Rho Ophiuchi
  | |
| Observation data Epoch J2000.0 Equinox 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] |
| Astrometry | |
| ρ Oph AB | |
| Radial velocity (Rv) | −14.6±1.5[5] km/s |
| Proper motion (μ) | RA: −5.53 mas/yr[1] Dec.: −21.74 mas/yr[1] |
| Parallax (π) | 7.19±0.13 mas[6] |
| Distance | 451±12 ly (138.2±3.6 pc)[5] |
| Absolute magnitude (MV) | −2.5±0.3[7] |
| Orbit[5] | |
| Primary | ρ Oph Aa |
| Companion | ρ Oph Ab |
| Period (P) | 87.831±0.010 days |
| Semi-major axis (a) | 0.995±0.026 AU |
| Eccentricity (e) | 0.17931±0.00017 |
| Inclination (i) | 71.348±0.020° |
| Longitude of the node (Ω) | 303.385±0.034° |
| Periastron epoch (T) | 60101.11 RJD |
| Argument of periastron (ω) (secondary) | 4.80±0.24° |
| Semi-amplitude (K1) (primary) | 55.5±3.6 km/s |
| Semi-amplitude (K2) (secondary) | 65.7±3.6 km/s |
| Orbit[8] | |
| Primary | ρ Oph A |
| Companion | ρ Oph B |
| Period (P) | 2,398±326 years |
| Semi-major axis (a) | 4.25±0.79″ |
| Eccentricity (e) | 0.675±0.322 |
| Inclination (i) | 135.3±6.0° |
| Longitude of the node (Ω) | 77.5±13.5° |
| Periastron epoch (T) | B 2327±343 |
| Argument of periastron (ω) (secondary) | 226.1±15.3° |
| Orbit[8] | |
| Primary | ρ Oph D |
| Companion | ρ Oph E |
| Period (P) | 675.5±32.5 years |
| Semi-major axis (a) | 1.01±0.15″ |
| Eccentricity (e) | 0.707±0.112 |
| Inclination (i) | 134.8±2.7° |
| Longitude of the node (Ω) | 152.7±4.6° |
| Periastron epoch (T) | B 2008.6±34.2 |
| Argument of periastron (ω) (secondary) | 260.4±1.1° |
| Details[6] | |
| ρ Oph Aa | |
| Mass | 9.21±0.79[5] M☉ |
| Radius | 4.2±0.3 R☉ |
| Luminosity | 4,270+980 −800 L☉ |
| Surface gravity (log g) | 4.25±0.25 cgs |
| Temperature | 23,000±1,000 K |
| Rotation | 1.205[9] days |
| Rotational velocity (v sin i) | 206±5 km/s |
| Age | 15±6 Myr |
| ρ Oph Ab | |
| Mass | 7.79±0.70[5] M☉ |
| Radius | 3.1±0.2 R☉ |
| Luminosity | 1,000+400 −290 L☉ |
| Surface gravity (log g) | 4.25±0.25 cgs |
| Temperature | 19,000±1,000 K |
| Rotational velocity (v sin i) | 227±5 km/s |
| Age | 15±6 Myr |
| ρ Oph B | |
| Mass | 8[10] M☉ |
| ρ Oph C | |
| Mass | 5[10] M☉ |
| ρ Oph D | |
| Mass | 3.06[8] M☉ |
| ρ Oph E | |
| Mass | 1.97[8] M☉ |
| Other designations | |
| ρ Oph, 5 Oph, WDS J16256-2327 | |
| ρ Oph AB: CD−23°12861, HIP 80473 | |
| ρ Oph A: HD 147933, HR 6112, SAO 184382 | |
| ρ Oph B: HD 147934, HR 6113, SAO 184381 | |
| ρ Oph C: CD−23°12862, HIP 80474, SAO 184383 | |
| Database references | |
| SIMBAD | ρ 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, it is located about 450 light-years distant.[5] The other stars in the system are slightly farther away.[11][clarification needed]
System
[edit]
The central system is known as Rho Ophiuchi AB. It consists of three blue-colored subgiants or main-sequence stars, designated Rho Ophiuchi Aa, Ab and B, respectively.[11] Rho Ophiuchi Aa-Ab is a spectroscopic binary with an orbital period of 88 days and an orbital period of 1.1 astronomical units.[6] Farther away is the B companion, a visual binary whose sky-projected distance from the inner pair appears to be 3.1″, corresponding to a separation of at least 344 AU.[11] However, the actual separation is larger, and the two take about 2,400 years to complete an orbit.[8] The two stars dominate the radiation field around the Rho Ophiuchi cloud complex.[9]
Rho Ophiuchi A emits X-rays, and exhibits strong variability in emission over periods of about 1.2 days, corresponding to its rotation period. The X-ray variability is due to the strong magnetic field of the secondary companion, Rho Ophiuchi Ab, whose dipole strength is 4 kG.[6][12]
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.[8]
Cloud complex
[edit]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.[7]
References
[edit]- ^ a b c van Leeuwen, F.; et al. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
- ^ a b Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". VizieR Online Data Catalog. 2237. Bibcode:2002yCat.2237....0D.
- ^ Houk, N.; Smith-Moore, M. (1988). Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume 4, Declinations −26°.0 to −12°.0. Bibcode:1988mcts.book.....H.
- ^ a b Nicolet, B. (1964). "Catalogue of homogeneous data in the UBV photoelectric photometric system". Astronomy and Astrophysics Supplement Series. 34: 1–49. Bibcode:1978A&AS...34....1N.
- ^ a b c d e f Klement, R.; Shultz, M. E.; Rivinius, Th. "Spatially resolved centrifugal magnetosphere caught in motion around the secondary component of ρ Oph A". arXiv:2505.10038.
- ^ a b c d Shultz, M. E.; Berry, I.; Bohlender, D.; Catanzaro, G.; Giarrusso, M.; Klement, R.; Labadie-Bartz, J.; Leone, F.; Leto, P. (2025-05-12). "Discovery of the binary nature of the magnetospheric B-type star ρ Oph A". arXiv:2505.08007.
- ^ a b Wegner, W. (2003). "The total-to-selective extinction ratio determined from near IR photometry of OB stars". Astronomische Nachrichten. 324 (3): 219–237. Bibcode:2003AN....324..219W. doi:10.1002/asna.200310081.
- ^ a b c d e f Novaković, B. (2007). "Orbits of Five Visual Binary Stars". Baltic Astronomy. 16: 435–442. arXiv:0712.4242. Bibcode:2007BaltA..16..435N.
- ^ a b Hubrig, S.; Schöller, M.; Järvinen, S. P.; Küker, M.; Kholtygin, A. F.; Steinbrunner, P. (2018). "Detection of a centrifugal magnetosphere in one of the most massive stars in the ρ Oph star-forming cloud". Astronomische Nachrichten. 339 (1): 72–77. arXiv:1712.05939. Bibcode:2018AN....339...72H. doi:10.1002/asna.201713457. S2CID 119084902.
- ^ a b Allen, Christine; Ruelas-Mayorga, Alex; Sánchez, Leonardo J.; Costero, Rafael (2018). "The dynamical evolution of multiple systems of trapezium type". Monthly Notices of the Royal Astronomical Society. arXiv:1809.03537. doi:10.1093/mnras/sty2502.
- ^ a b c d e f Cordiner, M. A.; Fossey, S. J.; Smith, A. M.; Sarre, P. J. (2013). "Cordiner, M. A., Fossey, S. J., Smith, A. M. and Sarre, P. J. 2013, ApJ, 764, L10". The Astrophysical Journal Letters. 764 (1): L10. arXiv:1301.6167. Bibcode:2013ApJ...764L..10C. doi:10.1088/2041-8205/764/1/L10. S2CID 119204101.
- ^ Pillitteri, Ignazio; Wolk, Scott J.; Reale, Fabio; Oskinova, Lida (2017). "The early B-type star Rho Ophiuchi a is an X-ray lighthouse". Astronomy & Astrophysics. 602: A92. arXiv:1703.04686. Bibcode:2017A&A...602A..92P. doi:10.1051/0004-6361/201630070. S2CID 119431278.
- ^ Wilking, B. A.; Gagné, M.; Allen, L. E. (2008). "Star Formation in the ρ Ophiuchi Molecular Cloud". Handbook of Star Forming Regions. arXiv:0811.0005. Bibcode:2008hsf2.book..351W.
- ^ Shatsky, N.; Tokovinin, A. (2002). "The mass ratio distribution of B-type visual binaries in the Sco OB2 association". Astronomy and Astrophysics. 382: 92–103. arXiv:astro-ph/0109456. Bibcode:2002A&A...382...92S. doi:10.1051/0004-6361:20011542. S2CID 16697655.
