Luminosity and Magnitude
What does luminosity measure about a star?
The total energy a star emits per second.
What process led to the formation of planets from a disk of gas and dust?
Accretion.
What is the main element fused in a star’s core during the main sequence?
Hydrogen.
What two factors determine a star’s luminosity?
Temperature and size (surface area).
What are the inner planets mostly made of?
Rock and metal.
What does an average-sized star become after the red giant stage?
A white dwarf.
What does apparent magnitude describe?
How bright a star appears from Earth.
Why did gases like hydrogen and helium not stay near the inner planets?
It was too hot for light gases to condense or be held by gravity.
What happens to a massive star’s core after it runs out of fuel?
It collapses, causing a supernova.
Two stars have the same apparent magnitude, but one is farther away. Which has the greater luminosity?
The farther one.
Why are the outer planets able to form thick atmospheres?
The cold temperatures allowed them to attract and hold light gases.
Why does a massive star have a shorter lifetime than a small star?
It burns through its fuel much faster.
Why can a very luminous star appear dimmer than a less luminous one?
Because it’s much farther from Earth, so its light spreads out more.
How does the composition difference between inner and outer planets show the temperature gradient in the early solar nebula?
It shows that higher temperatures near the Sun allowed only heavy materials to condense, while lighter gases condensed farther out.
How do the end products of an average star and a massive star differ, and why?
Average stars become white dwarfs because gravity is balanced by electron pressure, while massive stars collapse further into neutron stars or black holes because gravity overcomes all pressures.