Shapley 1 (Sp 1, PLN 329+2.1) — a planetary nebula in Norma

Overview and designations

Shapley 1 is cataloged under several identifiers used by observers and researchers. As a member of the class of objects known as planetary nebulae, it represents the ionized envelope once shed by a low‑ to intermediate‑mass star. The nebula lies toward the southern Milky Way and is associated with the sky area of Norma, sometimes referenced in broader surveys of the region (constellation context).

Appearance and physical properties

In telescopic images Shapley 1 typically appears as a faint, roughly circular shell of glowing gas. Planetary nebulae like this radiate strongly in emission lines such as hydrogen and doubly ionized oxygen, producing the characteristic colored rings and shells familiar from astrophotography. Its visible structure and brightness depend on factors such as orientation, the central star's temperature, and the density of expelled material.

Formation and significance

Planetary nebulae are a short but important phase in stellar evolution: a red giant expels outer layers and exposes a hot central core that ionizes the ejected gas. Objects such as Shapley 1 provide clues about mass loss, chemical enrichment of the interstellar medium, and the late stages of Sun‑like stars. They are studied with spectroscopy and imaging to determine composition, expansion velocity, and central star properties.

Observing Shapley 1 and notable facts

• Discovery: credited to H. Shapley, 1936.
• Location: southern constellation Norma (see constellation references).
• Alternative names: Sp 1, PLN 329+2.1.

Shapley 1 is a representative example of planetary nebulae found in deep sky surveys and remains of interest to amateur observers with appropriate southern skies and professional researchers studying nebular physics and stellar evolution.