Last month Voyager 1 passed two important milestones. Voyager 1 is currently 120 a.u. or 16 light-hours from earth, and is travelling at over 60,000 kilometers (38,000 miles) per hour. It is the farthest and fastest spacecraft yet built. Even so, it will take another 14,000 years before it travels a single light-year.
First, it detected the Lyman-alpha radiation from the Milky Way galaxy for the first time. We detect Lyman-alpha radiation from other galaxies no problem, but the radiation from our own sun drowns out our ability to detect it coming from our own galaxy. So Voyager 1 is far enough away from the sun that sun's radiation is no longer overwhelming the Lyman-alpha radiation. I find this pretty amazing.
Second, scientists have been estimating that Voyager 1 could break through the heliopause any day now, almost certainly by 2015. This is the point where the solar wind stops pushing outward from the sun because the radiation from nearby stars, the stellar wind or interstellar medium, becomes more powerful than it. The heliopause is usually considered to be the boundary of the solar system. In other words, Voyager 1 is on the verge of entering interstellar space. A month ago, they announced that it had reached a stagnation region or "cosmic purgatory" where the solar wind was starting to turn inward. The interstellar medium is beginning to force the solar wind to turn back toward the sun. Again, I find this pretty amazing.
Sunday, January 8, 2012
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