Models of the first star-forming clouds indicate that they had a temperature of roughly 180 K and a particle density of roughly 3.00×105 particles per cubic centimeter at the time they started trapping their internal thermal energy. Part A Estimate the mass at which thermal pressure balances gravity for these values of pressure and temperature. Mcloud = nothing kg Request Answer Part B How does that mass compare with the Sun's mass? Mcloud = nothing ⋅MSun Request Answer Part C What is the estimated lifetime of a star with that mass? Choose the answer that best fits your estimate Choose the answer that best fits your estimate About 10 billion years Greater than 10 million years Less than 10 million years About 1000 years

Which of the following harmful chemicals are found in tobacco smoke? a. carbon monoxide b. carbon dioxide c. nicotine b. carbon dioxide d. both a and c

Some material consisting of a collection of microscopic objects is kept at a high temperature. a photon detector capable of detecting photon energies from infrared through ultraviolet observes photons emitted with energies of 0.3 ev, 0.5 ev, 0.8 ev, 2.0ev, 2.5ev, and 2.8ev. these are the only photon energies observed. (a) draw and label a possible energy-level diagram for one of the microscopic objects, which has four bound states. on the diagram, indicate the transitions corresponding to the emitted photons. explain briefly. (b) would a spring–mass model be a good model for these microscopic objects? why or why not? (c) the material is now cooled down to a very low temperature, and the photon detector stops detecting photon emissions. next, a beam of light with a continuous range of energies from infrared through ultraviolet shines on the material, and the photon detector observes the beam of light after it passes through the material. what photon energies in this beam of light are observed to be significantly reduced in intensity (“dark absorption lines”)? explain briefly.

The star betelgeuse is about 600 light-years away. if it explodes tonight, a. we'll know because debris from the explosion will rain down on us from space. b. we'll know it immediately because it will be brighter than the full moon in the sky. c. we won't know about it until 600 years from now. d. none of the above.