Solar Surface Sun Facts The Sun is a

Solar Surface

Sun Facts • The Sun is a gas cloud of mostly hydrogen and helium. • The age is about 5 billion years. v Diameter: about 100 times Earth’s v Volume: about 1, 000 times Earth’s v Mass : about 300, 000 times Earth’s v Density = mass/volume = 1. 4 g/cm 3 v water is 1. 0 g/cm 3, Earth is 5. 6 g/cm 3

Luminous Gas • We only see the surface of the sun. – Not a solid surface – Temperature 5, 800 K = 10, 000 °F – Hot enough for visible light • Gases extend upward for thousands of km.

Solar Atmosphere • The Sun’s atmosphere is divided into three layers. – Different temperatures and densities chromosphere corona photosphere Sun’s interior

Eye on the Sun • The Solar Dynamics Observatory is in orbit around the Earth. – Launched Feb 2010

Photosphere • The visible surface is the photosphere. – Brightest part of the sun • The photosphere has features that show convection. Granules: Dark areas are cool and are sinking. Light areas are hot and are rising. Supergranules: Doppler color shows rising and sinking.

Chromosphere • The chromosphere is immediately above the photosphere. – Temperature to 20, 000 K – Faint compared to photoshpere – Red from hydrogen gas • The chromosphere is the site of prominences of hydrogen gas.

Corona • • The outermost layer of the sun is the corona. It can be seen during total eclipses - bright as a full Moon. The gas is thin but heated to over 1, 000 K. The Parker Solar Probe will fly through the corona.

Solar Wind • This solar wind streams away from the sun at high speed (300 to 800 km/s). • The solar wind distorts planetary magnetic fields. – Measured beyond Neptune