• Question: does the sun have a mantle?

    Asked by sina to Austin, Kirsty, Nike on 21 Jun 2012.
    • Photo: Nike Dattani

      Nike Dattani answered on 21 Jun 2012:

      No it does not =)

      The word “mantle” is only used for planets, because it’s a rocky layer between the core of the planet and the surface of the planet. The sun is too hot to have rocks !

    • Photo: Kirsty Ross

      Kirsty Ross answered on 22 Jun 2012:

      Hello Sina

      As Nike says, stars like our sun do not have mantles. They have a very different structure to the planets which is equally as interesting. The innermost layer of the sun is the core. With a density of 160 g/cm^3, 10 times that of lead, the core might be expected to be solid. However, the core’s temperature of 15 million kelvins (27 million degrees Fahrenheit) keeps it in a gaseous state.

      Outside of the core is the radiative envelope, which is surrounded by the convective envelope. The temperature is 4 million kelvins (7 million degrees F). The density of the solar envelope is much less than that of the core. The core contains 40 percent of the sun’s mass in 10 percent of the volume, while the solar envelope has 60 percent of the mass in 90 percent of the volume. The solar envelope puts pressure on the core and maintains the core’s temperature.

      The photosphere is the zone from which the sunlight we see is emitted. The photosphere is a comparatively thin layer of low pressure gasses surrounding the envelope. It is only a few hundred kilometers thick, with a temperature of 6000 K. The composition, temperature, and pressure of the photosphere are revealed by the spectrum of sunlight. In fact, helium was discovered in 1896 by William Ramsey, when in analyzing the solar spectrum he found features that did not belong to any gas known on earth. The newly-discovered gas was named helium in honor of Helios, the mythological Greek god of the sun.

      In an eclipse, a red circle around the outside of the sun can sometimes can be seen. This is the chromosphere. Its red coloring is caused by the abundance of hydrogen. From the centre of the sun to the chromosphere, the temperature decreases proportionally as the distance from the core increases. The chromosphere’s temperature, however, is 7000 K, hotter than that of the photosphere. Temperatures continue to increase through the corona.