Voyager I at the Heliopause

[Valin]

The American

An extension of human ingenuity will soon reach the farthest limit of the sun’s empire. Beyond is true interstellar space.

John Steele Gordon

January 18, 2013

 

 

If you would like to get an idea of how fast the reach of humankind is accelerating, consider this. In 1783, only 230 years ago, the Montgolfier brothers gave a public demonstration of the world’s first practical antigravity device, the hot-air balloon. It reached an altitude of about one mile. And 160 years later, a V-2 rocket, sent straight up, reached 128 miles.

 

But then in 1977, barely a quarter-century later, NASA launched Voyager I. Today that spacecraft has traveled 11 billion miles from Earth, 85 million times as far as that V-2 rocket of 60-odd years ago. And unlike the Montgolfier balloon and V-2, Voyager will never return to Earth. Until its power source gives out in 15 years or so, it will continue to send data back to the planet from which it is receding at more than 38,000 miles per hour. Then, dark and silent, it will cruise through space for eternity.

 

At Voyager’s distance today, the sun appears as no more than a point source of light, such as the stars in the night sky appear to us. Of course, it is still a very, very bright point source of light, at magnitude -16.3. That is roughly 40 times as bright as the full moon appears to us.

 

Voyager has traveled so far that it is now near the heliopause. At the heliopause, the solar wind — the stream of charged particles that emanates from the sun and causes such phenomena as aurorae and the tails of comets — becomes so attenuated that it blends into the interstellar medium. The heliopause, in other words, is the farthest limit of the sun’s empire. Beyond is true interstellar space, the empire of the Milky Way.

 

(Snip)

 

 

Published on Jul 9, 2012