Term
| What is interstellar reddening? |
|
Definition
| Interstellar dust absorbs more blue light than red light, making stars appear redder than their true color. |
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Term
| By mass, the interstellar medium in our region of the Milky Way consists of |
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Definition
| 70%hydrogen 28% helium and 2%heavier elements |
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Term
| The typical size of an interstellar dust grain is |
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Definition
| Microscopic, usually less than 1 micrometer across which is smaller than a single cell of bacteria. |
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Term
| If you wanted to observe a molecular cloud, in what wavelength of light would you most likely observe? |
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Definition
|
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Term
| The thermal pressure of a gas depends on |
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Definition
|
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Term
What prevents the pressure from increasing as a cloud
contracts due to its gravity? |
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Definition
| Thermal energy is converted to radiative energy via molecular collisions and released as photons. |
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Term
| What property of a molecular cloud does not counteract gravitational contraction? |
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Definition
|
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Term
| What is the likely reason that we cannot find any examples of the first generation stars? |
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Definition
| The first generation stars were mostly very massive and exploded as supernova. |
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Term
| Why do we think the first generation of stars would be different from stars born today? |
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Definition
| Without heavy elements, the clouds could not reach as low a temperature as today and had to be more massive to collapse. |
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Term
| What happens to the rotation of a molecular cloud as it collapses to form a star? |
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Definition
| The rotation rate increases and results in a disk of material around a protostar. |
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Term
| When does a protostar become a true star? |
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Definition
| when nuclear fusion begins in the core |
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Term
| What is the difference between brown dwarfs and Jupiter? |
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Definition
|
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Term
| No stars have been found with masses greater than 100 times our Sun because |
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Definition
| they would generate so much power that they would blow themselves apart. |
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Term
| Which of the following may be caused by a protostellar disk? |
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Definition
| Protostellar jets, Protostellar winds, Accretion of material onto the star, All of the above |
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Term
| What do astronomers mean when they say that we are all “star stuff”? |
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Definition
| that the carbon, oxygen, and many elements essential to life were created by nucleo synthesis in stellar cores |
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Term
| Which two energy sources can help a star maintain its internal thermal pressure |
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Definition
| nuclear fusion and gravitational contraction |
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Term
| What type of star is our Sun? |
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Definition
|
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Term
| What is the range of star masses for high‐mass stars? |
|
Definition
| between 8 and 100 solar masses |
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Term
| Which of the following statements about degeneracy pressure is not true? |
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Definition
| Degeneracy pressure can only be created by interactions among the electrons in an object. |
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Term
| What happens when a star exhausts its core hydrogen supply? |
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Definition
| Its core contracts, but its outer layers expand and the star becomes bigger and brighter. |
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Term
| At approximately what temperature can helium fusion occur? |
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Definition
|
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Term
| How many helium nuclei fuse together when making carbon? |
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Definition
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Term
| The helium fusion process results in the production |
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Definition
|
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Term
| What is a planetary nebula? |
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Definition
| It is a shell of gas ejected from a star late in its life. |
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Term
| What happens to the core of a star after a planetary nebula occurs |
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Definition
| It becomes a white dwarf. |
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Term
| Which of the following sequences correctly describes the stages of life for a low‐mass star? |
|
Definition
| protostar, main-sequence, red giant, white dwarf |
|
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Term
| Compared to the star it evolved from, a white dwarf is |
|
Definition
|
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Term
|
Definition
| a type of hydrogen fusion that uses carbon, nitrogen, and oxygen atoms as catalysts |
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Term
| Which element has the lowest mass per nuclear particle and therefore cannot release energy by either fusion or fission? |
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Definition
|
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Term
| Which event marks the beginning of a supernova? |
|
Definition
| the sudden collapse of an iron core into a compact ball of neutrons |
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Term
| Degeneracy pressure is the source of the pressure that stops the crush of gravity in all the following except |
|
Definition
| a very massive main-sequence star |
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Term
| White dwarfs are so called because |
|
Definition
| they are both very hot and very small. |
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Term
| A teaspoonful of white dwarf material on Earth would weigh |
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Definition
|
|
Term
| Why is there an upper limit to the mass of a white dwarf? |
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Definition
| The more massive the white dwarf, the greater the degeneracy pressure and the faster the speeds of its electrons. Near 1.4 solar masses, the speeds of the electrons approach the speed of light, so more mass cannot be added without breaking the degeneracy pressure. |
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Term
| What is the ultimate fate of an isolated white dwarf? |
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Definition
| It will cool down and become a cold black dwarf. |
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Term
| How does a 1.2‐solar‐mass white dwarf compare to a 1.0‐ solar‐mass white dwarf? |
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Definition
|
|
Term
| Which of the following is closest in size (radius) to a white dwarf? |
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Definition
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Term
| Observationally, how can we tell the difference between a white‐dwarf supernova and a massive‐star supernova? |
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Definition
| The spectrum of a massive-star supernova shows prominent hydrogen lines, while the spectrum of a white-dwarf supernova does not. |
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Term
| After a massive‐star supernova, what is left behind? |
|
Definition
| either a neutron star or a black hole |
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Term
| Which of the following is closest in size (radius) to a neutron star? |
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Definition
|
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Term
| From an observational standpoint, what is a pulsar? |
|
Definition
| an object that emits flashes of light several times per second or more, with near perfect regularity |
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Term
| What is the basic definition of a black hole? |
|
Definition
| any object from which the escape velocity equals the speed of light |
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Term
| How does the gravity of an object affect light? |
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Definition
| Light coming from a compact massive object, such as a neutron star, will be redshifted. |
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Term
| How does a black hole form from a massive star |
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Definition
| During a supernova, if a star is massive enough for its gravity to overcome neutron degeneracy of the core, the core will be compressed until it becomes a black hole. |
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Term
| A 10‐solar‐mass main‐sequence star will produce which of the following remnants? |
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Definition
|
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Term
| If you were to come back to our Solar System in 8 billion years, what might you expect to find? |
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Definition
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Term
| Black holes, by definition, cannot be observed directly. What observational evidence do scientists have of their existence? |
|
Definition
| Their effects on nearby light and matter (Gravitational interactions) |
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Term
| How do we know that pulsars are neutron stars? |
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Definition
| No massive object, other than a neutron star, could spin as fast as we observe pulsars spin. |
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Term
| What causes the radio pulses of a pulsar? |
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Definition
| As the star spins, beams of radio radiation sweep through space. If one of the beams crosses the earth, we observe a pulse. |
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Term
| From a theoretical standpoint, what is a pulsar? |
|
Definition
| a rapidly rotating neutron star |
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