NGC 40

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NGC 40
Emission nebula
Planetary nebula
NGC 40 Ps1.png
PanSTARRS false-color image of NGC 40, using the red r-band image as blue
Observation data: J2000 epoch
Right ascension 00h 13m 01.017s [1]
Declination +72° 31′ 19.03″ [1]
Distance1,619 [2]   pc
Apparent magnitude (V)11.6 [3]
Apparent dimensions (V)38″ × 35″ [3]
Constellation Cepheus
DesignationsBow-Tie Nebula, Caldwell  2, PN G120.0+09.8
See also: Lists of nebulae

NGC 40 (also known as the Bow-Tie Nebula and Caldwell 2) is a planetary nebula discovered by William Herschel on November 25, 1788, and is composed of hot gas around a dying star. The star has ejected its outer layer which has left behind a small, hot star. [4] Radiation from the star causes the shed outer layer to heat to about 10,000 degrees Celsius and become visible as a planetary nebula. The nebula is about one light-year across. [4] About 30,000 years from now, scientists theorize that NGC 40 will fade away, leaving only a white dwarf star approximately the size of Earth. [4]

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Morphologically, the shape of NGC 40 resembles a barrel with the long axis pointing towards the north-northeast. There are two additional pairs of lobes around the poles, which correspond to additional ejections from the star. [5]

The central star of NGC 40 has a Henry Draper Catalogue designation of HD 826. [6] It has a spectral type of [WC8], indicating a spectrum similar to that of a carbon-rich Wolf–Rayet star. [7] The central star has a bolometric luminosity of about 7,000  L☉ and radius of 0.56  R☉. The star appears to have an effective temperature of about 71,000  K , but the temperature of the source ionizing the nebula is only about 45,000 K. One proposed explanation to this contradiction is that the star was previously cooler, but has experienced a late thermal pulse which re-ignited fusion and caused its temperature to increase. [6]

See also

References

  1. 1 2 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 record for this source at VizieR.
  2. ↑ Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Demleitner, M.; Andrae, R. (2021). "Estimating Distances from Parallaxes. V. Geometric and Photogeometric Distances to 1.47 Billion Stars in Gaia Early Data Release 3". The Astronomical Journal. 161 (3): 147. arXiv: 2012.05220 . Bibcode:2021AJ....161..147B. doi: 10.3847/1538-3881/abd806 . S2CID   228063812.
  3. 1 2 O'Meara, Stephen James (2002). Deep Sky Companions: The Caldwell Objects. Sky Publishing Corporation. pp. 22–23. ISBN   978-0-933346-97-0.
  4. 1 2 3 "Chandra X-Ray Observatory" . Retrieved 2007-06-05.
  5. ↑ Rodríguez-González, J. B.; Toalá, J. A.; Sabin, L.; Ramos-Larios, G.; Guerrero, M. A.; López, J. A.; Estrada-Dorado, S. (2022). "Adjusting the bow-tie: A morpho-kinematic study of NGC 40". Monthly Notices of the Royal Astronomical Society. 515 (2): 1557–1567. arXiv: 2206.13368 . doi: 10.1093/mnras/stac1761 .
  6. 1 2 Toalá, J. A.; Ramos-Larios, G.; Guerrero, M. A.; Todt, H. (2019). "Hidden IR structures in NGC 40: Signpost of an ancient born-again event". Monthly Notices of the Royal Astronomical Society. 485 (3): 3360. arXiv: 1902.11219 . Bibcode:2019MNRAS.485.3360T. doi: 10.1093/mnras/stz624 .
  7. ↑ González-Santamaría, I.; Manteiga, M.; Manchado, A.; Ulla, A.; Dafonte, C.; López Varela, P. (2021). "Planetary nebulae in Gaia EDR3: Central star identification, properties, and binarity". Astronomy & Astrophysics. 656: A51. arXiv: 2109.12114 . Bibcode:2021A&A...656A..51G. doi:10.1051/0004-6361/202141916. S2CID   237940344.
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