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Electromagnetic radiation
- Radiation consisting of electromagnetic waves that travel at the speed of light
- Such as visible light, radio waves, and X rays
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Refracting telescope
- When a telescope uses a lens to collect the light from an object

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Reflecting telescope
- a telescope that uses a mirror to collect light from an object

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Satellite
- an artificial object or vehicle that orbits Earth, the moon or any other celestial body
- Also a celestial body that orbits another body of a larger size
- i.e. Moon is one of Earth's natural satellites
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Orbiters
Observatories that orbit other celestial objects
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Solar nebula theory
- The theory that describes how stars and planets form from contracting spinning disks of gas and dust

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Star
a celestial body made of up gases mostly hydrogen and helium
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Nebula
- A vast cloud of gas and dusts
- It might be the birthplace for stars and planets
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Protostar
- a hot condensed object in the center of a nebula

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Nuclear fusion
- The process when hydrogen nuclei form together to become helium nuclei
- Generates energy
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Photosphere
thee surface layer of the sun
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Sunspot
an area of strong magnetic field on the photosphere
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Solar wind
A stream of fast moving charged particles ejected from the sun into the solar system
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Solar flare
- They happen when there is a complex group of sunspots
- It is when magnetic fields explosively eject intense streams of charged particles into space.
- Streams are called solar wind
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Importance of the Sun
- The sun rays provide us heat that we need to survive and sustain ourselves
- Another thing it provides is visible light
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Luminosity
- A star's total energy output per second
- Its power in joules per second (J/s)
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Absolute magnitude
The magnitude of a star we would observe if it was 32.6 light years away form Earth
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Spectroscope
- an optical instrument that produces a spectrum from a narrow beam of light
- Usually projects the spectrum onto a photographic plate or digital detector
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Spectral lines
- Certain wavelengths within a spectrum characterized by lines
- Spectral lines identify specific chemical elements
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Hertzsprung-Russell (H-R) diagram
 - A graph that compares the qualities of stars
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Main sequence
- It is a narrow band of stars on the H-R diagram that runs diagonally from the upper left (bright and hot stars) to the lower right (dim and cool stars)
- The Sun is in the main sequence

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White dwarf
a small dim, hot star
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Supernova
a massive explosion in which the entire outer portion of a star is blown off
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Neutron star
A star that is so dense that only neutrons can exist in it's core
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How low-mass stars evolve
- They consume their hydrogen slowly, as long as 100 billion years
- During that time they lose significant mass (evaporating)
- When they lose fuel they become white dwarfs
- Still hot, takes billions of years to cool down (becomes black dwarfs).
- Universe not old enough for black dwarfs
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How intermediate-mass stars evolve
- Consume hydrogen faster than low mass stars
- over 10 billion years
- When fuel gone core collapses and
- As core contracts temperature increases and the outer layers expand
- Outer layers are cooler and look red
- It becomes a red giant and after layers disappear into space they become white dwarfs
- The heavier elements formed were ejected into the universe and become new stars
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How high-mass stars evolve
- Consumer fuel faster than low and intermediate stars
- Core heats up to higher temperatures which means heavier elements form by fusion
- When the core becomes iron, since it cannot release energy through fusion it violently collapses and the outer portion of the star will explode called a supernova
- Supernova's can be millions of times brighter than the original star was
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Black hole
- The leftovers of a supernova with a gravitational field so strong that nothing can escape it's pull
- Not even light
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