New User Special Price Expires in

Let's log you in.

Sign in with Facebook


Don't have a StudySoup account? Create one here!


Create a StudySoup account

Be part of our community, it's free to join!

Sign up with Facebook


Create your account
By creating an account you agree to StudySoup's terms and conditions and privacy policy

Already have a StudySoup account? Login here

Descriptive Astronomy 1455

by: Kaylee Black

Descriptive Astronomy 1455 PHY 1455

Marketplace > Baylor University > Astronomy > PHY 1455 > Descriptive Astronomy 1455
Kaylee Black
Baylor University

Preview These Notes for FREE

Get a free preview of these Notes, just enter your email below.

Unlock Preview
Unlock Preview

Preview these materials now for free

Why put in your email? Get access to more of this material and other relevant free materials for your school

View Preview

About this Document

Notes and Study Guides for the class
Descriptive Astronomy
Dwight Russell
Astronomy 1455, Baylor Astronomy, Dwight Russell, Descriptive Astronomy
75 ?




Popular in Descriptive Astronomy

Popular in Astronomy

This 35 page Bundle was uploaded by Kaylee Black on Sunday February 21, 2016. The Bundle belongs to PHY 1455 at Baylor University taught by Dwight Russell in Spring 2016. Since its upload, it has received 22 views. For similar materials see Descriptive Astronomy in Astronomy at Baylor University.

Similar to PHY 1455 at Baylor University


Reviews for Descriptive Astronomy 1455


Report this Material


What is Karma?


Karma is the currency of StudySoup.

You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!

Date Created: 02/21/16
Astronomy- In class T est one Review 02/03/2015 ▯ Go over Homework (not the order questions) ▯ List of term  Constellations- used to locate things in the sky 88 of them  Celestial sphere- easy way to talk about positions of things  Rotation- 24 hour motion, rising in east, setting in west, circumpolar  Celestial Equator- divides north and south  Declination- is like latitude North and South on celestial Sphere  Right ascension is like longitude East and West  Polaris- North Star- close to the North Celestial pole  Circumpolar- stars that do not rise or set  Solar Day- Noon to noon- when sun comes back to same position in the sky (longer than sidereal day)  Sidereal Day- spins around till stars are in the same position  Diurnal Motion- Daily Motion  Revolving- orbiting the sun  Ecliptic- the line the sun makes through the stars  Zodiac- the path the sun and planets around the sky is contained in the zodiac constellations  Summer Solstice- tilt axis of the earth beginning of summer-sun is highest in the sky in North  Winter Solstice- lowest  Equinoxes- equal night  Autumnal Equinoxes-  Vernal Equinox  Precession- wobble of the earths spin axis, doesn’t stay in the same place  Know Phases of Moon- not the waxing and waning, new-0 cresent:0- 89 Gibbous 91-179 and full, (know where it will be ) opposite of sun is Full Moon  Sidereal Month- moon in same place compared to star  Syndic- moon in same place as sun  Eclipses- know order they have to be in- sun is never closer to us than the moon o moon blocking sunlight- solar o moon cant block the whole surface of the moon- Annular eclipse  History of Astronomy- o Aristotle - most associated with the ancient greek world view o Aristarchus - rejected the Geocentric world view and supported the Heliocentric view o Eratosthenes - accurately determined the size of the Earth o Ptolemy – Almagest, the standard astronomy book for 1400 years. o Geocentric model of the Universe Heliocentric model o Retrograde Motion o Copernicus - Heliocentric world view o Tycho Brahe - Last astronomer without a telescope. Provided Kepler with the data needed in order to develop his three Laws o J. Kepler - Three Laws of Planetary Motion  KNOW KEPLERS 3 LAWS- don’t have to apply them o Galileo - Used a telescope and challenged the conventional wisdom of the motion of objects and the nature of the heavens (a and b below challenged the geocentric model, c and d challenged the idea that the heavenly object were perfect) Telescope observations: a) Phases of Venus b) Moons of Jupiter c) Sunspots d) Mountains on the Moon o Newton - Three Laws of Motion and universal Law of Gravity  Know newton’s laws from a statement o Wave nature of Light Frequency* wavelength = velocity of light Electromagnetic waves Long wavelength to short - Radio, infrared, visible, ultrraviolet, x-ray,gamma-ray o Blackbody  Weins Law and Stefans Law  Visible is hotter-which has shorter wavelengths? Shorter always has a HOTTER Absolute zero Kelvin temperature scale Wien's Law Stefan-Boltzmann Law- Hotter it gets the brighter it gets Continuous spectrum Emission line spectrum Adsorption line spectrum Kirchhoff's Laws Doppler effect o Objects with different temperatures and compositions emit different types of spectra. By observing an object's spectrum, then, astronomers can deduce its temperature, composition and physical conditions, among other things. o ▯ ▯ ▯ Astronomy Exam 3 Review The Sun Definition of a Star: A glowing ball of gas held together by its gravity and powered by nuclear fusion. Vital Statistics Radius: 696,000 km (100 Earth Radii) Mass: 1.99^10^30 kg Average Density: 1410 kg/m 3 Rotation Period: 24.9 days (equator), 29.8 days (poles) Surface Temperature: 5780K 26 Luminosity: 3.86 x 10 Watts Chemical Composition Element…. % of total number of atoms…. % of total mass Hydrogen…. 91.2…. 71 Helium…. 8.7…. 27.1 Oxygen…. 0.078…. 0.97 Carbon…. 0.043…. 0.40 Overall Structure of the Sun Core: 200,000 km Radiation Zone: 300,000 km Photosphere: 500 km, what we see and call the surface Chromosphere: the Sun’s lower atmosphere, about 1500 km thick Corona: thin, hot upper atmosphere, which turns into solar winds at a greater distance and flows away from the Sun Solar Wind: the distant corona which flows away from the Sun and permeates the entire solar system The Solar Interior, Standard Solar Model: We can’t observe the solar interior directly. Mathematical models are developed to understand the interior. These models must fit observations and known laws of Physics. That is they must explain the surface temperature of the Sun using physics phenomena consistent with the conditions (like temperatures and pressures) predicted by the models. Additional information used to test these models if obtain from helioseismology (the study of vibrations/solar surface patterns on the Sun as a whole) Two key questions will be asked about the interior of the Sun (and any other star for that matter) they are: 1. Where is the energy produced (i.e. where is the fusion occurring and what elements are involved in the fusion process)? i. The energy produced by nuclear reactions in the core travels outward toward the surface with relative ease in the form of radiation. Hot solar gas moves outward, while cooler gas above it sinks, creating characteristic pattern of convection cells. 2. How does this energy get to the surface of the sun (which makes the sun shine)? i. Energy is transported to the surface by physical motion of the solar gas. Energy is carried to the solar surface by convection. Energy is carried upward through a series of progressively smaller cells, stacked one upon another until, at a depth of about 1000 km below the photosphere, the individual cells are about 1000 km across. Convection does not proceed to the solar atmosphere. In and above the photosphere the density is so low that the gas is transparent and radiation once again becomes the mechanism of energy transport. For the Sun, the fusion occurs in the core where the temperature is about 15 million K and the density is about 3 160,000 kg/m . Sunspots: Sunspots are dark regions in the photosphere. They are typically about 10,000 km across (about the size of the Earth). They appear dark because they are cooler than the surrounding gases. They are regions where the suns magnetic field is concentrated in leaving and entering the photosphere. Just like a magnet has a North and South Pole, Sunspots come in pairs. Sunspot Cycle: An 11-year cycle in which the number of sunspots reaches a maximum and minimum. It is half the duration of the solar cycle. Solar Cycle: A 22-year cycle in which the Sun’s magnetic poles reverse and return to their original configuration. Fusion as an energy source: This process fuels the Sun. Using E=mc , 600 million metric tons/second in converted into energy. Measuring the Stars Luminosity: The amount of radiation leaving a star per unit time Luminosity is an intrinsic property of a star. It does not depend in any way on the location or motion of the observer. It is sometimes referred to as the star’s absolute brightness. (Apparent) Brightness: the amount of energy striking per unit area per unit time of some light sensitive surface. Brightness is what we can measure directly. Explain how stellar luminosity is determined: First, the astronomer must determine the star’s apparent brightness by measuring the amount of energy detected through a telescope in a given amount of time. Second, the star’s distance must be measured—by parallax for nearby stars and by other means for more distant stars. The luminosity can then be found suing the inverse-square law. For stars, brightness is related to luminosity by an inverse square law. Brightness = Luminosity/4*π*Distance ) 2 We can measure brightness directly. Therefore, using this equation to determine the luminosity we must know the distance. Conversely, if we have an independent way of determining the luminosity then we can use this equation to determine the distance to the star. Know the magnitude scale astronomers use to discuss brightness (apparent magnitude) and luminosity (absolute magnitude). Magnitude Scale: A system of ranking stars by their apparent brightness. The range 1 (brightest) to 6 (faintest) is used to categorize a star’s magnitude. Therefore, the larger the magnitude, the fainter a star would be. Apparent Magnitude: The apparent brightness of a star, expressed using the magnitude scale. Absolute Magnitude: The apparent magnitude a star would have if it were placed at a standard distance of 10 parsecs from Earth. Parsec: 3.1 x 10 16m, “parallax in arc seconds”, equal to 3.3 light-years Explain how stellar distances are determined. Parallax: The apparent motion of a relatively close object with respect to a more distant background as the location of the observer changes. Spectroscopic Parallax 1. We measure the star’s apparent brightness and spectral type without knowing how far away it is. 2. We use the spectral type to estimate the star’s luminosity, assuming that it lies on the main sequence. 3. Finally, we apply the inverse-square law to determine the distance to the star. Variable Star: A star whose luminosity changes with time. Standard Candle: Any object with an easily recognizable appearance and known luminosity, which can be used in estimating distances. Supernovae, which all have the same peak luminosity, (depending on type) are good examples of standard candles, and are used to determine distances to other galaxies. How is the mass of a star determined? If the distance to a visual binary is known, then the orbits of each component can be individually tracked and the masses of the components can be determined. For spectroscopic binaries, Doppler-shift measurements give us information only on the radial velocities of the component stars, and this limits the information we can obtain. For a double line system, only lower limits on the individual masses can be obtained. For single-line systems, even less information is available, only a rather complicated relation between the component masses can be derived. If a spectroscopic binary happens to also be an eclipsing system, then the uncertainty in the orbital inclination can be removed. Thus, both masses can be determined for a double-line binary. For a single-line system, the mass function is simplified to a point where the mass of the unseen component is known if the mass of the brighter component can be obtained by other means. Know how physical laws are used to estimate stellar sizes. The Stefan-Boltzmann law, the rate at which a star emits energy into space is proportional to the fourth power of the star’s surface temperature (luminosity α 2 4 radius X temperature ), is used as the radius- luminosity-temperature relationship is realized, as the knowledge of a star’s luminosity and temperature can yield an estimate of its radius—an indirect determination of stellar size. Know how the radial velocity is determined. Radial Velocity is determined using the known quantities of the ‘speed of light’ and atomic spectra by measuring spectral lines. The theory applied here is the Doppler Effect. Stars and Stellar Life Cycles, HR Diagrams Hertzsprung – Russell Diagrams: A plot of luminosity against temperature (or spectral class) for a group of stars. Identify Regions of the Hertzsprung Russell Diagram Main Sequence: The band of stars spanning the diagram. Yellow Giant Phase aka Horizontal Branch: Red Giant Region: The upper right hand corn of the diagram. White Dwarf Region: Faint bluish-white star seen in the bottom left hand corner of the diagram. For Main Sequence stars, be able to identify the position of a star on the H-R Diagram with its mass. Also, identify Red Dwarfs and Brown Dwarfs. The hotter the star is the bigger the mass it has. Therefore, the further left a main sequence star is on the HR diagram, the more mass it has. The Red Dwarfs are located at the bottom right of the diagram, meaning that it is small, cool, and faint. The Brown Dwarfs are small in size and low in temperature as well, but are scattered and difficult to detect. Parsec: Its magnitude is 3.3 light-years, Life Cycles of the Stars: 1) Interstellar Cloud 2) Cloud Fragment 3) Cloud Fragment/Protostar 4) Protostar 5) Protostar 6) Star 7) Main-Sequence Star 8) and 9) Subgiant to Red Giant 10) Helium Fusion 11) A Red Giant Again Study in detail the Evolution of a Sun-like Star. Be sure to be able to identify a star’s location on the H-R diagram with the processes occurring in the interior of the star (Hydrogen fusion, Helium fusion, etc.) The location of the Sun-like Star starts towards the top right, decreases sharply, continues decreasing sharply, and then the newborn star arrives on the main sequence. After the main sequence, the star shoots back up to the red giant branch, has a helium flash which lands the star on the horizontal branch, then back up to the asymptotic giant branch. Know how the ‘life’ of a high mass star differs from a Sun-like star. High mass stars develop more quickly, larger, and are unpredictable. Sun-like stars develop slower and are usually smaller. Other Important Terms Deaths of Stars: The star ventures into the twelfth stage of its life into the planetary nebula, and then to the thirteenth stage called a white dwarf. Then, the white dwarf eventually becomes a black dwarf—a cold, dense, burned-out cinder in space—where its temperature will drop to almost absolute zero. Planetary Nebula: The spectral display caused by a star that is so hot its ultraviolet radiation ionizes the inner parts of the surrounding cloud. Nova: A star that suddenly increases brightness, often by a factor of as much as 10,000, then slowly fades back to its original luminosity. A nova is the result of an explosion on the surface of a white-dwarf star, caused by matter falling onto its surface from the atmosphere of a binary companion. Supernova I: Explosive death of a star caused by the sudden onset of nuclear burning. Supernova II: Explosive death of a star caused by an enormously energetic shock wave. White Dwarf: A dwarf star with sufficiently high surface temperature that it glows white. Neutron Star: A dense ball of neutrons that remains at the core of a star after a supernova explosion has destroyed the rest of the star. Typical neutron stars are about 20 km across and contain more mass than the Sun. Black Hole: A region of space where the pull of gravity is so great nothing—not even light—can escape. This is a possible outcome of the evolution of a very massive star. Chandrasekhar Limit (Mass): the maximum mass of a white dwarf, which is 1.4 solar masses. Below lists the remnants for stars that, prior to their final explosion, have masses in the ranges given: > 10 Solar Masses become White Dwarfs < 10 Solar Masses become Neutron Stars or Black Holes Brightness and Distance-> Luminosity Parallax -> distance Luminosity and Brightness -> distance Standard Candle Technique Spectroscopic Parallax-> Temperature and that it is main sequence star Variable Stars (Cepheid Variable) Absolute magnitude scale Apparent magnitude scale 3 magnitude and 8 magnitude star - the lower the star the brighter Temp- spectrum-Wien’s Measure radius of star- Radius- Luminosity and Temperature- Stefan Boltzmann law Mass of star- Mass=Binary star system- keplers 3 rd Radial Velocity- Redshift Blueshift- Doppler High Mass – to go to type 2 supernovae Main sequence star with lifetime shorter than sun- Massive (upper left) Lower Right- long lifetime Test Four Study Guide Galaxies  There are 200-400 billion stars in the Milky Way.  The Milky Way is 30 kpc (100,000 light years) in diameter.  Nearest galaxy to ours: Andromeda, it is a part of our local group  Interstellar Medium o The stuff in between the Milky Way and galaxies  The Sun, resting on the Galactic Plane, is located 8 kpc/33,000 light years and 2/3 of the way away from the Galactic Center of the Milky Way.  It takes 230 million years for the Sun to go around the Milky Way once.  Galactic Bulge o Somewhat flattened—elongated in the plane of the disk (football- shaped) o Contains both young and old stars; more old stars at greater distances from the center; Population II stars o Contains gas and dust, especially in the inner regions o Stars have largely random orbits, but with some net rotation about the Galactic center o Ring of gas and dust near center; central Galactic nucleus o Yellow-white  Galactic Disk o Highly flattened o Contains both young and old stars; Population I and II stars o Contains gas and dust o Site of ongoing star formation o Gas and stars move in circular orbits in the Galactic plane o Spiral arms o Overall white coloration, with blue spiral arms  Galactic Halo o Roughly spherical—mildly flattened o Contains old stars only; Population II stars o Contains no gas and dust o No star formation during the last 10 billion years o Stars have random orbits in three dimensions o Little discernible substructure; global clusters, tidal streams o Reddish in color  Shapely methods of determining the size and position of the center of the Milky Way. o  Spiral Arms o Population I stars associated with spiral arms (in Galactic Disk) o Cannot rotate along with the galaxy; they would just fall into the middle  Density wave theory for spiral arm formation o Like a traffic jam, gas, dust, and materials tend to have things move in and out but dense region remains, which is the spiral arms  Self-propagating star formation for spiral arm formation o Needs a gas cloud to somehow start to collapse on itself; Supernova’s explosion causes the next supernova to form  Definitions and properties for Population I and II o Population I  Large amounts of elements heavier than helium  Located in the Galactic disk of the galaxy  0-10 billion years young, but short lived (blue stars)  Orderly roughly circular orbits  Dust and gas associated with these o Population II  Poor amounts of metal  Older stars  Cooler temperatures  In the Milky Way  Found in nuclear bulge and halo  Three major types of Galaxies in the Hubble Classification scheme: o Elliptical  Literally shaped as ellipse  Population II stars  Not orderly orbit  Very little gas and dust o Spiral/Barred Spiral  More orderly motion  Circular orbits  Best mix of Population I and II stars  Tend to have flat disks o Irregular  Galaxies that don’t fit into any regular category  Primarily Population I stars  Probably a collision of galaxies due to gravity  Galaxy Clusters: a group of galaxies held together by their mutual gravitational attraction o Rich clusters: made up of thousands of galaxies in a tightly knit group o Poor clusters: made up of a low number of galaxies in a loose collection o Local group: a poor cluster, which we belong to in the Milky Way; contains the Andromeda galaxy o Virgo cluster: nearest rich cluster  Outline of the Big Bang Theory o Planck Epoch: A mystery partly because we lack a quantum theory of gravity o The Grand Unification Epoch: Forces except gravity are unified o The Inflationary Epoch: Universe expands rapidly smaller than a proton to bigger than a melon (supported experimentally) o Electroweak Epoch: Weak and electromagnetic forces act as one o The Quark, Hadron, and Lepton Epoch: What we think of a “normal” elementary particle form and survive o Photons, Nucleosynthesis and the Cosmic Background Radiation: Atoms form (Hydrogen and Helium) and Cosmic Background radiation ‘decouples’ from matter o Dark Ages: Atoms exist but stars don’t o “Modern” Era = Stars form: Quantum fluctuations at the time of inflation determines the distribution of matter in the universe. Dense areas are where stars will form. Gravity is the major large- scale force  Defining feature of each epoch o The temperature of the Universe; as the Universe expands it cools REVIEW Review Homework Blackboard notes Chapter 14 Book Chapter 15 book Table 14.1- features summary of disk, halo, bulge Population 1 stars- group of stars that contain young massive blue stars- gas and dust in the blue stars Population 2- yellow and red- older stars very little gas and dust- middle of galaxy Spiral Arms- Density Wave theory 391- explains spiral arms like traffic jams regions where gas and dust is denser Self Propagating Star Formation 393- need supernova explosions in last generation of starts to form next generations of star formations- moves thru gas and dust of the disk and get spiral arms Three Regions Bulb halo and disk- Milky Way The sun is in the Disk Not in center of the milky way- 2/3 of the way out 100,000 light-years across- milky way Explosion on other side of galaxy it would be 100,000 yrs. 26 light-years out 200 billion stars in the milky way (hundreds of billions) Typical resident in the galactic halo- GLOBULAR CLUSTERS Determine size and position in milky way- study Cepheid variables and globular clusters in the globular halo CHAPTER 15 Galaxys 412 Elliptical Galaxy- emorphous (3d collection of stars, random orbit) Colors- no gas and dust- Population 2 stars Chapter 15 412 table for type of stars Barred spirals- what kid of galaxy is the milky way? Largest Percentage of population 1- irregular Galaxy clusters is named the local group and classified as a poor cluster- only 30 or less galaxies loosely connected gravitationally Nearest rich cluster- virgo tend to have enourmous elliptical galaxies Causes of Different Galaxy types Collisions- earliest galaxies are small- collided and built up in spiral galaxies and when they collide then they make up irregular galaxies- gas and dust from two spirals compresses the gas and get active star formation --- population 2 stars make up old yellow stars- irregular elliptical galaxies Size of, and # of stars in, the milky way. The sun's position in the Milky Way (in the disk, 2/3 of the way out from the  center). It takes 230 million years for the Sun to go around the Milky Way once.   Overall shape and regions (Bulge, Disk, Halo) of the Milky Way   Distinctive features of the regions, for example:   Halo – contains Globular clusters, is spherical in shape, contains pop. II stars  and very little interstellar gas and dust   Galactic disk – flattened shape, spiral arms, both pop I and pop II stars,  interstellar gas, dust, and pop I stars associated with spiral arms.   Bulge ­ Center of the galaxy, football shape, pop II stars, little gas and dust,  supermassive black hole at the center.   Shapely methods of determining the size and position of the center of the Milky  Way.   Density wave theory for spiral arm formation. Self propagating star formation for spiral arm formation. Definitions and properties of Pop. I, Pop. II,   Three major types of Galaxies in the Hubble Classification scheme: Elliptical,  Spiral/Barred Spiral, Irregular. Be able to identify Galaxy types by properties.   Review of causes of the different galaxy types   Clusters – Rich clusters, poor clusters, local group, Virgo cluster. Know the 'rungs' in the distance ladder. Big Bang Video Links Outline of the Big Bang Theory 2. The Grand Unification Epoch – Forces except gravity are unifiedy of gravity. 3. The inflationary Epoch – Universe expands rapidly smaller than a proton to bigger than a melon – Supported experimentally 4. Electroweak epoch – Weak and electromagnetic forces act as one. 5. The Quark, Hadron and Lepton Epoch – What we think of a “normal” elementary particle form and survive. 6. Photons, Nucleosynthesis and the Cosmic Background Radiation – Atoms form (Hydrogen and Helium) and Cosmic Background radiation ‘ decouples ‘ from matter 7. Dark Ages- Atoms exists but stars don’t. of matter in the universe. Denser areas are where stars will form. Gravity is the major large-scale force Astronomy Chapter 2 02/03/2015 Continuous Spectrum-  Spectroscope: splits light into component colors  Emission Lines: single frequencies emitted by particular atoms o The lines represent the type of Gas o Can be used to identify elements  Absorption Spectrum: if a continuous spectrum passes through a cool gas, atoms of the gas will absorb the same frequencies they emit o Long wavelengths are red, Short wavelengths are blue  The spectrums need to be recognized by a short description  ▯ Kirchhoff’s laws  Luminous solid, liquid or dense gas produces continuous spectrum  Low density hot gas produces emission spectrum  Continuous spectrum incident on cool, thin gas produces absorption spectrum ▯ Doppler Effect  If one is moving toward a source of radiation, the wavelengths seem shorter; if moving away, they seem longer  Relationship between frequency and speed: o Apparent wavelength = true frequency = 1+recession velocity o true wavelength apparent frequency wave speed depends only on relative motion of source and observer o (hearing a racecar go by) o Longer wavelengths- Pitch goes down (red shifted-away from you) o Shorter wavelengths- pitch HIGHER (Blue shifted towards you) o Wavelengths- measure of how fast its going o The Doppler effect shifts an objects entire spectrum either toward the red or toward the blue. o Radial Velocity- at the center of the circle- only get information from here in the Doppler effect o ▯ ▯ Astronomy Notes Chapter 0  Constellations ­ 88 officially, used by astronomers to show where in the sky you are  talking about­ a human grouping of stars in a recognizable pattern  Celestial Sphere­  imaginary sphere around surrounding earth to which all objects in  the sky were once considered to be attached  Rotation ­ spinning motion of body about an axis  North Celestial Pole ­ point on the celestial sphere directly above earths NORTH  POLE South Celestial Pole­ point on the celestial sphere directly above earths SOUTH  POLE  Celestial Equator­  the projection of Earth’s equator onto the celestial sphere  Celestial coordinates­  pair of coordinates, right ascension and declination, similar to  longitude and latitude on earth, used to pinpoint locations of objects on the celestial  sphere   Declination­  celestial coordinate used to measure the latitude above or below the  celestial equator on the celestial sphere  Right Ascension­  celestial coordinate used to measure longitude on the celestial  sphere. The zero point is the position of the sun at the vertical equinox  Polaris­  star near the North celestial pole Circumpolar­ stars that can be seen all the time, never rises or sets  Solar Day­  period of time between the instant when the sun is DIRECTLY overhead to the next time it is directly overhead noon to noon  Diurnal motion­  daily motion of the stars, caused by spin(rotation) of the earth  Sidereal day­ the time between successive risings of a given star  Revolving­  going around an object(sun)  Ecliptic­  the apparent path of the sun, relative to the stars on the celestial sphere, over  the course of a year  Zodiac­ the 12 constellations on the celestial sphere through which the sun appears to  pass during the course of the year  Summer solstice­  point on the ecliptic where the sun is at its northernmost point  above the celestial equator, occurring on or near June 21 Winter solstice­ point on the ecliptic where the sun is at its southernmost point below  the celestial equator, occurring on or near December 21 Seasons­ changes in average temperature and length of the day that results from the tilt  of the Earths axis with respect to the place of its orbit  Equinoxes­ tilt of the sun, nights and days are even  Autumnal Equinox­  date on which the sun crosses the celestial equator moving  southward, occurring on or near September 22 Vernal Equinox­  Date on which the sun crosses the celestial equator moving  northward occulting on or near March 21  Precession­  the slow change in the direction of the rotation axis of a spinning object,  caused by some external gravitational influence  Phases (of the Moon)­  appearance of the sunlit face of the moon at a different points  along orbit, as seen from the earth  Sidereal Month­  time required for the moon to complete one trip around the celestial  sphere  Synodic Month­  time required for the moon to complete a full cycle of phases  Eclipses­  event during which one body passes in front of another, so the light from the  occulted body is blocked  ­Lunar­  ­Partial ­Total ­Solar ­Annular Astronomy T est Three: STARS Chapters 9, 10, 11, 12 A Star: a flowing ball of gas held together by its gravity and powered by nuclear fusion  Glowing = energy out o Luminosity = how much energy it is emitting per second  Nuclear fission = a big, unstable nucleus breaking apart and releasing energy. Natural radioactivity that heats the earth, and that’s how atomic bombs work.  Nuclear fusion = small nuclei rammed together that stick together and release energy  The sun is fusion reactor, but it’s so far away that we only get the benefits from it ▯ ▯ Vital statistics of the Sun: ▯ ▯ Radius: 696,000km (100 Earth radii) ▯ Avg Density: 1410 kg/m^3 ▯ Rotation Period: 24.9 days (equator); 29.8 days (poles) ▯ Surface Temp: 5780 K Luminosity: 3.86 X 10^26 Watts  No simple way to express in earthly terms just how much energy this is ▯ Chemical Composition: Virtually all Hydrogen (91.2%) and Helium (8.7%). Traces of oxygen and carbon ▯ ▯ If the sun was a planet, it would be a GAS GIANT planet.  What is the difference between a gas giant planet and the sun: it generates energy by fusion.  Why isn’t Jupiter a star? It isn’t big enough, a star must be roughly 80 times the size of Jupiter to be a star. The temperature has to be high enough in the core for the fusion to happen.  CORE TEMPERATURE IS OUR INDICATOR AS TO WHAT A STAR IS ▯ ▯ Fusion occurs in the CORE, that’s where the energy that fuels the star is produced. ▯ Outside the core is the radiation zone. ▯ Outside the radiation zone is the convection zone. ▯ Outside the convection zone is the photosphere (outside of the star?) ▯ ▯ At the center of the sun, the temperature is OVER 15,000,000 Degrees. ▯ ▯ Fusion/Why we need high temperatures: ▯ -What is the nucleus of a hydrogen atom?  A proton ▯ -Two protons together needed for fusion (must stick), but photons want to repel from each other. To get them to stick, you have to throw them really hard together. In terms of temperature, this means that you must have a high temperature for this to happen. 10,000,000 Degrees or HIGHER. ▯ -Why such high temperatures? To give the protons enough energy so that they can overcome their natural electric composure and to get them to stick. ▯ -They get this hot through GRAVITY. ▯ -What happens to the speed as it collapses? They speed up, it becomes temperature. ▯ -How much mass is enough mass? About 80 times the mass of Jupiter. ▯ THIS IS JUST TO GET THE STAR STARTED. ▯ ▯ Structure of the sun: ▯ Core: where fusion occurs. ▯ Radiation Zone: ▯ Convection: energy travels by convection ▯ Photosphere: light escapes into space here ▯ ▯ Know the order of chromosphere, corona, solar wind. ▯ ▯ Hydrogen Fusion: energy source for stars (like our Sun). ▯ ▯ Where are stars born? – Nebulas Sunspots are associated with cooler temperatures and intense magnetic fields. Sunspots also usually come in pairs. Two cycles associated with sunspots  Sunspot Cycle: o 11 year solar cycle, sunspots go away and come back.  Solar Cycle: o About the magnetic field. Starts out a strong magnetic field with lots of sunspots, then weak with none, then strong with many. The entire cycle takes 22 years. Two sunspot cycles make up one solar cycle. ▯ ▯ Sunspots went away during the 1600s and 1700s, called the “Maunder Minimum”  The average temperature of the Earth dropped during these years  We don’t know if there is a connection between the two for sure, but it is a possible connection. ▯ ▯ MEASURING THE STARS ▯ (distance, luminosity and brightness; temperature, mass, radio velocity; radius of the star) ▯ ▯ ▯ One direct method we have of measuring a star, called PARALAX.  Finger out, eyes closed exercise. ▯ Very powerful because you don’t need to know anything about the star, you just need to be able to view it 6 months apart. The drawback is that for the nearest star to us, this angle is less than 1 arcsecond. This means you must have extremely accurate measurements. We can only do this within a few thousand light-years because of this. Luckily, there are tons of stars in this small neighborhood. ▯ ▯ Parsec: 3.3 light-years, give or take ▯ ▯ Brightness = luminosity/(4*Pi*Distance^2)  Brightness: What you see is what you get, brightness is what you see when you look at the stars. How much of the light from the star is getting to us. If you can see it, you can measure it.  Luminosity: How much energy per second the object is putting out, whether you can see it or not. (100 W light bulb; the 100 W is a measurement of it luminosity)  Distance: Distance changes brightness (closer is brighter, farther is dimmer) but DOES NOT change luminosity.  ALL THREE ARE RELATED.  If you know two of these, you can calculate the third.  If it is close enough for you to do a parallax calculation, you can get the distance and then be able to use THIS equation for brightness.  INVERTING THIS BECOMES A TOOL FOR MEASURING DISTANCE, which is great since parallax only works for a certain number of light-years away. Called a STANDARD CANDLE TECHNIQUE. Three stellar distances:  Parallax  Spectroscopic parallax (standard candle)  Variable star (standard candle) ▯ ▯ Magnitude Scale  Length: Meters is the scale  Brightness: Apparent Magnitude is the scale to use when talking about brightness. o First magnitude is brightest (cataloged first), and so on and so on. The higher the magnitude, the dimmer the star. o This went on into the 1800s when we started getting detectors that were able to quantify just how bright stars really were. o A difference in 5 in magnitude, really signifies a factor of 100 X brighter. First magnitude to second magnitude is 2.5 dimmer.  1 magnitude to 11 magnitude is 10. OR 10,000 times dimmer. th  A 6 magnitude star is about the limit of what the human eye can see. ▯ ▯ Luminosity: the scale for luminosity is ABSOLUTE MAGNITUDE. The exact same properties as apparent magnitude with factors, ect.  It is defined as the apparent magnitude that the star would have IF it were ten parsecs away. ▯ ▯ ▯  Measure Law ▯ Temperature: Spectrum Wein’s Law ▯ Mass: Binary Star System Kepler’s 3 Lawd ▯ Radius: Temp & Luminosity Stefan Boltzman Law ▯ Radial Velocity : Red/Blue Shift Doppler Effect ▯ ▯ If you have… ▯ Temp and Luminosity  can calculate distance ▯ Luminosity and distance  can calculate brightness ▯ ▯ DON’T CONFUSE SIZE AND MASS. You can change the size of an object without changing the mass. ▯ ▯ Stellar Spectral ▯ Oh, Be A Fine Girl, Kiss Me ▯ ▯ ▯ Hydrostatic Equilibrium gravity pushing in to keep the star from collapsing. ▯ ▯ Nova more common than supernova. ▯ ▯ Supernova a lot brighter than nova, needed another category for these newer, brighter stars.  Type II Supernova: death explosion of a high mass star  Type Ia: Not normal life cycle events. o Happens at a very specific mass? o Gives us the dark energy component to the universe we now need to understand. Recent development? White dwarf: dead body of a star cooling off. ▯ If you are below 1.4 solar mass you are a white dwarf, if you’re above it, you’re a neutron star. Black hole’s solar mass is around 3. ▯ ▯ Over Ten solar masses becomes white dwarfs ▯ Under 10 Solar Masses become neutron stars or black holes ▯ ▯ High mass stars end up as neutron stars, low mass stars end up as white dwarf stars. PICTURES ON PAGE 336 Healthy, main sequence stars mainly made of hydrogen. Chandrasekhar limit 1.4 Solar Masses. When you have a type 1a super nova, before the hydrogen starts fusing and becomes a super nova and blows itself up? After a high mass star blows up, you might have a neutron star left. Black hole Wormhole curves space and time so much that you can actually connect to places of space and time that wouldn’t normal connect.  Redefines the word “universe”; make our universe a provincial universe defined by our space and time. ▯ ▯ If we replaced our sun with a black hole of the earth’s size, what would happen to the earth’s orbit?  Nothing, because it’s the same mass and the gravitational pull would remain the same.  We are at a safe enough distance that we would not be sucked into the black hole. Even Mercury and Venus would be safe. ▯ ▯ If you are below 1.4 solar mass you are a white dwarf, if you’re above it, you’re a neutron star. We now think that galaxies have a black hole at the center of it, 2 to 3 million times the size of our star. Variable Stars (pg 383)  Cepheid ones are the ones we normally talk about o Named after the first one observed in the constellation Cephus. o Variability isn’t brightness or luminosity which change. But they get brighter and dimmer in a fairly regular fashion. o Show up on the HR diagram in a very normal sequence. o THE LONGER THE PERIOD OF THE PULSE, THE MORE LUMINOUS THEY ARE.  If you have the pulse period, you can calculate luminosity. If you can calculate the luminosity, you can calculate the distance.  STANDARD CANDLE TECHNIQUE ▯ ▯ THREE TECHNIQUES FOR MEASURING DISTANCE ▯ -Parallax (only direct method) ▯ -Variable star (standard candle)  measure the pulse period ▯ -Spectroscopic parallax (standard candle)  find the temperature, use HR diagram to calculate luminosity ▯ ▯ ▯ ▯ The Sun—don’t worry about numbers except  100 earths to go across the sun  Radius = 100 times the radius of the earth  Volume = 1000000 times that of earth  Density is like the ice giants  Temperature= 6000K o Surface temp: x axis of HR diagram o Core temp: determines whether fusion can occur or not  Luminosity – 1 solar Luminosity, compare other objects to the sun since its luminosity is so large  Composition: almost all hydrogen and helium ▯ MEMORIZE THE STRUCTURE FROM INSIDE OUT  Core- where fusion occurs that fuels the star  Radiation zone- energy propagates by radiation  Convection zone-energy propagates best by convection  Photosphere-top layer of convection zone, light produced there can escape into space for us to see. This is what we see as the surface of the sun.  Chromosphere  Corona  Solar wind-what particles blow out into the solar system, forms aurora borealis ▯ Interior of the sun  How do we study it? Same way we study the interior of the earth: looking at waves travelling through it. HELIO SEISMOLOGY ▯ What determines the size of the sun?  Gravity is always trying to make it smaller, something must always be pushing out to keep it from falling in. With the sun, it’s gas pressure from helium and hydrogen. The process of the pushing out and pushing in is called hydrostatic equilibrium. ▯ Details of the steps of fusion reaction from hydrogen to helium  Proton proton chain of events ▯ Photosphere  Sunspots found here. o Regions that are darker than the rest of the sun because they are cooler o LOWER TEMPS AND INTENSE MAGNETIC FIELDS associated with sunspots ▯ Sunspot Cycle  About 11 years in which the number of sunspots reaches a maximum and a minimum. It is HALF the duration of the solar cycle. ▯ Solar Cycle  About 22 years, in which the sun’s magnetic pole revers and return to their original configuration (Two sunspot cycles; from high to zero to low to zero to high) ▯ ▯ Brightness = luminosity/(4*Pi*Distance^2) ▯ Brightness  How much of the star’s energy is getting to your detector (aka eyes)  Apparent magnitude o The scale for describing the brightness of the object ▯ Luminosity  Total amount of energy per second that the star is putting out  Expressed in Absolute magnitude ▯ If you know brightness and luminosity, you can calculate distance.  This is called Standard Candle Technique ▯ If you know brightness and distance, you can calculate luminosity. ▯ If you know luminosity and temperature, you can calculate the radius. ▯ ▯ Magnitude scales  The higher the magnitude, the dimmer the object. o Higher = dimmer  A difference of 5 in magnitude is a factor of 100  Higher than 6 magnitude cannot be seen with the  eye. ▯ Measuring distance  ▯  Reading the graph ▯ Paralax: geometric technique ▯ ▯ Mass of the star:  Look at table in notes ▯ ▯ HR DIAGRAM  Three types of questions ▯ ▯ X axis  Temperature o Lower temperatures farther to the right (red) o Higher towards the y axis (blue/white) Y axis  T ▯ White dwarfs wold be in the lower left quadra ▯ Astronomy T est 2 02/10/2015 ▯ The Solar System  Asteroids- rocky objects- gravity does not dominate the shape of an asteroid- asteroids are bigger  Meteoroids- have rocky composition- asteroids are bigger  Comets- celestial object consisting of a nucleus of ice and dust and, when near the sun, a “tail” of gas and dust particles pointing away from the sun.  2000 in density- too low of a density for it to be rock- over 2000 are typically ice objects  1600 density- Gas giants  Terrestrial Planets- close to the sun, closely spaced orbits, small masses o Mercury o Venus o Earth o Mars  Jovian planets- far from sun, widely spaced orbits, large masses o Jupiter o Saturn o Uranus o Neptune  Differences between the Terrestrial Planets o Atmospheres and surface conditions are very dissimilar o Only earth has oxygen in atmosphere and liquid on Earth  Interplanetary Matter o The inner solar system, showing the steroid belt, earth crossing asteroids, and Trojan asteroids ▯ Earth and Moon  Moon has a core but its not metal rich ▯ Tides  are due to gravitational force on Earth from Moon- force on near side of earth is greater than force on far side. Water can flow freely in response  The sun has less effect, but it does modify the lunar tides  Tides tend to exert a “drag” force on Earth, slowing its rotation  This will continue until Earth rotates synchronously with the moon, so that the same side of Earth always points towards the moon  This has already happened with the moon, whose near side is always toward Earth ▯ Ozone and Greenhouse-  Chlorofluorocarbons (CFCs) have been damaging the ozone layer, resulting in ozone hole  There is extremely strong evidence that Earth is getting warmer. The cause of this warming Interior  Seismic waves ▯ The surface of the Moon  The moon has large dark flat areas, due to lava flow, called maria (early observers thought they were oceans)  The far side of the moon is relatively unmarked  Far side of the crest is a lot thicker ▯ ▯


Buy Material

Are you sure you want to buy this material for

75 Karma

Buy Material

BOOM! Enjoy Your Free Notes!

We've added these Notes to your profile, click here to view them now.


You're already Subscribed!

Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'

Why people love StudySoup

Jim McGreen Ohio University

"Knowing I can count on the Elite Notetaker in my class allows me to focus on what the professor is saying instead of just scribbling notes the whole time and falling behind."

Kyle Maynard Purdue

"When you're taking detailed notes and trying to help everyone else out in the class, it really helps you learn and understand the I made $280 on my first study guide!"

Bentley McCaw University of Florida

"I was shooting for a perfect 4.0 GPA this semester. Having StudySoup as a study aid was critical to helping me achieve my goal...and I nailed it!"


"Their 'Elite Notetakers' are making over $1,200/month in sales by creating high quality content that helps their classmates in a time of need."

Become an Elite Notetaker and start selling your notes online!

Refund Policy


All subscriptions to StudySoup are paid in full at the time of subscribing. To change your credit card information or to cancel your subscription, go to "Edit Settings". All credit card information will be available there. If you should decide to cancel your subscription, it will continue to be valid until the next payment period, as all payments for the current period were made in advance. For special circumstances, please email


StudySoup has more than 1 million course-specific study resources to help students study smarter. If you’re having trouble finding what you’re looking for, our customer support team can help you find what you need! Feel free to contact them here:

Recurring Subscriptions: If you have canceled your recurring subscription on the day of renewal and have not downloaded any documents, you may request a refund by submitting an email to

Satisfaction Guarantee: If you’re not satisfied with your subscription, you can contact us for further help. Contact must be made within 3 business days of your subscription purchase and your refund request will be subject for review.

Please Note: Refunds can never be provided more than 30 days after the initial purchase date regardless of your activity on the site.