U2: Astronomy - Measuring Space Distances . FLIP LESSON. On the Move.
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Nothing in space or our universe stays still. Planets, moons, stars, and galaxies are in constant motion. They are moving due to the expansion of the space in the universe. Space has no known boundaries. The location of Earth in space is relative to other moving objects.
Each object in space will move through space in proportion to the expansion of space. Think of the Earth and other objects in space as raisins in rising bread dough. As the dough expands or rises, the raisins move away from each other. Such is how objects move through space.
Astronomers use several methods to measure space distances. Lasers, radio and radar waves have helped us measure distances accurately. By using the known distances of closer stars, the distance to further stars can be found. A measurement called the parallax is used for this.
Astronomers use units of measure that express vast distance with small numbers. For shorter measurements in our solar system the astronomical unit (AU) is used. One AU is about 150,000,000 kilometers or 93,000,000 miles. One AU equals the average distance from the Earth to the Sun.
An AU is a standard of distance used within the solar system
The Inner Planets
Sizes to Scale
Mercury Venus Earth and MoonMars
The Outer Planets
Earth Included for Scale.
Diameters of Solar System Members:
Sun = 1,392,000 km
Mercury = 4,878 km
Venus = 12,104 km
Earth = 12,756 km
Mars = 6,794 km
Jupiter = 142,984 km
Saturn = 120,536 km
Uranus = 51,118 km
Neptune = 49,530 km
Pluto = 2,304 km
Mean Distance from Sun
57,900,000 km = 0.387 AU
108,200,000 km = 0.723 AU
149,600,000 km = 1.000 AU
227,900,000 km = 1.524 AU
778,300,000 km = 5.203 AU
1,427,000,000 km = 10.07 AU
2,871,000,000 km = 19.19 AU
4,497,000,000 km = 30.06 AU
5,914,000,000 km = 39.53 AU
Earth’s Moon = 3,476 km Mean Distance from Earth = 384,400 km
over 1,000 miles-per-hour.
The light year is the most well-known space distance unit used for measuring distances outside our solar system. It is equal to the distance light will travel in one year. Light travels 300,000 kilometers or 186,000 miles per second. A light year (LY) is over 9,000,000,000,000 kilometers or 5,865,696,000,000 miles long.
A Light Year is a standard unit of measure for interstellar (star) distances beyond the solar system.
Milky Way Galaxy is approx. 100,000 LY across in distance
If the Sun and Earth were 1 foot apart …
Proxima Centauri is 51 miles away!
Proxima (or Alpha Centauri C) is a red dwarf foot apart …
Alpha Centauri A is a yellow star
Alpha Centuari B is an orange star
For measuring distances between galaxies, the parsec is used. A parsec is equal to 3.26 light years.
One parsec equals 206,000 AU’s or about 30,000,000,000 kilometers.
distances between galaxies
800,000 parsecs away from Earth.
million light years
It is important to consider time. Time is related to distance. The light you view from an object 100 light years away left the object 100 years ago. You are looking back into time 100 years. You see the object only as it once was and where it was years ago.
In the same way, our sun is 8.33 light minutes away. If the sun exploded it would take us 8.33 min. to see the explosion.