1. Solar System Formation

2. Formation of Our Solar System
Formation of Our Solar System
• Astronomers use Earth-based observations and
data from probes to derive theories about how
our solar system formed.
• The significant
observations related to our
solar system’s formation
include the shape of our
solar system, the
differences among the
planets, and the oldest
planetary surfaces,
asteroids, meteorites, and
comets.

3. Formation of Our Solar System
A Collapsing Interstellar Cloud
• Stars and planets form from clouds of gas and
dust, called interstellar clouds, which exist in
space between the stars.
• The interstellar
clouds consist
mostly of gas,
especially
hydrogen and
helium that often
appear as blotches
of light and dark.

4. A Collapsing Interstellar Cloud
• Our solar system may have begun when interstellar gas
started to condense as a result of gravity and became
concentrated enough to form the Sun and planets.
– The collapse is initially
slow, but it accelerates and
the cloud soon becomes
much denser at its center.
– Rotation slows the
collapse in the equatorial
plane, and the cloud
becomes flattened.
– The cloud eventually
becomes a rotating disk
with a dense concentration
at the center.

5. Sun and Planet Formation
Formation of Our Solar System
• The disk of dust and gas that formed the Sun and planets
is known as the solar nebula.
• The dense concentration of
gas at the center of this
rotating disk eventually
became the Sun.
• In the disk surrounding the
Sun, the temperature varied
greatly with location.
• As the disk began to cool,
different elements and
compounds were able to
condense depending on their
distance from the Sun which
impacted the compositions of
the forming planets.

6. Sun and Planet Formation
•Elements and
compounds that were
able to condense close
to the Sun, where it
was warm, are called
refractory elements,
and far from the Sun,
where it was cool,
volatile elements could
condense.
•Planets may have
been formed by the
Accretion Theory.
•Refractory elements,
such as iron, comprise
the terrestrial planets,
which are close to the
Sun. Volatile elements,
such as ices and gases
like hydrogen,
comprise the planets
further from the Sun,
where it is cool.

7. Our Sun

8. The Sun
Solar Activity
• The Sun’s magnetic field disturbs the solar
atmosphere periodically and causes new features
to appear in a process called solar activity.
• Sunspots are cooler areas
that form on the surface of
the photosphere due to
magnetic disturbances,
which appear as dark spots.

11. The Sun
Solar Activity
Solar Activity Cycle
– The number of sunspots changes regularly, and on
average reaches a maximum number every 11.2 years.
– The length of the solar activity cycle is 22.4 years.
• The solar activity cycle starts with minimum spots
and progresses to maximum spots.
• The Sun’s magnetic field then reverses in polarity,
and the spots start at a minimum number and
progress to a maximum number again.
• The magnetic field then switches back to the original
polarity and completes the solar activity cycle.

12. Maximum
Minimum

13. Solar Activity
– Solar flares are
violent eruptions
of particles and
radiation from
the surface of the
Sun that are
associated with
sunspots.
– When these
particles reach
Earth, they can
interfere with
communications
and damage
satellites.
The Sun

15. – A prominence,
sometimes
associated with
flares, is
an arc of gas
that is ejected
from the
chromosphere,
or gas that
condenses in
the inner
corona and
rains back to
the surface.

18. The Sun
Solar Activity
Impact on Earth
– Some scientists have found evidence of subtle climate
variations within 11-year periods.
– There were severe weather changes on Earth during the
latter half of the 1600s when the solar activity cycle
stopped and there were no sunspots for nearly 60 years.
– Those 60 years were known as the “Little Ice Age”
because the weather was very cold in Europe and North
America during those years.

19. The Sun
The Solar Interior
• Fusion occurs within the core of the Sun where
the pressure and temperature are extremely high.
– Fusion is the combining of lightweight nuclei, such as
hydrogen, into heavier nuclei.
– Fission, the opposite of fusion, is the splitting of heavy
atomic nuclei into smaller, lighter atomic nuclei.
• In the core of the Sun, helium is a product of the
process in which hydrogen nuclei fuse.
• At the Sun’s rate of hydrogen fusing, it is about
halfway through its lifetime, with about another
5 billion years left.

20. The “Little Pieces”
Asteroids and Comets
Gaspra is an irregular body with dimensions of about 20 x 12 x 11 km (12.5 x 7.5 x 7
miles). Its surface reflects approximately 20 percent of the sunlight striking it. Gaspra
is composed of metal-rich silicates and perhaps blocks of pure metal.

21. Comet Hale-Bopp
Earth Closest Approach: March 22, 1997
Last seen by Tycho Brahe (1577)

22. Formation of Our Solar System
I. Asteroids
• Asteroids comprise the thousands and thousands
of bodies that orbit the Sun within the planetary
orbits that are leftovers from the formation of the
solar system.
• Asteroids range from a
few kilometers to about
1000 km in diameter
and have pitted,
irregular surfaces.
• Most asteroids are
located between the
orbits of Mars and
Jupiter within the
asteroid belt.

23. Formation of Our Solar System
I. Asteroids
Pieces of Asteroids
– As the asteroids orbit, they occasionally collide and
break into fragments.
• A meteoroid is a
asteroid fragment or
any other
interplanetary material
that falls toward Earth
and enters Earth’s
atmosphere.

24. • A meteor is the streak of light produced when a
meteoroid burns up in Earth’s atmosphere.
In the early
morning of the
3rd of november
2007 a meteor
hit Eslöv, known
as the most
boring town of
Sweden. It was
an unexpected
event that was
witnessed only
by a few.

25. • A meteorite is part of a meteoroid, that does not completely
burn up, that collides with the ground.

26. Look!
Meteorites!
Mr. Bantay at Washington DC’s Smithsonian Museum of Natural
Sciences.

27. Proposed site of the Impact Crater that hit 65 million years ago.

28. Asteroid Impact Crater below the Chesapeake Bay.

29. Great Meteor Crater, Arizona.

31. Distribution of Impact Craters on Earth

32. Russian Meteor - 02/15/2013

33. II. Comets
Formation of Our Solar System
• Comets are small, icy bodies that have highly
eccentric orbits around the Sun and are remnants
from solar system formation.
• Comets are made of ice and
rock, and they range from 1 to
10 km in diameter.
• There are two clusters, or
clouds, of comets: the Kuiper
belt and the Oort cloud.
• Occasionally, a comet is
disturbed by the gravity of
another object and is thrown
into the inner solar system
from one of these clusters.

35. November 4, 2010: NASA’s EPOXI mission passed within 435 miles of Comet Hartley 1 on
Nov. 4.
This image, one of the closest taken of comet Hartley 2 by NASA's EPOXI mission, shows
jets from the comet's surface. Analysis shows that dry ice sublimating from the comet
causes the fuzzy appearance.

36. Formation of Our Solar System
Comets
The Orbits of Comets
– When a comet nears the sun in its highly eccentric orbit,
it begins to evaporate and form a head and one or
more tails.
– The coma is an extended
volume of glowing gas
flowing from a comet’s head.
– The nucleus of a comet is
the
small solid core that releases
gases and dust particles that
form the coma and tails when
it is heated.

37. Changes to a comet:
1a. Seen as a star
1b. Coma grows
1c. Tail grows & ALWAYS faces AWAY from the sun.
1d. Tail fades
1e. Coma shrinks
1f. Coma vanished.

38. Comets
Formation of Our Solar System
Periodic Comets
– Comets that repeatedly orbit into the inner solar system
are known as periodic comets.
– Meteor showers occur when Earth intersects a
cometary orbit and numerous particles from the comet
burn up upon entering Earth’s upper atmosphere.
– Most meteors are
caused by dust
particles from comets,
while most meteorites,
the solid chunks of
rock or metal that
Leo
reach Earth’s surface,
are fragments of
asteroids.
Leonids

39. Comets and Meteors ( 4 min)

40. Solar Storm Alert 2012 - Discovery Channel: 19 minutes