The universe and space distances
What is a galaxy and how many stars are in a galaxy?
A collection of a billion stars, gas, dust, and other objects held together by gravity.
What force keeps planets orbiting the Sun?
Gravity.
What star is closest to Earth?
The Sun
n the heliocentric model, what object is at the center of the solar system?
The Sun.
What is a hypothesis?
A testable explanation or prediction based on observations.
Does the Sun appear to move across the sky in the geocentric model, the heliocentric model, or both?
What is both?
Which is largest: a planet, a solar system, a galaxy, or the universe?
The universe
How does the length of a planet's year generally change as its distance from the Sun increases?
The year becomes longer.
What star color is generally associated with the highest temperatures: red or blue?
Blue
In the geocentric model, what object was believed to be at the center of the solar system?
Earth.
Scientists usually say results "support" a hypothesis rather than "prove" it.
Because scientific knowledge can change with new evidence and cannot be proven with absolute certainty.
Geocentric, heliocentric, or both: In which model does the Moon orbit Earth?
What is both?
Why do scientists use light-years instead of miles or kilometers to describe distances between stars and galaxies?
Because distances in space are so enormous that light-years are a more practical measurement.
Which planetary property is most likely to decrease as distance from the Sun increases: average temperature, length of year, or orbit size?
Average temperature.
What is the difference between apparent brightness and luminosity?
Apparent brightness is how bright a star looks from Earth; luminosity is how much light the star actually produces.
How did gravity help form the solar system?
Gravity pulled together gas and dust, forming the Sun, planets, and other objects.
During an investigation, what is the independent variable?
The variable that is intentionally changed by the scientist.
According to the Law of Universal Gravitation, what role did gravity play in the formation of the solar system?
What is gravity pulled matter together to form the Sun, planets, moons, and their orbits?
A star appears brighter than another star in the night sky. Give one reason this might happen besides the star actually producing more light
It may be closer to Earth.
Earth has one moon. Another planet has several moons and a much thicker atmosphere. Name two ways scientists can compare that planet to Earth
Possible answers include atmosphere thickness, number of moons, gravity, temperature, distance from the Sun, or orbital characteristics.
How can a solar flare affect Earth?
It can interfere with satellites, communications, GPS systems, and power systems.
Why do scientists use models when studying the solar system?
Models help represent objects, distances, motions, and processes that are too large or complex to observe directly.
A student's hypothesis is not supported by the evidence. Why is the investigation still valuable?
The results can lead to new questions, revised hypotheses, and further investigations.
What are the three factors of a planets orbit?
Gravity, speed, and direction
Two stars appear equally bright when viewed from Earth. Scientists discover that Star A is much farther away than Star B. What can be concluded about the stars' luminosities, and what evidence supports that conclusion?
Star A must have a greater luminosity because it appears just as bright as Star B despite being much farther away. The evidence is the combination of apparent brightness and distance.
Scientists discover two planets orbiting the same star. Planet X is much farther from the star than Planet Y. Predict two differences scientists would expect to observe and explain your reasoning.
Planet X would likely have a lower average temperature and a longer year. Greater distance from the star means it receives less energy and takes longer to complete an orbit.
A red star and a blue star appear to be the same size. Using what you know about star color and temperature, explain which star is likely producing more energy and why.
The blue star is likely producing more energy because blue stars have higher surface temperatures than red stars. Higher temperatures generally indicate greater energy output.
A student claims that planets continue orbiting the Sun because there is no gravity in space. Use evidence from the Law of Universal Gravitation to evaluate this claim.
The claim is incorrect. Gravity exists throughout space and continuously pulls planets toward the Sun. This gravitational attraction keeps planets in orbit instead of moving in a straight line.
A group of students investigates whether distance from a star affects planetary temperature. Their data shows that planets farther away are generally colder. Why should the students conclude that the evidence supports the claim rather than proves it?
The evidence supports the claim because future observations could reveal additional factors or exceptions. Scientific explanations are always open to revision based on new evidence.
Gravity increases with increasing mass, and decreases with increasing distance.