Classifying stars
The total amount of energy radiated by an object every second
Luminosity
the leftover core of
a massive single star after a supernova. Black holes exert such large gravitational pull that not even light can escape
stellar black hole
A large, cold cloud made up mostly of molecular hydrogen and helium, but
with some other gases, such as carbon monoxide. It is in these clouds that new stars are born.
molecular cloud
How do astronomers classify stars?
Astronomers classify stars by their brightness, which is determined by using a magnitude scale. Astronomers also use color and temperature in their classification of stars.
star formed when the temperature in the center of a cloud reaches 15 million K, starting up the stellar fusion.
Main-sequence star
How stars are born.
A star is born when the material in a cloud of gas and dust begins to clump together because
of gravitational attraction. Eventually, the core material heats up until it reaches a temperature of 15 million K. A stellar fusion reaction starts, and a star is born.
the explosion of a massive star whose core has completely burned out.
supernova
What determines the way a star dies?
How a star dies is determined
by the size of the star. Stars of masses similar to the Sun die by gradually shedding mass through stellar wind. Larger stars die in cataclysmic explosions called “supernovae.”
the imploded core of a massive star produced by a supernova explosion.
neutron star
How lighter and heavier elements are formed in stars.
Nuclear fusion reactions in stars produce heavier elements from lighter elements starting with
the fusion of hydrogen to form helium. Fusion reactions stop with the formation of iron. When the iron core of a star suddenly collapses, a supernova explosion creates a shock wave that blasts material into space and provides the energy needed to form elements heavier than iron.