Astronomy Student Notes Our Sun and Other Stars Name Date Period Vocabulary: Please number and define each term below in a complete sentence on a separate sheet of paper(terms that have an *, please illustrate) Photosphere* Chromosphere* Red Dwarfs Blue Supergiants Corona * Convection Zone* Solar Core* Radiation Zone* Standard Solar Model Helioseismology* Granulated Supergranulation Transition Zone Solar Wind* Sunspots* Sunspot Cycle Solar Minimum* Solar Maximum* Solar Cycle Active Regions Prominences* Flares Parsec* Giants Supergiants Red Giants* Dwarfs White Dwarfs* Color Index* H-R Diagram* Main Sequence* The Sun in Bulk A.How does the text describe the structure of the Sun? -the Sun is sized, temperature, mass, radius and composition, making it easy for life to flourish on B.What happens in each layer of the Sun? - - where nuclear fusion takes place which powers the Sun, found at the center - - located outside the core, it transfers energy from the core by radiation - - material from the radiation zone is transferred by convection instead of radiation - - considered the surface of the Sun, always a gas state, just like every other layer - - the Sun s lower atmosphere - - the very thin outer atmosphere of the Sun, visible during a total eclipse - - energy flows out from the Sun and permeates the entire solar system C.How big is the Sun compared to Earth in diameter and radius? -The Sun is about 100 times the diameter of the Earth and has a volume times of Earth -The mass of the Sun is about times greater due to the effect on all object in the solar system D.How long does one rotation take place on the Sun, (at the Equator, at the Poles)? - The Sun rotates once every 27 days at the equator and 31 days at the poles E.What is the average solar surface temperature in Kelvin (Fahrenheit)? - The solar surface averages 5800-6000 in temperature F.What is luminosity, how much energy does the Sun give off each second? -Every second the Sun gives off the equivalent of energy to 100 billion megaton The Solar Interior A.What is, how is information in this field of science gathered? -Study of the interior of the Sun (has nothing to do with seismic waves and earthquakes) - Using computer models, physics and estimates, scientists have determined the and temperature of the internal layers of the Sun B.What is convection, how does it work on the Sun? -In the convection layer is transported to the upper levels through convection (same way that a pot of water begin to rise in temperature) 1
-The gas particles in the core and radiation zone with each other constantly but by the time it get to 200,000 km out it is turned into energy and through convection transferred towards the surface C.What is Granulation? -Looking at the surface of the Sun it looks highly -Each granule is about 1000 km across, has a lifetime of and depending on its color light or dark will fluctuate in temperature by 500 K -Granules shows rising up to the Photosphere The Solar Atmosphere 1.What is the composition of the Sun s atmosphere? - by studying the absorption lines, from the photosphere can be found, hydrogen and helium are the most abundant elements, just like on the Jovian planets 2.When is the Chromosphere and Corona visible? -Chromosphere- not visible unless a is occurring, sight of solar storms -which layer is hotter, why? Corona - spectral lines are dramatically different due to, temperatures dramatically increases above the chromosphere in the transition zone for reasons that are still not entirely known 3.What is the Solar Wind? - radiation moves away from the Sun at the speed, and particles such as protons and electrons escape at -The Sun in X Rays- gas emitted at cannot be seen by regular telescope but by x ray telescopes, can detect coronal holes where the solar wind escapes F.The Active Sun 1.What is the difference between the active Sun and quiet Sun? - Continuous emission from the Sun s photosphere gives off the luminosity, this is ordinary and called the quiet Sun, while unpredictable radiation that affects us on Earth is called the 2.What are sunspots, what causes them? -Dark spots on the Sun that are of the photosphere - - the cause of sunspots, the magnetic fields tend to be 1000 times greater than the surrounding hotter photosphere, usually pairing up with another sunspot with the same polarity 3.What is the Solar Cycle? - a sunspot cycle lasts approximately (# of sunspots reaches maximum) due to the 22 year cycle of the Sun s magnetic field which is stretched due to the differential rotation and convection at different latitudes 4.What happens at active regions- during solar maximum? -During solar maximum (11 year cycle), large of energetic particles erupt violently from the photosphere then arch back towards the sun due to the magnetic field, releasing more energy than all the power plants on Earth producing energy for 1 billion years) G.The Heart of the Sun 1.How much energy is generated through solar energy production on the Sun? - The amount of energy released by the Sun daily dwarfs the energy released from solar prominences and flares, each kilogram of solar material (2.5 lbs), thirty trillion joules of energy must arise, the only way to produce this much energy is by (combining of light nuclei into heavier ones) -What is nuclear fusion (in about 2 sentences)? 2
3 -Fusing of 2 nuclei= tremendous release of energy and a third atom of helium, this is called the proton-proton chain -Sun fuses of material per second, very little mass is lost in the Sun, most is just converted into another element -Why is observation of Solar Neutrinos important? - Astronomers cannot witness nuclear fusion in the core of the Sun, but indirectly detect it through (byproduct of nuclear fusion) -Solar neutrino detectors are built deep within the Earth where only neutrino can penetrate and react with chlorine to make argon, they haven t found the amount of neutrinos expected, why? The Distances to other Stars -How is stellar parallax used? -A stars apparent shift relative to some more distant background as the observer s point of view change -Using the, astronomers can use two ends of a baseline, or two opposites sides of the Earth, for more distant stars using parallax requires using the Earth s different positions at different points of the year (up to 2 A.U. for a baseline) -What distance do we used to find distance, what is the length? -Using parallax to find distance is measured in parsecs (pc), 1 parsec= -How many star are in our neighborhood (within 4 pc), which is the closest? -approximately lie within 4 pc (13.2 light years) of Earth, the closest star is called Proxima Centauri at 4.3 light years away or 270,000 A.U. -How many stars are within 100 light years of Earth? -1000 stars are within of Earth but most are well beyond this distance Stellar Temperatures How do we measure a Star s temperature? -By measuring app. Brightness and the (frequency of radiation emitted by a hot object) a stars temp. can be determined What is the color index? -By color we can approximate a star s surface temp. = 30,000 Kelvin = 3,000 K Stellar Sizes How do we determine the radius of other stars? -Using Geometry, astronomers can directly measure the sizes of a few nearby stars but for most stars, astronomers know how to determine a star s and from this the radius of the star can be determined ex. The Star Mira has a surface temperature of 3,000 K and a luminosity of 1.6x 10 29 Watts= 80 times the radius of Sun -What makes a star a Giant? -stars with radii of that of our Sun -What makes a star a Supergiant? - even larger stars with radii of up to times of our Sun -What makes a star a Red Giant? - a giant star with a temperature of -What makes a star a Dwarf - stars that are smaller than the Sun, some similar to the size of, most dwarfs are very hot at 24,000 K, is a white Dwarf Luminosity and Brightness -What is the difference between apparent brightness and absolute brightness?
-Apparent brightness is the amount of luminosity from a star as seen from Earth, not a true measure of luminosity, the formula is: -How do we determine the apparent brightness? - Absolute brightness = Temperature and Color -What are two ways that we can determine the temperature of a star? - By looking at the of a star, a rough estimate on temperature can be determined but with at least one intensity measurement at different wavelengths the exact temperature can be determined - is the second way -What is photometry - analysis in which a star s intensity is measured through a set of standard filter The Classification of Stars -How do we classify stars? - Using a of temperature, color, spectroscopy and spectral-line radiation are all used to classify stars -What does a detailed spectra tell us? - looking at various stars spectrums, which shows different elements appearing (though they all have similar elemental abundances) due to different temperature of stars -How are stars classified? - stars are classified based on, the hottest stars are an O to M being the coolest: Further subclasses of stars are numbers, our sun is G2 star, not quite hot enough to be considered a G1 but hotter than a G3 The Hertzsprung-Russell Diagram -How are stars classified on H-R Diagrams?, -A star s luminosity ( ) and its surface temperature (spectral class or color) are used to classify it -Who invented it? -in the Ejnar Hertzsprung and Henry Russell plotted these two qualities to come of with the H-R Diagram -What is on the x-axis, y-axis? - Surface temperature is on the while is on the y-axis, the Sun is right in the middle -What is the main sequence? - The main sequence- Hertzsprung and Russell noticed that most stars fall in certain sections, cool stars tend to be faint while bright stars tend to be hot - of stars are probably main sequence stars, while the remaining 9% are white dwarfs and 1% are Extending The Cosmic Distance Scale -What method is used to find the distance to stars beyond 100 pc? - Using is a method for determining distance to stars beyond 100 pc, this measurement is based on the H-R Diagram reading and the assumption that stars far away are probably similar to the one within 100 pc, this measurement is probably only 25% accurate Stellar Mass -How do we determine the mass of other stars? 4
5 -luminosity class considers density of which determines between a bright giant and a supergiant -What are binary-star systems? -two stars that are part of the same solar system we can see them -Why are eclipsing binaries helpful in studying star features? - binary stars eclipse each other and are called eclipsing binaries, the light difference is measured and can determine -What determines the location of a star on the main sequence? -The mass of a star determines its location on the, the radius of a star rises in proportion to its mass, while luminosity rises more like the cube of its mass -How long do different stars live for? -Stellar mass/stellar Luminosity, large O and B stars that are 10-20 times more massive than the Sun and 1000 s of times more luminous usually die out within 20 million years, M stars are much less massive and very faint but will exist for, while K and over a trillion years Chapter 20 Stellar Evolution -What happens to an aging G type main sequence star? -Its core temperature slowly increases due to consumption of Hydrogen converted to -Towards the end of its 10 billion year life, our Sun will change its appearance and its days are numbered (low mass stars die gently while high mass stars die catastrophically) -When all H is gone a star gets brighter and over 100 million years grows to a red giant and moves to the cooler position on the HR Diagram -The Sun grows to 8 times the mass of the Sun- (considered a high mass star) -What happens when the core becomes all Helium? -The Helium shell flashes causes it to be unstable, causing the outer layers to pulsate eventually becoming a planetary nebula -After many Helium flashes a white dwarf appears in a few thousand years (very hot- about the size of Earth but a mass of ½ the Sun) 20.4 Evolution of Stars more Massive than the Sun -How will a more massive Star differ in its death? -High mass stars evolve much faster than low mass stars -Our Sun will spend 10 Bill. Years on the main sequence -5x solar mass (B stars)- only 100,000,000 years on Main Seq. -10 x solar mass (O stars)- only 20,000,000 years on -Stars leave main sequence for one basic reason- run out of H -A high mass star > 8 solar masses are able to fuse heavier and heavier elements Chapter 21 Stellar Explosions -What happens when a high mass star s core fuses completely into Iron? -The star implodes falling in on itself, the temperature rises to -The spectacular death rattle of a high mass star is known as a -What is a Type I supernovae? -Hydrogen poor, resulting from a carbon white dwarf (descendant of a low mass star) pulling matter from binary nearby What is a Type II supernovae? -Hydrogen rich, results of a high mass star core collapse How do we know Supernovae occur? -Supernova remnants in our galaxy-
-Originally exploded in 1054 AD, brighter than Venus and visible during the daytime -From supernovae, all elements found on the are created Chapter 22 Neutron Stars and Black Holes What is left after a star goes supernova? -The core remnant is called a, they are extremely small (size of a large city) but very massive (more massive than the Sun), a billion times denser than a white dwarf ex. Half a teaspoon of neutron star would weigh (as much as an 8,000 ft mountain) Neutron stars are solid but if you walked on one you would weigh 1 billion tons and be flatten thinner than a piece of paper How can we detect neutron stars? -Neutron stars rotate in, they are referred to as Pulsars- emitting periodic bursts of radiation like a lighthouse flashing between 3-30 times/second 22.5 Black Holes How massive does a star need to be to become a black hole? -Any star with a mass of, the central core collapses forever creating a black hole -At this point gravity is so strong not even light, radiation and information can escape - mechanics cannot explain the conditions created in or near a black hole What is the escape speed of a black hole? -Remember: Escape speed is proportional to the square root of a body s mass by the square root of its radius -Earth s escape velocity is, if Earth were compressed to ¼ it size, escape speed= 22 km/s -If we compress Earth to about a = 300,000 km/s escape speed (speed of light), this would mean nothing can escape the speed of gravity How does a black hole affect surrounding space? -Any object with a lot of mass curves space (the actual fabric), the more massive the object the more space surrounding it is -If an object is massive enough (> 25 solar masses) it will create an Event Horizon -Over time a black hole s mass grows when debris come into the vicinity of the event horizon What if we could send an astronaut into a black hole, what would it be like? -If an astronaut tried to travel towards a Black Hole he/she would be squeezed and stretch unmercifully, they would also be heated to extremely What if we could send an impenetrable probe to extreme environments (no such thing for a black hole) into a BH? -If we could send a probe, while we observe from a safe distance, we would see the green light from the robot become to gravitational redshift -The robots clock signal would tick than an equivalent clock on board our space ship, till it stops altogether, this is called -To the in-falling probe time would remain the same -If the probe made it past the Event Horizon, what would happen? No one knows! Humans need to develop a better overall theory of (quantum gravity- the merger of general relativity with quantum mechanics) - attempted to make unified theory, not successful 6
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