Our Place in Space

Where we are

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We live on Earth

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Welcome to Earf!

Earth orbits the Sun

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The Earth is in the Solar System

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The Solar System is the Milky Way

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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

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We do not know what that is. Yet.

There are billions of galaxies

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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!