M97 - Owl Nebula
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Messier 97, also known as the Owl Nebula, is a planetary nebula located about 2,030 light-years from Earth in the constellation Ursa Major. Its age is estimated at around 6,000 to 8,000 years. The nebula has an approximately circular shape and features a subtle internal structure made up of three main concentric shells, with the outermost shell about 20 to 30 percent larger than the inner one. Its owl-like appearance, especially the dark patches resembling eyes, comes from the inner shell’s barrel-shaped structure, which is tilted at a 45 degree angle relative to our line of sight.
To find the nebula in the night sky, look southeast of the Big Dipper’s bowl, near the star Merak (Beta Ursae Majoris, β UMa). From there, M97 lies just over 2.5 degrees to the southeast, toward the star Phecda (Gamma Ursae Majoris, γ UMa).
Observations
June 26, 2024, around midnight – Jaworzno (Poland), garden
urban conditions, high level of light pollution
The Owl Nebula is a relatively faint object that cannot be seen with the naked eye, even under ideal observing conditions. For visual observation, a small telescope or large binoculars (20×80) will reveal it as a dim, featureless patch of light. To discern the nebula’s characteristic structure, including the darker areas that look like an owl’s eyes and give the nebula its name, a telescope with an aperture of at least 15 to 20 centimeters (6 to 8 inches) is needed. However, as with most deep-sky objects, the best way to observe the Owl Nebula is through long-exposure astrophotography (Photo 1).
The nebula’s mass is relatively small, with a mass of only 0.13 solar masses (0.13 M☉). It is primarily composed of hydrogen (H), helium (He), nitrogen (N), oxygen (O), and sulfur (S), with a density of less than 100 particles per cubic centimeter. Its outer radius is approximately 0.91 light-years and is expanding at a speed of 27–39 km/s.
The central star, with an apparent magnitude of 14m, ejected a large portion of its material during the final stages of its evolution, forming the nebula. It has since transformed into a white dwarf with a mass of 55–60% that of the Sun, yet it is several times brighter and hotter than our star. Nuclear fusion no longer takes place within the white dwarf, so it will gradually cool as it radiates its remaining energy.
Photo 1 Parameters:
- Total exposure time: 70 minutes (stack of 70 RAW frames at 60s each, using an appropriate number of dark, bias, and flat frames)
- Canon EOS 60D
- ISO: 1500
- Achromatic refractor Messier AR-152S (152/760), prime focus exposure
- A filter was used to reduce the effects of artificial light pollution and atmospheric glow
- Mount: equatorial mount with tracking, aligned using the drift method and controlled by a custom-built system
Futher readings:
- Stanghellini L., Shaw R. A., Villaver E., The Magellanic Cloud Calibration of the Galactic Planetary Nebula Distance Scale, The Astrophysical Journal, 2008, 689(1), str. 194-202
- Guerrero M. A., and Chu Y.-H., Manchado A., Kwitter K. B., Physical Structure of Planetary Nebulae. I. The Owl Nebula, The Astrophysical Journal, 2003, 125(6): str. 3213-3221
- Jones K. G., Messierś Nebulae and Star Clusters (2nd ed.), Cambridge University Press, 1991, str. 277-279,
Marek Ples