☀️ The Sun: Our Star

What you’ll learn

1. What the Sun IsSee the Sun as an ordinary nearby star: its mass, mix, age, and why you must not stare at it.The Sun is a G-type star about 150 million kilometers away. NASA puts about 99.8 percent of the solar system's mass in it; about 109 Earths fit across its face. By number of atoms it is mostly hydrogen. Meteorites date it to about 4.6 billion years. Never look at it unfiltered.
2. The Fusion EngineUnderstand core fusion, the proton-proton chain, and why sunlight is both eight minutes old and ancient.The core, about 15 million °C, fuses hydrogen into helium through the proton-proton chain. Four protons become one helium nucleus; the missing mass is energy. Light then takes tens of thousands of years to random-walk out, and eight minutes 20 seconds to reach Earth.
3. Layers of the SunName the layers and the coronal heating mystery, including how helium got its name.Energy moves from core through the radiative and convective zones to the photosphere. Above lie the chromosphere and corona. The corona is over a million degrees, still unexplained. Janssen and Lockyer found helium in the Sun in 1868. The corona streams away as the solar wind.
4. Sunspots and the Magnetic CycleExplain sunspots, the 11-year cycle, the 22-year Hale cycle, and the Maunder Minimum without overclaiming climate.Sunspots are cooler, intensely magnetic regions. Their numbers rise and fall over about 11 years; the poles flip, making a full magnetic cycle about 22 years. The Maunder Minimum (about 1645–1715) saw almost no spots. It overlapped the Little Ice Age but did not, on NASA's reading, start it.
5. Space WeatherSeparate flares from CMEs, and ground the hazard in Quebec 1989 and Carrington 1859.Flares are radiation flashes; CMEs are clouds of plasma that take one to three days to arrive. On 13 March 1989 about six million people in Quebec lost power for nine hours. The 1859 Carrington storm sparked telegraphs. NOAA now forecasts this weather.
6. Watching the Sun — and How It EndsKnow how we watch the Sun from space, what Parker did, and the red-giant then white-dwarf ending.SOHO (1995) and SDO (2010) watch continuously. Parker, launched 12 August 2018, entered the corona on 28 April 2021. In about five billion years the Sun becomes a red giant, then a white dwarf. It will not go supernova. What heats the corona remains unsolved.

Questions this course answers

Grounded in trusted sources

• NASA Science — Our Sun: Facts (about 99.8% of solar-system mass; core ~15 million °C; photosphere ~5,500 °C; another ~5 billion years; red giant will engulf Mercury and Venus, and possibly Earth) — https://science.nasa.gov/sun/facts/
• NASA GSFC ISTP Sun facts — more than 99.8% of solar-system mass; 109 Earths across the disk; interior could hold over 1.3 million Earths — https://pwg.gsfc.nasa.gov/istp/outreach/workshop/thompson/facts.html
• NASA StarChild — every second a star like the Sun converts about 4 million tons of its material into heat and light — https://starchild.gsfc.nasa.gov/docs/StarChild/questions/question13.html
• NASA Science — There Is No Impending Mini Ice Age (Maunder Minimum 1645–1715; Little Ice Age began earlier; volcanic aerosols likely played the title role) — https://science.nasa.gov/earth/climate-change/there-is-no-impending-mini-ice-age/
• NASA / Johns Hopkins APL — Parker Solar Probe (launched 12 August 2018; first spacecraft through the low corona; NASA: 'touched the Sun,' 28 April 2021) — https://parkersolarprobe.jhuapl.edu/The-Mission/index.php
• NOAA NESDIS — When Solar Storms Attack (13 March 1989 Quebec: about six million without power for nine hours; 1859 Carrington Event sparked telegraphs) — https://www.nesdis.noaa.gov/news/when-solar-storms-attack-space-weather-and-our-infrastructure
• NOAA Space Weather Prediction Center — watches, warnings, and the L1 solar-wind monitor — https://www.swpc.noaa.gov/
• APS News — helium first seen in the solar spectrum, 1868 (Janssen and Lockyer); named for Helios — https://www.aps.org/archives/publications/apsnews/201409/physicshistory.cfm

Every Wunder lesson is built from real, reputable sources — never invented.

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