Explain how astronomers determine the size of an asteroid without resolving it
What will be an ideal response?
The brightness of an asteroid depends on its size, distance, and reflectivity. The brightness can be measured using a telescope, the distance is known from its orbit, and the reflectivity can be measured by comparing how bright the asteroid is at visible and infrared wavelengths. A highly reflective asteroid does not absorb much sunlight and is cooler than a darker asteroid. It will therefore shine less brightly at infrared wavelengths, relative to its visible brightness, than the dark asteroid. Once the reflectivity and size are known, the size can be determined from the asteroid brightness: for a given reflectivity and distance, the brightness depends on how large the asteroid is.
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If all the "dark matter" in the Universe were somehow instantaneously removed, which of the following would happen?
A) The Solar System would fly apart. B) All the stars in the Milky Way would collapse into the central black hole. C) Clusters of galaxies would no longer be gravitationally bound together. D) Atoms would split into nuclei and free electrons.
The size and shape of a planet's orbit can be determined by
A) the Doppler technique. B) transit observations. C) spectral measurements. D) knowing the planet's mass by any technique and applying Newton's version of Kepler's third law. E) gravitational microlensing.
The rapid rotation of Uranus and its high inclination give the magnetosphere and its long extension a(n) _______________ shape
Fill in the blank(s) with correct word
Some light switches that glow in the dark after the lights are turned off employ
A) fluorescence. B) resonance. C) incandescence. D) all of the above E) none of the above