NGC 3147 is a spiral galaxy located in the constellation Draco. It is located at a distance of circa 130 million light years from Earth, which, given its apparent dimensions, means that NGC 3147 is about 140,000 light years across. It was discovered by William Herschel οn April 3, 1785. It is a Type II Seyfert galaxy.
NGC 3147 by Hubble Space Telescope
|Observation data (J2000 epoch)|
|Right ascension||10h 16m 53.7s|
|Declination||+73° 24′ 03″|
|Redshift||0.009346 ± 0.000003 |
|Helio radial velocity||2,802 ± 1 km/s|
|Distance||129 ± 29 Mly (39.6 ± 8.9 Mpc)|
|Apparent magnitude (V)||10.6|
|Apparent size (V)||3′.9 × 3′.5|
|Notable features||Seyfert galaxy|
|UGC 5532, MCG +12-10-025, PGC 30019|
The galaxy has a small and bright nucleus and tightly wound multiple spiral arms. The overall appearance of the galaxy resambles that of NGC 488, however the nuclear bulge is smaller. The arms consist of spiral segments that branch after approximately one quarter of a revolution. HII regions can be detacted in the arms.
NGC 3147 has been characterised as a Seyfert II galaxy. It is considered the best candidate to be a true type II Seyfert galaxy, galaxies which feature optical/UV spectrum lacking broad emission lines due to the lack of the broad line region rather than its obscuration, since the nucleus is simultaneously seen unobscured in the X-rays.
The galaxy was observed stimultaneously in the optical and X-ray spectrum by Bianchi et al. and concluded that the X-ray spectrum is unabsorbed while its optical spectrum lacks broad lines, a missmatch with respect to the Unification Model. Birghtman et al. confirmed their findings and also noted that the hard X-ray flux dropped by a factor of ∼2 between the observation by Chandra (2001) and XMM-Newton (2006). Further flux variation was observed by Suzaku in 2010, confirming the variability of the source. The nuclear emission in the UV band shows negligible variability. Shi et al. used data from Spitzer Space Telescope and ground-based optical spectropolarimeteric observations and observed lack of polarised broad emission lines in NGC 3147. NGC 3147 was observed by NuSTAR at the 3-40 keV X-ray spectrum, which is characterised by a simple power-law, with a standard Γ ∼ 1.7 and an iron emission line, with no need for any further component up to ∼ 40 keV.
There is a debate whether the lack of broad lines detection observed with NGC 3147 is caused by the presence of an Compton-thick column with the presence of a highly ionised reflactor to account for the X-ray spectrum or not. Bianchi et al. rejected the presence of a Compton thick column on the grounds of low-equivalent width of the iron Kα line (≃130 eV), and of the large ratio between hard X-ray and [O III] fluxes. Birghtman et al. confirmed their findings using data from XMM-Newton and Chandra. They also found that the X-ray flux is variable, meaning that the nucleus may be observed directly. However, they noted the presence of Compton-thick column cannot be ruled out. The observations by Suzaku in the hard X-rays spectrum didn't cast more light, but along with the observations performed by XMM-Newton put tight constraints on the column density.
After the observations by NuStar in 2015, Bianchi et al. concluded that the spectral properties and the significant variability on time-scales as short as weeks strongly support an unobscured line-of-sight for the nucleus of NGC 3147 and the Compton-thick scenario is strongly disfavoured.
NGC 3147 is the brightest galaxy in the NGC 3147 group, which also includes NGC 3155, UGC 5570, UGC 5686, and UGC 5689. A bit further away lie NGC 3183, NGC 3348, NGC 3364, and NGC 3516.
7 Draconis, also named Tianyi (or) , is a single star in the northern circumpolar constellation of Draco. It is visible to the naked eye as a faint orange-hued star with a stellar classification of 5.43. Based upon an annual parallax shift of 4.16 mas as seen from the Earth, the star is located approximately 780 light-years from the Sun.
This is an evolved giant star with a stellar classification of K5 III. The measured angular diameter of this star, after correction for limb darkening, is 2.61±0.03 mas. At its estimated distance, this yields a physical size of about 67 times the radius of the Sun. It is radiating about 1,024 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,945 K.8 Draconis
8 Draconis, formally named Taiyi , is a single star in the northern circumpolar constellation of Draco. Based upon an annual parallax shift of 34.14 mas as seen from the Earth, the star is located approximately 96 light-years from the Sun. It is moving further away with a heliocentric radial velocity of +9 km/s, having come within 40.6 ly some 2.6 million years ago.This is an F-type main-sequence star with a stellar classification of F1VmA7(n). It is a Gamma Doradus variable star with a brightness variation of about one tenth of a magnitude. 8 Dra has a relatively high rate of rotation, showing a projected rotational velocity of 120 km/s. The star has 1.56 times the mass of the Sun and 1.50 times the Sun's radius. It is radiating 5.75 times the Sun's luminosity from its photosphere at an effective temperature of 7,129 K. An infrared excess has been detected at wavelengths of 24 and 70μm, which suggests the presence of a circumstellar disk orbiting the star.Alruba
Alruba , designated HD 161693 and HR 6618, is a star in the northern circumpolar constellation of Draco. Based on parallax measurements obtained during the Gaia mission, it is about 457 light-years (140 parsecs) distant from the Sun.Herschel 400 Catalogue
The Herschel 400 catalogue is a subset of William Herschel's original Catalogue of Nebulae and Clusters of Stars, selected by Brenda F. Guzman (Branchett), Lydel Guzman, Paul Jones, James Morrison, Peggy Taylor and Sara Saey of the Ancient City Astronomy Club in St. Augustine, Florida, United States c. 1980. They decided to generate the list after reading a letter published in Sky & Telescope by James Mullaney of Pittsburgh, Pennsylvania, USA.In this letter Mr. Mullaney suggested that William Herschel's original catalogue of 2,500 objects would be an excellent basis for deep sky object selection for amateur astronomers looking for a challenge after completing the Messier Catalogue.
The Herschel 400 is a subset of John Herschel's General Catalogue of Nebulae and Clusters published in 1864 of 5,000 objects, and hence also of the New General Catalogue.
The catalogue forms the basis of the Astronomical League's Herschel 400 club. In 1997, another subset of 400 Herschel objects was selected by the Rose City Astronomers of Portland, Oregon as the Herschel II list, which forms the basis of the Astronomical League's Herschel II Program.Lambda Draconis
Lambda Draconis (λ Draconis, abbreviated Lam Dra, λ Dra), also named Giausar , is a solitary, orange-red star in the northern circumpolar constellation of Draco. It is visible to the naked eye with an apparent visual magnitude of +3.85. Based upon an annual parallax shift of 9.79 mas as seen from the Earth, the star is located around 333 light years from the Sun.
This is an evolved red giant star on the asymptotic giant branch with a stellar classification of M0III-IIIa Ca1. It is a suspected slow irregular variable with a periodicity of roughly 1,100 days. The measured angular diameter, after correction for limb darkening, is 6.43±0.07 mas. At the estimated distance of the star, this yields a physical size of about 53 times the radius of the Sun. It has an estimated 1.7 times the mass of the Sun and is radiating 834 times the solar luminosity from its photosphere at an effective temperature of 3,958 K.Pi Draconis
Pi Draconis, Latinized from π Draconis, is a solitary star in the northern circumpolar constellation of Draco. It is visible to the naked eye with an apparent visual magnitude of 4.59. Based upon an annual parallax shift of 14.25 mas as measured from Earth, it is located around 229 light years from the Sun. At that distance, the visual magnitude is diminished by an extinction factor of 0.063±0.10 due to interstellar dust.With an age of 350 million years, this is an A-type star of stellar classification A2 IIIs, where the luminosity class of III typically indicates an evolved giant star and the 's' means the spectrum displays sharp absorption lines. It is a candidate Am star, meaning there are some chemical peculiarities. The measured angular size is 0.427±0.062 arc seconds. At the estimated distance of Pi Draconis, this yields a physical size of about 3.2 times the radius of the Sun. It has about 2.70 times the mass of the Sun and is radiating 60 times the solar luminosity from its photosphere at an effective temperature of 9,125 K.Psi2 Draconis
Psi2 Draconis is a solitary giant star in the northern circumpolar constellation of Draco, also designated 34 Draconis. It lies about a degree east of the brighter Psi1 Draconis.
Psi2 Draconis has an apparent magnitude of 5.45. and is located around 287 parsecs (940 ly) away. It is a white giant of spectral type F2III+, a star that has used up its core hydrogen, cooled, and expanded away from the main sequence. It is now over 500 times as luminous as the sun.Rho Draconis
Rho Draconis (ρ Draconis) is a solitary star in the northern circumpolar constellation of Draco. It is faintly visible to the naked eye with an apparent visual magnitude is 4.52. Based upon an annual parallax shift of 7.61 mas as measured from Earth, it is located around 429 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.027 due to interstellar dust.With a stellar classification of K3 III, Rho Draconis is a normal giant star that is past the first dredge-up phase of its post-main sequence evolution. It has the peculiar spectrum of a CN star, showing abnormal line strengths for cyanogen and calcium. The star has expanded to around 28 times the Sun's radius and it is radiating 402 times the solar luminosity from its photosphere at an effective temperature of 4,370 K.Stars named after people
Over the past few centuries, a small number of stars have been named after individual people. It is common in astronomy for objects to be given names, in accordance with accepted astronomical naming conventions. Most stars have not been given proper names, relying instead on alphanumeric designations in star catalogues. However, a few hundred had either long-standing traditional names (usually from the Arabic) or historic names from frequent usage.
In addition, many stars have catalogue designations that contain the name of their compiler or discoverer. This includes Wolf, Ross, Bradley, Piazzi, Lacaille, Struve, Groombridge, Lalande, Krueger, Mayer, Weisse, Gould, Luyten and others. For example, Wolf 359, discovered and catalogued by Max Wolf.Stephen P. Laurie
Stephen P. Laurie is a British amateur astronomer. He is a prolific discoverer of asteroids and comets, although his profession is that of an actuary. He has also worked on searches for dwarf stars and discovered a supernova (SN 1997bq in NGC 3147) in 1997.Laurie has named five asteroids he discovered from the Church Stretton area — 7603 Salopia (named after Shropshire,) 9421 Violilla, 9428 Angelalouise, 10216 Popastro and 11626 Church Stretton — all discovered at observatory 966 Church Stretton and nearby location Ragdon (observatory J17). Laurie lives and works in the Church Stretton area.Tau Draconis
Tau Draconis, Latinized from τ Draconis, is an astrometric binary star system in the northern circumpolar constellation of Draco. The star is faintly visible to the naked eye, having an apparent visual magnitude of 4.45. Based upon an annual parallax shift of 22.28 mas as measured from Earth, it is located around 146 light years from the Sun. Its proper motion is propelling it across the sky at the rate of 0.176 arc seconds per year.This is a K-type giant star with a stellar classification of K2 III:, where the semi-colon indicates some uncertainty about its spectral value. It is considered metal-rich star and is past the first dredge-up phase of its post-main sequence evolution, although it shows under-abundances of carbon and oxygen in its spectrum. The star has 1.25 times the mass of the Sun and is an estimated 6.48 billion years old. It is radiating 48 times the solar luminosity from its enlarged photosphere at an effective temperature of 4,413 K.Thuban
Thuban , designation Alpha Draconis (α Draconis, abbreviated Alpha Dra, α Dra), is a star (or star system) in the constellation of Draco. A relatively inconspicuous star in the night sky of the Northern Hemisphere, it is historically significant as having been the north pole star from the 4th to 2nd millennium BC.
Even though Johann Bayer gave Thuban the designation Alpha, its apparent magnitude of 3.65 means it is 3.7 times fainter than the brightest star in the constellation, Gamma Draconis (Eltanin), whose apparent magnitude is 2.24.Upsilon Draconis
Upsilon Draconis (υ Dra) is a binary star system in the northern circumpolar constellation of Draco. It is faintly visible to the naked eye with an apparent visual magnitude of 4.83. Based upon an annual parallax shift of 9.48 mas as measured from Earth, it is located around 340 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.02 due to interstellar dust.In Chinese, 紫微左垣 (Zǐ Wēi Zuǒ Yuán), meaning Left Wall of Purple Forbidden Enclosure, refers to an asterism consisting of υ Draconis, ι Draconis, η Draconis, ζ Draconis, θ Draconis, 73 Draconis, γ Cephei and 23 Cassiopeiae. Consequently, the Chinese name for ζ Draconis itself is 紫微左垣五 (Zǐ Wēi Zuǒ Yuán wu, English: the Fifth Star of Left Wall of Purple Forbidden Enclosure.), representing 少弼 (Shǎobì), meaning The Second Minister.
This is a single-lined spectroscopic binary star system with an orbital period of 258.48 days and an eccentricity of 0.21. The primary, component A, is an evolved K-type giant star with a stellar classification of K0 III. It is a suspected barium star, which may indicate the orbiting companion, component B, is a white dwarf star.The measured angular diameter of the primary, after correction for limb darkening, is 1.69±0.02 mas. At the estimated distance of Upsilon Draconis, this yields a physical size of about 19 times the Sun's radius. It is about 1.37 billion years old with an estimated 2.05 times the mass of the Sun. The star is radiating 2.23 times the solar luminosity from its photosphere at an effective temperature of 4,561 K.
New General Catalogue 3000 to 3499