Accretion among the grains in the solar nebula would have been aided by
a. static electricity.
b. gravity.
c. high-velocity collisions.
d. all of the above
e. none of the above
Question 2The habitable zone is
a. the region on a planet where conditions are acceptable for life to exist.
b. a region around a star where a planet's temperature would permit the existence of liquid water.
c. very small for a massive star.
d. only found around G and K stars.
e. a region on a young planet where amino acids can begin to form DNA molecules.
Question 3The large planetesimals would have grown faster than the smaller planetesimals because
a. they were moving faster in their orbits than the smaller planetesimals.
b. their stronger gravity would pull in more material.
c. there was more material located near them that could be accreted.
d. the smaller planetesimals were covered by a layer of material that was lost during collisions.
e. all of the above
Question 4Presuming that it takes several billion years of complex live to evolve in a stable environment, the stars most likely to currently have inhabited planets are
a. G to K main sequence stars.
b. B to A main sequence stars.
c. G to K giants.
d. white dwarf stars
e. neutron stars.