1. The Sun is just one of about 200-400 billion stars in our Galaxy

The Milky Way is estimated to contain 200–400 billion stars, although this number may be as high as one trillion. Although, counting the stars in the galaxy is inherently difficult because, well, we can’t see all of them. Astronomers look at a small sample of the Milky Way and figure out how many stars it has and how much they each weigh. They then figure out how much the whole galaxy weighs, and they estimate the total number of stars from there.

2. The Sun accounts for 99.86% of the mass in the solar system

The Sun is the largest object in the solar system with a diameter of about 109 times that of Earth and a mass about 330,000 times or (1.98855±0.00025)×1030 k larger. If the sun were a hollow ball, more than a million Earths could stuff inside it.

  • Equatorial Radius: 695,500 km
  • Equatorial Circumference: 4,379,000 km
  • Volume: 1,142,200,000,000,000,000 km3
  • Mass: 1,989,000,000,000,000,000,000,000,000,000 kg
  • Density: 1.409 g/cm3
  • Surface Area: 6,087,799,000,000 km2

3. The Sun is middle-aged

The Sun is roughly middle-aged and will remain fairly stable for another four billion years. However, after hydrogen fusion in its core has stopped, the Sun will undergo severe changes and become a red giant. It is calculated that the Sun will become sufficiently large to engulf the current orbits of Mercury, Venus, and possibly Earth.

4. The Sun has many different layers

Much like the earth, the Sun has many different layers that define its structure. Unlike the earth, the Sun is completely gaseous, there is no solid surface on the Sun.

 5. The Sun has a 6 step life cycle

  1. Gas cloud: Initially the gas and dust which go to make up stars is in the form of a large dense cloud. The cloud starts to fragment and collapse under it’s own gravity and forms a proto-star.
  2. Proto-star: As the center heats up (gravitational energy is being converted into heat), the proto-star gets hot enough to glow red and continues to condense until nuclear reactions in its core halt the gravitational collapse.
  3. Main sequence: The star is stable, burning Hydrogen gas to Helium in its core through nuclear fusion. Stars spend about 90% of their active lifetime as main sequence stars. This is the stage our Sun is in now.
  4. Red giant: As the star runs out of core fuel to “burn” the stability of the star is disrupted and the core begins to shrink. The star then starts to turn Helium into Carbon. The rapid burning of helium causes the outer layers of the star to puff out, cooling the star and causing it to glow red. It is now a red giant. The Sun will spend approximately 250 million years as a red giant.
  5. Planetary nebula: The outer layers of the star are ejected as core continues to shrink. For stars like the Sun this process produces what is known as a planetary nebula.
  6. Remnant: The low mass core continues shrinking to form a star known as a white dwarf surrounded by the planetary nebula.

6. Conditions at the Sun’s core are extreme

The temperature of the Sun’s core is 15.6 million Kelvin and the pressure is 250 billion atmospheres. At the center of the core the Sun’s density is more than 150 times that of water.

7. The Sun is heating up and it’s bad news for Earth

The Sun is slowly heating up becoming 10% more luminous every billion years. Within just a billion years, the heat from the Sun will be so intense that liquid water will evaporate from Earth. Life as we know it will be gone forever. The surface of the planet will be scorched and uninhabited. It’ll take another 7 billion years for the Sun to reach its red giant phase before it actually expands to the point that it engulfs the Earth and destroys the entire planet.

8. The Sun blows Solar Wind

In addition to light, the sun radiates heat and a steady stream of charged particles known as the solar wind. The wind blows about 280 miles (450 kilometers) a second throughout the solar system.

9. Different part of the sun rotate at different rates

Since the sun is not a solid body, different parts of the sun rotate at different rates. At the equator, the sun spins once about every 25 days, but at its poles the sun rotates once on its axis every 36 Earth days.

10. The Sun is always changing

No matter when or where we look at the sun, we will always see something different and interesting. Scientists observe these changes by watching the sunspots. They increase and decrease on a regular cycle of about 10.8 years.