Solar Spectra: a Lesson on the Sun: Mrs. Pape’s Solar Lesson Bernalillo Middle School Bernalillo, NM © Contact Information: School Phone: (505)

~Background on~ THE SUN:

THE SUN: How big is the sun? 1,392,000 kilometers in diameter – that is 109 Earth diameters! All the planets orbit the sun because of its large mass and gravity. How far away is the sun? 93 million miles from Earth!

The Sun and its parts: The CORE: 10% of the sun’s mass, this is where nuclear fusion takes place –Nuclear fusion requires very high temperatures and high densities! The core of the sun has a temperature of 16 million degrees K (kelvin) and a density 160 times greater than water. This is very high since iron metal on Earth only has a density 7 times greater than water! But the core of the sun is all gas!!!

The Sun and its parts: The RADIATIVE ZONE: this layer inside the sun is 85% of the Sun’s radius, this is where the superhot energy from the sun’s core is transferred to the outer layers of the sun by Photons. –It could take a photon in the sun’s core a million years before it finally reaches the sun’s surface. Due to the high temperatures and the many gases in the sun the Photon will ‘bump’ into many other atoms and gas particles before it reaches the surface. Each time a photon ‘bumps’ into a gas particle it releases some energy. –Because the photons now reaching the sun’s surface were produced about a million years ago, they tell us about the conditions in the core as it was a million years ago.

The Sun and its parts: The CONVECTIVE ZONE: Makes up 15 % of the Sun’s radius, it is just below the sun’s surface. –Motions of gas called convection currents (rising by heat and sinking by cooling) are involved in this layer to again transfer the hot energy inside the sun, outward to the sun’s surface, the photosphere, our next layer!

Convection Currents deep in the Sun

REVIEW - The Inner Sun:

The Sun’s Surface: PHOTOSPHERE: This is the deepest layer of the sun that you can see. Photosphere means “light sphere” because it is the portion of the sun that is visible with white light (our visual spectrum). –It is called the “surface” of the sun because this is the layer where Photons can finally escape to outer space. –The Photosphere layer is cooler than the layers below it and cooler than the atmosphere layers above it. The cause for this is unknown, but there are many different theories.

Solar Surface - Photosphere Photo at High Resolution Each small ‘bead’ area is called a granule. One granule is about the size of the state of Texas! The entire process is called granulation. The bright areas are hotter, where the material is rising. The darker/black areas are cooler areas where the material is sinking.

The Sun’s Atmosphere: CHROMOSPHERE: Meaning “color sphere” because it is actually a bright pink color. It is only about 2000 to 3000 kilometers think. It’s temperature rises moving outward away from the Photosphere. –More studies are being conducted on the Chromosphere to determine flux in temperature and release of ionized gases at different heights.

CHROMOSPHERE:

The Outer Most Layer of the Sun: CORONA: The outer most layer of the solar atmosphere. Due to the sun being so bright the Corona can only be seen during a solar eclipse or by blocking out the solar disk with an instrument on a telescope. –The Corona is very hot! About 10 million degrees F. But even though the Corona has high temperatures it does not give off a lot of heat – due to its low density and scattered ionized gasses.

CORONA:

REVIEW – Solar Atmosphere: