byScottish astronomerJames Dunlop.[4] It is one of the closest galaxies to theLocal Group, and it most likely lies between the latter and theSculptor Group. It is the brightest of the five main spirals in the direction of the Sculptor Group.[2] It is inclined at an angle of 42° when viewed fromEarth and shares many characteristics of theTriangulum Galaxy.[5] It is about 94,000 light-years in diameter, somewhat smaller than theMilky Way, and has an estimated mass of (2.9 ± 0.2) × 1010M☉.[6][7]
NGC 300 and theMagellanic typebarred spiral galaxyNGC 55 have traditionally been identified as members of theSculptor Group, a nearbygroup of galaxies in the constellation of the same name. However, recent distance measurements indicate that these two galaxies actually lie in the foreground.[8] It is likely that NGC 300 and NGC 55 form a gravitationally bound pair.[9]
The dwarf galaxySculptor C is located about 6.65 million light-years (2.04megaparsecs) away from the Sun, and is very likely asatellite galaxy of NGC 300. Sculptor C has an absolute magnitude of about −9.1 which is typical for other recently discovered ultra-faint dwarf galaxies.[10]
In 1986,Allan Sandage estimated the distance to NGC 300 to be 5.41 Mly (1.66 Mpc).[11] By 1992, this had been updated to 6.9 Mly (2.1 Mpc) by Freedman et al.[2] In 2006, this was revised by Karachentsev et al. to be7.0±0.3 Mly (2.15±0.10 Mpc).[12] At about the same time, thetip of the red giant branch (TRGB) method was used to produce an estimate of5.9±0.4 Mly (1.82±0.13 Mpc) using edge detection and6.1±0.4 Mly (1.87±0.12 Mpc) using maximum likelihood.[2] These results were consistent with estimates using near-infrared photometry ofCepheid variables by Gieren et al. 2005 that provided an estimate of6.1±0.2 Mly (1.88±0.07 Mpc).[2] Combining the recent TRGB and Cepheid estimates the distance to NGC 300 is estimated at6.07±0.23 Mly (1.86±0.07 Mpc).[a]
On aCCD image obtained on 14 May 2008, amateur astronomer L.A.G. Berto Monard discovered a brightoptical transient (OT) in NGC 300 that is designated NGC 300-OT.[13][14] It is located atRA: 00h 54m 34.552s andDEC: −37° 38′ 31.79″[15] in aspiral arm containing active star formation.[16] Its broad-band magnitude was 14.3 in that image. An earlier image (from 24 April 2008), taken just after NGC 300 reemerged from behind theSun, evidenced an already brightening OT at ~16.3 magnitude.[16] No brightening was detected on a 8 February 2008 image, nor on any earlier ones.[16] The transient's peak measured magnitude was 14.69 on 15 May 2008.[16]
At discovery, the transient had an absolute magnitude ofMV ≈ −13, making it faint in comparison to a typicalcore-collapse supernova but bright in comparison to aclassical nova.[14][16] Additionally, the photometric and spectroscopic properties of the OT imply that it is not aluminous blue variable either.[16] Since its peak, brightness dropped smoothly through September 2008 while becoming continuously redder.[16] After September 2008, brightness continued to fall at a lower rate in the optical spectrum but with strongHα emissions.[16] Further, the optical spectrum is mostly made up of fairly narrowHydrogen Balmer and Ca II emission lines coupled with strong Ca II H&K absorption.[14] Research into historicalHubble images provide an accurate upper bound on the progenitor star's brightness.[14] This suggested a low-massmain sequence star as progenitor with the transient resulting from a stellar merger similar to red Galactic novaV838 Monocerotis.[14] 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.[15]
However, in 2008 a brightmid-infrared progenitor to the transient was discovered in historicalSpitzer data. This was a star that was obscured by dust, with energy distribution analogous to ablack-body ofR ≈ 300AU and radiating atT ≈ 300K withLbol ≈×106L⊙. 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 toNGG 6946'sSN 2008S.[14]
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 Galacticcarbon-richprotoplanetary nebulae.[14]
On 19 April 2025, NGC 300-OT was classified as an Intermediate-Luminosity Red Transient (ILRT).[17]
SN 2010da (type LBV, mag. 16) was discovered by Monard on 23 May 2010.[18][19] 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.[20]
Two sets of independent follow-up spectroscopy data suggested that this was again another optical transient rather than a supernova, possibly an outburstingluminous blue variable star according to one spectrum,[21][22] as earlier predicted from the nature of the candidate mid-infrared progenitor.[23] The transient faded by 0.5–0.7 mag in 9 days, much faster than the 2008 transient in NGC 300.[24]
AT 2019qyl was discovered by theDistance Less Than 40 Mpc Survey (DLT40) on 26 September 2019, at magnitude 17.1. It was initially classified as a type IIn/LBV,[25] but later analysis classified the star as a classicalnova.[26]
SN 2020acli (type IIn-pec, mag. 18.4205) was discovered by theDistance Less Than 40 Mpc Survey (DLT40) on 12 December 2020.[27]
AT 2024oth (type unknown, mag. 19.85) was discovered byBlackGEM on 27 June 2024.[28]
AT 2024txt (type unknown, mag. 19.77) was discovered byPan-STARRS on 29 July 2024.[29]
Anx-ray source in NGC 300 is designated NGC 300 X-1.[30] Astronomers speculate that NGC 300 X-1 is a new kind ofWolf-Rayet +stellar black holebinary system similar to the confirmed such systemIC 10 X-1.[30] Their shared properties include anorbital period of 32.8 hours. The black hole has a mass of 17 ± 4M☉ and the WR star has a mass of26+7
−5M☉. Both objects orbit each other at a distance of about 18.2R☉.[31]
There is an oxygen-sequence Wolf–Rayet star (WO4 type), known as STWR 13, located in one of the bright H II regions in NGC 300.[32]
