# Astronomy 1

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6,000 joules

### the frequency of a wave is?

measured in hertz, the number of peaks passing by a point each second, measured in cycle per second and equal to the speed of the wave divided by the wavelength.

### how are wavelength, frequency and energy related to photons of light?

longer wavelength means, lower frequency and lower energy

### which of the following statements about xrays and radio waves is not true?

xrays travel through space faster than radio waves.

### an electron-volt is?

an amount of energy much smaller than a joule

### if you heat a gas so that collisions are continually bumpign electrons to higher energy levels whne the electrons falls back to lower energy levels the gas produces?

an emission line spectrum

### when an electron in an atom goes from a higher energy state to a lower energy state, the atom?

emits a photon of specific frequency.

### when white ligth passes through a cool cloud of glass we see?

an absoprtion line spectrum

### which of the following statements about thermal radiation is always true?

a hot object emits more total radiation per unit surface area than a cool object

### you observe the same spectral line in two stars that are identical in every way except that one rotates faster than the other. How does the spectral line differ between the two?

the line in the faster rotating star is broader

### what is the difference between energy and power

power is the rate at which energy is used, so its units are a unit of energy divided by a unit of time.

### suppose you know the frequency of a photon and the speed of light. What else can you determine about the photon?

its wavelength and energy.

photons

### from shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation.

gamma ray, x-ray, ultraviolet visible light, infrared, radio

### thermal radiation is defined as

radiation with a spectrum that depends only on the emitting object's temperature

### according to the laws of thermal radiation, hotter objects emit photons with

A shorter average wavelength.

### Suppose you want to know the chemical composition of a distant star. Which piece of info is the most useful to you?

the wavelengths of spectral lines in the star's spectrum

### the spectra of most galaxies show redshifts, this means their spectral lines are

have wavelengths that are longer than normal

### laboratories show hydrogen produces a spectral line at a wavelength of 486.1 nanometers. A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude?

the star is moving toward us

infrared.

### which two are the basic premises for the special theory of relativity

1. the laws of nature are the same for everyone
2. the speed of light is the same for everyone

### which of the following is not a prediction made by the theory of relativity

observers in different reference frames may disagree about the basic laws of nature.

### in relativity, two people share the same frame of reference only if

they are not moving relative to each other

### bob is coming toward you at a speed at 75km/hr, you throw a baseball at Bob at 75km/hr, what does he see the ball doing?

he sees the ball coming at him at 150km/hr

### if you see jackie going to your left at exactly .99c and bob going to your right at exactly .99c, jackie will say that bob is

going away from her faster than .99c, but slower than c

### a spaceship is headed toward alpha centauri at .999c, according to us, the distance of alpha centauri is about 4 light-years. how far is alpha centauri according to the travelers in the ship?

quite a bit less than 4 light-years

### a spaceship is moving past us at close to the speed of light: how would we view time as it goes by one the ship?

their clocks are moving slower than ours.

### a spaceship is moving past us at close to the speed of light:if we could measure the mass of a ship as it passes by what would it be?

its mass is greater than its rest mass

### a spaceship is moving past us at close to the speed of light:how would the passengers on the spaceship view our clocks

our clocks are going slow

### how does the explosion of the nuclear bomb provide evidence of the theory of relativity?

the bomb produces energy in accord with E = mc^2, which is part of the theory of relativity.

### A man is moving past you at close to the speed of light, which of the following accurately describes the effects on mass, size and time?

his mass would be increased from its value at rest, his lenght would be decreased by his value at rest but only from the direction in which he is moving, and his time would be running slower than yours.

### why do the predicted consequences of the special theory of relativity seem so strange to us?

because they are obviously only at speeds that we never experience in our daily lives

### in the late 1800s helmholtz and kelvin suggested that the sun stayed hot due to gravitational contraction. What was the major drawback of this theory?

it predicted the sun could only last 25 million years, which is far less than the age of the Earth

### what do we mean when we say the sun is in gravitational equilibrium?

there is a balance within the sun between the outward push of pressure and inward pull of gravity

### What is the sun made of?

70 percent hydrogen, 28 helium, and 2 percent other elements

watts

6,000K

10 million K

### from the center outward, which of the following lists the sun's layers in the correct order?

core, radiation zone, convection zone, photosphere, chromosphere, corona

photosphere

### the core of the sun is

hotter and denser than the surface

### why do sunspots appear darker in pictures of the sun?

they are actually fairly bright they just appear darker vs the even brighter surface of the surrounding sun

nuclear fusion

### at the center of the sun, fusion converts hydrogen into

helium, energy and neutrinos

repel each other

### the first step in proton-proton chain produces an antielectron or positron, what happens to the positron?

it is rapidly converted to energy when it meets an ordinary electron, resulting in matter-antimatter annihilation

### the overall fusion reaction buy which the sun creates energy is

4H=->1He + energy

### which statement best describes the solar neutrino problem?

solar neutrinos have been detected , but in fewer numbers than predicted by theoretical models

### why are neutrinos so hard to detect

because they rarely have contact with matter

### what is a possible solution to the neutrino problem

the neutrinos created in the sun change into different neutrinos that we can't detect

### what happens to energy the sun creates in the convection zone

energy is transported outward by the rising of hot plasma and the sinking of cooler plasma.

### most of the energy produced in the sun is released in the form of visible light from the photosphere. however some energy is released from upper layers of the solar atomsphere. what best describes where the other forms of light are released

the chromosphere is a source of UV light and the corona is the source of xrays

### what is granulation in the sun?

the bubbling pattern on the photosphere produced by underlying convection

### what processes are involved in the sunspot cycle

the winding of magnetic fields lines due to differential rotation

### what observations characterize solar maximum

we see many sunspots on the surface

### since stars begin their lives with the same basic composition what characteristics decide how they will differe

mass they are formed with

watts

### a star's luminosity is

total amount of light a star radiates at each second

### what are the standard units for apparent brightness

watts per square meter

### if the distance between us and the 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

### why do astronomers measure the visible-light apparent brightness instead of the total apparent brightness of a star

longest answer...measuring brightness in all wavelengths is too hard to do.

10 parsecs away

100 parsecs away

### the spectral sequence sorts stars according to

surface temperature

OBAFGKM

### why is the spectral sequence of stars not in alphabetical order

the original alphabetical order didn't correspond to temp so it had to be redone

all are true

### 2 stars, same spectral line type

star 1 is 10 times

visual binary

### which term is given to a pair of stars that indicate they orbit each other only via their periodic Doppler shifts

spectroscopic binary

lower right

upper right

upper right

lower left

upper right

### you observe a star in the disk of the milky way you want to plot the star on the H-R diagram you will need to determine everything except

rotation rate of the star

### on the main sequence stars obtain their energy

by converting hydrogen to helium

10 billion years

### whihc is true about low-mass stars as compared to high-mass stars

low mass stars are cooler and less luminous than high mass stars

V

### an open cluster is...

alll stars in the cluster are approximately the same age

### cluster ages can be determined from

main sequence turnoff

Example: