70 Ophiuchi

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70 Ophiuchi
Template:Location mark
Location of 70 Ophiuchi in the constellation Ophiuchus
Characteristics
Spectral type K0V + K4V[1]
Apparent magnitude (B) 4.97/7.26[2]
Apparent magnitude (R) 3.6/5.6[2]
U−B Template:Engvar +0.69[3]
B−V Template:Engvar +0.82/+1.15[4]
Variable type BY Dra[5] or RS CVn[6]
Astrometry
70 Oph A
Radial velocity (Rv)Script error: No such module "val".[7] km/s
Proper motion (μ) RA: Script error: No such module "val". mas/yr[7]
Dec.: Script error: No such module "val". mas/yr[7]
Parallax (π)195.5674±0.1964 mas[7]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)+5.627[4]
70 Oph B
Radial velocity (Rv)Script error: No such module "val".[8] km/s
Proper motion (μ) RA: Script error: No such module "val". mas/yr[8]
Dec.: Script error: No such module "val". mas/yr[8]
Parallax (π)195.2166±0.1012 mas[9]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)+7.427[4]
Details
70 Oph A
MassScript error: No such module "val".[4] Template:Solar mass
RadiusScript error: No such module "val".[10] Template:Solar radius
Luminosity (bolometric)Script error: No such module "val".[4] Template:Solar luminosity
Habitable zone inner limit0.623[10] AU
Habitable zone outer limit1.242[10] AU
Surface gravity (log g)4.5[11] cgs
Temperature5,282[4] K
Metallicity [Fe/H]Script error: No such module "val".[12] dex
Rotation19.7[13] days
AgeScript error: No such module "val".[12] Gyr
70 Oph B
MassScript error: No such module "val".[4] Template:Solar mass
RadiusScript error: No such module "val".[10] Template:Solar radius
Luminosity (bolometric)Script error: No such module "val".[12] Template:Solar luminosity
Habitable zone inner limit0.359[10] AU
Habitable zone outer limit0.712[10] AU
Temperature4,623[4] K
Metallicity [Fe/H]Script error: No such module "val".[12] dex
AgeScript error: No such module "val".[12] Gyr
Other designations
Template:Odlist
70 Oph A: Template:Odlist
70 Oph B: Template:Odlist
Database references
SIMBADThe system
A
B
Exoplanet Archivedata
ARICNSdata

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70 Ophiuchi (p Ophiuchi)[14] is a binary star system located 16.7 light-years away from the Earth. It is in the constellation Ophiuchus. At magnitude 4 it appears as a dim star visible to the unaided eye away from city lights.

History

In Ptolemy's 2nd-century Almagest star catalogue this star system is listed as a 4th magnitude star, the 28th (or 4th outside the constellation figure) in Ophiuchus. It is star No. 261 in this catalogue.[15]

This star system was first catalogued as a binary star by William Herschel in the late 18th century in his study of binary stars. Herschel proved that this system is a gravitationally bound binary system where the two stars orbit around a common center of mass. This was an important contribution to the proof that Newton's law of universal gravitation applied to objects beyond the Solar System.

This star was once considered part of the obsolete constellation Taurus Poniatovii, but after the International Astronomical Union officially recognized constellations, it was placed in Ophiuchus.[16]

Variability

File:V2391OphLightCurve.png
A light curve for V2391 Ophiuchi, plotted from Hipparcos data[17]

70 Ophiuchi is a variable star with a magnitude range for the two stars combined of 4.00 to 4.03.[6] The type of variability is uncertain and it is not clear which of the two components causes the variations. It has been suspected of being either a BY Draconis variable[5] or an RS Canum Venaticorum variable, and a period of 1.92396 days has been measured.[6]

Binary star

The primary star is a yellow-orange main sequence dwarf of spectral type K0, while the secondary is an orange dwarf of spectral type K4.[1] The two stars orbit each other at an average distance of 23.2 AU. But since the orbit is highly elliptical (at e=0.499), the separation between the two varies from 11.4 to 34.8 AU,[18] with one orbit taking 88.38 years to complete.[19]

Claims of a planetary system

In 1855, William Stephen Jacob of the Madras Observatory claimed that the orbit of the binary showed an anomaly, and it was "highly probable" that there was a "planetary body in connection with this system".[20] This is the first known attempt to use astrometric methods to detect an exoplanet, although Friedrich Bessel had applied similar methods 10 years earlier to deduce the existence of Sirius B.[21]

T. J. J. See made a stronger claim for the existence of a dark companion in this system in 1899,[22] but Forest Ray Moulton soon published a paper proving that a three-body system with the specified orbital parameters would be highly unstable.[23] The claims by Jacob and See have both been shown to be erroneous.[24]

Discovery of a "third dark companion" was announced by Louis Berman in 1932. This "dark body" around 70 Oph A was thought to have an 18-year period and a mass of 0.1 to 0.2 the Sun's mass.[25] A claim of a planetary system was again made, this time by Dirk Reuyl and Erik Holberg in 1943. The companion was estimated to have a mass 0.008 to 0.012 that of the Sun and a 17-year period.[26] This caused quite a sensation at the time but later observations have gradually discredited this claim.[24][27][28]

The negative results of past studies does not completely rule out the possibility of planets. In 2006 a McDonald Observatory team set limits to the presence of one or more planets around 70 Ophiuchi with masses between 0.46 and 12.8 Jupiter masses and average separations spanning between 0.05 and 5.2 AU.[29]

See also

References

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  1. ↑ a b Script error: No such module "Citation/CS1".
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  3. ↑ Script error: No such module "Citation/CS1".
  4. ↑ a b c d e f g h Script error: No such module "Citation/CS1". 70 Ophiuchi's database entry at VizieR.
  5. ↑ a b Script error: No such module "citation/CS1".
  6. ↑ a b c Script error: No such module "citation/CS1".
  7. ↑ a b c Template:Cite Gaia DR3
  8. ↑ a b Template:Cite Gaia DR3
  9. ↑ Template:Cite DR2
  10. ↑ a b c d e f Script error: No such module "Citation/CS1".
  11. ↑ Script error: No such module "Citation/CS1".
  12. ↑ a b c d e Script error: No such module "Citation/CS1".
  13. ↑ Script error: No such module "Citation/CS1".
  14. ↑ Script error: No such module "Citation/CS1".
  15. ↑ Script error: No such module "citation/CS1".
  16. ↑ Script error: No such module "citation/CS1".
  17. ↑ Script error: No such module "citation/CS1".
  18. ↑ Solstation article giving details of orbital mechanics of the system
  19. ↑ Script error: No such module "Citation/CS1".
  20. ↑ Script error: No such module "Citation/CS1".
  21. ↑ Script error: No such module "citation/CS1".
  22. ↑ Script error: No such module "Citation/CS1".
  23. ↑ Script error: No such module "Citation/CS1".
  24. ↑ a b Script error: No such module "Citation/CS1".
  25. ↑ Script error: No such module "Citation/CS1".
  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".
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External links

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Template:Sky Template:Nearest star systems Template:Stars of Ophiuchus

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