the.com/protoplanetarydisk
a newborn star's leftover pancake batter, slowly clumping itself into worlds.
means a rotating disk of gas and dust around a young star, the raw material from which planets eventually form.
from from Greek protos (first) and planetes (wanderer), coined as astronomers realized the flattened clouds seen around infant stars were literal planet nurseries, not just stellar leftovers.
lifespanmost disperse within 5 to 10 million years
gravity assistdisk's own gravity clumps dust into pebbles first
visibilityimaged directly only since telescopes like alma arrived
leftoversour asteroid belt is a fossil of one
for instance
hl tauri — alma's 2014 image showed clear rings, planets already carving gaps
beta pictoris — nearby young disk, directly imaged planet beta pic b orbiting inside it
tw hydrae — faces us nearly pole-on, giving astronomers a rare top-down view
solar nebula — our own sun's 4.6 billion year old disk, now just eight planets