Key Takeaways:
- The Sun's structure includes the photosphere (visible surface), chromosphere (reddish layer above the photosphere), and corona (outermost layer with extremely high temperatures).
- The Sun emits a continuous solar wind, impacting Earth's aurorae and potentially disrupting communications.
- Sunspots, cooler regions caused by magnetic field concentrations, exhibit an approximately 11-year cyclical pattern, with historical records dating back to the 4th century B.C., including the Maunder Minimum (1645-1715).
- The Sun's distance from Earth (1 astronomical unit) varies throughout the year due to Earth's elliptical orbit, and the Sun, located 27,200 light-years from the galactic center, completes a galactic orbit in approximately 225-250 million years.
If you missed my first 10 cool things about the Sun, you can read them here. Now you’re ready for 10 more.
11. Astronomers call the Sun’s visible surface the photosphere. Its thickness ranges from tens of miles to a few hundred miles.
12. The chromosphere is a layer about 1,200 miles thick that lies above the photosphere. “Chromo” means “color,” and this region got its name from the reddish flash often seen just before and just after totality during a total solar eclipse.
13. Above the chromosphere is the corona. It has an average temperature between 1.8 and 3.6 million degrees Fahrenheit, but its hottest regions zoom to 36 million degrees Fahrenheit.
14. The Sun emits a continuous stream of plasma called the solar wind. On Earth, the most visible effect of the solar wind is the production of the northern and southern lights, the aurorae. Intense bursts of solar wind also can disrupt communications, especially those that route through orbiting satellites.
15. Sunspots appear dark because can be as much as 2,700 degrees Fahrenheit (1,482 degrees Celsius) cooler than the surrounding surface. They are concentrations of the Sun’s magnetic field where it breaks through the photosphere causing the region to radiate less energy.
16. Records of sunspots date to the 4th century B.C. During the past 100 years, observers have reported between 40,000 and 50,000 sunspots. The numbers ebb and flow with a fairly steady 11-year period. Solar scientists dub each 11 years a “solar cycle.” The first peaked in 1760. Since then, 24 cycles have come and gone. Solar cycle 25 began in June 2019.
17. The Maunder minimum is a 70-year period, from 1645 to 1715, when sunspots all but disappeared during a diminished period of solar activity.
18. One of the best-known of all astronomical facts is that the Sun lies an average of 93 million miles from Earth. Astronomers call this average distance an astronomical unit. In 2012, the International Astronomical Union defined the length of the astronomical unit as 92,955,807.3 miles (149,597,870.7 kilometers). But Earth’s orbit isn’t a perfect circle. We’re closest to the Sun around January 4 each year and farthest from it around the Fourth of July, with the difference of the two extremes being about 3 million miles (5 million kilometers).
19. The Sun (and the rest of the solar system) lie 27,200 light-years from the center of our galaxy, the Milky Way. It takes our solar system between 225 million and 250 million years to complete just one orbit within the Milky Way. And that’s traveling at the incredible speed of 135 miles per second (217 kilometers per second). Speaking of the Milky Way, it contains a total of between 250 billion and 400 billion stars.
20. The Sun is almost a perfect sphere. Its polar diameter is only 6 miles (9.7 kilometers) less than its equatorial diameter.
