ASTRONOMY Lecture

Kyle Kremer

• Office hours: Wednesday, 2pm - 3pm on zoom (Link on canvas - starts Oct. 2)

• Email: kykremer@ucsd.edu

Textbook: Bennett et al., The Cosmic Perspective 10th Ed. (ISBN 9780135208113), with Mastering Astronomy

Access Pearson

Topics covered in astronomy 1

• The sun and other stars, including their types and structure

• How stars are born

• How stars live and evolve over time

• How stars die

• Stellar remnants - white dwarfs, neutron stars, and black holes

• Etc.

SCAN TRON TESTING Buy your own scan tron

Globulalr Clusters

Mergers of black hole pairs emit gravitational waves

What is a galaxy?

Galaxy

• A great island of stars in space, all held together by gravity and orbiting a common center

What is a star?

Star

• A large, glowing ball of gas that generates heat and light through nuclear fusion

Stars create the elements

10/1/2024

Solar systems

• A star and all the material that orbits it, including its planets and moons

  • Planets and dwarf planets

Planet

• A moderately large object that orbits a star. Planets may be rocky, icy, or gaseous in composition

Universe sized numbers

• The fundamental scales of distance (meters), time (seconds) and mass (kilograms) in the Universe have huge ranges

1. Use Scientific Notations

   1. 1.5 x 10^11

2. Add a prefix to create a new unit

   1. E.g. 13,000,000,000 years = 13 giga years (gyr)

3. Define a new unit based on standard

   1. E.g. 700,000,000 meters - 1 solar radius

   2. Some standards

      1. Solar radius, luminosity

4. IMPORTANT SCALES

   1. Orbit of moon: radius = 4 x 10^8 m

Light year

Composition of the Universe

• 75% Dark Energy

• 21% Dark Matter

• 4% Normal Matter

A wide range of motions

Constellations

• In astronomy, a constellation is a region of the sky.

• Eighty-eight constellations fill the entire sky

The 12 constellations in the plane of the Earth’s orbit are called the zodiac

The sun appears to move through the zodiac constellations over

Star names vs. Star brightness

• Only a few very bright stars have formal names

• mOst are labeled according to brightness in constellation:

  • a

  • b

  • y

Scientific notation 1000000 1x10^(# of zeros)

N/V=n

• Distance between Earth and sun is also known as Astronomical unit

• The distance that light can travel in one year is also known as light-year

The celestial sphere

• Stars at different distances all appear to lie on the celestial sphere

• The 88 official constellations cover the celestial sphere

North celestial pole is directly above Earth’s North Pole

South celestial pole is directly above Earth’s South Pole

Celestial equator is a projection of Earth’s equator onto sky

Elliptic is the Sun’s apparent path through the celestial sphere

This is where the zodiac constellations lie

• Zenith: the point directly overhead

• Horizon: the “ground”, 90 degrees from zenith in all directions

• Meridian: line connecting N to S passing through zenith

• An object’s altitude (above horizon) and azimuth (along horizon) specify its location in the sky

• We use altitude and direction to pinpoint things in the sky

• We use latitude and longitude to pinpoint locations on Earth

• We use declination and right ascension to pinpoint locations on the celestial sphere

Right ascension is like longitude

• it means a star’s position west to east relative to the spring equinox

Declination is like latitude

• it measures as star’s position south to north relative to celestial equator

Earth rotates from west to east, so stars appear to circle from east to west

Astronomy 1: Stars and Black Holes - Lecture 2 Notes

Instructor: Kyle KremerDate: October 1, 2024Course: ASTR 1, UC San Diego

Page 2: Announcements

• Homework Deadlines:

  • Homework #0 due tonight by 11:59 PM (extra credit only)

  • Homework #1 due Friday by 11:59 PM

• Modified Mastering Account:

  • Create an account ASAP to resolve issues before deadlines.

• Content Coverage:

  • Material from last week, today, and Thursday.

Page 4: Today's Topics

• Definitions and concepts in astronomy

• Working with large numbers

• The speed of light and its implications for viewing the past

• Observing the sky from Earth

• Understanding constellations

• Reasons for the rising and setting of stars

• Variability of visible stars based on location and time of year

Page 5: The Universe

• Encompasses vast scales in:

  • Distance

  • Time

  • Motion

  • Mass

  • Energy

Page 10-12: Working with Universe-Sized Numbers

• Scientific Notation:

  • Example: 150,000,000,000 meters = 1.5 x 10^11 meters

• Operations with Big Numbers:

  • Multiplication: Multiply coefficients, add exponents.

  • Addition: Convert to the same exponent, then add coefficients.

• Common Prefixes:

  • n- (nano), µ- (micro), m- (milli), c- (centi), k- (kilo), M- (mega), G- (giga), T- (tera)

• Defining New Units:

  • Example: 700,000,000 meters = 1 solar radius (R☉)

Page 13-18: Important Scales

• Earth and Moon:

  • Earth diameter ≈ 1 x 10^7 m

  • Moon orbit radius ≈ 4 x 10^8 m

• Solar System:

  • Radius ≈ 1.5 x 10^13 m = 100 AU

• Nearest Stars:

  • Distance ≈ 10^17 m ≈ 10 light years

• Galaxies:

  • Nearest galaxy (Andromeda) ≈ 2.5 x 10^22 m ≈ 2,500,000 light years

Page 19-21: Viewing the Past

• Light Travel Time:

  • Example: Orion Nebula as it appeared 1500 years ago.

  • Andromeda Galaxy as it appeared 2.5 million years ago.

• Implication:

  • Observing distant objects means seeing them as they were in the past.

Page 33-41: Constellations

• Definition:

  • A constellation is a region of the sky; there are 88 official constellations.

• Zodiac:

  • The 12 constellations in the plane of Earth's orbit.

• Star Naming:

  • Bright stars have formal names; others are labeled by brightness (α, β, γ).

Page 49-56: The Celestial Sphere

• Celestial Coordinates:

  • Right Ascension (longitude) and Declination (latitude).

• Star Movement:

  • Stars appear to rise and set due to Earth's rotation.

• Latitude Impact:

  • The sky varies with latitude but not with longitude.

Page 60-64: Star Paths

• Star Movement:

  • Depends on latitude and star's declination.

• Circumpolar Stars:

  • Stars near the north celestial pole never set.

• General Movement:

  • Most stars, including the Sun and Moon, rise in the east and set in the west.

Page 66-70: Angular Measurements

• Measurement Basics:

  • Full circle = 360°

  • 1° = 60' (arcminutes), 1' = 60" (arcseconds).

• Angular Size Calculation:

  • Example: Moon's angular size calculated based on its physical size and distance.

Page 74-76: Seasonal Visibility of Constellations

• Dependence on Latitude:

  • Position on Earth determines which constellations are visible.

• Dependence on Time of Year:

  • Earth's orbit changes the apparent location of the Sun among the stars.

Questions

• Open floor for any questions regarding the material covered.

Physics 5 Lecture Notes

Announcements (Page 1)

• Homework #1: Due Friday by 11:59 PM

• Modified Mastering Account: Create ASAP to resolve issues before the deadline

• Textbook Reading: Not required; serves as a reference. Reading is optional based on personal learning style.

YouTube Resources (Page 2)

• Videos on Celestial Sphere and Seasons:

  • Video 1

  • Video 2

  • Video 3

Key Topics for Today (Page 4)

• Star Movement: Why do stars rise and set?

• Visibility of Stars: How location and time of year affect star visibility.

• Degrees and Angular Size: Understanding measurements in the sky.

• Earth's Movement: Spin and orbit around the Sun.

• Solar vs. Sidereal Day: Differences between the two.

• Seasons: Relation to Earth's axial tilt.

• Orientation of Earth's Axis: Changes over time.

Celestial Coordinates (Page 8)

• Right Ascension: Similar to longitude; measures star position west to east relative to the spring equinox.

• Declination: Similar to latitude; measures star position south to north relative to the celestial equator.

Star Movement (Page 9)

• Rising and Setting: Stars appear to circle from east to west due to Earth's rotation from west to east.

Latitude and Sky Variation (Pages 11-12)

• Sky Variation: The sky varies with latitude but not with longitude.

Altitude and Latitude (Page 14)

• Altitude of Celestial Pole: Equals your latitude.

Star Paths (Pages 19-21)

• North Pole: Stars remain at the same altitude as Earth rotates; altitude equals declination.

• Equator: All stars remain above the horizon for 12 hours each day; celestial equator passes overhead.

• Northern Hemisphere: Stars with declination greater than (90° - your latitude) are circumpolar.

Angular Measurements (Pages 24-25)

• Full Circle: 360 degrees

• Subdivisions: 1 degree = 60 arcminutes; 1 arcminute = 60 arcseconds.

• Angular Size Calculation: Angular size = (physical size / distance) × (360 degrees / 2π).

Example Calculation (Page 26)

• Moon's Angular Size: Diameter of 3500 km at a distance of 380,000 km results in an angular size of approximately 0.6 degrees.

Constellations and Visibility (Page 29)

• Dependence on Latitude: Position on Earth determines which constellations are visible.

• Dependence on Time of Year: Earth's orbit changes the apparent location of the Sun among the stars.

Earth's Motion (Pages 33-34)

• Orbital and Rotational Motion: Viewed from above the North Pole, Earth orbits and rotates counterclockwise.

• Fundamental Time Reckoning:

  • Day: Spin cycle of Earth.

  • Year: Orbital cycle around the Sun.

  • Season: Caused by Earth's tilt.

  • Month: Orbital cycle of the Moon around Earth.

Solar vs. Sidereal Day (Pages 36-42)

• Sidereal Day: One full rotation of Earth (23 hours, 56 minutes, 4.07 seconds).

• Solar Day: Time from noon to noon (24 hours); solar day is 4 minutes longer than a sidereal day.

Mean Solar Time (Page 44)

• Variation: Length of a solar day changes due to Earth's elliptical orbit.

• Definition of Noon: Average time when the Sun crosses the meridian.

Seasons (Pages 48-56)

• Misconception: Earth is not closer to the Sun in summer; seasons are due to axial tilt.

• Tilt of Earth's Axis: Approximately 23.5°; fixed orientation towards Polaris.

• Solar Light Incidence: Direct sunlight in summer vs. shallow incidence in winter.

• Seasonal Dates:

  • Equinoxes: Equal illumination in both hemispheres.

  • Solstices: One hemisphere experiences summer while the other experiences winter.

Special Latitudes (Pages 58-60)

• Arctic Circle: Sun never sets on summer solstice.

• Tropic of Cancer: Sun directly overhead at noon on summer solstice.

• Antarctic Circle: Sun never sets on winter solstice.

• Tropic of Capricorn: Sun directly overhead at noon on winter solstice.

Orientation of Earth's Axis (Page 61)

• Precession: Earth's axis precesses over approximately 26,000 years; Polaris will not always be the North Star.

Questions? (Pages 3, 17, 22, 28, 32, 43, 47, 57, 62)

• Open floor for any questions regarding the material covered.

Astronomy 1: Stars and Black Holes - Lecture 4 Notes

Page 1: Lecture Information

• Course: Astronomy 1: Stars and Black Holes

• Instructor: Kyle Kremer

• Date: October 8, 2024

• Institution: UC San Diego

Page 2: Announcements

• Homework #2: Due Friday by 11:59 PM (Chapters 3, 4)

  • Start early, skip uncertain problems, return after lecture.

• Class Format: Next Tuesday (October 15) will be on Zoom; no in-person lecture.

  • Zoom link will be posted on Canvas and sent via email.

Page 3: Review

• Altitude: The angle of a star above the horizon.

• Polaris: Its altitude equals your latitude on Earth.

• Star Coordinates: Measured using Right Ascension and Declination.

• Sun's Movement: Appears to move through the ecliptic plane.

• Angle Measurements:

  • 1 degree = angle subtended by a finger.

  • 1/60 degree = arcminute.

  • 1/60 arcminute = arcsecond.

Page 5: Today's Topics

• Reason for the seasons.

• Changes in Earth's axis orientation over time.

• The scientific method.

• Physical quantities used to measure the Universe.

• Description of motion.

• Newton’s Laws of Motion.

• Newton’s Gravitational Law.

• Conservation laws in nature.

Page 10: Incidence of Solar Light

• Insolation:

  • Steep incidence → Summer (more direct sunlight).

  • Shallow incidence → Winter (less direct sunlight).

Page 12: Distance and Seasons

• Earth-Sun Distance: Variation is about 3%, negligible compared to axis tilt effects.

• Seasonal Variation: Minimal distance change during seasons.

Page 13: Key Dates in Seasons

• Equinoxes: Spring & Fall - equal illumination in both hemispheres.

• Solstices: Summer & Winter - one hemisphere experiences summer while the other experiences winter.

Special Latitudes

• Article Circle (66.5 degrees N): Sun never sets on summer solstice

• Tropic of Cancer (23.5 degrees N): Sun directly overhead at noon on summer solstice

• Antarctic Circle (66.5 degrees S): Sun never sets on winter solstice

• Tropic of Capricorn (23.5 degrees S): sun directly overhead at noon on winter solstice

Page 16: Earth's Axis Orientation

• Precession: Earth's axis precesses over approximately 26,000 years.

• Polaris: Will not always be the North Star.

• Equinox Shift: Positions of equinoxes shift around the orbit.

Page 19: The Scientific Method

• Observations: Lead to questions about patterns and workings of nature.

• Hypothesis Formation: Develop models based on observations.

• Testing: Predictions are challenged through experiments.

Page 27: Scientific Laws vs. Theories

• Scientific Law: Describes patterns in nature that are consistently observed.

• Scientific Theory: Explains the origin of laws and must be supported by evidence.

Page 30: Principles of Modern Science

• Empiricism: Limited to observable phenomena.

• Simplicity: Theories should be as simple as possible (Occam’s Razor).

• Testability: Theories must make predictions that can be tested.

Page 33: Astronomy vs. Astrology

• Astronomy: Scientific study of celestial objects and phenomena.

• Astrology: Belief in hidden influences of celestial positions on human lives.

• Distinction: Astronomy adheres to scientific principles and testable predictions.

Page 37: Copernican Revolution

• Heliocentric Model: Sun at the center of the Solar System.

• Retrograde Motion: Explained without epicycles; occurs when Earth passes a planet.

Page 59: Importance of Measurement

• Quantification: Essential for creating theories and models of the Universe.

• Mathematics: The natural language of the Universe.

Page 60: Fundamental Physical Quantities

• Length, Time, Mass, Temperature, Electrical Current, Intensity of Light, Amount of Substance.

Page 62: Units of Measurement

• Length: Meters, kilometers, light-years, etc.

• Time: Seconds, hours, years, etc.

• Mass: Grams, kilograms, solar masses, etc.

• Temperature: Degrees Fahrenheit, Celsius, Kelvins.

Page 66: Derived Physical Quantities

• Velocity: Length/Time (e.g., m/s).

• Angular Speed: Angle/Time.

• Momentum: Mass x Velocity.

Page 68: Describing Motion

• Motion: Change in position over time.

• Speed: Rate of movement (e.g., 10 m/s).

  • Speed = ∆ position / ∆time

• Velocity: Speed with direction (e.g., 10 m/s east).

• Acceleration: Change in velocity over time.

  • Acceleration = ∆ velocity / ∆ time

Page 73: Scalars vs. Vectors

• Scalar: Only magnitude (e.g., speed).

• Vector: Magnitude and direction (e.g., velocity).

• Scalar ≠ Vector (NEVER EVER)

Page 75: Gravity on Earth

• Acceleration: All falling objects near Earth's surface accelerate at approximately 10 m/s².

Page 79: Questions

• Open floor for questions

10/10

Physics 5 Lecture Notes

Page 1: Announcements

• Homework #2

  • Due Friday by 11:59 pm (Chapters 3, 4)

  • Start early in the week; attend Thursday lecture for assistance.

• Class Format

  • Next Tuesday (October 15) will be on Zoom; no in-person lecture.

  • Zoom link will be posted on Canvas and sent via email.

Page 2: Review

• Planetary Motion

  • Retrograde motion observed around opposition.

  • Geocentric model: Earth at the center.

  • Heliocentric model: Sun at the center (Copernicus).

• Scientific Concepts

  • Law: A pattern always observed in nature.

  • Theory: A physical explanation for observed phenomena.

• Physics Fundamentals

  • Vector quantity: Specifies both magnitude and direction.

  • Acceleration: Change in velocity over time.

  • Gravitational acceleration on Earth: ~10 m/s².

Page 4: Aristotle on Motion

• Natural Motion

  • Heavy objects fall faster than light ones.

  • All things naturally come to rest.

  • A force is needed for "violent" motion (e.g., throwing a ball).

Page 6: Galileo's Discoveries

• Key Findings

  • Weight does not affect downward motion; gravitational acceleration is constant.

  • Recognized buoyancy and friction as forces acting on objects.

Page 7: Newton's Laws

• Three Laws of Motion

  1. Objects remain at constant velocity unless acted upon by a force.

  2. Acceleration depends on mass and force applied (a = F/m).

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

Page 9: Momentum

• Definition

  • Momentum (p) = mass (m) x velocity (v).

  • Momentum is a vector quantity with both magnitude and direction.

Page 11: Mass vs. Weight

• Definitions

  • Mass: Amount of matter in an object.

  • Weight: The force acting on an object due to gravity.

  • You are weightless in free-fall.

Page 14: Newton’s Second Law

• Force and Motion

  • A change in motion is proportional to the motive force and occurs in the direction of the force.

  • Formula: acceleration = Force ÷ mass.

Page 16: Force as a Vector Quantity

• Units

  • Force is measured in kg m/s² or Newtons.

Page 17-19: Types of Forces

• Contact Forces

  • Striking force, support (normal) force, friction, tension, buoyancy.

• Non-contact Forces

  • Gravitational force, electromagnetism, strong force, weak force.

Page 25: Gravity

• Observations

  • Gravity is an attractive force between objects with mass.

  • Interaction can occur without contact and depends on mass.

Page 26: Newton’s Universal Law of Gravitation

1. Every mass attracts every other mass.

2. Attraction is proportional to the product of their masses.

3. Attraction is inversely proportional to the square of the distance between their centers.

• Universal Gravitational Constant G = 6.67 x 10^-11m³/ kg-s²

Page 31-33: Gravity and Tides

• Tidal Effects

  • Moon's gravity causes tidal stretching on Earth.

  • The Sun also has a smaller tidal effect.

Page 42: Conserved Quantities

• Key Concepts

  • Momentum, angular momentum, and energy are conserved in interactions.

Page 49: Conservation of Angular Momentum

• Definition

  • Angular momentum cannot change unless acted upon by a twisting force (torque).

Page 53: Conservation of Energy

• Energy Forms

  • Energy can take many forms: kinetic, potential, thermal, etc.

  • Energy is a scalar quantity and cannot be created or destroyed.

• Kinetic Energy

  • Is a measure of an object’s motion:

• Thermal Energy

  • The collective kinetic energy of many particles

  • Temperature is the average kinetic energy of the many particles in a substance

  • There

Page 55: Kinetic Energy

• Definition

  • Kinetic energy depends on mass and the square of speed.

Page 66: What is Light?

• Nature of Light

  • Light is a form of energy associated with the electromagnetic force.

  • Exists as both electromagnetic waves and photons.

Page 68: Interaction of Light and Matter

• Types of Interactions

  • Emission, absorption, transmission, reflection, and scattering.

Page 71-72: Color Perception

• Examples

  • A rose appears red because it reflects red light.

  • The sky appears blue due to scattering of sunlight.

Page 73: Questions?

• Open floor for any questions regarding

10/15

Astronomy 1: Stars and Black Hole - Lecture 6

Kyle KremerOctober 15, 2024

Announcements (Page 2)

• Homework #3: Due Friday by 11:59 pm (Chapter 5)

• Midterm: Scheduled for Tuesday, October 22, in class

  • Covers Chapters 1-5 (as per lecture)

  • All multiple choice (similar to homework)

  • Review session on Wednesday

  • Scantrons: Required for the midterm (Form 882-E available at the bookstore)

Review of Newton's Laws (Pages 3-17)

• Newton’s First Law of Motion:

  • An object maintains a constant velocity unless acted upon by a force.

• Newton’s Second Law of Motion:

  • Acceleration is proportional to the applied force and inversely proportional to mass.

• Newton’s Third Law of Motion:

  • Every action has an equal and opposite reaction.

• Universal Law of Gravitation:

  • The force of gravity is inversely proportional to the square of the distance.

• Conservation of Momentum:

  • Propels rockets into space.

• Energy Conservation:

  • Energy exists in various forms but cannot be created or destroyed.

Today's Topics (Page 19)

• Light as a wave and particle

• The electromagnetic spectrum

• Properties of atoms

• Phases of matter

• Astronomical spectra

• Blackbody radiation

Understanding Light (Pages 22-24)

• Definition:

  • Light is a form of energy associated with the electromagnetic force.

  • Exists as both electromagnetic waves and photons.

• Colors of Light:

  • White light comprises various colors.

• Interactions with Matter:

  • Emission: Light produced (e.g., lightbulb).

  • Absorption: Light absorbed (e.g., sunglasses).

  • Transmission: Light passing through (e.g., window).

  • Reflection: Light bouncing off (e.g., mirror).

  • Scattering: Light dispersed in various directions (e.g., translucent window).

Properties of Waves (Pages 35-39)

• Wavelength: Distance between wave peaks (measured in meters).

• Frequency: Number of vibrations per second (measured in Hertz).

• Wave Speed: Calculated as wavelength x frequency.

• Light Waves:

  • Vibrations of electric and magnetic fields.

  • Can propagate through a vacuum, unlike sound waves.

Electromagnetic Spectrum (Pages 44-46)

• Definition:

  • The range of all types of light, from gamma rays to radio waves.

• Infrared Light:

  • Discovered by William Herschel in 1800, detected as heat beyond red light.

Matter and Atoms (Pages 50-56)

• Composition:

  • Matter consists of atoms, which have a nucleus (protons and neutrons) and electrons.

• Atomic Terminology:

  • Atomic Number: Number of protons.

  • Atomic Mass Number: Protons + neutrons.

  • Isotopes: Atoms with the same protons but different neutrons.

  • Ions: Atoms with a charge due to loss or gain of electrons.

• Phases of Matter:

  • Solid, Liquid, Gas, Plasma.

  • Phase changes depend on temperature and pressure.

Energy Levels in Atoms (Pages 61-63)

• Electron Orbits:

  • Electrons occupy specific energy levels and can transition between them by absorbing or emitting energy.

• Energy Level Transitions:

  • Allowed changes correspond to transitions between energy levels.

Spectra and Chemical Fingerprints (Pages 67-94)

• Spectrum:

  • Measurement of light at each wavelength from an astronomical object.

• Types of Spectra:

  • Continuous Spectrum: All visible wavelengths without interruption.

  • Emission Line Spectrum: Bright lines at specific wavelengths from low-density gas.

  • Absorption Line Spectrum: Dark lines from gas absorbing specific wavelengths.

• Chemical Fingerprints:

  • Unique patterns of emission and absorption lines corresponding to specific atoms.

Blackbody Radiation (Pages 111-114)

• Blackbody Emission:

  • Explains why stars appear in different colors based on temperature.

• Laws of Black Body Radiation:

  • Hotter objects emit more energy per square meter (Stefan-Boltzmann Law).

  • Peak wavelength shifts to shorter wavelengths as temperature increases (Wien’s Law).

Brightness and Temperature (Pages 120-123)

• Brightness:

  • Related to both temperature and size of the blackbody.

• Example:

  • Betelgeuse (3500 K) vs. Rigel (11000 K) - both appear similarly bright, but Betelgeuse is larger and closer.

Questions? (Pages 18, 31, 60, 78, 98, 108, 127)

• Open floor for any questions regarding