Here there will be a copy of the class lecture notes

Here there will be a copy of the class lecture notes

Astronomy:
a quick overview
Steinn Sigurðsson
Big Bang - Astro 120-3 15 Jan ’16
Topics
Overview
Basics of cosmology
Modern cosmology & current status
Weird speculative fun stuff
Objective: some appreciation of our current understanding of the
Universe; how we know what we know; when we knew it; what
we know we do not know; and, how it all fits in with our
general understanding of how he world works in useful ways.
Size and speed
Reminder: there is a speed limit - the
speed of light
c = 300,000 km/sec
distance = speed * time
d = v*t
v = d/t
t = d/v
Review use of eqn - examples
Size and speed
The Universe is Big. Ginormous actually.
Recap Astro 001 material Earth is a Planet
Planets go around Stars
Stars are in Galaxies
Many Galaxies in the Universe
Earth is a Planet: planets usually go around stars
Earth is one of several planets in the Solar System
orbiting the Sun
The Sun is a Star:
a type G
main sequence star
Sun is really big!
Solar System
Sun - a star
8-9 planets: Mercury, Venus, Earth, Mars,
Jupiter, Saturn, Uranus, Neptune, (Pluto)
Moons; Asteroids and Comets
Planets and Stars
There are, apparently, many planets per star
Like ~ 10 or so, for pretty much every star
Planets are 1,00 - 1,000,000 times less
massive than stars. Some planets may be detached from stars,
floating free in space
Solar System
Stars
The Sun is a Star
The Sun is a medium mass, medium temperature, medium composition,
medium age star
The Sun is very massive, made mostly of Hydrogen and Helium and
about 2% “metals” - i.e. elements other than H and He
Sun’s power comes from nuclear fusion reactions in its core, burning
hydrogen into helium and generating energy in the process
The Sun has a finite lifetime - it is about 4,500 million years old and
will last about 10 billion years total. It will fizzle when it runs out of
hydrogen fuel in its core.
Local Bubble
The Sun is in an interesting
neighbourhood.
It is embedded within the “local fluff”
which is a small part of the local bubble.
The local bubble is part of the Sco-Cen
association which is part of the Gould Belt
within the Orion spur.
Thomas O’Brien Co, http://www.earthporm.com/7-years-meteor-showers-one-breathtaking-timelapse/
Nearby stars are far away:
closest is over 4 light years away
Milky Way Galaxy
The Milky Way is rather big spiral galaxy.
about 100,000 light years across. Disk is about 1,000 light years high.
Consists of a thin disk, a central bulge and an extended halo
Contains about 100 billion stars
Sun is about 25,000 light years from center
We are near a spiral armlet, the Orion spur, between
two major spiral arms, Sagittarius and Perseus
Stars and Galaxies
There are about 100 billion - 100,000,000,000 stars in the Milky Way Galaxy
The Milky Way is a slightly undersized, fairly
normal galaxy.
There are trillions - 1,000,000,000,000++ galaxies in the observable universe
Milky Way
We are about 25,000 light years from
galactic centre
galaxy as a whole is about 50,000 or so
light years in radius (the edge is not
sharp) embedded in a dark halo that is
maybe 500,000 light years across.
We are part of a local group of galaxies
that is about 3 million light years in radius
NOT the Milky Way...
Yan Sun et al ApJL Jan 2015
http://iopscience.iop.org/2041-8205/798/2/L27/
Andromeda Galaxy
Elliptical Galaxies
Spiral Galaxies
Irregular
Barred
Clusters of Galaxies
http://htwins.net/scale2/
The Known Universe: https://www.youtube.com/
watch?v=17jymDn0W6U
Earth Size Comparison: https://www.youtube.com/
watch?v=1Eh5BpSnBBw
What we see…
There is more to the universe than what we see
This is true in more than one way:
there is stuff in the local universe we can not detect
directly but know of due to its indirect effects
there is stuff further out in the universe than we can
currently see directly
this is probably quite important…
STOP
Scale
Powers of Ten:
http://www.powersof10.com
http://www.powersof10.com/film
http://youtu.be/0fKBhvDjuy0
Local Group
Andromeda galaxy is the local big galaxy
we have a few smaller galaxies and a few
dozen dwarves. Typical, and problematic.
Local Clusters
Bigger scales - for friday.
Need - local clusters - Virgo/Fornax/Coma
~ 100 Mpc scale images
SDSS/6DF
UDF/Sims -- 4-6 images