How does density divide the stars in the H-R diagram into three groups?
What will be an ideal response?
Density divides stars into three groups. Most stars are main-sequence stars with densities like the Sun's. Giants and supergiants are very-low-density stars, and white dwarfs are high-density stars.
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Although all the known stars rise in the east and set in the west, we might someday discover a star that will rise in the west and set in the east.
a. Although all the known stars rise in the east and set in the west, we might someday discover a star that will rise in the west and set in the east. Choose the correct explanation why does the statement above make sense (or is clearly true) or does not make sense (or is clearly false). b. This statement does not make sense. The stars appear to rise and set because of Earth's rotation. So, during the day, all the stars must move in the same direction. c. This statement makes sense. The star appear to rise and set because of the sum of Earth's rotation and changing the seasons. So, in the night of solstice, the North Star could move in the opposite direction to other stars. d. This statement makes sense. The North Star itself does not appear to move usually, but sometimes the precession occurs. Precession changes the tilt of Earth's axis and could make the North star set in east or rise in west. e. This statement does not make sense. The stars moves because of the Galaxy's rotation around it center. So, during the day, al the stars must move in the same direction.
Stellar parallax occurs in much the same way as parallax on Earth, with greater parallax for stars that are nearer. Return to the main "Parallax" screen, and from here select the "Stellar Parallax" button, and watch how the motion of the star changes in the "View from Earth" window. Which statement best summarizes why stellar parallax occurs?
A. We view nearby stars from different positions in Earth's orbit at different times of year. B. We view nearby stars from different positions on Earth as Earth rotates on its axis. C. Nearby stars move in tiny circles as Earth orbits the Sun. D. Nearby stars move at higher speeds relative to the Sun than more distant stars.
Light of wavelength 550. nm in air is found to travel at 1.96 × 108 m/s in a certain liquid
(a) Determine the index of refraction of the liquid. (b) Determine the frequency of the light in air.
Why is the possible contamination of the Earth by Martian microbes in a future sample return mission not considered to be a significant problem?
A) Martian microbes will certainly be destroyed by terrestrial microbes B) any Martian microbes will be destroyed by high-energy particles and radiation on their trip back to Earth C) Martian microbes will be rapidly destroyed by oxygen in the Earth's atmosphere D) Martian microbes are likely to be quite different than terrestrial microbes and, hence, will probably not be able to affect life on Earth