NGC 300

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NGC 300 (also known as Caldwell 70 or the Sculptor Pinwheel Galaxy<ref name="interstellarum">Template:Cite book</ref>) is a spiral galaxy in the constellation Sculptor. It was discovered on 5 August 1826 by Scottish astronomer James Dunlop.<ref name="selig">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It is one of the closest galaxies to the Local Group, and it most likely lies between the latter and the Sculptor Group. It is the brightest of the five main spirals in the direction of the Sculptor Group.<ref name="Rizzietal2006" /> It is inclined at an angle of 42° when viewed from Earth and shares many characteristics of the Triangulum Galaxy.<ref name="Vlajićetal2009"> Template:Cite journal</ref> It is about 55,000 light-years in diameter, somewhat smaller than the Milky Way, and has an estimated mass of (2.9 ± 0.2) × 10¹⁰ Template:Solar mass.<ref name="West">Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Nearby galaxies and group informationEdit

NGC 300 and the Magellanic type barred spiral 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.<ref name="karachentsevetal2003"> Template:Cite journal</ref> It is likely that NGC 300 and NGC 55 form a gravitationally bound pair.<ref name = "vandesteeneetal2006"> Template:Cite journal</ref>

The dwarf galaxy Sculptor C is located about 6.65 million light-years (2.04 megaparsecs) away from the Sun, and is very likely a satellite 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.<ref name=Sand2024>Template:Cite journal</ref>

Distance estimatesEdit

In 1986, Allan Sandage estimated the distance to NGC 300 to be 5.41 Mly (1.66 Mpc).<ref name="Sandage1986"> Template:Cite journal</ref> By 1992, this had been updated to 6.9 Mly (2.1 Mpc) by Freedman et al.<ref name="Rizzietal2006"> Template:Cite journal</ref> In 2006, this was revised by Karachentsev et al. to be Template:Val (Template:Val).<ref name="Karachentsevetal2006"> Template:Cite journal</ref> At about the same time, the tip of the red giant branch (TRGB) method was used to produce an estimate of Template:Val (Template:Val) using edge detection and Template:Val (Template:Val) using maximum likelihood.<ref name="Rizzietal2006" /> These results were consistent with estimates using near-infrared photometry of Cepheid variables by Gieren et al. 2005 that provided an estimate of Template:Val (Template:Val).<ref name="Rizzietal2006" /> Combining the recent TRGB and Cepheid estimates the distance to NGC 300 is estimated at Template:Val (Template:Val).Template:Ref label

NGC 300-OTEdit

On a CCD image obtained on May 14, 2008, amateur astronomer L.A.G. Berto Monard discovered a bright optical transient (OT) in NGC 300 that is designated NGC 300-OT.<ref name="PrietoEtAl2009" /> It is located at RA: Template:RA and DEC: Template:DEC<ref name="Gogartenetal2009"> Template:Cite journal</ref> in a spiral arm containing active star formation.<ref name="Bondetal2009" /> 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.<ref name="Bondetal2009"> Template:Cite journal</ref> No brightening was detected on a February 8, 2008 image or on any earlier ones.<ref name="Bondetal2009" /> The transient's peak measured magnitude was 14.69 on May 15, 2008.<ref name="Bondetal2009" />

At discovery, the transient had an absolute magnitude of Template:Nowrap, making it faint in comparison to a typical core-collapse supernova but bright in comparison to a classical nova.<ref name="PrietoEtAl2009" /><ref name="Bondetal2009" /> Additionally, the photometric and spectroscopic properties of the OT imply that it is not a luminous blue variable either.<ref name="Bondetal2009" /> Since its peak, brightness dropped smoothly through September 2008 while becoming continuously redder.<ref name="Bondetal2009" /> After September 2008, brightness continued to fall at a lower rate in the optical spectrum but with strong Hα emissions.<ref name="Bondetal2009" /> 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.<ref name="PrietoEtAl2009" /> Research into historical Hubble images provide an accurate upper bound on the progenitor star's brightness.<ref name="PrietoEtAl2009" /> 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.<ref name="PrietoEtAl2009"> Template:Cite journal</ref> 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.<ref name="Gogartenetal2009" />

File:NGC 300 Hubble.jpg

NGC 300 zoom-in by the Hubble Space Telescope

File:Composite Image of NGC 300.jpg

NGC 300 by GALEX, in ultraviolet light

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 Template:Nowrap AU and radiating at Template:Nowrap K with Template:Nowrap. 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.<ref name="PrietoEtAl2009" />

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.<ref name="PrietoEtAl2009" />

On April 19, 2025, NGC 300-OT was classified as an Intermediate-Luminosity Red Transient (ILRT).<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

SN 2010daEdit

On May 23, 2010, Monard discovered another transient object of 16th magnitude, denoted as SN 2010da.<ref name=atel2640>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref name=sn-list>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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,<ref name=atel2636>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name=atel2637>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> as earlier predicted from the nature of the candidate mid-infrared progenitor.<ref name=atel2632>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The transient faded by 0.5–0.7 mag in 9 days, much faster than the 2008 transient in NGC 300.<ref name=atel2660>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Other Novae, Supernovae, and TransientsEdit

AT 2019qyl was discovered on 26 September 2019, at magnitude 17.1. It was initially classified as a type IIn/LBV,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> but later analysis classified the star as a classical nova.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

SN 2020acli (type IIn-pec, mag. 18.4205) was discovered by the Distance Less Than 40 Mpc Survey (DLT40) on 12 December 2020.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

AT 2024oth (type unknown, mag. 19.85) was discovered by BlackGEM on 27 June 2024.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

AT 2024txt (type unknown, mag. 19.77) was discovered by Pan-STARRS on 29 July 2024.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Binary black hole systemEdit

An x-ray source in NGC 300 is designated NGC 300 X-1.<ref name = "Barnardetal2008" /> Astronomers speculate that NGC 300 X-1 is a new kind of Wolf-Rayet + stellar black hole binary system similar to the confirmed such system IC 10 X-1.<ref name = "Barnardetal2008"> Template:Cite journal</ref> Their shared properties include an orbital period of 32.8 hours. The black hole has a mass of 17 ± 4 Template:Solar mass and the WR star has a mass of Template:Val Template:Solar mass. Both objects orbit each other at a distance of about 18.2 Template:Solar radius.<ref>Template:Cite journal</ref>

WO starEdit

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.<ref>Template:Cite journal</ref>