The NASA/ESA/CSA James Webb Space Telescope has reobserved the planetary nebula NGC 2392, also known as the Lion Nebula, using NIRCam and MIRI. The near- and mid-infrared images bring out fine-grained dust structures, diffuse shells of ionized gas, and the central white dwarf with a clarity not achieved before.
Object and origin
NGC 2392 represents the final evolutionary stage of a Sun-like star. After the star shed its outer layers, the remaining hot core — a white dwarf — ionizes the surrounding gas. The visible bubble of gas and dust formed over several thousand years and continues to expand.
What Webb reveals
In the near-infrared, pronounced, clumpy dust patterns become apparent; in the mid-infrared, warmer dust components and extended diffuse gas regions glow. Compared with previous optical images, differences in temperature and density are now more clearly distinguishable. Regions with enhanced mid-infrared emission point to larger or warmer dust grains, while other zones are dominated by lines from ionized gas.
Dynamics of the structures
The fast stellar wind from the central star collides with material that was previously expelled more slowly, producing shock fronts. This interaction sculpts clumps and compresses gas and dust into complex patterns. Asymmetries can be amplified by variable mass loss, a possible companion star, or magnetic fields — processes also observed in other planetary nebulae.
Chemical signatures
MIRI’s sensitivity in the mid-infrared reveals characteristic emission features typically associated with aromatic hydrocarbons (PAHs) and silicate dust. Such signatures provide clues to the chemical evolution of the material that dying stars return to the interstellar medium.
Why the data matter
Planetary nebulae contribute gas and dust to the galaxy, the raw material for new stars and planetary systems. Webb’s level of detail makes it possible to analyze temperature and density distributions, compositions, and motions separately. Time-series observations could allow measurable position changes of individual structures and reveal differences in expansion over decades.
Next steps
Analyses of the Webb data will refine the spectral fingerprints and derive velocities. Comparing the new images with older Hubble observations opens the possibility of tracking changes over timescales of decades.