跨越太阳系的边界（图）   

“航行者”2号太空船在研究日球层外侧。日球层是由太阳风创造的、笼罩在太阳系外围的一个磁性“外罩”。科学家们观察到，这个磁性外罩不是球形的，而是南半球受压向内，而呈扁平状。

Voyager Spacecraft Reveals Solar System Edge

Voyager 2's journey toward interstellar space has revealed surprising insights into the energy and magnetic forces at the solar system's outer edge, and confirmed the solar system's squashed shape.	飞往星际空间的“航行者”2号太空船洞察了太阳系外围边界处的能量及磁力情况，这让人感到惊讶，而且也证实了太阳系受压走形的情况。
Both Voyager 1 and Voyager 2 continue to send data to Earth more than 30 years after they first launched. During the 1990s, Voyager 1 became the farthest manmade object in space.	自从“航行者”1号和“航行者”2号最初发射成功以来，在30多年的时间里不断地向地球发回数据资料。20世纪90年代期间，“航行者”1号曾经成为在太空中飞行最远的人造物体。
Each spacecraft has now crossed the edge of the solar system, known as termination shock, where the outbound solar wind collides with inbound energetic particles from interstellar space. The termination shock surrounds the solar system and encloses a bubble called the heliosphere.	目前，两艘太空船都已经跨越了被称为“边界激波”的太阳系边界。在边界处，向外刮去的太阳风跟从星际空间向内飞来的高能粒子发生碰撞。边界激波包围住太阳系，形成一个被称为“日球层”的封闭外罩。
"The solar wind is blowing outward trying to inflate this bubble, and the pressure from interstellar wind is coming in," said Edward Stone, physicist and Voyager project scientist at Caltech in Pasadena, Calif. He and other researchers published a series of studies in the journal Nature this week that detail the Voyager findings.	“太阳风正在向外刮去，企图使这个外罩变得膨胀起来，同时来自星际风的压力是向内的，”加利福尼亚州帕萨迪纳市加州理工学院的物理学家、研究“航行者”号工程的科学家爱德华·斯通说。斯通和其他研究人员将一系列研究成果发表在本周的《自然》杂志上，详尽地介绍了“航行者”号的发现。
This way and that	两个不同的方向
Voyager 2 reached the southern edge of the solar system 7.8 billion miles (84 AU) from the sun, closer than Voyager 1 which had reached the northern edge 8.7 billion miles (94 AU) from the sun. That confirms earlier suspicions about the heliosphere bubble being squashed at its southern region.	“航行者”2号到达了太阳系的南部边界，距太阳78亿英里（84天文单位），其航程较短；而“航行者”1号到达了太阳系的北部边界，距太阳87亿英里（94天文单位）。这证实了以前对日球层外罩的猜测：太阳系的南区呈扁平状。
The reason for that asymmetrical shape rests with an interstellar magnetic field that puts more pressure on the southern region of the solar system — something that may change over 100,000 years as that magnetic field experiences turbulence, Stone said.	斯通说：太阳系之所以呈现出不对称的形状，是因为星际磁场在太阳系的南区施加了更大的压力；随着星际磁场不断经历动荡局势，这种不对称的情况在10万多年的时间里可能会发生变化。
Comparing the Voyager 1 crossing in December 2004 with the Voyager 2 crossing in August 2007 allowed scientists to confirm that the second sibling actually crossed the termination shock and passed into the heliosheath, an outer layer of the heliosphere. But Voyager 2 also carries more working instruments that show the termination shock in full detail.	“航行者”1号于2004年12月跨越了太阳系的边界，“航行者”2号于2007年8月跨越了太阳系的边界。科学家们将两次跨越进行了对比，结果证明： 实际上“航行者”2号跨越了边界激波，进入了日球层的外层——日鞘之中。但是，“航行者”2号也携带着较多处于运行状态的仪器，可以极为详尽地显示边界激波的情况。
"We're actually seeing the shock for the first time," said John Richardson, principal scientist for Voyager's Plasma Physics instrument at MIT in Cambridge, Mass.	“其实，我们这是第一次看到激波，”马萨诸塞州剑桥市麻省理工学院研究“航行者”号等离子物理装置的首席科学家约翰·理查森说。
Voyager 1's plasma detector failed after it passed Saturn, so Voyager 2 provided the first glimpse of what happens to the solar wind's energy as it slams into interstellar space. The solar wind travels outwards from the sun at supersonic speeds, and at temperatures near 17,540 degrees Fahrenheit (10,000 degrees Kelvin).	“航行者”1号越过土星之后，上面搭载的等离子体探测器失灵了。这样，当太阳风冲到星际空间的时候，由“航行者”2号首次观测到太阳风能量所发生的变化。太阳风以超音速从太阳朝外围穿行，温度将近17,540华氏度（10,000开氏度）。
Scientists had predicted that the solar wind would simultaneously slow down and heat up to a temperature near 1.8 million degrees F (1 million degrees Kelvin), but instead found that it reached just 180,000 degrees F (100,000 degrees Kelvin) at the solar system boundary.	科学家们曾经预测，太阳风在穿行的时候速度会降低下来，并且温度会升高到近180万华氏度（100万开氏度）。可是，结果却发现在太阳系边界处，太阳风的温度仅仅达到18万华氏度（10万开氏度）。
Hitching a ride	搭回程车
The solar wind's missing energy ended up hitching a ride with interstellar intruders, Richardson said.	理查森说，太阳风丢失的能量最终却搭上了侵入系内的星际风之车。
Neutral atoms that flowed in from outside the solar system became energized upon entering the heliosheath layer, and then ended up stealing 80 percent of the energy from the solar wind. Researchers have yet to puzzle out the significance of this.	从太阳系以外流入的电中性原子，一进入日鞘层便带上了电荷，结果从太阳风中窃取了80%的能量。研究人员仍然不得不苦苦思索这一窃取事件的意义。
An added mystery remains as to why the solar wind slows down early, as though anticipating running headlong into the termination shock. Researchers have begun looking into whether the solar wind somehow sheds energy ahead of time.	还有一个不解之谜一直存在：太阳风为何提前降低速度，就好象能够预见要迎头撞到边界激波了？研究人员已经开始观察，看看太阳风是否由于某种原因而提前流失了能量。
"Somehow the solar wind knows the shock is coming before it gets there, and theory says that shouldn't be," Richardson noted, adding that the solar wind speed drops from its supersonic speed of about 248 miles per second (400 km/s) to 186 miles per second (300 km/s) even before hitting the edge of the solar system. That speed falls more noticeably to about 93 miles per second (150 km/s) after the termination shock.	“不知何故，在到达边界激波之前太阳风就知道激波就在面前。但是从理论上讲，情况不应该是这样的，”理查森指出。他还说，就在撞击到太阳系边界之前，太阳风速度从每秒钟248英里（400 km/s）的超音速降至每秒钟186英里（300 km/s）。穿过边界激波之后，太阳风速度更是显著下降，大约降为每秒钟93英里。
Even as researchers continue parsing the Voyager findings, both spacecraft plow onward toward deep space — and beyond all expectations of their original mission.	正当研究人员继续分析“航行者”号的发现时，这两艘太空船也在朝着太空深处艰难地行进——相对于起初赋予它们的使命来说，这已经远远超出了科学家们的预料。
"My guess is five to seven years to reach interstellar space," Stone said. "There's a very good chance that Voyager I will send the first data back from there."	“据我推测，两艘太空船用5到7年的时间就能到达星际空间，”斯通说，“很可能，‘航行者’1号将从那里发回第一批数据资料。”