Transcript Astronomy Presentation

Astronomy
The study of the universe beyond the
Earth’s atmosphere
Theories of the Universe
• Geocentric
• Heliocentric
Theory: this
Theory: this
theory, put
theory, put
forward by the
forward by the
ancient Egyptian
Polish scientist
astronomer
Copernicus,
Ptolemy, states
states that the
that the Earth is
Sun is the
the center of the
center of the
universe.
universe.
Ptolemy and Geocentric Theory
Copernicus and Heliocentric Theory
What is the Solar System?
• The Solar
System is: the
Sun, the eight
planets and
their natural
satellites, the
asteroids, the
comets and the
meteoroids.
What is a planet?
• Planet = a
massive
collection of
matter that
revolves around
a celestial body,
or star.
The Eight Planets
•
•
•
•
•
•
•
•
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
– Pluto = dwarf
Planets are divided into two
categories
• Terrestrial Planets
are “land-based”
planets that are
solid, dense, “hot”
and have few
moons:
– Mercury
– Venus
– Earth
– Mars
– Pluto
• Gaseous Giants
are “gaseous”
planets that are
big, low density,
“cold” and have
many moons:
– Jupiter
– Saturn
– Uranus
– Neptune
Mercury
• Closest to the sun
• Thin atmosphere
• Day is 450 oC hot, night is -170
oC cold
• Has many craters
• Day is twice as long as its year
Venus
• 2nd planet from the Sun
• Hot 470 oC
• Has an atmosphere of poison
gas that causes sulfuric acid
rain
• Has storms
• Day is longer than the year
Earth
• 3rd planet from the Sun
• Only known planet with liquid
water
• Average temperature of ~ 12 oC
• Has one moon
• Has ice caps on the poles
Mars
• 4th from the sun
• Called the “Red Planet” due to large
amounts of iron oxide (rust) on
surface
• Also called the sister to earth
• Rocky composition
• Temperature range is -20 oC to -140 oC
• Has polar ice caps.
• 2 moons, Deimos and Phobos
Jupiter
• 5th from the sun
• Larger than all the other planets
combined
• High gravity makes the gas into a
liquid and therefore there are
“oceans”
• Great Red Spot is a storm on the
surface of the planet that is ~ 3
times the size of earth
• Jupiter has 63 moons.
Saturn
• 6th from the sun
• 2nd largest planet in solar
system
• Has a low density, it would float
in water
• Rings are made of particles of
ice, dust and rock
• Saturn has 60 moons.
Uranus
• 7th from the sun
• Planets axis is tilted on it’s side
• Green/blue color is from
methane gas, hydrogen and
helium composition
• Uranus has thin rings and 27
moons.
Neptune
•
•
•
•
8th from the sun
Blue color is from methane gas composition
Great Dark Spot is a storm on the surface
Neptune has 13 moons, moon Triton is
mostly nitrogen = possible atmosphere.
Pluto
•
•
•
•
9th from the Sun
Cold
Rocky composition
Pluto is considered a dwarf planet
– Pluto has one moon, Charon, almost as large as
Pluto itself
– Pluto and Charon together orbit the Sun in an
unusual path
Other Dwarf Planets
•
•
•
•
Ceres
Haumea
Makemake
Eris
Planetary Paths - Orbits
• Planets travel around the sun in a path called
an orbit.
• Planetary orbits are elliptical in shape.
• Elliptical orbits are compared based on how
eccentric, or out of round, they are.
• A perfect circle has an eccentricity of 0 (no
out of round shape) and a line has an
eccentricity of 1 (maximum out of round)
Planetary Orbits
Orbits
• All the planets revolve around the
sun in a counter-clockwise motion.
• The planets are held in place by the
gravitational force of the Sun.
• Planets move fastest through their
orbit when they are closest to the
sun.
What is our Sun?
• Our Sun is an average star of
yellow-orange classification.
Layers of the Sun
• The sun is
composed of
several
layers.
–
–
–
–
–
–
Core
Radiative zone
Convective zone
Corona
Photosphere
Chromosphere
The Core
• The core of the Sun is the place
where fusion of atoms is taking
place.
– Fusion generates temperatures of
10,000,000 oC
– Our sun is fusing hydrogen atoms
into helium
The Corona
• Corona = the outer layer
of the sun. This is the
gradual boundary
between the sun and
space. This is what we
see during an eclipse.
The Photosphere
• Photosphere = the layer
of the sun that is
incredibly bright and the
source of much of the
light we see on earth.
The Chromosphere
• Chromosphere = is an
active layer of the sun
that is where the
magnificent displays of
prominence and flares
take place.
Prominence / Solar Flares
• Prominence / Flares are bright
spots on the sun formed as gas
particles shoot outward from
the sun.
– These affect the magnetic fields
on earth (radio, television,
communications).
– These also cause the Northern
Lights or “Aurora Borealis”.
Aurora Borealis – “Northern Lights”
Northern Lights
Sun spots
• Sun spot = a dark, cooler spot
on the surface of the sun.
What are Stars?
• Star = a hot, glowing sphere of
gas that produces energy by
fusion (of hydrogen molecules).
–Some stars produce more
energy therefore they are
hotter.
How Do Stars Form?
• Nebula = a cloud of dust and
gas where stars are born.
–Here gravity pulls particles
together and fusion starts at
10,000,000 oC and a star is born.
The Horse Head Nebula
More Horse Head Nebula Shots
How Are Stars Classified?
• Stars are classified by:
–Temperature
–Color
–Brightness
Stars are Classified by Temperature
and Color.
• HOT
BLUE
COLD
WHITE
YELLOW ORANGE
RED
BROWN
What is a Main Sequence Star?
Stars are Classified by Brightness
• Actual brightness
is how bright a star
really is.
• Actual brightness
does not change, it
is an absolute
value.
• Example: a 40
watt light bulb is
actually converting
40 watts of energy
into light.
• Apparent brightness
is how bright a star
looks from earth.
• Apparent brightness
changes depending
on distance from
earth and viewing
conditions
(atmosphere).
• Example: a 40 watt
light bulb 10 feet
away appears
brighter than a 40
watt bulb 100 feet
away.
…And After Stars are Born?
Life Cycle of a Star
What is a Supernova?
• Supernova is when the core of a star
collapses and the outer portion
explodes.
– This is the “death of a star”.
• What remains when a star dies out
depends on the mass of the star.
– The most massive stars collapse into
black holes.
What is a Black Hole?
• Black Hole = the most dense thing
known to exist in the universe. The
gravity of a black hole is so great
that even light can not escape the
pull of a black hole.
The massive
density of
Black Holes
creates a
gravitational
force that
pulls in
anything that
comes within
reach: the
reach of this
force is
called the
event
horizon.
The fate of
objects that
enter a
Black Hole
is still
uncertain.
?
Other Objects in the Solar System
• Other objects in the solar
system include:
– Comets
– Asteroids
– Meteoroids
What is a Comet?
• A Comet is a
large chunk of
ice, dust,
frozen gas and
rock fragments
that moves
through space.
Comets form in an icy cloud, called the Oort Cloud, as the
gravity of a passing star pulls material out of the cloud.
Comets Have Two Tails
The Ion Tail
always
points away
from the sun
The Dust
Tail is left
behind in
the comets
path
Halley’s Comet
Comet - Liner
Asteroids
• Asteroid = a large chunk of rock
traveling through space.
– Most, not all, are found in the asteroid
belt located between Mars and Jupiter.
Asteroid approaching Earth
Asteroid Impact
Meteoroid, Meteor, Meteorite
• Meteoroids = small pieces of rock
moving through space.
• Meteors = small pieces of rock
moving through space (a meteoroid)
that enters Earth’s atmosphere.
• Meteorite = a small piece of rock
moving through space that hits the
Earth.
Perseid Meteor Shower
How are Distances
Measured in Space?
• Astronomical Unit
(AU) is the
distance from the
Earth to the Sun.
1 AU = ~92,000,000
miles
• Light Year (LY) is
the distance that
light travels in
one year.
1 LY = ~6 trillion
miles
Light Year = Distance
1 light-second
1 light-minute
1 light-hour
1 light-day
1 light-week
1 light-month
1 light-year
= 0.0020 AU
= 0.1202 AU
= 7.2143 AU
= 173.14 AU
= 1212.0 AU
= 5194.3 AU
= 63240.2 AU
= 186,322 miles
= 11.18 mil. miles
= 670.76 million miles
= 16.098 billion miles
= 112.69 billion miles
= 482.95 billion miles
= 5.89 trillion miles
OBJECT
Our
Planets
in Light
Years
Light-travel Distance
Mercury
3.22 light-minutes
Venus
6.01 light-minutes
Earth
8.32 light-minutes
Mars
12.7 light-minutes
Jupiter
43.3 light-minutes
Saturn
1.32 light-hours
Uranus
2.66 light-hours
Neptune
4.16 light-hours
Farthest comets
1.58 light-years
Proxima Centauri
4.3 light-years
Orion Nebula
1,500 light-years
Center of Milky Way
26,000 light-years
Andromeda Galaxy
2.36 million light-years
What is a Galaxy?
• Galaxy = a large group of stars, gas
and dust held together by gravity.
Three Types of Galaxies
Elliptical Galaxy
Spiral Galaxy
Irregular Galaxy
Elliptical Galaxies
• Elliptical galaxies = are groups of
stars that appear to be shaped like
an ellipse (football)
Irregular Galaxies
• Irregular galaxies = are groups of
stars that appear to be together but
have no regular shape.
Irregular Galaxy
Spiral Galaxies
• Spiral galaxies = are groups of stars
that appear to have a dense
concentration of stars in the center
and arms that are made of stars and
dust.
Barred Spiral Galaxy
– A “Barred” Spiral galaxy looks similar to
a spiral galaxy with a “bar” of stars
through the center and the arms extend
outward from the ends of the “bar”.
Clusters
• As stars are grouped into
galaxies, galaxies are grouped
into clusters.
• Our cluster is called the “Local
Group”
So Where in the Universe Are We?
• The astronomical address for
Earth would be:
– Earth is the 3rd planet in the solar
system of the star called the Sun,
which is in the Milky Way Galaxy,
of the Local Group of galaxies in
the Universe.