40 Eridani

From Wikipedia, the free encyclopedia
(Redirected from HD 26965)
Jump to navigation Jump to search

Template:Short description Template:Other stars by Bayer designation

Template:Starbox visbin

40 Eridani / Keid
Template:Location mark
Location of 40 Eridani (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Eridanus[1]
40 Eridani A
Right ascension Template:RA[2]
Declination Template:DEC[2]
Apparent magnitude (V) 4.43[3]
40 Eridani B
Right ascension Template:RA[4]
Declination Template:DEC[4]
Apparent magnitude (V) 9.52[5]
40 Eridani C
Right ascension Template:RA[6]
Declination Template:DEC[6]
Apparent magnitude (V) 11.17[5]
Characteristics
40 Eridani A
Evolutionary stage main sequence[2]
Spectral type K0.5V[7]
U−B Template:Engvar +0.45[5]
B−V Template:Engvar +0.82[3]
40 Eridani B
Evolutionary stage white dwarf[8]
Spectral type DA4[5]
U−B Template:Engvar +0.45[5]
B−V Template:Engvar +0.03[5]
40 Eridani C
Evolutionary stage main sequence[9]
Spectral type M4.5eV[10]
U−B Template:Engvar +0.83[5]
B−V Template:Engvar +1.67[5]
Variable type Flare star[11]
Astrometry
40 Eridani A
Radial velocity (Rv)Script error: No such module "val".[2] km/s
Proper motion (μ) RA: −2,240.085 mas/yr[2]
Dec.: −3,421.809 mas/yr[2]
Parallax (π)199.6080±0.1208 mas[2]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)5.93[12]
40 Eridani B
Radial velocity (Rv)−21[13] km/s
Proper motion (μ) RA: −2,236.169 mas/yr[4]
Dec.: −3,338.955 mas/yr[4]
Parallax (π)199.6911±0.0512 mas[4]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
40 Eridani C
Radial velocity (Rv)Script error: No such module "val".[6] km/s
Proper motion (μ) RA: −2,247.183 mas/yr[6]
Dec.: −3,409.824 mas/yr[6]
Parallax (π)199.4516±0.0692 mas[6]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Orbit[9]
Primary40 Eridani B
Companion40 Eridani C
Period (P)Script error: No such module "val". yr
Semi-major axis (a)Script error: No such module "val"."
(~35 AU)
Eccentricity (e)Script error: No such module "val".
Inclination (i)Script error: No such module "val".°
Longitude of the node (Ω)Script error: No such module "val".°
Periastron epoch (T)Script error: No such module "val".
Argument of periastron (ω)
(secondary)		Script error: No such module "val".°
Details
40 Eridani A
MassScript error: No such module "val".[14] Template:Solar mass
RadiusScript error: No such module "val".[15] Template:Solar radius
LuminosityScript error: No such module "val".[15] Template:Solar luminosity
Surface gravity (log g)Script error: No such module "val".[15] cgs
TemperatureScript error: No such module "val".[15] K
Metallicity [Fe/H]Script error: No such module "val".[15] dex
Rotation~37–43[16] days
Rotational velocity (v sin i)1.23 ± 0.28[16] km/s
AgeScript error: No such module "val".[14] Gyr
Metallicity [Fe/H]{{{metal_fe2}}} dex
40 Eridani B
MassScript error: No such module "val".[8] Template:Solar mass
RadiusScript error: No such module "val".[8] Template:Solar radius
LuminosityScript error: No such module "val".[8] Template:Solar luminosity
Surface gravity (log g)Script error: No such module "val".[8] cgs
TemperatureScript error: No such module "val".[8] K
Age1.8[8] Gyr
40 Eridani C
MassScript error: No such module "val".[9] Template:Solar mass
RadiusScript error: No such module "val".[17] Template:Solar radius
LuminosityScript error: No such module "val".[18] Template:Solar luminosity
Surface gravity (log g)~5.5[18] cgs
TemperatureScript error: No such module "val".[17] K
Metallicity [Fe/H]{{{metal_fe2}}} dex
RotationScript error: No such module "val".[19] days
Other designations
Template:Odlist
A: Template:Odlist
B: Template:Odlist
C: Template:Odlist
Database references
SIMBADA
B
C
Exoplanet Archivedata

Script error: No such module "Check for unknown parameters".

40 Eridani is a triple star system in the constellation of Eridanus, abbreviated 40 Eri. It has the Bayer designation Omicron2 Eridani, which is Latinized from ο2 Eridani and abbreviated Omicron2 Eri or ο2 Eri. Based on parallax measurements taken by the Gaia mission, it is about 16.3 light-years from the Sun.

The primary star of the system, designated 40 Eridani A and named Keid,[20] is easily visible to the naked eye. It is orbited by a binary pair whose two components are designated 40 Eridani B and C, and which were discovered on January 31, 1783, by William Herschel.[21]Template:Rp It was again observed by Friedrich Struve in 1825 and by Otto Struve in 1851.[22][23]

In 1910, it was discovered that although component B was a faint star, it was white in color. This meant that it had to be a small star; in fact it was a white dwarf, the first discovered.[24] Although it is neither the closest white dwarf, nor the brightest in the night sky, it is by far the easiest to observe; it is nearly three magnitudes brighter than Van Maanen's Star, the nearest solitary white dwarf, and unlike the companions of Procyon and Sirius it is not outshone by the glare of a much brighter primary.[25]

Nomenclature

40 Eridani is the system's Flamsteed designation and ο2 Eridani (Latinised to Omicron2 Eridani) its Bayer designation. The designations of the sub-components – 40 Eridani A, B and C – derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[26] 40 Eridani C also bears the variable star designation DY Eridani.

The system bore the traditional name Keid derived from the Arabic word قيض (Script error: No such module "lang".) meaning "the eggshells", alluding to its neighbour Beid (Arabic "egg").[27] In 2016, the IAU organized a Working Group on Star Names (WGSN)[28] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[29] It approved the name Keid for the component 40 Eridani A on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.[20]

Properties

File:40 Eridani.png
Amateur photo of 40 Eridani

40 Eridani A is a main-sequence dwarf of spectral type K1, 40 Eridani B is a 9th magnitude white dwarf of spectral type DA4, and 40 Eridani C is an 11th magnitude red dwarf flare star of spectral type M4.5e. When component B was a main-sequence star, it is thought to have been the most massive member of the system at Script error: No such module "val"., but ejected much of its mass before it became a white dwarf.[8] B and C orbit each other approximately 400 AU from the primary star, A.[30] Their orbit has a semimajor axis of 35 AU and is rather elliptical with an orbital eccentricity of 0.410.[22]

As seen from the 40 Eridani system, the Sun is a 3.4-magnitude star in Hercules, near the border with Serpens Caput.[note 1]

Potential for life

The habitable zone of 40 Eridani A, where a planet could exist with liquid water, is near 0.68 [[astronomical unit|Template:Sc]] from A. At this distance a planet would complete a revolution in 223 Earth days (according to the third of Kepler's laws) and 40 Eridani A would appear nearly 20%[note 2] wider than the Sun does on Earth. An observer on a planet in the 40 Eridani A system would see the B-C pair as unusually bright white and reddish-orange stars in the night sky – magnitudes −8 and −6, slightly brighter than the appearance of Venus seen from Earth as the evening star.

It is unlikely that habitable planets exist around 40 Eridani B because they would have been sterilized by its evolution into a white dwarf. As for 40 Eridani C, it is prone to flares, which cause large momentary increases in the emission of X-rays as well as visible light. This would be lethal to Earth-type life on planets near the flare star.[30]

Search for planets

40 Eridani A shows periodic radial velocity variations, which were suggested to be caused by a planetary companion. The 42-day period is close to the stellar rotation period, which made the possible planetary nature of the signal difficult to confirm.[16] A 2018 study found that most evidence supports a planetary origin for the signal,[14] but this was controversial, with a 2021 study characterizing the signal as a false positive,[31] and a 2022 study getting inconclusive results.[32] Further studies in 2023[33]Template:Rp and 2024 concluded that the radial velocity signal very likely does originate from stellar activity, and not from a planet.[34]

The candidate planet would have had a minimum mass of Script error: No such module "val"., and lie considerably interior to the habitable zone, receiving nine times more stellar flux than Earth, which is an even greater amount than Mercury, the innermost planet in the Solar System, on average receives from the Sun.[14]

In fiction

In the Star Trek franchise, the planet Vulcan orbits 40 Eridani A.[35] Vulcan has been referenced in relation to the real-life search for exoplanets in this system.[36][34] The hypothetical planet 40 Eridani A b is also mentioned in the book Project Hail Mary as the home of the eponymous Eridian species.[37] In the Bobiverse series by Dennis E. Taylor, a double planet is found orbiting 40 Eridani A,[38] and named Vulcan and Romulus by an uploaded intelligence in a von Neumann probe.

Notes

<templatestyles src="Reflist/styles.css" />

  1. ↑ From 40 Eridani the Sun would appear on the diametrically opposite side of the sky at the coordinates RA=Template:RA, Dec=Template:DEC, which is located near the border of Hercules (constellation) and Serpens Caput, the closest bright star being Alpha Serpentis. The absolute magnitude of the Sun is 4.85, so, at a distance of 5.04 parsecs, the Sun would have an apparent magnitude m = Mv + 5⋅((log10 5.04) − 1) = 3.36.
  2. ↑ From  h= a d, where Template:Mvar is the apparent height, Template:Mvar is the distance of the object, and Template:Mvar is the actual size of the object.

Script error: No such module "Check for unknown parameters".

See also

References

<templatestyles src="Reflist/styles.css" />

  1. ↑ Script error: No such module "Citation/CS1".
  2. ↑ a b c d e f Template:Cite Gaia DR3
  3. ↑ a b Script error: No such module "Citation/CS1".
  4. ↑ a b c d Template:Cite Gaia DR3
  5. ↑ a b c d e f g h Gliese Catalogue of Nearby Stars, preliminary 3rd ed., 1991. CDS ID V/70A.
  6. ↑ a b c d e Template:Cite Gaia DR3
  7. ↑ Script error: No such module "Citation/CS1".
  8. ↑ a b c d e f g h Script error: No such module "Citation/CS1".
  9. ↑ a b c Script error: No such module "Citation/CS1".
  10. ↑ General Catalogue of Trigonometric Parallaxes, 4th ed., 1995. CDS ID I/238A.
  11. ↑ Script error: No such module "Citation/CS1".
  12. ↑ Script error: No such module "Citation/CS1".
  13. ↑ Script error: No such module "Citation/CS1".
  14. ↑ a b c d Script error: No such module "Citation/CS1".
  15. ↑ a b c d e Script error: No such module "Citation/CS1".
  16. ↑ a b c Script error: No such module "Citation/CS1".
  17. ↑ a b Script error: No such module "Citation/CS1".
  18. ↑ a b Script error: No such module "Citation/CS1".
  19. ↑ Script error: No such module "Citation/CS1".
  20. ↑ a b Script error: No such module "citation/CS1".
  21. ↑ Script error: No such module "Citation/CS1".
  22. ↑ a b Script error: No such module "Citation/CS1".
  23. ↑ Script error: No such module "Citation/CS1".
  24. ↑ White Dwarfs, E. Schatzman, Amsterdam: North-Holland, 1958. , p. 1
  25. ↑ Keid Template:Webarchive, Jim Kaler, STARS web page, accessed 15/5/2007, 10/12/2011.
  26. ↑ Script error: No such module "citation/CS1".
  27. ↑ Script error: No such module "citation/CS1".
  28. ↑ Script error: No such module "citation/CS1".
  29. ↑ Script error: No such module "citation/CS1".
  30. ↑ a b Script error: No such module "citation/CS1".
  31. ↑ Script error: No such module "Citation/CS1".
  32. ↑ Script error: No such module "Citation/CS1".
  33. ↑ Script error: No such module "Citation/CS1".
  34. ↑ a b Script error: No such module "Citation/CS1".
  35. ↑ Script error: No such module "citation/CS1".
  36. ↑ Script error: No such module "citation/CS1".
  37. ↑ Script error: No such module "citation/CS1".
  38. ↑ Script error: No such module "citation/CS1".

Script error: No such module "Check for unknown parameters".

External links

Template:Sky Template:Nearest systems Template:Stars of Eridanus Template:Portal bar

Retrieved from "http://debianws.lexgopc.com/wiki143/index.php?title=40_Eridani&oldid=4804897"