Birth of Stars
The cloud of dust and gas that may form a star
Nebula
A star will spend this percentage of its life as a main sequence star.
90%
As a sun-sized (or larger) star leaves the main sequence, it will become this in the the next phase of its life.
a red giant (or red supergiant)
The event that signals that a star is no longer a star is ____ .
fusion stops happening
The final outcome of a star after it blows off its outer layers depends only on. this.
its mass
When this happens, the cloud of dust and gas officially becomes a star
Fusion (of hydrogen)
During the main sequence stage of a star's life, these two forces must balance each other.
gravity (inward) and heat (outward)
Compared to a main sequence star, most red giants are more luminous. (T of F)
True
The most massive of stars will become these at the end of their lives.
black holes
After a sun-sized star blows off its outer layers, the remaining core becomes this.
white dwarf
This force is what causes the cloud of dust and gas to heat up enough for fusion to occur
gravity
More massive stars spend more time on the main sequence than less massive stars
False
The main reason for the high luminosity of a red giant (or red supergiant) is _____ .
their large size
Stars that are at least 5x more massive than our sun will erupt into a _____ as they leave the main sequence.
supernova explosion
The core of a star that is 1.5 to 5 times the mass of our sun will become this.
neutron star
In the earliest stages of a star, _______ fuses to make ___________ .
hydrogen...helium
What factor determines what a main sequence star will become once it has burned up it hydrogen fuel?
the mass of the star
The surface of a red giant (or red supergiant) is (hotter / cooler) than the main sequence star from which it formed?
cooler
By the time the hydrogen fuel is used up, this has built up in the core of the star.
helium
The core of a star that is greater than 5 time the mass our out sun will become this.
black hole
If the nebula never gets hot enough to start fusion, it is simply called a ____ .
brown dwarf
red dwarf
The nebula formed by the ejection of the outer layers of a sun-sized or larger stars is called this.
planetary nebula
When fusion in the core stops, what happens to the core?
it will collapse under its own weight
The radius around a black hole, from which nothing, not even light, can escape is called this.
event horizon.