NASA’s unmanned Voyager 2 space probe leaves the vicinity of the planet Neptune, the outermost planet to have been explored by a man-made spacecraft. (At this point in time, Pluto is still considered a planet – the only one to which NASA hasn’t sent a space probe – though by the time a vehicle is dispatched to Pluto in the 21st century, Pluto has been demoted to “minor planet” status.) Though not expected to function beyond 2025 due to the slow decay of its nuclear power source, Voyager 2 may survive long enough to pass within 25,000,000,000,000 miles of Sirius in a quarter of a million years.
At the request of astronomer Carl Sagan, NASA and JPL reawaken Voyager 1‘s camera for a last look back at Earth and its solar system, from a mind-boggling distance of 4,000,000,000 miles. The “last look” is actually composed of 60 separate photos, capturing most of the planets (with the exception of Mars and Mercury), including Earth – which takes up less than a single pixel in the image. Sagan points to the image as evidence of the fragility and uniqueness of Earth, and names his next book after the photo, “Pale Blue Dot”, also centered on that theme.
Its collision with the solar system’s largest planet predicted over a year in advance, the fragments of Comet Shoemaker-Levy 9 begin impacting Jupiter’s atmosphere in an astronomical event lasting six days. With Earth-based telescopes watching, as well as cameras and instruments on the Hubble Space Telescope, Galileo and even Voyager 2, huge explosions are witnessed as the cometary chunks slam into Jupiter’s southern hemisphere at over 200,000 miles per hour, leaving dark “scars” larger than the diameter of Earth visible on the planet’s atmosphere and releasing more heat than the surface of the sun. Galileo is still over a year away from arriving at Jupiter.
Unmanned space prove Voyager 1, launched in 1977, surpasses its forerunner Pioneer 10 as the furthest man-made object in space. Due to a sharp increase in its speed imparted by a very close pass by Saturn’s large moon Titan in 1980, Voyager 1 has outrun Pioneer 10, which was launched in 1972. Both vehicles are still returning science data, and Voyager 1 is now 6.5 billion miles from the sun, 70 times further out from the sun than Earth. Voyager’s on-board nuclear power source is expected to keep it active through 2020.
NASA’s Voyager 2 spacecraft, nearly ten years after its final planetary encounter, suddenly goes quiet. For 66 hours, the space probe returns no signal or telemetry data to Earth, while engineers on the ground send 720 commands to Voyager 2 to begin transmitting again. When Voyager 2 does re-establish communications with Earth, it has switched to a backup transmitter, and the temperature of some on-board components is warmer than expected. The spacecraft has not gone into a safe mode, but reports receiving only 19 of the 720 commands to transmit. At nearly six billion miles from Earth, Voyager 2 is heading for the edge of the solar system at 35,000 miles per hour, and is expected to remain functional into the 2020s, provided the spacecraft experiences no further major faults.
Launched ahead of its identical twin, Voyager 1, in 1977, NASA’s Voyager 2 spacecraft surpasses its 10,000th day in deep space. At 11 billion miles from Earth, Voyager 2 is one of the most distant human-made objects in space, surpassed only by Voyager 1. Both Voyagers are expected to function well into the 2020s, and are expected to have left the solar system to enter interstellar space by then.
NASA’s Voyager 2 probe, having recently celebrated its 30th anniversary in deep space, sends back observations and instrument readings that lead scientists to a surprising conclusion: the “bubble” of the sun’s solar wind and magnetic influence isn’t spherical or even egg-shaped. Voyager 2′s readings, including the fact that it crossed what should’ve been the boundary of the sun’s outermost influence several times, have revealed that the solar system’s outermost boundary is in flux. Scientists theorize that the “dent” in that bubble is caused by the interstellar magnetic field of the Milky Way galaxy itself. Voyager 2 is now over 10 billion kilometers from the sun – or, to put that in perspective, 80 times further away from the sun than Earth is.
35 years after its departure from Earth, NASA’s Voyager 1 space probe registers major changes in its environment, including a large spike in radiation readings believed to indicate the presence of interstellar cosmic radiation. Some scientists claim that these changes in Voyager 1’s surroundings meet the expected criteria for space beyond the influence of Earth’s sun, making Voyager 1 the first man-made craft to reach interstellar space; others, including former Voyager project scientists, disagree with that assessment. Voyager 1 has no further planetary stops, and is expected to pass within two light years of the star Gliese 445 in 40,000 years.
Bradford A. Smith, a research astronomer and former professor of planetary science and astronomy at the University of Arizona, dies at the age of 86 from complications arising from an autoimmune disorder. Smith became a public figure during the peak years of the uncrewed Voyager missions in the 1970s and ’80s, where, as the head of the imaging team for Voyagers 1 and 2, it fell to him to interpret freshly-received images from the outer planets and their moons for the press and the public, combining authoritative knowledge with a dry sense of humor at press conferences. Smith had reshaped the specs for Voyager’s onboard cameras since the mission was given the go-ahead in 1972, not only pushing for more powerful telescopic optics, but going out of his way to hire geologists and planetary science experts who could interpret the geological processes shaping the moons of Jupiter, Saturn, Uranus and Neptune from photos alone. When the moons of Jupiter greeted Voyager’s cameras with recently-reshaped surfaces and active volcanoes, that decision paid off. Prior to the Voyager mission, Smith had also been involved with imaging science in the Mariner and Viking missions to Mars, as well as helping to shape the specs for the planetary camera being developed for the yet-to-be-launched Hubble Space Telescope and advising imaging teams working on later missions.
Launched in August 1977 prior to the departure of its sister ship, Voyager 1, NASA’s Voyager 2 space probe exits the heliosphere, the region where the solar wind from Earth’s sun has more influence than the interstellar medium between stars. Unlike Voyager 1, Voyager 2’s plasma science instruments are still working, so the instrument readings indicating a dramatic change in local space are very clear to the vehicle’s ground controllers (Voyager 1’s exit from the heliosphere in 2012 had been much more ambiguous at first). At over eleven billion miles from the Earth, radio signals take more than 16.5 hours to reach or be received from Voyager 2 at the time of its entry into the interstellar medium, and it is expected to return science data through the 2020s. It will pass within two years of the star Ross 248 in 40,000 years.