Epsilon Eridani

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Star
ε Eridani
Position of Epsilon Eridani (red circle)
Position of Epsilon Eridani (red circle)
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation Eridanus
Right ascension 03 h 32 m 55.85 s
declination -09 ° 27 ′ 29.7 ″
Apparent brightness 3.73 (3.68 to 3.78) mag
Typing
Known exoplanets 1
B − V color index +0.88 
U − B color index +0.59 
R − I index +0.47 
Spectral class K2 V
Variable star type BY 
Astrometry
Radial velocity (16.43 ± 0.09) km / s
parallax (310.94 ± 0.16)  mas
distance (10.489 ± 0.005)  Lj
(3.216 ± 0.002)  pc
Visual absolute brightness M vis +6.18 mag
Proper movement 
Rec. Share: (−975.17 ± 0.21)  mas / a
Dec. portion: (19.49 ± 0.20)  mas / a
Physical Properties
Dimensions (0.847 ± 0.042)  M ☉
radius (0.702 ± 0.035)  R ☉
Luminosity

0.28  L ☉

Effective temperature 5100  K
Metallicity [Fe / H] (−0.13 ± 0.04)
Rotation time 11.1 days
Age approx. 800 · 10 6  a
Other names
and catalog entries
Bayer name ε Eridani
Flamsteed name 18 Eridani
Bonn survey BD -9 ° 697
Bright Star Catalog HR 1084 [1]
Henry Draper Catalog HD 22049 [2]
Gliese catalog FY 144 [3]
Hipparcos catalog HIP 16537 [4]
SAO catalog SAO 130564 [5]
Tycho catalog TYC 5296-1533-1 [6]
2MASS catalog 2MASS J03325591-0927298 [7]
Other names Ran • FK5 127 • LHS 1557 • WDS 03330-0928
annotation
  1. ↑ Calculated from apparent brightness and distance.

Epsilon Eridani (also: Ran ) is a sun-like star with about 0.85 solar masses and a distance of about 10.5 light years from our solar system .

It is the third closest star to the naked eye after Alpha Centauri and Sirius .

Epsilon Eridani belongs to the constellation Eridanus and is the closest star of this constellation from a distance. Its closest neighbor is at a distance of 5.22 ly (1.60 pc) Luyten 726-8 ( UV Ceti and BL Ceti).

Names

For a long time, Epsilon Eridani had no proper name alongside his Bayer name. After a public IAU competition, it was given the name Ran in December 2015 .

Arab settlers along the east coast of Africa occasionally gave the star the name الصادرة Aṣ-Ṣādira ("the returning ostriches ") almost 700 years ago .

Physical Properties

Epsilon Eridani (left) is smaller and cooler than the sun (right).

With an age of half a billion years to a billion years, it is a relatively young star compared to the 4.6 billion year old sun . Epsilon Eridani is about the same size as the sun, but the brightness of the K2 main sequence star is only 28% of the brightness of the sun. The most unusual property of this star is its extremely changeable optical spectrum , which has many spectral lines (emission lines). It also has a very strong magnetic field and relatively low metallicity (especially with iron). Measurements made it possible to determine the duration of its rotation over 12 days, which corresponds to about twice the rotation speed of the sun; this is due to his young age.

Surroundings of the star

Dust disc

Disk of dust around Epsilon Eridani as seen by the James Clerk Maxwell Telescope

In 1998 a gas and dust disk was found around Epsilon Eridani , which has not yet dissolved due to its young age. Their distance to the star corresponds roughly to that of the Kuiper belt in the solar system. The dust disk contains about 1000 times more dust than is currently in the inner solar system. This would mean that the region around Epsilon Eridani contains a thousand times more cometary material than our solar system. Space is emptied of dust within 35 astronomical units around the star.

Bruce Campbell and other astronomers interpreted Doppler measurements in the dust disk as clumps that may have been caused by resonances. These could indicate a planet orbiting the star.

Today there are no longer any doubts about the theory of planet formation from such gas and dust disks, but this was the first time that astronomers were actually able to observe such conditions in a star.

Asteroid belt

In October 2008, with the help of the Spitzer infrared space telescope, it was possible to prove that Epsilon Eridani has two asteroid belts. The position of one belt is comparable to the position of the asteroid belt in the solar system between Mars and Jupiter. The second, denser belt is between the first belt and the outer ring of the comet.

Planetary system

Size comparison: dust disk and planetary orbit by Epsilon Eridani b.

→ Main article Epsilon Eridani b

Since Epsilon Eridani is one of the closest of the sun-like stars, the search for orbiting planets has long been intense. However, the strong activity and variability of the star meant that it was difficult to find using radial velocity methods . As early as the early 1990s, the existence of a satellite was assumed by a Canadian team led by Bruce Campbell and Gordon Walker. However, their observations were not sufficiently sound to prove its existence.

In 2000, the discovery of the planet Epsilon Eridani b was finally announced by a team led by Artie Hatzes . The discoverers determined its mass as 1.2 ± 0.33 times the mass of the planet Jupiter . Observations from the Hubble Space Telescope confirmed the existence of the exoplanet in early October 2006.

A hypothetical planet named Epsilon Eridani c was proposed in 2002 based on the analysis of the structure of the dust disk. The lumps in the dust disk can be dust particles that are compressed and bound in orbital resonances of a planet with high eccentricity. This planet is said to have a lower mass and orbiting Epsilon Eridani in 280 years with an eccentricity of 0.3 with a major semi-axis of 40 AU distance. The proposed planet is now considered refuted.

Planets from Epsilon Eridani
Planet
(order
from the star) 		Discovered Mass
( M J ) 		Radius
( R J ) 		Major semiaxis of
the railway
( AU ) 		Rotation time
( days ) 		eccentricity Orbit inclination
( degree )
b 2000 1.55 ± 0.24 - 3.39 ± 0.36 2502 ± 10 0.70 ± 0.04 89.0 ± 1.0

SETI project in the 1960s

In 1960 Epsilon Eridani and the star Tau Ceti were observed for several weeks for radio signals as part of the Ozma project, a SETI project, under the direction of Frank Drake . The project was unsuccessful.

Epsilon Eridani in science fiction

Because the star is a relatively close Sun-like star, it appears regularly in science fiction .

  • The science fiction novel Chasm City by Alastair Reynolds takes place on a fictional planet orbiting the star Epsilon Eridani.
  • In the TV series Babylon 5 , the space station of the same name orbits the third planet of Epsilon Eridani.
  • The fictional planet "Reach" in the orbit of Epsilon Eridani is a training center for the Spartans of the Halo game series .
  • In Isaac Asimov's Robot and Foundation cycle , Epsilon Eridani is the sun of the fictional planet Bayley's World , later renamed Comporellon and used as the setting in several of the series' novels.
  • In David Weber's Honor Harrington cycle, there is an "Epsilon Eridani Edict", a prohibition on the use of RKVs ( Relativistic Kill Vehicles ) or asteroids for planetary bombardment. The said "Epsilon Eridani massacre" is named as an example.
  • In the computer games Frontier and Frontier: First Encounters , Epsilon Eridani is described as a system with a planet made Earth-like by terraforming , on which tourism in particular has established itself.
  • Stranded by the sun Epsilon , in 1964 by Jiří Brabenec and Zdeněk Veselý , tells the story of a space crew who stranded on an Earth-like planet near the sun Epsilon, struggled for survival and tried everything possible to warn the follow-up expedition of the dangers of the landing approach. Quote: "Everyone agreed that the planet was baptized with the name Tertia ..."
  • The cartoon character Karl Gabel by the Berlin illustrator Erich Schmitt visits the sun Epsilon Eridani with his twin-hull spaceship. There he finds evacuees from the former fifth planet of the sun, Aloa.
  • In the book Strangers from Heaven by the author Margret Wonder Bonano from the Star Trek series of novels - The Beginnings , Epsilon Eridani is mentioned as the sun of the planet Vulcano.
  • In the novella world destroyer of Liu Cixin the population sends to warn a crystal to Earth to humanity before the world destroyer of planets of the solar system Epsilon Eridani.
  • Ravensburger-Taschenbuch Volume 562 "Flight into the world of tomorrow" by Ludek Pesek (Epsilon Eridani page 66 / Otto Maier Verlag Ravensburg 1979, Georg Bitter Verlag Recklinghausen licensed edition 1975 ISBN 3-473-39562-5 ).
  • In the novel, I am many of Dennis E. Taylor is Epsilon Eridani, the first attended by Bob system.
  • In the television series Space 2063 , the first extrasolar colony of mankind is on the moon Vesta, which orbits Epsilon Eridani B.

Web links

Commons : Epsilon Eridani  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c eps Eri. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed on November 1, 2018 .
  2. ↑ a b c eps Eri. In: VSX. AAVSO , accessed November 1, 2018 .
  3. ↑ a b c Bright Star Catalog
  4. ^ A b Hipparcos, the New Reduction (van Leeuwen, 2007)
  5. ↑ a b P. E. Kervella, F. Arenou, F. Mignard, F. Thévenin: Stellar and substellar companions of nearby stars from Gaia DR2. Binarity from proper motion anomaly . In: Astronomy & Astrophysics . 623, p. A72. arxiv : 1811.08902 . bibcode : 2019A & A ... 623A..72K . doi : 10.1051 / 0004-6361 / 201834371 .
  6. ↑ a b c d eps Eri b. In: Extrasolar Planets Encyclopaedia . Retrieved November 1, 2018 .
  7. ↑ Stefan Deiters: Two asteroid belts around Epsilon Eridani. Astronews, 2008, accessed on October 28, 2008 (German).
  8. ^ Artie Hatzes et al .: Evidence for a Long-period Planet Orbiting Epsilon Eridani . In: ApJ. Letters . 544, 2000, p. L145.
  9. ^ Fritz Benedict et al .: The Extrasolar Planet ε Eridani b: Orbit and Mass . In: The Astronomical Journal . 132, No. 5, 2006, pp. 2206-2218. bibcode : 2006AJ .... 132.2206B . Retrieved November 16, 2008.
  10. ↑ Alice C. Quillen and Stephen Thorndike: Structure in the Epsilon Eridani dusty disk caused by mean motion resonances with a 0.3 eccentricity planet at periastron . In: Cornell University . 2002. arxiv : astro-ph / 0208279 .
  11. ↑ Quillen & Thorndike: Small Planet Spotted About Epsilon Eridani . In: Space Daily , October 25, 2002. Retrieved June 20, 2007. 
  12. ↑ http://exoplanet.eu/catalog/eps%20Eridani_c/
  13. ↑ eps Eri. In: NASA Exoplanet Archive . Retrieved November 1, 2018 .