BETA ZEN
Humason 2-1
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| Emission nebula | |
|---|---|
| Planetary nebula | |
 Image of Hu 2-1 seen in narrowband filters F658N & F656N | |
| Observation data: J2000 epoch | |
| Right ascension | 18h 49m 47.6s[1] |
| Declination | 20° 50′ 39″[1] |
| Apparent diameter | ~3"[2] |
| Constellation | Hercules |
| Designations | PN G051.4+09.6, PK 051+09 1[1] |
Humason 2-1 (Hu 2-1) is a bipolar planetary nebula. It has an elongated shape. This nebula has a radius of ~4.5 pc and was discovered by astronomer Milton Lassel Humason. It was discovered on June 23, 1992 at the Mount Wilson Observatory in California.[3]
Humason 2-1 has an angular radius of ~0.4,[4] which corresponds to a liner radius of ~4.5 10-3 pc if the distance of Hu 2-1 is 2.35 kpc.[5]The expansion velocity of Hu 2-1 is approximately 10-15 km s-1.[6] The nebula has a electron density of ~10⁴ cm-3.[7] Hu 2-1 has a rather high 5-GHz temperature of ~3455 K. The structure of Hu 2-1 is revealed by VLA radio continuum observations,[8] which displays an elongated shape with a major axis oriented at position angle (PA) of ~320°. And ~230°, and a small ring close to the central star with a major axis of ~0.7" long and a PA of 135°.
The central star
Central star of Hu 2-1 has a temperature of ~25-40 10³ K and a luminosity of ~11.5 10³ L,[9] placing it at the beginning of the PNe evolutionary track on the H–R diagram. The axisymmetric structure of Hu 2-1 is caused by the interaction of a binary companion with the primary stars envelope during the common envelope (CE) evolution.[10] The moderate density between the equatorial and polar reigons indicate the progenitor star evolved to a late AGB stage before entering the CE phase.[11]
References
- 1 2 3 "PN G051.4+09.6". simbad.cds.unistra.fr.
- ↑ "Humason 2-1, a 3" planetary nebula in Hercules". Cloudy Nights. Retrieved 17 August 2018.
- ↑ Humason, M.L. (23 June 1992). "A New Planetary Nebula". The Astronomical Society of the Pacific. 34 (201). IOP Publishing: 296a–296. doi:10.1086/123227. ISSN 1538-3873.
- ↑ Kowk, S. (January 1985). "High-resolution radio observations of compact planetary nebulae". The Astronomical Journal. 90: 49. doi:10.1086/113707.
- ↑ Martin, W. (January 1994). "Extinction-distances to planetary nebulae". Astronomy & Astrophysics. 281: 526–535. Bibcode:1994A&A...281..526M.
- ↑ Tamura, S.; Katsunori, M.; Shibata, M. (November 1990). "Expansion Analyses on Low-Excitation Nebulae with Stellar Images". Publications of the Astronomical Society of Japan. 102: 1301. Bibcode:1990PASP..102.1301T. doi:10.1086/132764.
- ↑ Stanghellini, L.; Kaler, J. B. (July 1989). "Electron densities in planetary nebulae". The Astrophysical Journal. 343: 811. doi:10.1086/167751.
- ↑ Aaquist, O. B.; Kowk, S. (1990). "August 1990". Astronomy & Astrophysics. 84: 229. Bibcode:1990A&AS...84..229A.
- ↑ Kaler, J. B.; Jacoby, G. H. (April 1991). "Central star temperatures of low-excitation planetary nebulae". The Astrophysical Journal. 372: 215. doi:10.1086/169967.
- ↑ Livio, M.; Soker (May 1989). "Interacting winds and the shaping of planetary nebulae". The Astrophysical Journal. 339: 268. doi:10.1086/167294.
- ↑ Livio, M.; Bond, H. E. (June 1990). "Morphologies of Planetary Nebulae Ejected by Close-Binary Nuclei". The Astrophysical Journal. 355: 568. Bibcode:1990ApJ...355..568B. doi:10.1086/168789.
