Rho Ophiuchi

Source: Wikipedia, the free encyclopedia.
This article is about the star. For the dark cloud star forming region, see Rho Ophiuchi cloud complex.
ρ Ophiuchi
Location of ρ Ophiuchi (circled red)
Observation data
J2000.0
Constellation Ophiuchus
Right ascension 16h 25m 35.11766s[1]
Declination −23° 26′ 49.8150″[1]
Apparent magnitude (V) 4.63[2]
Characteristics
ρ Oph AB
Spectral type B2/3V + B2V[3]
U−B color index -0.56[4]
B−V color index +0.24[4]
Distance
360 ± 40 ly
(110 ± 10 pc)
Absolute magnitude (MV)-2.5 ± 0.3[6]
Argument of periastron
(ω)
(secondary)		226.1 ± 15.3°
Argument of periastron
(ω)
(secondary)		260.4 ± 1.1°
Details
ρ Oph A
Rotational velocity (v sin i)
240 ± 10[9] km/s
ρ Oph B
Mass8[10] M☉
ρ Oph C
Mass5[10] M☉
ρ Oph D
Mass3.06[7] M☉
ρ Oph E
Mass1.97[7] M☉
HIP 80474, SAO
 184383
Database references
SIMBADρ Oph
ρ Oph A
ρ Oph B
ρ Oph C
ρ Oph D/E

Rho Ophiuchi (ρ Ophiuchi) is a multiple star system in the constellation Ophiuchus. The central system has an apparent magnitude of 4.63.[2] Based on the central system's parallax of 9.03 mas,[1] it is located about 360 light-years (110 parsecs) away.[1] The other stars in the system are slightly farther away.[11]

System

Rho Ophiuchi cloud complex (N is up): Antares is the bright star that looks yellow in this image, σ Scorpii is in the red nebula (Sh2-9), and the globular cluster M4 is in between. Rho Ophiuchi is the small group of stars in the blue nebulosity (IC 4604).

The central pair is known as Rho Ophiuchi AB. It consists of at least two blue-colored

main-sequence stars, designated Rho Ophiuchi A and B, respectively.[11] Rho Ophiuchi AB is a visual binary, and the sky-projected distance between the two stars appears to be 3.1″, corresponding to a separation of at least 344 astronomical units (au).[11] However, the actual separation is larger, and the two take about 2,400 years to complete an orbit.[7] The two stars dominate the radiation field around the Rho Ophiuchi cloud complex.[9]

Rho Ophiuchi A emits

rotation period. The exact origin of its X-ray variability is unknown: it could be an magnetically active spot on its surface, or it could be a small low-mass companion.[12] Related to this is its extremely strong magnetic field; its dipole strength is at least Bd = 1.9 ± 0.2 kG.[9]

Several other stars are located close to Rho Ophiuchi AB. HD 147932 is located 2.5 arcminutes away (at least 17,000 au), and is known as Rho Ophiuchi C.[11] HD 147888 is located 2.82 arcminutes away (at least 19,000 au), and is known as Rho Ophiuchi DE.[11] Stars C and D are both B-type main-sequence stars,[11] and D itself is another binary with an orbital period of around 680 years.[7]

Cloud complex

Main article: Rho Ophiuchi cloud complex

Rho Ophiuchi is the namesake of the Rho Ophiuchi cloud complex. It is a nebula of gas and dust, which the Rho Ophiuchi system is embedded in. It is one of the easiest star forming regions to observe, as it is one of the nearest, and it is visible from both hemispheres.[13]

The interstellar extinction (AV) of Rho Ophiuchi is measured to be 1.45 magnitudes, meaning the dust and gas in front of Rho Ophiuchi absorbs light from the system, making it appear 1.45 magnitudes dimmer than it would be if there were no dust or gas.[14] Additionally, gas and dust also scatters more higher-frequency light, leaving the light appearing more reddish. The interstellar reddening (EB−V) of Rho Ophiuchi has been measured to be 0.47 magnitudes.[6]

References

  1. ^
    S2CID 18759600
    .
  2. ^
    Bibcode:2002yCat.2237....0D
    .
  3. Bibcode:1988mcts.book.....H
    .
  4. ^
    Bibcode:1978A&AS...34....1N
    .
  5. S2CID 119231169
    .
  6. ^
    doi:10.1002/asna.200310081
    .
  7. ^
    Bibcode:2007BaltA..16..435N
    .
  8. ^
    S2CID 17672346
    .
  9. ^
    S2CID 119084902
    .
  10. ^
    doi:10.1093/mnras/sty2502
    .
  11. ^
    S2CID 119204101
    .
  12. S2CID 119431278
    .
  13. Bibcode:2008hsf2.book..351W
    .
  14. S2CID 16697655
    .
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