NGC 300 | |
---|---|
Observation data (J2000 epoch) | |
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 ± 0.23 Mly (1.86 ± 0.07 Mpc) [2] [a] |
Apparent magnitude (V) | 9.0 [1] |
Characteristics | |
Type | SA(s)d [1] |
Mass | (2.9 ± 0.2) × 1010 M☉ |
Size | ~110,000 ly (35 kpc) (estimated) [3] |
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 as Caldwell 70 or the Sculptor Pinwheel Galaxy [4] ) is a spiral galaxy in the constellation Sculptor. It was discovered on 5 August 1826 by Scottish astronomer James Dunlop. [5] 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. [2] It is inclined at an angle of 42° when viewed from Earth and shares many characteristics of the Triangulum Galaxy. [6] It is 94,000 light-years in diameter, somewhat smaller than the Milky Way, and has an estimated mass of (2.9 ± 0.2) × 1010M☉. [3] [7]
NGC 300 and the irregular 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. [8] It is likely that NGC 300 and NGC 55 form a gravitationally bound pair. [9]
In 1986, Allan Sandage estimated the distance to NGC 300 to be 5.41 Mly (1.66 Mpc). [10] 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 be 7.0±0.3 Mly (2.15±0.10 Mpc). [11] At about the same time, the tip of the red giant branch (TRGB) method was used to produce an estimate of 5.9±0.4 Mly (1.82±0.13 Mpc) using edge detection and 6.1±0.4 Mly (1.87±0.12 Mpc) using maximum likelihood. [2] These results were consistent with estimates using near-infrared photometry of Cepheid variables by Gieren et al. 2005 that provided an estimate of 6.1±0.2 Mly (1.88±0.07 Mpc). [2] Combining the recent TRGB and Cepheid estimates the distance to NGC 300 is estimated at 6.07±0.23 Mly (1.86±0.07 Mpc). [a]
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. [12] It is located at RA: 00h 54m 34.552s and DEC: −37° 38′ 31.79″ [13] in a spiral arm containing active star formation. [14] 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. [14] No brightening was detected on a February 8, 2008 image or on any earlier ones. [14] The transient's peak measured magnitude was 14.69 on May 15, 2008. [14]
At discovery, the transient had an absolute magnitude of MV ≈ −13, making it faint in comparison to a typical core-collapse supernova but bright in comparison to a classical nova. [12] [14] Additionally, the photometric and spectroscopic properties of the OT imply that it is not a luminous blue variable either. [14] Since its peak, brightness dropped smoothly through September 2008 while becoming continuously redder. [14] After September 2008, brightness continued to fall at a lower rate in the optical spectrum but with strong Hα emissions. [14] 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. [12] Research into historical Hubble images provide an accurate upper bound on the progenitor star's brightness. [12] 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. [12] 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. [13]
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 R ≈ 300 AU and radiating at T ≈ 300 K with Lbol ≈ ×106 L⊙ . 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. [12]
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. [12]
On May 23, 2010, Monard discovered another transient object of 16th magnitude, denoted as SN 2010da. [15] 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. [16]
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, [17] [18] as earlier predicted from the nature of the candidate mid-infrared progenitor. [19] The transient faded by 0.5–0.7 mag in 9 days, much faster than the 2008 transient in NGC 300. [20]
AT 2019qyl was discovered on 26 September 2019, at magnitude 17.1. It was initially classified as a type IIn/LBV, [21] but later analysis classified the star as a classical nova. [22]
SN 2020acli (type IIn-pec, mag. 18.4) was discovered on 12 December 2020. [23]
An x-ray source in NGC 300 is designated NGC 300 X-1. [24] 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. [24] Their shared properties include an orbital period of 32.8 hours. The black hole has a mass of 17 ± 4 M☉ and the WR star has a mass of 26+7
−5M☉. Both objects orbit each other at a distance of about 18.2 R☉. [25]
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. [26]
Centaurus A is a galaxy in the constellation of Centaurus. It was discovered in 1826 by Scottish astronomer James Dunlop from his home in Parramatta, in New South Wales, Australia. There is considerable debate in the literature regarding the galaxy's fundamental properties such as its Hubble type and distance. It is the closest radio galaxy to Earth, as well as the closest BL Lac object, so its active galactic nucleus has been extensively studied by professional astronomers. The galaxy is also the fifth-brightest in the sky, making it an ideal amateur astronomy target. It is only visible from the southern hemisphere and low northern latitudes.
Messier 74 is a large spiral galaxy in the equatorial constellation Pisces. It is about 32 million light-years away from Earth. The galaxy contains two clearly defined spiral arms and is therefore used as an archetypal example of a grand design spiral galaxy. The galaxy's low surface brightness makes it the most difficult Messier object for amateur astronomers to observe. Its relatively large angular size and the galaxy's face-on orientation make it an ideal object for professional astronomers who want to study spiral arm structure and spiral density waves. It is estimated that M74 hosts about 100 billion stars.
NGC 3184, the Little Pinwheel Galaxy, is a spiral galaxy approximately 40 million light-years away in the constellation Ursa Major. Its name comes from its resemblance to the Pinwheel Galaxy. It was discovered on 18 March 1787 by German-British astronomer William Herschel. It has two HII regions named NGC 3180 and NGC 3181.
NGC 4725 is an intermediate barred spiral galaxy with a prominent ring structure, located in the northern constellation of Coma Berenices near the north galactic pole. It was discovered by German-born British astronomer William Herschel on April 6, 1785. The galaxy lies at a distance of approximately 40 megalight-years from the Milky Way. NGC 4725 is the brightest member of the Coma I Group of the Coma-Sculptor Cloud, although it is relatively isolated from the other members of this group. This galaxy is strongly disturbed and is interacting with neighboring spiral galaxy NGC 4747, with its spiral arms showing indications of warping. The pair have an angular separation of 24′, which corresponds to a projected linear separation of 370 kly. A tidal plume extends from NGC 4747 toward NGC 4725.
NGC 4603 is a spiral galaxy located about 107 million light years away in the constellation Centaurus. It is a member of the Centaurus Cluster of galaxies, belonging to the section designated "Cen30". The morphological classification is SA(s)c, which indicates it is a pure spiral galaxy with relatively loosely wound arms.
NGC 4051 is an intermediate spiral galaxy in the constellation of Ursa Major. It was discovered on 6 February 1788 by John Herschel.
NGC 2770 is a spiral galaxy in the northern constellation of Lynx, near the northern constellation border with Cancer. It was discovered by German-born astronomer William Herschel on December 7, 1785. J. L. E. Dreyer described it as, "faint, large, much extended 150°, mottled but not resolved, 2 stars to north". NGC 2770 was the target for the first binocular image produced by the Large Binocular Telescope.
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Supernova impostors are stellar explosions that appear at first to be a supernova but do not destroy their progenitor stars. As such, they are a class of extra-powerful novae. They are also known as Type V supernovae, Eta Carinae analogs, and giant eruptions of luminous blue variables (LBV).
NGC 3621 is a field spiral galaxy about 22 Mly (6.7 Mpc) away in the equatorial constellation of Hydra. It is comparatively bright and can be well seen in moderate-sized telescopes. The galaxy is around 93,000 ly (29,000 pc) across and is inclined at an angle of 66° from being viewed face on. It shines with a luminosity equal to 13 billion times that of the Sun. The morphological classification is SA(s)d, which indicates this is an ordinary spiral with loosely wound arms. There is no evidence for a bulge. Although it appears to be isolated, NGC 3621 belongs to the Leo spur.
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SN 2009ip was a supernova discovered in 2009 in the spiral galaxy NGC 7259 in the constellation of Piscis Austrinus. Since the brightness waned after days post-discovery, it was redesignated as Luminous blue variable (LBV) Supernova impostor.
NGC 4242 is a spiral galaxy in the northern constellation of Canes Venatici. The galaxy is about 18 million light years away. It was discovered on 10 April 1788 by William Herschel, and it was described as "very faint, considerably large, irregular, round, very gradually brighter in the middle, resolvable" by John Louis Emil Dreyer, the compiler of the New General Catalogue.
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In astronomy, a fast blue optical transient (FBOT), or more specifically, luminous fast blue optical transient (LFBOT), is an explosive transient event similar to supernovae and gamma-ray bursts with high optical luminosity, rapid evolution, and predominantly blue emission. The origins of such explosions are currently unclear, with events occurring at not more than 0.1% of the typical core-collapse supernova rate. This class of transients initially emerged from large sky surveys at cosmological distances, yet in recent years a small number have been discovered in the local Universe, most notably AT 2018cow.
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