Deneb
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Double star Deneb (α Cygni) |
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| Deneb in the constellation Swan | |||||||||||||||||||||||||||||
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Observation dates equinox : J2000.0 , epoch : J2000.0 |
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| AladinLite | |||||||||||||||||||||||||||||
| Constellation | swan | ||||||||||||||||||||||||||||
| Right ascension | 20 h 41 m 25.915 s | ||||||||||||||||||||||||||||
| declination | + 45 ° 16 ′ 49.220 ″ | ||||||||||||||||||||||||||||
| Apparent brightness | 1.25 mag | ||||||||||||||||||||||||||||
| Astrometry | |||||||||||||||||||||||||||||
| Radial velocity | (−4.9 ± 0.3) km / s | ||||||||||||||||||||||||||||
| parallax | (2.31 ± 0.32) mas | ||||||||||||||||||||||||||||
| distance | 1411.96 Lj (432.90 pc ) |
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| Proper movement : | |||||||||||||||||||||||||||||
| Rec. Share: | 1.56 mas / a | ||||||||||||||||||||||||||||
| Dec. portion: | 1.55 mas / a | ||||||||||||||||||||||||||||
| Individual data | |||||||||||||||||||||||||||||
| Names | A; B. | ||||||||||||||||||||||||||||
| Observation data: | |||||||||||||||||||||||||||||
| Apparent brightness | A. | +1.25 mag | |||||||||||||||||||||||||||
| B. | 11.7 mag | ||||||||||||||||||||||||||||
| Typing: | |||||||||||||||||||||||||||||
| Spectral class | A. | A2 Iae | |||||||||||||||||||||||||||
| B − V color index | A. | +0.09 | |||||||||||||||||||||||||||
| U − B color index | A. | −0.23 | |||||||||||||||||||||||||||
| Physical Properties: | |||||||||||||||||||||||||||||
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Absolute vis. Brightness M vis |
A. | -8.73 / -6.93 mag | |||||||||||||||||||||||||||
| B. | +1.9 mag | ||||||||||||||||||||||||||||
| Dimensions | A. | 20 to 25 M ☉ | |||||||||||||||||||||||||||
| B. | |||||||||||||||||||||||||||||
| radius | A. | 100 to 200 R ☉ | |||||||||||||||||||||||||||
| B. | |||||||||||||||||||||||||||||
| Luminosity | A. | 196,000 L ☉ | |||||||||||||||||||||||||||
| B. | |||||||||||||||||||||||||||||
| Effective temperature | A. | 8700 K | |||||||||||||||||||||||||||
| B. | |||||||||||||||||||||||||||||
| Rotation time | A. | 80 d | |||||||||||||||||||||||||||
| B. | |||||||||||||||||||||||||||||
| Other names and catalog entries |
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Deneb is the brightest star (α Cygni) in the constellation Swan . Together with Wega and Altair it forms the summer triangle . With an apparent magnitude of 1.2 mag, the Alpha Cygni star prototype is a luminous blue variable . Deneb is the 19th brightest star in the night sky and, together with Eta Carinae (also LBV star), the brightest known star of our Milky Way in visible light . It is also the most distant first magnitude star. If Deneb had the same distance to the earth as Vega (25 light years ), he would shine almost as bright as the moon in a sickle shape.
Naming
The name Deneb means "tail" and is an abbreviation of the Arabic nameذنب الدجاجة ḏanab al-daǧāǧa 'tail of the hen'. Other names of α Cygni: Arided, Aridif, Arrioph, Deneb el Adige, Gallina.
distance
Deneb's distance can only be specified within a wide range, because with stars that far away, the measurement errors already have a major impact on the result. In the most accurate parallax measurement to date by the Hipparcos satellite , a parallax of 1.0 milli- arcseconds was initially determined (data reduction 1997), which corresponds to a distance of approx. 3200 light years. Due to the high measurement uncertainty , the distance from Deneb would have been between 1600 and 7400 light years. More recent analyzes (second Hipparcos reduction 2007) show values of a little over 1400 light years; According to a 2008 study, the most likely distance is 1550 light years with an uncertainty of less than 20%. Therefore, the other properties of Deneb are also subject to great uncertainties.
Physical Properties
Deneb is a hot supergiant , he is currently in the transition phase from blue giant to red supergiant . So he's just about to turn off the main row to the top right, i.e. H. it becomes redder (the temperature drops), but at the same time more luminous as its diameter increases. With an absolute brightness of −8.5 mag, it is one of the brightest known stars. The radiation power is around 1.2 × 10 32 W, which is around 300,000 times higher than that of the sun. Since the distance could not yet be determined exactly, the values of the brightness fluctuate between 100,000 and 250,000 times the sun's brightness. The star produces more light in a minute than the sun does in a month.
Based on its temperature and luminosity, and the tiny apparent diameter of just under 0.002 arc seconds, the diameter can be determined to be about 200 times that of the sun. If Deneb were in the center of the solar system, its edges would extend at least as far as the orbit of the earth. It is therefore also one of the largest known stars and the most powerful star of the spectral class A that can be observed with the naked eye.
As an A2Ia star, Deneb has a surface temperature of 8700 Kelvin . It is the prototype of a series of variable stars known as Alpha Cygni variables . Its surface vibrates somewhat, which results in small fluctuations in brightness and the change in the spectral type . Its mass is estimated to be 20 to 25 times the solar mass.
Because of its large mass and high temperature, Deneb will not exist in this form for long. As a star about 20 times the mass of the Sun, Deneb ended its main sequence stage (the hydrogen burning phase) about 40,000 years ago as a hot B star.
It could become a supernova in just a few million years . Deneb's stellar winds of ∼240 km s −1 cause a loss of matter of 12.4 × 10 −7 M ☉ / year, corresponding to approx. 78 trillion tons per second.
The main star may be orbited by a faint companion about which little is known. With an apparent magnitude of 11.7 mag, it is only visible with the help of telescopes.
mythology
In the Chinese love story “ cowherd and weaver ” Deneb describes a bridge formed by magpies over the Milky Way, which allows the separated lovers Niulang (Altair) and Zhinü (Wega) to reunite on a special night in late summer. In Japanese culture, there is a festival ( Tanabata ) that grew out of this story . In other versions of this story, Deneb is a fairy who serves as a chaperone when the loved ones meet over this bridge.
See also
Web links
Individual evidence
- ↑ a b c d e f g h alf Cyg. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed on October 31, 2018 .
- ↑ a b c d e f g Olivier Chesneau, et al .: Time, spatial, and spectral resolution of the Halpha line-formation region of Deneb and Rigel with the VEGA / CHARA interferometer . In: Astronomy and Astrophysics (2010) . July 13, 2010. arxiv : 1007.2095v1 . doi : 10.1051 / 0004-6361 / 201014509 .
- ↑ alf Cyg. In: VSX. AAVSO, accessed October 31, 2018 .
- ↑ a b c Deneb ( Memento from December 5, 2012 in the web archive archive.today ) on domeofthesky.com
- ↑ a b Deneb. Jim Kaler, accessed October 31, 2018 .
- ↑ JM Apellániz, E. J Alfaro, A. Sota: Accurate distances to nearby massive stars with the new reduction of the Hipparcos raw data . arxiv : 0804.2553
- ↑ SIMBAD query