59 The Outer Solar System-Mid

The Outer Solar System FOCUS Question What exists beyond the planets in the solar system?

太阳系外焦点问题太阳系行星之外存在什么?

Beyond the Planets You may think that once you've passed Neptune, you've left the solar system. But you have a long way to go! The outer solar system is home to the Kuiper (KY-pur) Belt and Oort Cloud. This huge expanse of space contains trillions of comets and other frozen bodies. The Kuiper Belt is a disc-shaped region surrounding the Sun. It is located beyond Neptune's orbit. It is a bit like the Asteroid Belt. Instead of asteroids, it is made up of comets and other interesting space objects. The Oort Cloud is a large region much farther from the Sun than the Kuiper Belt. It is a massive sphere that surrounds the entire solar system.

你可能认为一旦你经过了海王星，你就离开了太阳系。 但你还有很长的路要走!太阳系外是柯伊伯(KY-pur)带和奥尔特云的所在地。 这片广阔的空间包含了数万亿颗彗星和其他冰冻天体。 柯伊伯带是围绕太阳的圆盘状区域。 它位于海王星轨道之外。 它有点像小行星带。 它不是小行星，而是由彗星和其他有趣的太空物体组成。 奥尔特云是一个比柯伊伯带离太阳远得多的大区域。 它是一个巨大的球体，围绕着整个太阳系。

Solar Leftovers The Kuiper Belt and Oort Cloud contain material left over from the birth of the Sun and solar system. It happened a bit like this: 1 The solar system was formed from the solar nebula—an area of dust and gas. 2 This huge nebula began to pull together (or condense) and swirl forming a disc. 3 Pressure at the disc's center was intense. It was so great that atoms began to combine. This process is called fusion. The Sun was born!

柯伊伯带和奥尔特云包含了太阳和太阳系诞生时遗留下来的物质。 事情是这样的:1太阳系形成于太阳星云——一个由尘埃和气体组成的区域。 这个巨大的星云开始聚集在一起(或凝结)并旋转形成一个圆盘。 圆盘中心的压力很大。 它是如此之大，以至于原子开始结合。 这个过程被称为聚变。 太阳诞生了!

4 The leftover material clumped together here and there. forming larger and larger objects. These objects became the planets. 5 Toward the outer reaches of the solar system. smaller objects remained. They formed the Kuiper Belt and Oort Cloud. Today, the Kuiper Belt and Oort Cloud give us glimpses of what the early solar system was like.

剩下的料子到处结块。 形成越来越大的物体。 这些物体变成了行星。 向着太阳系的外围延伸。 更小的物体仍然存在。它们形成了柯伊伯带和奥尔特云。 今天，柯伊伯带和奥尔特云让我们得以一窥早期太阳系的模样。

In the Kuiper Belt: Dwarf Planets, Most dwarf planets including Pluto, call the Kuiper Belt home. Pluto was discovered in 1930. At first, it was considered the ninth planet. It is smaller than Earth's moon and has five moons of its own. Then Eris was discovered in 2003. It's nearly the same size as Pluto. Eris doesn't qualify as a planet. Scientists decided to downgrade Pluto to a dwarf planet. Makemake (MAH-kay MAH-kay) and Haumea are also dwarf planets in the Kuiper Belt. Characteristics of a Planet large round orbits a star has an atmosphere the largest object in its orbit by far

柯伊伯带:矮行星，包括冥王星在内的大多数矮行星都以柯伊伯带为家。 冥王星于1930年被发现。 起初，它被认为是第九大行星。 它比地球的月球小，有五个自己的卫星。 2003年，阋神星被发现。 它几乎和冥王星一样大。 厄里斯不符合行星的标准。 科学家们决定把冥王星降级为矮行星。 Makemake (MAH-kay MAH-kay)和妊神星也是柯伊伯带的矮行星。 行星的特征大而圆的轨道一颗恒星有大气层是其轨道上最大的物体

In the Kuiper Belt: Comets and Discs Besides dwarf planets, the Kuiper Belt is home to billions of icy comets. These comets are short- period comets. They complete their orbits around the Sun in two hundred years or less. Sometimes overlapping the Kuiper Belt are Scattered Disc objects. These objects are affected by Neptune's powerful gravity. The tug of this gas giant pulls them into unusual orbits. The dwarf planet Eris is a Scattered Disc object. Math Moment Halley's Comet is a famous short- period comet that is visible from Earth about every 75 years. It was last seen in 1986. When will it return?

除了矮行星，柯伊伯带还有数十亿颗冰冷的彗星。 这些彗星是短周期彗星。 它们在200年或更短的时间内绕太阳运行一周。 有时重叠柯伊伯带的是分散盘状天体。 这些物体受到海王星强大引力的影响。 这个气体巨星的引力把它们拉进了不寻常的轨道。 矮行星厄里斯是一个散斑天体。 哈雷彗星是一颗著名的短周期彗星，从地球上大约每75年就能看到一次。 它最后一次出现是在1986年。它什么时候会回来?