The universe contains millions of galaxies, including the Milky Way galaxy that contains our solar system. Our solar system is centered around the sun, which is made up of hot gases. It contains layers including the photosphere and chromosphere. The solar system also contains 8 planets that can be divided into terrestrial and gas planets. The terrestrial planets are closer to the sun and include Mercury, Venus, Earth, and Mars while the gas planets farther out include Jupiter, Saturn, Uranus, and Neptune. The solar system also contains asteroids, meteors, comets, and other minor members.

1. The Milky Way – and Beyond
-The universe is vast beyond human
imagination.
- Stars exist in groups called galaxies, and
one of these galaxies is the Milky Way – our
galaxy.
- There are millions of stars in our galaxy
and our Sun is just one of them.

2. Members of the Solar System
1. The Sun
- The Solar System is named after the
Sun. Solar means of the Sun.
- The Sun is the center of the Solar
System and it holds all the members of
the system together through its
gravitational pull.
- The Sun is a rotating sphere of hot
gases, with diameter of 1380 000 km.
- Mass = 2 x 1030 about 300 000 times of
Earth.

3. Layers of the Sun
1. Photosphere
- Which means “sphere of light”, is the
bright thin layer of visible light. It is
a sea of gases with a temperature of
about 6 000 0C.
2. Chromosphere
- Which means “color sphere”, is above
the photosphere and is a dense layer
of colored gases with a temperature
that reaches about 10 000 0C.

4. 3. Corona
-Outermost region of the Sun.
- It is the halo of white light seen
around the Sun during a total eclipse.
- It has a temperature that reaches
about 1 – 1.5 million 0C.
- Pressure is enormously high in the
center of the Sun. In these extreme
conditions, hydrogen is converted to
helium in a process called nuclear
fusion.

5. 2. The Planets
a. Terrestrial Planets – solid planets
made up of rocks and metals.
- Mercury - Earth
- Venus - Mars
b. Gas Planets – made up of mostly of
gases, which are very different from
the gases in the Earth’s atmosphere.
- Jupiter - Saturn
- Uranus - Neptune

6. a.Terrestrial Planets
1. Mercury – “Swiftest Planet”
- Nearest planet to the Sun.
- Mercury was named after the Roman God
of commerce, travel, and thievery.
- Rotation = 58.5 days
- Revolution = 88 days
- Moon = none
- Exploration = Mariner 10 in 1974 – 1975
and only 45% of its surface has been
mapped.

7. 2. Venus – “Veiled Planet”
- It is the second nearest planet to the Sun
and is sometimes regarded as Earth’s twin
planet.
- Named after the Roman God of Beauty
-It is covered by rapidly spinning clouds that
trap surface heat, resulting in a greenhouse-
like environment.
-Average temp. = 450 0C
-It rotates backward or opposite the
direction of its orbit around the sun.
-Rotation = 243 days
-Revolution = 224.7 days
-Moon = none

8. Exploration
- Mariner 2 in 1962 (first spacecraft to visit
Venus)
- Soviet Probe Venera 7 ( first to land on the
planet)
- Venera 9 (first to send photographs of its
surface)

9. 3. Earth – “Living
Planet/Blue Planet”
-Third planet from the Sun
-It has four seasons as a result of the 23.5 0 tilt
of its axis.
- It is the only known planet in the Solar
System that has water in its liquid form,
without which, life cannot begin.

10. 4. Mars – “Red Planet”
-Named after the Roman God of War
-It is the home to the Solar System’s highest
mountain –Olympus Mons (27 000 km high)
-Polar ice caps are also present on Mars but
astronomers have yet to discover the
presence of liquid water.
-Rotation = 24 hours, 37 minutes
-Revolution = 687 days
-Moons = 2 (Phobos and Deimos)
Exploration =
- Mariner 4 in 1965 (first to visit Mars)
-Mars 2 and two Viking landers in 1967
-Mars Pathfinder July 4, 1997 (last
spacecraft to land successfully on Mars)

11. b. Gas Planets
5. Jupiter – “Largest Planet”
-It is the fourth brightest object in the sky
-It is considered to be “The Great Wandering
Star”
-Galileo’s invention of the telescope led him
to the discovery of the four large Jovian
moons, namely:
a. Io
b. Europa
c. Ganymede
d. Callisto

12. -Rotation = 9 hours, 50 minutes
-Revolution = 11.86 years
-Moons = 64 moons
-Exploration=
-Voyager I in 1979 (discovered that it has
rings)
-Galileo spacecraft in 1995 (dropped a probe
into Jupiter’s atmosphere.
-E.E. Bernard in 1892 (discovered another
moon Amalthea)
-Cassini Probe (highest resolution of image)
-Great Red Spot

13. 6. Saturn – “The Ringed Planet”
-Second largest planet
-Galileo was surprised when he observed
Saturn though a telescope and discovered a
pair of objects on both sides of the planet.
-Christian Huygens – observed that those
“pair of objects” was Saturn’s rings.
-The least dense of the planets
-Rotation = 10 hours, 14 minutes
-Revolution = 29.46 years
-Moons = 30

14. Exploration =
-Pioneer 11 in 1979 (first to visit Saturn)
-2 Voyager spacecraft made a detailed
observation of the planet’s rings.
-Cassini/Huygen’s spacecraft October 1997 (
collect data on Saturn, its moons, rings, and
magnetosphere during its four year study.
-Titan = Saturn’s largest moon

15. 7. Uranus – “Green Planet”
-Its discoverer, William Hershel, first
thought it was a comet,
-Uranus gets its blue-green color from the
methane clouds above its atmosphere.
-Rotation = 17 hours, 18 minutes
-Revolution = 84 years
-Moons = 21 (4 largest – Arial, Umbriel,
Miranda, Titans _largest)
-Exploration =
-Voyager 2 in 1986 (was the only one ever
sent to study the planet)
It observed faint cloud markings in the
southern latitudes of the planet.

16. 8. Neptune – “Distant Planet”
-The first planet whose existence was
predicted through mathematical
computations.
-When astronomers observed that Uranus was
not traveling along its orbit the way it was
expected to, they began to suspect the
presence of another mass perturbing its
movement.
-In 1846, Neptune was discovered right where
it was predicted.
-Rotation = 17 hours, 50 minutes
-Revolutions= 165 years
-Moons = 8 (Triton_largest moon)

17. Exploration
-Voyager 2 (the only spacecraft that visited
Neptune)
-The spacecraft tracked a large oval dark
storm in its southern hemisphere.
-It is the coldest body yet visited by a
spaceprobe in our Solar System.

18. Minor Members of the Solar System
1.Asteroids
- Also known as the minor planets, found in
between orbits of Mars and Jupiter.
- Scientists think that these asteroids are
either chunks of rocks that failed to form a
planet or fragments of a planet that had
exploded.

19. 2. Meteors (shooting stars)
- These are small pieces of interplanetary
dust, called meteoroids, that falls on Earth.
- The part that reaches earth is called a
meteorite.
- Meteor shower – is an instantaneous falling
of meteors on the same spot in the night
sky.

20. 3. Comets
-Are believed to be remnants of the Sun and
planets when they were still forming some
five billion years.
-Yuji Hyakutake – a Japanese amateur
astronomer, discovered a comet through a
pair of binoculars, named after the
discoverer.
-Hale-Bopp comet – discovered by Alan Hale
and Thomas Bopp, it is an unusually bright
comet, even brighter than Hyakutake comet.

21. Constellations – groups of stars with
distinct patterns.
Horoscopes – supposed forecasts of people’s
lives as “seen” through the signs of the
Zodiac, a special group of 12 constellations
that lie along the paths of the planets of the
Solar System, with the exception of Pluto.