EPS SCI 9: Planets

B. B. Boltwood (1870-1927)

- Boltwood used radiometric dating to detect the age of the Earth. - He took the measurements in ores that indicate lead to be a final product of uranium decay, and extrapolated the uranium decay rate from the assumption of decay equilibrium and the previously measured radium decay rate.

Marie and Pierre Curie (1898)

- Coined the term "radioactivity," - Proved that radioactivity was a property of atoms - Discovered the radioactivity of thorium

Tycho Brache (1546 - 1601 AD)

- Discovered a nova/new star (supernova), showing the universe is changing. - Endorsed the idea the Sun orbits the Earth while all other planets orbit the Sun - Still believed that all heavenly motions must follow perfect circles in the sky. - Made naked- eye observations with unparalleled accuracy over a 30 year period. With his data, neither the Ptolemy model nor the Copernican model accurately predicted the path of planets.

Ernest Rutherford (1871-1937)

- Discovered the nucleus of the atom (1910) and the concept of the atomic number (number of protons in the nucleus). - With Frederick Soddy he discovered that elements decayed into other elements in predictable ways via a series. - He also suggested using radioactivity (uranium/helium or uranium/lead ratios) as a way to tell the age of the Earth's rocks.

Jovian Planets

- Do not have solid surfaces - Mostly made out of hydrogen, helium, and hydrogen compounds (compounds containing water, ammonia, and methane). - Have systems of regular satellites, resembling miniature solar systems - Spaced farther apart and are farther from the Sun - Lower in average density than terrestrial planets - Have rings and many moons.

Arthur Holmes (1890-1965)

- He published several uranium/lead ages based mostly on measurements taken by Boltwood and an improved value for the uranium decay rate ranging from 340 million years to 1,640 million years. In 1927 he published a booklet containing estimates of the total quantity of uranium and lead in the Earth's crust, suggesting that the age of the Earth is between 1.6 and 3 billion years. - He also proposed that convection in the mantle is the force driving continental drift (1929)

Galileo (1564-1642)

- He was the first person to use a telescope to observe objects in space. - Came up with evidence to back up the Copernician model using the phases of Venus and parallax Discovered: - Planets are disks, not points - Phases of Venus - Moons of Jupiter - Sunspots, solar rotation - Craters on our moon - The Milky Way

William Thomson aka Lord Kelvin (1824-1907)

- Helped formulate the laws of thermodynamics and introduced an absolute scale for measuring temperature (Kelvin) - Using thermodynamic principles and measurements of thermal conductivity of rocks, Kelvin calculated that the earth consolidated from a molten state 98 million years ago. In 1897, he revised his estimate to 20-40 million years. (Did not consider convection)

Mercury

- Large iron core (high density as a result) - Smallest planet - Resembles the moon in appearance: heavily cratered - Contains plains created by ancient lava flows and tall, steep cliffs

Uranus

- Made largely of hydrogen, helium, and hydrogen compounds such as water, ammonia, and methane - Does not have a solid surface - At least 27 moons - Tipped on its side - Icy giant, icy moons

Saturn

- Made mostly of hydrogen and helium - Does not have a solid surface - Visible rings made of small particles of rock and ice - Has at least 62 moons, two of which are geologically active today: Titan (the largest) and Enceladus

Earth (The blue planet)

- Only planet with oxygen, an ozone (shields from solar radiation), abundant surface water, and therefore life - Has a single moon

Mars (The red planet)

- Polar caps made of frozen carbon dioxide and water (liquid water once covered the surface) - Covered with iron oxide dust (rust) - Has ancient volcanoes and giant canyons and mountains - Two moons: Phobos and Deimos

Titan

- Saturn's largest moon - Has lakes of liquid methane and methane-rain - Dense atmosphere

Neptune

- Similar in appearance to Uranus (blue) due to methane gas, but smaller and more dense. - Rings - Has at least 14 moons, the largest being Triton

Venus (Sister Planet)

- Similar mass, density, and chemical composition to Earth -Rotates the Sun clockwise - Rotates on its axis very slowly - Intense greenhouse effect and thick atmosphere creates a hot, and heavily pressured environment.

Terrestrial Planets

- Small, dense, and rocky bodies - They orbit closest to the Sun and are closer together - Have an abundance of metals in their cores. - Volatile elements (e.g., water) have reached the inner planets even though bulk compositions of the planets suggest formation at high temperatures. - Generally have few moons, if any, and no rings

Jupiter

- The biggest - Made primarily of hydrogen and helium. - Has a thin set of rings and at least 67 moons, 4 of which are large enough to be considered planets/dwarf planets (called the Galilean Moons).

The Sun

- The largest and brightest object in our solar system (source of almost all light in our solar system). - Made up of hydrogen and helium gas. - The temperature and pressure increase with depth. - Its gravity governs the orbits of the planets

Triton

- The largest moon of Neptune - Only large moon with a retrograde orbit (that is, an orbit opposite to the rotation of its planet), - Geologically active and has geysers that are assumed to erupt nitrogen.

The Copernican Revolution

- The solar system is heliocentric. The planets revolved around the sun in perfect circles, rather than the Earth. - Showed that the motions of other celestial bodies could be explained by the motions of the Earth. - Asserted that the earth rotated on its axis once daily and traveled around the sun once yearly; - Proved the retrograde motions of the planets were only apparent motions -- not real motions.

Structure of the Solar System

-Sun -Inner, smaller, rocky planets (Mercury, Venus, Earth, Mars) -Asteroid belt. -Outer, larger, gaseous planets (Jupiter, Saturn, Uranus Neptune) -Kuiper belt.

Measurements

1 AU = 1 Earth-Sun distance = 1.49 * 10^8 km (149 million km) 1 Parsec = 3.1 * 10^13 km (31 trillion km) = 3.26 light years Center of the Galaxy is ~8 kpc (8000 pc) from the Earth and Sun (~26000 light years) Angle of 1 degree = 60 minutes of arc = 3600 arc seconds Arc second = 1/60th of 1/60th of a degree or 1/3600th of a degree

Newton's Three Laws of Motion

1- law of inertia: an object will continue to be at rest or in motion, unless a force is exerted on it. 2: The force between the two objects is directly proportional to the product of their masses. F=m x a or force = mass times acceleration 3. For every action there is an equal and opposite reaction

Newton's Law of Gravitation

1. Every object with mass attracts every other object with mass. 2. The force between the two objects is proportional to the product of their masses and inversely proportional to the square of the separation between them 3. The force of gravity decreases with the square of the distance between the centers of the objects Shows the sun's gravity weakens with distance from the Sun

2 Answers to Olber's Paradox

1. Expanding universe causes visible light to stretch to longer wavelength (microwave background) 2. The universe is finite in age (light takes time to get to us)*

Johannes Kepler's (1571-1630) Three Laws of Planetary Motion

1. Planets moved in elliptical (not perfect circles) orbits, moving in the shape of an ellipse with two foci, the sun being one of them and the other is nothing 2. The planets go faster when nearer to the sun and slower when farther from the Sun, sweeping out equal areas in equal times 3. The square of the period of any planet is proportional to the cube of the planet's average distance from the Sun. As a result, more distant planets orbit the Sun at slower average speeds and the larger the planet the slower it moves

Why made Charles Lyell's and James Hutton's theories of uniformity wrong?

1. Radioactive nuclides decay with time 2. Oxygen gas accumulated late in Earth's atmosphere 3. The colonization of land by life; 4. Plate tectonics 5. Asteroid bombardment.

Solar System's Properties of Motion

1. The planets all revolve around the sun in the same direction: counterclockwise. This is the same sense as the rotation of the Sun about its axis 2. All the planets lie roughly within sun's equatorial plane and the orbits of all the planets lie within 18º of the plane of the ecliptic (= plane of Earth's orbit). 3. With a couple of exceptions the planets have a prograde rotation (rotation in the same direction as they revolve about the Sun) 4. Many, but not all, planets have moons and most moons orbit in the same sense as planetary orbits.

How old is the universe?

13.8 billion years old

How old is the Earth?

4.54 billion years old

Galaxy

A huge group of single stars, star systems, star clusters, dust, and gas bound together by gravity and orbiting a common center

Titius-Bode Law

A law the predicts the spacing between planets in the solar system. Led to the discovery of the asteroid belt and Uranus a = (n+4)/10

Uniform Expansion

All the galaxies are moving away from each other at roughly the same velocity.

Parallax

An apparent shift in the position of stars when the Earth moves around the sun. Measured by how distant stars shift back and forth as the Earth travels around the Sun.

Obliquity (tilt)

Angle between a planet's equatorial plane and its orbital plane (how inclined its axis of rotation is) Gives us seasons (tilted away from the sun = winter, towards = summer)

Alfred Wagner (1880-1930)

Came up with continental drift theory in 1912

2 Theories on the Start of the Universe

Catastrophism and Uniformitarianism

Claire Patterson (1922-1995)

Conducted radiogenic lead isotope calculations on meteorites to estimate the initial lead isotopic composition of Earth, allowing him to get to an age of 4.55 ± 0.07 billion years (for the solar system).

Asteroid Classes

D: CH rich P: CH rich C: CI, CM, irons and stony-irons S: reflect light more, OC, CV, CO E: Chondrite or aubrite

Henri Becquerel (1852-1908)

Discovered radioactivity of uranium

The more ... the galaxy is, the ... it appears to be moving

Distant Faster

Isotope

Each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties; in particular, a radioactive form of an element.

Edmund Halley (1656-1742)

English astronomer and mathematician who was the first to calculate the orbit of a comet later named after him. In 1717, he suggested using the salt content of oceans to calculate the age of the Earth.

How do stars form?

Forms inside relatively dense concentrations of interstellar gas and dust known as molecular clouds. Begins when the denser parts of the cloud core collapse under their own weight/gravity, forming a Protostar. Gravity compresses the material in a cloud to the point where the center becomes dense enough and hot enough to generate energy by nuclear fusion

Why is the inner solar system hot and the outer solar system cold?

Friction. Potential energy turns into heat within the inner solar system as it spins. The friction is greater on the inside than on the outside, due to the larger density. Energy gets trapped by the density of the material of the inner solar system, and the radiation effect is hot. In the outer solar system, energy is free to get out because it is less dense, so the radiation effect is cold.. This leads to a snowline in the outer solar system, which contains icy bodies

Archimedes

Gave us a way to express very large numbers through scientific notation

Not all solar systems are...

Identical

Volatiles (H20, CO2, CH4, N2..) ... as you go to the outer solar system.

Increase

Why does Venus rotate clockwise?

Initially, Venus was rotating the Sun counterclockwise, but at some point a large impact may have reversed its rotation by flipping its axis 180 degrees

Silicate rocks are more present in the...solar system because...

Inner Terrestrial planets were too hot to hold the volatile gases from the solar nebula

Sir Isaac Newton (1642-1727)

Introduced 3 new laws of motion for all objects on Earth and showed the same laws apply to the heavens. Wrote the Principia

Why is Uranus blue-green?

It has methane in its atmosphere, which absorbs red light and makes the planet appear blue-green.

Leonardo da Vinci

Italian painter and sculptor and engineer and scientist and architect. Did not believe in the "Great Flood" as being responsible for the existence of fossils at mountain tops.

Why does Uranus rotate on its side?

Its extreme axis tilt may be a result of a cataclysmic collision it suffered while forming, giving it the most most extreme seasonal variations of any planet in our solar system

Planets in order of size

Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Mercury

Formation of Jovian Planets

Large ice rich planetesimals formed in the cold, outer regions of the swirling disk. With accretion, they became massive enough for their gravity to capture some of the hydrogen and helium gas that made up the vast majority of the surrounding solar nebula, making their gravity even stronger. Each Jovian planet came to be surrounded by its own disk of gas.

The universe is

Large, expanding, infinite, lumpy

Inverse Square Law of Light

Light gets duller as you move farther away. As the distance from a light source increases, the intensity of light is equal to a value multiplied by 1/d^2 Replace D with R. R = distance I = Intensity of light

Velocity of stars is (blank) related to distance

Linearly

Which planets move in retrograde motion?

Mars, Jupiter, and Saturn. When we pass Jupiter or Mars or Saturn, for example, these more outward planets in orbit - which move more slowly than Earth in orbit - appear to reverse course in our sky for a couple of months.

Planets in order of distance from the sun

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune

The inner solar system is ... dense than the outer solar system

More

Why do terrestrial planets like Earth have water and other volatile elements?

Must have been delivered to Earth from the outer Solar System from the impacts of icy planetesimals such as comets or asteroids

Newton's Version of Kepler's Third Law

Newton explained Kepler's elliptical orbits were a result of a force (gravity). He proved Kepler's laws were approximately correct, but provided some quantitative corrections

Nebular Theory

Our solar system formed from the gravitational collapse of an interstellar cloud of gas, called the solar nebula. This cloud gave birth to our Sun at its center and the planets in a spinning disk that formed around the Sun. Heavy elements produced by dying stars mixed with other interstellar gas to form new generations of stars. The Earth and other terrestrial worlds were made from heavier elements mixed within the original hydrogen and helium produced from the Big Bang.

How do planets capture moons?

Passing planetesimals lost energy to friction in the extended and dense gas that surrounded the early forming planets.

The Greek Geocentric Model of Motion

Placed a spherical Earth at the center of the universe, by which the other planets rotated around in perfect circular orbits, while the Earth stayed stationary

Why are asteroids concentrated in the asteroid belt?

Planetesimals that formed between Mars and Jupiter were strongly influenced by orbital resonances with Jupiter. Asteroids experience repeated tugs from Jupiter that tend to nudge them out of orbit, leading to collisions between them, as a result asteroids are overturned planetesimals

Why do the jovian planets have rings?

Ring particles are probably debris from moons.

Accretion and Formation of Terrestrial Planets

Small particles that orbited the forming Sun in orderly, circular paths began to combine into larger ones within the warm, inner regions of the swirling disk. As these particles grew in mass, they began to attract each other through gravity, accelerating their growth into boulders large enough to count as planetesimals. As they grew in size, they gained more surface area and gravity to attract other planetesimals, as a result, planetesimals collided to form into larger proto-rocky planets

John Joly (1899-1901)

Sought to estimate the age of the Earth from the salt content of the oceans, and came to the estimate of 90-100 million years (Mass of salt)/(Mass of salt/year) = years

Olber's Paradox (1823)

The apparent paradox that if stars are distributed evenly throughout an infinite universe of infinite age, the night sky should display a uniform glow, since every line of sight would terminate at a star. But with an expanding universe of finite age, visible light from very distant stars has not reached the Earth.

The Great Flood

The event which expressed God's desire to rid the world of human wickedness

The Galilean Moons

The four largest moons of Jupiter: Io (volcanically active), Europa (icy crust and water below), Ganymede and Callisto (subsurface oceans)

Why do Jovian planets have more satellites?

The giant planets have more moons than the terrestrial planets because of their great masses which result in stronger gravitational fields. And giant planets also occupy greater space and hold larger volumes of mass in their surrounding atmospheres.

The local group

The group of about 40 galaxies to which the Milky Way Galaxy belongs.

Spin Angular Momentum

The inherent angular momentum of a fundamental particle; often simply called spin.

Ecliptic Plane

The plane of Earth's orbit around the Sun. Earth's axis is tilted by 23.5 degrees from a line perpendicular to the ecliptic plane

Retrograde Motion and Ptolemaic Model (100-170 AD)

The planets moved around Earth on a small circle that turned upon a larger circle. The smaller circle is called an epicycle, and the larger a deferent.

Asteroids

The rocky leftover planetesimals of the inner solar system that orbit the Sun in the same direction as the planets, but are too small and numerous to be considered planets. Asteroids have rocky bodies that occupy a wide belt between the orbits of Mars and Jupiter called the Asteroid Belt. Their orbits tend to be more elliptical and more highly inclined to the ecliptic plane.

Uniformitarianism

The theory that changes in the earth's crust during geological history have resulted from the action of continuous and uniform processes. Based on the work of James Hutton (Scottish geologist, 1726-1797) and made popular by Charles Lyell in the 19th century

Catastrophism

Theory that states that natural disasters such as floods and volcanic eruptions shaped Earth's landforms and caused extinction of some species

What was wrong with John Joly's calculations?

There was no way to account for recycled salt, salt incorporated into clay minerals, salt deposits.

How do planets form?

Through accretion. Small particles that orbited the young Sun began to combine into larger ones. As these particles grew in mass, they began to attract each other through gravity, accelerating their growth into boulders large enough to count as planetesimals. As they grew in size, they gained more surface area and gravity to attract other planetesimals, as a result, planetesimals collided to form into larger proto-rocky planets The young Sun pushed much of the gas out to the outer Solar System and its heat evaporated any ice that was nearby, leaving rockier planets closer to the Sun and gas giants that were further away

Retrograde Motion

Typically, the planets shift slightly eastward from night to night, drifting slowly against the backdrop of stars. From time to time, however, they change direction. For a few months, they'll head west before turning back around and resuming their easterly course

Charles Lyell 4 Principles of Uniformity (1830)

Uniformity of law: the natural laws have remained the same Uniformity of process: same causes today as in the past Uniformity of rate: changes occurred at the same rate as now Uniformity of state: the Earth was much the same in the past as it is now

Which planets orbit clockwise?

Venus and Uranus (and Pluto)

Differentiation

While the Earth or any other planet was molten, gravity acted to concentrate more dense material near the center and less dense material nearer the surface. When the planet solidified again it was left with a layered structure with more dense material like iron and nickel near the center and less dense rocks nearer the surface. The outer layers then cooled and solidified, leaving a mantle in between the core and the outer surface.

Galaxy Cluster

a group of galaxies

Orbital Angular Momentum

a measure of the rate of rotation

Eccentricity

describes how much an ellipse is stretched out in comparison to a perfect circle

Kepler Telescope

is orbiting the sun searching for Earth like planets. The telescope was launched on March 7, 2009

Half life

length of time required for half of the radioactive atoms in a sample to decay

Natural Satellite

objects that orbit the another body that are not man made - the moon is an example

Kepler Orrery

solar systems discovered by Kepler

Light Year

the distance light travels in one year (about 10 trillion km)

Radiometric Dating

the process of measuring the absolute age of geologic material by measuring the concentrations of radioactive isotopes and their decay products

Angular Momentum

the quantity of rotation of a body, which is the product of its moment of inertia and its angular velocity. Any object that is either spinning or moving along a curved path has angular momentum (Earth has angular momentum due to its rotation--rotational angular momentum--and orbital rotation due to its orbit around the Sun--orbital angular momentum) angular momentum = m x v x r

The Hubble Constant

value (H) used to calculate the rate at which the universe is expanding; measured in 74.2 kilometers per second per megaparsec