HD 184738
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 19h 34m 45.2338s[2] |
| Declination | +30° 30′ 58.951″[2] |
| Apparent magnitude (V) | 10.41[2] |
| Characteristics | |
| Spectral type | [WC9][3] |
| Astrometry | |
| Radial velocity (Rv) | −30.4[2] km/s |
| Proper motion (μ) | RA: −2.241 mas/yr Dec.: −8.844[2] mas/yr |
| Parallax (π) | 0.5863±0.0633 mas[2] |
| Distance | c.3,900 ly (c.1,200[3][4] pc) |
| Absolute magnitude (MV) | −1.5 |
| Details | |
| Mass | 0.6[3] M☉ |
| Radius | 0.85 R☉ |
| Luminosity | 6,000 L☉ |
| Temperature | 55,000[3] K |
| Other designations | |
| Campbell's star, BD+30°3639, HD 184738, HIP 96295, PK 064+05 1, Henize 2-438[2] | |
| Database references | |
| SIMBAD | data |
HD 184738, also known as Campbell's Hydrogen Star, Campbell's Hydrogen Envelope Star, or simply Campbell's Star, is a variable Wolf–Rayet star in the constellation of Cygnus. It is the central star of the planetary nebula PK 064+05 1. It is also catalogued as BD+30°3639 and HIP 96295.[2] The star is named after the American astronomer William Wallace Campbell, who discovered it in 1893.[5][6]
Location
[edit]Campbell's Hydrogen Star lies about 2.5° north of Albireo (β Cygni) and 1° east of φ Cygni. Its distance from the Solar System is estimated at roughly 1,200 parsecs (3,900 ly).[3][4]
Characteristics
[edit]With an apparent magnitude of +10.41, Campbell's Hydrogen Star is too faint to be seen with the naked eye.[2] It is a carbon-rich Wolf–Rayet-type star with a spectral type of [WC9]. The square brackets mark it as the central star of a planetary nebula rather than a massive Population I Wolf–Rayet star. It is extremely hot, with an effective temperature of about 55,000 K, and is about 6,000 times as luminous as the Sun.[3]
The star is deficient in hydrogen and is in an advanced stage of stellar evolution. Its current mass is about 60% of the Sun's. It is thought to have descended from a progenitor of about 2 solar masses that has passed through the asymptotic giant branch phase. It will ultimately become a white dwarf.[3]
Its chemical composition differs markedly from that of the Sun. It is deficient in iron (Fe/O ≈ 0.3) but has high abundances of carbon and neon, with a C/O ratio of about 30.[4]
Planetary nebula
[edit]The Hubble Space Telescope imaged the star and its surrounding planetary nebula (PK 064+05 1) in 2013.[1][7] The nebula emits strongly in infrared wavelengths.[7] It has an apparent diameter of about 0.13 arcminutes (roughly 8 arcseconds).[2] Its age is estimated at about 700 to 800 years.[3][4]
The dust around other late-type WC stars consists mainly of amorphous carbon. This nebula instead contains crystalline silicate dust, which points to a recent shift from oxygen-dominated chemistry to carbon-dominated chemistry.[3] One proposal is that a stellar companion could explain both the composition of the nebula's dust and the hydrogen deficiency of the central star.[3][4]
References
[edit]- 1 2 "A giant, smouldering star". ESA/Hubble Picture of the Week. Retrieved 17 September 2013.
- 1 2 3 4 5 6 7 8 9 10 "HD 184738 – Planetary Nebula". SIMBAD. Centre de données astronomiques de Strasbourg.
- 1 2 3 4 5 6 7 8 9 10 Crowther, Paul A.; Morris, P. W.; Smith, J. D. (2006). "An Ultraviolet to Mid-Infrared Study of the Physical and Wind Properties of HD 164270 (WC9) and Comparison to BD +30 3639 ([WC9])". The Astrophysical Journal. 636 (2): 1033–1044. Bibcode:2006ApJ...636.1033C.
- 1 2 3 4 5 Yu, Young Sam; Nordon, Raanan; Kastner, Joel H.; Houck, John; Behar, Ehud; Soker, Noam (2009). "The X-Ray Spectrum of a Planetary Nebula at High Resolution: Chandra Gratings Spectroscopy of BD +30°3639". The Astrophysical Journal. 690 (1): 440–452. Bibcode:2009ApJ...690..440Y.
- ↑ Campbell, W. W. (1894). "The Wolf-Rayet stars". Astronomy and Astro-Physics. 13: 448–476 (specifically p. 461). Bibcode:1894AstAp..13..448C.
- ↑ Swings, P.; Struve, O. (1940). "HD 167362, an object similar to Campbell's hydrogen envelope star" (PDF). Proc Natl Acad Sci USA. 26 (7): 454–458. Bibcode:1940PNAS...26..454S. doi:10.1073/pnas.26.7.454. PMC 1078208. PMID 16588382.
- 1 2 Hille, Karl (20 September 2013). "Hubble Eyes a Smoldering Star". NASA. Retrieved 30 August 2019.