Exploring Sh2-216: The Closest & Largest Planetary Nebula

Welcome to another enlightening article brought to you by the dedicated team at FreeAstroScience.com. In this piece, we delve into the mysteries of the cosmos, shining a spotlight on one of the largest and closest known planetary nebulae, Sh2-216. This celestial body, nestled in the constellation of Perseus, has intrigued astronomers since its discovery in 1955. Join us as we explore the fascinating details of this distant cosmic spectacle.

Sh2-216: A Cosmic Discovery in the Constellation of Perseus

Embedded within the constellation of Perseus, at a distance of approximately 416 light-years from our planet, resides the planetary nebula known as Sh2-216. This celestial body first caught the attention of the scientific community when it was discovered by Hugh M. Johnson in 1955. It also goes by other names like PK 158+00 1, YM 22, and LBN 744.

Sh2-216: The Closest and One of the Largest Known Planetary Nebulae

One of the distinguishing features of Sh2-216 is its proximity to Earth and its expansive size. This nebula holds the title of being the closest and one of the largest known planetary nebulae. Observations carried out in 1984 cemented Sh2-216's status as a planetary nebula. 

The Age, Size and Expansion Velocity of Sh2-216

The expansion velocity, or the speed at which Sh2-216 is spreading out into the cosmos, was estimated to be around 4 km/sec. This finding suggests that the nebula's ejecta have been decelerated by the interstellar matter. Based on these observations, the nebula's age was pegged at roughly 300,000 years. Furthermore, its size was determined to be a staggering 12 light-years across, derived from its known distance from Earth.

The Power Source of Sh2-216: A White Dwarf

At the heart of Sh2-216, a white dwarf with a mass equivalent to 0.55 solar masses powers the nebula. This stellar remnant is still incredibly hot, boasting a temperature of 95,000 Kelvin.

A Glimpse of Sh2-216 through an Amateur Telescope

John Travis, an amateur astronomer, provided us with a composite optical image of Sh2-216, captured using a small telescope. This striking image was created using broadband filters (RGB), along with narrow band filters that highlight the emission of ionised oxygen ([O III]), ionised hydrogen (Hα), and ionised sulphur ([S II]).