6.3 (Term 2) Flashcards
Learning Intentions Represent distances in space with the use of scientific notation Calculate distances in light years
What is the astronomic unit?
The first measurement needed is the distance from Earth to the Sun.
Who devised a method to measure the astronomical unit (AU), and what does it involve?
Halley devised a method involving two observers on Earth measuring the transit of Venus across the Sun’s face, using geometry and the principle of parallax.
What is parallax?
Parallax is the apparent movement of an object due to the actual movement of the observer.
What is the approximate value of the astronomical unit (AU)?
The astronomical unit (AU) is approximately 150 million kilometers.
How is the distance to stars outside our Solar System measured?
Using parallax.
What is a parsec?
Distance for an object with a parallax angle of one arcsecond.
How many AU are in one parsec?
206,265 AU.
Who first observed stellar parallax in 1838?
Friedrich Bessel.
What was the early 1900s view of galaxies?
Believed there was only one galaxy with the Sun near its center.
How many galaxies are estimated to exist now?
About 2 trillion galaxies.
What did Einstein’s theory of special relativity state about light?
Light always travels at the same speed.
What is a light-year?
The distance light travels in one year.
How many parsecs is one light-year?
0.306 601 parsecs.
How many AU are in one light-year?
63,241 AU.
Is a light-year a measure of time?
No, it’s a measure of distance.
