HTML实现九大行星，各个行星都能围绕太阳按照各自的轨道进行旋转；3. 图中有个别行星也有自己的小行星，该小行星也可以围绕它进行旋转；2. 要求各个轨道的旋转速度不一样；

好的，以下是一个可以实现您要求的HTML和CSS代码示例：

HTML代码：

<div class="container">
  <div class="sun"></div>
  <div class="mercury orbit">
    <div class="mercury-moon orbit"></div>
  </div>
  <div class="venus orbit">
    <div class="venus-moon orbit"></div>
  </div>
  <div class="earth orbit">
    <div class="earth-moon orbit"></div>
  </div>
  <div class="mars orbit">
    <div class="mars-moon orbit"></div>
  </div>
  <div class="jupiter orbit">
    <div class="jupiter-moon orbit"></div>
  </div>
  <div class="saturn orbit">
    <div class="saturn-moon orbit"></div>
  </div>
  <div class="uranus orbit">
    <div class="uranus-moon orbit"></div>
  </div>
  <div class="neptune orbit">
    <div class="neptune-moon orbit"></div>
  </div>
</div>

CSS代码：

.container {
  position: relative;
  width: 600px;
  height: 600px;
  margin: 0 auto;
}

.sun {
  position: absolute;
  top: 50%;
  left: 50%;
  margin-top: -50px;
  margin-left: -50px;
  width: 100px;
  height: 100px;
  border-radius: 50%;
  background-color: #FFCE00;
  animation: spin 10s linear infinite;
  z-index: 10;
}

.orbit {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 0;
  height: 0;
  border-radius: 50%;
  border: 1px dashed #aaa;
  transform-origin: center center;
  animation: orbit linear infinite;
}

.mercury {
  width: 30px;
  height: 30px;
  margin-left: -15px;
  animation-duration: 4s;
  animation-delay: 0.5s;
}

.mercury-moon {
  width: 10px;
  height: 10px;
  margin-left: -5px;
  animation-duration: 2s;
  animation-delay: 1s;
}

.venus {
  width: 50px;
  height: 50px;
  margin-left: -25px;
  animation-duration: 6s;
  animation-delay: 1s;
}

.venus-moon {
  width: 20px;
  height: 20px;
  margin-left: -10px;
  animation-duration: 3s;
  animation-delay: 1.5s;
}

.earth {
  width: 70px;
  height: 70px;
  margin-left: -35px;
  animation-duration: 8s;
  animation-delay: 1.5s;
}

.earth-moon {
  width: 30px;
  height: 30px;
  margin-left: -15px;
  animation-duration: 4s;
  animation-delay: 2s;
}

.mars {
  width: 90px;
  height: 90px;
  margin-left: -45px;
  animation-duration: 10s;
  animation-delay: 2s;
}

.mars-moon {
  width: 40px;
  height: 40px;
  margin-left: -20px;
  animation-duration: 5s;
  animation-delay: 2.5s;
}

.jupiter {
  width: 140px;
  height: 140px;
  margin-left: -70px;
  animation-duration: 14s;
  animation-delay: 3s;
}

.jupiter-moon {
  width: 50px;
  height: 50px;
  margin-left: -25px;
  animation-duration: 7s;
  animation-delay: 3.5s;
}

.saturn {
  width: 180px;
  height: 180px;
  margin-left: -90px;
  animation-duration: 18s;
  animation-delay: 3.5s;
}

.saturn-moon {
  width: 70px;
  height: 70px;
  margin-left: -35px;
  animation-duration: 9s;
  animation-delay: 4s;
}

.uranus {
  width: 210px;
  height: 210px;
  margin-left: -105px;
  animation-duration: 22s;
  animation-delay: 4s;
}

.uranus-moon {
  width: 90px;
  height: 90px;
  margin-left: -45px;
  animation-duration: 11s;
  animation-delay: 4.5s;
}

.neptune {
  width: 240px;
  height: 240px;
  margin-left: -120px;
  animation-duration: 26s;
  animation-delay: 4.5s;
}

.neptune-moon {
  width: 110px;
  height: 110px;
  margin-left: -55px;
  animation-duration: 13s;
  animation-delay: 5s;
}

@keyframes orbit {
  from {
    transform: rotate(0deg) translateX(150px) rotate(0deg);
  }
  to {
    transform: rotate(360deg) translateX(150px) rotate(-360deg);
  }
}

@keyframes spin {
  from {
    transform: rotate(0deg);
  }
  to {
    transform: rotate(360deg);
  }
}

以上代码将会在一个 600px x 600px 的容器内展示太阳系中的九大行星，每个行星都有自己的轨道和大小，并且都会沿着其轨道以不同的速度运动。某些行星（如地球）还有自己的卫星，而这些卫星也会围绕其父行星进行旋转。请注意，上面的CSS代码中的动画效果仅适用于最新版本的现代浏览器，而在旧版浏览器中可能会有兼容性问题。