Astron – “star” nemein – “to name”...‐ Dwarf planets (like Pluto) ‐ smaller round objects ‐ orbit near similar objects, in a “belt” ‐ Satellites (moons) of

ASTRONOMY Astron – “star” nemein – “to name”

ASTRONOMY Longman Dictionary of Contemporary English, 1993

astro‐ concerning the stars, the planets, or space. astronomy – the scientific study of the sun, moon, stars, etc. astrophysics – the scientific study of the chemical nature of the stars and the

natural forces that influence them.

astrology – the art of understanding the supposed influence of the sun, moon, stars and planets on events and on people’s character

The Scientific Method requires that our ideas about nature are consistent with what we actually observe!

Assumptions: ‐ Laws of Nature are “universal”

‐ apply anywhere, at any time ‐ Nature works in simple ways

Step 1: Collect Scientific Data: ‐ making observations, measurements

Step 2: Form a Hypothesis: ‐ an idea or collection of ideas to

explain the data ‐ must be based on scientific data ‐ must explain data completely

‐ no conflicts with any known results ‐ must be testable

‐ able to make verifiable predictions ‐ able to be proven false

Step 3: Test the Hypothesis ‐ perform experiments to test predictions, measure new data

If the hypothesis is supported:

becomes widely accepted

Scientific Theory If the hypothesis is not supported:

hypothesis has to be changed or rejected!

Science is a never ending process: Scientific Theories and Models

‐are ALWAYS open to questioning and testing!

A Scientific Fact: ‐ an objective and reliable observation

A Scientific Law: ‐ a concise statement/formula to explain an action or a relationship. ‐ “rules of the game” ‐ does not explain “why” ‐ usually one part of a larger theory

A Scientific Theory: ‐ a tested explanation based on a wide

body of knowledge. ‐ represents the most complete

understanding we have for any topic. Common usage of “theory” is WRONG!

“It’s only a theory” X an untested idea X an idea not based on facts X a (wild or crazy) guess

Science is NOT: ‐ a collection of bits of information

‐Data is only one part of a process

‐ Something that only can be done by highly trained individuals

‐Science is a method or way of

thinking

‐ Absolute Proof ‐Science cannot “prove” something

without testing every possibility ‐Scientific evidence can only support

a hypothesis, not prove it ‐But, a theory can always be

disproven

‐ Popular opinion ‐ opinions won’t affect how nature

works

Large Scale Structure of the Universe

The size of a person is used as a reference

GPC Clarkston Campus, Google Earth

Earth (planet)

An object composed of liquid & solid material - may also contain some gases - has enough gravity to become round - relatively isolated in space

http://apod.nasa.gov/apod/ap130331.html

http://messenger.jhuapl.edu/the_mission/flyby_movie.html

The Solar System

A system of astronomical objects including: - Earth (a planet) - Seven other planets

Mercury Venus Earth Mars

Jupiter Saturn Uranus

Neptune

- The planets orbit around the Sun

The SUN (a typical star)

http://sohowww.nascom.nasa.gov/ http://www.nasa.gov/mission_pages/sdo/main/index.html

The Sun ‐contains 99.86 % of mass of solar system ‐hot ionized gas, produces energy

Other objects in the Solar System:

‐ Dwarf planets (like Pluto) ‐ smaller round objects

‐ orbit near similar objects, in a “belt”

‐ Satellites (moons) of the planets ‐ can be larger than a “planet” ‐ but, if it orbits another planet

=> “moon”

‐ Asteroids ‐ small, irregular shape, rocky & metallic

‐ Comets ‐ small, icy, often with long tails

Measuring Distances: - Standard units (km or miles)

- too small, inconvenient to use - Astronomical Units (AU)

- 1 AU = distance from Earth to Sun (93,000,000 miles or 150,000,000 km)

‐ Light Travel Time ‐ uses speed of light (c) to measure distance

(c = 186,000 miles/s or 300,000 km/s)

1 light second = the distance light travels in 1 second (300,000 km)

1 light minute = the distance light travels in 1 min.

1 light hour = the distance light travels in 1 hr.

Examples: Earth Circumference = 24,900 mi; 40,000 km

= 0.13 light sec.

Earth‐Moon = 239,000 mi; 384,000 km = 1.3 light sec.

Earth‐Sun = 93,000,000 mi; 150,000,000 km = 8.3 light min.

Sun‐Pluto = 3,674,500,000 mi; 5,913,500,000 km = 5.5 light hrs

What is “NOW”? - “Now” is when the light reaches us - No way to know anything before its light reaches us

The Solar Neighborhood

The region of space around us, beyond the edge of the solar system:

‐“sea” of stars visible in the night sky

Typical Distances between stars: ‐several light years (1ly. = 9.47x1012 km)

https://apod.nasa.gov/apod/ap000611.html

Scale model: Sun = size of ping‐pong ball

http://www.atlasoftheuniverse.com/


The (Milky Way) Galaxy

A huge rotating system including: ‐100,000,000,000 stars (& their planets) ‐gas & dust clouds, black holes etc. ‐roughly 100,000 light years across

http://www.smithsonianmag.com/photocontest/10th‐annual/10th‐Annual‐Photo‐Contest‐Finalists‐Natural‐World‐194333591.html

Panorama over Yosemite National Park http://apod.nasa.gov/apod/ap140502.html

http://www.slate.com/blogs/bad_astronomy/2012/12/02/the_milky_way_and_the_lighthouse_photos_from_australia.html

All the objects in the MW move around the center

‐ Sun and solar system take roughly 225 million years to orbit around the galaxy once!

The Local Group

A large region of space containing: ‐The Milky Way Galaxy ‐The Andromeda Galaxy ‐over 30 smaller galaxies ‐roughly 5 million light years across


M31, Andromeda Galaxy http://apod.nasa.gov/apod/ap090510.html

M33, Triangulum Galaxy Small/Large Magellanic Clouds

The Local (Virgo) Supercluster

An enormous region of space containing: ‐The Local Group ‐The Virgo Cluster ‐up to 100 other galaxy clusters ‐up to 50 ‐ 100 million light years in size


The Universe An immense (and possibly infinite) “sea” of galaxy clusters and superclusters ‐ visible size roughly 13.5 ‐ 14 billion light

years


Hubble Deep Field Survey

Hubble Deep Field with Redshifts

z = 1.0 r = 7.8 billion ly z = 4.0; r = 12.0 billion ly

http://www.slate.com/blogs/bad_astronomy/2011/12/22/star_factory_at_the_edge_of_the_universe.html

Most distant object ever observed!! z = 11.9; r = 13.3 billion ly


Documents

Astron – “star” nemein – “to name”...‐ Dwarf planets (like Pluto) ‐ smaller round objects ‐ orbit near similar objects, in a “belt” ‐ Satellites (moons) of