1. Mercury
   Sun
2. Earth
   Mars

The Sun keeps the solar system orderly, as it prevents the planets from aligning. Mercury, the closest planet to the Sun, sustains temperatures as high as 840 degrees Fahrenheit.

1. Metabolism
   Photosynthesis
2. Respiration
   Excretion

Plants and other organisms convert the light's energy into chemical energy, which the organism uses as fuel. The sun's energy is stored in food as well as fossil fuels.

1. Messier 81
   Milky Way
2. Black Eye
   Virgo Stellar Stream

The Milky Way contains billions of stars, and the Sun is just one of those stars. The Sun is the closest star to Earth. Scientists estimate that the Sun is brighter than approximately 85 percent of the stars in the galaxy.

1. Gold and silver
   Light and heat
2. Hydrogen and oxygen
   Carbon and nitrogen

Aside from the important weather patterns and photosynthesis that the Sun's light and heat make possible, sunlight and electromagnetic radiation are responsible for how humans are able to perceive themselves, the world and the universe. You might not appreciate the heat on an August day, though!

1. Metal
   Gas
2. Liquid
   Plasma

The Sun is a large gas ball made mostly of hydrogen and helium. The Sun's surface, or photosphere, gives off constant radiation and it consists of very dense gas, making it extremely hard for us to see through it.

1. By prominence
   By granules
2. By flares
   By radiation

The photosphere surface layer of the Sun is 300 miles thick. The photosphere produces solar flares, or bursts of fire, that generate flashes of radio waves, X-rays, ultraviolet radiation and electromagnetic radiation.

1. Photon
   Proton
2. Electron
   Neutron

Photon particles result from the nuclear fusion reaction that occurs when hydrogen protons merge to produce helium nuclei. A photon bundle of electromagnetic radiation is a ray of light. Photons have no mass.

1. Helios
   Elio
2. Sol
   Samson

The naming of the days of the week after planetary bodies dates back to the Roman era. Sunday was reserved for the sun god. There were various manifestations of sun worship and sun cults during the Roman Empire.

1. 20 minutes
   8 seconds
2. 8 minutes
   1 nanosecond

Energy passes up through the Sun's surface, or photosphere, as visible sunlight, which is produced as electrons react with hydrogen atoms to produce hydrogen ions. The upper portion of the photosphere is cooler than that bottom part, making the Sun appear brighter at the center than the edges.

1. 7,000 miles
   96,650 miles
2. 100 miles
   865,000 miles

Our Sun's circumference is approximately 2,713,406 miles. Comparatively, the supergiant star Betelgeuse is 700 times bigger than the Sun.

1. 17 billion
   30 million
2. 4.5 billion
   6 million

The Sun was formed as a result of the collapse of a molecular mass made mostly of hydrogen and helium, which then produced the Sun and other stars in the solar system. The residual clump that produced the Sun slowly concentrated and heated up due to gravitational forces.

1. 9
   20
2. 5
   99.8

The Sun's core is quite dense and accounts for nearly 60 percent of the Sun's mass. The German mathematician Johannes Kepler devised a way to calculate the Sun's mass by means of a planetary constant from his third law.

1. 5 - 10 billion years from now
   6 - 12 million years from now
2. 80 billion years from now
   32 million years from now

Scientists are able to estimate the period of time that the Sun has left to function based on the amount of hydrogen it is estimated to have. Based on computer analysis, there is enough hydrogen in the Sun to enable energy production for another 5 to 10 billion years at the current rate of nuclear fusion.

1. Granule
   Prominence
2. Asterism
   Comet

A prominence is a large burst of incandescent gas that projects above the Sun's chromosphere into the solar corona, but is fastened to the photosphere. Prominences take about a day to form, and they can persist for months, spanning great distances into space.

1. 700 billion tons
   6 million tons
2. 18 billion tons
   6 million tons

The Sun produces energy from the net change in mass that results from the merging of hydrogen protons into helium nuclei. This nuclear fusion process has been called a proton-proton process. Gamma radiation is emitted as a result.

1. 8,500 kelvins
   500 kelvins
2. 5,800 kelvins
   800 kelvins

Gas currents that the Sun's convective zone sends to the photosphere layer release energy there before getting sent back to the center of the Sun to be reheated. The Earth's core is hotter than the surface, and the temperature drops to 4,000 kelvins just beyond the photosphere.

1. Z2
   F3
2. G2
   A1

The Sun is the central G2 V star of the solar system. "G2" indicates that it is the second hottest of the yellow G spectrum class stars. "V" indicates that the Sun is a main-sequence dwarf star, which is the standard star of its temperature class.

1. Prominence
   Granulation
2. Sunspots
   Flares

The grainy pattern atop the Sun's surface, or photosphere, is produced by convective cells and are a result of a violent movement of gas beneath the surface. The granular pattern consists of hexagonal prism shapes.

1. Sunspots
   Granules
2. Prominence
   Pigmentation

Sunspots are dark in color because they are cooler than their surroundings. These regions carry powerful magnetic fields where less heat escapes the photosphere.

1. Core
   Corona
2. Radiative zone
   Sunspots

A solar eclipse occurs when the Moon's dark contour completely conceals the bright light from the Sun's photosphere. This enables us to see the fainter light of the solar corona.

1. Core
   Photosphere
2. Plasma
   Chromosphere

The Earth and other components of the solar system revolve around the Sun. The Sun's light warms the Earth and is responsible for major terrestrial phenomena, such as global weather activity and plant photosynthesis.

1. 27 million degrees Fahrenheit
   68 million degrees Fahrenheit
2. 100 million degrees Fahrenheit
   6,000 kelvins

Intense gravitational forces produce tremendous pressure and high temperature at the Sun's core. The hydrogen-to-helium conversion that takes place in the core is a process called nuclear fusion and it produces vast amounts of energy.

1. Solar wind
   Granules
2. Protons
   Electrons

Solar wind is comprised mostly of protons and electrons that are heated at high temperatures generated by the solar corona. These particles are accelerated at velocities high enough for them to resist the gravitational field of the Sun and escape.

1. Aurora Superior
   Geomagnetic Storm of 1901
2. The Carrington Event
   Kepler's Phenomenon

Solar storms, or geomagnetic storms, cause a disturbance of the Earth's magnetosphere. The Carrington Event, which happened on Sept. 2, 1859, generated fierce luminous arrays and sparked fires caused by the accelerated flow of electricity along telegraph wires, which ignited recording tape at various telegraph stations.

1. Convective zone
   Radiative zone
2. Corona
   Chromosphere

The Sun's radiative zone, or radiation zone, is the area of the solar interior between the innermost core and the outer convective zone. The radiative zone is 200,000 miles thick.

1. Sol
   Helios
2. Eliana
   Arun

Ancient Greek religion personified the Sun as the male deity Helios. The Greeks depicted their Sun god Helios being hauled in a horse-drawn chariot from east to west across the sky.

1. Copper into nitrogen
   Helium into nitrogen
2. Hydrogen into helium
   Carbon into gold

The hydrogen-to-helium conversion is nuclear fusion that produces highly charged photons that navigate the radiative layer that surrounds the core. It takes one million years for energy to pass through this layer to the convective layer, since the photons are constantly redirected, absorbed and re-released.

1. Core
   Chromosphere
2. Photosphere
   Solar corona

The solar core is located approximately 312,000 miles below the Sun's surface. The core is 20-25 percent of the Sun's radius, and it is 3 percent of the Sun's volume.

1. Core
   Radiative zone
2. Convective zone
   Chromosphere

The chromosphere, or color sphere, is located above the glaring photosphere layer and below the solar corona. The chromosphere and the corona are hotter than the Sun's surface.

1. Prominence
   Solar corona
2. Core
   Photosphere

The corona is the solar atmosphere that surrounds the Sun and other stars. The corona extends millions of miles into space and has a temperature of one to two million kelvins.

1. 4
   1.3 million
2. 10,000 thousand
   30 billion

Although the Sun's volume is 1.3 million times the volume of Earth, the Sun is still considered a average-sized star. The Sun's radius is 109 times that of planet Earth.

1. Clockwise
   Differentially
2. Counterclockwise
   Angularly

The Sun rotates on its axis from east to west based on solar spectrum studies. The equator of the Sun rotates once every 26 days, and its poles rotate once every 36 days. Scientists believe that this differential rotation produces sunspots and causes magnetic fields to warp.

1. 60 - 90 days
   12 - 15 days
2. 26 - 36 days
   30 - 45 days

At high altitudes, sunspots at the equator rotate at a rate of 28 days. The Sun's surface rotation is faster at the Sun's equator and slower at its poles. This phenomenon is prompted by the convective zone.

1. Convective zone
   Radiative zone
2. Photosphere
   Solar corona

The photosphere is solar atmosphere's innermost layer where the most light is released. The photosphere is 250 miles wide, and the temperatures in this layer range from 7,460 degrees F at the top part to 17,500 F at the bottom.

1. Termination
   Nuclear fusion
2. Photosynthesis
   Hydroplaning

The Sun produces electromagnetic energy in its core through the process of nuclear fusion. Every second, 700 billion tons of hydrogen protons are used up. However, only a small percent of the resultant energy becomes light energy.