Astronomy Exam 3
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lealafortune on May 22, 2011
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68 terms
Terms | Definitions |
|---|---|
 Nova | A white dwarf undergoing an explosion on its surface that results in a rapid, temporary increase in the star's luminosity |
| How long does a nova last? | About 100 days |
| How do you get a nova? | From a white dwarf in a detached binary system |
| What temperature does a star reach before it implodes? | 10 billion K |
| Photodisintegration | process occurring at high temperatures, in which individual photons have enough energy to split a heavy nucleus |
| Differences between a nova and a supernova? | -Supernova is a million times brighter than a nova -A star may become a nova many times but a supernova only once |
| Why can stars only become a supernova once? | Matter can be transferred from a binary companion star onto a white dwarf many times, but a massive star only collapses once |
| What are the different supernovae? | Hydrogen rich (Type II) and Hydrogen poor (Type I) |
| Difference between Type 1 and Type 2 | Type I has a light curve similar to a nova but Type 2 has a light curve with a characteristic plateau |
| Type I explosion | Binary star with a white dwarf and explodes -Carbon detonation |
| Type II explosion | Iron core implodes and hydrogen is rebounded out creating a shockwave and explosion -Core collapse |
| Vela supernova remnant | An observable supernova should occur in our Galaxy once every 100 years |
| Cosmic abundances of the elements | The terrestrial elements correspond to the most abundant -Peaks are at multiples of 4 mass units |
| Proton Fusion | Four protons combine to form a nucleus of helium-4, releasing energy in the process |
| Helium Fusion | The helium-4 nuclei combine to form carbon-12 |
| Carbon Fusion | Carbon can form heavier elements by fusion with other carbon nuclei or by fusion with a helium nucleus |
| Neutron capture | The formation of heavier nuclei by the absorption of neutrons |
| S-Process | explains the synthesis of stable nuclei up to the heaviest-known nonradioactive nucleus but it cannot account for the heaviest nuclei |
| R-Process | Forms the very heaviest elements |
| Cycle of Stellar Evolution | -Matter in the interstellar cloud condenses to form a star -The star synthesizes new elements in fusion reactions -This matter is expelled into space in planetary nebulae or supernovae -Matter becomes available for a new cycle of star formation |
| Stellar Nucleosynthesis | The production of new elements by nuclear reactions in the core of evolved stars -All elements heavier than helium are formed here |
| What does a core-collapse supernova leave behind? | A remnant |
| Remnant | an ultra-compressed ball of material called a neutron star |
| Neutron Star | Extremely dense and are predicted to be very hot, strongly magnetized, and rapidly rotating |
| Pulsar | A signal from a rapidly rotating neutron star |
| Lighthouse Model | A rapidly rotating neutron star with an an intense magnetic field and radiation is emitted along N and S magnetic poles |
| Pulse Period | the rotation period of the neutron star |
| Electromagnetic Spectrum | Pulsars emit pulsed radiation in many parts of the electro-magnetic spectrum |
| Gamma-ray bursts | Merger of 2 neutron stars that collapse to a single star producing a relativistic fireball |
| X-ray burster | Bursts caused by nuclear explosions on the surface of a neutron star which is accreting material -It is similar to a nova (visible light burst when material ignites in a nuclear reaction on the surface of a white dwarf |
| Millisecond pulsar model | Found in the hears of old globular clusters -Gas from companion star spiral onto surface of a neutron star, striking it parallel to the friction of rotation, causing a speed-up |
| Binary Exchange | Neutron star replaces one of two low-mass stars in binary system |
| Theory of Relativity | The speed of light is independent of the motion of the source or the observer -The speed of light is a constant |
| Black Hole | A region of space from which nothing can escape |
| Predictions of the Theory of Special Relativity | Contraction of Lengths, Time Dilation, and Mass Increase |
| Contraction of Lengths | The length of a rapidly moving space ship (or any other object traveling close to the speed of light) contracts in the direction of travel |
| Time Dilation | Clocks on board a rapidly moving space ship will run slow |
| Mass Increase | The mass of the space ship appears to increase |
| General Relativity | Tells us that space warps or curves like the rubber sheet in the vicinity of a massive object |
| How to make a Black Hole | -As star contracts under gravity initially the speed of light exceeds escape velocity--space curvature is not enough -As the star's surface contracts inside the event horizon, light no longer exceeds escape velocity and cannot escape. Curved space sends light back to the star's surface |
| Bending of Starlight | The path of light from the star is bent because of the curvature in space caused by the Sun -Observable during a total eclipse of the Sun |
| Gravitational Redshift | A consequence of General Relativity -As the photon escapes it gives up energy to escape the black hole's gravity -The close the probe comes to the black hole, the more difficult it is to escape and the more energy must be given up |
| Gravitational Light Deflection | Light bending around the edges of a supermassive black hold makes it impossible for the hole to be observed as a black dot against the bright background of its stellar companion |
| A neutron star is about the same size as ___ | A US City |
| A neutron star's immense gravitational attraction is due primarily to its small radius and: | large mass |
| The most rapidly "blinking" pulsars are those that: | spin the fastest |
| The X-ray emission from a neutron star in a binary system comes mainly from: | Heated material in an accretion disk around the neutron star |
| Black holes result from stars having initial masses what size compared to the Sun | more than 25 times |
| The best place to search for black holes is in a region of space that: | has strong X-ray emission |
| Galaxy | A huge collection of stellar and interstellar matter isolated in space and bound together by its own gravity |
| Characteristics of a typical spiral galaxy | Galactic bulge, galactic center, galactic disk, and galactic halo |
| Variable Stars | Can be used to measure distances |
| RR Lyrae | All stars have roughly the same luminosity |
| Cepheid variables | Luminosity can be determined using the period-luminosity relationship |
| Where do variable stars occur when the stars in the red giant horizontal branch are under-going oscillations? | Instability strip |
| Period-Luminosity Relationship for Cepheids | Measures the period of the Cepheid and you have its intrinsic or absolute luminosity |
| Who found the period-luminosity relationship for Cepheids? | Henrietta Leavitt |
| How to measure the period of a Cepheid variable | Measure the apparent luminosity through your telescope, so you can easily find the distance from the inverse square law |
| Where are red stars in the Milky Way? | Distributed uniformly among the disk, halo, and globular clusters |
| Where are blue stars in the Milky Way? | Mostly in the disk |
| Disk Stars | Move in nearly circular orbits about Galactic center |
| Halo Stars | Move in randomly oriented, elongated orbits out of the Galactic plane |
| Formation of the Milky Way | -Forms by merger of smaller galaxies -Motion of stars is random -Rotation causes dust and gas to fall to Galactic plane -Stars already formed remain in the halo, but further star formation occurs in the Galactic plane |
| Spiral Arms | Regions of the densest interstellar gas where star formation is taking place |
| Spiral Density Waves | Spiral arms are waves of gas compression and star formation moving through the material of the Galactic disk |
| Self-propagating star formation | Shock waves causes by star formation and evolution trigger a new round of star formation |
| Rotation Curve | The continued rise in the rotation curve indicates that there is unseen "dark matter" beyond the visible radius of the Galaxy |
| Gravitational Lensing | A way to look for dark matter -causes a background star to temporarily brighten |
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