VIEWS: 1 PAGES: 30 POSTED ON: 11/17/2012
• no evidence for life beyond Earth – yet. • multitude of good reasons to believe life is widespread. • life may exist elsewhere in our solar system, not “intelligent life” • the possibilities, i.e. number of places, where life may be are innumerable • we are “star stuff” – God’s kitchen (the universe) builds all the ingredients for life • thus, “ASTROBIOLOGY”, studying the development of life on Earth and in the universe! 5. Galaxy Cluster 3. Galaxy (stellar system) 4. Galaxy Group (several galaxies) 2. Planetary System (with star) 1. Planet (ecosphere) Distance measured in “light time” speed of light = 300,000 km/s = 186,000 miles/sec Sun-Earth distance….......... 8 light minutes Solar System diameter……. 22 light hours Nearest Star………………… 4 light years (lys) Galaxy diameter………........ 100,000 lys Local Group diameter……… 1,000,000 lys Galaxy Cluster diameter…... 100,000,000 lys Size of Universe……………. 12,000,000,000 lys Anatomy of a Galaxy 250,000,000 yr rotation 20 Sun orbits Solar System Formation Gravity dominates – then angular momentum and pressure from heat. Solar System Formation Solar System Formation • star born in center • planets form in disk • metal/rock “seeds” in inner disk • ice “seeds” in outer disk • gas survives in outer disk – forms gas giants with ice cores • star lights up – blows remaining gas away • Terrestrial Planets inner systems • Jovian Planets outer system The Solar System Relative Sizes… Scale… A Star a balance between gravity and pressure core Gravity tends to crush the star, which causes The very center is called the the temperature and the core. In the core the density density to increase is ~150 times that of water toward the center. and the temperature is 15 million degrees Kelvin Planetary Nebulae The Sun’s Fate White Dwarf Supernovae Remnants in Our Galaxy Young Old Fate of very Massive Stars… Supernova in a distant galaxy. Atoms are comprised of a nucleus and electrons (in orbits -> would appear as a swarm or cloud) protons = positive charge; neutrons = no charge; electrons = negative charge The nucleus is extremely tiny; atoms are empty space! = 4.5 football fields = 450 yards = 1350 feet = ¼ mile This atom is blown up a trillion times = 1012 = 1,000,000,000,000 Atoms are defined by atomic number = number of protons hydrogen = 1; helium = 2; carbon = 6 The number of electrons is equal to the number of protons. A given atom does not always have the same number of neutrons (or mass). These different “flavors” of a given atoms are called isotopes. How elements are built and energy is released Fusion: small atoms bind together to form large atoms Fission: break up large atoms to form small atoms Shown is the energy released per fusion/fission event; this is called the binding energy. Note that a large amount of energy is released binding hydrogen into helium. Still, it takes 1038 reactions per second to support the sun! That is the conversion of 5 millions tons of mass into energy every second. Thus mass is lost from the sun forever. Note the special location of iron. The Energy Source of Life (and the chemical source!) e+ Step 1 of the Proton-Proton Chain… 1H + 1H 2H + e+ + n Two hydrogen ions (1H) “collide”. They stick together, or fuse, into deuterium (2H), an isotope of hydrogen- it has one proton and one neutron. This is called fusion. Also, in the process, a positron (e+, antimatter of electron) and a neutrino (n) are produced. In the process the positron (anti-matter version of electron) finds a free electron in the sun’s core plasma and when they collide they annihilate and release energy (photons). The Energy Source of Life (and the chemical source!) e+ Step 2 of the Proton-Proton Chain… 2H + 1H 3He +g The deuterium from step 1 collides with a hydrogen, forming tritium, an isotope of helium, with only one neutron instead of the typical two. In the process, a photon (g) is produced. This photon carries away energy. The Energy Source of Life (and the chemical source!) e+ Step 3 of the Proton-Proton Chain… 3He + 3He 4He + 1H + 1H 3 1 2 Two tritium from two different step 2s collide and form helium. In the process two hydrogen (1H) are e+ produced. Massive stars undergo multi-layered shell burning. The time duration that each shell burns becomes shorter and shorter as the star becomes desperate to battle against the merciless crushing force of its own gravity. Hydrogen .…… 7 million yrs Oxygen ………. ½ yr Helium …….…. 500 thousand yrs Silicon ……….. 1 day Carbon …….… 600 yrs Iron collapse … 0.1 second BOOM! Carbon, nitrogen, oxygen are blasted into interstellar space! Interstellar Gas Clouds Have Chemistry Carbon is the most versatile chemical element (atom) It can make 1,2, 3, or 4 strong bonds Compounds are molecules with more than one type of element… These chemical elements form the next generation of planets! Which of these are good sites for biology? On Earth, biology/life persists even in very hot and/or dark environments! Black Smoker Hot Spring On Earth, biology/life persists even in very cold/frozen environments! Antarctica Frozen rocks are the habitat of microbes. They “hibernate” in a frozen state, and then drink up when the sun warms the ice to water Is Mars much different than Antarctica? Is the warm upper atmosphere of Jupiter teaming with microbes? Mars is covered in a permafrost- are the rocks any different than those in Antiarctica? Room temperature about 300 km down Jupiter’s Moon Europa Covered with Water Ice- The cracks change with time, revealing a dynamic geology Dynamic geology means energy input into planet! A theoretical cutaway of Europa – we think the moon has a water ocean under the surface ice… Saturn’s Moon Titan Thick Methane atmosphere… Laboratory experiments to create a “gas” to match the measured properties of Titan’s atmosphere suggest a hydrocarbon gas rich with organic molecules! The Huygens Probe, supplied by the European Space Agency, has six complex instruments aboard. The data from these instruments will be received by the Cassini spacecraft and relayed to Earth after the probe descends into Titan's mysterious atmosphere in early 2005. ASTROBIOLOGY astro – study of the universe biology – study of life astrobiology – study of life in the universe NASA’s 3 main questions: 1. How does life begin and develop? 2. Does life exist elsewhere in the universe? 3. What is life’s future on Earth and beyond?
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