The University of Texas at Arlington

The University of Texas at Arlington

UTA Planetarium

UTA Planetarium

Ask the Astronomer Q&A

Tag: "mercury"

  • I have an app on my phone that let's me explore the solar system and I noticed that Mercury and Venus don't appear to rotate. Is their rotation just really slow or is there none at all?
  • Mercury and Venus both rotate very slowly. It takes over 58 days for Mercury to rotate once, and 244 days for Venus to rotate once.

    (Tags:  mercury  solar system  venus)
  • Why doesn't Mercury have moons?
  • Most moons are captured asteroids or rocks left over from the formation of the solar system. Since Mercury is so close to the Sun, asteroids and comets that come close by are captured by the Sun’s gravity. They are either pulled in to the Sun and burned up or they go around the Sun as comets. Mercury doesn’t have as strong a pull of gravity as the Sun, so it is unlikely that it would be able to redirect the path of any incoming objects to turn them into moons.

    (Tags:  asteroid  comet  gravity  mercury  moon  sun)