Protostar

Assembled from 37 blocks · 2 evidence · 30 related

1. Story
2. A collapsing cloud core that has become opaque to its own radiation and is now heated by gravitational contraction rather than by fusion. It accretes through a disc, drives bipolar jets that clear the surrounding envelope, and shrinks along a track toward the main sequence over a period that is strongly mass-dependent - on the order of tens of millions of years for a solar-mass star and vastly shorter for a massive one. A protostar becomes a star only when the core reaches the temperature at which hydrogen fusion supplies the entire radiated luminosity, at which point contraction stops. An object below roughly 0.07 to 0.08 solar masses never reaches that condition and becomes a brown dwarf instead; the exact threshold depends on composition and is quoted between about 0.07 and 0.09 solar masses in the literature. Not a place on Earth.
3. Knowledge
4. Initial stellar mass
5. Giant molecular cloud
6. Protostar
7. Main sequence (core hydrogen burning)
8. Connections
9. Initial stellar mass
10. Giant molecular cloud
11. Main sequence (core hydrogen burning)
12. The Sun forms and settles onto the main sequence
13. Hubble photographs the Pillars of Creation
14. Hydrogen fusion: the proton-proton chain and the CNO cycle
15. Main sequence (core hydrogen burning)
16. Supernova
17. Protostar
18. The first stars form from metal-free gas
19. SN 1987A: neutrinos from a collapsing core reach Earth
20. Eagle Nebula (Messier 16) and the Pillars of Creation
21. Protostar
22. Planetary nebula
23. Supernova
24. The first stars form from metal-free gas
25. The Sun forms and settles onto the main sequence
26. Hubble photographs the Pillars of Creation
27. Initial stellar mass
28. Protostar
29. Red giant and asymptotic giant branch
30. Hydrogen fusion: the proton-proton chain and the CNO cycle
31. The Sun
32. Hertzsprung-Russell diagram
33. The Sun forms and settles onto the main sequence
34. Hertzsprung and Russell independently plot luminosity against temperature
35. Evidence
36. 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.
37. Supports a hydrogen-burning mass limit near 0.07-0.075 solar masses at solar composition, rising toward about 0.09 solar masses at low metallicity. The paper was not fetched; the values come from its abstract as reproduced in a search summary.