GRADE 9 SCIENCE



GRADE 9 SCIENCE

SPACE EXPLORATION

FINAL EXAM PREPARATION

Name: ____________________________ Homeroom: ______

STUDY GUIDE

EARLY EXPLORATION OF THE SKY (Textbook pages 370-382)

Ancient Views

• People understand space based on their frame of reference. If the earth was all you knew as in ancient times, you would assume that it was at the center of the universe. Observation of things outside of our own planet, and eventually outside of our solar system and galaxy have allowed us to continually change our understanding of the universe because we have an ever-expanding frame of reference.

• Cultural viewpoints:

• First Nations thought Stone Ribs slept beneath the ground and held a pole

with a blanket full of holes on top of it.

▪ In ancient days, it was very important to be able to predict seasons based on motions in the sky for planting, harvesting and religious celebrations. To do this, they would track the solstices (seasons) and used this as their calendars. Examples of solstice trackers include Stonehenge, Medicine Circles, Pyramids, Mayan Temples.

• Solstices are the longest (first day of summer) and shortest (first day of winter) days of the year. The equinoxes are when day and night is exactly equal (first day of fall and spring).

• Geocentric – Aristotle said Earth was the centre of the solar system (universe).

• Heliocentric – Copernicus challenged Aristotle’s view and said the sun was at the centre and each planet revolves in an orbit around it. This was proven by Galileo using his telescope.

• Kepler – later discovered through mathematics that orbits were not perfect circles. They were slightly elliptical.

• Sundials -These are ancient devices for telling the time of day (length of shadow) as well as the time of year (position of shadow).

Space Exploration Leading Up to Modern Science

• Optical telescopes

• Although Galileo is usually credited with inventing the first telescope, he actually just improved on a design introduced by Lippershey.

• Telescopes became more and more refined. Galileo’s model was a refracting telescope. Later telescopes favoured reflecting which had a large mirror instead of a glass lens. This allowed images to be more magnified.

• Space travel

• The Chinese invented the first rocket as a weapon.

• The Greeks experimented with rocket engines when they made a clay pigeon that was propelled forward as hot steam shot out of the back.

• The Space Shuttle program was developed in the late 70’s and early 80’s. This reusable spacecraft made it more economic to go into space.

• In 2000, the first crew came on board the International Space Station, a permanent orbiting habitat and research station.

• Next step – settle on the moon and then off to Mars

WHAT IS IN SPACE? (Textbook pages 384-407, 446-454)

Stars and Star Groupings

• Stars are hot, glowing balls of hydrogen and helium gas that produce their own energy through nuclear fusion reactions in the core.

• Charged photon particles called solar winds blast out into space from stars.

• Star characteristics can vary greatly – in colour, size, temperature, brightness and even composition.

• A star’s colour is determined by its temperature. It follows the same pattern as light (red-orange-yellow-green-blue-violet) with red being the coolest and violet being the hottest. Our sun is a moderate temperature in the yellow/orange range.

• Stars vary in size from small dwarfs to huge supergiants. Our sun is in the middle – a main sequence star with medium size and medium temperature.

• Star Systems - our Solar System is a star system – a group of objects orbiting

onE or more central stars.

• Nebula - when a dying main sequence star explodes, it forms or adds to a nebula. These are collections of gas and dust and, eventually, they will be the birthplace of a new star or stars. Within a nebula, gravity between particles forms a rotating ball that acts like a snowball to collect more gas and dust. Core temperatures increase until the mass starts to glow (protostar stage). As it gets even bigger, hydrogen starts to fuse into helium producing nuclear energy. A star has been born.

• Galaxies - very large groupings of stars. There are billions of stars in galaxies and billions of galaxies in the universe. We live in the spiral Milky Way Galaxy.

• Constellations and Asterisms - small groups of stars are called constellations (or asterisms, locally). Ursa Major is a constellation known all over the world but we know part of it as the Big Dipper (asterism).

The entire bear is the constellation Ursa Major

Star Life Cycles

• Life cycle of stars differ depending on whether they are main sequence or massive stars. The diagram below shows how either star can be born from a nebula. The massive star simply collects more gas and dust than the main sequence star.

• The Hertzsprung-Russell (HR) Diagram compares brightness (luminosity) and temperature in an effort to group stars within distinct categories (spectral classes). The Red Giants and Supergiants are bright because they are so big, but they are cool (note temperature scale is backwards, going from hot at the left to cool at the right). White dwarfs are very hot but, because they are so small, they are not very bright. Our sun is a main-sequence star.

Spectral Analysis

• Isaac Newton first observed visible light’s spectra using a glass prism. As knowledge increased, scientists realized that the lines seen in the spectra represented elements in the periodic table. Each element has a unique “bar code” based on lines in the spectrum. Thus, astronomers can identify what kinds of elements are in stars from the lines they find in the star's spectrum. This tool is called spectroscopy or spectral analysis.

• Determining what elements make up a star:

| |

This illustration represents spectral lines from different known elements. Scientists can compare known spectra to an unknown pattern and determine what elements are in the mystery star. For example, the unknown star in this illustration would contain hydrogen and sodium.

• Determining star motion:

Stars emit light energy waves in much the same way ambulances emit sound waves.

The energy waves travel out in all directions from the source. When an object

comes toward you, energy becomes higher (blue light, higher pitch) and when it

goes away, energy becomes lower (red light, low pitch). This is the Doppler Effect.

ORIGINAL STAR SPECTRUM

(higher energy blue) (lower energy red)

SHIFTED SPECTRUM OF STAR MOVING AWAY FROM EARTH (RED SHIFT)

(higher energy blue) (lower energy red)

SHIFTED SPECTRUM OF A STAR MOVING TOWARD EARTH (BLUE SHIFT)

(higher energy blue) (lower energy red)

Our Solar System

• Protoplanet Hypothesis proposes how a solar system comes into being. The Sun (star) is created from swirling gas and dust in a nebula. Dust and gas left around after the star forms gathers together into smaller clumps. They get caught in the gravitational field of the larger Sun, forming the “solar” system.

• There are eight planets in our solar system: (and a few dwarf planetoids like Pluto).

• Planets are divided into inner and outer. The inner planets are small, rocky (terrestrial), dense, few or no moons. The outer planets are large, gaseous (gas giants or Jovian), low density, numerous moons, most have rings.

• Planetary data tables like the one on the next page compare planet criteria such as period of rotation (day), distance from the sun (AU), revolution period (year), etc. Generally, data tables compare other planets to Earth so Earth is often given the value of “1” for such things as distance from the sun (1 AU), period of rotation (1 day), mass (1) and gravity (1). For example, if a planet’s mass is “4”, it is 4 times greater than Earth whose mass is “1”. In general, the closer to the sun, the hotter the planet (Venus is the exception because of its very dense atmosphere leading to a horrendous greenhouse effect). The further away from the Sun, the longer the revolution period (time to travel around the sun or 1 year).

• Rotation and Revolution are easy to confuse. Use the following graphic to help you remember.

Revolution: planet revolves around sun once each year. Rev lution

Rotation: planet rotates on axis once each day. Ro ation

Orbit

Temp Period

Distance from Sun Distance from Sun

• Asteroids – small, rocky or metallic bodies mostly concentrated in the asteroid belt between Mars and Jupiter (inner and outer planets). Our Moon and atmosphere help to protect us.

• Comets are “dirty snowballs” made of ice and dust that have a regular, very elliptical orbit around our Sun that can be predicted. Comet tails only appear when they are near a sun. The hot, solar winds vapourize the ice and blow the tail in a direction that faces away from the sun (not trailing behind the comet as some people think). Comets have elliptical orbits with two focal points while circular orbits would have one central point. The further the focal points are apart, the more elliptical the orbit.

• The Sun’s path seems to change depending on the time of the year. It isn’t changing, but because out axis is tilted, our view changes. In winter, we need to look more toward the south to see it, and in summer we look more overhead. The solstices and equinoxes are based on these positions. The track of the sun across the sky is called the ecliptic.

• Constellations seem to move around in a circle in our night sky (precession), pivoting on Polaris (the North Star). It is not the constellations that are moving. It is the Earth rotating on its axis that gives the illusion of star motion. If you watch the Big Dipper for three hours, it will rotate about 45(. It is probably also time for you to get a life.

• Meteors, meteorites and meteoroids: Meteoroids are small pieces of rock that randomly float through space. Meteors are meteoroids that have been pulled into our atmosphere and are burning up. A meteorite is a meteor that didn’t completely burn up and lands on Earth. There are regular meteor showers that can be predicted because as our planet orbits the sun, it brings us into certain high areas of debris. While passing though these areas we can expect more of the debris to end up burning as it falls through our atmosphere. For example, the Leonid meteor shower every August.

• Eclipses

An eclipse of the Sun (or solar eclipse) can only occur at new Moon when the Moon passes between Earth and Sun. If the Moon's shadow happens to fall upon Earth's surface at that time, we see some portion of the Sun's disk covered or “eclipsed” by the Moon. At least twice a year, there is a solar eclipse somewhere on earth.

An eclipse of the Moon (or lunar eclipse) can only occur at full Moon, and only if the Moon passes through some portion of the Earth's shadow. This only happens 2-4 times per year. During a lunar eclipse, anyone on the night side of the planet can see at least a partial eclipse, and a full eclipse if you are in just the right place.

FINDING OBJECTS IN SPACE (Textbook pages 379, 401-402, 450)

Measuring Distances in space

• Astronomical Unit (AU) – distance between the centre of the Earth and the centre of the Sun (AU = 1). Used to measure distances within our solar system (i.e. Neptune is AU = 30 so it is 30 times as far from the Sun as Earth according to the planetary data tables).

• Light Year (LY) – distance light travels in one year. Used to measure distances outside of our solar system. Because light takes so long to reach us, we literally look into the past (sometimes billions of years) when we look at distant objects in space.

Parallax

• Parallax is the apparent shift in position relative to background stars. Background stars (stars seen in the distance behind the star of interest) are compared six months apart. If a star is closer, the apparent shift between background stars six months apart will be very noticeable. When looking at more distant stars, the shift is hardly noticeable. This technique can only be used for stars that are relatively close to us (within the Milky Way Galaxy). The apparent shift of more distant stars would be too small to detect.

Cellestial Sphere

• Imagine that the Earth is the center of the universe and that around the Earth there is a larger sphere, centered in the same point, in which the stars are fixed, as if they were painted in its internal surface. This imaginary outer ball is the Celestial Sphere and we use it to describe the locations of objects in space.

• Knowing angular coordinates of objects in the sky on the celestial sphere makes it so everyone has a common language with which to share information about location. The sphere can be described using azimuth (compass directions) and altitude (angle above the horizon).

• To measure azimuth: You need a compass. Azimuth

is from 0((N) to 360( (back to north). East is 90(,

south 180( and west 270(.

• To measure altitude, use an astrolabe and measure the angle between the horizon and the star you are looking at. Altitude can range from 0( (horizon) to 90( (zenith directly overhead).

The “star” on this celestial sphere would be at approximately 260º azimuth and approximately 50º altitude.

Triangulation measures distance to an object that cannot be reached. It does this by measuring angles between a baseline and drawing a scaled triangle.

Steps:

1. Lay out the baseline and determine its exact length. For the example below, say it was 100 m long.

2. Locate the object you want to find the distance to – in this case, a tree.

3. From one end of the baseline, use a protractor to determine the angle between

the point and the target (45( in the example below).

4. From the opposite end of the baseline, repeat the same procedure (40().

5. Make a scale drawing of the baseline (i.e., 1 m = 1 mm)

6. Complete the other two sides of the triangle by using a protractor to accurately measure the angles.

7. Mark a perpendicular line from the baseline to the point of intersection of the two lines (the location of the object).

8. Measure the perpendicular line with a ruler (39 mm).

9. Using the same scale as the baseline, convert the distance measured on the drawing to the actual distance of the object by using a ratio.

o Outside baseline = Unknown distance

Scaled baseline Scaled perpendicular

Cross Multiply:

100 m x __X__

100 mm 39 mm

X = 39 metres

39 mm

45( 40(

SPACE EXPLORATION TECHNOLOGY (Textbook pages 418-432)

Problems to Overcome

|PROBLEM |NEGATIVE EFFECT |SOLUTION |

|Microgravity |Almost no gravity in space. Bones become brittle due|Artificial gravity but it is too expensive to keep on |

| |to lack of resistance, heart and other muscles |all of the time. |

| |weaken, decrease in red blood cells | |

|Temperature |Extreme ranges of hot and cold. |Spacesuit, environmental control. |

|Clean Water |No water in space. Living things need water to |Recycling – 100% of water in space station is recycled|

| |survive. |through filters and water purification systems. |

|Air Pressure |No air pressure in space. Our bodies need to be |Artificial pressure in space station and in space |

| |under the right pressure in order to regulate our |suits. Air pressure will be constantly monitored. |

| |heartbeat. | |

|Breathable Air |No oxygen to breath in space. Most living things need|Use recycled water to produce air through electrolysis|

|(oxygen) |oxygen to survive. |(splitting H2O) into H2 and O2. Spacesuits have |

| | |oxygen supply. Permanent habitats will grow plants |

| | |for oxygen. |

|Solar Radiation |Can damage electrical circuits and kills living |Lead shielding, some protection built into visors and |

| |tissue. Can cause cancer. The longer the exposure |space suits. |

| |(i.e. trip to Mars), the higher the risk. | |

Space Transportation

• Multistage rockets: Used to transport things into space such as equipment and probes (the payload). They are all based on the principle of “for every action, there is an equal and opposite reaction. Exhaust shoots out the back, the rocket moves forward.

• Space Shuttles transport personnel and equipment to and from space. They are a big advantage over rockets since they are reusable and, therefore, cheaper.

• Space Station is an international project to set up the first permanent experimental station in orbit. It provides an orbital laboratory for research.

• Space Probes are used to explore places too distant or dangerous for human exploration. Probes have already landed on Venus and Mars and have flown past every other planet in the solar system.

• Solar Sails: A solar sail is a spacecraft without an engine, sped along its way by the direct pressure of light particles from the Sun being caught in a giant “sail”.

• Ion Drives: Ion drives are not particularly fast but they are very efficient. They use xenon as a fuel source.

Spinoff Technology

• We enjoy many inventions that would not have been possible without all of the extra research needed to get into space.

• Examples include motion sickness medicine, water purifying systems, microelectronics, internet, GPS, lightweight runners and helmets, etc.

Satellites

• Artificial satellites are built and sent into orbit by man (as opposed to natural satellites like our moon). There are over 2000 satellites currently in orbit.

• Wireless communication – long distance phone calls, T.V. – Satellite signals mean you don’t need cables to transmit data. These are in geosynchronous orbit which means they stay in one location high above the earth.

• GPS (Global Positioning System) – personal or auto tracking devices. 24 geosynchronous orbiting satellites mean that three are always above the horizon wherever you are. The three use triangulation to zero in on your GPS signal.

• Weather observation – stay in geosynchronous orbit to track storms 24 hours a day for an area.

• Remote sensing – LANDSAT and RADARSAT monitor ship movement, forest fires, environmental changes (ozone), and search for natural resources. This information is then sent back to Earth. These satellites move across the sky in a low orbit to monitor different locations.

TELESCOPES (Textbook pages 436-443)

Optical telescopes

• pick up energy from the visible light range of the electromagnetic spectrum. They may be refracting or reflecting. They are present on the earth, but there is also an orbiting optical telescope Hubble).

• Optical telescopes have been around for hundreds of years and have been improved tremendously. However, the earth-bound telescopes have problems seeing through the atmosphere with its moisture, clouds, light pollution and smog.

Refracting telescopes use two lenses to gather and focus light. The largest the objective lens can be as big as 1 m across. After that, the glass becomes too heavy and warps under its own weight. Light enters the aperture (opening at the end) and as it passes through the convex lens, the light rays converge. The image would come into focus where the rays converge. A magnifying lens is then used to bring the clear image to our eyes. Refracting telescopes give very clear images.

Reflecting telescopes use mirrors to gather and focus light. Mirrors can be one large one or several smaller ones. Light enters through the aperture, bounces off the concave mirror at the far end and converges at a secondary mirror. Light is then reflected toward a magnifying lens in the eyepiece. Although the image is not as clear as refracting, it can gather a lot more light so can see more distant objects.

Hubble Space Telescope is an orbiting reflecting telescope. Because it does not have to contend with atmospheric interference, it can see much further and much more clearly than Earth-based telescopes.

Radio Telescopes

• Pick up energy from the radio wave (lowest energy or longest wavelength) part of the electromagnetic spectrum. Radio waves are received from stars, galaxies, nebula, some planets and even parts of space that appear empty. Their advantage is that they are not affected by atmosphere, light, weather and pollution that plague Earth-based optical telescopes. Radio telescopes pick up signals using a satellite dish which focuses the signal toward a central antenna.

• The input of several telescopes (radio or optical) can be added together to increase overall resolution (clarity of image). This is called interferometry. With radio telescopes, the larger the field of dishes, the higher the resolution.

Canadian Contributions to Space Exploration

• Canadarm I and Canadarm II help repair and move things around on space stations.

Astronauts:

• Marc Garneau – first Canadian in space 1984

• Roberta Bondar -first Canadian female in space 1992

Space Exploration Issues

Costs versus benefits

• Ethical viewpoint - should we be spending so much when there are starving people?

• Environmental viewpoint- we could better use the money for cleaning up our own planet but satellites do allow us to better monitor sensitive areas.

• Economic viewpoint - benefits could be new resources, new jobs, but should we be using precious resources on objects that will never be recovered?

• Societal viewpoint - new home for the future, people in remote locations need to have communication so satellites are necessary.

Who owns the resources in space (i.e. mining on asteroids and on the moon)?

• Political viewpoint – whichever country gets there first

• Environmental viewpoint – whoever will protect it and clean it up

• Ethical viewpoint – we don’t have the right to exploit other worlds and if we

do, the benefits should be shared by all people on Earth

• Economic viewpoint – whoever has the money to develop the resources.

SPACE EXPLORATION VOCABULARY REVIEW

1. The summer solstice is the longest day of the year, when the sun is at its most northern position (June 21st).

2. The winter solstice is the shortest day of the year, when the sun is at its most southern position (Dec. 21st).

3. The equinoxes are days when the sun is exactly in the middle of the ecliptic so day and night are close to being equal. Fall equinox is Sept. 21st and spring equinox is March 21st.

4. Stonehenge in England and medicine circles in southern Alberta are two examples of monuments that keep track of solstices and equinoxes for religious and agricultural purposes.

5. Aristotle’s geocentric model of the solar system had the Earth in the centre and everything else orbiting around it.

6. Copernicus’s heliocentric model of the solar system had the sun in the middle and everything else orbiting around it in circles.

7. Kepler used mathematics to prove that orbits were elliptical rather than concentric.

8. Unlike circles which have one focal point in the middle, ellipses have two focal points.

9. Thousands of years ago people kept track of time by watching the shadow the sun cast on a sundial.

10. The scientists credited for refining the telescope is Galileo.

11. The distance from the centre of the sun to the centre of the Earth is

150 000 000 km or one astronomical unit (AU).

12. Because distances outside of our solar system are so great, light years, which are the distance light travels in one year going at 300 000 km/sec (9.5 trillion km) are used.

13. Triangulation is the method for finding the distance to objects that are inaccessible by using simple geometry.

14. Astronomers use parallax, which is the apparent shift of an observed star relative to the stars behind it, to determine relative distances of stars in space.

15. Stars like our sun are hot, glowing nuclear furnaces that produce their own energy.

16. Stars are made primarily of hydrogen and helium.

17. The surface of the sun has an “atmosphere” called the chromosphere, cool storms called sunspots and massive gas ejections called solar flares.

18. Charged photon particles (mostly electrons and neutrons) called the solar winds travel out in all directions from the surface of the sun at extremely fast velocities. Our magnetic poles protect us from most of these particles as evidenced by the aurora borealis.

19. The Hertzsprung-Russel diagram is used to categorize stars by comparing their temperature and luminosity (brightness).

20. According to the HR diagram, most stars fall in the middle range of temperature and luminosity and are called main sequence stars (like our sun). Much larger stars are called massive stars.

21. Red giants are cooler, huge stars that are the dying stage of a main sequence star. These collapse down into a very hot and bright white dwarf and will eventually die as a black dwarf.

22. Red supergiants are cooler, huge stars that are the dying stage of a massive star. From this stage, the star will explode in a supernova and then collapse into an extremely dense, spinning neutron star or into a black hole.

23. The birthplace of stars are nebula where clouds of gas and dust start swirling into a compacted, glowing protostar before becoming a full-fledged star.

24. Small groups of “star pictures” that are recognizable all over the world are called constellations (i.e. Ursa Major) while more local names for “star pictures” are called asterisms (i.e. Big Dipper).

25. Groupings of billions of stars in one quadrant of space are called galaxies and they can be spiral (like our Milky Way), elliptical (like a football) or irregular (no real form).

26. The protoplanet hypothesis suggests that planets orbiting suns come from left over dust and gas particles in the vicinity of the new sun.

27. Inner planets are small and rocky so are called terrestrial while outer planets are large and gaseous so are called gas giants or Jovian. Inner and outer planets are separated by an asteroid belt.

28. Astronomical units compare Earth’s distance from the sun to the distance of other planets. Rotation (time to rotate once on the axis) is compared to one day on Earth and revolution (time to revolve around the sun) is compared to one year on Earth.

29. Dirty snowballs that have a regular elliptical orbit around the sun are called comets.

30. Asteroids are large metallic bodies that orbit the sun and are concentrated in the belt between Mars and Jupiter.

31. The Kuiper Belt is just beyond our solar system and scientists think that Pluto may be a stray asteroid from here.

32. Meteorioids orbit the Earth while meteors glow as they fall through the atmosphere and meteorites hit the surface of our planet.

33. Altitude and azimuth can be found using an astrolabe which can be made from a string attached to a protractor.

34. The Sun’s path across the sky from east to west traces the ecliptic on the celestial sphere.

35. The celestial sphere is an imaginary dome that surrounds the earth as we look at stars behind it and it gives us a way to locate object in the sky. The directions on the horizon of this dome are the azimuth (0-360˚) and the height above the horizon is the altitude (0-90˚). The point directly at the top of the dome is called the zenuth.

36. Only 6% of a rocket’s load is reserved for the crew and their supplies. This is called the payload.

37. When an exploration site is too far or too dangerous for humans, we send space probes which carry scientific tools for testing and photographing the alien surfaces.

38. Right now, space shuttles are the best method we have for transporting people into and back from space.

39. One of the most dangerous conditions that astronauts in space for long periods of time will have to deal with is microgravity because of its effect on the heart, other muscles, and bones.

40. Because there is no oxygen in space, it may be made by splitting a recycled water molecule into hydrogen and oxygen through the process of electrolysis.

41. Satellites that stay in one position above the surface of the earth by moving at the exact speed as Earth’s rotation are said to be in geosynchronous orbit.

42. Remote sensing involves satellites such as LANDSAT and RADARSAT that move to different locations in search of natural resources, pollution, forest fires, ship movement or global land forms. These satellites travel far more quickly than the Earth’s rotation speed.

43. With 24 orbiting satellites, three are always above the horizon and able to locate anyone who has a global positioning system (GPS) device. They do this through triangulation.

44. The electromagnetic spectrum includes the range of energy from very low frequency radio waves to very high frequency gamma rays.

45. Optical refracting telescopes use two convex lenses to gather and focus light from the stars.

46. Optical reflecting telescopes use mirrors to gather and focus light from the stars.

47. The orbiting Hubble telescope is powered by solar energy and operated through remote control from Earth so that it can be aimed to observe objects from deep space.

48. Telescopes that pick up low energy radio waves and convert them to visual data are called radio telescopes.

49. Several telescopes combined together to increase resolution (clarity) are using a process called interferometry.

50. Scientists use spectrometers to look at the colour spectra emitted by stars, each as unique as a fingerprint.

51. The Doppler effect refers to the behaviour of energy waves (light in the case of astronomy) as they move toward or away from an observer. An object moving toward Earth will have a blue shift indicating higher energy compressed waves while objects moving away will have a red shift indicating lower energy stretched waves.

52. Astronauts orbiting Earth are in danger from space junk which includes old nuts, bolts, paint chips, and even a camera traveling at extremely high velocities.

53. The Canadarm I on the space shuttle and the Canadiarm II on the International Space Station are an important Canadian contribution to the space program.

54. The first Canadian astronaut in space was Marc Garneau.

55. The first female Canadian astronaut in space was Roberta Bondar.

-----------------------

Sun rises in east Sun at noon Sun sets in west

Big Dipper

asterism

Main Sequence:

nebula ( star (sun) ( red giant ( white dwarf ( black dwarf

fusion begins outer layers expand compresses and turns cold

and star cools heats up

Massive Sequence:

nebula ( massive star ( red supergiant ( supernova ( neutron star or black hole

fusion begins outer layers expand explodes implodes into extremely dense object

and star cools

Hydrogen

Helium

Sodium

Iron

Unknown

The greater the shift over time, the faster the star is either moving. The star moving away would be moving faster than the one moving toward us since the red shift is greater than the blue shift.

Drawing an ellipse

Summer

ecliptic

Winter

ecliptic

compass

astrolabe

100 mm baseline

High orbit geosynchronous satellites stay above the same area of the globe and provide information such as weather, communication and GPS data.

Low orbit satellites cover different areas of the globe. Used for remote sensing.

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