Astronomy Forces Review
Newtons Laws of Motion
o A body at rest, or in uniform motion, will remain so unless acted upon by
an unbalanced force.
o The change in motion (acceleration) is proportional to the unbalanced
o For e
Astronomy Galaxy Types
On the left of the diagram are the Elliptical galaxies
Elliptical galaxies contain very little gas and dust, and the gas that is present is
very hot and diffuse.
Consequently, there is no current star formation in elli
Astronomy Ancient Greek Influence
Ancient Greek Astronomers
Limited to naked-eye observations, their idea of using logic and
mathematics as tools for investigating nature is still with us today
Their investigative methodology is in many ways as importan
Galaxy luminosity function
Few galaxies L>L*
Most light from galaxies with L~L*
No accident that L~L*?
Bulges and disks
We live at edge of disk
Disadvantage: structure obscured by dust
Advantage: can study motions of nearby sta
Astronomy Growth of Astrophysics
Johannes Kepler (1571-1630)
Upon Tychos death, his data passed to Kepler, his young assistant
Using the very precise Mars data, Kepler showed the orbit to be an ellipse
Keplers Three Laws:
Planets move in elliptical
Astronomy Intro to Galaxies
What Are Galaxies?
Greek galax = milk
William Herschel, 1783: A disk with the Sun slightly off-center
What Are Galaxies?
19th Century: Spiral Nebulae
Nearby? Maybe Solar Systems in Formation?
1920: Galaxies are Stars
Astronomy universe Review
90% of the Universe is Missing
Outer Stars in Galaxies revolve faster than expected
What holds clusters of galaxies together?
Conclusion: There must be a lot of invisible mass in the Universe
Not really missing, just non-lumi
Astronomy section 1 review
What is a planet?
In August of 2007 the International Astronomical Union redefined what a planet is
(no official scientific definition of a "planet" existed before). A planet:
1. Is a body that orbits the sun (this definition on
Astronomy Renaissance Review
Tycho Brahe (1546-1601)
Designed and built instruments of far greater accuracy than any yet
Made meticulous measurements of the planets
Made observations (supernova and comet) that suggested that the heavens
Astronomy Pre-Historic Review
Many astronomical phenomena are cyclic on a day-to-day and year-toyear basis and consequently gave prehistoric people:
Methods for time keeping
Ability to predict and plan f