Astronomy 101 Midterm 1

Flashcard maker : Kaitlynn Baldwin
A solar eclipse can occur only when the
Moon comes between the Earth and the Sun.
A lunar eclipse does not occur at every full Moon because the
plane of the Moon’s orbit is at an angle to the plane of the Earth’s orbit.
An observer can see a total solar eclipse from within a narrow band along Earth’s surface. This band
can begin almost anywhere on Earth’s surface.
Winter in the northern hemisphere occurs when
sunlight falls with the greatest slant on that region of the Earth
A comet that is moving southward from the north celestial pole toward the equator can be described as having its
declination decrease with time.
If a modern astronomer describes a faint star as being in the constellation Cygnus, the Swan, you know that the star is
somewhere within a particular region of sky having definite boundaries
Why do we see different phases of the Moon?
The illuminated half of the Moon becomes more or less visible from Earth as the Moon orbits the Earth
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)?
10
A full Moon will always be at its highest in our sky at about
midnight
The number 50,000 is written in powers-of-ten notation as
5 × 10^4.
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?
13.6 AU (cube root of 2500)
How was the planet Neptune discovered?
Neptune was discovered by mathematical prediction using Newton’s laws.
Kepler’s second law states that a planet moves fastest when it
is closest to the Sun.
An object is in an orbit caused by its gravitational attraction to the Sun. This orbit
might be an ellipse, a parabola, or a hyperbola.
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
the same as the original acceleration.
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
is a constant, throughout all measured space and time.
Why do astronomers need special units, in addition to the metric system of units such as meters and kilograms, to describe the universe?
Distances and masses are very large, and representing them in metric units is cumbersome.
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?
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.
A person orbiting the Earth in the Space Shuttle feels weightless because
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.
According to Newton’s third law, if a force is acting on an object, then
there must be some other force acting on a different object, with the same magnitude but in the opposite direction
1 nanometer (nm) is
10^-9 m.
All forms of light have what property in common?
All forms of light are electromagnetic radiation.
Approximately how long does it take light to travel from the fingertips of your extended arm to your eye?
2.5 billionths of a second (2.5 nanoseconds)
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?
He made an error in his experiment because such a speed is considered to be impossible by all previous experiments.
X rays and visible light are
the same thing except that X rays have shorter wavelengths than visible light.
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?
The UV photon has 10 times more energy than the IR photon.
Our present understanding of the nature of light is that it
displays behavior of both waves and particles.
What is the relationship between color and wavelength for light?
Wavelength increases from violet to red.
Visible light occupies what position in the electromagnetic spectrum?
between infrared and ultraviolet
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?
The time will be identical because both pulses travel at the speed of light.
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?
The 305-m Arecibo telescope has much worse angular resolution than the 10-m Keck telescope.
A refracting telescope is the type that uses, as its main optical element, a
lens
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?
its focal length
Which substance in the Earth’s atmosphere is the main absorber of infrared radiation from space?
water vapor
How does angular resolution for a given diameter of telescope depend on wavelength?
Angular resolution worsens as wavelength increases.
A spherical mirror suffers from spherical aberration because
different parts of the mirror focus the light at different distances from the mirror.
A radio telescope
is very similar to a reflecting optical telescope.
A high mountaintop such as Mauna Kea in Hawaii is a good site for an infrared observatory primarily because it is
above a significant proportion of the moisture in the Earth’s atmosphere.
As a light ray leaves a glass surface, traveling from the glass back into air at an angle to the surface, the light ray
bends away from the perpendicular to the surface.
Astronomy from space vehicles is particularly useful because the telescope
is above the Earth’s absorbing and distorting atmosphere and can measure radiation over a very wide wavelength range.

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