What observations suggest the mass of the Galaxy goes much farther out than its visible disc?
A) the rotation curve of the outermost portions of the disc
B) 21-cm maps of the spiral arms
C) infrared observations of distant brown dwarfs
D) the orbits of the open clusters in the disc
E) X-ray images of other galaxies' discs from Chandra
A
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What important molecules of life did Miller and Urey brew up?
A) RNA B) fatty acids C) lean acids D) amino acids E) antacids
What is the one piece of evidence that suggests that the dinosaurs were made extinct by the impact of an asteroid 65 million years ago?
A) the crater from this impact can still be seen in the deserts of Arizona B) a layer of sediment laid down at that time contains grains of shocked quartz, solidified rock droplets, and soot from global wildfires C) a layer of sediment laid down at that time is littered with dinosaur fossils D) dinosaur fossils are found in rock layers older than 65 million years but not younger than 65 million years
Considering both longevity and luminosity, which of these stars would be the most likely candidate for seeking extraterrestrial intelligence?
A) Spica, a B3 main-sequence star B) Sirius B, a white dwarf C) Antares, a M3 supergiant D) 61 Cygni, a K2 main-sequence star E) Barnard's star, a M5 dwarf
A sealed container holds 0.020 moles of ideal nitrogen (N2 ) gas, at a pressure of 1.5 atm and a temperature of 290 K
The atomic mass of nitrogen is 14.0 g/mol. How many molecules of nitrogen are in the container? (R = 8.31 J/mol ? K, 1 atm = 101 kPa) A) 1.5 × 1021 mol B) 3.0 × 1021 mol C) 6.0 × 1021 mol D) 1.2 × 1022 mol E) 2.4 × 1022 mol