ASTR 310 Lecture Notes - Lecture 4: Stellar Evolution

• School: Athabasca University
• Department: Astronomy and Astrophysics
• Course: ASTR 310
• Professor: reew

Document Summary

This indicates that there was no single epoch during which all the stars formed. Since massive stars exist today, they must have been created within the last several million years: current theories suggest that stars and planetary systems formed from clouds of dust and gas. Recent observations of stars surrounded by clouds of dust and gas support this idea, and indicate that the process is ongoing today. B(cid:895) suppose the (cid:373)ea(cid:374) de(cid:374)sity i(cid:374) this (cid:374)e(cid:271)ula is (cid:1005)(cid:1004)^-(cid:1010) kg/(cid:373)^(cid:1007). Is su(cid:272)h a (cid:374)e(cid:271)ula likely to p(cid:396)odu(cid:272)e pla(cid:374)ets of jupite(cid:396)"s size o(cid:396) s(cid:373)alle(cid:396) (cid:271)y pu(cid:396)ely g(cid:396)a(cid:448)itatio(cid:374)al (cid:272)ollapse: > 1. 25 10 5 kg/m3. If the density of the condensation is approximately 10 6 kg/m3, then the condensation is not dense enough to begin collapsing. There is simply not enough gravitational attraction to overcome the thermal energy of the condensation. In an infrared star the cocoon nebula is still present. The infrared radiation from this nebula is the dominant feature in the spectrum.