Ch. 30. 1 - Characteristics of Stars
Name 3 stars that are hotter than our sun.
1 - Rigel, 2 - Sirius, 3 - Procyon
What 2 factors does APPARENT magnitude depend on?
1 - how much light the star emits 2 - how far the star is from Earth
What is a circumpolar star? How could you tell by observation whether a star is a circumpolar star?
A circumpolar star is a star that never passes below the horizon as viewed from a certain place. To determine whether a star is a circumpolar star, you could observe it over the course of a year to see whether it ever dips below the horizon.
Why do stars appear in different parts of the sky during different months?
As Earth orbits the sun, different stars are visible at different times.
What causes the apparent motion of stars?
Earth's moon
The closest star to Earth, apart from the sun, is Proxima Centauri. Proxima Centauri is about 4.2 light-years from Earth. How long does it take light from our sun to reach Proxima Centauri? About how many kilometers is Proxima Centauri from Earth?
It takes about 4.2 years for light from our sun to reach Proxima Centauri. Proxima Centauri is about 4.2 × 9.46 trillion = 39.7 trillion kilometers away.
A star is made mainly of hydrogen and helium. Name 1 difference between a star's composition and Earth's composition.
Oxygen is the most common element on Earth.
How do scientists use a star's spectrum to determine the star's composition?
Scientists analyze the colors missing from the spectrum, which indicate the elements in the star.
How do scientists determine the temperature of a star?
Scientists use the color of a star to determine its temperature. For example, blue stars are hotter than yellow stars.
Star A and star B are the same distance from Earth. Star A's apparent magnitude is 10. Star B's apparent magnitude is 15. Which star has the larger absolute magnitude?
Star B has the larger absolute magnitude. Apparent magnitude depends on the amount of light a star emits and how far away it is. If both stars are the same distance away, the difference in their apparent magnitude must be caused by differences in how much light they emit, or their absolute magnitude.
How can a star that has more mass than our sun be smaller than our sun?
The star could be denser than our sun.
Suppose distant galaxies had blueshifted spectra instead of red-shifted spectra. What could astronomers conclude about the motions of these galaxies?
They could conclude that the galaxies are moving toward Earth.
star
a large celestial body that is composed of gas and that emits light
What is a spectrograph?
a tool that separates light into different colors
How many kilometers are in one light-year?
about 9.46 trillion
parallax
an apparent shift in the position of an object when viewed from different locations
Doppler effect
an observed change in the frequency of a wave when the source or observer is MOVING
Which star would show a larger parallax shift —one that is 4 light-years from Earth or one that is 6 light-years from Earth?
one that is 4 light-years from Earth
apparent magnitude
the brightness of a star as seen from the Earth
absolute magnitude
the brightness that a star would have at a distance of 32.6 light-years from Earth
light-year
the distance that light travels in one year
