History of our Scientific Understanding of Space
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Cosmological Events
Solstice (Latin: sol – sun, stice – stop) Equinox (Latin: equi – equal, nox – night) Many early cultures honoured cosmological events including the solstice and equinox. In the Northern hemisphere, the summer solstice occurs around June 21 and the winter solstice occurs around December 21. The equinox was also honoured by early cultures. The Spring equinox occurs around March 21 and the fall equinox occurs around September 22. |
Models of Planetary Motion
Throughout history, humans have been incredibly curious about the night sky. The sun has played a key role in mythology for many cultures. Originally, humans believed that the Earth was at the centre of our solar system, and that the sun rotated around us. This is called the Geocentric Model.
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The Heliocentric Model of planetary movement changed the way people viewed the solar system. According to this model, the sun was at the centre of the solar system and the Earth and other planetary bodies orbited it in a pattern known as an ellipse.
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How our Solar System was Formed
Stars are born in stellar nurseries known as NEBULAE. We will look more closely at this a little later!
Our solar system is believed to have been born through this process. The birth of solar systems can be explained through the protoplanet hypothesis shown to the left.
Our solar system is believed to have been born through this process. The birth of solar systems can be explained through the protoplanet hypothesis shown to the left.
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Measuring Distance in Space
The distance of stars and other “objects in space” are so far away that we have to come up with different ways to measure them.
Astronomical Unit vs Light Years
- measures distance IN our solar system - measures distance OUTSIDE our solar system
- 1 AU = distance of center of sun to Earth - 1light year = distance light travels in 1 year
- 1 AU = 149 599 000km - light speed = 300 000 km/s
- used for position of planets - 1 year = 31 557 600s
- distance is ~ 9.5 trillion km
- measures distance IN our solar system - measures distance OUTSIDE our solar system
- 1 AU = distance of center of sun to Earth - 1light year = distance light travels in 1 year
- 1 AU = 149 599 000km - light speed = 300 000 km/s
- used for position of planets - 1 year = 31 557 600s
- distance is ~ 9.5 trillion km
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What is a Star?
A star is a burning ball of gas, much like our sun, and is comprised primarily of hydrogen. Stars give off massive amounts of energy, primarily LIGHT energy.
There are billions of billions of stars in our KNOWN universe, and because there are so many, they take on a variety of different properties. The star at the centre of our solar system is a "Sun-Like" star, while others are called Massive Stars.
Our sun has a mass that is 300 000 times that of Earth, and Betelgeuse is 670 times larger than the sun BUT, is only 1/10-millionth as dense. This star is set to supernova, and may have done so already!
There are billions of billions of stars in our KNOWN universe, and because there are so many, they take on a variety of different properties. The star at the centre of our solar system is a "Sun-Like" star, while others are called Massive Stars.
Our sun has a mass that is 300 000 times that of Earth, and Betelgeuse is 670 times larger than the sun BUT, is only 1/10-millionth as dense. This star is set to supernova, and may have done so already!
Stars and Colour:The hotter a star is, the more blue it is in colour. The cooler a star is, the more red it is in colour! In 1920, 2 scientists (Hertzsprung and Russell) determined that there was a relationship between the brightness and the temperature of stars. The “Hertzsprung-Russell Diagram” shows this relationship.
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Section Review
- Describe the difference between equinox and solstice. What are the common dates associated with them? Why were these events important for ancient people?
- Explain how the geocentric and heliocentric models of the solar system are different/similar.
- Compare the views of Copernicus and Kepler. What work did they do and how did they prove it?
- What are the 2 different ways to measure distance in space? Describe a situation where each would be used.
- Describe the initial phases of star formation. How is this different from the mid-phase?
- We have named the apparent patterns of star groupings in the sky. What are the 2 names we have given?
- The sun is the center of our solar system. What is the name for the path that the sun appears to follow in the sky? Describe the parts of the sun, as labelled on page 393 of your text.
- Describe the key differences between inner and outer planets.
- What are the differences between meteoroids, comets and asteroids? Consider their composition.