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Astro ch 5 test
| Question | Answer |
|---|---|
| Stars that have masses similar to the Sun's, and sizes similar to the Earth are: | white dwarfs. |
| On the H-R diagram, the Sun lies: | about the middle of the main sequence. |
| The Hertzsprung-Russell Diagram plots ________ against the spectral type or temperature. | luminosity or absolute magnitude |
| On the H-R diagram, red supergiants like Betelguese lie: | at the top right. |
| On the H-R diagram, white dwarfs like Sirius B and Procyon B lie: | bottom left. |
| What is the single most important characteristic in determining the course of a star's evolution? | mass |
| What is the typical main sequence lifetime of an M-type star? | a trillion years |
| What is the typical main sequence lifetime of a G-type star? | 10 billion years |
| What is the typical main sequence lifetime of a B-type star? | 20 million years |
| For a star of 10 solar masses, its main sequence life span will be: | only 1/1000th of the Sun. |
| When a star's inward gravity and outward pressure are balanced, the star is said to be: | in hydrostatic equilibrium. |
| In the H-R diagram, the bright blue-white stars that dominate the naked eye sky lie to the: | top left. |
| A star (no matter what its mass) spends most of its life: | as a main sequence star. |
| What spectral type of star that is still around formed longest ago? | M |
| What spectral type of star that is still around formed most recently? | O |
| At which stage in a Sun-like star's life is its core the least dense? | Main Sequence |
| Which of the following elements contained in your body is NOT formed in the cores of stars during thermonuclear fusion? | hydrogen |
| What temperature is needed to fuse helium into carbon? | 100 million K |
| The "helium flash" occurs at what stage in stellar evolution? | red giant |
| During the hydrogen shell burning phase: | the star grows more luminous. |
| A star is on the horizontal branch of the H-R diagram. Which statement is true? | It is burning both hydrogen and helium. |
| What inevitably forces a star like the Sun to evolve away from being a main sequence star? | Helium builds up in the core, while the hydrogen burning shell expands. |
| Just as a low-mass main sequence star runs out of fuel in its core, it actually becomes brighter. How is this possible? | The core contracts, raising the temperature and increasing the size of the region of hydrogenshell-burning. |
| Refer to the figure above. What is the name of the path between the points labeled 8 and 9? | red giant branch |
| Refer to the figure above. What is the name of the path between the points labeled 10 and 11? | asymptotic giant branch |
| Refer to the figure above. What is the name of the star labeled 10? | horizontal branch |
| Refer to the figure above. At what numbered point on the graph above does the helium flash occur? | 9 |
| What is a planetary nebula? | the ejected envelope, often bipolar, of a red giant surrounding a stellar core remnant |
| The order of evolutionary stages of a star like the Sun would be Main Sequence, red giant planetary nebula, and finally: | white dwarf. |
| Refer to the figure above. What is the name of the path between the points labeled 11 and 12? | planetary nebula |
| Refer to the figure above. What is the name of the path between the points labeled 13 and 14? | white dwarf |
| Which of these will the Sun probably become in the very distant future? | planetary nebula |
| As a 4-10 solar mass star leaves the main sequence on its way to becoming a red supergiant, its luminosity: | remains roughly constant. |
| In the evolution of massive stars, what is the significance of the temperature 600 million K? | It is the temperature needed for carbon fusing into heavier elements. |
| Which is used observationally to determine the age of a star cluster? | the luminosity of the main sequence turn-off point |
| A surface explosion on a white dwarf, caused by falling matter from the atmosphere of its binary companion, creates what kind of object? | nova |
| The Chandrasekhar mass limit is: | 1.4 solar masses. |
| The total energy emitted by the brightest nova explosions is about: | a million Suns. |
| An iron core cannot support a star because: | iron cannot fuse with other nuclei to produce energy. |
| When a stellar iron core collapses, large numbers of neutrinos are formed, and then: | they immediately pass through the core and escape to space. |
| Most of the energy of the supernova is carried outward via a flood of: | neutrinos. |
| In neutronization of the core, a proton and an electron make a neutron and a: | neutrino. |
| As a star's evolution approaches the Type II supernova, we find: | All of the above are correct. |
| Where was supernova 1987a located? | in our companion galaxy, the Large Magellanic Cloud |
| Why are neutrinos from a type II supernova detected before photons? | Neutrinos escape from the star quickly because they hardly interact with matter; photons are delayed by interactions with matter. |
| What evidence is there that supernovae really have occurred? | All of the above. |
| The supernova that formed M-1, the Crab Nebula, was observed in: | 1054 AD by Chinese and Middle Eastern astronomers. |
| What produces a type-I supernova? | mass transfer onto a white dwarf pushing it over 1.4 solar masses |
| Which of these does NOT depend on a close binary system to occur? | a Type II supernova |
| When observing a star that increases dramatically in brightness, if a plateau is observed in the light curve during the declining phase, the event is probably: | a type II supernova. |
| What is stellar nucleosynthesis? | the formation of heavier elements inside stars |
| The heaviest nuclei of all are formed: | by neutron capture during a type II supernova explosion. |
| What is the reason a type II supernova slows its dimming after about 2 months? | Energy is released from the decay of radioactive cobalt 56 to iron 56. |
| When helium capture occurs with a carbon 12 nucleus, what results? | oxygen 16 |
| The iron we commonly find in our surroundings came from: | decay of nickel 56 and cobalt 56 in a supernova remnant. |
| As seen in 1987, when two silicon 28 nuclei fuse, or when seven alpha particles are added to aSi-28 nucleus, the initial result in either case is: | nickel 56. |
| Neutron stars and black holes are formed by: | type II supernovae. |
| In a neutron star, the core is: | made of compressed neutrons in contact with each other. |
| Two important properties of young neutron stars are: | extremely rapid rotation and a strong magnetic field. |
| An object more massive than the Sun, but roughly the size of a city, is a: | neutron star. |
| The average density of neutron stars approaches: | about 1015 kg/m3, similar to the density of atomic nuclei. |
| Pulsars: | spin very rapidly when they're young. |
| The vast majority of pulsars are known only from their pulses in: | radio waves. |
| Which of these does NOT exist? | a 6.8 solar mass neutron star |
| Whose work with SETI led to the discovery of pulsars in 1967? | Jocelyn Bell |
| The supernova of 1054 AD produced: | a pulsar with a period of 33 milliseconds, visible optically. |
| What are X-ray bursters? | They are neutron stars on which accreted matter builds up, then explodes in a violent nuclearexplosion. |
| X-ray bursters occur in binary star systems. The two types of stars that must be present to make upsuch an object are: | a main sequence or giant star and a neutron star in a mass transfer binary. |
| The mass range for neutron stars is: | 1.4 to 3 solar masses. |
| The densely packed neutrons of a neutron star cannot balance the inward pull of gravity if the totalmass is: | greater than Schwartzschild's limit of 3 solar masses. |
| What explanation does general relativity provide for gravity? | Gravity is the result of curved spacetime. |
| If light from a distant star passes close to a massive body, the light beam will: | bend towards the star due to gravity. |
| A method for identifying a black hole is to: | look for their effects on nearby companions. |
| The largest known black holes: | lie in the cores of the most massive galaxies. |
| Which of the following is NOT an argument for Cygnus X-1's being a true black hole? | The mass of the visible B star is even greater than Cygnus X-1, at around 25 solar masses. |
| On a Hertzsprung-Russell diagram, where would we find stars that are cool and dim? | lower right |
| On a Hertzsprung-Russell diagram, where would we find stars that are cool and luminous? | upper right |
| On a Hertzsprung-Russell diagram, where would we find stars that have the largest radii? | upper right |
| On a Hertzsprung-Russell diagram, where on the main sequence would we find stars that have thegreatest mass? | upper left |
| What characteristic of a star cluster is used to determine its age? | the main sequence turnoff |
| What is a typical age for a globular cluster? | 12 billion years |
| In globular clusters, the brightest stars will be: | red supergiants. |
| The brightest stars in a young open cluster will be: | massive blue stars at the top left on the H-R diagram. |
| Which stars in globular clusters are believed to be examples of mergers? | blue stragglers |
Created by:
pinstripe