Astronomy 101 Midterm 1 – Flashcards
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A solar eclipse can occur only when the
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Moon comes between the Earth and the Sun.
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A lunar eclipse does not occur at every full Moon because the
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plane of the Moon's orbit is at an angle to the plane of the Earth's orbit.
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An observer can see a total solar eclipse from within a narrow band along Earth's surface. This band
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can begin almost anywhere on Earth's surface.
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Winter in the northern hemisphere occurs when
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sunlight falls with the greatest slant on that region of the Earth
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A comet that is moving southward from the north celestial pole toward the equator can be described as having its
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declination decrease with time.
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If a modern astronomer describes a faint star as being in the constellation Cygnus, the Swan, you know that the star is
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somewhere within a particular region of sky having definite boundaries
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Why do we see different phases of the Moon?
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The illuminated half of the Moon becomes more or less visible from Earth as the Moon orbits the Earth
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By how many powers of ten is the diameter of the Sun (1.4 × 105 km) greater than the length of a beetle (14 mm)?
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10
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A full Moon will always be at its highest in our sky at about
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midnight
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The number 50,000 is written in powers-of-ten notation as
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5 × 10^4.
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A distant asteroid is discovered that takes 50 years to orbit the Sun once. According to Kepler's third law, what is the average distance of this asteroid from the Sun?
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13.6 AU (cube root of 2500)
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How was the planet Neptune discovered?
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Neptune was discovered by mathematical prediction using Newton's laws.
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Kepler's second law states that a planet moves fastest when it
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is closest to the Sun.
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An object is in an orbit caused by its gravitational attraction to the Sun. This orbit
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might be an ellipse, a parabola, or a hyperbola.
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A force can give a certain mass a certain acceleration. If I double the force and double the mass, the acceleration of this object will be
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the same as the original acceleration.
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In Newton's law of universal gravitation, F = GMm/R^2, which defines the force between Earth with mass M and an orbiting satellite of mass m at a distance R from Earth, G
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is a constant, throughout all measured space and time.
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Why do astronomers need special units, in addition to the metric system of units such as meters and kilograms, to describe the universe?
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Distances and masses are very large, and representing them in metric units is cumbersome.
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Many of the extra-solar system planets discovered thus far contain large planets orbiting close to their stars. It is considered unlikely to find habitable Earth-like planets in such systems. What is the reason?
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The gravitational effects of these large planets would cause Earth-like planets to move into highly elliptical orbits and that would result in large temperature variations.
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A person orbiting the Earth in the Space Shuttle feels weightless because
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only one force (gravity) acts on her, but gravity also accelerates the Shuttle, so the Shuttle does not push up on her to create the feeling of weight.
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According to Newton's third law, if a force is acting on an object, then
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there must be some other force acting on a different object, with the same magnitude but in the opposite direction
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1 nanometer (nm) is
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10^-9 m.
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All forms of light have what property in common?
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All forms of light are electromagnetic radiation.
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Approximately how long does it take light to travel from the fingertips of your extended arm to your eye?
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2.5 billionths of a second (2.5 nanoseconds)
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A scientist reports the detection of an atomic particle known as a cosmic ray that came toward his experiment from outer space at a speed of 4 × 10^5 km/ s-1. What conclusion can we draw from this report?
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He made an error in his experiment because such a speed is considered to be impossible by all previous experiments.
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X rays and visible light are
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the same thing except that X rays have shorter wavelengths than visible light.
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A particular photon of ultraviolet (UV) light has a wavelength of 200 nm and a photon of infrared (IR) light has a wavelength of 2000 nm. What is the energy of the UV photon compared to that of the IR photon?
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The UV photon has 10 times more energy than the IR photon.
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Our present understanding of the nature of light is that it
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displays behavior of both waves and particles.
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What is the relationship between color and wavelength for light?
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Wavelength increases from violet to red.
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Visible light occupies what position in the electromagnetic spectrum?
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between infrared and ultraviolet
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An electrical spark, such as lightning, generates electromagnetic radiation over a wide range of wavelengths. How much longer will a pulse of radio energy take to travel between two detector stations 100 m apart than will a pulse of ultraviolet radiation from the same spark?
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The time will be identical because both pulses travel at the speed of light.
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How does the angular resolution of the 305-m Arecibo radio telescope in Puerto Rico compare with the angular resolution of the 10-m Keck optical telescope on Mauna Kea, Hawaii?
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The 305-m Arecibo telescope has much worse angular resolution than the 10-m Keck telescope.
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A refracting telescope is the type that uses, as its main optical element, a
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lens
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At what distance from the objective lens in a refracting telescope is the primary image formed—that is, at what distance would you place photographic film if you wanted to take a photograph?
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its focal length
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Which substance in the Earth's atmosphere is the main absorber of infrared radiation from space?
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water vapor
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How does angular resolution for a given diameter of telescope depend on wavelength?
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Angular resolution worsens as wavelength increases.
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A spherical mirror suffers from spherical aberration because
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different parts of the mirror focus the light at different distances from the mirror.
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A radio telescope
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is very similar to a reflecting optical telescope.
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A high mountaintop such as Mauna Kea in Hawaii is a good site for an infrared observatory primarily because it is
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above a significant proportion of the moisture in the Earth's atmosphere.
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As a light ray leaves a glass surface, traveling from the glass back into air at an angle to the surface, the light ray
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bends away from the perpendicular to the surface.
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Astronomy from space vehicles is particularly useful because the telescope
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is above the Earth's absorbing and distorting atmosphere and can measure radiation over a very wide wavelength range.
