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Astronomy 1020
Stellar Astronomy
Spring_2016
Day-2
Snow-2, Education-0
Course Announcements
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Smartworks Chapter 1: Start on – it will be
due next week. Make sure you hit “submit” to
record your answers – AFTER you finish the
entire assignment (not after each question).
If you plan to do some and then come back,
write your answers down on a piece of paper.
Because of the snow (and ice) nothing will be
due until after we return to the classroom.
 Modern astronomy
is more than
cataloging objects.
 How do stars
(matter and energy)
work?
 What is the
universe?
 How do humans fit
in?
Size
 The Universe is BIG!
 Earth is a small planet,
 orbiting a medium-sized
star,
 in a galaxy of 400 billion
stars,
 which is just one of
billions of galaxies,
 in a universe that is 13.7
billion years old.
The Universe is Strange
New Concept:
Cold Dark Matter
Size
 The universe is vast.
 Billions of galaxies are
separated by thousands
of trillions of miles.
 How do you visualize this?
 Astronomers need to be
able to talk about great
distances.
 We use the distance light
will travel in a year as a
basic “yard stick”.
Distance Measures
 Light travels 300,000 km every second.
 Universe’s greatest speed.
 Light-year: distance light travels in one year
– about 6 Trillion miles (9.4 Trillion km)
 Light could travel around Earth in 1/7
second.
Light Travel Times
 At this speed, light takes, on average:
• 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.
 It will take:
• 4.2 years to arrive
from the nearest
star.
• 100,000 years to
cross the galaxy.
• 2.5 million years to
get to the nearest
big galaxy.
• 10 billion+ years to
come from distant
galaxies.
• This can make
studying objects
difficult.
 But, studying the
universe reveals many
things.
 For example, except
for the hydrogen
in water (H2O), all the
atoms in our body were
made in stars.
 Stars generate energy
by making heavier
elements out of light
ones.
 Dying stars eject those
elements into space
in massive explosions.
 New stars and planets
(and humans) form.
 We are stardust, made
from the materials
provided by earlier
generations of stars.
 Test scientific ideas by observation.
 Space exploration has expanded our view
of planets and the Solar System.
 Telescopes, satellites, etc., extend it more.
 Science involves the use of theories,
hypotheses, and principles.
 A scientific hypothesis is an idea that leads to
testable or falsifiable predictions.
 The cosmological principle is a very
important underlying assumption:
• “There is nothing special about our place in the
universe.”
 Cosmological principle on one level:
• Our view from the Earth is not special or unique.
• Distant objects should be like nearby ones, which
we can study in detail.
 On another level:
• Matter and energy obey the same physical laws
everywhere.
• We can learn about distant objects by studying
nearby ones.
Science Is Creative
 Science is one of many creative human activities.
 It has its own rules for deciding what is right and
wrong.
 It is an important way for achieving knowledge and
insight.
 There are also other valuable ways to achieve
understanding.
Science Is Subversive
• Old ideas can be falsified and rejected.
• New ideas must be supported by evidence.
• Authority often works by suppressing inquiry.
• Scientific authority can be overthrown by new or
better evidence.
• Nature is the arbiter of science. It decides what
ideas are good or bad. (Occam’s Razor)
Scientific Progress
• The scientific processes and investigations can be
slow: many small steps and tweaks.
• Every now and then, there is a revolution and
progress is very rapid in both new knowledge gain
and understanding the implications and effects.
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Newtonian Mechanics
Quantum Mechanics
Evolution
Science Is a Process
• Science is a method for learning about nature.
• The scientific method works like this:
• Ideas are tested against nature.
• Tests come from observation or calculation.
• The tests falsify some ideas and support others.
• All scientific knowledge is provisional.
• Science involves Exploration & Discovery
• HST
• Curiosity
The Scientific Method
• To be accepted as valid,
an idea must be testable
and falsifiable.
• This separates “fact” from
“faith”.
• We use the “Scientific
Method”. The heart of
the Scientific Method is
making a testable
prediction based on a
valid hypothesis (or
theory).
Cute and Science
Math: The Language of Science
• Review page 16 – Math Tools 1.1 box.
• You should feel comfortable working at this level.
• You’ll need at least these skills just to live in the
modern world.
• Scientific Notation
• Ratios
• Geometry
• Algebra
• Proportionality
Dealing with very large and small
numbers
Scientific Notation
4,500,000,000,000,000 = 4.5x1015
0.000000000000000028 = 2.8x10-17
On calculators…look for the “EXP” key or the “EE” key
Common Prefixes
Don’t let the units confuse you.
centi = 0.01 = 10-2 (c)
milli = 0.001 = 10-3 (m)
micro = 0.000001 = 10-6 (m)
nano = 0.000000001 = 10-9 (n)
kilo = 1,000 = 103 (k)
mega = 1,000,000 = 106 (M)
giga = 1,000,000,000 = 109 (G)
tera = 1,000,000,000,000 = 1012 (T)