Astronomy 101 The Solar System Tuesday, Thursday Tom Burbine

Course Course Website: – Textbook: –Pathways to Astronomy (2nd Edition) by Stephen Schneider and Thomas Arny. You also will need a calculator.

There is an Astronomy Help Desk that is open Monday-Thursday evenings from 7-9 pm in Hasbrouck 205. There is an open house at the Observatory every Thursday when it’s clear. Students should check the observatory website before going since the times may change as the semester progresses and the telescope may be down for repairs at times. The website is

HW #10, #11, #12, #13, and #14 Due March 30 th at 1 pm

What Planet do we know the most about?

Earth The planet we know best 70% covered with water

Earth’s crust 46.6% O 27.7% Si 8.1% Al 5.0% Fe 3.6% Ca 2.8% Na 2.6% K 2.1% Mg

Earth is made of minerals

Mineral A naturally occurring, homogeneous inorganic solid substance having a definite chemical composition and characteristic crystal structure ~4,000 known minerals –100 can be called "common" –50 are "occasional“ –the rest are "rare" to "extremely rare".

Olivine (Mg, Fe) 2 SiO 4 Fayalite (Fa) - Fe 2 SiO 4 Forsterite (Fo) - Mg 2 SiO 4

Pyroxenes Examples: Enstatite - Mg 2 Si 2 O 6 Ferrosilite - Fe 2 Si 2 O 6 Augite - (Ca, Na)(Mg, Fe, Al)(Al, Si) 2 O 6 Augite Ferrosilite

Mineral – A naturally occurring, homogeneous inorganic solid substance having a definite chemical composition and characteristic crystal structure Rock - naturally occurring aggregate of minerals

Forming Different Mineralogies Can be on a planet-scale Or a few meters to kilometers

Some minerals form before other minerals

What minerals form? Depends on the composition of the magma Depends how quickly the magma cools

Types of Rocks Igneous – rock that solidified from molten or partially molten material Metamorphic - rock that has changed in composition, mineral content, texture, or structure by the application of heat or pressure Sedimentary – rock formed from material that was deposited as sediment by water, wind, or ice and then compressed and cemented

Igneous Rock

Metamorphism Quartzite

Sedimentary Examples of two types of sedimentary rock: limey shale overlaid by limestone

Rock formed from sediments covers 75-80% of the Earth's land area

Oldest rocks on Earth Oldest dated mineral –zircon mineral (ZrSiO 4 ) with an age of billion years enclosed in a metamorphosed sandstone conglomerate in the Jack Hills of the Narryer Gneiss Terrane of Western Australia. –Zircons contain trace amounts of uranium and thorium Oldest rock on Earth –The Acasta Gneiss in the Canadian Shield in the Northwest Territories, Canada has zircons with an age of billion years. Other rocks may be older (but are still being argued about)

Zircon

How do we know what’s in the interior of the Earth?

Seismic Waves – vibrations created by earthquakes

Seismic Waves P waves – primary waves – (pushing) – travel faster – can travel through anything S waves – secondary – (side to side) – travel slower – only through solids

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Surface Waves Travel on the surface of the Earth Love Wave – side by side mation.gifhttp:// mation.gif Rayleigh Wave – rolling movement _animation.gifhttp:// _animation.gif Most of the shaking felt from an earthquake is due to the Rayleigh waves

P (primary) waves S (secondary) waves Surface waves: Rayleigh and Love waves

Richter Scale Measures the magnitude of an earthquake Single number to quantify the amount of seismic energy released by an earthquake. Amplitude of largest displacement Under At most slight damage to well-designed buildings. Can cause major damage to poorly constructed buildings Can be destructive in areas up to about 100 kilometers across where people live Major earthquake. Can cause serious damage over larger areas. 8 or greater - Great earthquake. Can cause serious damage in areas several hundred kilometers across.

How do we get information? The precise speed and direction of the waves depends on the composition, density, pressure, temperature, and phase (solid or liquid)

Which of these bodies have they used seismic waves to study?

How can you study the interior of a planet from space?

Density Density = mass/volume If the density is higher than the surface rock, there must be denser material in the interior

Gravity If you can measure gravity (force) with a spacecraft as it rotates around a body, you can determine how mass is distributed on the body

Magnetic Field Tells if a planet has a molten metal interior Magnetic field definition: –a physical field that arises from an electric charge in motion, producing a force on a moving electric charge

Earth’s magnetic field is believed to be caused by the convection of molten iron, within the outer liquid core along with the rotation of the planet Electrons flow

Magnetic pole moves

North Magnetic Pole However, the "north pole" of a magnet is defined as the one attracted to the Earth's North Magnetic Pole By this definition, the Earth's North Magnetic Pole is physically a magnetic south pole

Glatzmeier and Roberts simulations :

Geomagnetic Reversals Based upon the study of lava flows of basalt throughout the world, it has been proposed that the Earth's magnetic field reverses at intervals, ranging from tens of thousands to many millions of years The average interval is ~250,000 years. The last such event, called the Brunhes- Matuyama reversal is theorized to have occurred some 780,000 years ago.

The present strong deterioration corresponds to a 10– 15% decline over the last 150 years and has accelerated in the past several years Geomagnetic intensity has declined almost continuously from a maximum 35% above the modern value, which was achieved approximately 2000 years ago. At this rate, the dipole field will temporarily collapse by 3000–4000 AD

What may happen during the reversal? There may be a slight rise in the per capita cancer rate due to a weaker magnetic field. We may also be able to see the northern lights at lower latitudes If you own a compass, it will have difficulty finding north until the magnetosphere settles.

Van Allen Belts The Van Allen radiation belts are rings of energetic charged particles around Earth, held in place by Earth's magnetic field Outer belt – primarily electrons Inner belt – primarily protons

Van Allen Belts

James Van Allen Sent a Geiger Counter on the first US satellite Explorer 1 The Geiger counter began clicking madly as soon as it reached orbit

Auroras Auroras – natural light displays Collision of charged particles from Earth's magnetosphere with atoms and molecules of Earth's upper atmosphere The collisions in the atmosphere electronically excite atoms and molecules in the upper atmosphere. The excitation energy can be lost by light emission or collisions.

Rocks on the Surface If you can see rocks on the surface that comes from the interior, you can study them

Rocks can deform and flow Easier for rock to deform and flow when it is warmer

Lithosphere Lithosphere is a planet’s outer layer of cool and relatively rigid rock Asthenosphere is the region in the upper mantle characterized by low-density, semi-plastic (or partially molten) rock material chemically similar to the overlying lithosphere

Heating of Planet

How does the planetary interior cool off? Heat is transported outward

How does the planetary interior cool off?

Plate Tectonics Plate tectonics describes the large scale motions of Earth's lithosphere. Venus – does not appear to have plate tectonics Mars – maybe Satellites of Jupiter – maybe Titan (Satellite of Saturn) - maybe

Pangea Pangea - One large supercontinent

Principles of Plate Tectonics 1. The surface of the Earth is composed of lithospheric plates that are in constant motion. 2.The plates move in response to plastic flow in the athenosphere. 3.Motion in the asthenosphere is caused by convection driven by the Earth’s internal heat. 4.The internal heat comes from radioactive decay and the latent heat from the Earth’s formation.

Three Types of Plate Tectonic Boundaries Divergent – plates move apart, space is filled with molten magma Convergent – plates collide Transform – plates slide horizontally past each other

Divergent plate boundary

When lava cools Lava is a mixture of melted minerals (some are magnetic). While lava is liquid, the minerals will tend to line up with a magnetic orientation pointing at the North Pole. When the lava solidifies, the magnetic orientation is frozen into the rock- essentially; it will have a “north end” and a “south end.”

Magnetic stripes on Mars

Convergent Plate Boundary

Hot spots

Transform Boundaries

Earth’s Atmosphere Layer of gases surrounding the planet Earth that is retained by Earth's gravity The atmosphere –protects life on Earth by absorbing ultraviolet solar radiation –warming the surface through heat retention (greenhouse effect) –reduces temperature extremes between day and night.

Air (by volume) 78% nitrogen 21% oxygen 1% argon 0.04% carbon dioxide ~1% water vapor

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Greenhouse Effect The greenhouse effect is the rise in temperature that a planet experiences because certain gases in the atmosphere (H 2 O, CO 2, CH 4, O 3 ) trap energy emitted from the surface. Visble light hits the surface Surface warms and emits infrared radiation Atmospheric gases absorb some of the infrared light Surface and atmosphere heat up

Stefan-Boltzman Law Emitted power (per square meter of surface) = σT 4 λ·T max = 2,900,00 nm

Contribution to Greenhouse Effect water vapor (H 2 O) 36–72% carbon dioxide (CO 2 ) 9–26% methane (CH 4 ) 4-9% ozone (O 3 ) 3–7%

Any Questions?