Transcript a 03 Scale and Comparing Planets to Stars ppt

Part 1: Distances in Space
And
Part 2: Comparing Planets to
the Stars
(4.13A-01a)
Interplanetary Distances
• Compared to how far away the stars are,
separation of the planets is a relatively
small distance.
• Examples: Distance from Earth to the
Sun ~150 000 000 km and the distance
between Earth and Mars is 75 000 000
km.
• Units of Distance used to describe the
distance between planets is Kilometers
• Kilometers are of limited use because distances
in space are very large and we usually must
express the number of kilometers in scientific
notation.
e.g. the average distance from Earth to the Sun is
150 000 000km, but we write it 1.5x108km
Bill Nye distances between planets (4:17 min): http://www.youtube.com/watch?v=97Ob0xR0Ut8
Bill Nye distances between planets soccer field (2:07 min): http://www.youtube.com/watch?v=BdAqq-wEQV0&feature=related
Astronomical Units
• Useful measurement units because,
1. They allow comparisons and the use of smaller numbers.
2. Compares distances to a common known distance (the
distance from the Earth to the Sun).
ACK! That Brain
has a
comparative size
of 3.5 H.B.’s
Comparing is easy. My brain is 3.5
times the size of HUMAN BRAINS
•
•
•
•
1 astronomical unit = 1 a.u.
1a.u. = average distance between Earth and Sun
Earth is 150 000 000 km, or 1 a.u. away from the Sun.
Mars is 230 000 000 km, from the sun, or approximately 1.5
a.u. from the Sun. So Mars is 1.5 times as far from the sun as
Earth is from the sun.
Why use the sun as a reference
point?
Interstellar Distances
• Interstellar distances are relatively very,
VERY large distances.
• Examples: Distance between Earth and
Alpha Centauri (the next closest star) is
3.8x1013 km [or 38 000 000 000 000 km]
• Units of Distance used to measure the
distance from Earth to a star or galaxy are
LIGHT YEARS
• 1 light year is the distance that light
can travel in 1 year, at its speed of
300 000 km/s
• 1 light year = 9.5x1012 km
How far can a photon (light particle)
travel in 1 year?!?
1 Light year
!!!
b
• Example: The nearest star (other than
the Sun) to us is Alpha Centauri. Alpha
Centauri is 4.3 light years away or
4.3x9.5x1012 km = 3.8x1013 km away
from earth.
• This means that the light that we see
from Alpha Centauri left that star 4.3
years ago.
Is that like
looking into the
past?
2.2 million light
years
Light years are
large, and there
are no
washroom stops
between
galaxies.
• The Andromeda Galaxy is 2.2 million light years away from
Earth.
• This Means that the light we see from Andromeda Galaxy left
there 2.2 million years ago.
• It is therefore very possible that some of the stars in
Andromeda have exploded as a supernova or gone out long
ago. The message of these star finishing events just has not
gotten to us yet!
Part 2: Comparing Planets and
Stars
Features
Planet
Star
Location
In our solar system.
Beyond our solar system. The
Sun is the closest one.
Distance from the Earth
Closer than the sun or other
stars.
Generally VERY VERY far
away, (light years away) except
for the Sun.
Real Size
Varies, but much smaller than
a star.
VERY VERY large compared to
planets
Reason we are able to
see it
Reflect the sun’s light and are
called “Non-Luminous” (not
light giving)
Gives off own light and are
called “Luminous” (light giving)
Surface Temperature
Varies, depending on
closeness to sun and insulation
effects of atmosphere.
Some are rock (e.g. Earth,
Mars)
What are they made of?
Extremely Hot
The Sun is ~5500oC
Gases … that are going
through nuclear reactions.
Some are gas (e.g. Jupiter)
Observable Features
Don’t “Twinkle” – give off
steady light.
“Twinkle”
Long Term Observable
Features
Slowly appear to move through
constellations.
Varies, but our Sun has
extreme solar flares every
11yrs.
Reviewing Lights in the Sky
• In our own solar system we see 8 other
planets, some of their moons and our own
local star (Sol), which the solar system is
named after.
• We can see nearby planets because they
reflect the light produced by our sun.
Luminous: stars are called luminous because
they make the light that illuminates space.
Non-luminous: Objects like Planets are
called non-luminous because they do not
make their own light but only reflect the light of
stars.