AstronomyAstronomy

IntroductionIntroduction

What is Astronomy?What is Astronomy?

The scientific study of celestial (sky/space) objects like stars, comets, planets, and galaxies

Astronomy is NOT astrology

Why study astronomy?Why study astronomy?•The Sun provides our energy to live.•Radiation from the Sun powers our atmosphere and weather.•Earth's spin gives us day and night.•Axial tilt gives us the seasons.•The Sun and Moon cause the tides.•The Moon causes eclipses.•The constellations are used for navigation.•Earth's orbit provides our annual calendar.•The phase of the Moon fixes the date of Easter Sunday.•Ultra violet radiation from the Sun gives us a suntan.•Solar Flares cause the auroras and affect our radio transmissions.•New worlds to explore and colonize

LIFE ON OTHER WORLDS??

Scientific Theory and the Scientific Method

Scientific theories:• Must be testable• Must be continually tested• Should be simple

What can we Observe What can we Observe in the Night Sky?in the Night Sky? Stars Stars

– large spheres of incandescent large spheres of incandescent (glowing) gas(glowing) gas

– Energy comes from nuclear fusionEnergy comes from nuclear fusion– H + H H + H →→ He + energy (e=mc He + energy (e=mc22))– E.g. Polaris, Sun, Betelgeuse, E.g. Polaris, Sun, Betelgeuse,

Procyon, RegulusProcyon, Regulus

ConstellationsConstellations– Regions of spaceRegions of space– 88 regions88 regions– E.g. Ursa Major, Ursa Minor, PegasusE.g. Ursa Major, Ursa Minor, Pegasus– Gemini, Leo, Capricornus, ScorpiusGemini, Leo, Capricornus, Scorpius

AsterismAsterism– Aster = starAster = star– Group of stars that make a patternGroup of stars that make a pattern– Big Dipper, Little Dipper, Big Dipper, Little Dipper,

Great Square, Orion’s Belt, Summer Great Square, Orion’s Belt, Summer TriangleTriangle

GalaxyGalaxy– Cluster of billions of starsCluster of billions of stars– Milky Way- our galaxyMilky Way- our galaxy– Andromeda Galaxy (M31)Andromeda Galaxy (M31)

Spiral Galaxy NGC 4414 -

NebulaNebula– Cloud of gas and dust in spaceCloud of gas and dust in space– M42: Great Nebula in Orion (nursery M42: Great Nebula in Orion (nursery

for stars)for stars)– Eagle NebulaEagle Nebula

Eagle Nebula (M16)Eagle Nebula (M16)

These eerie, dark pillar-like structures are These eerie, dark pillar-like structures are actually columns of cool interstellar hydrogen actually columns of cool interstellar hydrogen gas and dust that are also incubators for new gas and dust that are also incubators for new stars. They are part of the "Eagle Nebula", a stars. They are part of the "Eagle Nebula", a nearby star-forming region 7,000 light-years nearby star-forming region 7,000 light-years away in the constellation Serpens. away in the constellation Serpens.

The picture was taken on April 1, 1995 with The picture was taken on April 1, 1995 with the Hubble Space Telescope Wide Field and the Hubble Space Telescope Wide Field and Planetary Camera 2. Planetary Camera 2.

Dr. Jeff J. Hester, Dr. Paul A. Scowen, Arizona Dr. Jeff J. Hester, Dr. Paul A. Scowen, Arizona State University, STScI/AURA, NASA (1995)State University, STScI/AURA, NASA (1995)

North American North American NebulaNebula(NGC 7000)(NGC 7000)

In Cygnus close to DenebIn Cygnus close to Deneb Emission nebulaEmission nebula Discovered in 1700s by William Discovered in 1700s by William

HerschelHerschel 50 ly across50 ly across About 1500 ly awayAbout 1500 ly away

Horsehead Nebula Horsehead Nebula (Barnard 33)(Barnard 33)

In OrionIn Orion Dark nebulaDark nebula 1500 ly away1500 ly away 3.5 ly across3.5 ly across Discovered Discovered

18881888

Ring Nebula (M57)Ring Nebula (M57)

In LyraIn Lyra Planetary Planetary

nebulanebula 2000-2500 2000-2500

ly awayly away

Forms when star blows off Forms when star blows off gas- white dwarf star left gas- white dwarf star left behindbehind

Crab Nebula Crab Nebula (M1, NGC 1952)(M1, NGC 1952) In TaurusIn Taurus Remnant of Remnant of

supernova observed supernova observed by Chinese in 1054by Chinese in 1054

Hubble Space Telescope Hubble Space Telescope image of the Crab Nebula. image of the Crab Nebula. High-energy particles High-energy particles accelerated by the Crab accelerated by the Crab pulsar, a neutron star pulsar, a neutron star spinning with a period of spinning with a period of 33 ms at the center of the 33 ms at the center of the remnant, cause the bluish remnant, cause the bluish glow of the interior. The glow of the interior. The outer filaments are the outer filaments are the tattered remains of the tattered remains of the star and consist mostly of star and consist mostly of hydrogen. hydrogen.

http://www.mpa-garching.mpg.de/~thj/popular/Crab_Nebula.jpg

PlanetsPlanets

Bodies that revolve around the Bodies that revolve around the SunSun

Have enough gravity to make Have enough gravity to make themselves roundthemselves round

Cleared out the region in their Cleared out the region in their orbitorbit

Eight planetsEight planets

MercuryMercury VenusVenus EarthEarth MarsMars JupiterJupiter SaturnSaturn UranusUranus NeptuneNeptune

Could there be more planets that we Could there be more planets that we cannot see?cannot see?

Dwarf PlanetsDwarf Planets

PlutoPluto Far from the SunFar from the Sun Not roundNot round ‘‘Kuiper Belt objects’Kuiper Belt objects’

CometsComets

Orbit the Sun in eccentric pathsOrbit the Sun in eccentric paths ‘‘dirty snowballs’dirty snowballs’ E.g. Halley (1910, 1986, 2061)E.g. Halley (1910, 1986, 2061)

AsteroidsAsteroids

Large chunks of rockLarge chunks of rock Live between Mars and JupiterLive between Mars and Jupiter Largest: CeresLargest: Ceres

MoonsMoons

Satellites of a planetSatellites of a planet (the planet is the ‘primary’- it (the planet is the ‘primary’- it

goes around the Sun)goes around the Sun)