The study of the universe beyond the Earth’s atmosphere Astronomy The study of the universe beyond the Earth’s atmosphere

What is Astronomy Astronomy is the study of the Universe, the stars, planets and all other objects in space.

How are Distances Measured in Space? Astronomical Unit (AU) is the distance from the Earth to the Sun. 1 AU = ~86,000,000 miles Light Year (LY) is the distance that light travels in one year. 1 LY = ~6 trillion miles

What is a Galaxy? Galaxy = a large group of stars, (billions), gas and dust held together by gravity.

Three Types of Galaxies Elliptical Galaxy Spiral Galaxy Irregular Galaxy

Elliptical Galaxies Elliptical galaxies = are groups of stars that appear to be shaped like an ellipse (football)

Irregular Galaxies Irregular galaxies = are groups of stars that appear to be together but have no regular shape. The Large and Small Megelanic Clouds are examples of irregular galaxies.

Irregular Galaxy

Spiral Galaxies Spiral galaxies = are groups of stars that appear to have a dense concentration of stars in the center and arms that are made of stars and dust. Ex: Milky Way and Andromeda Galaxies

Barred Spiral Galaxy A “Barred” Spiral galaxy looks similar to a spiral galaxy with a “bar” of stars through the center and the arms extend outward from the ends of the “bar”.

Milky Way Galaxy Our Sun is just one of billions of stars in the Milky Way Galaxy. The Milky Way Galaxy is thought to be 100,000 LY in diameter and 15,000 LY thick.

Clusters As stars are grouped into galaxies, galaxies are grouped into clusters. Our cluster is called the “Local Group”

So Where in the Universe Are We? The astronomical address for Earth would be: Earth is the 3rd planet in the solar system of the star called the Sun, which is in the Milky Way Galaxy, of the Local Group of galaxies in the Universe.

What is our Sun? Our Sun is an average star of yellow-orange classification.

Layers of the Sun The sun is composed of several layers. Core Radiative zone Convective zone Corona Photosphere Chromosphere

The Core The core of the Sun is the place where fusion of atoms is taking place. Fusion generates temperatures of 10,000,000 oC Our sun is fusing hydrogen atoms into helium

The Corona Corona = the outer layer of the sun. This is the gradual boundary between the sun and space. This is what we see during an eclipse.

The Photosphere Photosphere = the layer of the sun that is incredibly bright and the source of much of the light we see on earth.

The Chromosphere Chromosphere = is an active layer of the sun that is where the magnificent displays of prominence and flares take place.

Prominence / Solar Flares Prominence / Flares are bright spots on the sun formed as gas particles shoot outward from the sun. These affect the magnetic fields on earth (radio, television, communications). These also cause the Northern Lights or “Aurora Borealis”.

Aurora Borealis – “Northern Lights”

Northern Lights

Sunspots Sunspot = a dark, cooler spot on the surface of the sun. The sunspot cycle is a pattern of high sunspot activity and lower activity . ~11 year cycle for our Sun The dark central portion is called the umbra 4,300 0K

What is the Solar System? The Solar System is: the Sun, the eight planets and their natural satellites, the asteroids, the comets and the meteoroids.

Formation of the Solar System Our solar system formed about 4.5 - 5 billion years ago from a giant cloud of gas and debris. Planets were formed by the accumulation of material in the solar nebula. The type of planet that forms depends upon conditions existing at that distance from the star; such as temperature and material present.

What is a planet? Planet = a massive collection of matter that revolves around a celestial body, or star.

The Eight Planets Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto has recently been classified as a “dwarf planet”

Planets are divided into two categories Jovian or Gaseous Giants are “gaseous” planets that are big, low density, “cold” and have many moons: Jupiter Saturn Uranus Neptune Terrestrial Planets are “land-based” planets that are solid, dense, “hot” and have few moons: Mercury Venus Earth Mars Dwarf Pluto

Mercury 57.9 million km from Sun 88 day period of revolution 59 day period of rotation 0.206 eccentricity of orbit 4,880km diameter 0.553 mass of Earth Density of 5.4 g/cm3 No moons

Venus 108.2 million km from Sun 224.7 day period of revolution 243 day period of rotation 0.007 eccentricity of orbit 12,104 km diameter 0.815 mass of Earth Density of 5.2 g/cm3 No moons

Earth 149.6 million km from Sun 365.26 day period of revolution 23hr 56min 4sec period of rotation 0.017 eccentricity of orbit 12,756 km diameter 1.00 mass of Earth Density of 5.5 g/cm3 1 moon

Mars 227.9 million km from Sun 687 day period of revolution 24hr 37min 23sec period of rotation 0.093 eccentricity of orbit 6,787 km diameter 0.1074 mass of Earth Density of 3.9 g/cm3 2 moons

Jupiter 778.3 million km from Sun 11.86 year period of revolution 9hr 50min 30sec period of rotation 0.048 eccentricity of orbit 142,800 km diameter 317.896 mass of Earth Density of 1.3 g/cm3 16 moons

Saturn 1,427 million km from Sun 29.46 year period of revolution 10hr 14min period of rotation 0.056 eccentricity of orbit 120,000 km diameter 95.185 mass of Earth Density of 0.7 g/cm3 18 moons

Uranus 2,869 million km from Sun 84.0 year period of revolution 17hr 14min period of rotation 0.047 eccentricity of orbit 51,800 km diameter 14.537 mass of Earth Density of 1.2 g/cm3 21 moons

Neptune 4,496 million km from Sun 164.8 year period of revolution 16hr period of rotation 0.009 eccentricity of orbit 49,500 km diameter 17.151 mass of Earth Density of 1.7 g/cm3 8 moons

Earth’s Moon 149.6 million km from Sun (0.386 from Earth) 27.3 day period of revolution 27 day 8hr period of rotation 0.055 eccentricity of orbit 3,476km diameter 0.0123 mass of Earth Density of 3.3 g/cm3

Dwarf Planet A dwarf planet is an object within the Solar System that meets four criteria: is in orbit around the Sun has sufficient mass to become spherical (hydrostatic equilibrium) has not cleared it’s orbital neighborhood is not a satellite

Pluto Examples of dwarf planets are Ceres which is the largest asteroid in the Asteroid Belt, Pluto which is in the Kuiper Belt, and Eris which is beyond the Kuiper Belt.

The Kuiper Belt The Kuiper Belt is a region of the solar system which begins beyond the orbit of Neptune and is 3 – 5 trillion miles wide. The Kuiper Belt consists of small objects composed largely of ices, such as methane, ammonia and water. The Kuiper Belt is consisdered the source of many comets.

Other Objects in the Solar System Other objects in the solar system include: Comets Asteroids Meteoroids

Asteroids Asteroid = a large chunk of rock traveling through space. Most, not all, are found in the Asteroid Belt located between Mars and Jupiter.

What is a Comet? A Comet is a large chunk of ice, dust, frozen gas and rock fragments that moves through space.

Most comets have very elongated orbits around the Sun Comets form in an icy cloud, called the Oort Cloud, as the gravity of a passing star pulls material out of the cloud. Most comets have very elongated orbits around the Sun

Comets Have Two Tails The Ion Tail always points away from the sun The Dust Tail is left behind in the comets path

Halley’s Comet

Comet - Liner

Meteoroid, Meteor, Meteorite Meteoroid = a small pieces of rock moving through space. Meteor = a small pieces of rock moving through space (a meteoroid) that enters Earth’s atmosphere. Meteorite = a small pieces of rock moving through space that hits the Earth.

Perseid Meteor Shower

Meteor Showers Meteor showers are very likely from the debris left behind by a comet that passed at an earlier time. Perseids – August 10-14 Orionids – October 18-23 Taurids – November 1-15 Geminids – December 10-16

Impact Events Most material reaching the Earth’s surface is very small, however there is evidence of comets hitting Earth in the past. If large meteoroid fragments collide with the surface then the result is an impact crater. Example is Barringer Crater in Arizona which is 1.2km across and 200m deep. Est. object size = 50m at 25,000 mph

Asteroid approaching Earth

Asteroid Impact