Pluto and dark matter both star in a busy week for astronomers (2/2)

Scientists can observe what they believe to be dark matter only through its gravity. But the team says the crash was violent enough to break dark matter away from normal matter. Normal matter in galaxy clusters is mostly in the form of hot gas and stars.

They call it the strongest evidence yet that most of the matter in the universe is dark.

They say the observations cannot be explained by theories of gravity that remove the need for dark matter. These theories propose that gravity is stronger with huge galaxy clusters than the theories of Isaac Newton or Albert Einstein would suggest. The findings will appear in the Astrophysical Journal Letters.

Now on to Pluto. This week the International Astronomical Union met in Prague, in the Czech Republic, with the goal to officially define a planet.

Scientists voted to set three requirements for a planet. One, it must orbit the sun. Two, it must have enough mass so that its own gravity has formed it into a nearly round shape. And three, it must have cleared the area of other objects around its orbit. That is where Pluto fails: its orbit around the sun crosses paths with Neptune’s.

专有名词

Isaac Newton  以撒·牛顿

Albert Einstein 阿尔伯特·爱因斯坦

Prague  布拉格

Czech Republic  捷克

Neptune  海王星

 

生词

theory  n. 理论

propose  v. 计划，打算，向……提议

astrophysical  adj. 天体物理学的

orbit  n. 轨道，常规，眼眶　v. 绕轨道而行，进入轨道，盘旋

 

翻译

科学家们只有通过重力才能观测到他们所认定的暗物质。但这组科学家表示，这次的撞击猛烈到足以将暗物质从常规物质中分离出来。星系团中的常规物质大多以炽热气体和星体的形式存在。

他们把它称作是证明宇宙中大部分物质是暗物质的最有力证据。

他们认为如果排除了必需的暗物质，这个观测结果是无法用重力理论来解释的。这些理论提出，巨大星系团中的重力要比牛顿或爱因斯坦的理论中所提出的要大。这些发现将会发表在Astrophysical Journal Letters上。

现在说冥王星。本周，国际天文学联合会的成员们为了正式确定行星的定义，聚集在捷克的布拉格。

科学家们通过投票确定了三项作为行星必要条件。第一，它必须围绕太阳进行公转。第二，它必须有足够大的质量，从而能通过自身的重力形成近圆的形状。第三，在其公转轨道上不能有其它物体存在。那就是冥王星所不符合的：它的公转轨道与海王星的相交了。

posted on 2006-08-29 16:51 annika 阅读(397) 评论(0)  编辑  收藏 所属分类: 慢速VOA 网摘收藏