Giant molecular cloud

Assembled from 15 blocks · 2 evidence · 15 related

1. Story
2. A cold, dense region of the interstellar medium in which hydrogen exists as H2 rather than as atoms, and the only environment in which stars are known to form. Typical temperatures are around 10 to 20 K and giant complexes contain on the order of ten thousand to a million solar masses of gas and dust spread over tens of parsecs. A cloud does not collapse simply because it is massive: turbulence and magnetic fields provide most of the support on large scales, and thermal pressure dominates only in the densest cores. Collapse begins where a region exceeds the Jeans mass for its temperature and density, which is why star formation is patchy and clustered rather than uniform. Crucially, the cloud is not primordial material: its carbon, oxygen and iron were made inside earlier generations of stars, so every new star is assembled from the debris of dead ones. Not a place on Earth.
3. Knowledge
4. Giant molecular cloud
5. Connections
6. Eagle Nebula (Messier 16) and the Pillars of Creation
7. Protostar
8. Planetary nebula
9. Supernova
10. The first stars form from metal-free gas
11. The Sun forms and settles onto the main sequence
12. Hubble photographs the Pillars of Creation
13. Evidence
14. Supports typical molecular cloud temperatures near 10 K, giant complex masses of order 10^4-10^6 solar masses, and the statement that turbulence and magnetic fields dominate support on large scales while thermal pressure dominates in dense cores. Neither source was fetched; cloud lifetimes remain actively debated in the literature.
15. Establishes stellar nucleosynthesis as the origin of the elements heavier than helium and organises production into distinct nuclear processes including slow and rapid neutron capture. Title, authors, journal, volume and pages were read from ADS and publisher listings via search; the review itself was not fetched, so the internal process taxonomy is described from secondary accounts.