|Right ascension||11h 14m 47.734s|
|Declination||+55° 01′ 08.50″|
|Distance||2,030 ly (621 pc)|
|Apparent magnitude (V)||+9.9|
|Apparent dimensions (V)||3′.4 × 3′.3|
|Radius||0.91 ly (0.28 pc)|
|Notable features||Owl-like "eyes" visible through larger telescopes|
|Other designations||M97, NGC 3587, PN G148.4+57.0|
|See also: Planetary nebula, Lists of nebulae|
The Owl Nebula is a planetary nebula located some 2,030 light years away in the constellation Ursa Major. This object is known by the catalogue identifiers Messier Object 97 (M97) and NGC 3587. It was discovered by French astronomer Pierre Méchain on February 16, 1781. When William Parsons, 3rd Earl of Rosse observed the nebula in 1848, his hand-drawn illustration resembled an owl's head. It has been known as the owl nebula ever since.
This 8,000 year old planetary nebula is essentially circular in cross-section with a "relatively bland internal structure". It was formed from the outflow of material from the stellar wind of the central star as it evolved along the asymptotic giant branch. The nebula is arranged in three concentric shells, with the outermost shell being about 20–30% larger than the inner shell. The owl-like appearance of the nebula is the result of an inner shell that is not circularly symmetric, but instead forms a barrel-like structure aligned at an angle of 45° to the line of sight.
The nebula holds about 0.13 times the mass of the Sun worth of matter, including hydrogen, helium, nitrogen, oxygen, and sulfur; all with a density of less than 100 particles per cubic centimeter. Its outer radius is around 0.91 ly (0.28 pc) and it is expanding with velocities in the range of 27–39 km/s into the surrounding interstellar medium.
The 14th magnitude central star has since reached the turning point of its evolution where it condenses to form a white dwarf. It has 55–60% of the Sun's mass, 41–148 times the brightness of the Sun, and an effective temperature of 123,000 K. The star has been successfully resolved by the Spitzer Space Telescope as a point source that does not show the infrared excess characteristic of a circumstellar disk.
- Kerber, F. et al. (September 2003), "Galactic Planetary Nebulae and their central stars. I. An accurate and homogeneous set of coordinates", Astronomy and Astrophysics 408: 1029–1035, Bibcode:2003A&A...408.1029K, doi:10.1051/0004-6361:20031046.
- Stanghellini, Letizia et al. (December 2008), "The Magellanic Cloud Calibration of the Galactic Planetary Nebula Distance Scale", The Astrophysical Journal 689 (1): 194–202, Bibcode:2003A&A...408.1029K, doi:10.1051/0004-6361:20031046.
- Cuesta, L.; Phillips, J. P. (November 2000), "Excitation and Density Mapping of NGC 3587", The Astrophysical Journal 120 (5): 2661–2669, Bibcode:2000AJ....120.2661C, doi:10.1086/316800.
- Jones, Kenneth Glyn (1991), Messierś Nebulae and Star Clusters (2nd ed.), Cambridge University Press, pp. 277–279, ISBN 0521370795.
- Clark, Roger Nelson (1990), Visual Astronomy of the Deep Sky, CUP Archive, p. 133, ISBN 0521361559.
- Per Guerrero et al (2003), the age is 12,900 × d years, where d is the distance in kpc. According to Stanghellini et al (2008), d is 0.621 kpc. Hence, the age is 12,900 × 0.621 ≈ 8,000 years.
- Guerrero, Martín A. et al. (June 2003), "Physical Structure of Planetary Nebulae. I. The Owl Nebula", The Astrophysical Journal 125 (6): 3213–3221, arXiv:astro-ph/0303056, Bibcode:2003AJ....125.3213G, doi:10.1086/375206.
- Capriotti, Eugene R.; Kovach, William S. (March 1968), "Effective Temperatures of the Central Stars of Planetary Nebulae", Astrophysical Journal 151 (5): 991–995, Bibcode:1968ApJ...151..991C, doi:10.1086/149498.
- Bilíková, Jana et al. (May 2012), "Spitzer Search for Dust Disks around Central Stars of Planetary Nebulae", The Astrophysical Journal Supplement 200 (1): 3, Bibcode:2012ApJS..200....3B, doi:10.1088/0067-0049/200/1/3.
- The Owl Nebula on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
- The Owl Nebula at Calar Alto Observatory
- The Owl Nebula @ SEDS Messier pages
- NightSkyInfo.com – M97, the Owl Nebula
- Norton, Andy; Crowther, Paul; Hardy, Liam. "M97 – Owl Nebula". Deep Space Videos. Brady Haran.