Kinds of Stars
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Transcript Kinds of Stars
Stars & Galaxies
Chapter 21
Stars & Their
Characteristics
Constellation – Group of stars that appears
to form a pattern. 88 recognized by
science.
Ursa Major – “Big Bear”, “Big Dipper”
Ursa Minor - “Little Bear”, “Little Dipper”
Cassiopeia – Lopsided “M”, Queen’s Chair
Circumpolar Constellations – Constellations
that appear to move around the North Star.
Stars & Their
Characteristics
Polaris – “North Star”
Apparent movement of circumpolars
caused by rotation on axis.
Seasonal Constellations –
– Summer Triangle
– Orion
Constellations lost in sunlight at
different times of the year.
Stars & Their
Characteristics
Summer Triangle – 3 Stars
– VEGA in the constellation Lyra (The Harp)
– Altair in the constellation Aquila (The Eagle)
– Deneb in the constellation Cygnus (The Swan)
Deneb at the top of the “Northern Cross”.
Orion – “The Hunter” Winter Constellation
– BETELGEUSE & RIGEL
– Belt stars help locate two other constellations.
Stars & Their
Characteristics
Left of belt is SIRIUS of the constellation
Canis Major.
– SIRIUS-Brightest star in the nighttime sky.
Right of belt is Taurus the Bull, Pleides.
Distances to Stars
– Astronomical Unit (AU)- Average distance from
our sun to the Earth.
150 Million Kilometers
Alpha Centauri next nearest star to us. 300,000 x as
far from Earth as we are from the sun.
Stars & Their
Characteristics
Stars – Most are different in density.
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Less different by mass.
Color of star depends on surface temperature.
Hot stars are Blue, Cooler stars are Red.
Made mainly of Hydrogen and Helium.
Our sun is 70 % Hydrogen/ 28 % Helium.
Each star has its own spectrum. (Fingerprint)
Stars & Their
Characteristics
Brightness –
– Apparent Magnitude – How bright a star
appears from the Earth’s surface.
Kinds of Stars
Red Giants - ALDEBARAN, ARCTURUS
Blue-white- hot, SIRIUS, VEGA
SUPERGiants- More luminous, greater in
size. Include blue-white RIGEL, Whiteyellow CANOPUS, red SuperGiants
ANTARES & BETELGUESE.
REDSUPERGIANTS- Largest of all stars
Kinds of Stars
Dwarf stars – Absolute magnitude of less
than 1.
Most either red, orange, or yellow.
White dwarfs – very faint, small, dense.
Variable stars – Shine with different
brightness over several day periods.
Pulsating Stars- Change brightness, expand
& contract. Example is Cepheid Variables.
Kinds of Stars
Eclipsing Binaries- When one star rotates
around another brighter star. The stars look
like 1 star that changes brightness.
Pulsars- 1967 Jocelyn Bell-Burnell. Crab
Nebula discovered. Both radio waves and
light came from a star in this nebula. Pulse
due to rapid rotation of star.
Formation of Stars
Nebulae – Clouds of dust or gas in space.
Nebula dust seen by 2 methods:
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1. Light from nearby star is reflected off dust.
Example is a DIFFUSE NEBULA
Brightest known is in constellation ORION.
2. Nebulae clouds contact each other and glow.
These are called PROTOSTARS.
– Dark Nebulae- Away from stars. “HorseHead”
Formation of Stars
Gas and Dust in space are called Nebulae.
Stable State – Stars whose diameter and
radiation stay the same for millions of years.
Our sun is in a stable state.
When fusion doesn’t balance gravity’s force,
core contracts(gets hotter) and outer layers
expand.
Star is bigger, brighter, more surface area.
Formation of Stars
Dwarfs – Core temperature and pressure
not enough to support outer layer(s) weight.
Star collapses and becomes very dense.
Occasional flare ups called “NOVAS”
NOVA – “new star”
Our sun – Stable now, will become Red
Giant, fade to White Dwarf.
Formation of Stars
SUPERNOVA – 1054 Chinese observed
one. It’s remaining dust cloud “Crab
Nebula” found in Taurus the Bull.
Best known modern SuperNova appeared in
1987. (Page 387 text) Figure 21.10
NEUTRON STAR – Mass that remains after
an exploded SuperNova.
Formation of Stars
BLACKHOLES - Object of space with
high gravitational pull. Light cannot
escape.
Atoms are ripped apart before entering
a Blackhole. These atoms emit XRays that are detected by radio
telescopes.
Galaxies and the
Universe
Most galaxies are millions of light years
away.
Our sun is one star of 100 billion in the
MILKY WAY Galaxy.
Milky Way – 140,000 LY long, 20,000 LY
thick. Sun is 23,000 LY from its center.
Local Group – Small cluster of 17 galaxies.
Galaxies and the
Universe
Nearest galaxy is the ANDROMEDA Galaxy
at 2 million LYs away.
Galaxy Types:
Spiral – Bright center, usually two arms that
hold majority of its stars. ( ¾ of galaxies)
Elliptical – spherical shape, most stars in the
center. No arms, gas, or dust.
Irregular- No set shape, least common.
Galaxies and the
Universe
QUASARS – Discovered in 1961
– Very far away
– Calculated to be the most luminous
objects in space.
– Larger & more massive than stars.
– High radiation emission.
Science Background
Polaris is a cepheid variable with a
period of just 4 days. Its magnitude is
only 2.5 to 2.6. Polaris is a double
star. Its companion has a magnitude
of 8.8.
Scientists compare a Cepheid’s
absolute and apparent magnitudes to
determine its distance from Earth.
Science Background
Proxima Centauri – Closest star to
Earth. Its magnitude of 11 is no visible
to unaided eye.
Alpha Centauri – Closest VISIBLE star
to Earth with the unaided eye.
Both Centauri stars can only be seen
at locations within 30 degrees of the
south pole.
Ch 21Vocabulary Words
Absolute magnitude - The brightness of a star
compared to other stars if they were compared at the
same distance.
Constellation – A group of stars that appear to
form a pattern.
Apparent magnitude – The brightness of a star as it
appears from Earth.
Dwarf Stars – Stars that have gone to the unstable
state. The inner core collapses and the star is very
dense.
Astronomical Unit (AU) – The average distance
between the sun and the Earth. 150 million kilometers.
Eclipsing Binary – Two stars that are in rotation
around each other. One is brighter than the other.
Looks like 1 star.
Big Bang Hypothesis – Theory of how the universe
first started.
Galaxies – Collections of billions of stars. Three
types include spiral,elliptical, and irregular. Local
Group
Luminosity- The actual brightness of a star as it
appears from just outside of the Earth’s atmosphere.
Light-year – The distance light travels in one year.
9. 5 trillion kilometers. (300,000 kilometers per
second)
Nebulae – A collection of space dust and gas. This is
the ingredients for starting a new planet.
Protostar – When two nebulae clouds rub together
and cause a glow.
Neutron star – The mass that remains after a star
goes supernova.
Pulsar – Stars that emitt radio waves that are in
time with the visible light waves that it also emitts.
“Crab Nebulae”
Nova – “New Star”
Quasars – The most luminous objects in space.
Very large. Very, very far away. Bigger than super
giant stars.
Black holes – Invisible objects in space that have a
gravitational pull so strong that no EM energy can
escape.
Red Giants – Highly luminous stars that are
considered to be “warm” compared to other stars.
Aldebaran Arcturus
Cepheid Variables – Yellow super giant stars that
Super Giants – Hundreds of times brighter than