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Unit 8 Chapter 26 Studying Space Section 1 Viewing the Universe Astronomy is the study of the universe Astronomer is the scientist that does the studying The Value of Astronomy As new things are discovered in space like Black Holes, new planets, stars and nebula, scientists can use that information to learn about Earth. Scientists have been able to piece together the processes that involve the formation of our planet, the solar system and the universe. Characteristics of the Universe Cosmology is the study of the origin, properties, processes and evolution of the universe. The Universe began approximately 13.7 billion years ago in what we feel was a “Big Bang”. Organization of the Universe Our nearest part of the universe is our solar system. Our solar system is part of a galaxy which is a collection of stars, dust, gas and other objects bound together by gravity. Our galaxy name is the Milky Way (candy named after it). Measuring Distances in the Universe Astronomical Unit (A.U.) is the average distance from the earth to the sun which is 149,597,870.691 km (150 million) Light Year measures the distance that a ray of light travels in one year, which is approximately 9.46 X 1012 km 1 light year = 9.5 X 1012 km 1 A.U. = 1.5 X 108 km This means that there are 6033 X 104 A.U.’s per light year. The next closest object to us aside from out sun is approximately 4.22 light years away. Electromagnetic Spectrum Spectroscope/Spectrograph It is an instrument that uses prisms to split light, a special telescope and a special camera to look at stars. Each star emits its own spectrum because each star is made of different elements and each element emits a different wavelength. Continuous SpectrumThey are an unbroken band of color which shows that the source is emitting all visible wavelengths. It can be either a glowing solid (hot filament of light bulb) or a glowing liquid (molten iron, lava) or a hot compressed gas. Emission SpectrumThese are unevenly spaced lines of different colors and brightnesses. Bright lines mean light of only certain wavelengths can be glowing thin gasses (Florescent bulbs). Absorption SpectrumIt is a continuous spectrum crossed by dark lines. This happen when light passes through a cooler gas, actually the elements in the gas absorb exactly the same wavelengths that they would emit if they were hot and glowing. Visible Electromagnetic Radiation Visible Spectrum is the part of the electromagnetic spectrum that human eyes can see. We see the colors of a rainbow, Red (longest), Orange, Yellow, Green, Blue and Violet (shortest). White light is made up of all of the colors in the spectrum. Color shifts are used to visualize the movement of objects toward and away from the observer. We use this when we work with meteorological maps and viewing objects in space. In labs the changes are either to the red or the blue side of the spectrum. RED SHIFT- SHOWS THERE IS AN INCREASING distance There is a wavelength increase BLUE SHIFT- shows there is a decreasing distance There is a wavelength decrease Erwin Hubble discovered that most stars are red shifted. It means that all stars are moving apart and the universe is expanding Invisible Electromagnetic Radiation Invisible radiation is the radiation that we can not see but we can feel it and experience it. It will usually involve a temperature rise. In the 1800 William Heschel discovered that there was a rise in temperature in the red end of the spectrum if you placed a thermometer in it, hence the name Infrared, which means below red. Doppler Effect is the apparent change in the frequency of an object as it moves towards or away from an observer. It can be sound or light. Example- The sound of a siren as it comes towards you and then moves past you. The pitch grows higher as the vehicle approaches it compresses and makes the wavelength shorter (higher pitched) as the vehicle goes away from you the wavelengths increase in size and the pitch drops. Telescopes A Telescope is used to help our eyes see further and more clearly into space. Although he was not the first to make it, Galileo was the first to use it to see the “heavens”, since it was originally used to look for ships and pirates. They gather more light than our eye can and can magnify images. The best place to use a telescope is in a place that is away from light and as high as possible. Why? Refracting Telescopes Refracting Telescopes use two lenses to bend and then focus the light. The bad thing about them is that it is hard to make big lenses for the instruments, so they tend to be smaller. Also if you focus in on one color, you will be out of focus in another. Reflecting Telescopes Reflecting Telescopes use a curved mirror to focus the light and an eyepiece lens to magnify the image. Sir Isaac Newton first introduced this. These telescopes are usually about 10 meters in diameter. The Keck telescope in Hawaii is the largest of these so far. If smaller multiple mirrors are used instead of one big one it is called a Multiple Mirror Telescope (MMT). Astronomers are planning are making larger ones. An ELT, Extremely Large Telescope at about 50meters and the OWL, Overwhelmingly Large Telescope at about 100 meters are in the works. Telescopes for Invisible Electromagnetic Radiation A Radio telescope uses radio waves instead of light. It collects the sound waves from space and transmits them into an instrument that looks like a dish. In New Mexico there is an array of them able to act as one, the Very Large Array (VLA). This enables astronomers to hear radio waves from outer space (like the movie Contact). Space Based Astronomy In Space, Earth’s atmosphere can not interfere with the detection of electromagnetic energy. Space Telescopes Hubble Telescope A telescope launched in space from the space shuttle that enables us to see 12 billion light years away. Named after Erwin Hubble who discovered that most (all) stars is red shifted Other Spacecraft Since the 1960’s we have been sending things into space to do the exploring for us. 1977 Voyager 1 and Voyager 2 investigated Jupiter, Saturn, Uranus & Neptune 1995-2003 Galileo orbited Jupiter 2004 Cassini orbited Saturn 2004 Huygens studied the surface of Titan 2004 Mars rovers Spirit and Opportunity landed 2008 Phoenix found ice on Mars Human Space Exploration The first humans went into space in the 1960’s. Between 1969 and 1972 12 humans have landed on the moon. NASA is still researching and sending crews out to space stations now. Spin-offs of the Space Program We have satellites that we use to help us see and hear things better, for commercial or government use. Medical equipment is also being experimented on in the space station for use on earth. Section 2 Movement of the Earth If we can understand the motions of the Earth, we can understand the motions of other bodies in our solar system. The Rotating Earth The earth rotates counter clockwise as seen from above the North Pole (from west to east). The earth rotation and its tilt also cause: changes in the amount of sunlight per day length of the day (24 hours) direction of the sunset; Summer – north of West Winter – south of West direction of sunrise; Summer – north of East Winter – south of East Apparent movement of the sun across the Sky The earth is 40,074 km at the Equator, it rotates 15o/hr therefore it must rotate 1670 km/hr. At the north and South Pole, it rotates at the grand speed of 0 km/hr. At 41o N Lat. It is approximately 1325 km/hr. The Foucault Pendulum In 1851 Jean Foucault constructed a freely swinging pendulum that appeared to change its direction in a very predictable manner. The pendulum appeared to move 15o per hour. The Coriolis Effect Objects in the Northern Hemisphere appear to go to the right Objects in the Southern Hemisphere appear to go to the left The Revolving Earth As Earth spins on its axis, it also travels around the sun. The average speed of the orbit is approximately 29.8km/s which takes us about 365 ¼ days to go around the sun. Earth’s Orbit Because the earth’s orbit isn’t a perfect circle we are closer in the winter and further away in the summer. Aphelion-July 4 furthest from the sun Perihelion Jan. 2 closest to the sun http://www.windows2universe.org/physical_science/physics/mechanics/orbit/perihelion_ aphelion.html Constellations and Earth’s Motions Evidence of Earth’s motions can also be seen in the motions of the constellations. Constellations Are groups of stars that seem to form an object or Pattern. They were named for mythic heroes. 88 constellations can be seen from Earth’s northern and southern hemispheres. Evidence of Earth’s Rotation All stars appear to move in an arc in the sky except for Polaris. Why ____________________________________________________ Evidence of Earth’s Revolution Not only does the daily position of celestial objects change, the position changes throughout the year, why? ___________________________________________________ Measuring Time Earth’s motion provides the basis for measuring time. Each day is divided into 24 hours. A year is divided into 365 ¼ days and a month was based on the cycle of the moon which was approximately 29.5 days. Now it is based on being 1/12th of the year. Formation of the Calendar A calendar is a system created for measuring long intervals of time by dividing time into periods of days, weeks, months, and years. Because the year is about 365 1/4 days long, the extra 1/4 day is usually ignored to make the number of days on a calendar a whole number. To keep the calendars on the same schedule as Earth's movements, we must account for the extra time. So, every four years, one day is added to the month of February. Any year that contains an extra day is called a leap year. The Modern Calendar Because the year is not exactly 365 days long, over centuries, the calendar gradually became misaligned with the seasons. In the late 1500s, Pope Gregory XIII formed a committee to create a calendar that would keep the calendar aligned with the seasons. We use this calendar today. In this Gregorian calendar, century years, such as 1800 and 1900, are not leap years unless the century years are exactly divisible by 400. Thus, 2000 was a leap year even though it was a century year. However, 2100, 2200, and 2300 will not be leap years. Time Zones Standard time zones the world is divided in 24 different time zones each 15o of longitude, called time meridian. International Date Line International Date Line – because of the changes of time either ahead or back, people can lose or gain a whole day. This line (imaginary) represents where the date will change. West – one day ahead East – one day earlier Daylight Savings Time Because there is a different amount of day light hours in the winter and summer, the United States decided to adjust out clocks to accommodate this. We turn our clocks ahead in the spring, in which we lose an hour of time, and then we fall back, in which we gain an hour. This was due to help with the energy crisis. The Seasons Since our axis is tilted about 231/2o off of perpendicular this which means that a different area of the earth receives different amounts of light each day. And since it takes us 12 months to complete a revolution around the sun, it takes approximately 3 months to change the area being exposed. Seasonal Weather As the Earth moves, it causes changes in the area exposed which creates different weather in areas on the earth. So the seasons are caused by the tilt of Earth's axis and not by Earth's distance from the sun. Equinoxes Spring – March 21st (Vernal) Fall – September 23rd (Autumnal) Sun is directly above the equator, 12 hrs of daylight all over the earth Sun Sets directly West and Rises directly East Summer Solstice Summer Solstice (June 21st) Direct rays of the sun on Tropic of Cancer 23 1/2o North Latitude 15 hrs of daylight on L.I. (sunrise N. of E.) 24 hrs of daylight on the North Pole 12 hrs of daylight on the Equator 0 hrs of daylight on the South Pole Winter Solstice Winter Solstice (December 21st) Direct rays of the sun on Tropic of Capricorn 23 1/2o South Latitude 9 hrs of daylight on L.I. (sunrise S. of E.) 0 hrs of daylight on the North Pole 12 hrs of daylight on the Equator 24 hrs of daylight on the South Pole Zenith – point directly over head The sun is NEVER at the zenith anywhere in the contiguous U.S. Altitude – suns angle with the horizon The altitude is measured in degrees from the observer’s horizon to the object. There are 900 from the horizon to the Zenith.