The Grand Tour Continues
Over the past 35 years the Voyager probes have been an inspiration to many, a human project spanning the generations. Originally envisioned as a grand tour of the planets, the mission expanded to encompass the outer reaches of the solar system and beyond into interstellar space. A rare planetary alignment facilitated the use of the gravity assist technique. This dance among the planets allowed the probes to steal kinetic energy, accelerating to extraordinary speeds; they will travel a further 1000 km in the time it takes you to read this article. The venerable spacecraft continue to provide new revelations, such as the discovery in 2011 of ‘magnetic bubbles’ in the heliosheath separating the Sun’s sphere of influence from the interstellar medium. It now appears that in the wrinkled and twisted fringe of the Sun’s magnetic field, magnetic reconnection forms self-contained regions more than 100 million km across, with only tenuous connections to the broad structure of the solar magnetic field. A ‘foam’ of magnetic bubbles may even form a partial barrier, protecting the solar system from bombardment by cosmic rays. It is a testament to the robustness of the 1970s era technology that most instruments are still available for use, although many have been disabled to conserve energy. The onboard radioisotope thermoelectric generators are projected to keep some instruments functioning until 2025. What then? In 40,000 years, Voyager 1 will pass within 1.6 light years of the star Gliese 445. With no power and hence no electromagnetic emissions, it seems a forlorn hope that this tiny spec in a vast cosmos will ever be discovered by another civilisation. But just in case, both probes carry with them the Voyager Golden Record, bearing messages from J.S. Bach, Chuck Berry and others, painting a picture of humanity for whomever they might encounter.
Guest article by Jeffrey Philippson