Sunday, September 15, 2013

Voyager Goes Interstellar

This artist's concept puts solar system distances in perspective. The scale bar is in astronomical units, with each set distance beyond 1 AU representing 10 times the previous distance. One AU is the distance from the sun to the Earth, which is about 93 million miles or 150 million kilometers. Neptune, the most distant planet from the sun, is about 30 AU.

Informally, the term "solar system" is often used to mean the space out to the last planet. Scientific consensus, however, says the solar system goes out to the Oort Cloud, the source of the comets that swing by our sun on long time scales. Beyond the outer edge of the Oort Cloud, the gravity of other stars begins to dominate that of the sun.

The inner edge of the main part of the Oort Cloud could be as close as 1,000 AU from our sun. The outer edge is estimated to be around 100,000 AU.

NASA's Voyager 1, humankind's most distant spacecraft, is around 125 AU. Scientists believe it entered interstellar space, or the space between stars, on August 25, 2012. Much of interstellar space is actually inside our solar system. It will take about 300 years for Voyager 1 to reach the inner edge of the Oort Cloud and possibly about 30,000 years to fly beyond it.

Alpha Centauri is currently the closest star to our solar system. But, in 40,000 years, Voyager 1 will be closer to the star AC +79 3888 than to our own sun. AC +79 3888 is actually traveling faster toward Voyager 1 than the spacecraft is traveling toward it.

Illustration credit: NASA/JPL-Caltech

Note: Of course, this story is major news, and many articles and graphics have been published. The following is some of those available:
* PIA17045: Voyager Captures Sounds of Interstellar Space
* PIA17047: Voyager Signal Spotted By Earth Radio Telescopes
* PIA17048: One Voyager Out, One Voyager In (Artist Concept)
* PIA17049: Voyager in Space (Artist Concept)
* PIA17441: Observed Change in Density Shows Voyager is in Interstellar Space
* PIA17442: Mystery of the Interstellar Magnetic Field (Artist's Concept)
* PIA17460: Moving into Interstellar Space (Artist Concept)
* PIA17461: Heading toward Gliese 445
* PIA17462: Voyager 1 Entering Interstellar Space (Artist Concept)
* PIA17463: Heliosphere Traveling Through Interstellar Space
* PIA17464: Voyager 1 Launch (1977)
* How Do We Know When Voyager Reaches Interstellar Space?
* NASA Spacecraft Embarks on Historic Journey Into Interstellar Space
* Voyager 1 Reaches Interstellar Space

From earlier in the year, see:
* NASA's Voyager 1 Explores Final Frontier of Our 'Solar Bubble'
* Voyager 1 Approaches Interstellar Space

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