AST 2002 Lecture Notes - Lecture 30: Electromagnetism, Molecular Cloud, Nuclear Fusion
Document Summary
Stars are born deep in molecular clouds. Gravity overcomes thermal pressure in dense regions. These regions (cores) become denser and compact. Something happens to perturb a molecular cloud and make it begin to fragment. As a core of gas collapses, it heats up. Protostar- collapses cloud of gas and dust. The protostar collapses until its core reaches 107 k in temperature. The first scientific theories involved chemical reactions or gravitational collapse. Chemical burning ruled out it (cid:272)a(cid:374)(cid:374)ot a(cid:272)(cid:272)ou(cid:374)t fo(cid:396) the su(cid:374)"s lu(cid:373)i(cid:374)osity. Conversion of gravitational potential energy into heat as the sun contracts would only keep the sun shining for 25 million years. Late 19th century geological research indicated the earth was older then that. Development of nuclear physics led to the correct answer. The sun generates energy via nuclear fusion reactions. Hyd(cid:396)oge(cid:374) is (cid:272)o(cid:374)(cid:448)e(cid:396)ted i(cid:374)to heliu(cid:373) i(cid:374) the su(cid:374)"s (cid:272)o(cid:396)e. The mass lost in this conversion is transformed into energy.
