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Our Place in Space
Where we are
1
We live on Earth
2
Welcome to Earf!
Earth orbits the Sun
3
The Earth is in the Solar System
4
The Solar System is the Milky Way
5
The Milky Way is a galaxy
A galaxy is a massive gravitationally bound system
that consists of stars and stellar remnants gas and dust dark matter
6
We do not know what that is. Yet.
There are billions of galaxies
7
Scale of the Universe
This stuff is FAR!
Sizes of things
Earth diameter: 13,462 Km Mars diameter: 6,800 Km
About ½ Earth Jupiter diameter: 142,984
10+ times the Earth 1,000+ Earths would fit inside
Sun diameter: 1.4 million kilometers 109 times Earth, almost 10 times Jupiter 1,000,000 Earths would fit inside
Distance Ladder
Distance to the Sun
Earth is 149,597,871 Km from the Sun 92,955,807 miles
This distance is 1 astronomical unit AU
Astronomical Unit Mercury is .4 AU from the Sun Venus is 0.72 AU Mars is 1.52 AU Jupiter is 5.2 AU Saturn is 9.5 AU Uranus is 19.6 AU Neptune is 30 AU Kuiper Belt is 30 to 50 AU Oort Cloud is 50,000 to 100,000 AU!
Edge of the solar system Heliosphere - The bubble in the interstellar
medium of space caused by the Sun’s wind
Beyond the solar system
Beyond the solar system, the astronomical unit becomes too small Like measuring distance
around USA in millimeters Need a bigger unit of
measure – the Light Year (LY)
Light Year – distance light can travel in one year
Beyond the solar system
Oort Cloud is about 2 LY in diameter Nearest star, Proxima Centauri, is 4.22 LY Center of Milky Way is 26,000 LY Milky way is 100,000 LY across Nearest Galaxy, Andromeda, is 2.5 million LY
away
Voyager 1 will take 18,000 years to go 1 LY
How do we know this? Measurement to distant objects is done with
trigonometry Parallax - difference in the apparent position
of an object viewed along two different lines of sight
Beyond the Light Year
Parsec – uses parallax Parallax of 1 arcsecond 3.26 LY pc
Beyond the Light Year
Parsec is for really big distances Proxima Centauri = 1.29 parsecs Galaxy RXJ1242-11 = 200 million pc Edge of observable universe 14 billion pc
Distance Ladder
Spectroscopic Parallax
Uses the color of a star to determine its absolute brightness
Compared to apparent brightness to determine distance
Spectroscopic Parallax Imagine a distance candle The closer it is, the brighter it looks If you can measure how bright it looks, you can
tell how far away it is
Distance Ladder
Cepheid in Virgo
Cepheid Variables Cepheids pulsate on a regular frequency
Days to months The slower they pulse, the brighter they are Determine how fast it pulses, determine its magnitude Determine the magnitude, determine the distance
Distance Ladder
Supernova! Sometimes a star dies in a
massive explosion called a supernova
Certain ones are called Type 1A All Type 1A supernovae are
exactly the same brightness. Measure its brightness and
determine the distance
Distance Ladder
This stuff is FAR!
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