1. Characteristics of Stars
Constellations – imaginary
patterns of stars
Circumpolar – five constellations
in the Northern Hemisphere that
circle the pole star (Polaris)
Classification of Stars
Stars are classified by their color,
temperature, size, brightness, and
composition
2. Brightness depends on size and temperature and
there are two types
• Apparent – brightness as seen from Earth
• Absolute – brightness the star would have if it were at
a standard distance from Earth
Composition is determined by a spectrograph – a
device that breaks light into colors and produces an
image of the resulting spectrum
Measuring Distance
Astronomers use light years – the
distance that light travels in one
year, about 9.5 million million
kilometers
Astronomers use parallax – the
apparent change in position of an
object when you look at it from
different places
3. Hertzsprung-Russell
(HR) Diagram
– graph used to determine
a stars classification
– it helps identify stars by
color, size, temperature
and brightness.
– about 90% of stars fall on
the main sequence.
– the other 10% of stars
were once main
sequence stars.
– can help determine
where a star is in its
lifecycle
