ASTR 3 Study Guide - Winter 2019, Comprehensive Midterm Notes - Weightlessness, Tidal Force, Thermal Energy

92 views42 pages
Published on 14 Feb 2019
School
Department
Course
Professor
ASTR 3
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 42 pages and 3 million more documents.

Already have an account? Log in
What is Astronomy?
Astronomy covers the structure and composition of the Universe from its beginning to its
ultimate end
Where did your atoms come from?
What is the Universe made of?
What happens in 1 billion years?
What happens in 100,000 billion years?
Universe is vast, possibly infinite space, sparsely filled with hydrogen and helium gas
Some places has gravity pull the gas together to make objects (Ex. you)
Fun Facts
Your atoms once drifted for more than a billion years in space
Your atoms have been part of several stars including at least one supernova explosion
The oceans will boil in 1 billion years
The Chesapeake Bay was formed through the impact of an asteroid 35 million years ago
At least 30% of stars have planets
Stars
>1.1 billion in existing catalogs
90% fusing H into He like the sun
Sun is in top 10% of brightest stars
A few stars 1,00,000x more luminous than the sun, most 10,000x fainter
Our Solar System
Solar system is basically the sun with some left-overs
Sun is 99.85% of total mass
1000x more massive than Jupiter which is 2nd most massive object
330,000x more massive than Earth
Basic Properties of Sun
Distance: 1.48x10^8 km = 1 A.U.
Mass: 1.99x10^30 kg = 330,000 Earths
Radius: 6.96x10^5 km = 100 Earth radii = 2x orbit of moon
Rare Stars
Red Giants, White dwarfs, Neutron stars
All in some stage of death--often throwing material back to space
Giant Molecular Clouds
1,000 solar masses of dust and gas
Debris from dead stars
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 42 pages and 3 million more documents.

Already have an account? Log in
Gravity is bringing material back together
Stellar Recycling
When stars die, they cast off large amounts of enriched material back into the Galaxy
This material combines with other similar “debris” to form vast clouds of dust and gas
(giant molecular clouds)
All elements heavier than He made this way
Clouds can collapse under gravity and will form new generation of stars
Other Galaxies
>100 billion galaxies in observable universe
Each with 100 billion stars like the sun
At any moment the moon (0.5 degrees) blocks >500,000 galaxies that the largest
telescopes can discern
Getting to the Stars
Furthest that Hubble Space Telescope has ever travelled from the Earth’s surface is 350
miles
Space Shuttle travelled 18,000 mph: takes 7 months to go to the sun (1 A.U.)
30x faster than an airliner
5 miles every second
90 min to go around the world
Next nearest star (Proxima Centauri) would take 166,000 years
Center of galaxy would take 1.1 billion years
Astronomys Main Tool
LIGHT comes to us
The Universe is largely transparent so with sufficiently large telescopes we can see
arbitrarily far away
Light travels at an incredibly fast, but FINITE speed of 186,000 miles per second
(300,000,000 meters per second)
Light-Year
Define: the distance light can travel in one year
Multiply the speed of light in km/s by the number of seconds in 1 year
Almost 10 trillion kilometers (6 trillion miles), in “round” numbers
Speed of light is almost 300,000 km/s
About 31.5 million seconds in a year
Light Shows Us the Past
You see a neighbor 1 meter away as from light that left them 3 nanoseconds ago
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 42 pages and 3 million more documents.

Already have an account? Log in
One mile away is 5 microseconds ago
Satellite communications with point 20,000 miles away can have 0.1 second delay
Moon seen as it was 1.3 seconds ago
Sun is 8 minutes away
Extreme Time and Size
Timescales and sizes in this class are so extraordinary compared to our everyday
experiences we rarely have good intuition
1 second is short, 100 years is very long
1 mm is short, 100 miles is very long
Long Times
Evolution of primates into humans
During lifetime, and even over recorded history (10,000 years) humans and primates
haven’t changed significantly
If a generation is <20 years, that’s more than 500 generations with little change
First hominid ancestor split from other primates 5 million years ago or 250,000
generations
Cosmic Time and Calendar
Earth and Solar System are 4.6 billion years old
1,000x longer than evolution of first Hominids
250,000,000 generations of people would be needed to witness entire history of
the Earth to date
A common method is to make an analogy with a calendar (popularized by Carl Sagan in
Cosmos)
Squeeze entire history of Universe into a Cosmic Year
Big Bang stars the year at Jan 1
Now is midnight, Dec 31
Universe is 13.7 billion years old
Cosmic month represents 1.15 billion years
Cosmic day is 38 million years
Cosmic second is 430 years
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 42 pages and 3 million more documents.

Already have an account? Log in

Get OneClass Grade+

Unlimited access to all notes and study guides.

YearlyMost Popular
75% OFF
$9.98/m
Monthly
$39.98/m
Single doc
$39.98

or

You will be charged $119.76 upfront and auto renewed at the end of each cycle. You may cancel anytime under Payment Settings. For more information, see our Terms and Privacy.
Payments are encrypted using 256-bit SSL. Powered by Stripe.