7.6: Accessible Descriptions

Figure 7.2.1 Fusion and Fission

Two simplified diagrams comparing nuclear fusion and nuclear fission.

Diagram (a): Fusion

• One white sphere and one green sphere move toward each other and join together into a single larger sphere.

Diagram (b): Fission

• A large ball made up of many smaller white and green spheres breaks apart into two smaller balls, each containing a mix of white and green spheres.

Figure 7.2.2 Proton-Proton Chain, Step 1

A diagram of the first step in the proton-proton chain, in which two protons fuse to form deuterium.

Diagram Elements

• Two protons, drawn in blue and labeled 1H, are shown at the left.
• An arrow from each proton points toward the right and meets at an illustration of a small explosion, representing the release of energy and mass in the collision.
• Three arrows lead away from the explosion toward the right.
• The topmost arrow points to a neutrino, drawn in light blue and labeled Neutrino.
• The center arrow points to a deuterium nucleus, drawn as a blue dot (proton) and a red dot (neutron) and labeled 2H.
• The lower arrow points to a positron, drawn in purple and labeled Positron.

Figure 7.2.3 Proton-Proton Chain, Step 2

A diagram of the second step in the proton-proton chain, in which deuterium fuses with a proton to form helium-3.

Diagram Elements

• At upper left is the deuterium nucleus from step 1, drawn as a blue dot (proton) and a red dot (neutron) and labeled 2H.
• At lower left is a proton, drawn in blue and labeled 1H.
• An arrow from each object points toward the right and meets at an illustration of a small explosion, representing the release of energy and mass in the collision.
• A single arrow leads away from the explosion toward the right, pointing to a helium-3 nucleus, drawn as two blue dots (protons) and one red dot (neutron) and labeled 3He.
• A wavy arrow moves away from the helium-3 nucleus, labeled Gamma ray.

Figure 7.2.4 Proton-Proton Chain, Step 3

A diagram of the third step in the proton-proton chain, in which two helium-3 nuclei combine to form helium-4.

Diagram Elements

• At left are two helium-3 nuclei, each drawn as two blue dots (protons) and one red dot (neutron) and labeled 3He.
• An arrow from each nucleus points toward the right and meets at an illustration of a small explosion, representing the release of energy and mass in the collision.
• Three arrows lead away from the explosion toward the right.
• The topmost arrow points to a proton, drawn in blue and labeled 1H.
• The center arrow points to a helium-4 nucleus, drawn as two blue dots (protons) and two red dots (neutrons) and labeled 4He.
• The lower arrow points to a second proton, drawn in blue and labeled 1H.

Figure 7.3.1 Gas Pressure

A diagram of gas molecules moving inside an imaginary container, illustrating the origin of gas pressure.

Diagram Elements

• An imaginary container is drawn as a light blue cube.
• Several dots inside the cube represent gas molecules, each trailing a line that narrows toward the point the molecule just traveled from, showing its path.
• Many of the dots have bounced off the sides of the cube; others are still traveling in straight lines.

Figure 7.3.2 Hydrostatic Equilibrium

A cutaway diagram of a star showing the balance of forces at a point within it.

Diagram Elements

• A cutaway view of a star shows an imaginary point, marked with a red dot, about halfway between the center and the surface.
• Two equal-length arrows extend from the red dot in opposite directions.
• One arrow points toward the center of the star and is labeled Gravity.
• The other arrow points toward the surface of the star and is labeled Pressure.
• The equal lengths of the arrows show that the two forces are balanced.

Figure 7.3.3 Convection

A diagram of convection cells carrying heat upward through the Sun's convection zone.

Diagram Elements

• The solar interior is labeled and drawn as an orange semicircle at the bottom of the image.
• Above it, in contact with the solar interior, is the convection zone, labeled and drawn in yellow.
• Seven ovals within the convection zone represent individual convection cells.
• Each oval has two arrows on its perimeter: one pointing downward toward the solar interior, and one on the opposite side pointing upward toward the surface, showing the rising and sinking motion of hot gas within each cell.

Figure 7.3.4 Photons Deep in the Sun

A diagram tracing the zigzagging path of a single photon as it scatters through the dense gas of the solar interior.

Diagram Elements

• The dense gas of the solar interior is shown as a fairly uniform scattering of yellow dots.
• A photon, drawn as a wavy black arrow, moves upward from the bottom of the figure and strikes a yellow dot.
• From that point, a second wavy arrow moves toward the upper left to another dot.
• A third arrow moves from there toward the upper right to another dot.
• A fourth arrow moves toward the lower right to another dot.
• A fifth arrow moves horizontally to the right to another dot.
• A sixth and final arrow moves toward the upper left to a last dot, completing six random changes of direction.

Figure 7.3.5 Photon and Neutrino Paths

Two diagrams of the Sun comparing the paths taken by a photon and a neutrino from the core to space.

Diagram (a): Photon Path

• On the left
• The Sun is drawn as a yellow disk.
• Starting at the center, the photon's path is drawn in red and labeled Photon.
• The path zigzags, curves, and twists back on itself many times before reaching the Sun's surface, then continues away into space in a straight line.

Diagram (b): Neutrino Path

• On the right
• The Sun is again drawn as a yellow disk.
• Starting at the center, the neutrino's path is drawn in blue and labeled Neutrino.
• The path is a straight line from the center to the surface and onward into space.

Figure 7.3.6 Solar Interior

A cutaway illustration of the Sun showing its interior layers and two surface features.

Diagram Elements

• A triangular wedge has been removed from the upper half of the Sun to expose the interior, while surface features are shown in the lower half.
• Interior features are labeled on the left side of the figure.
• The core is labeled and drawn in blue at the center.
• The radiative zone surrounds the core, drawn as a gradient from yellow near the core to orange and finally red at its outer boundary.
• Several wavy arrows extend from the center of the core out to the red boundary of the radiative zone, representing energy leaving the core and moving outward through the radiative zone.
• The convection zone is drawn as a thick yellow layer above the radiative zone, with oval arrows showing the vertical rising and sinking motion of the gas.
• Two surface features are labeled on the right side of the figure: granulation and a sunspot.

Credit: NASA/Goddard

Figure 7.3.7 Solar Interior Temperature

Four graphs showing how temperature, density, luminosity fraction, and hydrogen abundance vary from the Sun's center to its surface.

Shared Horizontal Axis

• All four graphs share a horizontal axis labeled Fraction of the Sun's radius, running from zero at the center on the left to 1.0 at the surface on the right.
• Three regions are labeled across the top of each graph: the Nuclear fusion zone, shaded aqua, from 0 to 0.3; the Radiative zone, shaded orange, from 0.3 to 0.7; and the Convection zone, shaded yellow, from 0.7 to 1.0.

Upper Left: Temperature

• The vertical axis is labeled Temperature (K) and ranges from 0 to 15 x 10⁶ in increments of 5 x 10⁶.
• The plotted line begins at 15 x 10⁶ K at the center and slopes steadily downward to near zero at the surface.

Lower Left: Density

• The vertical axis is labeled Density (g/cm³) and ranges from zero to 150 in increments of 50.
• The plotted line begins near 160 g/cm³ at the center and drops off sharply to near zero by about 0.6 of the Sun's radius.

Upper Right: Fraction of Luminosity

• The vertical axis is labeled Fraction of Luminosity and ranges from zero to 1 in increments of 0.25.
• The plotted line begins at zero at the center, rises sharply to 1 by about 0.25 of the Sun's radius, and then stays constant at 1 through the rest of the interior.

Lower Right: Hydrogen Abundance

• The vertical axis is labeled Percentage of Hydrogen (by weight) and ranges from zero to 1.0 in increments of 0.25.
• The plotted line begins near 0.3 at the center, rises quickly to about 0.75 by 0.2 of the Sun's radius, and then stays constant at 0.75 through the rest of the interior.

Figure 7.3.8 Solar Oscillations

A computer simulation showing alternating regions of inward and outward motion across the Sun.

Diagram Elements

• A triangular wedge is removed from the upper half of the spherical Sun to expose the interior, with surface features shown in the lower half.
• Alternating red and blue regions extend radially outward from the center of the sphere to the surface, with red marking inward motion and blue marking outward motion.

Credit: GONG, NOAO

Figure 7.3.9 Sunspot Structure

An image of the Sun with a diagram showing the flow of gas beneath a sunspot.

Image (a)

• On the left
• A visible-light image of the Sun with a box drawn around a large sunspot complex below center.
• An arrow leads from the box to the diagram on the right.

Diagram (b)

• On the right
• A profile view of the region beneath the sunspot, boxed in Image (a).
• The cooler gas of the sunspot is shown in blue at the top.
• A plume of hot gas, shown in red, rises and expands upward toward the sunspot.
• Black arrows show the direction of material flow: pointing downward through the blue sunspot, showing the cooler gas sinking, and pointing upward within the red plume.
• Where the downward and upward arrows meet, they turn outward toward the left and right edges of the figure, showing that the rising plume is blocked by the sinking sunspot material and diverted sideways.

Credit: NASA, SDO

Figure 7.3.10 Sudbury Neutrino Detector

A photograph of the Sudbury Neutrino Detector's 12-meter diameter sphere.

Image Elements

• The 12-meter diameter sphere is covered with an interconnected lattice of triangular support structures.
• A dense matrix of photodetectors covers the surface of the sphere, used to detect flashes of light from neutrino interactions.

Credit: A.B. McDonald (Queen's University) et al., The Sudbury Neutrino Observatory Institute

Figure 7.4.1 SNO+ Detector

A photograph of the SNO+ neutrino detector during a stage of construction.

Image Elements

• The 12-meter acrylic vessel of the detector is shown supported by an interconnected triangular framework.
• The vessel was partially filled with liquid scintillator while the surrounding water was still being replaced, visible as a layered fluid inside the transparent sphere.

Figure 7.4.2 Standard Model of Particle Physics

A table of the fundamental particles of the Standard Model of particle physics.

Table Elements

• Twelve fermions, the matter particles, are arranged in a grid of three generations: six quarks (up, down, charm, strange, top, and bottom) and six leptons (electron, muon, tau, and their three corresponding neutrinos).
• The three neutrino flavors, electron neutrino, muon neutrino, and tau neutrino, are shown along the bottom row of the lepton columns.
• Additional columns show the gauge bosons, the force-carrier particles (photon, gluon, Z boson, and W boson), and the Higgs boson.
• Each particle's box lists its mass, charge, and spin.