Chapter 5 Flashcards
What is a planetary nebula?
Result of a relatively gentle stellar outburst in which matter is ejected into space
What was the material from which the solar system formed?
nebula made mostly of hydrogen and helium gas but enriched in heavier elements from supernova explosions
Hydrogen and helium together account for what percentage of the total mass of all the matter in the universe?
98%
Where was all the hydrogen in the universe formed?
in the Big Bang, at the very beginning of the universe
What are the three “common” substances that are believed to be important in planet formation?
rock, ices, and gas
Where in the universe are heavy elements with masses greater than that of helium being produced at this time?
in the central cores of stars
The most likely mechanism for the solar system is that the
Sun and planets slowly condensed to their present form from a gas and dust cloud
Why did the temperature start to rise at the center of the solar nebula?
The nebula was contracting, which increased the speed of the atoms moving in it.
The most probable theory for the formation of the solar system is
the condensation of a nebula of cold gas and dust into the Sun and planets
Accretion is the process by which
dust grains and ice crystals coalesce to form planetesimals.
The most probable time sequence for the formation of the solar system was the following:
The Sun contracted first as a gas ball, and the planets and moons formed shortly afterward by accretion and condensation.
The formation of terrestrial-type planets around a star is most likely to have occurred by what process?
accretion, or slow accumulation of smaller particles by mutual gravitational attraction
The manner in which the large, outer planets formed in our solar system was most likely the
accretion of planetesimals to form a core, followed by the gravitational capture of hydrogen and helium gas.
Viewed from a position above the north pole of the Sun, the direction of the motion of the planets in their orbits is
counterclockwise.
Each of the following characteristics is included in the formal definition of a planet except one. Which is the exception?
spins fast enough to produce its own magnetic field
