Notes.pdf

1. For Our Eyes Only Frames of Reference When you look up in the sky, you’ll see the Sun move through the sky in the daytime and the Moon, stars, and planets move through the sky at night. Objects appear to rise in the east and set in the west due to Earth’s rotation. However, it feels as though E...

1. For Our Eyes Only Frames of Reference When you look up in the sky, you’ll see the Sun move through the sky in the daytime and the Moon, stars, and planets move through the sky at night. Objects appear to rise in the east and set in the west due to Earth’s rotation. However, it feels as though Earth doesn’t move. A long time ago, people believed that everything rotated around Earth. Everything appears to move from our frame of reference. This is a set of axes of any kind that is used to describe the positions or motions of things. For example, the equator and prime meridian are the axes that we use to describe horizontal and vertical locations (longitude and latitude) on Earth. In another example, a bus of school children drives by you at 50 km/h as you are standing on the sidewalk. The bus and children are going 50 km/h compared to you. You are the frame of reference. However, the bus is not moving compared to the children. Here, the children are the frame of reference. What Our Ancestors Saw Ancient peoples watched the motions of celestial bodies (the Sun, Moon, stars, and planets). Ancient civilizations, such as the ancient Greeks, Babylonians, Hindus, and Egyptians, built up a body of knowledge from their observations: The stars make unchanging patterns in the sky called constellations. These patterns look like objects. On each successive day, a given star rises and sets fur minutes earlier than the day before. This means that over a period of months, different stars are in the night sky. Each month has its own set of stars, which helps people to predict the changing of the seasons and create calendars. The Sun rises and sets at a rate different from the stars. The Moon also rises and sets at a rate different from the stars. The moon also shows phases. Five other bodies – Mercury, Venus, Mars, Jupiter, and Saturn – rise and set at rates different from the stars. The ancient Greeks considered these to be special stars, which they called planets, from the Greek word “wanderer.” The stars appear to revolve around one point in the sky, which is very near Polaris, or the North Star. Polaris never rises or sets, so early people used it to find direction at night. The southern hemisphere doesn’t have a South Star, but instead has the constellation Crux (the Southern Cross), whose long axis points toward the South Celestial Pole. Ancient Legends Many ancient societies created stories to explain the origin and movements of the celestial bodies. The Algonquin, Iroquois, and Narragansett saw the constellation Ursa Major as a bear running from hunters. According to some stories, because the bear is low enough to brush the maple trees in early autumn evenings, blood from its wounds turns the leaves red. The Snohomish have a legend that tells how three hunters chasing four elk became the seven stars of the Big Dipper. One of the hunters is accompanied by a “dog,” which you can see if you look carefully at the middle star in the handle. 1 Space Exploration Sky Coordinates Sometimes ancient peoples, as early as the ancient Egyptians, wanted to accurately measure the celestial bodies’ locations in the sky. They would give a celestial body two coordinates measured in degrees. 1. The azimuth (also known as a bearing) is an angle measured clockwise from north. 2. Next, measure the altitude by measuring the celestial body’s angle above the horizon in degrees. These two angles are called altitude-azimuth coordinates. They locate a celestial body relative to a fixed Earth (as though the celestial bodies are circling Earth). The altitude-azimuth coordinates for each celestial body change depending on the time of the reading, e.g. the Moon’s location changes throughout the day. Look at the diagram and write your own definition for zenith: An astrolabe is a device used to measure the altitude of an object. It was invented by the Greeks. The pointer on it is aimed toward a star. The angle (altitude) is measured from the horizontal. A compass is used to measure an object’s azimuth. With these tools, navigation was improved and the great sea explorations of the world began. The Stars as a Frame of Reference Because of Earth’s rotation, the stars and planets appear to circle above us. To track the movement of each celestial body (such as the Sun, Moon, and planets), you need to compare their motion to the stars. This is because we are looking for motions in the sky that are different from the big motion caused by Earth’s rotation. It is simple to use the stars as a frame of reference. Suppose you want to see the actual movements of the planet Mars. Find Mars in the night sky. Next, find a few very bright stars near Mars. Mark down Mars’s position relative to those few bright stars. The next night you would find Mars and the few bright stars in the sky again. Mark it down. If you made similar observations over several weeks, you could see in which direction Mars is really moving. The Earth-Centred Model Even with their advanced knowledge of how to track the motion of the celestial bodies, ancient peoples still believed that the stars circle around Earth. This led to an Earth-centred or geocentric model of the universe. Aristotle saw that the stars’ patterns in the sky were unchanging, and placed the stars on the surface of an outer sphere that he termed the “firmament of fixed stars” or celestial sphere. He arranged the Sun, Moon, and five known planets on concentric spheres inside the celestial sphere. The Earth-centred model provided a means of predicting the dates and times when celestial bodies rose and set. Ultimately, it required up to 55 different spheres to account for the observed motions. Ptolemy 2 Space Exploration added “epicycles” to explain why the motions of three planets – Mars, Jupiter, and Saturn – appear to reverse or retrograde. The result was an even more complex Earth-centred model, although it did make sense. The Sun-Centred Model In the early 1500’s, Polish astronomer Nicholas Copernicus proposed a Sun-centred or heliocentric model to explain the view from Earth. He placed the Sun in the centre, with a rotating Earth revolving around it. German mathematician Johannes Kepler realized that the orbits of the planets are ellipses, not circles. Cosmological Events A. Solstice - marks the longest period of daylight or shortest period of daylight in the year. B. Equinox - represents days of equal length. C. Seasons and the Earth’s tilt Summer: tilts toward Earth Winter: tilts away from Earth When Earth rotates once, we call it a day. When Earth revolves around the Sun once, we call it a year. Acting together, these two movements create variations in temperature, weather, and in the seasons. The temperature difference between summer and winter is due to the angle of the Earth on its axis. During summer in Canada, the radiation from the Sun is more concentrated. The same amount of energy radiates from the Sun in winter, but it is spread across a larger area resulting in less heating. Note: The angle of the axis has been exaggerated in the diagram to make the difference in heat energy more visible. Universal Gravitation In the early 17th century, Johannes Kepler described the shape of the planets’ orbits around the Sun as an ellipse. An ellipse has two foci, with the Sun being located at one. This means that Earth can be different distances from the Sun. Like a ball that gains speed when it falls to the ground, Earth is fastest when it is closest to the Sun. 3 Space Exploration Eighty years later, Isaac Newton stated the law of Universal Gravitation. This law provided an explanation for the planets’ elliptical orbits. There is a gravitational force, or pull, between all objects. If there is no force acting on an object, it will move in a straight line at a constant speed. This means the planets, which are always moving, would fly off through space in a straight line. The force of gravity pulls them in toward the Sun, which balances their tendency to move in a straight line. The result is an elliptical orbit for each planet. Assignment 1. What is a frame of reference? 2. Why did ancient peoples think Earth was at the center of the universe? 3. What is an astrolabe and what function does it perform? 4. You want to measure the coordinates of a celestial object. The first angle you measure is clockwise from the north. What is the name for this angle? Next, you measure the celestial object’s angle above the horizon. What is this called? 5. Complete the statements: Azimuth readings go from 0° to ____°. Altitude readings go from 0° to ____°. 6. Use the diagram to the right to measure the altitude of stars A – D. A = ____° C = ____° B = ____° D = ____° 7. How does the heliocentric model differ from the geocentric model? 8. A friend tells you that it is cold in winter because Earth is farther from the Sun. Correct this statement. 9. What word is used to describe when the length of day equals the length of night? When do these occur? 10. Why is the northern hemisphere warm during summer and cold during winter? 11. Describe how planets stay in stable orbits around the Sun. 4 Space Exploration 2. Stronger Eyes and Better Numbers At one time, people were limited to using only their eyes to view the stars. The invention of the telescope has resulted in a big leap forward. Optical Telescopes A telescope is used to magnify objects at great distances. A simple telescope magnifies using 1. an objective lens: large one at the front of the telescope, 2. and an ocular lens: the eyepiece through which you view the magnified object. Refracting telescopes have a lens for their objectives and reflecting telescopes have objective mirrors. Refractors give better images than equal-size reflectors, but reflectors can be made much larger. New designs have elements of both types of telescope. Refracting telescopes were the first to be designed. They are smaller than reflecting telescopes, because their size becomes a problem. Any lens diameter greater than 1 m causes the glass in the lens to warp under its own weight. Imagine trying to learn the details of the moon by looking through the bottom of a pop bottle! Galileo’s Approach to Inquiry Galileo Galilei, an Italian astronomer, did not invent the telescope, but improved it and trained it on the sky at the end of the 17th century. Many scientists did not test their theories and models by observation. Galileo insisted that the adequacy of models should be assessed with observations. His observations revealed details of the celestial bodies that required new explanations: 1. The Moon’s surface has blemishes, which have shadows that lengthen and shorten with the Sun’s angle on them. Conclusion: 2. The Sun has spots on it that move across the surface of the period of a month before disappearing and reappearing again on the other edge. Conclusion: 3. Jupiter is accompanied by four small “stars” that move back and forth across it. Conclusion: 4. The planets appear to be disk-shaped, and some detail can be observed. The stars, however, appear to be pinpoint in appearance and cannot be further defined even with a telescope. Conclusion: 5 Space Exploration Overall, Galileo’s observations support Copernicus’s Sun-centred model and not Ptolemy’s Earth-centred model. Resolving Power To build a more powerful telescope, you need to increase its resolving power. This is the fineness of detail the telescope can produce of the object in view. It depends on the diameter of the objective lens. A telescope with a small diameter objective lens can magnify as much as you want, but you see only a larger image with the same detail. State the relationship between the width of the objective lens and the fineness of detail: Interferometry: Combining Telescopes for Greater Power The resolution of the images seen with optical telescopes can be further improved when two or more telescopes are used together in a technique called interferometry. On top of Mauna Kea, Keck I and Keck II are located 85 m apart from each other. When working together, they can detect objects in space with better clarity and at greater distances than any other current Earth-based observatories can. The Very Large Telescope located high in the Andean Mountains in Chile is four separate telescopes being used together. The Hubble Space Telescope Although remote mountains make excellent sites for building and operating telescopes away from light pollution and air pollution, astronomers are still at the mercy of the weather. Clouds, humidity (moisture in the air), and even high winds can interfere with star-gazing. The Hubble Space Telescope solves these problems by orbiting about 600 km above Earth. It takes about 95 min to orbit Earth. A reflecting telescope, it uses mirrors to focus light from extremely distant objects. It is modular in design, which allows shuttle mission astronauts to replace faulty or out-of-date instruments without having to interrupt its other operations. The telescope works 24 h a day, and is controlled from Earth. It observes, and sends data to Earth, but also uses time to turn to focus on a new object of interest or switch data transmission modes. Assignment 1. Why is there a need for telescopes? 2. Describe one pro about each type of optical telescope. 3. Jupiter’s moons (or “stars”) rotating around Jupiter contradicts the geocentric model. Explain why. 4. What observation led Galileo to the conclusion that the Sun rotates? 5. Large ground-based telescopes are built with the ability to move to oppose the movement of Earth. Why is this necessary? 6 Space Exploration 6. What happens to the detection capabilities of two reflecting telescopes working together? 7. Why is the Hubble Space Telescope a reflector and not a refractor? 8. Even though it has a smaller mirror than many Earth-based telescopes, the Hubble Space Telescope can see objects more than 50 times fainter than what Earth telescopes can see. Explain why that is. 3. The Spectroscope: New Meanings in Light Spectral Lines Isaac Newton passed a beam of sunlight through a prism to produce a rainbow of colours. This shows us that sunlight, which is white light, is made up of all colours. If you pass a beam of light through a narrow slit before sending it through a prism, the resulting spectrum shows much finer detail. A spectroscope is a device that produces this kind of focused spectrum. Joseph von Fraunhofer, a German optician, used a spectroscope (which had very fine prisms) to observe the Sun’s spectrum. He noticed hundreds of dark lines in the Sun’s spectrum called spectral lines. Spectroscopy: The Science of Colour The significance of spectral lines was discovered about 50 years after Fraunhofer’s discoveries. Chemists knew that the heated vapours of different elements give off different colours when heated to incandescence (heated until glowing). Examining this light through a spectroscope, Gustav Kirchoff, a German physicist, and Robert Bunsen, a German chemist, discovered that not all of the colours of the rainbow were present. Instead, they observed… Each element has a unique and particular set of spectral lines. Each spectrum can be used to identify an element. For example, if a sample is tested and has the lines below, you can conclude that the sample contains hydrogen. Hydrogen: Diffraction Gratings Like waves in a pool, the Sun’s light energy ripples out through space. Some of those light waves come to Earth. Some spectroscopes use prisms to split the light into a spectrum, but a diffraction grating can also split the light. It is made of thousands of closely spaced slits. When light passes through very small openings that are close together, a spectrum is produced. This happens because light waves bend around corners (they diffract) and then pass through each other causing interference (they cancel each other out, or reinforce each other – think about double-bouncing on a trampoline). The spectrum produced by a diffraction grating has much better detail in it than a spectrum from a prism. Modern spectroscopes use diffraction gratings instead of prisms to split the light into spectra. 7 Space Exploration Spectroscopy for Astronomers If white light is passed through a cooler substance, the spectrum observed is a continuous spectrum with dark gaps between colours. This is called an absorption or dark line spectrum. If the dark lines’ placement in the solar spectrum matches the bright lines produced by various elements, then those elements are present in the sample. Astronomers use this spectral analysis method to learn about distant stars, but the stars are much dimmer than the Sun, and astronomers can’t identify the hundreds of lines in their spectra. Any lines that can be observed are used to make inferences about the composition of the stars. Assignment: Long-Distance Chemistry: Using Spectral Analysis to Identify Star Composition The Doppler Effect: Determining a Star’s Direction of Motion Spectroscopes can also tell us how fast a celestial body, such as a star, is moving toward or away from us. You have probably noticed that the siren on an ambulance or fire truck sounds different as the vehicle approaches, passes, and then moves away from you. The change in the siren’s pitch is called the Doppler effect, and is caused by the change in the sound’s wavelength. This results in a shorter wavelength and a higher pitch. Behind the vehicle, the sound waves stretch out, creating a longer wavelength and lower pitch. Sound waves have equal wavelengths. Sound waves are shorter on the right (approaching) side and longer on the left (going away) side. No shifting Red shift (longer) vs. blue shift (shorter) 8 Space Exploration  Light, like sound, travels in waves. The Doppler effect can be used to measure the speed and direction of light-emitting objects such as stars. While the waves coming from emergency vehicles differ in sound, the light coming from stars differs in colour. Look at the spectral diagrams below. The same set of four lines is in each. Which represents the a) stationary star, b) star moving away (red shifting), and c) star moving toward (blue shifting)? Assignment 1. Describe how a spectroscope is used to find out what elements are present in the Sun’s atmosphere. 2. If a star’s light is “red shifted,” what can astronomers conclude about that star? 3. Think Critically. What should the spectrum of the moon look like? 4. The diagrams show models of two different light waves. One represents blue light, the other red light. Label the diagrams with the corresponding colour of light. 5. Look at the spectral diagrams. a. What can astronomers say about the composition of the stars producing these spectra? Label their compositions to the right of each star. b. What colour does each star appear? violet red violet red 9 Space Exploration 4. Bigger and Smarter Telescopes The reception of telephone calls in the early 20th century was often poor. They were transmitted by radio waves, and people had to shout over the hiss and noise on the line. In 1932, Karl Jansky, working for Bell Telephone Laboratories, was given the task of tracking down this radio interference. He built a radio antenna and discovered that interference rose and set with the Sun, planets, and stars. He concluded: This led to the use of radio telescopes to study radio objects in space. Seeing Beyond the Visible Optical telescopes give us information based on visible light. However, objects in space, such as stars and galaxies, also emit electromagnetic energy in the form of radio waves, infrared (heat) waves, and X-rays. This energy travels at the speed of light, 300 000 km/s, but has different wavelengths (λ) and frequencies (f) from those of light. Use the diagram on page 8 to compare: Wave λ f As λ ↓ the frequency _____. Radio As λ ↑ the frequency _____. Infrared X-rays Studying radio waves emitted by objects in space gives astronomers data that are not available from the visible spectrum. Radio telescopes have several advantages over optical telescopes: They are not affected by weather. Signals can be detected during the day and at night. They are not distorted by clouds, pollution, or the atmosphere as are light waves. They can detect information from regions of the universe that appear empty. e.g. neutral hydrogen does not emit light, but does emit a specific wavelength of energy. Mapping these energies, scientists have learned that our Milky Way galaxy is a spiral. Recall from our section about optical telescopes that smaller wavelengths have better resolving power. Objects in space produce very long radio waves, so the resolving power of radio telescopes is poor. However, the radio waves penetrate dust clouds, giving astronomers information about the universe that can’t be learned with optical telescopes. The signals that are received are mapped through the use of sophisticated electronics and computers. The pictures are coloured in by the computers, with low intensity signals being coloured purple or blue, and high intensities being coloured green, yellow, red to white. Radio telescopes are a metal-mesh curved dish with a receiver in the middle. The curved portion intercepts and focusses radio waves before transmitting them to the receiver as an electrical signal. The wavelength of light is one factor for the resolving power of telescopes – the smaller the wavelength, the better the resolving power. Because the wavelengths of radio waves are so large, the antenna of a radio telescope must be large to collect sufficient information to be useful. 10 Space Exploration  11 Space Exploration Radio Interferometry As with optical telescopes, several small radio telescopes can be arranged into groups (called arrays) to achieve greater resolving power than one large radio telescope can achieve. The greater the separation between the telescopes, the more detail astronomers can measure. The Very Large Array in Socorro, New Mexico, uses twenty-seven 25 m radio telescopes arranged in a Y pattern covering a distance of 61 km. The resolving capability of this array would be similar to that of a telescope with a diameter of 27 km. Radio astronomers can connect their telescopes without wires, called very long baseline interferometry (VLBI). Now radio telescopes from anywhere around the world can be connected and signals can be combined. Assignment: 1. How does the frequency and wavelength of radio waves compare to that of visible light? 2. How does a radio telescope differ in structure from optical telescopes? 3. Why are radio telescopes built so much larger than optical telescopes? 4. What is the purpose of creating arrays of radio telescopes? 5. If you wanted to build a radio telescope, would you build it in a country with lots of rain, sunshine, or both? Would either type of location affect the telescope’s ability to make accurate observations? Explain your answer. 5. Distance to the Stars By using a distance you know, you can indirectly measure the distance to a star in a process called triangulation. It is also called the parallax technique. You need to: 1. Create a baseline. The distant object will be viewed from each end of the baseline. Mark off a long, straight line. 2. Measure the angles to the object at each end of the baseline. 3. Make a scale drawing of the triangle that is formed. Draw the baseline and the angles that are formed at each end. Extend the sides of the triangle until they cross at the location of the object. 4. Measure the shortest distance (the perpendicular line) to the baseline. This is the distance of the object. When using triangulation, the longer the baseline, the more accurate the results. 12 Space Exploration Assignment: Using Triangulation to Measure an Unknown Distance Triangulation of a Star Watch This: watch https://youtu.be/iwlMmJs1f5o Parallax is used to determine distances to nearby stars. To create the longest baseline possible without leaving Earth, angles are measured when the Earth is farthest from the Sun (with Earth’s elliptical orbit, measurements are taken in January and June). The stars behind the one being measured appear to have changed in position, which is called parallax. This helps astronomers measure the parallax angle; if the lines are drawn six months apart, the parallax angle is half the angle created by the two lines with the nearby star being the vertex. The farther a star is from Earth, the smaller the parallax angle. Only 10,000 stars could be measured using parallax, and all those stars were within 126 light-years (see below for more information about astronomical distances). The Hipparcos (an acronym for HIgh Precision PArallax COllection Satellite) satellite changed this because its baseline of observation was longer. Its range for triangulation was 1600 light-years, resulting in nearly 120,000 stars to be mapped. Hipparcos was deactivated in 1993. Measuring Astronomical Distances The universe is so large that distance must be measured in different units – astronomical units (AU) and light-years. One AU is the distance from Earth to the Sun (1 AU = 1.5 x 108 km or 150 million km). The closest star to Earth, Proxima Centauri, is more than 272,000 AU from Earth. Astronomical distances are so much larger than our solar system, so astronomers created the light-year. It is the distance that light travels in one year, a distance equal to about 63,240 AU. e.g. How far is Proxima Centauri from Earth in light years? Assignment: 1. How is parallax used to measure distances in space? 2. When using the triangulation technique, why is it important to measure the baseline accurately? 3. How far away is the tree in the picture to the right? Note: Do not change the angle of the lines to aim at the tree in the picture. 4. When they are farthest apart, 7.5 billion km separate Earth and Pluto. a. State this measurement in scientific notation. b. Convert this distance to astronomical units. c. Convert this distance to light-years. 13 Space Exploration 6. Above the Atmosphere and Under Control Rockets – Getting Up There There are three basic parts to a rocket: 1. Machinery is everything from the rocket itself to engines, storage tanks, and the fins on the outside that help guide the rocket during its flight. 2. The fuel can be any number of materials, including liquid oxygen, gasoline, and liquid hydrogen. The mixture is ignited in a combustion chamber, causing the gases to escape as exhaust out of the nozzle. 3. The payload refers to the materials needed for the flight, including crew cabins, food, water, air, and people. The science of rocketry relies on a basic physics principle: All fuels create exhaust, which comes out the end of the rocket. The speed of the exhaust leaving the rocket is called the exhaust velocity, and it determines the range of the rocket. The gravitational exhaust velocity (28,000 km/h) has to be achieved for a rocket to venture into space. Staged rockets will travel faster and higher than complete rockets. A stage is a section of a rocket that drops off once its fuel is used up. Technologies for Space Exploration Rockets used today can enter into Earth’s orbit, but we don’t have powerful enough rockets to send heavy spacecraft on long journeys throughout the solar system. Scientists have developed a technique called gravitational assist. It is a method of acceleration which enables a spacecraft to gain extra speed by using the gravity of a planet to slingshot it in a new direction. Large telescopes use charge coupled devices (CCDs) instead of photographic plates to record images. These digital files can be processed with computer software. The Hubble Space Telescope has been orbiting Earth’s atmosphere since 1990. Artificial satellites are used for communications, observation and monitoring, navigation, and mapping. They are often powered with solar panels. Observation satellites are used for forecasting weather, carrying out research, and helping ships, aircraft, and other vehicles determine their exact location to Earth. Radio and television satellites are usually placed in geosynchronous orbit, which means they move in the same direction as Earth rotates. They are about 36,000 km above Earth and directly over the equator. They take 24 h to orbit Earth once, and appear to be motionless. Radio and television satellites are often placed in geosynchronous orbit so that the signal can be useful for people in one location, e.g. a television satellite for people living 14 Space Exploration in Canada. Observation satellites are placed in Low Earth orbit, about 200-800 km above Earth. They complete one orbit of Earth in about 1.5 h. GPS or global positioning systems use satellite technology to find out where you are on Earth. GPS (also called NAVSTAR for navigation satellite tracking and ranging) satellites aren’t as high as geosynchronous satellites. They send out radio signals announcing their exact position and time. A device with GPS detects radio signals and measures the distance to each satellite by comparing how long the signals take to receive. Your device calculates your location on Earth, using the triangulation method. What happens to old space junk? About 95% of all objects in the diagram to the right are orbital debris, not functional satellites. As satellites get old, engineers will use its last bit of fuel to slow it down so it will fall out of orbit and burn up in the atmosphere. What about objects that are too large to burn up completely? Operators can plan to have remaining debris fall into a remote location. This place, nicknamed Spacecraft Cemetery, is in the South Pacific Ocean. Farther satellites are instead sent even farther away into a graveyard orbit in space. There is so much space junk that one tiny collision could trigger a big chain reaction, a possibility called the “Kessler Effect.” To prevent a disaster like this from happening, anyone launching anything into orbit must now have a plan for the end of the device’s life. Watch how space agencies are dealing with space junk: https://youtu.be/SLEzsr46Hbk Five Canadian Contributions 1. Astronauts – Chris Hadfield (his many musical moments in space can be found on YouTube), Roberta Bondar, and more! 2. Black holes – University of Toronto researchers first found evidence in 1972. 3. Crater names on Mars – at least 25 are named after Canadian towns or cities. 4. The Canadarm – A remote-controlled robotic arm that was developed by Canadians. It helped capture and deploy satellites, dock space shuttles and even build the International Space Station. Watch and learn: https://youtu.be/cRt8cH1iMp4 5. Space farming – The University of Guelph leads the world in research for building greenhouses in space using hydroponics, or growing plants without soil. 15 Space Exploration The Future of Space Travel 1. Ion drives – Xenon gas is electrically charged, accelerated, then emitted as exhaust. Thrust generated by an ion drive is 10,000 times weaker than today’s chemically fueled rockets, but the force generated lasts a very long time and uses very little energy. In space, a little amount of force goes a long way. Ion drives are useful when traveling great distances in space. They are used in over 100 geosynchronous Earth orbit satellites, as well as the Dawn spacecraft which is studying Vesta and Ceres. 2. Solar sails – The Sun emits electromagnetic energy in the form of photons, which strike and propel the carbon fiber solar sails. The momentum from the photons is transferred to the sails, propelling them up to five times faster than current space crafts. The light sails do not require a lot of force to be set in motion. See what Bill Nye has to say: https://youtu.be/ORQNgKnKVvM 3. The International Space Station (ISS) – Currently orbiting the Earth at an altitude of 350 km. It is a joint project between sixteen nations, including the USA, Canada, Japan, Russia, and Brazil, as well as eleven European nations. The space station is in low Earth orbit, and can be seen from Earth with the naked eye. It orbits at an altitude of approximately 350 km above the surface of the Earth, travelling at a speed of 7.66 km/s, completing one orbit around Earth every 92 minutes! Assignment 1. Describe the three basic parts of a rocket. Draw and label a sketch showing the parts. 2. What is the benefit of having a staged rocket? 3. Name two alternatives to rocket engines that scientists are studying as a means of propelling spacecraft on long journeys. 4. Explain what would happen if a rocket’s payload were greater than the allowed percentage. 5. What is the main attraction for using an ion drive for powering spacecraft? 6. Besides saving in fuel costs, what is the other main advantage to using a solar sail? 7. Space probes are often sent into space to collect information for scientists to study; they do not have astronauts. Name and describe two other objects that are sent into space. 8. How do left-over materials in space pose a threat to people on the ground? 16 Space Exploration 7. People in Space Space begins approximately 100 km above Earth, but Earth’s gases (considered its atmosphere) may extend up to 600,000 km above Earth. Outside of the atmosphere lies the cold vacuum of space. It is an environment that is hostile to humans in many ways. NASA is close to having the technology to send humans to Mars and back, however, a mission like this would take two to three years. Hazards of Living in Space 1. Environmental Hazards – Since space is a vacuum, there is no oxygen or water. Other hazards include the damaging effects of cosmic rays and solar radiation, being hit by meteoroids, extremely cold temperatures in the shadows or extremely high temperatures in the full sun (due to no atmosphere). The air pressure that helps regulate our heartbeats is also missing. 2. Psychological Challenges to Confined Living: Astronauts maintain close, confined quarters for long periods of time, up to two years. 3. Effects of Microgravity on the Body – Astronauts on the ISS work in a microgravity environment. This means the gravitational forces on the body are greatly reduced. In space, astronauts are nearly weightless, which can confuse the body’s senses. Many astronauts develop space sickness, which is like motion sickness. They feel nauseated and dizzy and have headaches. They may vomit, which can be very dangerous if they are wearing a spacesuit. Space sickness goes away as the astronaut adjusts to microgravity, but they may need to wear a medication patch on their skin to reduce the effects while on space walks. With no gravity pulling down on you, the body undergoes many changes. Fluids move from the legs to the upper body and head, which can block a person’s sinuses as though they have a cold. The face and neck can also look puffy. Bones have much less pressure on them, so they expand, and the heart does not have to pump as hard to circulate blood. Muscles do not get used as much and weaken, so astronauts exercise to keep their muscles in good condition. Even visual depth perception is affected. When astronauts return to Earth, it takes several weeks for the body to return to normal. Storage Space and Recycling in Space Because there is so little room for storage, materials taken onto the International Space Station must be recyclable or reusable. This includes water. The ISS recycles almost 100% of its water, including waste water, water for hygiene, and moisture in the air. The water is purified over and over on long space flights using fuel cells to produce drinkable water as well as electrical power. Piloted spacecraft carry oxygen in on-board tanks in liquid form. Gaseous oxygen takes 800 times more space than liquid oxygen. Carbon dioxide must also be removed from the air; in some space stations, oxygen is produced from carbon dioxide or water. The hydrogen release from the water molecules is vented into space. The oxygen produced can supply most of the crew’s needs. 17 Space Exploration Space Suits The first space suits were worn on the Mercury spacecraft in 1962. They were modeled after suits worn by fighter jet pilots who flew at high altitudes. The suit was not pressurized, but was worn just in case the spacecraft lost cabin pressure. Shown to the left is Astronaut John Hershel Glenn in his Mercury spacesuit. Credit: NASA Once it was determined that people could safely travel into space, the suit needed to change to allow astronauts to leave the spacecraft. Neil Armstrong and Buzz Aldrin became the first to walk on the moon on July 20, 1969. Their suits needed to withstand the vacuum of space, extreme temperatures, and be flexible to allow movement such as walking and grasping objects. The fabric of their suit also had to be tough to withstand piercing by moon rocks or micrometeoroids, which are small bits of space dust and junk. Travel into outer space has required the development of the current suit, the EMU (Extravehicular Mobility Unit). It is sturdy enough to withstand the harsh environment of space (such as micrometeoroids and the harsh radiation of the Sun), but is also more flexible. When the astronaut wears it, they must be able to walk, bend over, grasp a wrench, or twist a bolt. These suits have their own supply of oxygen, as well as cooling and communication systems and a portable toilet! These space suits are custom-designed for the person who will wear them. Essentially, the space suit is a mini-Earth system that allows the wearer to work freely outside the craft. The Pros and Cons of Space Exploration Many people argue that there are so many problems on Earth that require solving, for example: countries should not be spending large amounts of money on space exploration. Others, however, argue that space is the “last great frontier,” and that discoveries in space could lead to improving life on Earth. Some forecasters predict that the population of Earth will stabilize in the next fifty years, while our demand for resources will continue to grow. Technology is allowing scientists to look beyond Earth and to space for them. It is being driven by economics: 18 Space Exploration  1. Space could be a source of resources such as solar energy, and mineral resources from rocks in the asteroid belt. 2. The cost of space travel could be cut by using material in space for the construction of space vehicles, supplies and fuel. For example, both hydrogen and oxygen can be easily processed from Moon rock, which then could be combined to form and supply water. Political, Ethical, And Environmental Issues Who owns the resources in space, and who has the right to use them will be up for debate if space development does continue? Political questions: Who owns space? Who has the right to use the resources in space? Who will determine how space is used? Ethical questions: Is it right to spend money on space exploration rather than on solving problems on Earth? Do we have a right to alter materials in space to meet our needs? How can we ensure that space resources will be used for the good of humans and not to further the interests of only one nation or group? Environmental questions: Who is responsible for protecting space environments from alteration? Who is responsible for cleaning up space junk, and who should pay for doing it? Assignment 1. What are three hazards of living in space? 2. Briefly describe how working on the International Space Station might affect a person psychologically. 3. What is the difference between gravity and microgravity? 4. Explain why a regular ball-point pen will not work in space. 5. What effect does living in space for extended periods of time have on a. bones? b. muscles? 6. List some characteristics or features that a space suit must possess in order to be functional for a particular astronaut. 7. Use examples to explain the value of recycling in space. 8. How is oxygen produced in space? 9. Why might asteroids be of interest in space exploration? 10. List three costs of space exploration, and three benefits. 19 Space Exploration 8. Up Close: Galaxies & Our Solar System To people of long ago, the bright band of stars, gas, and dust that was visible in the night sky looked like milk that had been spilled along a pathway. As a result, that galaxy that is home to our solar system was called the Milky Way Galaxy. All of the stars you can see at night and several hundred billion more are all bound together by gravity. The Milky Way, a spiral galaxy, is shaped like a flattened pinwheel, with arms spiralling out from the center. From the side, it looks like a CD with a marble in the middle sticking out evenly on either side. You can make a rough guess of the number of stars in our galaxy by dividing the Galaxy’s total mass by the mass of a typical star. Recently, astronomers have discovered that most of the mass of the Galaxy (and other galaxies) is not in the form of stars, gas, or dust. Instead, it is made of some other material, yet unknown, and is given the descriptive name “dark matter.” Dark matter does not produce any light, but it has gravity that can be measured. Scientists believe that dark matter also allows the stars in a galaxy to rotate at a constant speed. Analysis of the rotation of stars in galaxies has shown that for the most part, the stars all rotate at about the same speed, regardless of how far they are from the galactic center. This would not be possible without some form of matter existing between the stars. There are millions of galaxies, each with millions of stars. Most galaxies have common features as seen in the Sombrero Galaxy, a lenticular galaxy, that is pictured: 1. A bulge which is the round center of the galaxy. It contains billions of stars, as well as gases and dust. Here, the stars are quite old in comparison to the stars in the rest of the galaxy. 2. The disk, which surrounds the bulge, is the flattened portion of the galaxy and contains mostly younger stars. A disk is not present in an elliptical galaxy. 3. The halo is the ring of gases and stars that extends beyond the galaxy. Halos are easier to see in spiral galaxies than in other galaxies. In elliptical galaxies, it can be hard to see where the bulge ends and the halo begins. Halos contain dust, gas, dark matter, and may also contain globular clusters. 4. Spiral arms are only present in spiral galaxies. They are curving arms that spread out from the bulge, giving the spiral galaxy its pinwheel appearance. The spiral arms contain mainly younger stars, gas, and dust. 20 Space Exploration Galaxies take these shapes: 1. Spiral: flattened disks with a spiral pattern in the disk. Most galaxies are spiral. Older stars are near the center of the bulge. Star formation occurs in the gases within the disk and spirals. 2. Elliptical: Smooth with a stretched circle or oval shape. It does not have a disk. They contain very little dust or gas, and contain older, smaller stars with little to no new star formation. 3. Irregular: no definite structure; the stars are bunched up but the patches are randomly distributed throughout the galaxy. They contain lots of gas and dust, and active star formation; many of the stars in irregular galaxies are quite young. Astronomers believe they were other galaxies that lost their shape due to gravity acting on them during collisions or near collisions with other galaxies. 4. Lenticular: has a bulge, disk, and halo, but does not contain spiral arms. There is little gas, meaning little star formation occurs, and the existing stars are quite old. Label the shape of these galaxies: _________________ _________________ _________________ Our Solar Neighbourhood The formation of our solar system is based on the protoplanet hypothesis or nebular theory, which follows three steps: 1. A cloud of gas and dust in space begins swirling. 2. Most of the material (more than 90%) accumulates in the center, forming the sun. 3. The remaining material accumulates in smaller clumps circling the center. These form planets. 21 Space Exploration Take notes on the eight planets using the NASA website: https://solarsystem.nasa.gov/planets/overview/ Diameter Planet & Average Date (km) & Size # of Length of Planet Surface Composition Discovered Compared Moons Day & Year Type Temp to Earth Mercury Day: Year: Venus Day: Year: Earth Day: Year: Mars Day: Year: Jupiter Day: Year: Saturn Day: Year: Uranus Day: Year: Neptune Day: Year: 22 Space Exploration The Sun The Sun is at the center of our solar system. Our Sun is one million times bigger than Earth and has a diameter 110 times wider than Earth. The surface of the Sun, which is always bubbling and boiling, is about 5500°C, while the core is close to 15 million degrees Celsius. The Sun contains mostly hydrogen and helium, which is packed very densely at its core. The Sun emits charged particles in all directions. This solar wind bombards the Earth at 400 km/s, but the Earth’s magnetic field protects us. Asteroids Between the orbits of Mars and Jupiter lies a narrow belt of small asteroids ranging in size from a few meters to several hundred kilometers across. The largest known asteroid, Ceres, is over 1000 km wide. Scientists don’t know where the asteroids came from. Beyond Pluto, a group of objects orbit in the Kuiper belt. Asteroids, comets, dwarf planets, and other small solar system bodies are in this region. Comets Often described as “dirty snowballs,” comets are made up of dust and ice that travel through space. When they get close to the Sun, they heat up and emit light. Gases are released, and get pushed away from the comet by the solar wind. These gases form long tails that can be millions of kilometers long. Usually comets spend their time orbiting the outer edges of our solar system, and are not visible from Earth. The path of a comet is elliptical, enabling astronomers to predict when the comet will pass by Earth again. Halley’s comet has an average 76-year orbit, and was last observed in 1986. Shortly afterward, observers saw it brighten unexpectedly, which might mean it collided with something. We will have to see what happened when it returns again in 2062. 23 Space Exploration Meteoroids, Meteors, and Meteorites Meteoroids are small pieces of rock (can be as small as a grain of sand or as large as a car) flying through space with no particular path. We are usually aware of them once they enter our atmosphere and heat up due to friction, giving off light. Once in our atmosphere, they are called meteors. They are known to us as “shooting stars” when we see them streaking across the night sky. A meteor becomes known as a meteorite if it lasts long enough to impact the Earth’s surface. Most meteors burn up in the atmosphere. Tracking Objects in the Solar System You learned previously that the paths of planets have elliptical paths. This can be demonstrated with a string and two thumbtacks, as shown to the right. With this information, astronomers and scientists can trace and predict where bodies in space are, have been and will be in the future. Aside from Pluto, all other planets orbit the Sun in roughly the same plane. Pluto, however, has an orbit that is raised 17.2° from the plane of the other planets. Additionally, Pluto’s orbit is more elliptical than that of the other planets. As a result, every 248 Earth years, Pluto’s orbit slips inside Neptune’s orbit for a period of twenty years. The understanding of orbits has led to the discovery of many different comets. NASA tracks asteroids, comets, and meteors that have been discovered by observatories and amateur astronomers. Assignment 1. What is the solar wind? 2. How does the Sun release energy? 3. Where are the terrestrial planets located compared to the gas and ice giants? 4. Explain the main ways in which the inner planets differ from the outer planets in our solar system. 5. Describe what an asteroid is. 6. Why are comets sometimes referred to as “dirty snowballs”? Why are their tails visible? 7. What is the name for a meteoroid that survives its journey through our atmosphere and hits Earth? 8. Describe in your own words how the solar system formed. 9. For about 20 years, from 1979 to 1999, Pluto was closer to the Sun than Neptune was. Explain why this was possible. 10. Suppose a gaseous planet half the size of Saturn was discovered. Where in the solar system do you think it would be located? Give a reason for your answer. 11. Most of the worlds in the solar system that have solid surfaces show evidence of heavy cratering. Suggest a reason for this. 24 Space Exploration 9. Beyond the Milky Way Astronomers estimate the age of the universe to be about 13.8 billion years. They calculate this age by measuring the distances and radial velocities of other galaxies, most of which are flying away from our own galaxy. What Is A Star? A star is a hot, glowing ball of gas (mainly hydrogen) that gives off tremendous light energy. There are billions of billions of stars in the universe. They vary in temperature, brightness, size, and colour, as shown by the Hertzsprung-Russell diagram to the right. 90% of all stars fit into this grouping. Our Sun belongs in the middle of the main sequence grouping. Colour the stars. The giants are yellow and the main sequence stars are in rainbow order. Stars vary greatly in their characteristics. Betelgeuse is 670x larger than our Sun, but only 1/10-millionth as dense. Our Sun is a very average star. If it was 1 m wide, the largest known star would be 2300 m (or 2.3 km) wide! The Birth of a Star Just like living organisms, stars have a life cycle: they are born, live, and die. The life cycles of massive stars differ from those of Sun-like stars, as shown in the diagram. A nebula is a region of gas and dust where stars form. Each is composed of about 75% hydrogen and 23% helium. The other 2% is oxygen, nitrogen, carbon, and silicate dust. Some of this interstellar matter came from exploding stars. 25 Space Exploration The attraction of gravity acting between atoms of gas and grains of dust causes a small area of the nebula to start collapsing into a smaller, rotating cloud of gas and dust. As more material is drawn into the spinning ball, the mass at its core increases and the temperature climbs. If the core gets hot enough, it will start to glow forming a protostar, the first stage in a star’s formation. The interior of the protostar gets hotter and hotter, reaching 10 million degrees Celsius, and hydrogen starts to change to helium. This process is known as fusion, and it releases great quantities of energy and radiation. The star has been born. A star’s mass determines whether it is a Sun-like or a massive star. Both spend most of their time in the main sequence with fusion occurring in their cores. The outward pressure generated by fusion is counteracted by gravity, and the star is stable in this phase. All stars remain in this state for millions to billions of years. As the nuclear fuel of the star runs out, so does the energy required to keep the gases together and the star expands dramatically. A Sun-like star becomes a red giant and a massive star becomes a red supergiant. For us, our Sun will become a red giant in about 5 billion years, expanding to have a diameter beyond the current orbit of Mars. Fusion stops in Sun-like stars because the star is no longer hot enough to keep the reaction going. The star contracts to 1/10 of the original size, gradually becoming a white dwarf no larger than Earth. Eventually, the star will cool until it no longer emits light, becoming a black dwarf. It takes so long for this cooling process to occur that there are no known black dwarfs in our universe. Fusion stops in massive stars because the star runs out of fuel. The residual star is so dense and gravitationally unstable that a supernova or solar explosion may result. If the star is not completely destroyed by the explosion, the collapsed core is left as a neutron star or a black hole. A neutron star is a rapidly spinning object that is only about 30 km in diameter; it is too small to form a black hole. A black hole, shown to the right, is a highly dense remnant of a star in which gravity is so strong that even light cannot escape! Although they are invisible to telescopes, material close to a black hole emits a tremendous amount of light so we can see them indirectly. 26 Space Exploration Assignment 1. What is the main chemical element in a star? 2. What is the connection between a supernova and a black hole? 3. What is the term used to refer to a group of millions of stars? 4. Explain the Hertzsprung-Russell diagram in your own words. 5. Why are nebulae sometimes referred to as “stellar nurseries”? 6. Create a word sequence that correctly summarizes the life cycle of massive stars. Use the words: red supergiant, nebula, supernova, massive star, neutron star. Connect each word with an arrow: 🡪 7. Considering the number of stars in space, why don’t astronomers see greater numbers of dwarf stars? 8. Imagine two stars in a galaxy. Both are at the end of their life spans. One star ends up as a white dwarf, the other ends up as a black hole. Describe the conditions that led to these stars having different outcomes. 9. The light we see from the planets in our solar system is just the light reflected from the Sun. Why do planets appear brighter than the vast majority of stars we see? 27 Space Exploration