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Sun factsheet

Our Sun is actually the closest star to Earth. The Sun is a massive shining sphere of hot gas. It is by far the largest object in the solar system, and contains more than 99.8% of the total mass of the Solar System (Jupiter contains most of the rest). Its strong gravitational pull holds Earth and the other planets in the solar system in orbit. We rely on the Sun’s light and heat.

Our Sun is considered to be an average star, meaning its size, age, and temperature fall in about the middle of the ranges of these properties for all stars. While some stars in our galaxy are nearly as old as the universe, about 15 billion years, our sun is a second-generation star. It is only 4.6 billion years old. Some of its material came from former stars.

Sun Data

  • Mass 1024 kg
  • GM x 106 km3/s2
  • Volume 1012 km3
  • Volumetric mean radius (km): 696,000.
  • Mean density (kg/m3): 1408.
  • Surface gravity (eq.) (m/s2): 274.0
  • Escape velocity (km/s): 617.7
  • Ellipticity: 0.00005
  • Moment of inertia (I/MR2): 0.059
  • Visual magnitude V(1,0):26.74
  • Absolute magnitude: +4.83
  • Luminosity (1024 J/s): 384.6
  • Mass conversion rate (106 kg/s): 4300.
  • Mean energy production (10-3 J/kg): 0.1937
  • Surface emission (106 J/m2s): 63.29
  • Spectral type: G2 V

Since its creation, the sun has used up about half of the hydrogen in its core. Over the next 5 billion years or so, it will grow steadily brighter as more helium accumulates in its core. As the supply of hydrogen dwindles, the Sun's core must keep producing enough pressure to keep the Sun from collapsing in on itself. The only way it can do this is to increase its temperature. Eventually the sun will run out of hydrogen fuel. At that point, it will go through a radical change which will most likely result in the complete destruction of the planet Earth.

The Greeks named the sun Helios, but the Romans used the name Sol, which is still in use today. Because of the important role the sun plays in our lives, it has been studied, perhaps, more than any other object in the universe, outside our own planet Earth.