Epsilon Aquilae

from Wikipedia, the free encyclopedia
Star
ε Aquilae
(Deneb el Okab Borealis)
Aquila constellation
Aquila constellation
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation Eagle
Right ascension 18 h 59 m 37.36 s
declination + 15 ° 04 ′ 5.9 ″
Apparent brightness 4.02 mag
Typing
B − V color index +1.08 
U − B color index +1.04 
R − I index +0.52 
Spectral class K2 III
Astrometry
Radial velocity (−45.9 ± 0.4) km / s
parallax (21.05 ± 0.70)  mas
distance (154.9 ± 5.2)  ly
(47.5 ± 1.6)  pc  
Visual absolute brightness M vis approx. +0.6 mag
Proper movement 
Rec. Share: (−50.75 ± 0.90)  mas / a
Dec. portion: (−72.36 ± 0.61)  mas / a
Physical Properties
Dimensions 2.5  M ☉
radius 10 to 12  R ☉
Luminosity

66  L ☉

Effective temperature 4700  K
Other names
and catalog entries
Bayer name ε Aquilae
Flamsteed name 13 Aquilae
Bonn survey BD + 14 ° 3736
Bright Star Catalog HR 7176 [1]
Henry Draper Catalog HD 176411 [2]
Hipparcos catalog HIP 93244 [3]
SAO catalog SAO 104318 [4]
Tycho catalog TYC 1585-2531-1 [5]Template: Infobox star / maintenance / specification of the TYC catalog
Other names FK5 712

ε Aquilae ( Epsilon Aquilae , short ε Aql ) is a star in the constellation of eagle . Epsilon Aquilae is a red giant of the spectral class K1 and has an apparent magnitude of 4.0 mag. Its distance is about 155  light years . It is a so-called barium star , which means that its atmosphere is enriched with barium and other heavy elements above average . Such stars are formed when they soak up that matter that is repelled by a close companion in the course of its development, while this companion ends up as a white dwarf .

In fact, Epsilon Aquilae is a multiple star . At a distance of only about 3.5  AU , a companion of an unknown type should orbit it in 1270 days. In addition, Epsilon Aquilae could have two other companions. One component is a faint star with an apparent magnitude of +10.2 mag and is 148.6 arc seconds or about 3700 AU away from the central star. The second (possible) companion, which is 10.1 mag bright, has two different information (66 or 131 arc seconds) about its distance to the main star. However, these two faint components are perhaps only optical double stars.

Epsilon Aquilae bears the historical proper name Deneb el Okab Borealis and was thus distinguished from the star Zeta Aquilae , which bears the historical proper name Deneb el Okab Australis . The two stars together form the tail feathers of the eagle, therefore they were collectively called "Deneb el Okab" ( Arabic ذنب العقاب, DMG ḏanab al-ʿuqāb  'tail of the eagle'). Because Epsilon Aquilae is the more northerly of the two stars, the addition Borealis (Latin boreas = "north") is added to it.

Web links

Remarks

  1. ↑ a b c Hipparcos catalog (ESA 1997)
  2. ↑ a b c Bright Star Catalog
  3. ↑ Pulkovo radial velocities for 35493 HIP stars
  4. ↑ a b c Hipparcos, the New Reduction (van Leeuwen, 2007)
  5. ↑ Deneb el Okab Borealis by Jim Kaler