Transcript NASC 1100 - The University of Toledo

Lecture 33
The Solar System. The Inner Planets.
Chapter 16.1  16.8
• The Solar System Overview
• Terrestrial Planets
Our Cosmic Origins
• The Big Bang – beginning of the Universe
• 12-16 billion years ago
• Galaxies are flying away from each other
• No expansion within galaxies
• Only hydrogen and helium in the early Universe
• All other chemical elements were created inside stars
• We are all created from the stars’ stuff
• Current composition of the Sun: 70%H, 28%He, 2%others
Images of Time
• Speed of light: c = 300,000 kilometers per second
• Light year – distance which light travels in 1 year
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From the Sun to Earth - 8 minutes
From the Sun to Pluto - 5 ½ hours
To the closest star
- 4 years
Through the Milky Way - 100,000 years
To the closest galaxy - 2,500,000 years
• The farther away the object, the further back we look in
time
Sun within our Galaxy
Appearance of the Milky Way
The Solar System
• Content:
Sun (the only star)
9 planets
Nearly 100 moons
Asteroids
Comets
Free-flying gas and ‘dusty’ particles
Solar System
APOD: 2002 April 29 - Dusk of the Planets
http://solarviews.com/eng/homepage.htm
The Sun
• Temperature (at surface) - 6000 degrees Kelvin (K)
• Size (diameter) - 1,392,500 kilometers (km)
• Mass – 1.86 1030 kilograms (kg) or 98% of the total
mass of the Solar system
• Energy production rate – 4 million tons of mass
(E=mc2)
• Age – 4.6 billion years
• Total stable life time - ~10 billion years
Our very own star
APOD: 2003 May 17 - Dark Sky, Bright Sun
APOD: 2003 March 24 - A Digital Sunset Over Europe and Africa
APOD: 2002 July 29 - A Setting Sun Trail
Inside the Terrestrial Worlds
Two families of planets in the Solar system:
terrestrial (Earth-like) and Jovian (Jupiter-like)
The terrestrial planets are relatively small and
almost spherical
The Earth has a radius of 6,378 km and an obliquity
of 1/298
They are mostly made of rocky materials that can
deform and flow
Every object exceeding ~500 km in diameter can
become spherical under the influence of gravity
Lithospheres of the Terrestrial Planets
Planetary surfaces are all warmed by sunlight, but
the high temperatures inside the planets today are
due to radioactive heating.
Mercury and Moon
The 2 smallest terrestrial worlds covered with lots
of impact craters.
They have volcanic activity in the past (example lunar maria).
Mercury has a 88-day orbit and a 59-day rotation.
Temperature is up to 425oC on the day side and
down to 150oC on the night side.
It has many craters, but also traces of geological
activity.
Venus
Venus is the third brightest object in the sky after the Sun
and the Moon.
Venus has very similar parameters to those of the Earth.
However, it spins backwards (clockwise if looking from
its north pole).
Its atmosphere has 96% CO2, surface temperature
400740 K, surface pressure is 90 times the Earth’s one.
It has volcanic activity, but probably no tectonic activity.
The Soviet spacecraft Venera 9 landed on Venus and
send a panoramic view of its surface.
The US Magellan spacecraft transmitted radio images.
Mars
This is an intermediate-size planet and the most
distant of the terrestrial planets from the Sun.
It has polar caps made of frozen CO2, many deserts,
and volcanoes.
There is no liquid water on Mars today, but rather
traces of past water flows.
The surface is different in the northern (low plains)
and southern (highlands).
Only 13 missions to Mars out of 23 were
successful.
Summary
Terrestrial planets are small and rocky
Only a handful geological processes shape the
terrestrial planets
Every terrestrial world was heavily cratered long
ago. Most of the craters are erased now.
Understanding of planetary geology might help us
learn about planets of other star systems