Transcript Ch. 26 The Sun and the Solar System

Ch. 26
The Sun and the Solar System
The Sun’s Size, Heat, and Structure
• Fusion: The process by which stars get their
energy. Consists of the combining of 4 hydrogen
nuclei into helium
• When the nuclei fuse, some of their mass is
converted into energy. The mass of the particles
involved in the reaction at the start of the
reaction is greater than the mass of the particles
at the end. The missing mass is converted into
energy. The amount of energy produced varies
depending on the kinds of elements involved in
the fusion reaction E=mc2
• Layers of The Sun
– Core – Radiative Zone – Convection Zone –
Photosphere – Chromosphere
Core: consists of helium and hydrogen atoms in the
plasma state (100 times more dense than water)
15,600,000 C
Radiative Zone: plasma; cooler than the core; 8,000,000
C to 2,000,000 C from deep to shallow
Convection Zone: made up of rising and falling currents
of plasma carrying energy to the Sun’s surface where it
gets radiated into space as sunlight
Photosphere: The visable surface of the sun.
Around 6,000 C
Chromosphere: The inner layer of the Sun’s
atmosphere. 20,000 C extending thousands of Km
above the photosphere. Distinctive reddish color
due to hydrogen emitting light due to the intense
temperature
Prominences = dense clouds of material
suspended above the Sun’s surface by magnetic
fields
• Corona: The thin outer atmosphere of the
Sun. Millions of times less bright than the
photosphere. Temps of 1,000,000 to
3,000,000 C
Venus in front of Sun
• 1 A.U. (astronomical Unit) = 150,000,000 Km
– The distance from the Sun to the Earth
• Features of the Sun:
– Sunspots: Dark spots on the photosphere. Cooler
areas than the surrounding photosphere. Very strong
magnetic fields (1000 times stronger than that of the
surrounding photosphere)
Move from left to right across the Sun’s
surface (first indication that the Sun rotates on an axis
much like Earth)
Sunspot activity cycles on an average of 11 yrs
between peak activity and are associated with increase
solar flare activity (large explosions of light on the Sun)
and cause disruptions of radio, tv, cell phone, satellite
activity
• Solar Wind: The constant stream of electrically
charged particles given off from the Sun’s
Corona (450 km/Sec) so they reach Earth in a
few days
– Earth is protected from this by our magnetic field
but the interraction of the Solar Wind and the
Earth’s magnetic field create the Auroras
(Northern/Southern Lights)
Section 2
History of solar System Study
• Geocentric Models: Earth is the center of the
Solar System. The stars were holes in a solid
celestial sphere that surrounded the Earth.
Beyond the sphere was a source of intense light.
The belief was then that the sphere rotated with
certain patterns coming around at the same time
each year
• Retrograde Motion: The apparent “backwards”
movement of a planet due to the Earth catching
and passing that planet in its orbit around the
Sun
Ptolemy’s Geocentric Model
• Ptolemy: Greek astronomer (2nd century AD)
lived in Egypt
– Developed the first model that could predict the
position of planets that help until the 16th century
• Epicycles: Small circular orbits that the planets
moved upon
• Deferent: The orbit followed by the center of
each smaller orbit
Copernicus’s Heliocentric Model
• Nicolaus Copernicus: Polish astronomer (14731543)
• Heliocentric model: Model where the Sun is
the center of the Solar System and the Earth is
a planet that moves around it.
• Retrograde is caused by planets following a
counterclockwise orbit at different distances
from the Sun and at different speeds
Tycho, Kepler Planetary Motion
• Tycho Brahe:Danish astronomer (16th Century)
– Followed the motion of planets, and the Moon
throughout its orbit and not just at particular
times. He had the most precise records from
before the invention of the telescope
Johannes Kepler: Tycho’s assistant. Discovered that
planet’s orbits were elliptical rather than circular
• Created 3 Laws of Planetary Motion:
•
1. Planets travel in elliptical orbits around the Sun
with two foci or focus on each side of the center of its
path. Since there are two foci, its distance from the
Sun will change throughout its orbit
•
2. The Equal Area Law: Each planet moves around
the Sun in such a way that an imaginary line joining the
planet to the Sun sweeps over equal areas of space in
equal periods of time. Due to this, a planet’s speed is
not constant in its orbit (faster = closer to the Sun)
• 3. The Harmonic Law = The farther a planet is
from the Sun, the longer its period of
revolution (2 Reasons: the orbit is longer and
the planets closer to the Sun move faster) i.e.
= Earth = 30 km/sec and Mercury = 49 km/sec
Newton’s Laws of Gravitation
• Isaac Newton (1642 – 1727) = Created three
laws of motion. Discovered the Law of
Gravitation
The Law of Gravitation: Every mass exerts a force
of attraction on every other mass and the strength
of the force is proportional to each of the masses
and inversely proportional to the distance between
them.