Approximately, what basic composition are all stars born with?
three-quarters hydrogen, one-quarters helium, no more than 2 percent heavier elements
If the distance between us and a star is doubled, with everything else remaining the same, the luminosity...
remains the same, but the apparent brightness is decreased by a factor of four.
When does a star become a main-sequence star?
when the rate of hydrogen fusion within the star's core is high enough to maintain gravitational equilibrium.
Which of the following best describes the axes of the Hertzsprung-Russell (H-R) diagram?
surface temperature on the horizontal axis and luminosity on the vertiaval axis
What happens to the rotation of a molecular cloud as it collapses to form a star?
The rotation rate increases and results in a disk of material around a protostar.
Suppose you measure the parallax angle for a particular star to be 0.25 arcesecond. The distance to this star is...
What is the smallest mass a newborn star can have?
80 times the mass of Jupiter or .08 times the Sun's mass
Where would a brown dwarf be located on an H-R diagram?
below and to the right of the lowest part of the main sequence