NGC 5189 (Gum 47, IC 4274, nicknamed Spiral Planetary Nebula) is a planetary nebula in the constellation Musca. It was discovered by James Dunlop on 1 July 1826, who catalogued it as Δ252. For many years, well into the 1960s, it was thought to be a bright emission nebula. It was Karl Gordon Henize in 1967 who first described NGC 5189 as quasi-planetary based on its spectral emissions.
Seen through the telescope it seems to have an S shape, reminiscent of a barred spiral galaxy. The S shape, together with point-symmetric knots in the nebula, have for a long time hinted to astronomers that a binary central star is present. The Hubble Space Telescope imaging analysis showed that this S shape structure is indeed two dense low-ionization regions: one moving toward the north-east and another one moving toward the south-west of the nebula, which could be a result of a recent outburst from the central star. Observations with the Southern African Large Telescope have finally found a white dwarf companion in a 4.04 day orbit around the rare low-mass Wolf-Rayet type central star of NGC 5189. NGC 5189 is estimated to be 546 parsecs or 1,780 light years away from Earth. Other measurements have yielded results up to 900 parsecs (~3000 light-years)
NGC 5189 image taken with the Hubble Space Telescope on July 6, 2012
|Observation data: J2000.0 epoch|
|Right ascension||13h 33m 32.97s|
|Declination||−65° 58′ 26.7″|
|Distance||3000 ly ly|
|Apparent magnitude (V)||8.2, 8.5p|
|Apparent dimensions (V)||90 × 62 arcsec|
|Radius||~1 ly ly|
|Absolute magnitude (V)||-|
|Notable features||A peculiar PN with a binary in the center|
|Designations||Spiral Planetary Nebula, Gum 47, IC 4274, He2-94, Sa2-95, PK 307-3.1|
Media related to NGC 5189 at Wikimedia Commons
ι1 Muscae, Latinised as Iota1 Muscae, is a solitary star in the constellation Musca. Its apparent magnitude is 5.04. Located around 67.80 parsecs (221.1 ly) distant, it is an orange giant of spectral type K0III, a star that has used up its core hydrogen and is cooling and expanding. The measured angular diameter is 1.50±0.02 mas. At the estimated distance of the star, this yields a physical size of about 11 times the radius of the Sun.List of planetary nebulae
The following is an incomplete list of known planetary nebulae.List of stars in Musca
This is the list of notable stars in the constellation Musca, sorted by decreasing brightness.Mu Muscae
Mu Muscae, Latinized from μ Muscae, is a solitary star in the southern constellation of Musca. It is visible to the naked eye with an apparent visual magnitude of around 4.75. Based upon an annual parallax shift of 8.97 mas as seen from Earth, it is located about 360 light years from the Sun.
This is an evolved K-type giant star with a stellar classification of K4 III. It most likely on the red giant branch, rather than the asymptotic giant branch, and shows no signs of mass loss. Mu Muscae is an oxygen-rich irregular variable with a small amplitude that varies in visual magnitude between 4.71 and 4.76. It is radiating 465 times the luminosity of the Sun from its photosphere at an effective temperature of 4,086 K.Musca
Musca (Latin for "the fly") is a small constellation in the deep southern sky. It was one of 12 constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman, and it first appeared on a celestial globe 35 cm (14 in) in diameter published in 1597 (or 1598) in Amsterdam by Plancius and Jodocus Hondius. The first depiction of this constellation in a celestial atlas was in Johann Bayer's Uranometria of 1603. It was also known as Apis (Latin for "the bee") for 200 years. Musca remains below the horizon for most Northern Hemisphere observers.
Many of the constellation's brighter stars are members of the Scorpius–Centaurus Association, a loose group of hot blue-white stars that appears to share a common origin and motion across the Milky Way. These include Alpha, Beta, Gamma, Zeta2 and (probably) Eta Muscae, as well as HD 100546, a blue-white Herbig Ae/Be star that is surrounded by a complex debris disk containing a large planet or brown dwarf and possible protoplanet. Two further star systems have been found to have planets. The constellation also contains two cepheid variables visible to the naked eye. Theta Muscae is a triple star system, the brightest member of which is a Wolf–Rayet star.NGC 6905
NGC 6905, also known as the Blue Flash Nebula, is a planetary nebula in the constellation Delphinus. It was discovered by William Herschel in 1784. The central star is 14.0 mag. The distance of the nebula, as with most planetary nebulae, is not well determined and estimates range between 1.7 and 2.6 kpc.The shape of NGC 6905 is characterised by an internal shell with angular dimensions 47" ×34" and roughly conical extensions, with ansae-type formations along the major axis. The nucleus of the nebula possesses one of the most broad emission of OVI emission lines among planetary nebulae. Moreover, OVIII emission has been detected in NGC 6905. The ansae were particularly intense in NII. The central star, a white dwarf is estimated to have surface temperature 150.000 K.NGC 6905 can be detected under dark skies with a 4-inch telescope, but it better observed with larger instruments.Wolf–Rayet star
Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectra showing prominent broad emission lines of ionised helium and highly ionised nitrogen or carbon. The spectra indicate very high surface enhancement of heavy elements, depletion of hydrogen, and strong stellar winds. Their surface temperatures range from 30,000 K to around 200,000 K, hotter than almost all other stars. They were previously called W-type stars referring to their spectral classification.
Classic (or Population I) Wolf–Rayet stars are evolved, massive stars that have completely lost their outer hydrogen and are fusing helium or heavier elements in the core. A subset of the population I WR stars show hydrogen lines in their spectra and are known as WNh stars; they are young extremely massive stars still fusing hydrogen at the core, with helium and nitrogen exposed at the surface by strong mixing and radiation-driven mass loss. A separate group of stars with WR spectra are the central stars of planetary nebulae (CSPNe), post asymptotic giant branch stars that were similar to the Sun while on the main sequence, but have now ceased fusion and shed their atmospheres to reveal a bare carbon-oxygen core.
All Wolf–Rayet stars are highly luminous objects due to their high temperatures—thousands of times the bolometric luminosity of the Sun (L☉) for the CSPNe, hundreds of thousands L☉ for the Population I WR stars, to over a million L☉ for the WNh stars—although not exceptionally bright visually since most of their radiation output is in the ultraviolet.
The naked-eye stars Gamma Velorum and Theta Muscae, as well as the most massive known star, R136a1 in 30 Doradus, are all Wolf–Rayet stars.
See also: Gum Nebula
New General Catalogue 5000 to 5499