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 ” 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!