Chapter 4 and 5 notes
Chapter 4 and 5 notes ASTR 1010
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This 13 page Class Notes was uploaded by Brandon Carpenter on Wednesday February 24, 2016. The Class Notes belongs to ASTR 1010 at Clayton State University taught by Harold Banke in Spring 2016. Since its upload, it has received 13 views.
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Date Created: 02/24/16
Astronomy notes Astronomy Notes Geocentric viewpoint- everything revolves around us. Heliocentric viewpoint- we revolve around the sun but not center of universe. Cosmic address: the location in the universe. 1. Planet 2.Moon 3.Star 4.Solar System 5.Galaxy 6. Universe Andromeda Galaxy is 2.4 million light years away Light year is the distance light travels in a year. Light minute is the distance light travels in a minute. Universe is expanding from a small point created from a "big bang" Hydrogen is main composition of starts, two hydrogen atoms fusion producing helium. Supernova is an exploding star. Most stars come in pairs. There are 100 billion stars in the Milky Way galaxy. The super nova caused the elements to get out of stars. 24,000 miles around the earth at the equator = 24 hrs. to go around the curve. This is basically 1000 miles an hour rotational speed. Revolutionary speed is about 60,000 miles per hour. Can't tell motion when motion is constant, only the change in motion. Astronomical unit is the distance from sun to earth. 230million year orbit, rotation of galaxy is about 800,000km/hrs. or 500,000m/hr. Dark matter has gravity but does not reflect/emit light, this holds the stars in orbit Dark energy is causing the universe to go faster and faster Edwin Hubble 1920's discovered we were not the only galaxy, every other galaxy APPEARS to be moving away from us, farther away from us the faster they travel away from us. There is nothing to compare speed to so we can’t tell how fast we as a planet actually are moving. Took us 13.5 billion years to get we are now. Stars in our galaxy is fixed, they are not getting bigger nor is the galaxy. The space of the universe between galaxies are expanded, 6000 total stars are able to be seen in the best conditions at night. 60th of a second is the time that light is allowed into our eyes. Stars that looked to be in the same area relative to us are names constellations. Winter Triangle contains: Betelgeuse, Rigel and Sirius. Canis Major star group, named big dawg, Sirius is part of this group Sirius is the 4th brightest light in the sky most nights; it’s very close and the brightest. Order of brightest to weakest: sun, moon, Saturn and then Sirius. Babylonians looked to see the sun come up against background of different stars every day. This would be their time tracking ability, every day there would be different stars until eventually they came back to the same. They broke up the times of the year that the sun would be the same place, became our months eventually. 12 constellations for 12 months, Started their year in the constellation Aries Eventually 88 constellations came about for 88 sections by the international astronomical union. Useful to know where they are so people can know what you're looking at, narrows locations in the skies. Gave us ways to name stars that are out there in the sky. Would say Alpha Canis Majoris for the astronomical name for Sirius. Means that it is the brightest of Canis Major group. Alpha Centari means that it’s the brightest star in the constellation Centaurus. The ‘I’ ending means "of", alpha means brightest. Ancient romans believe the sky was a crystal sphere and thought the stars were dots of light. Believed that we were rotating in the center of this "celestial sphere" Used to describe the apparent sphere of the sky around us, landmarks for navigating at night. The point that appears to not turn at all refers to the "north celestial pole" at the North Pole of the earth. The point that appears to not turn at all refers to the "south celestial pole" at the South Pole of the earth. Split in the middle of the earth would be a dividing line of north and south hemisphere of the sky, known as the "celestial equator" Another point is the "ecliptic" that appears to be moving around this celestial sphere. Greeks had a myth (explanation about something that is mysterious) about this strange swathe of milky stuff during the summer. Believe that this swathe was god having spilled milk onto the sky, "milky way" Greek word for milk was 'galaxy'. Galileo saw this swathe through telescope and discovered it was a lot of stars condensed and was the actually galaxy. Local sky is the half of the sky above you, the zenith is the point directly above your head. Zenith is 90 degrees about the horizon is the altitude, top point in the pole is the north celestial pole. Stars rotate counterclockwise around the zenith of the north celestial pole. Polaris is at the north celestial pole. Polaris (North Star) doesn’t seem to turn at all. Will have to look at the horizon directly on the ocean to see North Star when on the equator. 31 degrees in the sky over morrow Georgia. Half circle going across the local sky through the zenith is called the meridian. The highest point a star goes through in the night is a point that has to cross the meridian. Will say something like “crosses the sky at 34 degrees past the meridian at 1 in the morning” Have to tell the compass direction or “azimuth” and the altitude. So SE at 60 degrees above the horizon. Circumpolar stars are stars that seem to move around the north Celestial pole. Never rise nor set. Don’t have to be at the North Pole to see these circumpolar stars however. The angular size of the moon is about (1/2) degrees, which is also the size of the sun. Angular size does not tell the actual size of the object out in space. But if you know angular size and distance you can figure out actual size. Moon crosses in front of the sun for a solar eclipse. Anything smaller than a degree is an arc, so arc minute then arc second. Arc second is one thirty six thousandths of a degree. Uranus and Pluto rotate counter clock wise but on their horizon, spinning on a horizontal axis. Saturn rotates clockwise on its axis due to being knocked over. Stars moving in the western hemisphere, will go down over the horizon towards the west, not straight down however. Going straight up and straight down only on the equator, you are in North Pole look as if they go around you not up or down. Latitude is from 0 to degrees north and south of the equator. In the sky latitude is similar to the altitude of the celestial poles. If you are on the same latitude you will see the same stars no matter what longitude, just different times Longitude is from 0 to 180 degrees east and west of the prime meridian. In the sky we call them Stars we see in the night depends on the latitude, time of the night and the time of the year. Changes in temperature are due to the position of the axis, tilted at 23 1/2 degrees. January is Parahelium is closest to the sun, Apt Helium is farthest away. Two effects, changes in light concentration and changes in length of daylight Solstice is that we are standing still, stopping at solstices. 4 things happen during winter solstice 1. Sun Stops moving south, rises as far south on the horizon as it ever does 2. The northern hemisphere is tilted at a maximum away from the sun. 3. The northern hemisphere receives the least amount of daylight. 4. Winter season “begins” 4 things happen during summer solstice 1. Sun Stops moving north, rises as far north on the horizon as it ever does 2. The southern hemisphere is tilted at a maximum away from the sun. 3. The southern hemisphere receives the least amount of daylight. 4. summer season “begins” in Morrow: 1 day in the year sun rises due east, spring equinox 2 day in the year sun rises due east, fall equinox Only in the tropics does the sun pass the zenith, overhead directly. Summer solstice the Sun is the highest altitude; winter solstice is lowest altitude. Southern hemisphere is known as the sea hemisphere, northern is known as land hemi. Sea hemisphere holds the temperature better than the ground. El Nino- water movement in the pacific. that is unusual, affects the temps on the earth. Earth wobbles, due to gravity, called procession-wobble of a spinning object. Earth’s wobble is very slow; we no longer have sun rising as it did 3000 years ago according to zodiacs. Moon has a 380,000km distance from earth, Sun has a 150,000,000km distance from earth. Closest to the earth is Perigee, apogee would be the farthest from the earth 27 1/3 days to go around the earth for the moon, phases of the moon take 29 ½ days to take place. Super moon occurs when full moon is at the perigee, moon rises and sets because earth spins. Moon is so close that it actually moves in the sky a little to the east, going in the same direction we are. Moon rises and sets at different times during the month, takes us 50 minutes to catch the moon. Rises 50 minutes later every day, as it turns the moon receives different amounts of sunlight. New moon rises at dawn, full moon rises at sunset. Very slow rotation, time it takes to go around earth is the same time it takes to make a full rotation. Rotation period = revolution period. Eclipse is the darkening of one body by the shadow of another. Umbra is the Lunar eclipse is the darkening of the moon with earth’s shadow. Moon is in the Full Phase Moon is crossing the ecliptic plane, passing through a “node” in its orbit. Solar Eclipse is the moon getting between the earth and the sun. Moon is in the NEW phase Moon is crossing the ecliptic plane, passing through a “node” in its orbit. Ecliptic plane is the imaginary surface around the sun, moon’s plane is tilted about 5 degrees. Travels a bit above and below the plane, as long as it’s on the plane you can have eclipse. Red light is refracted very noticeably during a lunar eclipse, producing the effect know as a blood moon. Moon never becomes completely dark during a lunar eclipse. 7 Wanderer’s: Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn Wanderer is Greek for Planet there for these were called planets back then. Most of these planets went through retrograde motions, or backward motions. Ancient Greeks (600B.C. – 200A.D.) Ancient Greeks developed major innovations that helped paved the way for modern science. Aristotle believed that the eclipse meant sun was behind the earth casting shadow on moon. Discovered that earth wasn’t flat because of the shadow was curved on the moon. They developed a tradition of trying to understand nature without resorting to supernatural explanations. Used mathematics to give precision to their explanations. They began to understanding the power of reasoning from observation. Arisosthenese measure the earth with sunlight and measured size of angle and shadows. Estimated that the complete circumference around the earth is about 24,000 miles/40000 kilometers. Aristarchus(260bc) used geometry to measure the sun and earth and discovered the sun was much bigger than the earth, started wondering what made sense: small around big or big around small. Came up with the idea that the earth goes around sun, Ptolemy was the Greek who came up with the idea of retrograde motion, threw away the idea of orbits. Smaller circles called epicycles, two of which exist, planet appears to go in the opposite direction. Copernicus came up with the heliocentric model, Aristarchus could have influenced him. Tyco Brahe collected data for about 30 years using the naked eye, hires Johannes Kepler to do the data. 1 law of planetary motion is ellipse- sun is at one foci. 2nd law states imaginary line equal area at different times, planet moves frdter when it is close to the sun. 3 law states that more distant planet travel more slowly than less distant planets. P squared = a cubed, p = orbital period time, a = distance. Creates the semi major axis using the average of these. 4AU is 8 years, square root of 4 cubed equals 8. 10AU is 31.6 years, square root of 5 cubed equals 31.6. 7 years is about 3.66 AU, cubed root of 7 squared? Galileo Galilea (1564-1642) [Shakespeare birth, Newton death] First person to use the telescope for astronomy, 1609, made a number of important discoveries. - Noticed that Jupiter has four moons orbiting it, proved that Earth is NOT the center of the earth. These were named the four Galilean moons due to his discovery. - He observed there were phases of Venus, this had been predicted by the heliocentric model. Copernicus said we would never be able to see the phases with naked eye, Galileo used telescope proved the existence of the Venusian cycle. - He also observed that the moon is no perfect, it had craters, mountains and lines; world like our own. Believed there were oceans on the moon, that’s why names are such as Sea of tranquility - Observed the sun, found more imperfections called sunspots, maximum every eleven years, sun also rotates on his axis. Went blind years later possibly due to looking at the sun. - Discovered that the Milky Way was a galaxy full of stars, there were more distant than imagined, some were not visible to the human eye. This allowed the “Stellar Parallax” (shift) to go missed because we could not see it with the naked eye. Galileo was convicted of heresy, and sentenced to house arrest for his entire life, however his works became well known after his imprisonment. Continued writing even after losing his eyesight. The catholic court case was finally overturned after 300 years, they finally admitted Earth revolves around the Sun in 1992 for this particular case. A hypothesis is an idea that will be tested but a theory is an idea that has been tested. The ideas that cannot be tested are not called scientific. Celestial timekeeping and Navigation Summer solstice, sun never goes down for a period of times. Day is determined by the movement of the sun, 1 day is called a Sidereal day, 1 is called solar day. Sidereal refers to the sun, Solar refers to the sun Sidereal is the time it takes any star to make a circuit of the local sky, takes about 23 hrs and 56 minutes Solar is the time it takes the sun to make a circuit of the local sky, takes about 24 hrs. Because we are in orbit around the sun we take four minutes longer than the Sidereal time Sidereal is just the time it takes us to rotate around the axis alone, stars in the sky appear in same place. Solar is the time it takes to point back at the sun at noon, four more minutes on the rotation due to the revolution around the sun. 7 Days of the week because of the 7 wanderers, one week passed when it’s only first quarter of phase. Month (month, due to the moons time periods) time it takes for moon to goes through its phases. Named after the 7 wanderers, Sun-Sunday, Moon-Monday, Mars-Tiw- Tuesdays, Mercury-Woden-Wednesday, Jupiter-Thor-Thursday, Vens-Fria- Friday, Saturn-Saturday. Sidereal Month is 27 1/3 day- got to see the same star every 27 1/3 days, time it takes to orbit the earth. Synodic month is 29 ½ days- time it takes to go through all its phases, its orbiting earth. Synodic means meeting together, Lunar calendar is used with moon phases, 12 cycles equal a year. A day is not related to the year at all. A year is 365.2422 solar days it takes to orbit around the sun, tropical year. 4000 years ago Egyptians used Cirius to mark their calendars with 365 days. (wrong of course) Sun appears due east only during the Equinoxes, sundials used shadows of the sun when pointed due North Apparent solar time, actual time sun crosses meridian, called noon, Sundial only measures noon in Your location, not just all days. Mean solar time, measures the average time the sun crosses the meridian at a given location. The solar days vary in length because of the earths orbital speed varies due to it elliptical orbit. Eventually these times can add up to 17 minutes between the apparent solar time and the mean solar time, the solar day can vary as much as up to 25 seconds. th Defined as 1/24 of a solar day, 1 hr., mechanical clock records exactly 24 of these. The world decided to split into 24 different time zones. Line in the middle would determine noon for the whole area of the time zone. Time in the zone is the standard time, universal time is the single time for the entire earth, called the zulu time or Universal coordinated time-(UTC) zero- time zone is the prime meridian, Grinige, England, is famous for its observatory. Daylight savings time is changing clocks so that we automatically get up an hour earlier, due to summer having longer hours. Romans were first to recognize that the year was more than 365 days long. Julius Caesar realized that the calendar needs to be changed to keep up with the seasons. Believed to be 365 ¼ days long, made average year this, Julian calendar th allowed this by adding an extra day into the calendar by making the 4 year a leap year with 366 years. Adding up 365*3 + 366 then divide by 4 and you get the 365 ¼ days Tropical Year – 365.2422 not equal to 365.25 – Julian Year 11 minutes off. The calendar was off by 10 full days, would mess up the catholic holiday. 1582-Pope Gregory, Gregorian calendar- leap years except for the century years that are not divisible by 400 exactly. For this century we do not count 2100 as a leap year. Chapter 4 Motion can be described using several general terms: Speed is the rate of change of position, measured in units such as m/s or km/h Velocity is the rate of change of position in a certain direction such as 29 m/s, W Acceleration is the rate of change of speed or velocity, measured in units such as m/s/s (m/s squared) Gravity is 9.8 meters per second per second, there is no terminal velocity in space. Terminal velocity is when air resistance is the same as the gravity. Mass is the amount of matter in an object, weight is the pull of gravity on you. Object is in free fall only if the force acting upon it is gravity. Momentum is a characteristic of a moving object defined by the product of objects mass and velocity. Described as Momentum = Mass X Velocity. Collision is the transfer of MOMENTUM from on object to another. Force is an influence that changes momentum, pound is the American amount of force from g. If in elevator, the APPARENT weight would increase as the elevator increases velocity, at cruising speed you read the same as actual weight, as elevator is pulled down the apparent weight is decreased, in free falling elevator you become weightless. Orbit is freefalling around the earth, blasted out just right so trajectory matches the curve the earth. Hundreds of satellites launched into orbit using Newton’s laws of motion, have to travel faster than 17,000meters per second. Optics, calculus, astronomy- all influenced by Newton, gravity extended beyond the earth. Newton was first in astrophysics, discovered the 3 laws of motion- 1 An object at rest or in uniform motion in a straight line will remain that way forever, unless acted upon by a net, external force. a. Just means that an object moves or stays at rest until outward force is acting upon these object in rest or motion b. Horse carriage does not come to stop because the horse break free, friction cause the carriage to stop, not because the horse stopped pulling. c. Space craft keep going until the planets gravity pulls it into orbit. Kept going because there is no friction in space, planets can help “sling-shot” satellites out into space. 2 The acceleration of an object is directly proportional to the net, external fore applied to it, and inversely proportional to the objects mass. a. Means that if you have an object and you push on it with more or less force, object moves faster or slower due to that push b. If you have an object with one mass and the next object has 2x mass of one object, then the force you push on object will be proportional to the weight. c. Force = mass times the acceleration 3 For every force there is an equal but opposite force. a. For every force there is an equal but opposite reaction force. As mass gets bigger the acceleration is smaller, a rocket does not have to push on the ground Conservation laws-reflections of laws of gravity. Law of conservation of Momentum: the absence of net, external force, the total momentum of system remains constant. (neither destroyed or created) If in space, rocket will continue forever without thrust. Law of conservation of angular momentum- spinning on a top, radius * mass * velocity Distance is greater from the sun so speed is slower, distance is smaller closer to the sun so the speed is greater Linear Momentum is the tendency for an object to keep going in a straight line, mass * velocity When radius increases, mass has to increase and speed must decrease. Law of Conservation of Energy- energy can not be created or destroyed, only transformed. - A moving object or particle can do work thus having kinetic energy - Light and other forms of radiation can do work because of there radiative energy - Potential energy is stored in objects in a force field, suck as a book on top of a shelf. o Gravitational Potential Energy (book on shelf) o Chemical Potential Energy (molecules in fuel) o Mass Energy (hydrogen bomb- nuclear fusion) Squeezing two hydrogen molecules combined to less than 2, the remaining mass becomes the missing mass turned into energy. Mass decreases with nuclear fusion. o Heat Energy: higher temperature higher kinetic energy, how fast molecules are moving. Molecular motion will cause the disruption of skin and burn. Particles moving fast give you higher temperatures. Measured in Fahrenheit, Celsius, and Kelvin. Water at 212 degrees causes more damage that oven at 400 degrees Water has more energy because the molecules are compact. If you are up in the atmosphere, you have temp of 2000 degrees but very little heat, if you take off suit, you freeze because your infrared heat is given away and you lose your heat. - Gravity was calculated by newton with the equation: o Force of gravity equals a numerical constant times (Mass of object 1 times time mass of object 2) divided by the distance between objects squared. o Fg= G(m1*m2)/d^2 o Will be proportionately changed depending on the variables. Force will be increase by product of multiplied constant of the mass. Force will be decreased if the distance is increased Any changes in distance will make a bigger effect on gravity. - Orbits allowed by laws of gravity o Bound elliptical orbit- escape velocity (on earth: 11.2 kilometers per second) o Unbound parabolic orbit- o Unbound hyperbolic orbit- Einstein believed gravity would warp space and objects coming near it will roll towards it. Two high tides, two low tides, two bulges all the times because moon pulls one way. The water on the closer bulge is higher tide, the water on the other side is lower tide on the side that pulls less and has water left behind. Bulges are pulled towards the direction of the moon, 50 minutes later every day for high tides. 12 noon is high tide today. 12:50 tomorrow is when high tide would come in. Full/new moon at beach, water comes up highest, first/third quarters lowest tide Bulges should be towards the moon but due to earth spinning as well, water is pointed towards ahead of the and the moon tries to pull tides in to line and this slows the earths rotation. Earth rotation is slowing down and at the same time earth speeds the moons orbits. This has effect on the size of its orbit, this being that the orbit gets slowly bigger and bigger. CHAPTER 5 LIGHT AND MATTER We know we can see stars because they give off a lot of light. List of once what was impossible to know in 1700’s - Composition of stars. o Now we know: composition, size, temps, brightness, lifespan, and movement o We can evaluate a lot things using light spectrum to evaluate it. o Light is radiative energy, that’s how stars emit light energy. o Joules, electron volt (small amount inside atom) Power is amount of energy per unit of time. Power = E/T. Joules per second. 1joule per second = 1 watt. o 60 watt bulbs emit 60 joules every second, sun power is 3.8x10 to the 26 watts or 3.8x10 to the 26 joules per second, given off as different forms of energy. o Ultraviolent has a lot more energy than standard bulb, can burn skin, lower than violet light rays in the rainbow o Infrared is the heat given off matter warmer than absolute zero. Higher than red rays on rainbow. Light interacts with matter in 4 different ways: - Emitted from matter, such as light bulbs - Absorption into matter, black absorbs light and white combines it all, all colors are reflected from the object. - Reflection, plants are green because they absorb all colors except green, if placed in blue light, they would be black because they have no colors being reflected, if placed in green lighting it would reflect green and be green but it would not be healthy and after awhile it would die off. o Scattering is when light bounces off a rough surface to spread all around the room. - Transmission, light passes through glass in which it moves through the atoms. Light is absorbed into your retina. Light absorbed into the snow cause the molecules move faster and then melt. Absolute zero is when molecules do not move and is 0 degrees Kelvin. Optics deal with lights and lenses- experimented with by newton. Refraction deals with light waves bending and light is not made of atoms, newton was wrong in this hypothesis. Light consisting of waves theory came after newton, 1800’s and beyond. Light consist of trophs and crests, wavelengths and frequency and speed. Different waves have different wave lengths- measured in meters per cycles: goes up down then back up, repeating itself as one cycle after another, distance wave travels in one cycle. Greek letter for l- lambda is the symbol for wave length. Going up and down is the cycle, if you count the number of times it goes up and down you get the frequency of a wavelength, counts the cycles and time. We can call cycles per second “Hertz” 92.9 MHz is 92.9 million hertz or cycles per second - FM 1000 KHz is 1,000,000 hertz or cycles per second – AM Longer length, fewer cyclers. Low frequency has long wavelength Ultraviolet has shorter wavelengths. Wavelength times frequency is its Speed (velocity). 1 meter per cycle, 5 cycles per second = 5 meters per second.
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