Astronomy Exam 1

A galaxy contains...

Contains lots of gas, dust, and stars.

Largest astronomical scale

Size of a typical galaxy

Scale model of solar system (Sun = tennis ball)

Inner planets within ~12 yards; Pluto over half a mile away

Light-year misuse in ads

A light-year is a unit of distance, not time.

Signal from Andromeda Galaxy 2.5 million light-years away,

Would take 2.5 million years to reach us.

Distant galaxies

Seen as they were when they were young

5.3 × 10⁻⁴ meters

0.53 millimeters

Scientific models

Make specific predictions that can be tested through observations or experiments

Science

Progresses through testing models against observations

Scientific theory

Must make testable predictions that can be proven wrong

Big Dipper visibility

Not visible from the South Pole

Celestial Equator from North Pole is...

Invisible below the horizon

The Big Dipper is close to your northern horizon, so where will it be in 6 hrs

Moves 90° counterclockwise (to the right of Polaris)

North Celestial Pole from Equator

On the horizon due north

Polaris visibility

Always above the northern horizon

How to determine latitude at sea

Measure the altitude of Polaris at midnight

Orion in June at midnight is...

Not visible near midnight

If the full Moon is rising in the east in 6hrs it will...

Still full 6 hours later

The moon phase between first quarter and full

Waxing gibbous Moon

Total lunar eclipse visibility can be seen...

By anyone on the nighttime side of Earth

Moon with a larger orbit would have...

No total eclipse of the Sun

Visible planets in October evenings

Saturn and Jupiter

Object never in retrograde motion

The Moon

Retrograde motion explanation

Inner planets move faster and overtake outer ones

Do close or far stars show more parallax?

Closer stars

Disproof of Ptolemy's model

Observed phases of Venus

Eris and Pluto are both...

Dwarf planets

True or False... Our solar system is located in the center of the Milky Way Galaxy

False

Earth's orbit shape → Nearly circular (observed fact).

Are aliens helping me study science or non-science?

Non-Science

Moon and Sun angular size are...

Approximately the same (0.5°)

Stars south of celestial equator from North Pole are...

Never visible

One side of the Moon is visible due to...

Synchronous rotation

The Meridian in sky runs...

North to south through zenith

Path of Sun during year...

The Ecliptic

Hierarchy of the universe

Planets → Stars → Solar Systems → Galaxies

Closest astronomical structure to us

The solar system

Use of scientific notation in astronomy

To express very large or small numbers efficiently

AU and light years

AU measures distances within the solar system; light years measure distances between stars and galaxies

Implication of light years

Shows how far light travels in a year and lets us look back in time

Scientific model

A simplified representation used to explain and predict phenomena

Hallmarks of science

Testable predictions, repeatability, peer review, and falsifiability

Pseudoscience

A belief or practice that claims to be scientific but lacks evidence and cannot be tested

Constellation

A pattern of stars recognized in Earth's sky

Celestial sphere

A model that maps the sky as if stars lie on a sphere surrounding Earth

Cause of daily star motion

Earth's rotation

Using stars to determine latitude

By observing the altitude of Polaris or other stars

Why different stars are visible in different seasons

Because of Earth's orbit around the Sun

Retrograde motion

Apparent motion caused when Earth overtakes another planet in orbit

Cause of Moon phases

The Moon's position relative to Earth and the Sun

Why eclipses don't happen every month

The Moon's orbit is tilted relative to Earth's orbit

Parallax

Apparent shift in star position due to Earth's motion; proves Earth orbits the Sun

Model ruled out by Venus's phases

Ptolemy's geocentric model

Fix for Copernicus' model inaccuracies

Kepler's elliptical orbits

Evidence for Earth's rotation

Foucault pendulum and Coriolis effect

Three criteria for a planet

Orbits the Sun, nearly round shape, and clears its orbital path

Why Pluto is not a planet

It doesn't dominate its orbit

Dwarf planet

Meets first two criteria of a planet but not the third

Asteroid characteristics

Rocky, irregular, mostly between Mars and Jupiter

Comet characteristics

Icy, elliptical orbits, often from the Kuiper Belt or Oort Cloud

Kuiper Belt vs Oort Cloud

Kuiper Belt objects orbit in the ecliptic plane; Oort Cloud objects have random orientations