Scale of the Universe - Lecture Flashcards

Flashcards covering key concepts from the lecture notes on the scale of the universe and solar system.

What is the Astronomical Unit (AU) defined as?

The average distance between the Earth and the Sun.

The most common element in the universe is

Hydrogen.

What is a light year?

The distance that light travels in one year.

For scientists, an element is defined by

the number of protons in its nucleus.

The location of the Earth in the Milky Way Galaxy is

a little less than 30,000 LY from the center.

Sort the celestial objects in order of size (largest to smallest).

Universe > Galaxy > Solar System > Star > Planet.

What is the name of the point directly above your head?

Zenith

Retrograde motion

When a planet appear to move backwards in the sky from Earths perspective

Prograde motion

Motion in the same direction as the dominant orbital direction of a system

Classical astronomers, like Ptolemy, could or could not explain Retrograde motion with their models

Could explain

{who} observed gibbous phases of {what} as evidence for the heliocentrism of our solar system

Galileo, Venus

Parallax

The apparent shift in the direction of an object as a result of the motion of the observer

Apparent magnitude

A measure of how bright a star looks in the sky; the larger the number, the dimmer the star appears to us

Celestial equator

A great circle on the celestial sphere 90 degrees from the celestial poles; where the celestial sphere intersects the plane of Earths equator

Which of the following was not done by Hipparchus, the great ancient astronomer

Explained retrograde motion

A satellite in a circular orbit and then burns thrusters to increase speed slightly, what happens

Its orbit would become more elliptical

A rocket blasts its engines long enough to reach escape velocity from the surface of earth. What is its orbital shape?

None, will fly away from earth

What is the semi-major axis it the orbital period is 2 years?

1.59AU