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The Life and Death of Stars (20.1) Notes
What are
Stars are huge spheres of very hot __________ that emit light and other radiation. The nearest star to the
Stars?
Earth is the ___________.
The Greeks grouped stars into shapes and patterns called ___________________________.
We use the unit _____________________ (ly) to describe a star’s distance from Earth. One light-year is
the distance that light travels in one year which is ______________________m.
A star is held together the enormous gravitational forces that result from its own ___________.
Nuclear ________________ takes place in the hot, dense core. Fusion combines the nuclei of
____________________ atoms into __________________. When two particles fuse, _______________
is released.
Energy moves through the layers of a star by a combination of radiation and ____________________.
The energy from nuclear fusion reaction may take ____________ of years to work its way through the
star. When the energy finally reaches the surface, it is released into space as ________________ and
_____________.
Once energy leaves the surface of a star, it radiates across space at the speed of light,
_______________m/s. At this speed it takes light from the sun about ____________ minutes to reach
Earth.
The brightness of a star depends on the star’s ___________________________, ____________, and
Studying
________________________ from Earth. The brightest star in the night sky is __________________.
Stars
A star’s color is related to its ______________________. Hotter objects glow with light that is more
intense and that has shorter wavelengths (closer to the __________ end of the spectrum), while light
from cooler objects have longer wavelengths ( closer to __________).
Spectral lines reveal the ______________________ of stars.
The Fate of
Stars are born, go through different ____________ of development, and eventually die. Nearly ____% of
Stars
all stars in our galaxy, including the sun, are in _____________, still converting hydrogen to helium in
their interiors.
Stars form from a cloud of gas and dust called a ___________________. The cloud collapses inward,
pulled by its own ______________. It then begins to _____________ faster and faster. As the center of
the cloud becomes hotter, the process of nuclear ______________ begins in the core of the cloud, and it
“turns” on.
The fusion reactions in the core of our sun produce an _______________ force that balances the
____________ force due to gravity. Eventually the core will run out of ____________________, and the
fusion reactions that turn hydrogen into helium will __________ ______________ , and the sun will
begin to _________.
As fusion slows, the pressure in the core will drop and the core will contract, temperatures will rise, and
the outer layers will _________________ becoming a _________ ________________. The star is red
because it is _____________, but the core is still hot enough to convert helium into
__________________ and ___________________.
After the core runs out of helium, the outer layers will expand further until they eventually _________
the star. The remnant will become a ________________ ________________, a small very dense star
about the size of _____________.
More massive stars die when their cores become mostly ____________. The core collapses because of its
own gravity and rebounds with a shock wave that violently blows the stars outer layers from the core.
This huge, bright explosion is called a Type II _________________________.
If the core that remains after a supernova has a mass of 1.4 – 3 solar masses it becomes a
_______________ star, a very dense star that is a source of pulsating radio waves called _____________.
If the left over core has a mass greater than 3 solar masses, it will collapse to form a __________
__________, which consists of matter so massive and compressed that nothing, not even light, can
escape its ___________________.
The H-R diagram organizes stars by their _________________ (absolute magnitude) and
____________________. Because most stars spend most of their lives in midlife, more stars appear on
the __________ ________________ than any other parts of the H-R diagram.