| A | B |
|---|
| electromagnetic energy/radiation | energy that can travel through space in the form of waves (radio-infrared-visible light-ultraviolet-x-rays-gamma) |
| visible light | one type of electromagnetic radiation - the light you can see |
| apparent brightness | a star's brightness as seen from Earth |
| absolute brightness | the brightness a star would have if it were at a standard distance from Earth |
| light-year | the distance that light travels in one year, about 6 trillion miles |
| nebula | a large cloud of gas and dust where stars are born |
| protostar | Gravity pulls the gas & dust together, forming a contracting cloud of gas and dust with enough mass to form a star. Note: A star is born when nuclear fusion starts. |
| white dwarf | what a low & medium-mass star becomes once it's fuel is gone |
| black dwarf | what a white dwarf becomes once it stops glowing |
| supernova | the explosion of a supergiant when it runs out of fuel |
| neutron star | forms from the remains of a lesser massive supergiant after a supernova |
| black hole | forms from the remains of the most massive stars, after a supernova |
| star system | groups of 2 or more stars |
| binary stars | star systems that have 2 stars |
| galaxy | a huge group of single stars, star systems, dust & gas bound together by gravity |
| spiral galaxy | a galaxy that bulges in the middle and has arms that spiral out - our Milky Way galaxy is an example |
| universe | all of space and everything in it |
| Big Bang theory | the theory of how the universe formed, with a huge explosion |
| Hubble's Law | all galaxies are moving away from each other, and the farther away a galaxy is the faster it's moving away from us |
| dark energy | what astronomers think is causing the expansion of the universe to accelerate |
| cosmic background radiation | leftover thermal energy (heat) from the big bang |
| solar nebula | a large cloud of gas & dust the formed our SOLAR system |
| refracting telescope | an optical telescope that uses convex LENSES to gather & focus light |
| reflecting telescope | an optical telescope that uses a curved MIRROR to gather & focus light |
| 5 characteristics used to classify stars | color, temp., size, composition & brightness |
| main sequence stars | Most stars, including the Sun are main sequence stars. On H-R diagram, absolute brightness increases as temperature increases. |
