Unit 5 - Space Exploration

Lesson 1 - For Our Eyes Only

A frame of reference is a set of axes of any kind that is used to describe the positions or motion of things. For example, the equator and the prime meridian are the axes for the frame of reference used to locate positions on Earth (latitude and longitude).

Ancient peoples watched the motions of celestial bodies (Sun, Moon, stars, and planets). They noticed that stars make unchanging patterns in the sky. These patterns looked like objects which people grouped and named. These groupings are called constellations. Ex. Orion, Great Bear - Ursa Major.

  • On each successive day, a given star rises and sets four minutes earlier than the day before. This means that over time, different stars are in the night sky. Since each month has its own set of stars in the night sky, people developed the ability to predict the changing of the seasons – helped in the creation of calendars.

Sky Co-ordinates

  • A celestial bodies’ location in the sky was measured by using two co-ordinates measured in degrees. The first angle is measured clockwise from north. This is called the azimuth. Next measures the angle above the horizon. This is called the altitude.
  • Angles used to specify the co-ordinates of a celestial body are called altitude-azimuth co-ordinates.

(p. 359)

  • The co-ordinates for each body change depending on the time of the reading.
  • Our ability to measure the positions of bodies in the sky has always depended upon technological devices. An astrolabe is a device used to measure the altitude. A compass is used to measure an object’s azimuth.
  • To track the actual motion of each celestial body we use the stars as the frame of reference instead of Earth. This is because we are looking for motions in the sky that are different from the big motion caused by Earth’s rotation.

The Earth-Sun-Centered Models

  • Ancient peoples believed that the stars circled around Earth. This led to an Earth-centered or geocentric model of the universe, which lasted almost 2000 years. (Started by Greek philosopher Aristotle).
  • In the early 1500s, polish astronomer Nicholas Copernicus proposed that the Sun was fixed, and a rotating Earth revolved around it. This is known as the Sun-centered or heliocentric model of the universe.

Stronger Eyes and Better Numbers

  • A telescope is used to magnify objects at great distances. It was invented by Hans Lippershey (Dutch), in 1608. A simple telescope consists of an objective lens and an ocular lens.
  • An objective lens is the large one at the front of the telescope. The ocular lens is the eyepiece through which you look.
  • Later that century, Galileo Galilei, improved the telescope and used it to make celestial observations that required new explanations. Unlike scientists before him, Galileo insisted that any model of the universe should be backed up by actual and careful observations.
  • Resolving power is the fineness of detail the telescope can produce of the object in view. This depends on the diameter of the objective lens – the larger the diameter the greater or finer the detail.

Refractors and Reflectors

  • Many types of telescopes have been invented since Galileo’s time.
  • Refracting telescopes have a lens for their objectives and reflecting telescopes have a mirror (See Fig. 5.14 p. 370).

Lesson 2 – Johannes Kepler

  • In 1609, Johannes Kepler, showed that the planetary orbits were elliptical rather than circular. An ellipse is a figure that looks like a squashed circle.
  • By using a combination of mathematics and data gathered by astronomer Tycho Brahe over a period of 20 years of observations, Kepler also figured out the shape and scale of the entire known solar system.

Universal Gravitation

  • Newton stated the law of universal gravitation, which provided an explanation for the planets’ elliptical orbits.
  • According to Newton’s law there is a gravitational force of attraction between all masses in the universe. When no forces act on an object, it will move in a straight line at a constant speed.
  • The planets are always moving but the force of gravity of the Sun results in the elliptical path.

The Spectroscope: New Meanings in Light

  • Isaac Newton passed a beam of sunlight through a prism to produce a spectrum of colors. It showed that normal white light is made up of all colors (ROY G BIV).
  • 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.
  • Fraunhofer (1820s), a German optician, used a spectroscope to observe the Sun’s spectrum. He noticed hundreds of dark lines in the Sun’s spectrum (also called the solar spectrum). These dark lines are called spectral lines.

Spectroscopy: The Science of Color

  • Gustav Kirchoff and Robert Bunsen (German physicist and chemist) heated various chemicals to incandescence and examined their light through a spectroscope. They discovered that not all of the colors of the rainbow were present – each spectrum was a series of color lines with black spaces between them. Each spectrum was unique and could be used to identify the element.
  • Spectroscopy is the study of spectra. There are three types of spectra:
  • Continuous - rainbow
  • Emission or Bright line
  • Absorption or Dark line (see p. 377)

Diffraction Grating

  • A device made of thousands of closely spaced slits is called a diffraction grating. It produces a better spectrum than a prism.
  • Modern spectroscopes use diffraction gratings instead of prisms to split the light into spectra.
  • Astronomers use spectral analysis to identify the gases on the Sun (and to a lesser extent on stars because of distance).

The Doppler effect

  • You have probably noticed that the siren on an ambulance sounds different as the vehicle approaches, passes and then moves away from you. The siren’s change in pitch is called the Doppler effect and is caused by the change in the sound’s wavelength.
  • As the vehicle approaches you the wave gets compressed resulting in higher pitch and the wave gets stretched as it moves away resulting in lower pitch.
  • The Doppler effect can be used to measure the speed and direction of light-emitting objects such as stars. If the star is going away from you, its spectral lines will be red shifted – longer wavelength part (red end). If it’s moving toward the lines will be blue shifted.

Lesson 3 - Bigger and Smarter Telescopes

  • In 1773 Sir William Herschel, an English astronomer, built a large reflecting telescope. With this telescope, he discovered the planet Uranus.
  • Today, with the use of computers, it is possible to combine images from two or more telescopes.

Adaptive Optics

  • Stars twinkle because of the Earth’s motion and the bending (refraction) of light by the atmosphere. The technology that cancels out the twinkling effect is called adaptive optics.

Distance – Measuring with Triangulation

  • Triangulation is a method of measuring distance indirectly by creating an imaginary triangle between an observer and an object whose distance is to be estimated (See Fig.5.30&5.31 p.387&388).
  • Astronomers use triangulation to measure distances to celestial objects.
  • Astronomers use the diameter of Earth’s orbit as the baseline for triangulating on a nearby objects. The angle between the baseline and the star’s position is measured in January and July, for example.
  • The nearest star to Earth is Proxima Centauri and it is more than 272,000 astronomical units (AU) from the Sun. One astronomical unit is the distance from Earth to the Sun (150 million km).
  • Astronomers use light-years to measure interstellar distances. A light-year represents the distance that light travels in one year (about 63,240 AU). On this scale, Proxima Centauri is 4.28 light-years away.

What Channel Is That?

  • Light isn’t the only kind of radiation coming from the stars – light is just one form of electromagnetic radiation. The electromagnetic spectrum is made up of radio waves, microwaves, infrared radiation (heat), visible light, ultraviolet radiation, X-rays, and gamma rays. (See Fig. 5.33 p. 393).
  • Radio astronomy uses radio waves to study the composition of stars. The first radio telescope (antenna) was built in 1932 by Karl Jansky and later perfected by Reber (made a parabolic dish).
  • “Listening” to the stars through the radio telescope would be like tuning a radio between channels. Reber would hear hissing static. The hiss would become louder when he tuned in to an area in space that was giving off large amounts of radio waves – the bright radio objects. In our solar system the Sun is the brightest of all the radio objects, and Jupiter is the second brightest.
  • Radio astronomers wanted to identify their strong sources with objects they had seen with optical telescopes. This was impossible at first because the radio images had such low resolutions. As the radio telescope improved, astronomers could make these optical connections.
  • If two or more radio telescopes are connected together, their signals can be combined using a computer. It’s like seeing with many eyes instead of one. This method is called interferometry. The most accurate set of connected telescopes in the world is the Very Large Array (VLA) in New Mexico.
  • Today telescopes can be connected without wires. This is called very long baseline interferometry (VLBI). VLBI produces images 100 times as detailed as the largest optical telescopes.

Lesson 4 - Above the Atmosphere

  • The Earth’s atmosphere prevents astronomers from getting a clear view of the universe. Thus, astronomers are sending telescopes into space using rockets and computers.
  • A rocket is a tube that contains combustible materials in one end and a payload in the other end and moves by the action, reaction principle (Newton’s Third Law of Motion: For every action there is an equal and opposite reaction).
  • The fuel used in a rocket creates exhaust that comes out of the rocket. The speed at which it leaves is called the exhaust velocity. The greater the exhaust velocity the greater the rocket’s range.
  • To increase the velocity of the exhaust, liquid fuel is used instead of solid fuel, and the fuel is kept in several compartments. As the fuel is used up in that compartment, it is dropped off to make the rocket lighter – a staged rocket.
  • To send rockets throughout the universe, scientist use a technique called gravitational assist. Gravitational assist uses the gravity of a planet to change the speed and/or direction of a rocket. (Fig. 5.42 p. 402).

Clarifying Images

  • Today, large telescopes use charge-coupled devices (CCDs) instead of photographic plates to record images. These devices convert light signals into electric signals in digital format.
  • Then the images can be processed in many ways using computer software.

Satellites

  • Astronomers use artificial satellites, such as the Hubble space telescope, to look into space.
  • Some communications satellites are placed in low Earth orbit, while others are placed in geosynchronous orbit.
  • Low Earth orbit satellites are placed 200-800 km high above the ground. They circle the Earth faster than the Earth rotates.
  • Geosynchronous orbit satellites move in the same direction as Earth rotates. They are placed about 36,000 km above Earth, directly over the equator and appear motionless. Radio and TV satellites are usually placed in this type of orbit.
  • Observation satellites are used for forecasting weather, research, measure depth of snow, location of forest fires etc.
  • The science of taking measurements of Earth (and other planets) from space is known as remote sensing.
  • Global Positioning System (GPS) uses a fleet of GPS satellites above Earth and a small hand-held GPS unit on Earth. It can calculate your position on Earth to within 30 m (military units can be accurate to within a few centimeters).

Lesson 5 – The Solar System Up Close

  • Everything in the solar system is under the influence of the Sun’s gravity. The Sun is made up of mostly hydrogen and it is about 1.4 million km in diameter (110xEarth’s).

Moon and Planets

  • The Moon is the first place (and only) on which man has managed to land. On July 17, 1969 two Americans, Neil Armstrong and Edwin Aldrin, were the first to make it to the Moon.
  • There are nine planets in our solar system and no two are exactly the same. They differ in size, motion, composition, density, and temperature. However, some have few similar features.
  • The inner planets – Mercury, Venus, Earth, and Mars – are sometimes called the terrestrial planets, because of their rocky composition. The outer planets – Jupiter, Saturn, Uranus, and Neptune – are similar because of their gaseous composition.

Exploring the Outer Space

Two spacecrafts, Voyager 1 and Voyager 2, were designed by NASA and sent to the edge of the solar system with gravitational assists from the planets.

People in Space

  • The Soviet Union was the first to successfully orbit a satellite with no astronauts inside – Sputnik 1 (1957). On April 12, 1961, Cosmonaut Yuri Gagarin, was the first person in space aboard Vostok 1, which orbited the Earth once at 302 km above the surface.
  • The first American in space was Alan Shepard on May 5, 1961 (aboard Freedom 7). He flew a sub-orbital flight.
  • A sub-orbital trajectory is one in which the spacecraft is boosted above the atmosphere and then falls back to Earth without going into orbit.
  • In 1962, astronaut John Glenn was the first American to make a full orbital flight.

The Apollo Program

  • The Apollo Program was designed to send a three-person team to the Moon, land two of them, and bring everyone back safely.
  • The Apollo spacecraft consisted of an orbiter and a lander (the lunar module). In the summer of 1969, Apollo 11 carried the first humans to the Moon. Neil Armstrong was the first man to step onto the Moon’s surface, followed by Edwin Aldrin. Michael Collins manned the command module in lunar orbit.
  • Eventual Soviet-American co-operation resulted in joint missions – the Apollo/Soyuz test project was flown in 1975. It was the first international space mission.

The Space Shuttle

  • The first Shuttle, Columbia, flew its first mission in 1981. Seven months later it flew again. The Canadian-built space arm , Canadarm, was tested on this flight and has been part of all shuttles since.
  • Marc Garneau was the first Canadian aboard a space shuttle in 1984 (Challenger). Roberta Bondar became the second in 1992 aboard the Discovery.
  • In addition to launching and fixing satellites, the shuttles are being used to help build the International Space Station (ISS).
  • Canada developed a second generation of space robotics for the ISS, called the Canadian space station remote manipulator system (SSRMS) or “Canadarm2” (giant mechanical arm attached to the space station).
  • The ISS will provide laboratory for long-term research in various fields (biology, chemistry, physics, medicine). This research will be done in micro-gravity (zero gravity) environment.

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