Today's CO2 abundance is approximately ________ times the average value over the last 800,000 years.
A) 18
B) 1.8
C) 1.18
D) 0.18
B) 1.8
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At what two celestial locations do the celestial equator and ecliptic coincide?
a. winter solstice and summer solstice b. vernal equinox and autumnal equinox c. they coincide at all points because they are the same. d. north celestial pole and south celestial pole e. zenith and east point
Quasar spectra often show many absorption lines that all appear to be as a result of the same electron transition (such as level 1 to level 2 in hydrogen) but that fall at different wavelengths in the spectrum. Why do we think this is the case?
A) We are seeing absorption lines from clouds of gas that lie between us and the quasar, and therefore each cloud has a different redshift. B) Quasars are rotating rapidly, and this rotation produces spectral lines with a wide variety of Doppler shifts. C) The lines fall at different wavelengths because they are produced by different chemical elements. D) No one knows; it remains perhaps the greatest mystery about quasars.
If luminosity depends on radius and temperature, what does flux depend on? _______________
Fill in the blank(s) with correct word
Very massive stars lose their outer layers in a planetary nebula
a. True b. False Indicate whether the statement is true or false