The Solar System, stars, the Universe……and you Setting a context for us in the Universe The solar system; Other stars; Our Milky Way Galaxy; Other galaxies; The Big Bang; The enormity of timelines; Take home message: a good idea of our place in space, and how the building blocks of life came to be.
Scientific notation Before we can even begin… 10,000 = 1×104 600,000 = 6×105 0.00008 = 8×10-5
The Solar System All the objects within the Sun’s zone of gravitational influence. The Sun 99% of the solar system mass; 110 × Earth’s diameter; 300,000 × Earth’s mass; 4.5 billion years old (10 billion year life expectancy); H (70%), He (28%); Nuclear fusion (HHe); 30% brighter now than when formed; An unremarkable star.
Tiny Terrestrial Planets Mercury – hot, airless; Venus – hot, thick atmosphere; Earth – moderate atmosphere, warm. Moon – no atmosphere, chillier. Mars – tiny atmosphere, chilly indeed.
Giant Jovian Planets Jupiter – enormous, about 1% stellar mass. Saturn – very large, spectacular rings. Uranus – cold, relatively quiet; tilted sideways. Neptune – strangely turbulent.
Interplanetary dust • Asteroids • Asteroid belt (2.1-3.3 au); • 1-2×106 objects; 4% Moon’s mass. • Kuiper belt • 30-50 au; • 105 cometary objects; • Largest known is Eris (2500 km diameter). • Comets • Periodic (i.e., Tempel, 5.5y orbit); • Öort cloud (50,000 au); • 1012 cometary objects. Solar System Detritus
(set 1 au=15m, 50 ft) The Solar System:distance scale Sun: diameter=17 cm (6.6 inches) Earth: diameter = 2 mm (1/16 inches); 15 m from Sun Jupiter: diameter = 1.4 cm (1/2 inch); 80 m from Sun
(set 1 au=15m, 50 ft) The Solar System: distance scale Neptune: diameter = 0.5 cm (1/5 inch); 450 m from Sun (1/4 mile) Kuiper belt: 450-750 m from Sun (1/4 – 1/2 miles)
(set 1 au=15m, 50 ft) The Solar System: distance scale Öort cloud = 750 km (470 miles) (Sierra College to San Diego) Nearest star = 4000 km (2500 miles) (Sierra College to New York City)
Stars Our Sun is a relatively common type
The bigger stars have more raw fuel… …but, they use it faster Big stars burn out quickly Big stars produce a great deal of harmful radiation Stars Each different kind has a different life history… The smallest stars have very little raw fuel… …but, they use it sparingly Tiny stars live very, very long times Tiny stars produce low energy radiation
Stars and nucleosynthesis Stars turn hydrogen into helium via nuclear fusion; Stars also fuse helium into carbon, and the most massive engage in even more complicated atomic fusion reactions that produce other atoms such as phosphorus, nitrogen, etc. Carbon stars are giants that lose up to half their mass via huge winds that blow off their surfaces.
Supernovae: friends and foes Produce atoms more massive than iron. Cause ionizing events – there is no defense!
The Milky Way Galaxy A massive grouping of stars, dust, and gas, and related phenomena. Dimensions Disk 100,000 LY across; 1000 LY thick; We are 28,000 LY from center ; Scaling sun (6.95×108m) to H atom (10-10m); Galaxy=140 m across, 1.4 m tall; 100 billion times mass of Sun (interior to Rsun). Structure Bulge; Spirals: arms and inter-arms; Halo; Differential rotation.
Interstellar medium (ISM) is mostly H, He; Star formation occurs; Stars produce winds which churn and fertilize the ISM; Stars supernovae, further churning ISM; Supernova bubbles rain back into galaxy. Galactic recycling (star-gas-star cycle)
Types of galaxies Spirals Ellipticals Irregulars Active All galaxies seem likely to harbor supermassive black holes (108 × the mass of the Sun). These black holes were apparently more active in the distant past.
Galaxy groups Galaxies occur in clusters Clusters occur in superclusters Scaling sun (6.95×108m) to H atom (10-10m)… Nearest large galaxy (Andromeda, 0.8 MPC)3.4 km (2 miles) away. Superclusters (33 MPC) 150 km (90 miles) across.
Galactic evolution Central black holes calm down in time; Galaxies collide with each other; Galaxies consume their interstellar matter; Important: not all galaxies have as much dust and gas as ours does!
Receding galaxies Redshift studies have revealed that nearly all galaxies are rushing away from us. The farther a galaxy is from us, the faster it is rushing away. Truly distant galaxies are rushing away from us at speeds approaching the speed of light! What is the matter with us?
The Big Bang Galaxies are receding from us because space is expanding. This is NOT a cosmic explosion in space. It is a cosmic explosion OF space. All points in the Universe see galaxies receding from them. This mathematical model is called the Big Bang; but it ain’t no explosion!
Consequences of the Big Bang theory The Universe… … enlarged with time … cooled with time … shifted from mostly energy to mostly matter. … started out as pure H and He. … continues to age, but to what? The Big Bang theory predicts the relative H and He concentrations in the Universe. Dark Matter and Dark Energy are recent discoveries needed to explain some observations. … See Astro 5, Astro 10, or (especially) Astro 25 for details!
The Enormity of Timelines Age of Universe: 13.5-14 billion years Age of Milky Way Galaxy: at least 13.2 billion years Age of Sun: 4.6 billion years Age of Earth: 4.5 billion years First life on Earth: 3.7 billion years Homo sapiens 200,000 years (0.0014% of Universe’s age)