Owl Nebula

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Messier 97, Owl Nebula
Emission nebula
Planetary nebula
Noao-m97.tif
Owl Nebula Messier 97
Observation data: J2000.0 epoch
Right ascension 11h 14m 47.734s [1]
Declination +55° 01 08.50 [1]
Distance2,030  ly (621  pc) [2]
2,800  ly (870  pc) [3]   ly
Apparent magnitude (V)9.9 [4]
Apparent dimensions (V)3′.4 × 3′.3
Constellation Ursa Major
Physical characteristics
Radius 0.91 ly (0.28 pc) [5]  ly
Notable featuresOwl-like "eyes" visible through larger telescopes
DesignationsM97, NGC 3587, PN G148.4+57.0
See also: Lists of nebulae

The Owl Nebula (also known as Messier 97, M97 or NGC 3587) is a planetary nebula approximately 2,030 light years away in the constellation Ursa Major. [2] Estimated to be about 8,000 years old, [6] it is approximately circular in cross-section with a faint 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. [5] The nebula is arranged in three concentric shells, with the outermost shell being about 20–30% larger than the inner shell. [7] 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. [5]

Contents

The nebula holds about 0.13 solar masses (M) of matter, including hydrogen, helium, nitrogen, oxygen, and sulfur; [5] all with a density of less than 100 particles per cubic centimeter. [7] 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. [5]

The 14th magnitude central star has passed the turning point in its evolution and is condensing to form a white dwarf. [7] [8] It has 55–60% of solar mass, is 41 to 148 times solar luminosity (L), [5] and has an effective temperature of 123,000 K. [9] 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. [10]

History

The Owl Nebula was discovered by French astronomer Pierre Méchain on February 16, 1781. [8] Pierre Méchain was Charles Messier's observing colleague, and the nebula was observed by Messier himself a few weeks following the initial sighting. [11] Thus, the object was named Messier 97, and included in his catalog on March 24, 1781. [12] Of the object, he noted: [13] [14] [15] [16]

Nebula in the great Bear, near Beta: It is difficult to see, reports M. Méchain, especially when one illuminates the micrometer wires: its light is faint, without a star. M. Méchain saw it the first time on Feb 16, 1781, & the position is that given by him. Near this nebula he has seen another one, [the position of] which has not yet been determined [Messier 108], and also a third which is near Gamma of the Great Bear [Messier 109]. (diam. 2′).

In 1844, Admiral William H. Smyth classified the object as a planetary nebula. [12] [17] When William Parsons, 3rd Earl of Rosse, observed the nebula in Ireland in 1848, his hand-drawn illustration resembled an owl's head. In his notes, the object was described as "Two stars considerably apart in the central region, dark penumbra round each spiral arrangement, with stars as apparent centres of attraction. Stars sparkling in it; resolvable." [18] [19] It has been known as the Owl Nebula ever since. [20] More recent developments in the late 1900s include the discovery of a giant red halo of wind extended around its inner shells, [21] and the mapping of the nebula's structure. [17] [22] [23]

Observing

Although the Owl Nebula can not be seen with the naked eye, a faint image of it can be observed under remarkably good conditions with a small telescope or 20×80 binoculars. To make out the nebula's more distinctive owl like eye features, a telescope with an aperture 10" or better is required. To locate the nebula in the night sky, look to the southwest corner of the Big Dipper's bowl, marked by the star Beta Ursae Majoris. From there, M97 lies just over 2.5 degrees in the southeast direction towards the star positioned opposite Beta Ursae Majoris in the other bottom corner of the Big Dippers Bowl, Gamma Ursae Majoris; which marks the constellations southwest corner. M97, together with Alpha Ursae Majoris, point the way to Polaris. [24]

See also

Related Research Articles

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<span class="mw-page-title-main">Saturn Nebula</span> Planetary nebula in the constellation Aquarius

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Messier 105 or M105, also known as NGC 3379, is an elliptical galaxy 36.6 million light-years away in the equatorial constellation of Leo. It is the biggest elliptical galaxy in the Messier catalogue that is not in the Virgo cluster. It was discovered by Pierre Méchain in 1781, just a few days after he discovered the nearby galaxies Messier 95 and Messier 96. This galaxy is one of a few not object-verified by Messier so omitted in the editions of his Catalogue of his era. It was appended when Helen S. Hogg found a letter by Méchain locating and describing this object which matched those aspects under its first-published name, NGC 3379.

<span class="mw-page-title-main">Messier 108</span> Galaxy in the constellation Ursa Major

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<span class="mw-page-title-main">NGC 2362</span> Open cluster in the constellation Canis Major

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<span class="mw-page-title-main">NGC 7027</span> Planetary nebula in the constellation Cygnus

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<span class="mw-page-title-main">NGC 6751</span> Planetary nebula in the constellation Aquila

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<span class="mw-page-title-main">NGC 2022</span> Planetary nebula in the constellation Orion

NGC 2022 is a planetary nebula in the equatorial constellation of Orion, located at a distance of 8.21 kilolight-years from the Sun. It was first observed by William Herschel on December 28, 1785, who described it as: considerably bright, nearly round, like a star with a large diameter, like an ill-defined planetary nebula. In medium-sized amateur telescopes it looks like a small grayish patch of light. It is not very bright but it is still easy to spot it in the eyepiece. Even in a telescope as small as 80mm it can just be seen using a narrowband filter such as an OIII filter as a 'fuzzy' star. The object has the shape of a prolate spheroid with a major to minor axis ratio of 1.2, an apparent size of 28″, and a halo extending out to 40″, which is about the angular diameter of Jupiter as seen from Earth.

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References

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  6. 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.
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  23. Sabbadin, F.; Bianchini, A.; Ortolani, S.; Strafella, F. (1985-12-01). "The structure of NGC 3587, the Owl nebula". Monthly Notices of the Royal Astronomical Society. 217 (3): 539–549. Bibcode:1985MNRAS.217..539S. doi: 10.1093/mnras/217.3.539 . ISSN   0035-8711.
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