Download Stars Power Point

WHAT ARE STARS?
•Huge, hot balls of gas
that are trillions of
kilometers away from
the Earth.
• Astronomers study the COLOR of star
light
• Which color is the hottest?
• Red and yellow – cool
• Blue - hot
• Spectrum – when you look at white light
through a glass prism – see a rainbow of
colors (ROYGBIV)
• Continuous Spectrum – shows all the
colors – a hot, solid object, such as the
glowing wire inside a light bulb
• A Spectrograph is used to break a
star’s light into a spectrum
• This gives information about
COMPOSITION and TEMPERATURE of
a star
• For example – when look at a neon
sign WOULD NOT see a continuous
spectrum but would see EMISSION
LINES
• Emission Lines are lines made when
certain wave lengths of light or
COLORS are given off by hot gases
• Bright Line (Emission)-A spectrum
consisting of individual lines at
unique spots.
CONTINUOUS SPECTRUM
BRIGHT EMISSION LINES
• Each element has a unique set of
bright emission lines.
• A Star’s Spectrum is made up of DARK
EMISSION LINES
Absorption
DARK EMISSION
LINES
• A star’s atmosphere absorbs certain
colors of light in the spectrum, which
causes black lines to appear!
• ABSORPTION SPECTRUM - a star’s
atmosphere absorbs colors of light
instead of emitting them
• An absorption spectrum is
produced when light from a hot
solid or dense gas passes
through a cooler gas.
• Absorption spectrum of a star –
inside is hotter than it’s
atmosphere
• Black lines in a spectrum
represent where less light gets
through
• What is this star made of?
Hydrogen
Helium
• Stars are classified by HOW
HOT THEY ARE!
• Temperature differences
between stars result in
COLOR DIFFERENCES
• Hottest stars are BLUE
• TYPES OF STARS
Temperature & Color
• Stars can be different colors
• Reddish stars are coolest
(<4000°C)
• Orange/Yellow stars are medium
(4000°-7000°C)
• White & Blue stars are hottest
(7000°-30,000°C)
•
•
•
•
Brightest stars – 1st MAGNITUDE STARS
Dimmest stars – 6th MAGNITUDE STARS
Positive numbers – dimmer stars
Negative numbers – brighter stars
Apparent Magnitude
• How bright stars look when
they’re viewed from Earth
• Low numbers are brightest, high
are dimmest
• Sun = -26.7
• Sirius = -1.45 (Brightest Star)
Absolute Magnitude
• The ACTUAL BRIGHTNESS OF
A STAR
• If all stars were the same
distance away, their absolute
magnitudes would be the same
as their apparent magnitudes.
Absolute Magnitude
• The brightness that a star would
have at a distance of 32.6 light
years from Earth
• Sun = +4.8 (ordinary for a star)
• Due to closeness to Earth Sun’s
apparent magnitude is -26.8
DISTANCE IN SPACE
1. LIGHT YEARS – distance that
light travels in one year – 9.5
trillion kilometers (light moves
300,000 Km/sec)
2. PARALLAX – an apparent shift in
the position of an object when
viewed from different directions
• Notice that the location of the middle
star seems to shift in relation to more
distant stars – seen through telescopes
• Daytime and nighttime are caused by the
Earth’s rotation
• The apparent motion of the sun and
stars in our sky is due too the EARTH’S
ROTATION
• The Earth’s tilt and revolution
around the sun cause the seasons.
• During each season the Earth faces
a different part of the sky at night.
• All stars that we see appear to
rotate around POLARIS (the North
Star)
• Due to the Earth’s rotation all of the
stars in the sky appear to make one
complete circle around Polaris every
24 hours.