Clues from Butterfly Nebula dust advance knowledge of rocky planet origins

Clues from Butterfly Nebula dust advance knowledge of rocky planet origins
by Sam Tonkin for RAS News
London UK (SPX) Sep 01, 2025

Clues about the formation of Earth-like planets have emerged from the Butterfly Nebula NGC 6302, where astronomers used the James Webb Space Telescope and ALMA to probe its dusty heart. The combined observations revealed crystalline silicates, irregular dust grains, jets of iron and nickel, and even carbon-based molecules thought to be precursors of life.

Lead researcher Dr Mikako Matsuura of Cardiff University said: "For years, scientists have debated how cosmic dust forms in space. But now, with the help of the powerful James Webb Space Telescope, we may finally have a clearer picture." She added that Webb data show gemstone-like grains forming in stable regions alongside chaotic soot created in turbulent zones.

The nebula's central star, one of the hottest in our galaxy at 220,000 Kelvin, drives the system's radiant glow. Webb's Mid-InfraRed Instrument uncovered a vertical doughnut-shaped torus of dust surrounding the star, hiding it from view at optical wavelengths. The dust includes relatively large grains about a millionth of a metre across, suggesting long-term growth.

Scientists also detected polycyclic aromatic hydrocarbons, or PAHs, in an oxygen-rich planetary nebula for the first time. These ring-shaped carbon molecules may have formed when stellar winds punched through surrounding gas. On Earth, PAHs are found in smoke and combustion products, and their discovery in NGC 6302 provides a new glimpse into how complex organics emerge.

NGC 6302 lies 3,400 light-years away in Scorpius. Planetary nebulae like this one are created when Sun-like stars shed their outer layers during their final stages of life, producing ephemeral displays lasting only about 20,000 years. The Butterfly Nebula's dramatic bipolar wings and dark central band illustrate how dense dusty tori can sculpt stellar outflows.

The new study combined Webb's infrared imaging and spectroscopy with radio data from ALMA, yielding nearly 200 distinct spectral lines that map the nebula's chemical and structural layers. The observations also finally pinpointed the location of the long-hidden central star through its warm dust shroud.

Research Report:The JWST/MIRI view of the planetary nebula NGC 6302 I.: a UV irradiated torus and a hot bubble triggering PAH formation'