Download Notes: Astronomy and Groups of Stars

Notes: ASTRONOMY ( pp .775-780)
- The study of everything in the universe that can be observed from earth or in space.
UNIVERSE
Everything that exists ( its’s estimated to be 14 byo)
its’ building blocks are the GALAXIES
3 types are spiral, elliptical & irregular
groups of STARS
glowing ball of GAS
gives off ENERGY in the form of RADIATION
HYDROGEN & HELIUM
(Process called Nuclear Fusion)
Wavelengths arranged in the
ELECTROMAGNETIC SPECTRUM
4H=1 HE + energy
Some wavelengths are invisible & others are VISIBLE LIGHT
made of colors ROY G BIV
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STARS
Are different distances from earth measured in units called LIGHT YEARS
the distance that light travels in a year ( 5.8 trillion mi).
*distance= time traveled x 5.8 trillon mi ( or 9.46 trillion km) *
Closest star to earth is the sun….next closest is Alpha Centauri , 4.22 light years away.
Characteristics of stars:
a. Brightness (magnitude)- created by glowing gases.
The energy that heats the gases is made from the NUCLEAR FUSION of 4
hydrogen atoms to form 1 helium atom. The helium has less matter than the 4
hydrogen, so the left over matter becomes HEAT ENERGY—makes stars glow
** types of brightness= apparent magnitude & absolute magnitude.
b. Temperature- The color tells the surface temperature of the star.
red=coolest
y-o= medium hot
blu-whi= hot
blue= hottest
The core of stars is very hot. The temperatures observed are of the outer layer of the star.
c. Composition- All have nearly identical composition to Earth.
73 % of the stars mass is hydrogen, 25 % is helium & 2% other elements
d. Mass/Size- Determined by comparing it to the sun-----Giant, Dwarf and Medium.
Most are medium sized like the sun. Fusion occurs more rapidly in larger stars.
Some stars are small & dense or large & less dense.
Life Cycle of a Star ( pp.781-788)
(Stellar Evolution)
NEBULA
star not hot enough
to shine. Nuclear fusion
begins & temperature
increase in core
huge cloud of dust & gas that
clump together due to gravity young
PROTOSTAR
MAIN SEQUENCE
TRUE STAR
middle-aged star-temperature & brightness are
constant for billions of yrs.
Hydrogen is slowly used up. GIANT (red)
Star begins to die. Shell expands
as energy from the core radiates
outward. It grows cooler as it expands.
Star is bright
(LOW MASS)
(MASSIVE)
WHITE DWARF
As the outer gases disperse, the core
collapses inward. The hot small core
remains & takes billion of years to
completely cool off.
SUPERGIANT
A red giant that keeps expanding
Star is very bright and very cool
SUPERNOVA
Explosion of a star due to the
release of energy and great inner core
temperature & pressure
BLACK DWARF
Star no longer giving off light
A dead star
NEUTRON STAR
High densely packed star made
from supernova neutrons.
Very small & rotates rapidly
BLACK HOLE
large amount of mass
concentrated in a single
spot . The gravity is so
great making it so dense
that not even light can
pass thru it.
GROUPS OF STARS (pp.790-792)
Binary stars
Stars that are in pairs.
Revolve around each other
Held together by gravity
Star Clusters
A group of hundreds or thousands of
stars.
Globular and Open
Galaxy
A system of billions of stars, gas &
dust held together by gravity.
Major building blocks of the Universe.
Universe has 100’s of billion of galaxies
------3 types based on shape:
a. elliptical b. irregular-
c. spiral Ex. Milky Way Galaxy.
Constellations (p.669 &789)
Oval shaped, Extremely bright,
Older stars
No regular shape, Very low mass
Made of gas and dust, Least common
Looks like a wheel with arm extensions
Most common type
Arms consist of younger stars, gas/dust.
- our galaxy
-100’s of billions of stars
- it takes 100,000 light years to
travel across our galaxy
- our galaxy revolves slowly
(225 million years) as the stars orbit
the center of the galaxy.
- galaxies are also in clusters.
Our cluster is called the Local Group
(30 galaxies)
patterns or picture of stars not bound by
gravity.
88 constellations
specific one’s are only seen during
specific times of the year due to the
earth’s revolution changing our view of
the night sky.
OUR STAR: THE SUN
- huge glowing gaseous ball found in the Milky Way galaxy.
- closest star to earth- 93 million miles away
- medium -sized single star.
- revolves once every 250 million years.
- rotates every 27 days
- sun’s surface is constantly in motion due to convection currents.
- made of hydrogen & helium.
- energy made by nuclear fusion
- energy produced is radiation in the form of visible light.
- formed 4.6 billion years ago
- will live for a total of 10 billion years
- it takes energy 8.5 minutes to travel to Earth.
- 1 million Earth’s can fit inside the sun.