Astro 2021B All Weeks (Final Exam Prep.)

Purpose of Mission: Viking 1 and 2

Sent to Mars to search for signs of life

Purpose of Mission: Galileo

Studied Jupiter and its moons, especially Europa

Purpose of Mission: Cassini-Huygens (1997)

Explored Saturn and its moons, particularly Titan and Enceladus

Purpose of Mission: Mars Exploration Rovers (Spirit and Opportunity) (2003)

Searched for evidence of past water on Mars

Purpose of Mission: Mars Curiosity Rover (2011)

Investigated Mars’ habitability

Purpose of Mission: Mars Perseverance Rover (2020)

Searching for signs of ancient life and collecting samples

Amount of years Galileo orbited Jupiter

Eight years

Purpose of Mission: Europa Clipper

Determine if Europa has conditions suitable to support life

James Webb Space Telescope

Premier observatory of the next decade, serving thousands of astronomers worldwide. It studies every phase in the history of our universe

James Webb Space Telescopes 3 Significant Roles in the Search for life beyond Earth

1. Atmosphere Analysis

2. Detection of Habitable Zones

3. High-Resolution Imaging

How many laws does “Kepler’s Laws of Planetary Motion” have?

Three

Kepler’s 1st Law of Planetary Motion

Planets move in elliptical orbits with the Sun as a focus

Kepler’s 2nd Law of Planetary Motion

A planet covers the same area of space in the same amount of time no matter where it is in its orbit

Kepler’s 3rd Law of Planetary Motion

A planets orbital period is proportional to the size of its orbit (its semi-major axis)

Geocentric Model

The earth is at the center of the cosmos or universe, and the planets, the sun and the moon, and the stars circle around it

Heliocentric Model

The sun is the center, and the planets revolve around the sun.

Orbits are generally inclined by no more than 3.4 degrees. What two planets in our solar system are exceptions to this?

Mercury and Pluto

What is a Terrestrial Planet

Planets that are relatively small in size/mass, and have rocky surfaces

What is a Jovian Planet

Much larger in mass/size planets that have lower average density. They always have rings and are mostly gas (no solid surfaces)

Terrestrial Planets In Our Solar System

Mercury, Venus, Earth and Mars

Jovian Planets In Our Solar System

Jupiter, Saturn, Uranus, Neptune

Percentage Composition of the Sun

75% Hydrogen and 25% Helium

How far is the Sun from Earth?

1 Astronomical Unit (AU)

How long is the Solar Cycle?

22 Years

After __ years, North/South order of leading/trailing sunspots is reversed

11

The Sun’s Magnetic Dynamo

The fact that the sun rotates faster at the equator than near the poles. This differential rotation might be responsible for magnetic activity of the sun.

How many exoplanets have been discovered?

Slightly more than 5500

Habitable (Goldilocks) Zone

The orbital distance from a star at which temperatures could allow liquid water on the surface, of the planet. This makes a planet a target for possible signs of life and habitability.

Planets in our solar system considered in the Habitable (Goldilocks) Zone

Earth and Mars

3 Ways of Studying Possibility of Life Beyond Earth

1. Study conditions conducive to the origin and ongoing existence of life

2. Look for such conditions on other planets in our solar system and around other stars

3. Look for the actual occurrence of life elsewhere

Purpose of Mission: Dragonfly

Explore diverse locations to characterize the habitability of Titan’s (one of Saturn’s moons) environment.

How many stars our in our galaxy

More than 3×10^10

What is Omar Khayyam’s significance

A Persian polymath known for his contributions to math, astronomy, and philosophy.

Who introduced the Jalali Calender?

Omar Khayyam

Who is revered for bridging poetry and science?

Omar Khayyam

Astrolabe

A sophisticated, ancient astronomical instrument used to measure to positions of celestial objects, determined time, and solve various astronomical problems.

3 Purposes/Applications of Astrolabe

Astronomy, Navigation, Timekeeping

4 Astronomical Features of Stonehenge

Solstice Alignment, Lunar (cycle) and Solar (eclipse) Tracking, Ritual Significance, Ancient Observatory

What is the Templo Mayor

The main temple of the Aztec capital

Significance of Templo Mayor

Equinox Alignment: the run rose between the two shrines at the top of the temple during spring and autumn equinoxes, symbolizing harmony between the deities

What was the Equinox Alignment from the Templo Mayor used to mark?

Agricultural Calendar

Within Chapter 2, what is an important element in modern science?

Carefully recorded repeatable observations

What is a Scientific Model?

A conceptual representation that explains and predicts phenomena

Main drawbacks of Scientific Models

A model can only include certain aspects of nature and not everything

Name Greek philosophers in the order of models/laws covered by chapter 2 (years 624 B.C to 1727) (Hint: Starting with Thales and ending with Newton)

Thales (624 - 546 B.C)
Anaximander (610 - 546 B.C)
Pythagoras (560 - 480 B.C.)
Eudoxus [First Geocentric Model] (~380 B.C)
Aristotle (384 - 322 B.C.)
Eratosthenes (~240 B.C.)
Ptolemy [“Sophisticated” Geocentric Model] (~150)
Nicholas Copernicus (1473 - 1543)
Tycho Brahe (1546 - 1601)
Johannes Kepler (1571 - 1630)
Galileo (1564 - 1642)
Newton (1642 - 1727)

What was Thales’ significance

The first known model of the Universe (Earth is flat) that did not rely on supernatural forces

What was Anaximander’s significance

He introduced the concept of celestial spheres, which explained the rotation of the sky around the (North) pole star

What was Pythagoras’ significance

He taught that the Earth is a sphere (due to mathematical perfection). Was a key player in the geocentric model.

What was Eudoxus’ significance

He developed the first Geocentric model. It consisted as a series of cosmic spheres containing the stars, the sun, and the moon all built around the Earth at its center.

What four elements did Ancient Greek Philosophers believe that Earth was born from?

Fire, Water, Earth, Air

Who were Atomists

People which believed the world was made form an infinite number of indivisible atoms of each of the four elements

What (5th) element did Ancient Greek Philosophers believe that the Heavens was made of?

Aether (or Quintessence)

What was Aristotle’s significance

Cited evidence of Earth’s round shadow on the Moon during lunar eclipses. Was a key player in the geocentric model.

What was Eratosthenes’ significance

He measured the Earth’s size (circumference)

Celestial Body Which Named: Sunday

Sun

Celestial Body Which Named: Monday

Moon

Celestial Body Which Named: Tuesday

Mars

Celestial Body Which Named: Wednesday

Mercury

Celestial Body Which Named: Thursday

Jupiter

Celestial Body Which Named: Friday

Venus

Celestial Body Which Named: Saturday

Saturn

What was Ptolemy’s significance

He developed the most sophisticated Geocentric model. This was so accurate, that it remained in use for 1500 years. Was (obviously) a key player in the geocentric model.

Main problem with Ptolemy’s Geocentric Model

The use of epicycles made it too complex (and led to predicted positions of planets being off by several degrees by 1400 A.D.)

Three Key Players of the (“sophisticated”) Geocentric Model

Pythagoras, Aristotle, Ptolemy

How did the Ptolemaic model explain retrograde motion?

Epicycles

Through the ___, the heliocentric model was introduced, being much less complicated than the geocentric model

Copernican Revolution

Why did Copernicus introduce the heliocentric model?

Because of the main problem with the geocentric model (the fact that the use of epicycles made it too complicated)

What was Nicholas Copernicus’ significance

He brought about the heliocentric model through beginning the Copernican Revolution, in turn, explaining retrograde motion without epicycles

What was Tycho Brahe’s significance

He made the most precise (“naked-eye”) astronomical observations that challenged the geocentric model, in turn, supporting the Copernican Revolution.

What was Johannes Kepler’s significance

He abandoned circular orbits in favor of ellipses and formulated the three laws of planetary motion. His contributions supported the Copernican Revolution.

What was Galileo’s significance

He overcame the three major objections to the Copernican view, in turn. supporting the Copernican Revolution.

Four Main Supporters of the Copernican Revolution (in chronological order)

Nicolaus Copernicus, Tycho Brahe, Johannes Kepler, Galileo

What is the Geocentric Model

A earth-centered universe

What is the Heliocentric Model

A sun-centered universe; supported by the Copernican (Revolution) Theory

3 Pros of the Copernican Theory

• Simple

• Mercury and Venus closer to Sun than Mars

• Changing brightness of planets

3 Cons of the Copernican Theory

• Still used circular orbits

• Offset needed (similar to Ptolemy)

• No more accurate than Ptolemy

How many Laws of Planetary Motion did Kepler come up with?

3; Kepler’s Three Laws of Planetary Motion

Kepler’s First Law of Planetary Motion

The orbit of each planet around the Sun is an ellipse with the Sun at one focus (being the perihelion).

What is an Ellipse? What are it’s two focus points called?

An oval which resembles the path of a planet around its star. It has two focus points on both (farthest) ends, with one called the perihelion and the other called the aphelion.

What is a Perihelion

The focus point on an ellipse, at which a planet is closest to its star.

What is a Aphelion

The focus point on an ellipse, at which a planet is farthest from its star.

What is a semimajor axis?

The distance between the center of an ellipse to a focus point (almost like a radius)

Kepler’s Second Law of Planetary Motion

As a planet moves around its orbit, it sweeps out equal areas in equal times. Implies a planet travels faster when near its star (the perihelion) and slower when farther from its star (the aphelion).

Kepler’s Third Law of Planetary Motion

That more distant planets orbit the sun at slower average speeds.

Three Key Objections against Copernican (Revolution) Theory

1. Nature of Motion: If Earth is moving, wouldn’t it objects be left behind

2. Heavenly Perfection: Non-circular objects are not “perfect” as heavens should be

3. Parallax: If Earth were really orbiting Sun, we’d detect stellar parallax

Overcoming The Nature of Motion objection against the Copernican Theory

Due to Newton’s first law of motion, moving objects remain in motion unless a force acts on it, meaning objects around Earth would move with it

Overcoming the Heavenly Perfection objection against the Copernican Theory

Tycho’s observations prove that the heavens undergo changes as well.

Overcoming the Parallax objection against the Copernican Theory

Galileo showed that stars are likely farther than Tycho predicted, meaning that the lack of detectable parallax wasn’t troubling for the Copernican model

Steps of The Idealized Scientific Method

Make Observations, Ask a Question, Suggest a Hypothesis, Make A Prediction, Perform a Test/Experiment/Additional Observation

How many Hallmarks of Science are there?

3

Issue with The Idealized Scientific Method

That science rarely proceeds in this idealized way and that we often must follow our intuition rather than a particular line of evidence.

First Hallmark of Science

That modern science seeks explanations for observed phenomena that rely solely on natural causes; A scientific model cannot include divine intervention.

Second Hallmark of Science

Science progresses through the creation and testing of models of nature that explain the observations as simply as possible.

Third Hallmark of Science

A scientific model must make testable predictions about natural phenomena that would force us to revise or abandon the model if the predictions do not agree with observations.

What was Newton’s significance

He realized that the same physical laws that operated on Earth also operated in the heavens, leading to the laws of motion and gravity.

How many Laws of Motion are there?

3

Newton’s First Law of Motion

An object moves at constant velocity unless a net force acts to change its speed or direction.

Newton’s Second Law of Motion

To move a heavier object, you need a stronger force. To move an object faster, you need more acceleration (a stronger force); F = ma

Newton’s Third Law of Motion

For every action, there is an equal and opposite reaction.

How many Laws of Gravity are there?

3