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Stingray Nebula
The Stingray Nebula (Hen 3-1357) is the youngest known planetary nebula (PN). The Stingray is located in the direction of the southern constellation
Ara (the Altar), and is located 18,000 light-years away. Although it is some 130 times the size of our solar system, the Stingray Nebula is only about 1/10 the size of most other known planetary nebulae. Forty years ago it was still a protoplanetary nebula in which the gas had not yet become hot and ionized. In a ''Nature'' article, Bobrowsky et al. described how the Hubble observations revealed a 17th-magnitude companion to the Stingray's 15th-magnitude central star. The image of the Stingray Nebula shown here shows how the outer shells of gas are collimating the continuing outflow of gas from the central star—an important observation, as the process of how these outflows become collimated has not been well understood.
==History==
Prior to the discovery of the nebula, the central star of the Stingray Nebula was known as He3-1357, which Karl Gordon Henize classified as an A or B type Hα emission line star in 1967. It was observed in 1971 to be a pre-planetary nebula (PPNe) when it seemed to be an asymptotic giant branch (AGB) B1 supergiant. Planetary nebula (PN) emission lines were identified in this star in 1989 by the IUE (Parthasarathy et al. 1993). As the nebula would be newly formed and very small, ground-based observations were not able to resolve it; so Bobrowsky〔 observed it with the Hubble Space Telescope, discovering the nebula, which he named the "Stingray Nebula."
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