Transcript solar.gmu.edu

ASTR 111 – 003
Lecture 14 Dec. 3, 2007
Fall 2007
Introduction To Modern Astronomy I:
Solar System
Introducing Astronomy
(chap. 1-6)
Planets and Moons
(chap. 7-15)
Sun and Life: Highlights
(Chap. 16 & 28)
Ch1: Astronomy and the Universe
Ch2: Knowing the Heavens
Ch3: Eclipses and
the Motion of the Moon
Ch4: Gravitation and
the Waltz of the Planets
Ch5: The Nature of Light
Ch6: Optics and Telescope
Ch7: Comparative Planetology I
Ch8: Comparative Planetology II
Ch9: The Living Earth
Ch10: Our Barren Moon
Ch11: Mercury, Venus and Mars
Ch12: Jupiter and Saturn
Ch13: Satellites of Jupiter & Saturn
Ch14: Uranus, Neptune and Beyond
Ch15: Vagabonds of Solar System
Ch16: Our Star: the Sun
Ch28: The Search for Extraterrestrial Life
Our Star, the Sun
Chap. 16
Energy from the Sun sustains life on the Earth
Basic Facts
• Diameter: 1,400,000 km
• Distance to Earth: 1 AU = 1.5 X 108 km
• Light travel time: 500 seconds
• Angular size: 30 arcmin
• Effective Surface Temperature: 5800 K
Thermonuclear reactions
• Sun’s total energy output: 1026 watts
• Can not be chemical energy (only last 10,000 years)
• Can not be gravitational contraction (only last 25
million years)
• Energy from nuclear reaction
– Corresponds to a reduction of mass according
Einstein’s mass-energy equation:
E = m c2
Thermonuclear reactions
•The Sun’s energy is produced by hydrogen fusion: a
sequence of thermonuclear reactions in which four
hydrogen nuclei combine to produce a single helium
nucleus; called proton-proton chain reaction
Thermonuclear reactions
4 H  He + energy + neutrinos
Mass of 4 H > Mass of 1 He
•In every second, 600 million tons of hydrogen converts
into helium to power the Sun
•At this rate, the Sun can last for about 10 billion years
•It is now 4.6 billion year old
•It will continue the hydrogen burning for at least another
5 billion years.
The sun itself is extremely stable. It controls
the climate of the Earth
Dynamic Atmosphere
•
However, the Sun’s atmosphere is extremely dynamic
Dynamic Atmosphere
Space Weather: the Effects
Human Space Exploration
Aviation
Satellite Operation
Power
Aurora
Communication and Navigation
The Search for
Extraterrestrial Life
Chap. 28
The State of the Universe
•Age: 13.7 billion years
•Size:
•Composition:
•dark energy: 73%
•dark matter: 23%
•ordinary matter: 4%
Chemical building blocks of life
• All life on Earth is
based on carbonbased compounds,
called organic
molecules
• These organic
molecules occur
naturally in the
interstellar clouds
of gas and dust,
called nebula,
throughout galaxies
Liquid Water
• Liquid water may be
needed for Earth-like
life
• Besides Earth, at least
two worlds in our solar
system—the planet
Mars and Jupiter’s
satellite Europa—may
have had liquid water
The Drake equation
Estimate how many civilizations may inhabit our Galaxy:
about 10
=1 per year
=1
~0.1
~1
~1
~1
~100 years
Search…Search…
Dedicated to search for
extraterrestrial
intelligent life (SETI)
ATA: Allen Telescope Array
of 350-dishes when completed.
42 dishes now working
Seth Shostak:
“I think we will find signals
from intelligent
civilizations by 2025”