During stage 3 of star formation, the dense, opaque region at the center of the cloud is called a:
A) Herbig-Haro object.
B) T Tauri star.
C) protostar.
D) protoplanetary nebula.
E) zero-age main sequence star.
A
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A device that transforms mechanical energy into electrical energy is a
A) generator. B) motor. C) transformer. D) magnet. E) none of the above
By definition, our Sun has a mass-to-light ratio of 1 solar mass per solar luminosity
Indicate whether the statement is true or false
The location of the Galactic Center was first found by Harlow Shapley with
A) radio emissions from Sagittarius A. B) RR Lyrae variables in the globular clusters. C) Cepheids of population I in the spiral arms. D) infrared observations of the heat from its accretion disk around the black hole. E) planetary nebulae in the open clusters.
The microwave in the kitchen has a label that indicates it produces its microwaves at a frequency of 2450 MHz. What is the energy associated with one of these microwave photons? (h = 6.63 × 10^?34 J?s)
a. 3.19 × 10^–2 eV b. 2.45 eV c. 1.02 × 10^–5 eV d. 1.62 eV