Astronomy Earth, Moon, and Sun

Days and Years Astronomy: the study of moon, stars, and other objects in space Rotation: the spinning of Earth on its axis, this takes 24 hrs This causes day and night Revolution: the movement of 1 object around another; 1 revolution = 1 year Orbit: Earth’s path as it revolves around the sun, its shape is elliptical (egg shaped)

Season on Earth Earth has seasons because its axis is tilted as it moves around the sun Summer occurs in the hemisphere leaning towards the sun because the sun’s rays are striking it most directly

Longest and Shortest Days Solstice: when the sun is directly over head 23.5° N or S. It is either the longest (summer) or shortest (winter) day of the year Equinox: (equal night) sun is directly over the equator and day and night are equal

Motions of the Moon The moon revolves around the Earth AND rotates on its own axis every 27.3 days. This means that a lunar day is the same length as a lunar year!! As a result, we always see the same side of the moon, that we call the near side

Motions of the Moon The moon’s orbit is an ellipse (egg shape) just like the Earth’s Perigee – when the moon is closest to Earth Apogee – when moon is farthest from Earth

Motions of the Moon

Phases of the Moon The phase of the moon you see depends on how much of the sunlit side of the moon faces Earth The lunar cycle, full moon to full moon, is 29.5 days

Structure of the Moon The Moon’s diameter is ¼ of the Earth’s In relation to the planet it orbits, it is the largest moon in our solar system

Features of the Moon Craters: round pits on the moons surface caused by the impacts of meteors

Features of the Moon Maria: dark flat regions on the moons surface that were once lava flows Highlands: high areas on the moon

Eclipses Lunar Eclipse: when the Earth is directly between the sun and the moon preventing the sunlight from hitting the moon Solar Eclipse: when the moon is between the sun and the Earth preventing the sunlight from hitting Earth Occurs at full moon Occurs at new moon

Eclipses Umbra – the darkest part of a shadow Penumbra – the larger part of the shadow surrounding the darkest part Solar eclipse Lunar Eclipse

Tides Tides: the rise and fall of water level in the oceans What causes tides? Tides are a result of differences in how much the moon’s gravity pulls on different parts of the Earth

Types of Tides There are 2 high tides and 2 low tides each day (25 hour cycle) Neap Tide: smallest tide, least difference between high and low tide. Moon phase first and last quarters. Spring Tide: when there is the greatest difference between high and low tide. When moon is in new or full phase

Tides

Origin of the Moon Collision theory: AKA – Giant Impact Theory - states that the moon formed when an object from space collided with Earth, throwing large chunks of Earth into space which then condensed to form the moon

Satellites Satellite: any natural or artificial object that revolves around an object in space. Is the moon a satellite? YES! Geosynchronous: they revolve around earth at the same rate earth rotates, so they stay over the same place

Chapter 2 The Solar System

Observing the Solar System Geocentric: the theory that the Earth is the center of the solar system, supported by Ptolemy (Greek astronomer) WRONG!

Observing the Solar System Copernicus Galileo Heliocentric: theory that the Sun is the center of the solar system proposed by Copernicus and proved by Galileo (who was subsequently put under house arrest)

Observing the Solar System Johannes Kepler (German mathematician) analyzed Tycho Brahe’s (Danish astronomer) planetary observations and calculated that planet’s orbits are elliptical Brahe Kepler

Observing the Solar System Isaac Newton concluded that inertia and gravity combine to keep planets in orbit.

Observing the Solar System Inertia: the tendency of a moving object to keep moving in a straight line or a stationary object to remain in place. Gravity: the attractive force between 2 objects; depends on the masses and distance between the 2 objects

Rockets Newton’s 3rd Law: For every action there is an equal and opposite reaction This law demonstrates how rockets are launched into space

The Sun’s interior The sun’s interior is like a giant furnace producing energy through nuclear fusion nuclear fusion: the process of combining 2 hydrogen nuclei fusing to form helium Nuclear fusion occurs in the sun’s core where the temperature is 15 million degrees Celsius NASA - The Composition of the Sun

The Sun’s Atmosphere The sun’s atmosphere has 3 layers: Photosphere: inner layer of the sun’s atmosphere where light is produced and what we see when we look at the sun Chromosphere: middle layer of the sun’s atmosphere Corona: outer layer of sun’s atmosphere only visible during solar eclipses

Features of the Sun Solar wind: stream of electrically charged particles sent out from the corona, causes the aurora borealis Sunspot: areas of gas on the sun’s surface that are cooler than the surrounding areas

Sunspots

Features of the Sun Prominence: reddish loops of gas that link different areas of sunspots

Features of the Sun Solar flares: an explosion of hydrogen gas that results when prominences connect Solar flares video

Mercury Closest to sun No moons No atmosphere Sky is black 450°C during the day and -170°C at night Image:http://www.nasa.gov/worldbook/mercury_worldbook.html

Venus Similar in size to Earth Revolution (1 yr) = 7.5 months Rotation (1 day) = 8 months Rotation is retrograde which means it rotates in the opposite direction or from east to west

Venus Atmosphere is thick and full of carbon dioxide resulting in a strong greenhouse effect As a result Venus is actually hotter than Mercury, its surface is 460°C, hot enough to melt lead! Surface of Venus

Mars The red planet Thin atmosphere is mostly carbon dioxide Has an ice cap at its north pole Has a tilted axis like Earth so it has season It has 2 moons: Phobos and Deimos

The Outer Planets Jupiter, Saturn, Uranus, and Neptune are known as the “gas giants” because they are much larger than Earth and do not have solid surfaces. The composition of their extremely thick atmospheres is similar to the gases in the sun Astronomers think they may have solid cores made of rock, ice, and frozen carbon dioxide

Jupiter Largest planet Thick atmosphere made of hydrogen and helium

Jupiter Has the Great Red Spot, a hurricane like storm Has 50 confirmed moons & 17 provisional ones Moons: Io, Ganymede, Callisto, and Europa Jupiter and its moon Io

Saturn 2nd largest planet Has very large rings made of dust and ice Has 53 satellites including Titan which has an atmosphere

Saturn Saturn orbits the sun once every 29 years Its winds blow up to 1600 ft/s

Uranus Twice as far from the sun as Saturn Discovered by William Herschel in 1781 It takes 84 Earth years for it to orbit the sun It has 27 moons Farthest planet that can be seen without a telescope

Uranus Looks bluish because of the traces of methane in its atmosphere Its axis is tilted 90° from vertical so it rotates from top to bottom

Neptune Featureless blue atmosphere with some visible clouds 30x farther from the sun than Earth 165 Earth years to orbit the sun

Neptune It has several rings 13 moons including Triton, which is the only 1 known to orbit in the opposite direction as its planet

Dwarf Planet - Pluto discovered in 1930 and long considered to be the ninth planet From 1979 to 1999, Pluto was actually closer to the Sun than Neptune

Dwarf Planet - Pluto May be the largest of icy objects just beyond Neptune called the Kuiper Belt Has 5 moons

Comets Comets: chunks of ice and dust whose orbits are usually long narrow ellipses Comets get their name from the Greek word "kometes" (long hair)

Asteroids Largest space rocks that revolve around the sun that are too small and too numerous to be considered planets

Asteroids Asteroids are made up of rock and iron Most are found between Mars and Jupiter in the Asteroid Belt

Meteoroid a chunk of rock or dust in space that usually come from comets or asteroids Meteoroids orbit our Sun just like asteroids and planets

Meteorite a meteoroid that passes through Earth's atmosphere and hits Earth's surface

Meteor A meteoroid that enters Earth's atmosphere and burns up

Stars, Galaxies, and the Universe

Tools of Modern Astronomy Electromagnetic Radiation: a form of energy (including light) that can travel through space in waves Visible light: light we can see with our eyes (ROYGBIV = spectrum, or colors, of visible light) Longest wavelengths:radio, infrared waves Shortest: Ultra violet, x-rays, gamma rays

Tools of Modern Astronomy Visible Light Telescopes: produce images using visible light Refracting Telescopes: Uses convex lenses to gather and focus light Reflecting Telescopes: uses 1 or more mirrors to gather light Radio Telescope: a device used to detect radio waves (electromagnetic radiation) in space Others use infrared radiation, UV rays, x-rays, and gamma rays

Tools of Modern Astronomy Observatory: a building that contains 1 or more telescope Constellation: patterns of stars in the sky Satellites: Telescopes are placed on satellites because most electromagnetic radiation is blocked by our atmosphere Hubble space telescope

Tools of Modern Astronomy Spectrograph: breaks light from an object into colors and photographs the resulting spectrum Astronomers use spectrographs to get info about stars including their chemical composition and temperatures

Characteristics of Stars Universe: all space and everything in it Galaxy: A giant structure that contains hundreds of billions of stars Light year: the distance that light travels in 1 year = 9.5 trillion Km (light speed = 300,000 Km/s)

Characteristics of Stars Parallax: is the apparent change in the position of an object when you look at it from different places. Astronomers use parallax to measure distance to nearby stars

Characteristics of Stars The main characteristics used to classify stars are: size temperature brightness

Characteristics of Stars A stars color reveals its temperature blue stars are the hottest and red the coolest How bright a star looks from earth depends on 2 things: how far it is from earth how bright it actually is

Characteristics of Stars Apparent magnitude: a stars brightness as seen from Earth (how bright it appears to be) Absolute Magnitude: the actual brightness of a star

Characteristics of Stars Hertzsprung-Russell Diagram: a graph relating the temperature and brightness of stars Main sequence stars: 90% of all stars, where as surface temperature increases brightness increase (like our sun)

Birth of Stars Stars begin life in a nebula

Birth of Stars As gravity pulls the gas and dust of the nebula together a protostar is formed A star begins life when it is hot enough that nuclear fusion begins **How long a star lives depends on how much mass it has; small stars burn their fuel more slowly than large stars

Deaths of stars When a star runs out of fuel it becomes a white dwarf, a neutron star, or a black hole White dwarf: small and medium stars become red giants and then when they run out of fuel become white dwarfs, when it stops glowing it is dead and is called a black dwarf

White dwarf

Deaths of stars Neutron star: a giant or super giant star can explode causing a supernova The material that is left over from the explosion becomes a neutron star which are smaller and denser than white dwarf podcast

Deaths of stars Black Hole: the remains of the most massive stars collapse into black holes

Star Systems and Galaxies More than half of stars are members of groups of 2 or more stars called star systems Binary stars: stars systems with 2 stars (75% of all stars) Eclipsing binary: a star system in which one star periodically blocks the light from another

Star Systems and Galaxies Planets around other stars 51 Pegasi was the 1st found So far we have only been able to detect very large planets - “Goldilocks conditions” – Conditions (size, distance from the sun etc.) that are “just right” to support life or for life to evolve

Star Systems and Galaxies 4 main types of galaxies: Spiral: these have arms that radiate outward like pinwheels (milky way) Elliptical: these look like flattened balls, contain billions of stars, and have little gas and dust between the stars Irregular: galaxies without a regular shape Lenticular – smooth disc galaxies of older stars, they have used up the material between the stars

History of the Universe Big bang: the initial explosion that resulted in the formation and expansion of the universe According to this theory, the universe formed 10-15 billion years ago The universe is always expanding: Edwin Hubble discovered that the galaxies are moving away from each other Our solar system and sun were formed about 5 billion years ago