Stellar astronomy

• the study of the objects that lie beyond the solar system and the processes by which these objects interact with one another

Scientific Method

• Ask a “simple” question

• Research the question

• Formulate a Hypothesis (An educated guess, not a theory)

• Test your hypothesis (design an experiment)

• Analyze your data and develop a “theory” (based on facts, evidence)

• Must be subject to peer review

Critical Thinking

• Exploring misinformation and disinformation

• Extraordinary claims require Extraordinary evidence

• All things considered; the simplest explanation is usually the best

• Humans have always been terrible at understanding coincidences

• What is your evidence? What is your source?

• How reliable is that source? Who decides its reliability?

• There are NO alternative facts

• Science has always been a “work in progress”

The Roots of Astronomy

• The ancients required knowledge of the sky in order to survive

• They used the sky:

  • As a calendar (seasons)

  • For navigation

  • For story telling

  • And then there was Curiosity

• Most early civilizations used lunar cycles as their calendars

Why was understanding the sky so important for survival?

• When to plant their crops, when to harvest

• When herds were migrating

• When they should migrate

• When was it safe to travel into the mountains for hunting and gathering?

• Understanding the timing of ocean tides for fish and travel

Determined Seasons using the sun

• Stonehenge: Summer solstice

• Newgrange: Winter solstice

• Chichen Itza: Equinoxes

Determined seasons using the stars

• Summer and spring have different star systems

Navigation

• Used Polaris as a “North, South Landmark

• Minoans used Hydra as their “West, East Landmark”

Curiosity

• What were the wanderers? What were meteors? What were comets? Why did the moon change shape? What were eclipses?

Most common problems Astronomers face

• We cannot touch what we are studying

  • The only thing we can study is its light

• Enormous distances

  • Difficult to measure distances accurately. Without distance, there are many properties we can't understand

• Enormous sizes/masses/densities/speeds

  • Requires “new” physics, Special and general Relativity, Particle Physics and more

• Time (millions and billions of years)

  • Difficult to reconstruct histories, can only be determined by studying “populations” of objects

Spectroscopy

• The study of an object’s light

• Wavelength, absorption lines, hydrogen, sodium, calcium etc

Ground based telescopes

Space telescopes

James Webb telescope (JWST)

Laboratory research

Measuring distances in astronomy

• One astronomical unit (AU) is 93 million miles, average distance from the earth to the sun

• One light year (LY)  is the distance light travels in one year

• One parsec (PC) is 3.26 light years

• At 65 Mph it would take 163 years to drive to the sun, 1AU

• 100,000

Light travel units (LTU)

• Speed of light is 186,000 miles a second or 300,000 km a second

• Light second is the distance light travels in one second

  • Moon is 1.3 light seconds away

• Light minute is the distance light travels in one minute

  • The sun is 8.3 light minutes away

• Light hour, light day, light year etc

How far can you see without telescopes (naked eye)

• The farthest planet you can see is Uranus, 2 hours 40 light minutes

• The farthest star you can see is 16,000 ly in Cassiopeia

• The farthest object you can see naked eye is the Andromeda Galaxy, 4.3 million ly

Where are we?

• Earth in Sol’s system, located in the solar neighborhood, high is a group of stars located in the Milky Way galaxy

  • Diameter: 140,000 light years across

  • Around 1.5 trillion masses (100-400 billion stars)

  • The sun is located around 30,000 ly from the center of the galaxy

• Milky Way is located in the “local group” of galaxies

  • Approximately 80 galaxies

  • The area between galaxies is called “intergalactic space”

• Galaxy groups are organized into galaxy clusters

  • Our local group is located in the Virgo cluster

• Clusters are organized into superclusters

• The Virgo cluster is located in the Virgo supercluster (laniakea)

• Superclusters are organized into filaments and walls

• Visible universes

  • 5% of the universe is made out of visible matter

  • 27% is made out of dark matter

  • 68% is made out of dark energy

    Deep Sky Objects The Constellations Areas of the sky Pareidolia Illusion of. Recognizable image where none exists The face on the surface features of the moon Asterism An asterism is a recognizable pattern of stars Big Dipper, Little Dipper, Orion The classical constellations 48 classical constellations were described by Ptolemy in “Almagest” which was written in 120 AD Pallets of marker-3200 BC The oldest known constellations Bayer Catalogue: southern sky Some defunct constellations… Felis (the cat) noctura (the owl) Using constellations Mnemonics Navigational aids Art Rituals and calendars As storytelling mnemonics The story of Perseus and Andromeda Navigation Urea Major: the Drinking Gourd- Polaris is North Art Altas- Palace of Farnese, Rome Starry Night- Van Gogh Astronomical Alignments Lakota Medicine Wheel Mayan Celestial Alignments Modern Constellations A constellation is an area of the sky The sky is divided into 88 official constellations. Most are based upon the constellations of the Ancient Greek tradition and contains the signs of the zodiac The 13 constellations of the Zodiac are called the Zodiacal Constellations Star names Individual stars can have many names Naming the stars Star names and designations Proper names Bayer designations Flamsteed designations Proper names of stars Most bright star names are Arabic They begin with “Al”, which means “the” Algol-the ghoul, Alioth-the black horse, Alkaid-the leader of the recession of mourners, Alnilam-the string of pearls Alnitak-the belt Bayer designations All stars have other names The Bayer designation uses the Greek alphabet to designate the stars. The brightest star is the alpha star, the second brightest is the beta star, etc The Greek letter can then be followed by “in” and the constellation name, or the constellation’s genitive (possessive name) Example the brightest star in Orion would be (alpha) in Orion Alpha, beta, gamma, delta, epsilon, zeta, eta, theta, iota, kappa, lambda, mu, nu, xi, omicron, pi, rho, sigma, tau, upsilon, phi, chi, psi, omega Flamsteed designation Stars can also have a “Flamsteed number” 25 in Orion; 25 Orionis Drake Equation N=R*. Fp x ne x fl x fi x fc x L N= number of civilizations with which humans could communicate R*= mean rate of star formation Fp= fraction of stars that have planets Ne= mean number of lancets that could support life per star with planets Fl= fraction of life supporting planets that develop life Fi= fraction of planets with life where life develops intelligence Fe= fraction of planets with life where life develops intelligence Fe= fraction of intelligent civilizations that develop communication L= mean length of time that civilizations can communicate Charles Messier 1730-1817 (will be on quiz) Comet hunter Nicknamed the Comet Ferret August 1758, discovery of Messier Object #1 Commonly called M1 Galaxies The largest entities in the universe Huge accumulations from several million to hundreds of trillions of stars Nebulae-4 types Clouds of dust and gas, remnants of dying or dead stars Emission Nebula Emits light and glow as newly formed stars ionize the gases The red color is caused by the ionization of hydrogen gases The “birthplaces” of new stars Evolve to become “open clusters” Reflection Nebula The bluish white light is created as light from newly formed stars is reflected off left over dust grains Absorption Nebula Also called “dark nebula”, are dust clouds which block light Orion Nebula, Horsehead Nebula Planetary Nebula Ejected envelopes of red giant stars Appear as expanding, symmetrical clouds of gas with shapes similar to “smoke rings” Supernova Remnants Remnants of a massive star, greater than 8 solar masses, which has violently exploded The Fate of a Star, whether or out it ends its life as a Planetary Nebula, SuperNova, Neutron Star, Black hole, etc, is determined by its MASS M1 The Crab Nebula A bright supernova recorded by Chinese and Arab astronomers in 1054 Located at a distance of about 6.5k light years Star Clusters Two categories of Clusters Globular Clusters Ancient stars: 10-12 billion years old as old or older than the galaxies Cool “red” stars Population 10k-1 million stars Separated by light weeks/months Found in the “halo” of the galaxy Open Clusters Also called Galactic Clusters Young, newly formed stars… “blue and white” stars Population: 10-300 stars Found within the plane of the galaxy Binary Star Systems Star system made up of two gravitationally bound stars Messier 40, double star M40 (WNC 4) in Ursa Major The celestial sphere A rotating crystalline sphere to which the celestial bodies are attached The belief that everything revolves around the Earth Celestial Equator Imaginary line that divides the celestial sphere into Northern and Southern Hemispheres Meridian Imaginary line that runs from the north to the south and divides the Celestial Sphere into East and West Hemispheres North/South Celestial Poles (NCP)-(SCP) The north and south celestial poles are the two magi army points in the sky where the Earth’s axis is extended out onto the celestial sphere Ecliptic Apparent path of the Sun, Moon and planets through the background stars of the Zodiacal constellations