Delta Eridani

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δ Eridani
dates equinoxJ2000.0 , epoch : J2000.0
Constellation Eridanus
Right ascension 03 h 43 m 14.9 s
declination -09 ° 45 ′ 48.2 ″
Apparent brightness 3.52 mag
B − V color index +0.92 
U − B color index +0.69 
R − I index +0.50 
Spectral class K0 IV
Radial velocity (−6.4 ± 0.2) km / s
parallax (110.61 ± 0.22)  mas
distance (29.49 ± 0.06)  Lj
(9.041 ± 0.018)  pc  
Visual absolute brightness M vis approx. +3.7 mag
Proper movement 
Rec. Share: (−93.16 ± 0.29)  mas / a
Dec. portion: (+743.64 ± 0.22)  mas / a
Physical Properties
Dimensions 1.9  M
radius 2.5  R

2.8  L

Effective temperature 9800  K
Rotation time 116 days
Age 7 to 8 billion  a
Other names
and catalog entries
Bayer name δ Eridani
Flamsteed name 23 Eridani
Bonn survey BD −10 ° 728
Bright Star Catalog HR 1136 [1]
Henry Draper Catalog HD 23249 [2]
Hipparcos catalog HIP 17378 [3]
SAO catalog SAO 130686 [4]
Tycho catalog TYC 5303-1320-1 [5]Template: Infobox star / maintenance / specification of the TYC catalog

δ Eridani ( Delta Eridani , δ Eri ) is a star in the constellation Eridanus . Delta Eridani belongs to the spectral class K0 and has an apparent brightness of 3.5 m . It is about 30  light years from the sun .

The star bears the historical proper names Rana ("frog") and Theemini .


Delta Eridani is a sub-giant that is just leaving the main row in the HRD and is thus in the transition from hydrogen burning to helium fusion. The hydrogen fusion shifts from its core to the shells. Delta Eridani is estimated to be 7 to 8 billion years old. It would be almost twice as old as the sun. Its previous classification as a variable of the type RS Canum Venaticorum is probably wrong, but the general classification as a variable star seems to be confirmed. Suspicious for this are some changes in spectrum and radial velocity , which can indicate sunspots and pulsations in its atmosphere. Delta Eridani owns a lithium anomaly. The lithium content determined from its spectrum is only about half as large as the lithium content of our sun. So far this has been justified by the relatively old age.


Planetary companions (gas giants) around Delta Eridani could not yet be detected despite multiple measurements of the radial velocity . A radius of up to 10 AU from the star was examined  . The Habitable Zone is believed to be 1.7 AU from the star.

Individual evidence

  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. calculated from apparent brightness and distance
  1. Wolfram Alpha : Delta Eridani
  2. Rana
  3. Murdoch, KA, Hearnshaw, JB, Clark, M .: A search for substellar companions to southern solar-type stars. In: Astrophysical Journal. Part 1, vol. 413, no. 1, pp. 349-363.
  4. Conti, PS: The presence of lithium in delta Eridani. In: The Observatory. Vol. 84, pp. 122-123.

Web links