Solar System and Earth
30 Sep: Solar System and Earth
05 Oct: Earth-Moon
07 Oct: Terrestrial Planets
12 Oct: Mars Close-up
14 Oct: Jovian Planets
19 Oct: Asteroids, comets, etc
21 Oct: Planet formation
26 Oct: Extra-Solar Planets
9 planets going around Sun
Other than that the solar system is
practically empty. Most of that is
near perfect vacuum.
Large: about 12 billion km across
This image shows the sun and 9 planets
approximately to scale.
The order of these bodies are Sun, Mercury, Venus,
Earth, Mars, Jupiter , Saturn, Uranus, Neptune, Pluto
Average Distance from Sun (AU)
1.5 10 m
Express numbers in a general form,
A × 10n,
which is convenient for both large and
1.5 10 m 150 m
1.5 10 m 1,500 m
1.5 10 4 m 15,000 m
1.5 10 m 150,000,000,000 m
If something happens at Sun (e.g.
Explosion), we know the event
(b) about 3 sec after
(c) about 8 min after
(c) About 8 min after
Note: in only one second,
light can circumnavigate the Earth
more than seven times
Orbits are almost in a plane (within a
few degrees) and close to circular.
Mercury and Pluto are most eccentric
and have highest inclination.
of 9 Planets
332,946 (Earth Mass)
The nine planets are often further classified as follows
Terrestrial Planets (inner 4 planets)
Mercury, Venus, Earth and Mars
small, high density, low mass, rocky
little or no atmosphere
Jovian Planets (next 4)
Jupiter, Saturn, Uranus and Neptune
Massive, low density, gaseous
probably no solid surface
Pluto: ball of ice and rock,
not much the larger than the largest asteroids
Rocky, no atmosphere
Gaseous, no solid surface
Small, high density
Massive, low density
Two ways to find out what the
planets are made of
(1) Go There! (Mars and Venus)
(2) Spectroscopy – either from Earth
or from a spacecraft passing by
or in the orbit around the planet
Terrestrial planets are rocky
- silicon, iron compounds
Jovian planets are gaseous –
hydrogen, helium, methane,
ammonia, carbon monoxide,
carbon dioxide, water vapor etc.
Water on Mars!
greeting card from my hockey mate at Jerusalem
Other Solar Stuff
Moons: small bodies that orbit
Asteroids: small bodies that orbit
Comets: dirty snowballs in highly
elliptical orbits around Sun
Most of them are between Mars and
Jupiter: Asteroid Belt
The composition is similar to that of
terrestrial planets (rocks and metals)
Comets (Ices, rocks)
Comets have ices covering them, and
these vaporize and produce a gas halo
around the comet when it comes close to
Kuiper belt comets : from extended wedge
of asteroids beyond the orbit of pluto, 30100AU
Oort cloud comets: from very extended
halo of comets, probably it extends to
What is the farthest Planet to the sun?
Sometimes Neptune is further, but it
is not a choice.
Which of these is not a Planet?
Mars is either a planet or a candy bar,
Mercury is either a planet or a metal,
and Pluto is either a planet or a
cartoon dog. Moon most definitely is
not a planet.
What is the closest Planet to the Sun?
Which of these takes the least time
to travel around the Sun?