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Star
- Self-luminous, gaseous objects that fuse elements
- Obtain energy from nuclear fusion
- Considered a star when it can sustain itself through nuclear reactions (making its own energy)
- How long it takes a star to form depends on its mass
Distance from the Earth
- Parallax
- Limited to ~400 light-years
- Using brightness measurements
- Look at the star, determine it's color spectrum (good indication of it's actual brightness)
- Compare the actual brightness with the apparent brightness, they can determine the Distance
- It's apparent brightness will be dimmer