Transcript Day-5
Astronomy 3040 Astrobiology Spring_2016 Day-5 Homework -1 Due Monday, Feb. 8 Chapter 2: 1, 3, 16 23, 24, 26 29, 30, 33 44 53, 54, 56 The appendices will be useful Project http://www.ulalaunch.com/docs/product_sheet/Delt aIVPayloadPlannersGuide2007.pdf This is the Delta-IV payload guide overview. 20MB. Planetary quarantine program. The Universe and Life The Universe is vast and old. The elements of life are widespread. The same physical laws operate throughout. The Cosmological Principle There's nothing special about Earth Compared to the universe, the Earth is less than a grain of sand on a beach A Vast Universe The universe is vast. We need to handle great distances and long times. We can do this through the travel time of light. Light travels 300,000 km every second. We often use times to denote distances. For example, we may say a friend’s house is two hours away. Astronomy is a time machine! Light Travel Times Light takes: 1¼ seconds to arrive from the Moon. 8.3 minutes to arrive from the Sun. 5.5 hours to get to Pluto from the Sun. 4.3 years (yr) to get to the nearest star. 100,000 yr to cross the galaxy. 2.9 million yr to get to the nearest big galaxy. 10 billion yr to come from distant galaxies. Energy Content of the Universe History Expansion Time of Human Life Where do Stars Form? Spirals Cold Gas Much of the gas is in cool interstellar clouds, with hotter intercloud gas between them. Many clouds are cold enough for hydrogen to be in the H2 molecule. These are called molecular clouds. Temperatures are below 300 K emit radio waves. Many other molecules are in the mix. Stars form in molecular clouds. A Molecular Cloud Pat Hartigan, Rice University Star Formation Molecular clouds are cold and dense. Some places in the cloud are denser than average. Gravity will make these regions collapse. Rate of collapse is slowed by magnetic fields, turbulence, and angular momentum (spin). Collapse and fragmentation leads to dense star-forming cores in the molecular cloud. Spin and Collapse Molecular cores collapse under their own gravity. Center shrinks fastest; outer layers later. This produces a dense protostar. Spin of core produces a disk of material around the protostar. Material falls onto the growing protostar from the disk. Protostars Protostars are large, cool, and luminous. They will emit infrared light. Infrared studies of molecular regions reveal protostars and their disks. The protostar continues to shrink and radiate away energy. The interior temperature and pressure rise. Contraction of a Protostar JPL/NASA/Karl Stapelfeldt Bipolar Outflows Many or all protostars have material flowing outward in a bipolar outflow. Powerful flows can collide with the interstellar medium to make Herbig-Haro objects. These can eject lots of the mass that would otherwise land on the star. Infalling and outflowing gas can be very complex. Jets and H-H Objects Jeff Hester (Arizona State University), WFPC2 Team, NASA