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Astronomy Part 2. Earth in the Universe Motions of Earth, Moon, and Sun. Earth in the Universe. Eccentricity and Ellipse. An ellipse is an oval shape. Earth’s orbit around the sun is an ellipse. Within an ellipse, there are two fixed points called foci .
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Astronomy Part 2 Earth in the Universe Motions of Earth, Moon, and Sun
Eccentricity and Ellipse • An ellipse is an oval shape. • Earth’s orbit around the sun is an ellipse. • Within an ellipse, there are two fixed points called foci. • In our solar system, the sun is ALWAYS ONE of those foci.
You can make an ellipse with 2 tacks and a string. The tacks are the “foci”, and if you put them further apart, the ellipse is more “eccentric” (one tack makes a circle). An ellipse is an example of a “conic section”. Circles and hyperbolas are others. All are possible forms for orbits.
Eccentricity and Ellipses • The degree of flatness or “ovalness” of an ellipse is measured by eccentricity. • This formula is on page 1 of your ESRT!
Eccentricity and Ellipse • The more oval the orbit is, the more eccentric it is, or the higher the eccentricity. Increasing Eccentricity
Eccentricity and Ellipse • Calculating Eccentricity: Major Axis X X Foci 1 Foci 2
Eccentricity and Ellipse • Calculating Eccentricity: • When you measure those 2 distances and calculate them, you will NEVER get higher than 1!! • The closer to 1 you are the MORE oval or eccentric the orbit. • The closer to 0 you are the LESS oval or eccentric the orbit.
Gravitational Force • The closer 2 objects are to each other, the greater the gravitational pull between them. • Therefore, during the perihelion – when Earth is closer to the sun, there is a greatergravitational pull between it and the sun. • This makes the Earth speed up a bit in its orbit around the sun during that time.
Gravitational Force Perihelion Aphelion
The Big Bang Theory • The universe started with a concentrated area of matter and energy. • 15-20 billion years ago. • Then, it exploded and has been expanding ever since. • Faster moving stuff traveled farther.
The Big Bang Theory • Matter began to clump together forming stars and galaxies. • The universe continued to expand and is still expanding today.
The Big Bang Theory • What proof do we have that the big bang did happen? • 1. Recently, scientists have found long-wave radiation coming from all directions in the universe. This is the energy that was created from the Big Bang. • 2. The universe is still expanding.
Universe Expansion • How do we know the universe is expanding? • Pg. 14 in the ESRT shows the electromagnetic spectrum. • Notice that in the visible spectrum there are all the colors of the rainbow.
Pg. 14 ESRT Longwave Shortwave
Universe Expansion • When looking at the visible spectrum wavelengths are shifted either to the blue end (shorter wave) or the red end (longer wave). • This shift in wavelengths is called the Doppler Effect. • If they are shifted towards red, they are moving away from you. • If they are shifted toward blue, they are coming towards you.
Universe Expansion • When scientists look at the universe, they see a red shift. This proves it is moving away from us, thus, expanding!
Red Shift Light from galaxies moving away Notice the shift to the red end
Blue Shift Light from galaxies moving toward us Notice the shift to the blue end
Galaxies • The basic unit of matter in the universe is a galaxy. • A galaxy is a collection of billions of stars and gas and dust. • Our solar system is part of the Milky Way Galaxy. • The Milky Way is a spiral-shaped galaxy.
Stars • A star is usually a large ball of gas held together by gravity. • Produce tremendous amounts of energy and they shine. • Energy is produced by nuclear fusion – combination of nuclei of smaller elements to form nuclei of larger elements.
Stars • Stars have different: • Size • Composition • Temperature • Color • Mass • Brightness
Stars • SIZE – 5 main categories: • 1. Medium sized • 2. Giants • 3. Supergiants (Largest) • 4. White Dwarfs • 5. Neutron Stars (smallest)
Stars • COMPOSITION • Mostly made up of hydrogen (60-80%) • Most of the rest is helium. • About 1% of other elements. • Determined by looking at the color of the star.
Blue White Yellow Red Stars 35,000 °C • TEMPERATURE • Color also indicates temperature • hottest surface 50,000 °C • coolest -3000°C • Blue are hottest stars. • Red are coolest stars. 10,000 °C 6,000 °C Red-Orange 5,000 °C 3,000 ºC
Stars • BRIGHTNESS • A measure of a stars brightness is its magnitude. • Apparent magnitude is how bright it looks from Earth. • Absolute magnitude is how bright it really is.
Stars • Hertzsprung-Russell Diagram: • Found that as temperature increased, so did absolute magnitude. • 90% of stars followed this pattern • Called main sequence stars • Other 10% were once main sequence stars but have changed over time.
Supergiants Giants Main sequence White Dwarfs Absolute Magnitude 50000 20000 10000 6600 6000 5000 3000
Our Solar System • The solar system is the sun and all objects that orbit the sun under its gravitational influence. • Our solar system has 1 sun and 8 planets.
Our Solar System • The Sun • An average star – Main Sequence • Over 1 million Earth’s would fit inside. • 1/4 the density of the Earth. • Made of 4 layers.
