Stars vs. Planets: What's the Difference?


Key Difference

Stars are the celestial objects which emit light and heat and contained hot gases and flames. Stars are fixed in their position. Planets are objects which revolve around the stars in particular elliptical path and don’t emit light.


Comparison Chart

DefinitionStars are the astronomical objects, produced due to thermonuclear fusion occurring at its center and emit light.Planets are celestial objects which revolve around stars in their fixed path or orbit.
NumberMillions in numberEight
SizeBig in sizeSmall
LightThey have their own lightThey do not have light
PositionStars remain fixedPlanets change position
ShapeDot shapedSpherical
CompositionHydrogen, helium and other light elements.Solid, liquid and gases or combination

What are Stars?

Stars are glowing balls, containing plasmas, gases and other light elements, held together by its gravity. Plasmas are intensely heated state of matter. Hydrogen and helium are gases which are present in stars. Hydrogen and helium create nuclear fusion in the core of stars which gives shine to the stars. The nuclear fusion occurring in the stars continuously emit energy in the form of light in the universe which helps us to see stars and observe through a radio telescope. Twinkling is the most important characteristic of stars. Light of the stars passes through the earth and enters the earth atmosphere, as the result of atmospheric refraction, they seem to twinkle. The nearest star to the earth is the sun which is almost 150 million km away from earth. Light of sun makes other stars visible during day light. Many stars are visible to the naked eye of humans from the earth. They seem as a multitude of fixed luminous points in the sky due to long distance from the earth. The distance of stars is written in light years, for example, the distance traveled by light per year. It appears moving from east to west. Some stars are 1 billion to 10 billion years old while some stars are even close to 13.8 billion years old. Stars usually composed of 71 hydrogen, 27% helium and a small amount of heavier elements. Iron is the most common element of heavy elements.


What are Planets?

Researchers who research on stars and planets are called astronomers. The planet is an ancient term which relates to history, science, mythology, and religion. People of early cultures consider planets as divine or emissaries of deities. But with the advancement of scientific knowledge, the human perception changed about the planets Planet refers to a heavy object that revolves around a star in a fixed path which is called orbit. It is large enough to gain shape of a sphere by its gravity, but the planet is not large to effect nuclear reaction. Planets also explain other bodies of its neighboring area. Until now, astronomers have discovered eight planets namely Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Planets are classified into two main types; large (low density giant) and small (terrestrial). Planets of the solar system are divided into two parts by orbit; inner planets and outer planets. Planets whose path rests inside the asteroid belt are known as inner planets. Inner planets are usually small and contain solid elements like rocks and metals. Mercury, Venus, Earth, and Mars are examples of inner planets. Pluto has also solid rocky surface but never grouped with these four inner planets. On the other hand, the orbit of outer planets lies external to the asteroid belt. Their size is larger than inner planets and carries a ring around them. They are composed of gases like hydrogen, helium, etc. Jupiter, Saturn, Uranus, and Neptune are examples of outer planets. Outer planets also called Jovian planets (Jupiter like). According to NASA, Jupiter and Saturn are called as a gas giant because both are dominated by gases while other two are known as ice giant because of the presence of ice. Mercury is the closest planet to the sun and Neptune is the eighth planet from the sun.


Stars vs. Planets

  • Stars develop when a cloud of gas, out in nebula or any other region of interstellar space collapses under the effect of gravity.
  • Planets form when the material in the disk around a preexisting star begins to condense around rock cores.
  • Stars twinkle in the sky.
  • Planets do not twinkle in the sky.
  • Stars have their light.
  • Planets do not have their light.
  • Stars are fixed on a point.
  • Planets are not fixed. They revolve around the sun.
  • Stars are big in size.
  • Planets are small in size in comparison to the sun.

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