ASTR 4B Exam 2
Which of the following statements best describes the two principle advantages of telescopes over eyes?
Telescopes can collect far more light with far better angular resolution.
How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope?
The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope.
What is the name for the period of time from 1645 to 1715 when the solar cycle shut down?
The Maunder minimum
Consider an atom of gold in which the nucleus contains 79 protons and 118 neutrons. What is its atomic number and atomic mass number?
The atomic number is 79, and the atomic mass number is 197.
if we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet?
The planet is rotating
True or false: The chromosphere is the layer of the Sun that we see as its visible surface
false
Based on its surface temperature of 5,800 K, what color are most of the photons that leave the Sun's surface?
green
At the center of the Sun, fusion converts hydrogen into
helium, energy, and neutrinos
The core of the Sun is
hotter and denser than the surface
What is the Sun mainly made of?
hydrogen and helium
Which of the following are plotted on the vertical and horizontal axes of the H-R diagram?
luminosity and surface temperature
Hydrogen fusion in the Sun requires a temperature (in Kelvin) of
millons of degrees
A gas heated to millions of degrees would emit
mostly X rays.
How does the Sun generate energy today?
nuclear fusion
The Sun's surface, as we see it with our eyes, is called the
photosphere
The phase of matter in the Sun is
plasma
In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate?
radio
True or false: Grass is green because it absorbs green light, reflecting all other colors.
false
Temperature of the core of the sun:
10 million K
Suppose you measure the parallax angle for a particular star to be 0.1 arcsecond. The distance to this star is
10 parsecs
An atom of the element iron has an atomic number of 26 and an atomic mass number of 56. If it is neutral, how many protons, neutrons, and electrons does it have?
26 protons, 30 neutrons, 26 electrons
The Sun's average surface (photosphere) temperature is about
5800 K
Why do the most massive stars have the shortest lifetimes?
Because they use up their fuel far faster than smaller stars do.
The largest effective telescope, created by radio interferometry, is the size of
Earth
Our Sun is a star of spectral type
G2
What is the purpose of interferometry?
It allows two or more small telescopes to achieve the angular resolution of a much larger telescope.
What is the purpose of adaptive optics?
It reduces blurring caused by atmospheric turbulence for telescopes on the ground.
True or false: Any object moving relative to Earth will have a Doppler shift when viewed from Earth.
false
How can an electron in an atom lose energy to go from a higher energy level to a lower energy level?
It releases a photon equal in energy to its own energy drop.
According to the inverse square law of light, how will the apparent brightness of an object change if its distance to us doubles?
Its apparent brightness will decrease by a factor of 4
What do astronomers mean by light pollution?
Light pollution refers to lights from human sources that make it difficult to see the stars at night.
The spectral sequence in order of decreasing temperature is
OBAFGKM
The Chandra X-ray Observatory must operate in space because
X rays do not penetrate Earth's atmosphere.
If we say that a material is opaque to ultraviolet light, we mean that it
absorbs ultraviolet light
If you heat a gas so that collisions are continually bumping electrons to higher energy levels, when the electrons fall back to lower energy levels the gas produces
an emission line spectrum
What 2 wavelength regions cannot be studied with telescopes on the ground?
both ultraviolet and x rays
From center outward, which of the following lists the "layers" of the Sun in the correct order?
core, radiation zone, convection zone, photosphere, chromosphere, corona
When an electron in an atom goes from a higher energy state to a lower energy state, the atom
emits a photon of a specific frequency
True or False Gravitational equilibrium means that the surface and the core of the Sun are at the same pressure
false
True or false A radio telescope and an optical telescope of the same size have the same angular resolution.
false
Without telescopes or other aid, we can look up and see the Moon in the night sky because it
reflects visible light
If the distance between us and a star is doubled, with everything else remaining the same, the luminosity
remains the same, but the apparent brightness is decreased by a factor of four
Suppose you put two protons near each other. Because of the electromagnetic force, the two protons will?
repel eachother
What term is given to a pair of stars that we can determine are orbiting each other only by measuring their periodic Doppler shifts?
spectroscopic binary
The spectral sequence sorts stars according to
surface temperature
What two physical processes balance each other to create the condition known as gravitational equilibrium in stars?
the gravitational force and outward pressure
A star's luminosity is the
total amount of light that the star radiates each second
If a material is transparent, then it
transmits light well
True or False: Lines of a particular element appear at the same wavelength in both emission and absorption line spectra.
true
True or False: X rays from astronomical objects can only be detected from telescopes in space.
true
True or false Most astronomical objects emit light over a broad range of wavelengths.
true
True or false: The more distant a star, the smaller its parallax angle
true
True or false: You are currently emitting electromagnetic waves.
true
true or false A magnitude 10 star is fainter than a magnitude 9 star
true
true or false If the distance between us and a star is doubled, the apparent brightness is decreased by a factor of four
true
The stars in our sky twinkle in brightness and color because of
turbulence in Earth's atmosphere
Which of the following terms is given to a pair of stars that appear to change positions in the sky, indicating that they are orbiting one another?
visual binary
What are the standard units for luminosity?
watts
