* Astronomy

NGC 3587 (also the Owl Nebula, Messier 97 and PN G148.4+57.0) is a magnitude +9.9 planetary nebula located 2,030 light-years away in the constellation Puppis.
The name "Owl Nebula" comes from a sketch by William Parsons in 1848 that depicts the two dark spots that look like the eyes of an owl.
The appearance was interpreted as a sphere, with the eyes of the owl as thinner areas at the poles. Its age is estimated at 6000 years.
Observationally, M97 is at the limit of visibility with a pair of binoculars. Its small apparent size and its relatively low brightness requires a 150mm aperture telescope with a lowish magnification for easy observing. Higher magnifications will show some of the details, such as the two dark spots that represent the "eyes" of the owl.
Its location is relatively easy to find, thanks to its proximity to the star Merak (beta Ursae Majoris).
M97 is one of the largest planetary nebulae known in absolute terms; it extends to a diameter of nearly 3 light-year. The central star is an extremely hot magnitude 14 white dwarf, whose surface temperature is around about 85,000 kelvin and with a mass equal to 0.7 solar masses.
The nebulas distance has long been a subject of debate; estimates range from a minimum of 1600 light years up to a maximum of 12,000, which would have put it beyond the edge of the galactic plane; today we tend to accept a value of ~2,600 light years. The total mass of the nebula is about 0.13 solar masses and its density is of the order of 100 particles per cubic meter, around a tenth of the average of other planetary nebulae; this would indicate an older age for the nebula, since over time it has greatly expanded and rarefied the gas. The age would be about 6000 years.

The nebula was discovered by French astronomer Pierre Méchain using a 15.24 cm (6 inch) speculum newtonian reflector on the 16th February 1781.

Right Ascension 11h 14m 47.7s, Declination +55° 01' 08"

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