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Humason 2-1

Hu 2-1
Emission nebula
Planetary nebula
Image of Hu 2-1 seen in narrowband filters F658N & F656N
Observation data: J2000 epoch
Right ascension18h 49m 47.6s[1]
Declination20° 50′ 39″[1]
Apparent diameter~3"[2]
ConstellationHercules
DesignationsPN G051.4+09.6, PK 051+09 1[1]
See also: Lists of nebulae

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. The nebula was named after 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, assuming a distance of 2.35 kpc.[5]The expansion velocity of Hu 2-1 is approximately 10-15 km s-1.[6] Relatively speaking, the nebula has a electron density of ~10⁴ cm-3.[7] And a rather high 5-GHz temperature of 5GHz of ~3455 K.The structure of Hu 2-1, as revealed by VLA radio continuum observations,[8] 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 has a major axis of ~0.7" long and a PA of 135°

The central star

The central star of Hu 2-1 has a temperature of ~25-40 10³ K and also has a luminosity of ~11.5 10³ L.[9] Placing it at the beginning of the PNe evolutionary tracks on the H-R diagram. The axisymmetric structure of Hu 2-1 may be 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 may indicate that the progenitor star evolved to a late AGB stage before entering the CE phase.[11]

References

  1. ^ a b c "PN G051.4+09.6". simbad.cds.unistra.fr.
  2. ^ "Humason 2-1, a 3" planetary nebula in Hercules". Cloudy Nights. Retrieved 17 August 2018.
  3. ^ 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.
  4. ^ Kowk, S. (January 1985). "High-resolution radio observations of compact planetary nebulae". The Astronomical Journal. 90: 49. doi:10.1086/113707.
  5. ^ Martin, W. (January 1994). "Extinction-distances to planetary nebulae". Astronomy & Astrophysics. 281: 526–535. Bibcode:1994A&A...281..526M.
  6. ^ 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.
  7. ^ Stanghellini, L.; Kaler, J. B. (July 1989). "Electron densities in planetary nebulae". The Astrophysical Journal. 343: 811. doi:10.1086/167751.
  8. ^ Aaquist, O. B.; Kowk, S. (1990). "August 1990". Astronomy & Astrophysics. 84: 229. Bibcode:1990A&AS...84..229A.
  9. ^ 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.
  10. ^ Livio, M.; Soker (May 1989). "Interacting winds and the shaping of planetary nebulae". The Astrophysical Journal. 339: 268. doi:10.1086/167294.
  11. ^ 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.

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