- The Sun is a large ball of hot ionized gas that shines on its own.
- It is 109 times wider than the Earth and can hold 1.3 million Earths.
- The Sun does not have a solid surface or core.
- It is mostly made of hydrogen and helium (98%) and is so hot that matter can’t survive as a liquid or solid.
- The Sun is an electrically charged environment because its atoms are ionized due to its extremely high temperatures. Such a hot ionized gas is called a plasma.
- The Sun rotates in a counter-clockwise direction.
- Closer objects to the Sun are made of elements with high melting points and farther objects are made of lower melting point elements.
- The Sun is a rare type of star in the Milky Way.
Characteristics of the Sun:
- Age: 4.6 billion years.
- Diameter: 1.39 million km.
- Temperature: 6000 °C on surface and 16 million °C in core.
- Density: 1.41 times that of water.
- Gasses spin at different rates, therefore, while the sun does indeed rotate on its axis, different parts of the sun rotate at different speeds. It does not rotate at a constant rate like solid Earth.
- The differential rotation of the sun helps contribute to sunspots, magnetic fields, and radiation.
Sun’s Internal Structure and Atmosphere:
- The Sun’s energy is produced by different layers of the Sun.
- The layers from inside out are the core, radiative zone, and convective zone.
- The core is the hottest part of the Sun and releases nuclear energy.
- The radiative zone starts at 25% of the distance to the surface and extends to 70% and is the primary mode for energy transport.
- The convective zone is the outermost layer and transports energy to the surface through convection cells.
- The convective zone is 200,000 kilometers deep and energy is transported by hot plasma that rises to the surface, cools, and sinks back.
- Photosphere:
- The photosphere is the lowest layer of the solar atmosphere and the visible surface of the Sun.
- It is the bright outer layer that emits most of the radiation.
- The photosphere has an uneven surface.
- The temperature on the outer side of the photosphere is 6000°C.
- Chromosphere:
- The chromosphere is the second layer in the Sun’s atmosphere and is 3,000 to 5,000 kilometers deep.
- It appears rosy red during eclipses.
- The chromosphere is located above the photosphere and below the solar transition region.
- It is a thin layer of burning gases.
- The temperature of the chromosphere is about 10,000 K.
- Transition Region:
- Here the temperature rises rapidly from 10,000 K (typical of the chromosphere) to nearly a million degrees.
- This hottest part of the solar atmosphere is called the corona.
- The transition region is a few tens of kilometers thick and is located between the chromosphere and the corona.
- Corona:
- It is the outermost part of the Sun’s atmosphere.
- It was first observed during total eclipses.
- The corona extends millions of kilometers into space and is most easily visible during a total solar eclipse.
Coronal Holes
- A coronal hole is a region of less dense, cool plasma in the solar corona.
- The magnetic field in a coronal hole is open, allowing solar wind to escape at a faster rate.
- Resulting in decreased temperature, density and increased speed of solar wind in interplanetary space.
- Coronal holes appear darker than their surroundings and can last from a few weeks to months.
- They occur throughout the sun’s 11-year cycle and last longer during solar minimum.
- Coronal holes are important for understanding the space environment around Earth and its impact on technology and astronauts.
