Science - Chapter 12

astronomical unit (AU)

a unit of distance equal to the average distance between Earth and the sun, about 150 million kilometers

ellipse

an oval shape, which may be elongated or nearly circular; the shape of the planets’ orbit

dwaf planets

an object that orbits the sun and is spherical, but has not cleared the area of its orbit

comet

a loose collection of ice and dust that orbits the sun, typically in a long, narrow orbit

meteor

a streak of light in the sky produced by the burning of a meteoroid in Earth’s atmosphere

meteoroid

a chunk of rock or dust in space, generally smaller than an asteroid

meteorite

a meteoroid that passes through eh atmosphere and hits Earth’s surface

nuclear fusion

The process in which two atomic nuclei combine to form a larger nucleus, forming a heavier element and releasing huge amounts of energy; the process by which energy is produced in stars

sunspot

a dark area of gas on the sun’s surface that is cooler than surrounding gases