Sun
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The Sun is the star at the center of the Solar System. It is a massive, hot ball of plasma, inflated and heated by energy produced by nuclear fusion reactions at its core. Part of this energy is emitted from its surface as visible light, ultraviolet, and infrared radiation, providing most of the energy for life on Earth. The Sun has been an object of veneration in many cultures. It has been a central subject for astronomical research since antiquity.
The Sun, filmed through a clear solar filter
High-resolution image of the Sun's surface taken by the Daniel K. Inouye Solar Telescope (DKIST)
The Sun's transition region taken by Hinode's Solar Optical Telescope
During a solar eclipse the solar corona can be seen with the naked eye during totality.
Star
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A star is a luminous spheroid of plasma held together by self-gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night; their immense distances from Earth make them appear as fixed points of light. The most prominent stars have been categorised into constellations and asterisms, and many of the brightest stars have proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. The observable universe contains an estimated 1022 to 1024 stars. Only about 4,000 of these stars are visible to the naked eye—all within the Milky Way galaxy.
Image of the Sun, a G-type main-sequence star, the closest to Earth
A star-forming region in the Large Magellanic Cloud
Stars in the night sky
Infrared image from NASA's Spitzer Space Telescope showing hundreds of thousands of stars in the Milky Way galaxy