Ch 1 txtbk questions + assignment qs Flashcards
(18 cards)
The star Betelgeuse is about 600 light-years away. If it explodes tonight,
(a) we’ll know because it will be brighter
than the full Moon in the sky.
(b) we’ll know because debris from the explosion will rain down on us from space.
(c) we won’t know about it until about 600 years from now
c
Light from Betelgeuse takes about 600 years to travel to Earth. So if it exploded tonight, the light from that explosion wouldn’t reach us until 600 years later. We would only see it then, not right away.
If stars existed but galaxies did not,
(a) we would probably
still exist anyway.
(b) we would not exist because life on
Earth depends on the light of galaxies.
(c) we would not exist because we are made of material that was recycled in galaxies.
c
Galaxies are where stars are born, live, and die. When massive stars die (in supernovae), they recycle elements like carbon, oxygen, and iron—the building blocks of planets and life—into space. These elements are later used to form new stars, planets, and eventually life.
The age of our solar system is about
(a) one-third of the age
of the universe.
(b) three-fourths of the age of the universe.
(c) 2 billion years less than the age of the universe
a
The fact that nearly all galaxies are moving away from us, with more distant ones moving faster, helped us to conclude that
(a) the universe is expanding.
(b) galaxies repel each other like magnets.
(c) our galaxy lies near the center
of the universe.
a
This observation, known as Hubble’s Law, shows that the farther away a galaxy is, the faster it appears to be moving away from us. This pattern only makes sense if space itself is expanding, stretching the distances between galaxies.
Briefly describe the major levels of structure (such as planet, star, galaxy) in the universe.
Here’s a brief description of the major levels of structure in the universe, from smallest to largest:
- Planet – A round object that orbits a star; Earth is a planet.
- Star – A massive, glowing ball of gas (like the Sun) that produces energy through nuclear fusion.
- Planetary System – A star and everything that orbits it, including planets, moons, asteroids, and comets (e.g., the Solar System).
- Galaxy – A huge collection of stars, gas, dust, and dark matter bound together by gravity (e.g., the Milky Way).
- Galaxy Group – A small collection of galaxies that are gravitationally bound (e.g., the Local Group).
- Galaxy Cluster – A larger grouping of hundreds to thousands of galaxies.
- Supercluster – A vast region of space containing many galaxy clusters (e.g., the Laniakea Supercluster).
- Universe – All of space and time, including all matter, energy, galaxies, and cosmic structures.
What do we mean when we say that the universe is expanding,
and how does expansion lead to the idea of the Big Bang
and our current estimate of the age of the universe
When we say the universe is expanding, we mean that space itself is stretching, causing galaxies to move farther apart over time. This isn’t because galaxies are flying through space, but because the fabric of space is growing, increasing the distance between galaxies.
How this leads to the Big Bang:
If galaxies are moving away from each other now, then in the past, they must have been CLOSER together. By running the expansion backward in time, scientists concluded that the universe began as a hot, dense point — a singularity — about 13.8 billion years ago. This event is called the Big Bang.
Estimating the Age of the Universe:
By measuring how fast galaxies are moving apart (Hubble’s Law) and calculating the rate of expansion, astronomers can estimate how long the universe has been expanding. This gives us the universe’s current age: about 13.8 billion years.
Briefly explain Earth’s daily rotation and annual orbit, defining the terms ecliptic plane and axis tilt.
Earth’s Daily Rotation:
Earth rotates once every 24 hours on its axis, an imaginary line running from the North Pole to the South Pole. This rotation causes day and night, as different parts of Earth face toward or away from the Sun.
Earth’s Annual Orbit:
Earth orbits the Sun once every year (about 365.25 days). This path is nearly circular and lies in a flat plane called the ecliptic plane.
Ecliptic Plane:
The ecliptic plane is the imaginary flat surface formed by Earth’s orbital path around the Sun. It’s used as a reference for the positions of planets and constellations in the sky.
Axis Tilt:
Earth’s axis is tilted at an angle of about 23.5° relative to the ecliptic plane. This axis tilt is responsible for the seasons, because it affects how sunlight hits different parts of Earth during its orbit.
So, Earth’s daily rotation gives us day and night, and its tilted annual orbit around the Sun creates the changing seasons.
Briefly describe our solar system’s location and motion within the Milky Way Galaxy
Our solar system is located about 27,000 light-years from the center of the Milky Way Galaxy, in one of its spiral arms called the Orion Arm.
Motion:
The solar system orbits the center of the galaxy at a speed of about 800,000 km/h (500,000 mph).
It takes roughly 230 million years to complete one full orbit around the galactic center — this is called a galactic year.
Which of the following statements are false? Select all that apply.
a) Pluto and Mercury are the two smallest planets.
b) Venus and Uranus both have spins tilted compared to their orbits.
c) The moons of Earth and the Moons of Jupiter are both geologically inactive.
d) Io and Earth both have volcanoes.
e) Both Venus and Mercury lack moons.
a) and c)
Which of these are possible situations?
a) The Earth’s casts a shadow on the moon during the Waning Gibbous phase.
b) The Moon blocks the Sun’s light from reaching Earth during a New Moon.
c) There is a lunar eclipse in the same week as a solar eclipse.
d) An annular lunar eclipse occurs during a New Moon.
e) A New Moon is visible from Toronto at midnight.
b
Planet A and Planet B orbit the same star. Which of the following is correct? Select all that apply.
a) If planet A is twice as far as planet B, Planet A could have an orbital period twice as long if their masses were identical.
b) If Planet B has an orbital period that is eight times the length of Planet A, it could have a semi-major axis that is four times longer than Planet A.
c) If planet B is two times more massive than Planet A, Planet A’s year is half the length of Planet B’s.
d) If planet A is four times more massive than planet B, Planet B could have an orbital period twice as long as A.
b) and d)
What conclusions can be drawn from applying Kepler’s Laws?
- keplers laws can describe the motion of the moons
- a planet with a larger semi-major axis will take longer to complete an orbit
Which of the following is part of the reason that we observe the cycle of phases of the Moon from Earth?
a) The Moon orbits the Sun.
b) Clouds partially obstruct our view of the Moon.
c) We only see the part of the Moon illuminated by the Sun.
d) The amount of light emitted by the Moon changes as it rotates.
e) The Earth casts a shadow on the Moon.
c)
Earth has a 23-degree axial tilt and a nearly circular orbit. Imagine the Earth’s axial tilt was increased to 90 degrees. Which of the following best describes how the seasons would change?
a) during summer, the sun would never be visible
b) summer would be colder
c) the planet would never have summer
d) during the winter, the sun would never be visible
d
Let’s assume you have set up camp on the center of the side of the Moon facing Earth. Then if people on Earth were seeing a lunar eclipse, you would see..
a solar eclipse
Which of the following statements about the ecliptic and the celestial sphere is TRUE?
a) If a constellation is located near the north celestial pole, someone in Australia should be able to see it every night of the year.
b) If a constellation is located near the celestial equator, someone in France should be able to see it every night of the year.
c) Constellations that are located near the ecliptic are visible about half the year.
d) When the Sun is on the celestial equator, it’s summer in Toronto.
c
If a rocky object is orbiting the Sun between the terrestrial planets and Jovian planets, in a near circular orbit, hasn’t cleared its path, and isn’t spherical, how can it be categorized?
asteroid
Which of the following is in the correct order from smallest to largest orbit size?
a) Ceres
Earth
Io
Pluto.
b) Io
Mercury
Pluto
Sun.
c) Earth
Moon
Jupiter
Uranus.
d) Mars
Uranus
Ceres
Sun.
b)
