The Planets in our Solar System

Solar System Basics

• Our solar system is not only made of the Sun, the nine planets and their satellites, but also asteroids and comets.

• All celestial bodies revolve around the sun.

• The characteristics of each planet were determined by where each planet formed in relation to the Sun.

• The various temperatures created different elements. • Heavier elements formed closer to the heat of the

Sun, lighter elements formed farther from the Sun.

More on planet formation . . .

• Temperature and distance from the Sun influenced the condensation of various substances within the evolving solar system.

• Eventually, the condensing material merged to form large bodies hundreds of kilometers in diameter.

• These bodies were called planetesimals.

• The planets began to form from the collision of these planetesimals.

To be or not to be . . .

• Pluto is weird – Solid surface but low

density; the best of both worlds!

• Planet: – Yes, solid body

orbiting star.– No, orbit too far off

and not regular.

• Decide for yourself!!

The Birth of the Sun • The sun formed from

the dense concentration of gas at the center of the solar nebula.

• As the gas and dust condensed, the temperature and pressure at the center increased.

• The temperature and pressure became so great, nuclear fusion began.

The Sun (. . . Continued)

• Nuclear fusion causes lighter atoms, like hydrogen, to fuse and become heavier atoms, like helium.

• This reaction releases tremendous amounts of energy.

• The sun releases this energy in the form of thermal energy and light.

Other Objects in the Solar System

• Asteroids– Small, rocky bodies that orbit the Sun.

• Comet– A small body that revolves around the Sun in

an elliptical orbit. – It is a body of ice with a rocky core– When it nears the Sun, the ice melts and is

illuminated by the sun, forming the tail.

Meteoroids, Meteors, and Meteorites!

• Meteoroids– A fragment of an asteroid that enters Earth’s

atmosphere.

• Meteor– A meteoroid that burns up as it enters Earth’s

atmosphere. (Shooting Star)

• Meteorite– A meteor that hits the Earth

Formation of the Planets

• The particles in space surrounding the sun contracted to form the planets of the solar system.

• *A planet is a celestial body revolving around a star.

• Our solar system has 9 planets revolving around our star – the Sun.

Two Types of Planets

• The Inner Planets– Terrestrial

– Made of heavy, solid elements

– Mercury, Venus, Earth, Mars

• *Gas Giant Planet:– The Outer Planets

– Gaseous

• About 15 times larger than Earth

• Composed of hydrogen and helium

– Light, very low density

– Jupiter, Saturn, Uranus, Neptune

Galaxies . . .

• The sun is the star of our solar system, but it is only one of millions of stars in the Milky Way Galaxy.

• A *galaxy is a system containing millions of stars held together by gravity.

The Neighborhood . . .

• *A Local Group of galaxies is a group of 30 galaxies, of which the Milky Way is a part.

• The local group is part of a 10,000 unit supercluster

Proxomity

• *Astronomical Unit (AU)– The distance between the

Earth and the Sun

– ~ 93 million miles.

• A *light year is the distance light travels in one year.

~ 9.7 trillion km.

General Solar System Info . . .

• (#1) The two largest planets in our Solar system are Jupiter and Saturn ~ both gaseous planets.

• (#2) Venus is the planet closest in size to the Earth.

• (#3) The inner, terrestrial planets are much smaller than the outer, gaseous planets.

• (#4) According to the ESRT, Jupiter’s diameter is about 11 times greater than Earth’s.

• (#5) The sun’s diameter is 1,394,000 km. If we used the scale 1 mm = 700 km, the sun would be almost 2000 mm (1.9 m)!

• (#6) The outer planets are much farther apart than the inner planets.

• (#7) The planets that are closest to Earth are Mars and Venus.

• (#8) Which planet has the longest period of revolution?

• Neptune at 165 years.• Why?• Check out the ESRT;

It’s the farthest planet from the sun!

• (#9) Which planet has the longest period of rotation?

• Venus– 243 days

– Earth rotates in 24 hours!

• (#10) How many moons orbit around Jupiter?

• 16, compared to 1 for Earth, 18 for Saturn and 21 for Uranus!

Conclusion . . .

• All of the planets, including Jupiter, are dwarfed by the size of the sun

• The Earth is close to the sun in comparison to other, “nearby” stars and galaxies.