"Owl Nebula "

J2000
RA: 11h 14m 46,39s
Dec: +55° 00' 59,7 "
Mag. 12,00
Surface bright: 14,00
Dim.: 202" x 196"
Central star : 16,01
Constellation: UMa

Discovery: Pierre Mèchain 16 feb. 1781
Distance: 0,6 kpc
Radius: 0,298 pc

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NGC 3587, also known as M97, is a very famous and peculiar Planetary Nebula located in the Big Dipper. Its popularity comes from its particular morphology. Besides the typical rounded structure, there are two dark zones inside from which comes the nickname "Owl Nebula" (given by Lorde Rosse), giving the nebula an owl-faced shape. It is not an easy target from light-polluted skies, expecially if you're using a small telescope, due to its low surface-magnitude. Dark skies are required as also 8" telescopes to see some details. OIII filter gives a big emprovement, allowing you to see distinctly the eyes and the rounded shape.
There is a pair of theories about its structure: someone thinks it's a particular kind of bipolar PN; someone thinks it's an elongated PN, giving us this perception because of its angle of inclination. The modern high-resolution spectrography researches have found that this nebula is, indeed, a dense gas bubble with a bipolar cavity formed by the star-wind from the central star. But it's still unknown why the star-wind has this asymmetrical distribution, giving hints about a probable binary core. Infact, a very tight binary nucleus can cause an asymmetrical mass-loss distribution during AGB (Asymptotic Giant Branch) phase. But these are only hipothesys at the present day. Waiting for omre investigations and researches to verify these suppositions.

Interesting level: *