Tuesday, December 11, 2018

NASA's Voyager 2 Enters Interstellar Space

    In a news conference yesterday, NASA announced that its Voyager 2 probe exited the heliosphere - the protective bubble composed of particles from the solar wind created by our Sun. This marks the second time in history in which a human-made object has left the near solar system.
    Comparing data gathered using different instruments on the spacecraft, scientists realized that the probe crossed the boundary on November 5. Although Voyager 1 made this crossing six years ago, Voyager 2 will be able to provide unique observations through its still-functioning array of instruments unlike its predecessor.
    Scientists realized that the spacecraft left the solar system when Voyager 2's Plasma Science Experiment (PLS) observed a steep decline in the speed of the solar wind particles on Nov. 5. Since that time, this instrument has detected virtually no solar wind flow in its environment around Voyager. 
     "Working on Voyager makes me feel like an explorer, because everything we're seeing is new," said John Richardson, principal investigator for the PLS instrument and a principal research scientist at the Massachusetts Institute of Technology in Cambridge. "Even though Voyager 1 crossed the heliopause in 2012, it did so at a different place and a different time, and without the PLS data. So we're still seeing things that no one has seen before."
    Although both probes have crossed the heliosphere, these two spacecraft have not left the solar system entirely. The boundary of the solar system is considered to be beyond the outer edge of the Oort Cloud. The distance of this collection of small objects under the gravity of the Sun is currently known, but it is estimated that it may begin 1,000 astronomical units (AU) from the Sun and extend to over 100,000 AU.

Image Credit: NASA/JPL-Caltech

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