the theory that the planets formed from the same cloud of gas and dust that formed the sun (p.321; video lesson; objective 1)
a small, rocky world. Most asteroids lie between Mars and Jupiter in the asteroid belt.
the collection of icy planetesimals believed to orbit in a region just beyond Neptune out to 100 AU or more
one of the small icy bodies that orbit the sun and produce tails of gas and dust when they approach the sun.
A small bit of matter heated by friction to incandescent vapor as it falls into Earth's atmosphere. Also refers to the flash of light seen in the sky (i.e. a shooting star)
a meteor in space before it enters Earth's atmosphere. The small piece of space debris.
a piece of space debris that produces a meteorand survives its passage through the atmosphere and strikes the ground.
the time required for half the atomsin a radioactive sample to decay.
an earthlike planet; small, dense and rocky.
Jupiter-like planet with a large diameter and low density.
the density that a planet would have if its gravity did not compress it.
Ice line or snowline
the demarcation point between the inner and outer regions of our solar system where temperatures are low enough for water to condense out of the solar nebula and form ice. These ice particles stick to rocky planetesimals allowing for rapid growth into larger planets.
the sequence in which different materials condense from the solar nebula as we move outward from the sun
one of the small bodies that formed from the solar nebula and eventually grew into protoplanets
the growth of a particle, atom by atom, by addition of material from surrounding gas
the sticking together of solid particles to produce a large particle
massive object resulting from the coalescence of planetesimals in the solar nebula and destined to become a planet
the rapid accumulation of a large amount of in-falling gas
heat of formation
inplanetology, the heat released by infalling matter during the formation of a planetary body
the separation of planetary material accoording to density
the release of gases from a planet's interior
the force exerted on the surface of a body by it's absorption of light. Small particales floating in the solar system can be blown outward by the pressure of the sunlight
the intense cratering during the first 0.5 billion years in the history of the solar system
cold dust disks that formed around some stars
a planet orbiting a star other than the sun
when and orbiting planet crosses in front of the star
the hypothetical source of comets. A swarm of icy bodies believed to lie in a spherical shell extending to 100,000 AU from the sun