Download 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