The origin of the Solar System
Small planets beyond Pluto – Sedna, ~1,300 – 1750 km dia.
Our Solar System is about 16
billion km, or 10 billion miles, or
15 light hours across.
Light travels ~ 300,000 km/sec or
~1.1 billion km/hour
Our galaxy, the Milky Way
A galactic center: More than 1 Million stars are visible here!
Edge-on view of a spiral galaxy. Our galaxy, the Milky Way, would
look very much like it to an outside visitor
Our galaxy, the Milky Way
IRAS telescope
image of 
Pictoris, a solar
system in the
making? Red =
solid material.
Star nurseries in the constellation Sagittarius
“The Big Picture”
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The “Big Bang”, the birth of the Universe ~ 13 Gy ago,
produced H and He. These elements formed stars
which cluster in galaxies with billions of stars; our
galaxy, the Milky Way, formed ~ 10 Gy ago.
Other elements are synthesized in the interiors of stars
such as Red Giants and Supernovae.
Upon ejection into interstellar space from dying stars,
some elements condense into dust grains (presolar
grains) and amorphous dust, either in stellar
atmospheres or in interstellar space.
Gas and dust collect into giant, cold molecular clouds.
Dense cores collapse into stars, such as the Sun 4.56 Gy
ago and planets, asteroids and comets form.
Asteroids collide and fragments fall on Earth as
meteorites
We study meteorites and the presolar grains which
some of them contain. These tell us about the complex
nucleosynthetic processes that are going on in stars,
such as Supernovae, AGB stars, etc.
The origin of the Solar System
The critical role of Earth’s Moon in helping life start and be
sustained on Earth
• Moon adds stability to
Earth’s rotation, so
less extreme seasons
• Moon provides ocean
tides on Earth –
promotes early life in
shallow pools
• Moon slows Earth’s
rate of rotation –
longer days
Growth of continents with time
Old parts of the Moon are very
heavily cratered. This indicates
that early in the history of the
Solar System the Moon and, by
inference, Earth were very
heavily bombarded by highly
destructive bullets from space
(asteroids; comets)
Oldest rocks on Earth are ~3.85
Gy old. Older rocks were
destroyed by impacts and
erosion: There is nothing left of
the earliest period of Earth
history!
The atomic bomb dropped on Hiroshima was ~ 20 kt (1 kt = 1,000 t of TNT; 1 mt = 1,000 kt).
Meteor Crater Arizona = 3 mt = 150 Hiroshima bombs.
How long does life exist on Earth
Earth is unique: Do not mess it up!
Planets outside our Solar System, orbiting other stars, in multiples of
Jupiter masses (Mj). Conclusion: Most planets have masses equal to,
or a few times, the mass of Jupiter
Planets outside our Solar System, orbiting other stars, plotted as a
function of the distance of their star. Conclusion: Most planets orbit
extremely closely to their stars!