The spectacular innards of a star in its final stages may be the key astronomers use to trace the very earliest beginnings of how Earth was formed.
Butterfly Nebula NGC 6302: where dust turns to crystal
Astronomers studying the Butterfly Nebula NGC 6302 have uncovered strong signs that dust is crystallising as it cools out of hot gas. The nebula sits roughly 3,400 light-years from Earth, in the southern constellation of Scorpius.
"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," says astrophysicist Mikako Matsuura of Cardiff University in the UK.
"We were able to see both cool gemstones formed in calm, long-lasting zones and fiery grime created in violent, fast-moving parts of space, all within a single object. This discovery is a big step forward in understanding how the basic materials of planets come together."
Cosmic dust and the swansong of a dying star
Cosmic dust really is what the name suggests: tiny particles drifting through the space between stars. Researchers think much of it is produced in the outer layers of dying stars, helping to seed nebular matter that later feeds newborn stars and the planets that form around them.
The Butterfly Nebula is a striking final act from just such a star. It is a planetary nebula (so named because early examples were round and planet-like in appearance): an expanding shell of material created when a star sheds its outer layers into space at the end of its life.
At the nebula’s centre lies a white dwarf - the leftover core of a once-giant star that has already passed through its most dramatic final changes. Rather than forming a tidy, circular bubble, NGC 6302 shows two forcefully ejected outflows, resembling the spread wings of a butterfly.
JWST and ALMA peer inside the dusty torus
Encircling the central white dwarf - still intensely hot from the lingering heat of its demise and transformation - is a dense, doughnut-shaped torus of dust. Matsuura and colleagues used the James Webb Space Telescope (JWST) to look into this dust and, in effect, identify what it is made from.
Dust blocks and scatters most wavelengths of light, but longer infrared wavelengths can pass through it, which makes JWST particularly well suited to investigating this puzzling region.
To build a fuller picture, the team paired JWST infrared observations with radio data from the Atacama Large Millimeter/submillimeter Array (ALMA). Together, these measurements exposed fresh detail about what is happening deep within the Butterfly Nebula.
From soot-like grains to silicate minerals
The researchers report that the dusty “doughnut” carries infrared fingerprints of both amorphous dust grains - more like soot - and orderly crystalline structures. The way the light glints also indicates the grains are comparatively large for dust, on the scale of micrometres, implying they have persisted there long enough to grow.
What the dust is made of is equally striking: it includes crystals of the silicate minerals forsterite, enstatite, and quartz.
Beyond the torus, the observations show a distinct layering in atoms and molecules. Ions that need the highest energies to form appear closer to the nebula’s centre, whereas ions that form with less energy are found more heavily farther out.
Jets, PAHs, and clues to life’s building blocks
The JWST data also reveal other notable structures: substantial jets of iron and nickel flowing away from the star in opposite directions, as well as a fairly pronounced abundance of polycyclic aromatic hydrocarbons (PAHs). That latter detection is especially intriguing.
PAHs are soot-like molecules built from rings of carbon atoms and are known to be widespread in space. As a result, they feature prominently in ideas about how carbon-based life could originate. Detecting them at the core of the oxygen-rich Butterfly Nebula provides new hints about how life’s building blocks might arise - specifically when powerful winds from the star crash into surrounding material.
Why this matters for the Solar System
We cannot run the Solar System backwards to watch how a cloud of material in space assembled into the planets we see today. However, tools such as JWST, and targets such as the Butterfly Nebula, offer scientists vital evidence for piecing together how we came to exist - starting with dust created by a dying star.
The research has been published in The Monthly Notices of Royal Astronomical Society.
Comments
No comments yet. Be the first to comment!
Leave a Comment