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Voyager 2 confirms that our solar system is dented |
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Written by Derek Kessler on
Sunday, 20 July 2008
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 (From Jul 2, 2008) Hurtling out towards interstellar space, the probe Voyager 2 has come across some surprising insights into the forces at work at the outer fringe of our solar system, confirming that interstellar wind is actually squishing our solar system. Voyagers 1 and 2 were launched more than 30 years ago and are the farthest traveled objects man has ever made.
Both probes have reached the edge of our solar system, an area called the termination shock. In is here that solar wind flowing out from the sun impacts the charged particles of interstellar wind. Astronomers have long hypothesized that just like solar wind deforms the magnetic fields of planets like Earth, then interstellar wind must do the same to the heliosphere created by outbound solar winds.
This suspicion was confirmed when Voyager 2 reached the southern edge of our solar system at 11.2 billion km (76 AU), while it’s twin Voyager 1 had already reached the northern edge at at 12.6 billion km (84 AU) from the sun. The difference of over a billion kilometers shows that the pressure from interstellar wind is greatly squashing the southern reaches of the heliosphere. Voyager 1 crossed the termination shock in December 2004, while Voyager 2 reached it in August 2007.
Many of Voyager 2’s instruments are still working, providing scientists their first hands-on look at the heliosheath (the outer layer of the heliosphere). The probe’s plasma detector revealed that solar wind, which streams out from the sun at 10,000° K (17,500° F), heats up much less than scientists had predicted. Models of the heliosheath indicated that as the solar wind slowed, it could heat up to as much as 1 million degrees Kelvin (1.8 million F). Instead, Voyager 2 instruments revealed that the plasma only reached 100,000° K (180,000° F) at the edge of our solar system.
Instead, much of the energy from the solar wind is transferred to neutral atoms coming in from interstellar space. These particles become energized upon entering the heliosheath and steal around 80% of the solar wind’s energy. The energy transfer puzzled scientists, as did the revelation that solar wind actually slows down before it reaches the termination shock. Solar wind travels at about 400 km/s (258 miles/sec, or 928,000 mph), but before it hits the edge of the solar system, it’s already slowed to 300 km/s (186 miles/sec), and crawls to 150 km/s (93 miles/sec) after the termination shock.
Voyagers 1 and 2 are still functioning and transmitting data back to Earth from the heliosheath and termination shock. Currently, it takes 12 hours for data from Voyager 2 to travel at the speed of light back to Earth, and 14.7 hours for the same to happen from Voyager 2. The two probes are currently traveling at a speed of 500 million km (300 million miles) a year and are estimated to cross into true interstellar space in the next five to seven years. Their plutonium power cores are expected to power the probes until at least 2025, 48 years after launch.
Discuss: TrekUnited Forum
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