Star Brightness
This medium-sized star looks like the biggest and brightest star in our sky because it is closest to Earth.
What is the Sun?
Earth takes this many hours to complete one full rotation on its axis.
What is 24 hours?
It takes Earth exactly this long to complete one full orbit around the sun.
What is one year?
It takes the moon about this many days to orbit the Earth once.
What is 28 days?
This is the force of attraction that keeps the Moon in orbit around Earth and Earth in orbit around the Sun.
What is gravity?
This is the term for how bright a star actually is, regardless of how far away it is from Earth.
What is absolute brightness (or luminosity)?
Earth's rotation causes this daily pattern of light and darkness.
What is day and night?
Earth's orbit, combined with the tilt of its axis, causes this pattern of changing weather and temperatures.
What are the seasons?
We see different phases of the moon because the moon reflects light from this object as it orbits Earth.
What is the sun?
The North Star, used for navigation for centuries, is also known by this scientific name.
What is Polaris?
This is the term for how bright a star looks to us when we gaze up at it from Earth.
What is apparent brightness?
Because Earth rotates from west to east, the sun, moon, and stars appear to rise in this direction.
What is the east?
This is the word used to describe Earth's movement as it travels in a path around the sun.
What is revolution?
This is the phase of the moon where it looks like a complete, bright circle in the sky.
What is a full moon?
Even though this object is much smaller than any star in the night sky, it looks much larger to us because it is only about 238,900 miles away from Earth.
What is the moon?
If two stars have the exact same actual size and energy output, the star that is closer to Earth will look this way compared to the farther one.
What is brighter?
This is the imaginary line running through the center of the Earth from the North Pole to the South Pole that the Earth spins around.
What is the axis?
Because Earth orbits the sun, we see different groups of these in the night sky at different times of the year.
What are constellations?
When the moon appears to be growing larger each night, it is given this descriptive term.
What is waxing?
This is a huge, glowing ball of gas, mostly made of hydrogen and helium, held together by its own gravity.
What is a star?
These are the two main factors that determine how bright a star appears to an observer on Earth.
What are size and distance?
This changes in length and direction throughout the day because of the changing angle of the sun caused by Earth's rotation.
What is a shadow?
This is the shape of Earth's orbit around the sun, which is slightly oval rather than a perfect circle.
What is an ellipse?
When the moon is completely dark and invisible to us from Earth, it is in this phase.
What is a new moon?
This term describes the rise and fall of ocean water levels, which are caused by the gravitational pull of the Moon and the Sun.
What are tides?