5-ESS1-1: Why the Sun Looks Brighter Than Other Stars
Also called NGSS 5-ESS1-1 · Topic: Space Systems: Stars and the Solar System · Earth and Space Science
The Official Wording
Support an argument that differences in the apparent brightness of the sun compared to other stars is due to their relative distances from the Earth.
Assessment boundary: Assessment is limited to relative distances, not sizes, of stars. Assessment does not include other factors that affect apparent brightness (such as stellar masses, age, stage).
NGSS Lead States, 2013 · Read it on nextgenscience.org · checked October 15, 2026
What 5-ESS1-1 Means in Plain English
Fifth graders argue, using evidence, that the sun outshines every other star because it is so much closer to us. They compare matching lights at different distances, then connect the pattern to space, where the next nearest star is about 270,000 times farther away.
The argument rests on distance alone. How big, heavy or old a star is stays out of it, even though those things matter too. It builds on sky patterns from 1st grade (1-ESS1-1) and leads to the scale of the solar system (MS-ESS1-3).
5-ESS1-1 I Can Statements
- I can explain that the sun is a star.
- I can show that a closer light looks brighter than a farther one.
- I can argue that the sun looks brightest because it is closest.
5-ESS1-1 Worked Example
A test a class can run in a gym with the lights off, using two matching flashlights and a measuring tape.
Does the same light look dimmer when it is farther away?
Set It Up: Two identical flashlights with fresh batteries, a measuring tape, and a gym or long hallway with the lights off.
- Turn both flashlights on and hold them side by side, pointed at the class.Both look equally bright
- One helper stands 2 meters from the class while the other walks back to 20 meters.2 m and 20 m
- Each student rates both lights from 1 for dim to 5 for dazzling.Near light: mostly 5s. Far light: mostly 1s and 2s
- Swap the flashlights between helpers and rate them again.The near one still looks brighter
- Compare the gym distances with real ones in space.Sun: 150 million km. Next star: about 40 trillion km
The same flashlight looked much dimmer from 20 meters than from 2 meters, so distance alone changed how bright it seemed.
Why it works: Light spreads out as it travels, so less of it reaches your eyes from a faraway source, which is why our nearby star looks so much brighter than the distant ones.
Common Mistakes with 5-ESS1-1
Thinking the sun is not a star
“Stars are tiny sparkles. The sun is something different.”
Try this: The sun is a star like the ones at night. It looks like a blazing disk only because it is so close.
Thinking the sun is the biggest star
“The sun is brightest because it's the biggest star.”
Try this: Many stars are bigger than the sun. Its nearness is what makes it look brightest from Earth.
Changing two things in the light test
A new flashlight at the far spot and an old one at the near spot
Try this: Use two matching flashlights with fresh batteries, then swap them, so distance is the only thing that changes.
Where 5-ESS1-1 Fits
Practice 5-ESS1-1
Quick Check
- Is the sun a star?
- Two identical lamps are 5 meters and 50 meters away. Which looks brighter?
- Why do other stars look like tiny dots?