Q:

What is the difference between a planet and a star?

A:

Quick Answer

Planets and stars differ in their mass, composition and life cycle. Stars are usually structurally simple bodies of high mass that produce energy by way of nuclear fusion of hydrogen into helium. Planets are much smaller, do not generate light and usually orbit stars.

Know More
What is the difference between a planet and a star?
Credit: Steve Allen Stone Getty Images

Full Answer

Solar systems form when clouds of gas and dust coalesce into protostellar accretion disks. Most of the mass in such a disk falls toward the center, which provides the mass and energy required to drive the nuclear fusion engine that powers a star throughout its life. Outside the star, small eddies in the accretion disk collapse locally to form small bodies. These small objects grow in size as they collide with one another over millions of years. The largest of these bodies become planets.

Unlike stars, planets can be gaseous or rocky. Some worlds, such as the dwarf planet Pluto, incorporate ice as a major component of their makeup. At the lower size range, dwarf planets can resemble comets, which are formed in ways similar to planets. The largest possible planet would have a mass 75 times that of Jupiter. Above that threshold, the world's mass is sufficient to sustain fusion, and it is, by definition, considered a brown dwarf star.

Learn more about Planets

Related Questions

  • Q:

    When was Uranus discovered?

    A:

    The planet Uranus was discovered on March 13, 1781, by British astronomer William Herschel. While Uranus is visible from Earth with the naked eye under optimal conditions, it was long assumed to be a star due to its dimness and slow orbit.

    Full Answer >
    Filed Under:
  • Q:

    Which planet has the weakest gravity?

    A:

    The planet with the weakest gravitational pull is Mercury. Mercury's gravitational pull is 3.7 meters per second-squared, which is less than half Earth's gravitational pull of 9.81 meters per second-squared. An object that weighs 100 pounds on Earth would weigh 38 pounds on Mercury.

    Full Answer >
    Filed Under:
  • Q:

    What was Mercury named after?

    A:

    The planet Mercury was named by the Romans after their messenger god, Mercury. Mercury travels the fastest around the Sun, so it was fitting that they chose the god whose hat and shoes were winged, enabling him to move swiftly through the skies. The element known as Mercury was named after the planet.

    Full Answer >
    Filed Under:
  • Q:

    What is the closest planet to Saturn?

    A:

    Based on their respective distances from the sun, Jupiter is the planet that can approach Saturn most closely. Even so, the two planets are still over 400 million miles apart at the closest point in their orbits.

    Full Answer >
    Filed Under:

Explore