Briefly discuss the gas-stars-gas cycle
What will be an ideal response?
During a star's lifetime, it fuses hydrogen into helium and helium into carbon. If it is more massive, it also creates heavier elements, up to iron, by fusion, and even heavier elements during a supernova event. When the star ends its life as a planetary nebula or in a supernova explosion, it disperses these elements into the interstellar medium. The interstellar medium thus gains these heavier elements and has a smaller proportion of hydrogen but a larger proportion of heavier elements than it did before. The newly added material to the interstellar medium cools, forms molecular clouds, and then forms new stars, which are now made out of material in the interstellar medium with a larger heavy element content. These stars evolve and the cycle continues.
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High-mass stars become ________ variables when they cross the instability strip, while low-mass stars become ________ variables.
A. RR Lyrae; Cepheid B. T Tauri; Cepheid C. Cepheid; RR Lyrae D. Cepheid; T Tauri E. ZZ Ceti; RR Lyrae
A 1.5m long, 0.75kg dowel is pivoted about the end so that it is a pendulum of sorts - it can freely swing in a vertical plane. At the other end of the dowel is a brass weight having mass 1.5kg. (The center of the brass weight is 1.5m from the pivot point. When the rod is positioned in its swing such that its angle with the vertical is 22.5 degrees, what is the net torque on the rod about the pivot?
A. 11 Nm B. 28 Nm C. 9.5 Nm D. 25 Nm
The cosmic speed limit, the speed of light is established by
A) Newton's Laws of Motion B) Einstein's General Theory of Relativity C) Einstein's Special Theory of Relativity D) Kepler's Laws of Planetary Motion
An alpha particle is like with 2 protons and 2 neutrons, whereas a beta particle is equivalent to hydrogen
a. True b. False Indicate whether the statement is true or false