Edward C Stone was born in 1936 in Knoxville, Iowa, USA and is currently David Morrisroe Professor of Physics and Vice Provost for Special Projects at the California Institute of Technology (Caltech), USA. He obtained his Master degree and his PhD in Physics from the University of Chicago in 1959 and 1964 respectively. He then joined Caltech, where he was successively Research Fellow (1964–1966), Senior Research Fellow (1966–1967), Assistant Professor (1967–1971), Associate Professor (1971–1976) and Professor (1976–1994). Since 1994, he has been appointed David Morrisroe Professor and has served as Vice Provost for Special Projects from 2004. At Caltech, he was also appointed Chairman of Division of Physics, Mathematics and Astronomy from 1983 to 1988, Vice President for Astronomical Facilities (1988–1990) and Vice President and Director of the Jet Propulsion Laboratory (1991–2001). He is a member of the US National Academy of Sciences.

The Voyager project is a NASA mission for exploring the outer planets. It consists of two spacecraft Voyagers 1 and 2 launched in 1977. Having accomplished the primary mission to study Jupiter and Saturn close-up, Voyager 2 also visited Uranus and Neptune. Subsequently, both spacecraft headed away from the solar system and have now entered interstellar space. Voyager 1 also becomes the most distant human artefact now.

The Voyagers dramatically improved our understanding on many aspects of the giant planets, including their masses, shapes, atmospheres, rings and gravitational fields. We learnt much more about the many satellites of the giant planets, and 22 new satellites were discovered. For the foreseeable future, Voyager 2 will remain the only spacecraft visiting Uranus and Neptune. These unique data collected are important for the study of exoplanets, since Uranus and Neptune now appear to be more representative of the bulk of the exoplanet population than the other solar system planets.

Important Dates

Distance from Earth in 2019

(One AU is the distance from the Sun to Earth)

Although Voyager 1 was launched later than Voyager 2, its path allowed it to reach Jupiter earlier than Voyager 2 and so it was called Voyager 1.

Voyager discovered that the magnetic axes of Uranus and Neptune are greatly tilted from their rotational axes and largely offset from the centres. We can imagine that a compass on these two planets will no longer point to the north poles.

Voyager observed that Neptune had a vast storm system: the Great Dark Spot. Its size was as large as Earth, and the wind speed was up to 2000 km/h near the storm. Neptune is the windiest place in the solar system.

Voyager 1 took the ‘family portrait' of solar-system planets from a distance 6 billion km from the Sun. The image of Earth has come to be called the ‘pale blue dot', which has become an icon for how small we are in the larger universe.

Photo credit: NASA/JPL

The family portrait of solar-system planets is a composed composite of 60 frames. Mercury was not seen as it was too close to the Sun. Mars was not detectable due to scattered sunlight in the optics in the camera. The images of planets in the insets are enlarged.

 

Photo credit: NASA/JPL

Our Earth, known as the ‘pale blue dot', in the family portrait of solar-system planets. The light in the background is due to the scattered sunlight in the optics of the camera.