Unit E Section 1.3 Flashcards
WHAT IS A STAR?
A star is a hot, glowing ball of gas (main hydrogen) that gives off tremendous light energy
What is the weight of the Sun compared to Earth?
Our Sun has a mass 300 000 times greater than Earth, with an average density of 1.4 times that of water.
What is the size and weight of the Betelgeuse compared to the sun?
In diameter, Betelgeuse is 670 times larger than our Sun but only 1/10-millionth as dense
What does the color of the star depend on?
The color of a star depends on its surface
temperature.
What do hot stars look like?
Very hot stars look blue
What do cooler stars look like?
Cooler stars look red.
What is the “Hertzsprung-Russell diagram”?
Shows the stars fall into several distinct groupings
Which star grouping does the sun belong to?
Main sequence
How much percent of stars fall into the main
sequence?
Ninety percent of
all stars fit into this grouping.
What do nebulae mean?
Stars form in regions of space where there are huge
accumulations of gas and dust called nebulae
What gases are nebulae formed of?
75% hydrogen
23% helium
The other 2% is oxygen, nitrogen,
carbon, and silicate dust
What is interstellar matter
is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays
What is protostar?
the first stage in a star’s formation
What is fusion?
This process, known as fusion, releases great quantities of energy and radiation.
What does the star depend on to figure out if it is a Sun-like or massive?
Depending on the mass of the star formed from a particular nebula,
What do Sun-like (in terms of mass) or massive spend most of their lives doing?
Both types of stars spend most of their lives in this main sequence, converting hydrogen to helium in their cores.
What makes the stars in a stable state?
The outward pressure of radiation on the stellar
material is counteracted by gravity
When does the stable state of the star shrink?
-When the hydrogen in the core has been used up, the stable state star shrinks in size, heating the helium core so that it first starts fusing to carbon, then to other elements
How does a star become a red giant or a red supergiant?
- After the stable state, when hydrogen is used up and turns into other elements,
- As gravity causes the star to contract, further nuclear reactions occur, leading to expansion of the outer layers.
What is the difference between a red giant and a red supergiant?
- red giant if it is a Sun-like star
- red supergiant if it is a massive star
When will our sun become a red giant?
- Our Sun will become a red giant in about 5 billion years.
- At that time, the Sun’s diameter may extend out past the present orbit of Mars.
When does the final stage in a star’s life occur?
when the fusion reaction stops
When does the fusion reaction end for a Sun-like star?
-fusion ends when the core temperature in the star is
no longer hot enough to keep the reaction going.
-With no heat input from fusion, the decreasing pressure is unable to prevent gravity from causing the star to collapse slowly on itself
What happens to a sun-like star after its last stage occurs as a giant red star
The Sun-like star continues to shrink, gradually becoming a WHITE DWARF, no larger than Earth
Eventually, the star will fade completely until it evolves into a cold, dark BLACK DWARF?
When does the fusion reaction stop in a massive star?
- when the star runs out of fuel.
- The lack of heat input into the core from fusion enables gravity to get the upper hand.
-Gravity causes the star’s core to collapse
rapidly on itself
- The collapse ends suddenly with an outgoing shock
wave. This, in turn, causes the outer part of the star to explode in a catastrophic event is known as a supernova
What is a supernova?
This, in turn, causes the outer part of the (massive) star to explode in a catastrophic event is known as a supernova
What happens if a massive star is not completely destroyed by the explosion?
the core is left as a neutron star or a black hole.
what is a neutron star?
A neutron star is a rapidly spinning object only about 30 km in diameter.
What is a black hole?
A black hole is a highly dense remnant of a star in which gravity is so strong that not even light from the radiation going on inside the remnant can escape.
Black holes are themselves invisible to telescopes. Astronomers only know about their existence indirectly because of how material near a black hole becomes very hot and bright.
Occasionally, massive stars collapse on themselves with such violence that they become super-dense. The gravity around these bodies is so intense that even light cannot escape being pulled inward. These bodies are called black holes.
Are humans stardust?
Humans are carbon-based life forms. The carbon making up our bodies was created inside ancient stars that exploded, distributing their elements in our region of the galaxy
What are Constellations?
are the groupings of stars we see as patterns in the night sky
How many Constellations are there?
88 constellations recognized by the International
Astronomical Union
What are asterisms?
many unofficially recognized star
groupings
What is one of the most famous asterisms visible
from the northern hemisphere?
the Big Dipper, which is part of the constellation Ursa Major.
-The ancient Greeks saw the stars that make up Ursa Major as a bear.
-The early Black Foot nation of North America also
saw a bear.
-Ancient Europeans saw a variety of different patterns
including a chariot, a wagon, and a plow
Orion Constellation/
The constellation of Orion, a figure in Greek mythology who was thought of as a great hunter
What is a galaxy?
A galaxy is a grouping of millions or billions of stars, gas, and dust. It is held together by gravity.
What is the galaxy we live in?
The galaxy we live in is a spiral galaxy called the Milky Way
It is shaped like a flattened pinwheel, with arms spiraling out from the center
What are the two other main types of galaxies?
elliptical and irregular
elliptical galaxy
An elliptical galaxy has a shape similar to that of a football or egg and is made up mostly of old stars.
irregular galaxy
An irregular galaxy has no notable shape and tends to be smaller than the other two galaxy types.
A mixture of old and young stars are found in irregular
galaxies.
