Practice problem(s):

You observe a binary star system where the two stars are exactly the same temperature. The diameter of one star is 1.2 times the diameter of the second star.  How many times more energy is emitted by the brighter star?

Answer: 1.44x

You observe a binary star system where the two stars are exactly the same size. One star is 5500 K. The other star is 6100 K.  How many times more energy is emitted by the brighter star?

Answer: 1.51x

What is the luminosity, in solar units, of a brown dwarf whose radius is 0.1 solar radii, and whose surface temperature is 600 K (0.1 times that of the Sun)?
Answer: 1.0x10-6 times.

How many magnitudes different is this?
Answer: 15 magnitudes higher.

PRS Quesitons:

Answers are at the end.


1) Which of these is not a form of electromagnetic radiation?

A) television signals

B) ultraviolet causing a suntan

C) light from your camp fire

D) DC current from your car battery

E) x-rays in the doctor's office


2) The speed of light in a vacuum is written as:

A) h = E/c.

B) v = 186,000 miles per hour.

C) v = 768 km/hour.

D) c = 300,000 km/sec.

E) not given


3) The radiation our eyes are most sensitive to lies in the color:

A) blue at 4,321 nanometers.

B) yellow-green at about 550 nm.

C) red at 6563 Angstroms.

D) black at 227 nm.

E) violet at 7,000 Angstroms.


4) The tendency of a medium to block transmission of a certain wavelength of radiation is referred to as its:

A) seeing.

B) opacity.

C) clarity.

D) transparency.

E) albedo.


5) Off the main sequence, Deneb is a luminous hot supergiant, so it is class:

A) M3V.

B) A2Ia.

C) B9V.

D) M3Ib.

E) K5V.


6) Which of these pairs of binaries would appear most similar in color telescopically?

A) F0V and G9III

B) M1V and K9V

C) A2Ia and F7Ia

D) O2V and M4Ia

E) F3IV and G8III


7) Which temperature will freeze water?

1:   65° F                      2:   5° C                       3:   263 K                   



8) Which feels hotter?

1:  300° F                     2:  300° C                    3:  300° K       



9) The relationship that the total energy radiated by a black body is proportional to T4 is attributed to?

1: Bunsen

2: Wien

3: Kirchhoff

4: Stefan


10) What kind of spectrum do we see from the sun?

A) a continuum with no lines, as shown by the rainbow

B) a continuum with emission lines

C) only absorption lines on a black background

D) a continuum with absorption lines

E) only emission lines on a black background


11) Which property of a black body is NOT true?

A) It appears black to us, regardless of its temperature

B) Its energy is in a continuum.

C) Its energy peaks at the wavelength determined by its temperature.

D) If its temperature is doubled, the peak in its curve would be halved in wavelength.

E) If its temperature doubled, it would give off 16 times more total energy.


12) A pulsating variable star has a temperature ranging from 4000 K to 8000 K.  When it is hottest, each cm2 of surface radiates how much more energy?

A) (sqrt2)x more

B) 2x more

C) 4x more

D) 16x more


13) The element first found in the Sun’s spectrum and then on Earth 30 years later is… 

A) hydrogen

B) helium

C) solarium

D) technicum


14) A source of light is approaching us at 3,000 km/s.  All its waves are:

A) Red shifted by 1%

B) Blue shifted by 1%

C) Not affected, as c is constant in all reference frames.

D) Red shifted out of the visible into the infrared

E) Blue shifted out of the visible into the ultraviolet


15) The temperature of the photosphere of the Sun is about:

A) 4500 K

B) 5800 K

C) 11000 K

D) 1 million K

E) 15 million K


16 )The Sun’s average density is about the same as:

A) the Earth’s Moon

B) the Earth

C) Haley’s Comet

D) Jupiter

E) Saturn


17) From inside out, which is the correct order?

A) core, convective zone, radiative zone

B) photosphere, radiative zone, corona

C) radiative zone, convective zone, chromosphere

D) core, chromosphere, photosphere

E) convective zone, radiative zone, granulation


18) Typically, a granule in the photosphere of the sun is about the size of?

A) A city, ~20-30 kilometers across.

B) Texas, ~1000 km across.

C) The Moon, ~3000 km across.

D) The Earth, ~12,000 km across.

E) Jupiter, ~100,000 km across.


19) What is the temperature of 150 C in Kelvin?

A) 212 K

B) 433 K

C) 413 K

D) 423 K

E) 522 K


20) A star's absolute magnitude is its apparent brightness as seen from:  

A) Pluto.

B) Alpha Centauri.

C) 10 light years distance.

D) 33 light years distance.

E) 100 parsecs distance.


21) Which is correct

1 :         velocity x frequency = wavelength

2 :         velocity x period = wavelength

3 :         period x frequency = wavelength

4 :         velocity / period = wavelength


22) A star of temperature 3,750K, just one step hotter than M (at 3,500), would be a related:

A) A9.

B) F5.

C) K9.

D) M1.

E) O3.


23) A star emits the most energy at a wavelength of 5.8x10-5cm.  What is its temperature?

A) 5800 K.

B) 2000 K.

C) 20000 K

D) 0.29 K.

E) 5000 K.


24) What energy transport gets the energy of the gamma rays to the Sun’s surface?

A) the transition zone

B) meson capture

C) the weak force

D) convection

E) prominences


25) The model of the atom with quantum leaps between electron orbitals is that of:

A) Albert Einstein.

B) Isaac Newton.

C) Neils Bohr.

D) Scott Bachula.

E) Wilhelm Kirchhoff.


26) That electromagnetic radiation can behave not only as a wave, but as a packet of energy, or a photon, is due to:

A) Enrico Fermi.

B) Edward Teller.

C) Neils Bohr.

D) Isaac Newton.

E) Albert Einstein.


27) The magnetic fields of sunspots are studied by the splitting of their spectral lines in the:

A) Doppler effect.

B) Stefan's law.

C) Zeeman effect.

D) Kirchhoffts third law.

E) Bohr model.


28) When we glimpse the chromosphere at the start and end of totality, its color is:

A) yellow, like the photosphere below it.

B) red, due to ionized hydrogen at lower pressure.

C) green (the famous flash).

D) blue, due to the ionization of nitrogen by the magnetic fields.

E) white from the moonlight.


29) The solar winds blow outward from:

A) the Sun's poles only.

B) flares.

C) the entire photosphere.

D) coronal holes.

E) sunspots.


30) In the proton-proton cycle, the positron is:

A) an anti-electron.

B) the chief means energy reaches the photosphere.

C) a spin conservation particle.

D) massless.

E) intermediate between the proton and neutron in mass.


31) The most striking example of solar variability was the:

A) Dust Bowl drought of the 1930s.

B) Sporer Minimum that doomed the Anasazi.

C) Joseph's seven lean years in the Old Testament.

D) Maunder Minimum from 1645-1715.

E) the fall of Rome.


32) The ESA satellite which gave us our best parallax measurements is:

A) Huygens.

B) Cassini.

C) Giotto.

D) Hipparcos.

E) Copernicus.


  33) If the rest wavelength of a certain line is 600 nm, but we observe it at 606 nm, then:

A) The source is approaching us at 6% of the speed of light.

B) The source is receding from us at 6% of the speed of light.

C) The source is receding from us at 1% of the speed of light.

D) The source is approaching us at 1% of the speed of light.

E) The source is getting 1% hotter as we watch.


34) A new star is discovered.  If we observe it with blue and yellow filters (separately), and find much more yellow intensity than blue, where would you expect the peak wavelength to be?

A) Red, or longer

B) Blue or shorter

C) Near the yellow

D)  Not enough information given.


35) If a star was the same size as our Sun, but was 16X more luminous, it must be:

A) three times hotter than the Sun.

B) 81 times hotter than the Sun.

C) four times hotter than the Sun.

D) nine times hotter than the Sun.

E) twice as hot as our Sun.



36) If a star has a parallax of .05", then its distance must be:

A) 5 parsecs.

B) 20 parsecs.

C) 25 parsecs.

D) 200 parsecs.

E) 500 parsecs.


37) If your naked eye limiting magnitude is 6.0, then using a pair of small binoculars, with about 15X the surface area of your pupil, which object would be near your new limiting magnitude?

A) seventh magnitude Titan, Saturn's largest moon

B) eighth magnitude Neptune

C) ninth magnitude Barnard's Star

D) eleventh magnitude Tethys, Saturn's second largest moon

E) thirteenth magnitude Pluto



Key:     D D B B B     B C B D D     A D B B B    D C B D D     B C E D C     E C B D A     D D C A E     B C


Chapter 11


1) Why are star clusters ideal "laboratories" for stellar evolution?

A) Their stars are all the same composition and stage in evolution.

B) The combined light of all the stars makes them easier to see.

C) Their stars are all about the same mass and temperature.

D) Their stars are all about the same age, composition, and distance from us.

E) Like our Sun, they lie in the plane of the Milky Way.


2) What are the characteristics of an open cluster?

A) no stars left on the main sequence, but millions of white dwarfs

B) a few hundred stars, most still on the main sequence

C) millions of stars, both young and old, spread out over 100,000 ly.

D) a star forming region, hundreds of light years across, with many blue main sequence stars

E) old age and tens of thousands of stars


3) Which is characteristic of globular star clusters?

A) only brown dwarfs in a yellow ball 100 ly across

B) bright blue main sequence stars, and thousands of them

C) no remaining main sequence stars, but millions of white dwarfs

D) old age and hundreds of thousands of stars, only about 30 ly wide

E) a mix of old and young stars, about 100,000 ly across


4) The most common molecule in a molecular cloud is:

A) carbon monoxide, with one carbon and an oxygen.

B) ammonia, with three hydrogens attached to a nitrogen.

C) molecular hydrogen, made of two H atoms.

D) methane, with four hydrogens around a hydrogen.

E) water, with two hydrogens around an oxygen.


5) What effect does even thin clouds of dust have on light passing through them?

A) It dims and reddens the light of all more distant stars.

B) Even a little can completely block all light, such as the Horsehead Nebula.

C) Its motion causes all light to be red shifted as it passes through these clouds.

D) Its motion causes the light of stars beyond to twinkle.

E) The light that passes through them is blue shifted due to the cloud's approach.


6) Interstellar gas is composed mainly of:

A) only hydrogen.

B) some hydrogen, but mainly carbon dioxide.

C) 10% hydrogen, 90% helium by numbers of atoms.

D) 75% hydrogen, 25% helium by weight.

E) ammonia, methane, and water vapor.


7) Why are dark dust clouds largely misnamed?

A) The cloud is an illusion, for the dust is evenly distributed around the Galaxy.

B) It is ice, not dust, which make them look dark.

C) Dust clouds do radiate energy, but not as much light as the stars do.

D) They contain much more gas than dust.

E) All of the above are correct.


8) Complex molecules in the inter-stellar medium are found:

A) uniformly throughout the disk of the Galaxy.

B) only around the supergiant stars like Betelguese that make their heavy atoms.

C) on the surfaces of the coolest class K and M stars only.

D) scattered evenly throughout the universe, a product of the Big Bang itself.

E) primarily in the dense dust clouds.


9) A cloud fragment too small to collapse into a main sequence star becomes a:

A) pulsar.

B) brown dwarf.

C) white dwarf.

D) planet of another star.

E) T Tauri object.


10) How long does it take an M class star to reach the main sequence, compared to a solar type star?

A) a tenth as long

B) longer than the age of the Galaxy

C) about twice as long

D) about twenty times longer

E) about the same, 30 million years


D B D C A   D D E B D

Chapter 12


1) The helium flash converts helium nuclei into

A) carbon

B) beryllium

C) oxygen

D) iron

E) boron


2) Which is used observationally to determine the age of a star cluster?

A) the number of white dwarfs

B) the total number of main sequence stars

C) the amount of dust that lies around the duster

D) the ratio of giants to supergiants

E) the luminosity of the main sequence turn-off point


3) In a white dwarf, we have packed the mass of the Sun into the volume of:

A) the Moon.

B) Jupiter.

C) Eros.

D) Earth.

E) Mars.


4) The brightest stars in a young open cluster will be:

A) red T-tauri stars still heading for the main sequence.

B) yellow giants like our Sun, but much larger.

C) the core stars of planetary nebulae.

D) massive blue stars at the top left on the H-R diagram.

E) red giants that are fusing helium into carbon.


5) A relatively peaceful mass loss as a giant core becomes a white dwarf is a:

A) emission nebula.

B) nova.

C) supernova remnant.

D) planetary nebula.

E) supernova.


6) What forces a star like our Sun to evolve off the main sequence?

A) It loses all its neutrinos, so fusion must cease.

B) It completely runs out of hydrogen.

C) It builds up a core of inert helium.

D) It explodes as a violent nova.

E) It expels a planetary nebula to cool off and release radiation.


7) A surface explosion when a companion spills hydrogen onto its close white dwarf companion creates a:

A) nova.

B) Type I supernova.

C) emission nebula.

D) Type II supernova.

E) planetary nebula.


8) For a white dwarf to explode entirely as a Type I supernova, it must weigh:

A) 20 solar masses, the Hubble Limit.

B) at least 8% as much as the Sun.

C) 1.4 solar masses, the Chandrasekhar Limit.

D) 3 solar masses, the Schwartzchild Limit.

E) 100 solar masses, the most massive known stars.


9) Of the elements in your body, the only one not formed in stars is:

A) aluminum.

B) carbon.

C) hydrogen.

D) iron.

E) calcium.


10) Which of these events is not possible?

A) close binary stars producing recurrent novae explosions

B) white dwarfs and companion stars producing recurrent Type I supernova events

C) red giants exploding as Type II supernovae

D) a white dwarf being found in the center of a planetary nebula

E) low-mass stars swelling up to produce planetary nebulae


A E D D D    C A C C B


Chapter 13

  1) A massive object, heavier than the Sun, which could fit inside a city, is a:

A) asteroid

B) white dwarf

C) neutron star

D) brown dwarf


2) If the Sun were replaced by a one solar mass black hole:

A) we would immediately escape into deep space, driven out by its radiation.

B) our clocks would all stop.

C) life here would be unchanged.

D) we would still orbit it in a period of one year.

E) all terrestrial planets would fall in immediately.


3) The largest known black holes

A) create the dark nebulae in the plane of the Milky Way.

B) can be no more than 1.4 solar masses, according to Chandrasekhar.

C) lie in the cores of the most massive galaxies.

D) can be no bigger than a small city, just like neutron stars.

E) can be no bigger than the earth, like white dwarfs.


4) Which of these does not exist?

A) a six solar mass black hole

B) a million solar mass black hole

C) a 1.8 solar mass neutron star

D) a .06 solar mass brown dwarf

E) a 1.5 solar mass white dwarf


5) While perhaps affected by rotation and magnetism, we think the lower limit for black holes is:

A) Hubble's limit of 30 solar masses.

B) Shapley's limit of 75 solar masses.

C) Chandrasekhar's limit of 1.4 solar masses.

D) Einstein's limit of 8 solar masses for high-mass stars.

E) Schwartzschild's limit of 3 solar masses.


6) Neutron stars have:

A) very strong bi-polar magnetic fields.

B) weak or non-existent magnetic fields.

C) periods of days or weeks.

D) monopolar fields that switch polarity every rotation.

E) no relation to pulsars.


C D C E E   A