AstronomyAstronomy is the scientific study of stars, planets and other things in space.

Origins of the Universe1. Creationism – universe is

created by a deity or spirit, anchored on holy books

2. Big Bang Theory – primordial explosion that created the universe (primordial atom)

3. Steady State Theory – the universe has always been as it is today

Planetary Nebula or Close Encounter?

Historically, two hypothesis were put forward to explain the formation of the solar system….

1. Gravitational Collapse of Planetary Nebula (Latin for “cloud”)

Solar system formed form gravitational collapse of an interstellar cloud or gas

2. Close Encounter (of the Sun with another star)Planets are formed from debris pulled out of the Sun during a close encounter with another star. But, it cannot account for• Probability for such encounter is small in our neighborhood…

The Nebular Theory* of Solar System Formation

Interstellar Cloud (Nebula)

Protoplanetary DiskProtosun

Gravitational Collapse

Terrestrial

Planets

Accretion Nebular Capture

Jovian PlanetsAsteroids

Leftover Materials Comets

Leftover Materials

Metal, Rocks

Condensation (gas to solid)

Sun Gases, Ice

Heating Fusion

*It is also called the ‘Protoplanet Theory’.

A Pictorial History

Gravitational Collapse

Accretion Nebular Capture

Interplanetary Cloud Condensation

The Interstellar Clouds

• The primordial gas after the Big Bang has very low heavy metal content

• The interstellar clouds that the solar system was built from gas that has gone through several star-gas-star cycles.

Solar System

What’s in Our Solar System?

• Our Solar System consists of a central star (the Sun), the nine planets orbiting the sun, moons, asteroids, comets, meteors, interplanetary gas, dust, and all the “space” in between them.

• The nine planets of the Solar System are named after Roman Gods and Goddesses.

Models of the Solar System1. Geocentric model - earth is the

center; proposed by Ptolemy

Models of the Solar System2. Heliocentric model - sun is the

center; proposed by Copernicus

The Relative Size of the Planets in the Solar System

Solar SystemSun – yellow star; driven by thermonuclear fusion, by which hydrogen nuclei fuse to form heliumi. Photosphere – surfaceii. Sunspots – cooler and

darker portion on the Sun’s surface

iii.Chromosphere – sphere of color, seen during eclipse

iv.Corona – outermost region

Chromosphere Prominences

Sun Spots

The Sun actually moves!

Rotation: The Sun spins around one time every 25 days.Revolution: The Sun moves around the center of our galaxy one time every 200,000,000 years!

Our Differing Distances from the Sun

A.Aphelion – when the Earth is far away from the sun, about 152 million km away

B.Perihelion – when the Earth is closest to the sun, about 147 million km away

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Equinox & SolsticeEquinox  is when daylight time is equal to night time.Solstice is when daytime or night time is longer than the other; may be winter, when night time is longer, or summer when daytime is longer.

General Characteristics of Major Planets - Dynamical

• Nearly circular orbits (Mercury and Mars most eccentric)

• All orbit within 10o of Earth’s orbital plane

General Characteristics of Major Planets•All revolve in the same direction• All rotate in the same direction (except Venus)

Solar SystemPlanets1. Inner planets (terrestrial

planets) - composed primarily of rock and metal; have relatively high densities; slow rotation; solid surfaces; no rings

2. Jovian planets (gas planets) - composed primarily of hydrogen and helium; have low densities; rapid rotation; deep atmospheres; rings

Mercury• Mercury has a revolution

period of 88 days. Mercury has extreme temperature fluctuations, ranging from 800F (daytime) to -270F (nighttime).

• Even though it is the closest planet to the sun, Scientists believe there is ICE on Mercury! The ice is protected from the sun’s heat by crater shadows.

• Messenger of gods

Venus• Venus is the brightest

object in the sky after the sun and moon because its atmosphere reflects sunlight so well. People often mistake it for a star.

• Its maximum surface temperature may reach 400C.

• Venus has no moons • Greenhouse Model• “The Morning Star”• Goddess of Beauty

Earth• Earth is the only planet

known to support living organisms.

• Earth’s surface is composed of 71% water.– Water is necessary for life

on Earth.– The oceans help maintain

Earth’s stable temperatures.

• Earth has one moon and an oxygen rich atmosphere.

Motion of the Earth

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Rotation Revolution

The MoonThe Moon is the Earth’s only natural satellite.Ancient man feared the moon - thought it made a person crazy!1609, Galileo was the 1st person to fully examine the moon through a telescope.The moon is about a ¼ of the size of Earth.Rotation: 27 1/3 daysRevolution: 27 1/3 days

The MoonGreat Impact Theory – moon is the result of the collision of a huge rocky mass the size of planet Mars with the Earth about 20 million years after the Earth had formed; the collision formed a ring of clouds and rock fragments from both bodies around the Earth until by gravity it formed the Moon

This shows the craters and the smooth areas on the moon.

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Q&AQ: 1. Can a full Moon be seen at noon? 2. Can a new Moon be seen at midnight?

A: Both, no. You would be on the wrong side of Earth to view the full moon and the new moon.

Eclipse: Solar

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• Moon’s shadowfall on the earth

• During new moon

Eclipse: Lunar

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• Earth’s shadow fall on the earth

• During full moon

• Like Earth, Mars has ice caps at its poles.

• Mars has the largest volcano in our solar system: Olympus Mons.

• Mars appears red because of iron oxide, or rust, in its soil and an atmosphere of CO2

• Mars has two moons (Phobos & Deimos) and takes about two years to complete an orbit.

• Probes: Curiosity, Opportunity, Spirit

Mars

Jupiter• Jupiter is the largest

and most massive planet.

• Diameter is 11 times bigger than that of the Earth’s.

• Takes about 12 years for Jupiter to orbit the sun.

• Jupiter has 16 well-known moons. Four famous moons: Ganymede, Calisto, Io, & Europa

• “Great Red Spot”

Saturn • Saturn is composed almost entirely of hydrogen and helium

• Saturn has many rings made of ice and rocks. Saturn’s rings are very wide.

• It takes Saturn about 30 years to orbit the sun.

• Saturn has 62 known moons (Titan & Enceladus, being the largest) composed largely of ice, some of which orbit inside the rings!

• Named after the Roman god of agriculture

Uranus• Uranus is blue in color due

to methane gas in its atmosphere.

• Uranus has 11 dark rings surrounding it.

• Uranus has 27 known moons (Titania, Oberon, Umbriel, Ariel, & Miranda) and takes 84 years to complete one orbit.

• Tilted by over 90 degrees• Named after the Roman

god of the sky

Neptune• Neptune has the

fastest winds in the solar system: up to 2,000 km/hr.

• Neptune is also blue in color due to methane gas in its atmosphere.

• takes 165 years to orbit the sun and has 14 moons, Triton is one of the known moons

• “Great Dark Spot”• The god of the sea

Pluto• Pluto has only one moon and

takes about 249 years to orbit the sun.

• Part of Pluto’s orbit passes inside that of Neptune, so at times Neptune is the planet farthest from the sun.

• Pluto was located and named in 1930, but today Pluto is no longer considered a planet.

• New Horizon fly-by

Dwarf Planet/ Kuiper Belt Object/

Dwarf PlanetPluto – 1930-2006 classified as major planet; its famous moon is named CharonReasons why it is not one of the major planets:1. Most often located in Kuiper Belt Region2. Orbit is highly elliptical & steeply inclined to

the planetary plane3. Composition does not match any of the other

planets, but is a near-perfect match to objects in Kuiper Belt

Quantitative Planetary Facts

Comets• Comets are small bodies typically only a

few kilometers across, composed largely of volatile ices.

• Have highly eccentric orbits• Known to have a coma and a “tail”

– Perseids (July 23- Aug 20)– Orionids (Oct 16-27)

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The Milky Way GalaxyThe Milky Way is the galaxy that contains our Solar System. Its name "milky" is derived from its appearance as a dim glowing band arching across the night sky whose individual stars cannot be distinguished by the naked eye. 

Our galaxy is called the Milky

WayOur WHOLE solar

system is located right about here

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Galaxies – group of star and solar systems

Galaxies vary in shape:•Spiral•Andromeda Galaxy

•Ring•Hoag’s Object

• Irregular

Stars go through four different stages in their lifetime.

The four stages are:1.Yellow Star2.Red Giant3.White Dwarf4.Black Dwarf

• Medium-Hot star. Nuclear reaction occurring

• Our “Star” (sun) is a yellow star.

•As nuclear fuel is used up, star expands and turns red

•Lasts for about 100 million years

•When our sun is a Red Giant, it will expand and swallow up the inner planets—Mercury, Venus, Earth & Mars

•Most of the stars fuel in the outer layers is used up

•Shrinks and collapses (about the size of Earth but heavier)

•Gives off a white light

•Remaining fuel is used up•Star is dead

The universe is made up of millions

of Galaxies.A galaxy is a swarm of billions of stars, clouds and dust rotating

around a central point.

Stars & Constellations•Constellations are group of stars. Zodiac is based from these constellations.•Nearest Star from the Sun is the Proxima Centauri•Brightest Star is Sirius of Canis Major•Most common constellation and star are the “Ursa Minor” and the Northern Star “Polaris” of the Ursa Minor, respectively.•Largest known star is the VY Canis Majoris

Supernova & Black holeSupernova  is a large explosion that takes place at the end of a star's life cycle. Black hole  is a region of space-time exhibiting such strong gravitational effects that nothing can escape from inside it.

Lunar Missions•Lyka was the first animal sent in the space, to orbit the Earth.•The first successful manned mission to the moon. (Apollo 11)•Astronauts Neil Armstrong and Buzz Aldrin were the first men on the moon, (July 16, 1969, 8:18 PM)•Astronauts = NASA, Americans•Cosmonauts = USSR, Soviets

Due to the extreme conditions on the moon astronauts must

were a suit like this.

This shows the surface of the moon

Little Astronaut

And away we go!

The Astronomical UnitsOften planets’ distance from the Sun

is measured by ASTRONOMICAL UNITS.

This is the relative distance of the Earth from the Sun. SO when we say 2 Astronomical Units, it means twice the distance of Earth from the Sun.

Light-year The distance that light travels in one year, about

9.5 trillion kilometers.

Parsec: A unit of measurement used to describe distances

between celestial objects, equal to 3.258 light-years.

Important Astronomical Measurements