CP 16 Star-Forming Clouds Flashcards
Most interstellar clouds remain stable in size because the force of gravity is opposed by __________ within the cloud.
thermal pressure
What conditions of gas cloud is most likely to give birth to stars?
a cold, dense gas cloud
Which molecule is the most abundant in an interstellar molecular cloud?
H2
How do we learn the chemical composition of the interstellar medium?
By studying spectra of interstellar gas clouds
Which part of the electromagnetic spectrum generally gives us our best views of stars forming in dusty clouds?
infrared
What is the cloud required to do to allow a gravitationally-collapsing gas cloud to continue to collapse?
The cloud must radiate away much of its thermal energy.
Which two processes can generate energy to help a star or gas cloud maintain its internal thermal pressure?
nuclear fusion and gravitational contraction
TF The first stars born in the universe were made only of Hydrogen and Helium
T
During the time before fusion begins, a protostar’s core gradually ________.
shrinks and heats
When does a protostar become a main-sequence star?
when rate of H fusion = rate which the star radiates energy into space
Approximately what core temperature is required before hydrogen fusion can begin in a star?
10 million K
Why are the very first stars thought to have been much more massive than the Sun?
The temperatures of the clouds that made them were higher because they consisted entirely of hydrogen and helium.
What is the approximate range of masses that newborn main-sequence stars can have?
0.1 to 150 solar masses
If a star is extremely massive (more than 100-solar masses), why isn’t it likely to survive
It may blow itself apart because of radiation pressure.
