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PSSC: The Earth Sciences
Dr. Neil Suits, Assistant Professor of Earth ScienceOffice: Sci 118 Phone: 896 ‐ 5931
Best times to see me are right after class on Mondays and Fridays
Email also is good.
PSSC: The Earth Sciencesreadings and quizzes
8th EditionCh 14: pp 358-368Ch 15: scan the chapter, look at the figures and read the captions, know all the planets in the solar system, know the two types of planets, know terms in boldface.Ch16: 406-409; 411-412; 418-425Ch 17: 432-435; 439-447(mineral formation)
7th EditionChapter 14, pages 388-398Chapter 15, scan the chapter. Know the planets of the Solar System, know the two types of planets, know terms in boldfaceChapter 16, pages 438-441; (Places & Time) 443-446; Moon, etc. 452-460Chapter 17, pages 466-470; Read Figure Captions; 473-482.
First quiz, next Wednesday.
PSSC: The Earth Sciencestopics we will cover
Time and Place: Where the Earth and Solar System come from.
Basic Geology: How rocks and minerals are formed as well as mountains and oceans. We will also look at the geology of Montana, and take a quick tour through the fossil record.
Weather and Climate: What is the difference between weather and climate? What controls the weather and what are the facts about Climate Change?
~14 GA
(Giga Annum: Billion Years)
today
~ 300,000 years after the Big Bang
The first map of the Universe. Not homogeneous.
Cosmic microwave background (CMB) anisotropy. First detected by the COBE DMR instrument.
Typical spiral galaxy. Similar to ‘our’ Milk Way Galaxy’
~100,000 light years in diameter
We would be about here
~ 100 Billion Stars~100,000 light years across
We are not alone.
About 80 billion galaxies in the observable universe.
About 400 billion stars in the Milky Way galaxy (but that may be a bit larger than average)
Many (most?) of those probably have planets.
How many of those planets are terrestrial (Earth-like?)
How many have life?
Stars
• Sun
– An average star
– Reference for understanding other stars
• Massive, dense balls of incandescent gas
• Powered by nuclear fusion reactions in their core
(E = mc2)
Origin of stars
• Gaseous nebula– Mostly hydrogen
• Shock waves induce gravitational collapse– Gravitational energy
released into higher temperatures and pressures
• Protostar– Accumulation of gases that
will become a star
http://faculty.rmwc.edu/tmichalik/NebandStar.htm
Star Birth and Formation: Protostars
The internal structure of the Sun
Stellar modeling
• Core– Very hot, most dense region
– Nuclear fusion releases gamma and x-ray radiation
• Radiation zone– Radiation diffuses outward
over millions of years
• Convection zone– Structured by hot material
rising from the interior, cooling, and sinking
– Upper reaches: visible “surface” of star
– Sun surface temp. ~5,800 K
Lifetime of the Sunor any star
• Our Sun converts about 1.4x1017 kg of matter to energy each year – About 2,700 6000 lb SUVs!
– E = mc2 ( units = kg m2/sec2 = Joules)
• Lifetime of a star depends on its mass– Less massive stars have longer lifetimes
– More massive stars have shorter lifetimes
• Born 5 billion years ago
• Enough hydrogen for another 5 billion years
But not every star is like the Sun……
The Crab Nebula in Lyra
Remnants of a supernova
….the most violent event ever seen in the universe — flashed into view on the morning of March 19th.
"This burst was a whopper," said Swift principal investigator Neil Gehrels of NASA's Goddard Space Flight Center in Greenbelt, Md. "It blows away every gamma ray burst we've seen so far."
….the March 19th, 2009 burst had a redshift of 0.94, corresponding to a look-back time of 7.5 billion years — several thousand times more than the nearby galaxies.
The farthest object ever seen by the naked eye.
Most gamma ray bursts occur when massive stars run out of nuclear fuel. Their cores collapse to form black holes or neutron stars, releasing an intense burst of high-energy gamma rays and ejecting particle jets that rip through space at nearly the speed of light like turbocharged cosmic blowtorches. When the jets plow into surrounding interstellar clouds, they heat the gas, often generating bright afterglows. Gamma ray bursts are the most luminous explosions in the universe since the big bang.
Why are some stars bright and others are not?
• Differences in stellar brightness1. Amount of light produced by
star
2. Size of star
3. Distance to star
• Apparent magnitude– observed brightness (how bright it
looks from Earth)
• Luminosity– actual brightness (how much light
the star is actually putting out)
What does the color of a Star tell you?
• Color variations apparent: red, yellow, bluish white
• Color related to surface temperature
– Blackbody radiation curves
– Red: cooler stars
– Blue: hotter stars
– Yellow: in between (Sun)
• Classification scheme
– Based on temperature: hottest to coolest
– O, B, A, F, G, K, M
Star color ~ star temperature
Life of a star
• Protostar stage– Gravitational collapse
– Density, temperature and pressure increase
– 10 million K: fusion ignition temperature
– Dynamical equilibrium• Inward force of gravity
• Outward pressure of fusion energy
– Star enters main sequence
Hertzsprung-Russel
Diagram
A stars fate depends on its mass
Fate of the Sun…. First a Red Giant, then a White dwarf within a planetary nebula
The Crab Nebula in Lyra
Remnants of a supernova
Magnetic fields around a sunspot
‘Winds' and ‘Waves’ on the surface of Sol
SUN Rocky
(Terrestrial) inner planets
The giant Gas planets of the outer solar system
Hydrogen, Helium, methane, water, ammonia
Silicates with Iron cores
Hyd
rog
en (7
4%
), so
me h
elium
(24
%)
Planet summary
Mercury
Venus
Earth
Mars
The Martian ice cap
Frozen water?
Craters on Mars
Olympus Mons
The largest mountain in the Solar System
Why is it so big?
~ 625 km (324 miles) diameter
Scarp Height~ 6 km (4 miles)
Olympus Mons on an overcast day
Evidence for water on mars
Wind-formed dunes on MarsAtmosphere: 0.7% of the Earth’s atmospheric pressure; 95% Carbon Dioxide (CO2), 3% Nitrogen (N2); 1.7% Argon, 0.1% Oxygen (O2)
View of the surface of Mars from the Martian lander
Figure 15.09a
Jupiter
Figure 15.09b
Movie of Jupiter
Saturn
Titan: moon of Saturn
landing400.mov
Uranus
Neptune
Pluto
Smaller bodies of the Solar System
• Comets, asteroids, meteorites
• Leftover from solar and planetary formation
• Mass of smaller bodies may be 2/3 of total Solar System mass
• Bombard larger objects– Comet Shoemaker-Levy 9
fragments (bottom)…– … and strikes Jupiter (July
1994)
Comet structure
• Small, solid objects
• “Dirty snowball” model
– Frozen water, CO2, ammonia, and methane
– Dusty and rocky bits
• Comet head
– Solid nucleus and coma of gas
• Two types of tails
1. Ionized gases
2. Dust
• Tail points away from Sun
Meteors and meteorites
• Meteoroids – Remnants of comets and
asteroids
• Meteor– Meteoroid encountering
Earth’s atmosphere
– Meteor showers: Earth passing through comet’s tail
• Meteorite– Meteoroid surviving to strike
Earth’s surface
– Iron, stony (chondrites and achondrites) or stony-iron
Figure 15.19b
Figure 15.19a
Our moon: Luna
Current hypothesis: Luna was formed as a result of an impact by a Mars-sized object in the early stages
of Solar System formation.
Lunar impact craters
Crater Tycho
Close up of Tycho