HS-ESS1-1NGSS*ScienceEarth and Space ScienceGrades 9-12
HS-ESS1-1: Modeling the Sun's Life Span and How Fusion Energy Reaches Earth
In plain English: HS-ESS1-1 is the NGSS high school performance expectation that asks students to build an evidence-based model of the sun: how nuclear fusion in the core releases energy, how that energy moves outward and reaches Earth as radiation, and how long the sun will shine. It is usually taught in Earth and Space Science, sometimes in Physics.
Develop a model based on evidence to illustrate the life span of the sun and the role of nuclear fusion in the sun's core to release energy that eventually reaches Earth in the form of radiation.
Clarification Statement: Emphasis is on the energy transfer mechanisms that allow energy from nuclear fusion in the sun's core to reach Earth. Examples of evidence for the model include observations of the masses and lifetimes of other stars, as well as the ways that the sun's radiation varies due to sudden solar flares ("space weather"), the 11-year sunspot cycle, and non-cyclic variations over centuries.
Assessment Boundary: Assessment does not include details of the atomic and sub-atomic processes involved with the sun's nuclear fusion.
Next Generation Science Standards · Disciplinary Core Idea: Earth's Place in the Universe · Official standard
Students build and revise a model of the sun that answers two questions: how does energy released in the core end up as sunlight on Earth, and how long can the sun keep shining? They trace energy from fusion in the core through the radiative and convection zones to the photosphere and across space, use the sun's measured output to estimate how fast it uses its hydrogen, and test the model against evidence from other stars and from changes in the sun's own radiation.
The NGSS Clarification Statement says: "Emphasis is on the energy transfer mechanisms that allow energy from nuclear fusion in the sun's core to reach Earth. Examples of evidence for the model include observations of the masses and lifetimes of other stars, as well as the ways that the sun's radiation varies due to sudden solar flares ("space weather"), the 11-year sunspot cycle, and non-cyclic variations over centuries." The Assessment Boundary says: "Assessment does not include details of the atomic and sub-atomic processes involved with the sun's nuclear fusion." On this page fusion is described only as hydrogen nuclei combining into helium, with a small fraction of the mass released as energy; the step-by-step nuclear reactions are beyond this standard. Every data set labeled invented is made up for teaching but patterned on real measurements. Constants used: solar luminosity 3.83 × 10²⁶ W, solar mass 1.99 × 10³⁰ kg, Earth-sun distance 1.496 × 10¹¹ m, speed of light 3.00 × 10⁸ m/s, 1 year = 3.16 × 10⁷ s.
Learning Objectives
By the end of this lesson, students will be able to:
Develop a labeled model that traces energy from fusion in the sun's core, through the radiative and convection zones, to radiation that reaches Earth
Use the sun's luminosity and E = mc² to estimate how much mass the sun converts to energy each second and how long its core hydrogen will last
Use the masses and lifetimes of other stars as evidence for the sun's life span and its future stages
Analyze data on solar flares, the 11-year sunspot cycle and the Maunder Minimum, and explain how each changes the radiation reaching Earth
Critique and revise a model of the sun when new evidence does not fit it
Prior Knowledge Required
Students should already be comfortable with:
Scale properties of objects in the solar system MS-ESS1-3
Waves and electromagnetic radiation being reflected, absorbed or transmitted MS-PS4-2
Conduction, convection and radiation as ways thermal energy moves
Scientific notation and unit conversions HSN.Q.A.1
Project a photo of the sun taken through a solar filter (never look at the sun directly or through binoculars). Give students one minute alone, then two with a partner.
Warm-Up Prompt
"The sunlight hitting your skin right now left the sun's surface a few minutes ago. Sketch where you think that energy was before it reached the surface, and list two things you would need to measure to predict how much longer the sun can shine."
Collect sketches without correcting them. Many students draw a single straight arrow from the center of the sun to Earth, or imagine the sun as a burning ball of gas. Keep two or three sketches on the board: the class revises them at the end of the lesson.
Direct Instruction15-20 minutes
The model. Show Diagram 1. In the core, where the temperature is about 15 million K, hydrogen nuclei fuse into helium. The helium has slightly less mass than the hydrogen that formed it: about 0.7% of the fused mass becomes energy, E = mc². That energy moves outward in two different ways. In the radiative zone, radiation is absorbed and re-emitted by the dense gas so many times that estimates of the escape time range from about ten thousand to more than a hundred thousand years. In the convection zone, hot gas rises, releases energy at the top and sinks again, like water boiling in a pot. The photosphere, at about 5,800 K, emits the radiation that crosses space to Earth in a little over 8 minutes.
The life span. A star like the sun shines steadily while it fuses hydrogen in its core (the main sequence). Rocks from meteorites date the solar system at about 4.6 billion years, so the sun has been on the main sequence for about that long. When the core hydrogen runs out, models and observations of older stars of similar mass show that the sun will swell into a red giant, later shed its outer layers, and end as a small, cooling white dwarf. It does not have enough mass to explode as a supernova.
Energy path and travel time
Sunlight leaves the photosphere and travels 1.496 × 10¹¹ m to Earth at 3.00 × 10⁸ m/s. How long does the last step of the energy path take, and how does it compare with the time energy spends inside the sun?
Result: t = d/v = 1.496 × 10¹¹ m ÷ 3.00 × 10⁸ m/s ≈ 499 s ≈ 8.3 minutes. The trip through space is tiny next to the thousands of years energy spends working its way out of the radiative zone.
Mass converted to energy each second
Satellites and the solar constant give the sun's luminosity as 3.83 × 10²⁶ W (joules per second). How much mass does the sun convert to energy each second?
Result: m = E/c² = 3.83 × 10²⁶ J ÷ (3.00 × 10⁸ m/s)² ≈ 4.26 × 10⁹ kg each second, about 4 million metric tons. Because only 0.7% of fused hydrogen becomes energy, the core fuses about 4.26 × 10⁹ ÷ 0.007 ≈ 6.1 × 10¹¹ kg of hydrogen per second.
Estimating the sun's life span
Models show that about 10% of the sun's mass is core hydrogen that can fuse while the sun is on the main sequence. Use a fusion rate of 6.08 × 10¹¹ kg/s and a solar mass of 1.99 × 10³⁰ kg.
Result: Fuel = 0.10 × 1.99 × 10³⁰ = 1.99 × 10²⁹ kg. Time = 1.99 × 10²⁹ ÷ 6.08 × 10¹¹ ≈ 3.27 × 10¹⁷ s ≈ 1.0 × 10¹⁰ years. With 4.6 billion years used, about 5.4 billion years of main-sequence life remain.
Evidence from other stars
Star clusters and binary stars show that a star's luminosity rises steeply with mass, roughly as M³·⁵. A simple fuel model then gives a main-sequence lifetime t ≈ 10 billion years × (M/Msun)-2.5. How long does a star with twice the sun's mass last?
Result: t ≈ 10 × 2-2.5 ≈ 1.8 billion years. It has twice the fuel but about 11 times the luminosity, so it runs out much sooner. The sun's own 10-billion-year estimate fits the same pattern.
A solar flare changes the radiation
A satellite that measures solar X-rays records 1.0 × 10⁻⁶ W/m² before a flare and 2.0 × 10⁻⁴ W/m² at its peak 12 minutes later. The sun's total output barely changes.
Result: Ratio = 2.0 × 10⁻⁴ ÷ 1.0 × 10⁻⁶ = 200. The X-ray part of sunlight rose 200-fold in minutes. It reaches Earth about 8 minutes after it leaves the sun and can disrupt radio signals on the daylit side of Earth.
After each example, ask: "Which part of the model does this number test, and what evidence gave us the input?" Point out that the model has three kinds of time: minutes for radiation to cross space, thousands of years for energy to leave the interior, and billions of years for the fuel to run out.
Guided Practice15 minutes
Pairs build a model poster from evidence. Each pair gets the five evidence cards in the table below and must decide which part of the model each card supports, then draw and label the model so that every arrow is backed by at least one card.
Guided practice evidence cards
Card
Observation
Part of the model it supports
1
Filtered images of the photosphere show bright cells about 1,000 km across, each rising and fading within about 10-20 minutes
Students decide
2
Models that match the sun's size, mass and brightness give a core temperature of about 15 million K and a surface of about 5,800 K
Students decide
3
Meteorites and the oldest Moon rocks are about 4.5-4.6 billion years old
Students decide
4
In old star clusters the most massive stars are missing from the main sequence, while stars like the sun remain
Students decide
5
Satellites above the atmosphere measure about 1,361 W/m² of sunlight at Earth's distance
Students decide
Sort the cards: which ones are evidence about how energy moves, and which ones are evidence about how long the sun lasts?
Draw the sun's layers with radii roughly to scale (core 0.25, radiative zone to 0.70, convection zone to 1.00 of the radius) and label the energy transfer mechanism in each layer.
Add a timeline beside the sun: formation, now (4.6 billion years), end of the main sequence (about 10 billion years), red giant, white dwarf. Mark which cards support it.
Write one sentence about a part of the model that no card supports yet, and what evidence would test it.
Circulate and ask each pair to point to the arrow that crosses space. Card 1 supports convection (rising and sinking cells), card 2 supports fusion in a hot core, cards 3 and 4 support the time scale, and card 5 is the energy that reaches Earth. Pairs revise their warm-up sketches.
Independent Practice10-15 minutes
Each student uses Diagram 2 (invented yearly sunspot numbers) and the invented satellite readings below of total solar irradiance, the sunlight power per square meter at Earth's distance.
Invented total solar irradiance readings
Year
1986
1989
1997
2000
2008
Irradiance (W/m²)
1360.6
1361.7
1360.6
1361.6
1360.5
Students (1) find the length of each sunspot cycle in Diagram 2, (2) compare irradiance in sunspot-maximum years with sunspot-minimum years and express the change as a percent of about 1,361 W/m², and (3) add the 11-year cycle to their model poster as a small, repeating change in the radiation that leaves the photosphere. Ask: does a sun with more dark spots send us more energy or less, and how do the data show it?
Closure5 minutes
Exit ticket: "Telescope records from about 1645 to 1715 show almost no sunspots for seventy years, a gap called the Maunder Minimum. (1) Is this a cyclic or a non-cyclic change? (2) Where does it belong in your model? (3) Name the three ways energy moves between the core and your skin, in order." Return to the warm-up sketches and ask what the class would change.
Differentiation Strategies
For Struggling Students
Give a partly drawn model with the layers already outlined, so students add the mechanisms, arrows and evidence card numbers
Provide a calculation frame for scientific notation: write the numbers, divide the leading digits, then subtract the exponents
Pair the three time scales with familiar comparisons: minutes (a class change), thousands of years (all of recorded history), billions of years (Earth's age)
For Advanced Students
Ask students to estimate how much the sun's mass will drop over its whole main-sequence life and explain why that does not end the main sequence
Have students compare a model in which the sun burns like coal with the fusion model, and name the evidence that rules out chemical burning
Ask students to predict how the life span changes if the usable fraction of core hydrogen were 12% instead of 10%, and explain which evidence would pin that fraction down
Assessment Guidance
What to Look For
Check that models show two different transfer mechanisms inside the sun (radiation in the radiative zone, convection near the surface) and radiation across space, not a single straight arrow. Look for life-span reasoning that divides a fuel supply by a rate of use and ties the result to evidence such as the ages of meteorites or star clusters. Listen for students who say the sun burns, who think sunspots make the sun dimmer overall, or who expect the sun to become a supernova.
02
Classroom Activities
3 Activities
1
Scale Model: From the Core to a 9 mm Earth
25 minGroups of 3-4
Groups build a scale model in which the sun is 1.0 m across, draw its layers on chart paper and then walk the distance to Earth with a tape measure. The walk makes the energy path and its time scales concrete.
Procedure
Tape two sheets of chart paper together and draw a circle of radius 50 cm with string and a pencil. Draw the core (radius 12.5 cm) and the top of the radiative zone (radius 35 cm).
Label each layer with its energy transfer mechanism and draw a zigzag in the radiative zone and loops in the convection zone.
Compute the scale distance to Earth: 1.496 × 10¹¹ m ÷ 6.96 × 10⁸ m (the sun's radius) ≈ 215 solar radii, so 215 × 0.50 m ≈ 107 m. Earth's diameter at this scale is about 9 mm.
Carry the 9 mm bead 107 m down a hallway or across the field, and place it. Safety: stay on paths the teacher has cleared, and walk.
Discussion Questions
At this scale, radiation covers the 107 m walk in 8.3 minutes. The energy took thousands of years to cross the 35 cm radiative zone drawing. Which step of the path is the slow one, and why?
Earth is a 9 mm bead 107 m from a 1 m sun. What does that suggest about how much of the sun's radiation Earth intercepts?
What part of your model would you need to change if the sun had no convection zone?
Modification for Distance Learning
Students build the model at home with a 1 m circle of string on the floor, then use an online map to find a landmark about 107 m from their door and post a photo with their labels.
2
Space Weather Data Stations
25 minGroups of 3-4
Four stations each hold an invented data set patterned on real records. At each one, groups decide what kind of change in the sun's radiation the data show (sudden, cyclic or non-cyclic), how large it is, and how to add it to their model.
Station Data (invented)
Station 1, a flare: X-ray flux 1.2 × 10⁻⁶, 1.3 × 10⁻⁶, 8.0 × 10⁻⁶, 6.0 × 10⁻⁵, 3.0 × 10⁻⁵ and 1.0 × 10⁻⁵ W/m² at 08:00, 08:04, 08:08, 08:12, 08:16 and 08:20.
Station 2, sunspot minima: 1856, 1867, 1878, 1889, 1901, 1913.
Station 4, radio blackout days per year and yearly sunspot number: 2008: 0 days, 5; 2010: 8 days, 25; 2012: 70 days, 85; 2014: 120 days, 115; 2016: 20 days, 40; 2018: 1 day, 7.
Discussion Questions
At Station 1 the X-ray flux peaks at 50 times its 08:00 value within 12 minutes. Why does Earth feel the change about 8 minutes after it happens on the sun?
At Station 2, what is the average time between minima? Is every cycle exactly the same length?
At Station 3, the six decades from the 1650s through the 1700s all average 3 or fewer sunspots. Why is this called non-cyclic?
At Station 4, the year with the most sunspots also has the most blackout days. What link between flares and the sunspot cycle does this suggest?
Challenge Variation
Groups rank the three kinds of change by how much they alter the total energy reaching Earth and by how much they alter X-rays and ultraviolet, then explain why the two rankings differ.
3
Stellar Fuel Budget: Testing the Life Span Model
20 minPairs
Each pair receives a star card with a mass and a luminosity (in units of the sun's) taken from the simple model L ≈ M³·⁵. They compute a lifetime with t ≈ 10 billion years × M ÷ L, add it to a class table, and compare the results with what astronomers see in star clusters.
Star Cards
Card A: 0.5 solar masses, luminosity 0.088
Card B: 1 solar mass, luminosity 1
Card C: 2 solar masses, luminosity 11.3
Card D: 5 solar masses, luminosity 280
Card E: 10 solar masses, luminosity 3,160
Card F: 20 solar masses, luminosity 35,800
Discussion Questions
Cards A-F give lifetimes of about 57, 10, 1.8, 0.18, 0.032 and 0.0056 billion years. Why does the star with the most fuel run out first?
A cluster is 100 million years old. Which card stars could still be on the main sequence? (Cards A, B, C and D; E and F would already be gone.)
No star with the mass on Card A has ever left the main sequence. How does the age of the universe, about 13.8 billion years, support that claim?
Modification for Distance Learning
Pairs enter the cards in a shared spreadsheet, graph lifetime against mass, and post one sentence that uses the graph as evidence for the sun's life span.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: How Fusion Energy Leaves the Sun and Reaches Earth
A model of the energy path. The core, radiative zone and convection zone are drawn with their radii to scale. Energy released by fusion in the core moves outward by radiation, then by convection, and leaves the photosphere as radiation that reaches Earth about 8.3 minutes later. The zigzag stands for radiation being absorbed and re-emitted many times; the real path has far more steps.
Diagram 2: The Sunspot Cycle (Invented Data)
Invented yearly mean sunspot numbers for 1986-2008, drawn to scale and patterned on the real record. Minima fall in 1986, 1997 and 2008, 11 years apart, and maxima in 1989 and 2000. Students use this graph with the irradiance table in Independent Practice.
04
Homework Assignment
~30 min
HS-ESS1-1 Homework: Modeling the Sun's Energy and Life Span
Directions: Data sets are invented for practice unless the problem says otherwise. Use the constants from the lesson: luminosity 3.83 × 10²⁶ W, speed of light 3.00 × 10⁸ m/s, 1 year = 3.16 × 10⁷ s. Show each calculation with units, and end every problem with a sentence that names your evidence.
Part 1: The Energy Path (Problems 1-2)
Mars orbits about 2.28 × 10¹¹ m from the sun. (a) How many minutes does sunlight take to reach Mars? (b) Sunlight spreads over a sphere of area 4πd². How much solar power reaches each square meter at Mars's distance? (c) What fraction of Earth's 1,361 W/m² is that, and what does the answer tell you about how radiation spreads out?
A classmate's model says: "Fusion energy leaves the core and reaches the sun's surface in about 8 minutes. Then it travels to Earth by convection." Identify the two errors, explain what evidence or reasoning shows each one is wrong, and redraw the model correctly with each mechanism labeled.
Part 2: The Sun's Life Span (Problems 3-4)
The sun converts about 4.26 × 10⁹ kg of mass to energy each second. (a) How much mass will it convert over a 10-billion-year main-sequence life? (b) What percent of the sun's 1.99 × 10³⁰ kg is that? (c) Use your answer to explain why the main sequence ends because the core runs low on hydrogen, not because the sun runs out of mass.
Astronomers study a star cluster in which stars of about 1.5 solar masses are just now leaving the main sequence. Use the model t ≈ 10 billion years × M-2.5 (M in solar masses). (a) Estimate the age of the cluster. (b) Would a star like the sun in this cluster still be on the main sequence? (c) A star of 0.8 solar masses has a model lifetime longer than the age of the universe (13.8 billion years). Show this, and explain what it predicts about finding such stars as white dwarfs.
Part 3: Changes in the Sun's Radiation (Problems 5-6)
Sunspot minima occurred in 1954, 1964, 1976, 1986, 1996 and 2008 (real dates, given as the year in which each minimum fell). (a) Find each interval and the average cycle length. (b) Predict the year of the next minimum. (c) Satellites show the total irradiance changes by about 0.1% over a cycle. How many W/m² is that out of 1,361 W/m²? (d) Explain in two sentences how to show this cycle in your model of the energy that reaches Earth.
An X-ray satellite records 2.0 × 10⁻⁶ W/m² before a flare and 5.0 × 10⁻⁵ W/m² at its peak. Separately, carbon records in tree rings point to a long low in solar activity from about 1460 to 1550, called the Spörer Minimum. (a) By what factor did the X-ray flux rise? (b) How long did the low-activity period last? (c) Classify each change as sudden, cyclic or non-cyclic, and explain how each one would change the radiation part of your model.
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
Energy Path Model
Model shows fusion in the core, radiation then convection inside the sun, and radiation across space, each labeled
Model has the right layers but a missing or wrong mechanism
Calculations with Units
Travel times, intensities, mass rates and lifetimes computed correctly with units and sensible rounding
Correct method with one arithmetic, exponent or unit error
Use of Evidence
Names specific data (star lifetimes, sunspot dates, X-ray readings) and explains what each shows about the model
Evidence named but not connected to a part of the model
Model Revision
Explains clearly how the model changes to include flares, the 11-year cycle and long-term variations
Mentions a change but does not say where it belongs in the model
05
Quiz: 20 Questions
Interactive, with answers
Instructions
Data sets are invented unless a question says otherwise. Use luminosity 3.83 × 10²⁶ W, speed of light 3.00 × 10⁸ m/s and 1,361 W/m² at Earth. Your score updates as you answer, and Reset quiz clears everything so you or your students can try again.
Multiple choice: pick an option to check it. Short answer: write your answer, then reveal the model answer.
0 of 20 answered · 0 correct
Question 1 of 20 · Multiple Choice
In a model of the sun, where is the energy that becomes sunlight first released?
Answer: C
Fusion needs the very high temperature and density of the core, about 15 million K. Choice A is wrong because the photosphere, at about 5,800 K, emits the light but does not produce the energy. Choice B names a layer that carries energy outward but does not release it.
Question 2 of 20 · Multiple Choice
Which statement about where the sun's energy comes from fits the evidence?
Answer: A
Fusion turns about 0.7% of the fused mass into energy, E = mc². Choice B describes a chemical reaction, which could not keep the sun shining for billions of years. Choice C cannot explain a steady output over the 4.6-billion-year age shown by meteorites.
Question 3 of 20 · Multiple Choice
Which order correctly lists how energy moves from the sun's core to your skin?
Answer: B
Energy moves by radiation through the radiative zone, by convection in the outer layer, and by radiation through empty space. Choice A reverses the inner layers and names conduction in space, where there is no matter to conduct. Choice D ignores the convection zone seen as rising and sinking cells on the surface.
Question 4 of 20 · Multiple Choice
Venus orbits about 1.08 × 10¹¹ m from the sun. About how long does sunlight take to reach Venus?
Answer: D
t = 1.08 × 10¹¹ m ÷ 3.00 × 10⁸ m/s = 360 s = 6.0 minutes. Choice C leaves the answer in seconds but labels it minutes. Choice A is the time for Earth, which is farther away.
Question 5 of 20 · Multiple Choice
Jupiter is about 7.78 × 10¹¹ m (5.2 times Earth's distance) from the sun. About how much solar power reaches each square meter at Jupiter's distance?
Answer: B
Intensity falls with the square of distance: 1,361 ÷ 5.2² ≈ 50 W/m², the same as 3.83 × 10²⁶ ÷ (4π(7.78 × 10¹¹)²). Choice A divides by 5.2 instead of 5.2². Choice C assumes the radiation does not spread out.
Question 6 of 20 · Multiple Choice
A sunlike star's energy took thousands of years to leave its interior but only minutes to reach a planet. What does the model say causes the long delay?
Answer: B
Between absorptions the radiation travels at light speed, but it is absorbed and re-emitted so many times, in random directions, that the net outward trip takes thousands of years or more. Choice A misreads the delay as a slower speed. Choice C is wrong because fusion in the core releases energy steadily.
Question 7 of 20 · Multiple Choice
A star in another system has the same mass as the sun, so the model gives it the same 10-billion-year main-sequence life. Radioactive dating of material around it gives an age of 7.5 billion years. Which prediction fits the model?
Answer: D
7.5 ÷ 10 = 0.75, so the star has used three quarters of its main-sequence time and has about 10 - 7.5 = 2.5 billion years left. Choice A confuses a million with billions. Choice B would need an age above 10 billion years. Choice C ignores that the core hydrogen is used up at a known rate.
Question 8 of 20 · Multiple Choice
Observations of older stars that have about the sun's mass suggest what future for the sun after its main sequence?
Answer: C
Stars with about the sun's mass end as white dwarfs after a red giant stage, and the glowing shells they shed are seen around many such stars. Choices A and B happen only to stars much more massive than the sun. Choice D describes no observed stage of a sunlike star.
Question 9 of 20 · Multiple Choice
Use the model t ≈ 10 billion years × M-2.5 (M in solar masses). About how long is the main-sequence life of a star of 3 solar masses?
Answer: C
32.5 ≈ 15.6, and 10 ÷ 15.6 ≈ 0.64 billion years, or about 640 million years. Choice A assumes more fuel means a longer life and multiplies by 3. Choice B divides by 3 and ignores how steeply luminosity rises with mass. Choice D is off by a factor of ten.
Question 10 of 20 · Multiple Choice
Observations show that a star with 15 times the sun's mass has about 13,000 times its luminosity. What does this evidence imply for the model?
Answer: A
Fifteen times the fuel used about 13,000 times as fast gives a lifetime about 15/13,000 of the sun's 10 billion years, roughly 11 million years. Choice B counts the fuel but ignores the rate of use. Choice D does not follow: the data describe how fast fusion runs, not a new energy source.
Question 11 of 20 · Multiple Choice
Satellite data show that total solar irradiance is slightly higher at sunspot maximum than at sunspot minimum. What is the best explanation?
Answer: D
Sunspots are cooler and darker, but the bright regions around active areas outweigh them, so the total rises by about 0.1%. Choice A is wrong because sunspots look dark exactly because they are cooler. Choice C is wrong: the cycle is a surface magnetic effect, and energy from the core takes thousands of years to reach the surface anyway.
Question 12 of 20 · Multiple Choice
During a large flare, an X-ray satellite reading rises 300-fold in 15 minutes, while total solar irradiance changes by less than 0.01%. Which conclusion do these data support?
Answer: A
X-rays carry only a tiny share of the sun's output, so a 300-fold jump in X-rays hardly moves the total. Choice B contradicts the irradiance reading. Choice C is wrong because energy from the core takes thousands of years to reach the surface, so a 15-minute event cannot come from the core.
Question 13 of 20 · Multiple Choice
Sunspot records show that cycles were unusually weak from about 1790 to 1830, a stretch of about 40 years called the Dalton Minimum, after which stronger cycles returned. What kind of evidence is this for the model?
Answer: C
A decades-long weak stretch that does not repeat on a regular schedule is a non-cyclic variation, the kind of long-term change the model has to allow. Choice A is the opposite of what the record shows. Choice B is wrong because energy leaving the core takes thousands of years to reach the surface, so a 40-year change cannot come from the core.
Question 14 of 20 · Multiple Choice
A student claims the sun could be a giant ball of burning coal. Which evidence best rules this out?
Answer: B
The energy a chemical fuel could supply, divided by the sun's luminosity, gives a lifetime far shorter than the 4.6 billion years dated in meteorites. Choice A is about color, not energy. Choice C is weaker evidence because the claim could include oxygen in the fuel.
Question 15 of 20 · Short Answer
Coal releases about 3 × 10⁷ J per kilogram when it burns. If the entire 1.99 × 10³⁰ kg sun were coal burning at 3.83 × 10²⁶ W, about how many years would it last? What does the result say about the sun's energy source?
Energy = 1.99 × 10³⁰ × 3 × 10⁷ ≈ 6.0 × 10³⁷ J. Time = 6.0 × 10³⁷ ÷ 3.83 × 10²⁶ ≈ 1.6 × 10¹¹ s ÷ 3.16 × 10⁷ s per year ≈ about 5,000 years. Meteorites show the sun has shone for about 4.6 billion years, so a chemical source is ruled out; fusion, which releases far more energy per kilogram, fits the evidence.
Question 16 of 20 · Short Answer
A student's model shows fusion in the core, one straight arrow through the whole sun, and a wavy arrow to Earth labeled "heat conduction." Name two changes that would make the model match the evidence.
(1) Inside the sun, show two mechanisms: radiation that is absorbed and re-emitted many times in the radiative zone, then convection in the outer layer, seen as rising and sinking cells on the surface. (2) Relabel the arrow to Earth as radiation: conduction needs matter, and space between the sun and Earth is nearly empty.
Question 17 of 20 · Short Answer
A 1.0 m² solar panel faces the sun above the atmosphere, where sunlight delivers 1,361 W/m². How much energy reaches the panel in one hour? Where in the sun did that energy start?
E = 1,361 W × 3,600 s ≈ 4.9 × 10⁶ J. The energy was released by fusion in the core, worked its way out by radiation and convection over thousands of years, and crossed space as radiation in about 8 minutes.
Question 18 of 20 · Short Answer
A star cluster is 1.0 billion years old. Using t ≈ 10 billion years × M-2.5, which stars in it have already left the main sequence? Explain how this kind of cluster data is evidence for the sun's life span.
Set 10 × M-2.5 = 1, so M = 100.4 ≈ 2.5 solar masses: stars more massive than about 2.5 suns have left; stars of smaller mass, including sunlike ones, remain. Clusters of different ages show the cutoff moving to lower mass as they age, which tests the same model that gives the sun about 10 billion years.
Question 19 of 20 · Short Answer
Sunspot minima occurred in 1755, 1766, 1775, 1784 and 1798 (real dates, given as the year in which each minimum fell). Find the average cycle length. Is the cycle perfectly regular? Use the intervals as evidence.
Intervals: 11, 9, 9 and 14 years. Average = (1798 - 1755) ÷ 4 ≈ 10.75, about 11 years. The cycle is not perfectly regular: single cycles ranged from 9 to 14 years, so the model should show an average period with real variation.
Question 20 of 20 · Short Answer
In four or five sentences, use your model to explain how energy released in the sun's core reaches Earth and why the sun will not shine the same way forever. Name at least two pieces of evidence.
Model answer: Hydrogen fuses into helium in the core, and a small fraction of the mass becomes energy. The energy moves out by radiation through the radiative zone and by convection near the surface, then leaves the photosphere as radiation that reaches Earth in about 8 minutes. The core has a limited supply of hydrogen, used at about 6 × 10¹¹ kg per second, so the main sequence lasts about 10 billion years. Evidence: convection cells on the surface, the 1,361 W/m² measured at Earth, the 4.6-billion-year age of meteorites, and clusters where more massive stars have already left the main sequence. Rubric: full credit names the core, both inner mechanisms, radiation across space, a limited fuel supply and two specific pieces of evidence.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does HS-ESS1-1 mean?
HS-ESS1-1 asks students to develop a model, based on evidence, of how long the sun will last and how fusion in its core releases energy that reaches Earth as radiation. The code means High School, Earth and Space Science, core idea 1 (Earth's Place in the Universe), performance expectation 1. The focus is on the model and the evidence behind it, not on memorizing layer names.
Is HS-ESS1-1 taught in Earth science or physics?
It is usually taught in Earth and Space Science, often in an astronomy unit. Some schools place it in Physics or in an integrated science course, because the energy calculations use E = mc², intensity and scientific notation.
Do students need to know the proton-proton chain for HS-ESS1-1?
No. The Assessment Boundary excludes the atomic and sub-atomic details of fusion. Students should know that hydrogen nuclei combine into helium in the core and that a small fraction of the mass is released as energy. The individual reaction steps are beyond this standard.
How do scientists know how old the sun is?
Mainly from radioactive dating of meteorites, which formed with the solar system about 4.6 billion years ago. Models of the sun that match its present mass, size and brightness give a similar age, and so do the oldest rocks from Earth and the Moon.
How is HS-ESS1-1 usually assessed?
With tasks that ask students to build, use or critique a model rather than recall facts. A typical task gives data, such as star masses and lifetimes or a sunspot record, and asks students to explain what it shows about the sun's energy or life span. Constructed-response items often ask students to fix a flawed diagram of the energy path.
Why is the sun's life span only an estimate?
Because it rests on model inputs that are known only approximately, above all the fraction of the sun's hydrogen that can fuse in the core, about 10%. The sun also brightens slowly as it ages, so its rate of fuel use is not perfectly constant. That is why lessons give about 10 billion years rather than an exact figure.
Is it safe to observe the sun in class?
Only with the right equipment. Never look at the sun directly or through binoculars, a telescope or a camera without a certified solar filter. Pinhole projectors and online images from solar observatories and satellites are safe ways to see sunspots, and they are all this lesson needs.
What is space weather, and why is it in HS-ESS1-1?
Space weather means sudden changes in the sun's output, such as flares, and the effects they have near Earth, such as radio blackouts and disturbances to satellites. The Clarification Statement lists flares as evidence that the sun's radiation varies, so students should add sudden changes to their model alongside the 11-year cycle and slower, non-cyclic changes.
Does the sunspot cycle cause climate change on Earth?
The 11-year cycle changes the total sunlight by only about 0.1%, which is small, and it goes up and down rather than in one direction. Longer, non-cyclic changes such as the Maunder Minimum may have contributed to cool periods, and scientists still study how much. How changes in incoming energy affect climate is the subject of HS-ESS2-4.
What math do students use in an HS-ESS1-1 lesson?
Scientific notation, unit conversions, dividing distance by speed, E = mc², and dividing a fuel supply by a rate of use. The inverse-square idea for sunlight spreading out is helpful but optional. The math serves the model: each number tests one part of it.
07
Related Standards
5 standards
These standards connect to HS-ESS1-1: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
MS-ESS1-3Prerequisite
Analyze and interpret data to determine scale properties of objects in the solar system
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