Shapley-1

Shapley-1 is a beautiful, small and faint planetary nebula in the constellation Norma. This nebula was discovered in 1936 by Harlow Shapley. Its distance appears to be difficult to determine with enough certainty. The values that appear in the literature range either around 1,000 light years (based on information published by the AAO -Anglo Australian Observatory) in the 90’s or around 4,700-4,900 light years based on more recent observations by D. Jones et al. (2012). The central star is a close binary system. Having a central binary system leads, in the case of planetary nebulae, to a non-spheric structure. Most literature sources affirm that its real structure is that of a “torus” (like a tire), but Jones provides abundant material to propose the more classical “butterfly” structure. The outer halo, more visible as a bluish OIII emission, is not a sphere (as expected by the “torus” model), but more an equatorial, somewhat flat, equatorial ring.

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