A Quick Survey of the Solar System

A Quick Survey of the Solar System

Size and Distance…

12 inches

If we model the Earth as a 12-inch globe, then the Solar System to scale would look like…

The Sun and the Planets to Scale:

• The Sun would be larger than a BIG house.

• Jupiter would be over 11 ft. across.

• Pluto would be only 2 in. across.

And the distances can be compared to New York State:

SUN

PLUTO comets

ERIS

At the center of it all: THE SUN!

The planets can be divided into two groups:

The Earth-like or the terrestrial planets, which include Mercury, Venus, Earth, and Mars.

The Terrestrial Planets • Are small in size (less than 8000

miles across).• Are composed mostly of solid rock.• Have thin atmospheres compared to

the giant planets.• Are relatively close to the Sun.

The second group of planets are gas giants called the Jovian planets after Jupiter.

THE JOVIAN PLANETS:

• Are very large compared to the terrestrial planets.

• Are composed mostly of dense gases or ices.

• They include Jupiter, Saturn, Uranus, and Neptune.

• All these planets have rings.

Mercury• Mercury is the closest planet to the sun, only

0.39 AU away.• It revolves around the Sun in just 88 days.• It looks a lot like the Moon (cratered).• Temperatures range from very hot to very cold.

Animation

VENUS

• Venus has an atmosphere with thick clouds.

• Venus is almost the same size as Earth.

• Heat trapped by the atmosphere makes Venus a very hot world!

A Venus Transit Across the Sun

EARTH• Earth is the largest

terrestrial planet.• It is the only planet with

significant amounts of oxygen in the atmosphere and water in the liquid state.

• The Earth is a very active planet, tectonically.

Mars• The reddish color is

caused by iron oxide (rust).

• Mars has about the same rotation rate as Earth.

• Mars has ice caps and seasons.

• The largest known volcano in the Solar System is found on Mars.

Jupiter• Jupiter is larger than all

the other planets combined.

• The Great Red Spot is a huge storm on Jupiter’s surface.

• One day on Jupiter is only 10 hours, causing the planet to have a oval shape.

• The four largest moons of Jupiter are named for Galileo.

The Galilean Satellites: Io, Europa,

Ganymede, and Callisto

Saturn• The rings of Saturn are

made of billions of small particles.

• Saturn has a very low density. It could float in water, if you could find a sea big enough.

• Some of the moons of Saturn have conditions that might allow living organisms.

Uranus• Uranus was the first

planet discovered using a telescope in 1787.

• It was the second planet found to have rings.

• It is one of the “ice planets” along with Neptune.

• Uranus is tilted on its side, so it has extreme seasons.

NEPTUNE• Neptune is over 30

times farther from the Sun than Earth.

• It was discovered when Uranus’ orbit was slightly off predictions.

• Unlike its “twin”, Neptune is not tilted much.

Pluto• Pluto is smaller than the

Moon. • It has the most elliptical and

tilted orbit of all previously known planets.

• Its origin is a major debate among astronomers. It was demoted to the category of dwarf planet in August 2006.

• Its companion is called Charon.

• Charon ‘s status is still unclear according to the IAU.

Eris - a Dwarf Planet

• In the summer of 2005 a tenth “planet” was identified with an orbit averaging 68 A.U. from the Sun.

• Its orbit is very eccentric and inclined.

• The International Astronomical Union has decided that ”Eris” is the largest known dwarf planet.

MakemakeMakemake• Another dwarf planet

was discovered in 2005.

• This past year it was named “Makemake” in honor of a Polynesian god.

• It has a highly eccentric and tilted orbit, averaging around 45 AU from the Sun.

Sedna - Way, Way, Out!

Pluto is Dissed!

• In the mid-1990s the Hayden Planetarium in NYC was renovated.

• Their new exhibit left out Pluto, which set off a major media storm.

• This led to a reclassification of solar system objects (and a lot of angry elementary teachers).

What then What then isis a planet? a planet?• In a very controversial

vote on Aug. 24, 2006, the IAU stated that there are only eight classical planets.

• Pluto, Makemake, Eris, and Ceres are considered to be dwarf planets.

• There are probably many more dwarf planets waiting to be discovered.

• The IAU therefore resolves that planets and other bodies in our Solar System be defined into three distinct categories in the following way:

• (1) A planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.

• In plain language, if it's round and it orbits the Sun, and it doesn’t cross another orbit then it's a planet.

The Official Definition…

The Dwarf PlanetsThe Dwarf Planets• The IAU also defined a

new category of bodies revolving around the sun, the dwarf planets.

• They are similar to classical planets, except “they have not cleared the neighborhood around its orbit.”

• Then in 2008, a subcategory was created…plutoids, dwarf planets beyond Neptune.

Ceres - dwarf planet, but not a plutoid

Small Solar System Bodies

• Small Solar System Bodies are too small and irregular in shape to be true planets.

• “SSSBs” include natural satellites, asteroids, meteoroids, and comets.

• Satellites (or “moons”) revolve around planets as they revolve around the Sun.

• Some of the satellites of Mars, Jupiter and Saturn are probably captured asteroids. Deimos and Phobos

The Asteroids• Asteroids are mini-

planets found mostly between Mars and Jupiter.

• The rock fragments never managed to coalesce, so they have irregular shapes (i.e. they are NOT planets).

• Their orbits are often highly eccentric and inclined.

Jupiter

Mars

The Asteroid Belt

The Dawn Mission to the Asteroid Belt

Meteoroids• Meteoroids are small

rocky fragments, probably left over from the formation of the Solar System.

• When they enter the earth’s atmosphere, they start to burn, creating meteor showers. If it reaches the ground, it is called a meteorite.

FireballFireball

Comets• Comets are balls of rock

and ice, usually no more than a few miles across.

• Their orbits are very elliptical, taking them way past the orbit of Pluto.

• When they approach the Sun, a tail of gases forms, always pointing away from the Sun.

• Sometimes the heat of the sun causes the comet to begin to disintegrate, such as Comet West.

Orbit of a typical comet…

Earth

Pluto

Comet orbit

P = 100,000 yrs.

Many comets come from a distance region of the Solar

System called the Oort Cloud.

Pluto’s orbit

1 light-year

These minor objects can enter the Earth’s atmosphere, usually doing little damage.

In rare instances, they can produce impact craters.

Origin of the Solar System

Around 5 billion years ago, a huge cloud of gas (left over from an ancient supernova) began to shrink and rotate.

Most of the matter fell to center, producing the Sun.

The outer rings became the planets. Those near the sun lost most of their gases (terrestrial planets).

Those farther out kept their thick atmospheres and icy cores

Jovian Planets

One of Jupiter’s moons

The “Goldilocks” Solar System

The Solar System appears to be stable, but there is still much violent uncertainty.

Shoemaker Levy

Olympus Mons

Io

Enceladus

Target Zero: EARTH • There seems to be a

major collision with asteroids or comets every 25 million years.

• One major impact hit the Yucatan Peninsula and might have caused the extinction of the dinosaurs.

• In 1908 an asteroid exploded above Tunguska, Siberia.

• Is it only a matter of time before Armageddon II?

A Near Miss in Feb. 2009

2009 - Jupiter Gets Slammed Again!

Quick QuizQuick Quiz• What are the differences between the

terrestrial and Jovian planets?• What is meant by a dwarf planet?• Name an usual property for each planet.• What are the three Small Solar System

Bodies in the Solar System?• What seems to be the origin of the Solar

System?