Our Place in Space

The Scale of the Universe

• Imagine (don’t write down):– You are driving on the 401 at 100km/h– You accelerate until you are going 280 times as

fast– You head toward Neptune. How long do you think

it will take you to get there?

Answer: 50 years

The Scale of the Universe

• https://www.youtube.com/watch?v=The Scale of the Universe AMNH

Measuring Distances

• One of the biggest challenges astronomers face in modeling and mapping the universe is measuring distances.

Astronomical Range Typical UnitsDistances to satellites kilometresPlanetary distances astronomical units Distances to nearby stars parsecs, light-yearsDistances at the galactic scale kiloparsecsDistances to nearby galaxies megaparsecs

Measuring Distances

• Astronomical Unit (AU): ~150 million kilometers (average distance from Earth to Sun)– Useful for measuring distances in the solar system

Measuring Distances

• Astronomical units are a more manageable way to measure distances.

Measuring Distances

• Light Year (ly): The distance that it takes light to travel in one Earth year= 63 241.077 astronomical units= 9.46 x 1012 km

Measuring Distances

• The Sun is ~0.000016 ly away from Earth. Light from the Sun takes ~0.000016 years (or 8 minutes) to reach us.

Measuring Distances

• Parsec (pc): equal to 3.26 light years– Good for measuring large distances (galaxies,

galaxy clusters

Think-Pair-ShareWhat unit might you use to measure the

distance to?

• A meteor burning up in Earth’s Atmosphere

• The next nearest star to our sun

• The distance to the Andromeda galaxy

• Distance to Neptune

• Kilometers

• Light years

• Parsecs

• Light years

Parallax

• Parallax is a tool used to measure distances to stars.

• Parallax is the change in position of an object viewed from two different locations

• Example: pointing to an object, closing an eye

As the distance increases, the parallax angle decreases.

Overview of Our Solar System

• Consists of:– The sun– Eight Planets & their moons– Dwarf planets– All other celestial objects travelling around the sun

(e.g. Comets, meteors, etc.)

The Planets

• To be a ‘planet’, a celestial object must:– Be in orbit around a star (eg. The sun)– Have enough mass to be pulled into a stable shape

by gravity– Dominate its orbit

Dwarf Planets

• A dwarf planet is a celestial object that orbits the sun and has a spherical shape but does not dominate its orbit

Dwarf Planets

• There are currently 5 dwarf planets: – Ceres– Pluto– Haumea,– Makemake– Eris

Dwarf Planets

• Astronomers estimate there may be up to 2000 dwarf planets, with many located in the Kuiper Belt region of the solar system.

Moons and Satellites

• A moon is a type of satellite: a celestial object that travels around a planet in a closed path.

To date, Saturn has had 53 moons identified!

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