Astronomy Exam 1

What is a solar system?

A star and all the material that orbits it, including its planets and moons

What is a planet?

A moderately large object that orbits a star

What is a moon?

An object that orbits a planet

What is a sun?

A large, glowing ball of gas that generates heat and light through nuclear fusion

What is an asteriod?

A relatively small and rocky object that orbits a star

What is a comet?

A relatively small and icy object that orbits a star

What is a galaxy?

A great island of stars in space, all held together by gravity and orbiting a common center

What is the universe?

The sum total of all matter and energy

What is an astronomical unit?

The average distance between the Earth and the Sun, about 150 million km or 93 million miles

What is a light year?

The distance that light can travel in 1 year, about 10 trillion km

What is the speed of light?

300,000 km/s

Why do we see far away things back in time?

Light travels at a finite speed, the further away the further back in time we are looking

How many stars are in the Milky Way?

About 100 billion

How many galaxies are there?

About 100 billion

How did galaxies come to be?

Gravity drove collapse of matter into galaxies and galaxy clusters

How do stars come to be?

Gravity drives collapse of clouds of gas and dust to form stars and planets, born when gravity compresses the material to dense enough state for nuclear fusion

How can we determine the age of the solar system?

Radiometric dating

What is a half life?

The time for half the nuclei in a substance to decay

What does the universe look like from Earth?

With the naked eye, we can see more than 2000 stars, as well as the Milky Way.

What is a constellation?

A region of the sky.

How many constellations are there in the sky?

Eighty eight

Where is the North celestial pole?

Directly above Earth’s North Pole

Where is the South celestial pole?

Directly above Earth’s South pole

What is the celestial equator?

A projection of Earth’s equator onto the sky

What is the ecliptic?

The Sun’s apparent path through the celestial sphere

What is the zenith?

The point directly overhead

What is the horizon?

All points 90 degrees away from the Zenith

What is the Meridian?

The line passing through the zenith and connecting the north and south points on the horizon

Why do stars rise and set?

The Earth rotates from west to east, so stars appear to circle from east to west

What is latitude?

Position north or south of equator

What is longitude?

Position east or west of prime meridian

Where does the prime meridian run through?

Greenwich, England

What causes the seasons?

Axis tilt

Why do we see phases of the moon?

Half the Moon is lit by the Sun; half is in shadow, it’s appearance to us is determined by relative positioning

What causes a lunar eclipse?

Earth’s shadow on the Moon

What causes a solar eclipse?

Moon’s shadow on Earth

How did Copernicus, Tycho, and Kepler challenge the Earth centered idea?

Copernicus created a Sun centered model, Tycho provided the data, and Kepler found a model that fit the data

What is Kepler’s first law of planetary motion?

The orbit of each planet is an ellipse with the Sun at one focus.

What is Kepler’s second law of planetary motion?

As a planet moves around its orbit it sweeps out equal areas in equal times.

What is Kepler’s third law of planetary motion?

More distant planets orbit the Sun at slower average speeds: p^2 = a^3

What was Galileo’s role in solidifying the Copernican revolution?

His experiments and observations overcame the remaining objections to the Sun-centered solar system model

How many arcminutes are in a degree?

60

How do you calculate angular size?

Physical size times ((360 degrees) divided by (2pi times distance))

How does a object’s angular size appear if it’s further away?

Smaller

What is a parsec?

A unit of distance, equal to about 3.26 ly (D = 1/p’’) pc

How can we distinguish science from non science?

Science seeks explanations that rely solely on natural causes

What is a scientific theory?

A mathematical construct that explains a wide variety of
observations in terms of a few general principles and that has
survived repeated and varied testing.

Does astrology have any scientific validity?

No more accurate than pure chance, so no

What are particles of light called?

Photons

What is a wave?

A pattern of motion that can carry energy without matter

What is a wavelength?

The distance between two wave peaks

What is frequency?

The number of times person that a wave vibrates up and down

What does a shorter wavelength mean?

Higher frequency

What is an atomic number?

The number of protons in a nucleus

What is an atomic mass number?

Number of protons + neutrons

What do molecules consist of?

Two or more atoms

What do isotopes consist of?

Same number of protons but different number of neutrons

How does light tell us what things are made of?

Through chemical fingerprints, a set of unique energy levels

What is a light wave?

A vibration of electric and magnetic fields

Can human eyes see most forms of light?

No

What is the entire range of wavelengths known as?

The electromagnetic spectrum

How does light tell us the temperatures of planets and stars?

Nearly all large or dense objects emit a continuous spectrum
that depends on temperature.

What is refraction?

The bending of light when it passes from one substance into another

What is a focus?

A single point where all refracted rays point

What do eyes use to focus light?

Refraction

What is the focal plane?

The plane where light from different directions come into focus

What side is the image behind a single convex lens?

Upside down

Why don’t we see things upside down?

Our brains automatically compensate

What do cameras use to refract light?

Detectors

What types of detectors are used in digital cameras and modern telescopes?

CCD detectors

What do astronomers do to images they take?

They use computer software to combine, sharpen or refine images

What are the two most important properties of a telescope?

Light collecting area - more light in less time, angular resolution - greater detail

What is angular resolution?

The minimum angular separation that the telescope can distinguish

What is the limit of angular resolution known as?

The diffraction limit

What does a refracting telescope focus light with?

A lens

What does a reflecting telescope focus light with?

Mirrors

What are most modern telescopes?

Reflectors

What do astronomers do with telescopes?

Imaging, spectroscopy, and time monitoring

What is imaging?

Taking pictures of the sky, astronomical detectors can record bands of light our eyes can’t see

What is spectroscopy?

Breaking light into spectra

What is time monitoring?

Measuring how light output varies with time

What is a spectrograph?

A graph that separates the different wavelengths of light before they hit the detector

What is light pollution caused by?

Scattering of human-made light

Who has been building satellites that have interfered with astronomical imaging?

Starlink

What types of light pass easily through Earth’s atmosphere?

Radio and visible light

What are all the different types of light?

Gamma ray, x-ray, ultraviolet, visible, infrared, radio

What are radio telescopes essentially?

Large satellite dishes

What does a satellite dish do?

Reflects radio waves from a large area into a single receiver

Why do x-ray and gamma ray telescopes need to be in space?

These light waves can’t pierce Earth’s atmosphere

What are terrestrial planets?

Rocky, relatively small planets that are close to the sun

What are jovian planets?

Gaseous, larger planets that are further from the sun

What does the solar system look like?

Planets orbit Sun in the same direction and in nearly
the same plane.

What can we learn by comparing the planets to one
another?

Those patterns give us insight into the general
processes that govern planets.

What are examples of terrestrial planets?

Mercury, Venus, Earth, Earth’s Moon, Mars

What is Earth’s core made of?

Highest density; nickel and iron

What is Earth’s mantle madeo f?

Moderate density; silicon ,oxygen, etc

What is Earth’s crust made of?

Lowest density; granite, basalt, etc

What are seismic waves?

Vibrations that travel through Earth's interior tell us what Earth is like on the inside.

What is a lithosphere?

A planet’s outer layer of cool, rigid rock

What is geological activity?

Activity such as volcanic eruptions, earthquakes, and erosion caused by interiors heating up and cooling off