Astronomy

Astronomy

History of Astronomy

Hubble (1929, Expansion of the universe, observed red light)

Slipher (1919, The gap in the spectrum, red light = receding, blue light = approaching)

Henrietta Leavitt (1908, Measures distances according to the rhythm of the Cepheid supergiant signal)

Einstein (1905, Special and general theory of relativity, gravitational lensing, predicted black holes 1916, proven 1971)

Gravitational lensing: Magnifying light through distorted space and galaxies

General Theory of Relativity: Gravity distorts space and time.

Special Theory of Relativity: Time dilation, All movement is relative and speed of light has a limit, time slows down as we speed up

Bradley (1729, Speed of light = 3x10^5 km/s, "c", used a star parallax)

Halley (1682, Predicted that the same comet returns, Halley's comet)

Newton (1665, Explained Kepler's laws with the concept of gravity, type of orbit depends on the mass and speed of the object, gravitational attraction and speed opposes it

Elliptical: Small mass or low speed

Circular: Speed doesn't create eccentricity (perfect conditions)

Hyperbolic: Great speed or distance

Spiral: Low mass or speed

Galileo (1610, Jupiter's moons orbit Jupiter, objects can orbit something other than Earth, proved the geocentric theory wrong, put on house arrest by the Church)

Kepler (1609, assistant to Tycho, 3 laws of planetary motion

3. The longer a planet's orbital radius, the slower it orbits

2. Equal area in equal time (Planets move faster near the Sun)

1. All planetary motion is elliptical

Lippershey (1608, Telescope)

Bacon (Early 1600's, Scientific Method)

Tycho (1588, Observations and Supernova)

Copernicus (1543, Heliocentric Solar System, Afraid of the Church

Scientific Revolution (1500, Copernicus - Newton)

The Press (1400, information available to the public)

Renaissance (1300-1400, return of the arts and international trade)

Dark Ages (476-1500, No major science except Astronomy for Easter)

Ptolemy (140 BCE, Math Models of epicycles to describe the retrograde motion of mars)

Aristotle (322 BCE, Geocentric Theory, Crystals hold stars)

Pythagoras (540 BCE, Triangulation, quantified abstract ideas, c² = a² + b², Parallax = change in apparent position relative to a distant background when observing 2 different points)

Miletus (585 BCE, Predicted Solar Eclipse)

Greeks (150 BCE, Star map magnitude 1-6, reject supernatural)

Babylonians (1000 BCE, Predicts Lunar Eclipses)

Chinese (2000 BCE, Observatories)

Egyptians (4200 BCE, 365 day calendar) (Before Common Era)

Antiquity (Time, Date, Navigation)

Beyond the Solar System

Exoplanets (Planets beyond our solar system)

Galaxies

Formation of Galaxies

Swirl of Dust (Protoplanetary Disk)

Star

Types of Galaxies

Elliptical

Irregular

Lenticular

Barred-Spiral

Spiral

Units and Measure

Light Years

approx. 9.46x10^12 km (Distance light travels in a Earth year)

Used for interstellar distances

AU

1 AU = 1.5x10^8 km (Distance between our Earth and Sun)

Used for distances within our Solar System

Solar Systems

Comets, Asteroids, Meteoroids, Moons

Comets

Trans-Neptunian Objects (Objects beyond the orbit of Neptune

Kuiper Belt (Disk shaped group of millions of small objects orbiting the Sun and are thought to be from the formation of the Solar System

Oort Cloud (Spherical, Icy cloud of small debris)

Asteroids

The Asteroid Belt is a band of asteroids that orbit the sun in between Mars and Jupiter

Asteroids are thought to be debris left over from the formation of the Solar System, non-spherical, small, some have moons

Meteors, Meteoroids, Meteorites

Meteoroids (Pieces of rocks moving through space, thought to be broken parts of asteroids and planets)

Meteors (Meteoroids that enter the Earth's atmosphere and begin to burn up due to atmospheric friction)

Meteorites are the surviving meteors (ones that reached the ground without fully burning up)

Meteor Showers are what people also call "Shooting Stars", though they aren't stars and are in fact meteors, when the Earth passes through an area filled with these meteors, a meteor shower occurs

Moons

Tides

Tides occur due to the gravitational difference of the Moon and the Earth

Eclipses

Lunar Eclipse

Can only occur during a full moon, the Earth passes in between the Sun and the moon and can result in a partial lunar eclipse (penumbra shadow) or a total lunar eclipse (umbra shadow), the moon's orbit is tilting resulting in only 2 lunar eclipses on average per year, the moon can appear reddish during a lunar eclipse and is completely safe to watch

Solar Eclipse

Can only occur during a new moon, the Moon's shadow falls on the Earth's surface and is in between the Sun and the Earth, on average only twice a year however, due to the shadow's size being smaller, you often have to be in a remote or specific place to see the solar eclipse, it is not safe to look at the solar eclipse with just your eyes as the radiation can damage them

Penumbra and umbra are the inner and outer shadow of the Earth

When a celestial object moves directly in front of another celestial object

Phases of the moon

Waning Crescent

Third Quarter

Waning Gibbous

Full Moon

Waxing Gibbous

First Quarter

Waxing Crescent

New Moon

Moon phases are created by the reflection of sunlight on its surface (always half-luminated, what we see is based on where the moon is relative to Earth

Satelites (Celestial object orbiting another celestial object)

Planets

Planets in our solar system

Jovian (Gaseous)

Neptune

Furthest planet from sun, similar to Uranus

Uranus

Rotates on its side, rings, methane gas atmosphere

Saturn

Main composition of atmosphere: H & He, Rings

Jupiter

Gas Giant, Largest planet, Massive Red Storm

Terrestrial

Mars

Red Planet due to high concentration of Fe in its rocks, 2 polar ice caps, thin atmosphere

Earth

Only discovery of life, water in 3 forms, perfect atmosphere, temperature, etc.

Venus

Acid Rain (Sulfuric Acid), Dense atmosphere trapping heat, Hottest planet, Earth's sister, Similar to earth in size and composition

Mercury

No atmosphere, From Extremely hot to freezing cold, smallest planet

Protostar (Gravitational Center)

Swirling dust and Hydrogen gas

Planetesimals

Stars

Our Sun

Photosphere (Surface layer of the Sun)

Sunspots (Charged Particles disturb the photosphere and appear darker due to the difference in temperature and create strong magnetic fields)

Solar Flares (Ejections of intense steam of charged particles into space, these steams are known as "Solar Wind", upon the interaction of solar winds and our Earth we get auroras which are just the charged particles passing through our magnetic fields, generating electric current that flows to our poles and charges gases, creating light

Life Cycle (After protostar and star formation)

Stars radiate the entire electromagnetic (EM) spectrum which tells us about them

Radio

Microwave

Infrared

Visible

Ultraviolets

X-rays

Gamma rays

>8Ms

Blue Giant

Red Supergiant

Supernova (No more nuclear fusion, Gravity collapses core, chemical composition: To U)

(If >20Ms)

Black Hole (Gravity pulls in on itself, so dense that light can't even escape its gravitational pull)

Neutron Star (Dense, small, rotates incredibly fast)

>10Ms

(1x10^9 years of lifetime, Short life)

Chemical Composition: To Fe

1-8Ms

Yellow Star

Chemical Composition: To C

Red Giant

Planetary Nebula (Outer layers of star expel into space)

Core compresses

Black Dwarf

(1x10^10 years of lifetime, Average life)

<1Ms

Red Dwarf

(1x10^12 years of lifetime, Long life )

H -> He

Heats up due to nuclear fusion (becomes white dwarf)

Black Dwarf (Cools Down)

Ms = Solar Mass (Relative to Sun's Mass)

Types of Stars

Supergiants

Cooler, extremely large, extremely bright

Giants

Cool, large, bright

Main Sequence

90% of all stars

White Dwarf

Dense, hot, small

Formation

Hydrogen Gas + Dust (Nebulae)

Protostar

At 1x10^7°C, Nuclear Fusion occurs

Forces Balance (Gravity Inward, Fusion Outward)

Balance = Stable Star

H -> He (It goes on Depending on the mass of the star)

Nuclear Fusion = Fusion of 2 or more atomic Nuclei

Study of the universe beyond the earth.