Term
| What is the Orion Nebula? |
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Definition
| a large interstellar gas and dust cloud containing many young stars |
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Term
| What planet has a similar density to the Sun? |
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Definition
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Term
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Definition
| A plot of luminosity and surface temperature of stars. |
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Term
| Spectral diagrams emitted from the sun that are split into two or more components show that... |
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Definition
| The sun has a strong magnetic field |
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Term
| What is the relationship between stellar mass and luminosity? |
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Definition
| The greater the mass, the greater the luminosity |
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Term
| What is Hydrostatic Equilibrium? |
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Definition
| The balance of gravity inward and gas pressure outward |
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Term
| When is electron degeneracy pressure important in the life of a star? |
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Definition
| It occurs at the end of hydrogen burning in the star's core, just before the start of helium burning in a star's core. |
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Term
| What is the spectral type of a star most directly related to? |
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Definition
| The surface temperature of the star |
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Term
| What defines the end of the protostar period of star development? |
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Definition
| Nuclear reactions beginning in the protostar's core |
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Term
| Where does a star move on the HR diagram when a star stops burning hydrogen in its core? |
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Definition
| The upper right, where red giants are located |
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Term
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Definition
| Differential rotation and its effect on weak magnetic fields |
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Term
| What supports a white dwarf star? |
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Definition
| Degenerate electron pressure in the compact interior |
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Term
| At what distance are objects assumed to be when measuring absolute magnitude? |
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Definition
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Term
| What are the characteristics of a K2 III star like Arcturus? |
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Definition
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Term
| What occurs in a semidetached binary system? |
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Definition
| One star fills its Roche lobe while the other does not |
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Term
| At what temperature do thermonuclear reactions in a star's core begin to convert helium into carbon? |
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Definition
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Term
| What is the characteristic color of an emission nebula? |
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Definition
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Term
| What provides power for the sun? |
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Definition
| Fusion of hydrogen into helium |
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Term
| In what kind of binary star system does the transfer of mass from the surface of one star to another star occur? |
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Definition
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|
Term
| In which wavelength is the sun's coronal hole most prominently visible? |
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Definition
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|
Term
| What characteristic do all main sequence stars share? |
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Definition
| They generate energy by hydrogen fusion in their cores |
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Term
| What effect does interstellar dust have on starlight? |
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Definition
| It dims and reddens distant stars by preferentially scattering their blue lights |
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Term
| What causes a helium flash and in what type of star does it occur? |
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Definition
| Electron degeneracy or quantum crowding in the core of a low mass red giant star |
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Term
| What is the temperature of the corona of the sun? |
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Definition
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Term
|
Definition
| A low mass star at the end of its life |
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Term
| What is the last nuclear burning stage in the life of a low mass star like the sun? |
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Definition
| Fusion of helium nuclei to form carbon and oxygen |
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Term
| What are the layers of the sun from the center outward? |
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Definition
| Radiative zone, convective zone, photosphere, chromosphere, corona |
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Term
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Definition
| Stars that are slowly contracting and heating up |
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Term
| How long will the sun be a main sequence star? |
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Definition
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Term
| What is apparent magnitude? |
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Definition
| The measure of the brightness of a star as seen from earth |
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Term
| What is proper motion of a star? |
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Definition
| Its apparent motion across our sky against the background stars |
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Term
| What has the study of stars in clusters helped astronomers to understand? |
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Definition
| Stellar evolution -- the development of stars over time |
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Term
| How precisely can stellar parallax be measure by telescopes on Earth? |
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Definition
| 0.01 arc seconds, equivalent to about 100 parsecs in space |
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|
Term
| What is the Chandrasekhar limit? |
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Definition
| The point at which a white dwarf star can no longer support its own weight -- 1.4 solar masses |
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|
Term
| How many more years will the sun be able to generate energy using nuclear reactions in its core? |
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Definition
| About 5 billion more years |
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Term
| How can the age of a star cluster be determined? |
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Definition
| By determining its turnoff point from the main sequence of the HR diagram |
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Term
| What is most important in determining where a protostar reaches the main sequence on the HR diagram? |
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Definition
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|
Term
| What causes granulation on the surface of the sun? |
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Definition
| Convection currents carrying heat from beneath the surface |
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|
Term
| What is the second hottest surface temperature spectral class? |
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Definition
|
|
Term
| What is the order of the spectral classes |
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Definition
|
|
Term
| What is most important in controlling the evolution of a star? |
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Definition
|
|
Term
| What are the two most abundant materials in the universe? |
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Definition
|
|
Term
| What is most important in controlling the evolution of a star? |
|
Definition
|
|
Term
| What are the two most abundant materials in the universe? |
|
Definition
|
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Term
|
Definition
| An elusive subatomic particle which has little or no mass and is difficult to detect |
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Term
| What kind of stars are at the center of an H II region (emission nebula) |
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Definition
| Bright, young O and B stars |
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Term
|
Definition
| Cool, dark regions on the sun's surface |
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Term
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Definition
| an object intermediate between a planet and a star, with not enough mass to begin nuclear reactions in its core. |
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Term
| What is the temperature of the sun's photosphere? |
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Definition
|
|
Term
| How many of all the stars are main sequence? |
|
Definition
|
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Term
|
Definition
| star burning hydrogen into helium in a shell around the core. |
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Term
| What is the surface of the sun called |
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Definition
| The surface of the sun is called photosphere |
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Term
| What kind of galaxy has very little interstellar dust and gas? |
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Definition
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Term
| What is the "central engine" of an active galaxy? |
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Definition
| A supermassive black hole at the center of an accretion disk, with jets of material being ejected perpendicular to the disk. |
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Term
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Definition
| A galaxy that has a disk and a bulge with smooth light distribution but no spiral arms |
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Term
| What is the Hubble classification of a very flat elliptical galaxy? |
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Definition
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Term
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Definition
| A cluster of galaxies in which the Milky Way is located. |
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Term
| What is the temperature of the blackbody radiation we detect that originated in the Big Bang (cosmic microwave background radiation)? |
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Definition
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|
Term
| What is the energy output of a bright quasar equivalent to? |
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Definition
|
|
Term
| What is cosmological redshift? |
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Definition
| The stretching of the wavelengths of photons as they travel through expanding space. |
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Term
| What do cosmologists study? |
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Definition
| The origin, structure, and evolution of the universe. |
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Term
| What is a supercluster of galaxies? |
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Definition
| A cluster of galaxy clusters |
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Term
| What are Seyfert galaxies? |
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Definition
| Active galaxies with very bright, starlike nuclei |
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Term
| In the Hubble classification scheme for spiral galaxies, what is the tightness of the winding of the spiral arms most directly related to? |
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Definition
| The size of the central bulge of the galaxy. |
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Term
| What kind of galaxy contains mostly old, low mass, population II stars? |
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Definition
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|
Term
| What does a spiral galaxy look like when seen edge-on? |
|
Definition
| A thick, flat line with a bulge in the center |
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Term
| What is a starburst galaxy? |
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Definition
| A galaxy that has collied with another and caused a burst of star formation |
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Term
| In the 1970s it was discovered that, among spiral galaxies, the wider the 21 cm radio emission line is, the brighter the galaxy. What is the name of this relation? |
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Definition
| The Tully-Fisher Relation |
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Term
| What do elliptical galaxies not have? |
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Definition
| A disk, bulge, and spiral arms. |
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Term
| What is a quasar thought to be? |
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Definition
| The central core of an active galaxy |
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Term
| What is cosmic microwave background radiation? |
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Definition
| Radiation left over from the big bang, after the universe expanded and cooled. |
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Term
| What do quasars appear to be? |
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Definition
| Very distant, intrinsically bright objects that are moving away from earth at very high speeds. |
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Term
| In relation to the universe, what does the word "isotropic" mean? |
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Definition
| The expansion of the universe is the same in all directions. |
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Term
| What observational fact convinces astronomers that the source of the energy in a a typical quasar is physically very small? |
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Definition
| The rapid variation of the intensity of the source |
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|
Term
| What does the Hubble distance-velocity relationship state? |
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Definition
| The farther a galaxy is away from our galaxy, the faster it appears to be traveling away from it |
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Term
| What if the universe is unbounded? |
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Definition
| The universe will expand forever |
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Term
| What was the COBE satellite designed to measure? |
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Definition
| Cosmic microwave background radiation |
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Term
| Which two parameters representing observations of distant objects in the universe are related to the Hubble Law? |
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Definition
| The distance to the object and a redshift of its light |
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Term
| How are the Magellanic Clouds classified? |
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Definition
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Term
|
Definition
| A galaxy that has two lobes, one on each side of the galaxy, which emit synchrotron radiation at radio wavelengths. |
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Term
| In what type of galaxy is star formation no longer occurring? |
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Definition
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|
Term
| If space is flat, what is the future of the universe? |
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Definition
| It will barely expand forever, reaching zero expansion speed after infinite time. |
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Term
| What is the Hubble classification of a spiral galaxy with a prominent central bulge and smooth, flat spiral arms? |
|
Definition
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|
Term
| What parameter of the present universe is considered to be most critical in determining the ultimate fate of the universe? |
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Definition
| The average density of matter |
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|
Term
| In which classification of galaxies is the largest range of sizes found? |
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Definition
|
|
Term
| When is synchrotron radiation produced? |
|
Definition
| When electrons move in spirals in a magnetic field |
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Term
| In what important measurement in astronomy are variable stars (RR Lyrae and Cephied) used? |
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Definition
| The measurement of distances to galaxies |
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|
Term
| What two characteristics of distant objects does the Hubble relation link? |
|
Definition
| Distance and velocity of recession |
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|
Term
| What is the meaning of the cosmological principle |
|
Definition
| We do not occupy a special location in space, because the univese is the same everywhere on average |
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Term
| What will happen if the universe is bounded? |
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Definition
| The univese will eventually fall back in on itself; the "big crunch" |
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Term
| Where is a pulsar usually found? |
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Definition
| At the center of a supernova explosion |
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|
Term
| What separates a black hole from the rest of the universe? |
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Definition
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|
Term
| What is the maximum mass of a neutron star? |
|
Definition
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|
Term
| Where in our galaxy are young, metal-rich stars found? |
|
Definition
| In the disk and spiral arms |
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|
Term
| How far is our sun from the center of the MWG? |
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Definition
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|
Term
| How did Sir William Herschel try to measure our sun's position in our galaxy in the 1790s? |
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Definition
| By counting the density of stars in different directions along the milky way |
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|
Term
| What quantum transition occurs in a cool hydrogen atom to produce a 21-cm radiation photon? |
|
Definition
| An electron in the ground atomic state reverses the direction of its spin. |
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|
Term
| What material in the MWG prevents us from seeing and photographing the galactic center at optical wavelengths? |
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Definition
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|
Term
| What mechanism gives rise to the phenomenon of the nova? |
|
Definition
| Matter from a companion star falls onto a white dwarf in a close binary system, eventually causing a nuclear explosion |
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|
Term
| How are neutron stars believed to be created? |
|
Definition
| By type II supernovae, the explosions of high-mass stars |
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|
Term
| Where are O-type stars not found in our galaxy? |
|
Definition
|
|
Term
| What is the Chandrasekhar limit? |
|
Definition
|
|
Term
| What method did Harlow Shapley use in 1917 to estimate the sun's location in the MWG? |
|
Definition
| He measured the locations of globular clusters around the galaxy |
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Term
|
Definition
| A point of infinite density |
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|
Term
| What is the term used to describe when light traveling away from the surface of a neutron star becomes strongly redshifted? |
|
Definition
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|
Term
| When is the core collapse phase at the end of the life of a massive star triggered? |
|
Definition
| When nuclear fusion has produced a significant amount of iron in the star's core |
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|
Term
| What is the law of cosmic censorship? |
|
Definition
| There can be no naked singularities -- every black hole must be surrounded by an event horizon |
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|
Term
| What kind of wave is similar in properties to the density wave that produces the spiral arm in the MWG? |
|
Definition
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|
Term
| What is a type II supernovae? |
|
Definition
| The explosion of a single, high mass star after silicon burning has produced a core of iron nuclei |
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|
Term
| What kind of galaxy is the MWG? |
|
Definition
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|
Term
| Where do the X-Rays that come from the vicinity of a black hole actually originate? |
|
Definition
| Just outside the event horizon, on the accretion disk |
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|
Term
| How did we deduce that there is possibly a very large amount of dark matter in the halo of our galaxy? |
|
Definition
| The rotation curve of our galaxy, which indicates higher than expected orbital speeds in the outer regions of the galaxy |
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|
Term
| What is photodisintegration? |
|
Definition
| the splitting apart of atomic nuclei by high energy gamma rays |
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|
Term
| What is the sequence of end points in stellar evolution in order of increasing maximum mass? |
|
Definition
| White dwarf, neutron star, black hole |
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|
Term
| How does interstellar matter affect our view of the disk of our galaxy? |
|
Definition
| It blocks the view of the disk more at optical wavelengths, less in infrared, and not at all at radio wavelengths |
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|
Term
| Where did black holes get their name? |
|
Definition
| Because no light or any other electromagnetic radiation can escape from inside them |
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|
Term
| What has been proposed to explain the tremendous amount of activity detected at the center of our galaxy? |
|
Definition
| A supermassive black hole |
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|
Term
| According to the theory of general relativity, why does the earth orbit the sun? |
|
Definition
| Earth orbits the sun because space around the Sun is curved and the Earth follows this curved space |
|
|
Term
| Who discovered the first pulsar? |
|
Definition
| An English graduate student, Jocelyn Bell, in 1967 |
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|
Term
| Where is the center of the MWG located? |
|
Definition
|
|
Term
| What is a type 1-a supernova? |
|
Definition
| the explosion of a white dwarf in a binary star system after mass has been transferred onto it from its companion |
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|
Term
| How are clocks affected by the presence of a presence of a gravitational field? |
|
Definition
| Clocks in a gravitational field run slower than clocks outside the field |
|
|
Term
| What is the Swarzschild Radius? |
|
Definition
| The distance from the singularity to the event horizon, from which light cannot escape |
|
|
Term
|
Definition
| An elusive subatomic particle which has little to no mass and is very difficult to detect. |
|
|
Term
| When is Synchotron radiation emitted? |
|
Definition
| When charged particles are forced to move along curved paths within a magnetic field |
|
|
Term
| According to Newton's law of gravity, why does the earth orbit the sun? |
|
Definition
| the Earth orbits the Sun because the sun exerts a gravitational force on the Earth across empty space |
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|
Term
| What outlines the spiral arms in our galaxy? |
|
Definition
| Dust, Gas, and Young O and B stars |
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|
Term
| What is the main observational difference between type I and type II supernovae? |
|
Definition
| Hydrogen lines are prominent in the spectrum of a Type II supernova but absent in a Type I |
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|
Term
| What did Ancient Chinese astronomers record the appearance of in 1054? |
|
Definition
| A supernova, bright enough to be seen in broad daylight |
|
|
Term
| What is the main observational difference between type I and type II supernovae? |
|
Definition
| Hydrogen lines are prominent in the spectrum of a Type II supernova but absent in a Type I |
|
|
Term
| What did Ancient Chinese astronomers record the appearance of in 1054? |
|
Definition
| A supernova, bright enough to be seen in broad daylight |
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