Owl Nebula (M 97) + Galaxy M 108

Messier 97
Messier 97: Owl Nebula in Ursa Major; 500 mm Cassegrain 5800 mm f/11.4; SBIG STL11K; 100+20+20+20 min LRGB; Bernese Highlands; © 2005 Radek Chromik

Owl Nebula M 97

This planetary nebula was discovered on 16 February 1787 by the French astronomer Pierre Méchain. He was a younger colleague and close friend of Charles Messier. [196] The name «Owl Nebula» goes back to the Irish astronomer William Parsons, the 3rd Earl of Rosse (mostly just called «Lord Rosse»), who observed the nebula in 1848 and made the cute drawing shown in Fig. 2. According to him, both stars had been visible in the owl's eyes until March 1850, but then one faded and was no longer seen. [4]

Messier 97
Messier 97: Drawing, Lord Rosse, 1848 [217]

M 97 is one of the more complex planetary nebulae. The appearance is interpreted by an obliquely viewed torus, whose material-poor eyes correspond to the eyes of the owl. This shell is surrounded by a weaker nebula with less ionization. The mass of the nebula is estimated to be about 0.15 solar masses. The 16 mag bright central star probably has 0.7 solar masses. The age of the planetary nebula is estimated to be around 6000 years. [17]

The distances given are very imprecise and range from 1300 to 12'000 light years. A latest measurement by Gaia DR2 in 2018 indicates a distance of 879 parsecs (2867 light years). [145]

«Strasbourg-ESO Catalogue of Galactic Planetary Nebulae» Acker et al., 1992 [141]
DesignationsPN G148.4+57.0: NGC 3587, PK 148+57.1, ARO 25, M 97, VV 59, VV'107
Right Ascension (J2000.0)11h 14m 46s
Declination (J2000.0)+55° 00' 59"
Dimensions 170." (optical), 170." (radio)
Distance 0.5 kpc
Radial Velocity+6.0 km/s ± 3.1 km/s
Expansion Velocity 29.0 km/s (O-III), 40. km/s (N-II)
C-Star DesignationsAG82 135
C-Star Magnitude14.36 mag (U filter), 15.66 mag (B filter), 16.01 mag (V filter)
DiscovererLORD ROSSE 1850
M 97 + M 108
M 97 + M 108: Owl Nebula M 97 and Galaxy M 108 Ursa Major; 10" Meade Schmidt-Newton, Canon EOS 20Da; 75 min, ISO 1600; Oberes Schlierental, Obwalden; © 2007 Eduard von Bergen

Next to the Owl Nebula, just 19 arc minutes away, lies the star FI Ursae Majoris. It is a variable star of the δ Scuti type. Its brightness is 6.64 mag in the V-band and it pulsates around 0.007 mag with a period of 0.0400 days (57.4 minutes). [228]

Galaxy M 108

Messier 108
Messier 108: Galaxy in Ursa Major; 500 mm Cassegrain 3625 mm f/7.2; SBIG STL11K; 60+20+20+20 min LRGB; Bernese Highlands; © 2011 Radek Chromik

This galaxy was discovered by Pierre Méchain on 19 February 1781, and it was rediscovered by Charles Messier on March 24 of the same year. Both indicated the position relative to the planetary nebula M 97. Messier marked it as 98 in a preliminary manuscript of his catalog, but failed to measure the exact location before publishing his catalog. He added a handwritten note to his personal copy, which is why Owen Gingerich did not identify the galaxy as NGC 3556 until 1953 and added it to the Messier catalog as number 108. [196]

M 108 is a spiral galaxy of the Sc type, which we can see almost from the side. It shows no or only a very slight bulge and no noticeable center, but mainly dust bands. The distance is estimated to be around 40 to 50 million light years. M 108 belongs to a loose group to which M 109 and probably also M 106 belong. [233]

Revised+Historic NGC/IC, Version 22/9, © Dr. Wolfgang Steinicke [277]
DesignationNGC 3556
TypeGx (Sc)
Right Ascension11h 11m 29.4s
Declination+55° 40' 22"
Diameter8.6 × 2.4 arcmin
Photographic (blue) magnitude10.7 mag
Visual magnitude10.0 mag
Surface brightness13.1 mag·arcmin-2
Position angle80°
Redshift0.002332
Distance derived from z9.85 Mpc
Metric Distance14.320 Mpc
Dreyer DescriptioncB, vL, vmE 79°, pbM, r
Identification, RemarksM 108, UGC 6225, MCG 9-18-98, IRAS 11085+5556, CGCG 267-48, CGCG 268-1, KARA 469

Finder Chart

The odd couple is very easy to find. It is located slightly below the second third between the two drawbar stars Phecda (γ Ursae Majoris) and Merak (β Ursae Majoris) of the Big Dipper. It is circumpolar, but the best time to watch it is December to June. Then the constellation is highest in the sky at night. In a large field eyepiece with low magnification and at least 1 ° field of view, both should be visible at the same time.

Chart Owl Nebula (M 97) + Galaxy M 108
Owl Nebula (M 97) + Galaxy M 108 in constellation Ursa Maior. Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

More Objects Nearby (±15°)

References

4«Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System» by Robert Burnham; Dover Publications, Inc.; Voume I: ISBN 0-486-23567-X; Volume II: ISBN 0-486-23568-8; Volume III: ISBN 0-486-23673-0
17«Planetary Nebulae: A Practical Guide and Handbook for Amateur Astronomers» by Steven J. Hynes; 1991, Willmann-Bell, Inc., Richmond Virginia; ISBN 0-943396-30-1
141Strasbourg-ESO Catalogue of Galactic Planetary Nebulae; A. Acker, F. Ochsenbein, B. Stenholm, R. Tylenda, J. Marcout, C. Schohn; European Southern Observatory; ISBN 3-923524-41-2 (1992); cdsarc.unistra.fr/viz-bin/cat/V/84 (2021-02-18)
145SIMBAD astronomical database; simbad.u-strasbg.fr/simbad
149SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
160The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
196Celestial Atlas by Curtney Seligman; cseligman.com/text/atlas.htm (2020-12-28)
217The Messier Catalog (SEDS); messier.seds.org (2021-01-01)
228«A revised catalogue of δ Sct stars» E. Rodríguez, M. J. López-González and P. López de Coca; Astron. Astrophys. Suppl. Ser. Volume 144, Number 3, June II 2000; DOI:10.1051/aas:2000221
233NOIRLab: M108, NGC 3556; noirlab.edu/public/images/noao-m108
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; klima-luft.de/steinicke (2021-02-17)