This July 4th, U.S. citizens around the world may proudly display American flags to celebrate Independence Day while away from home, but they won't hold a candle to the farthest American flag in history, which is leaving the entire solar system behind on NASA's Voyager 1 spacecraft.
The spaceflying American flag is a not a huge version of Old Glory, but will be the only one flying more than 10.5 billion miles (16.9 billion km) from Earth this Fourth of July. It is riding on Voyager 1, a 33-year-old space probe on the outskirts of our solar system.
Another far-flung American flag is flying on Voyager 2, which is about 8.6 billion miles (13.8 billion km) from Earth. Both Voyager 1 and Voyager 2 are on trajectories to leave the solar system behind after passing through a magnetic bubble-like region called the heliosphere.
A NASA photo of the Voyager 2 American flag shows it to be a small U.S. standard packed alongside other mementos from Earth, like the iconic golden record that were also launched the spacecraft and contain messages from Earth for any extraterrestrials that may find them.
"We were extraordinarily proud of what we were doing as a laboratory, as a part of NASA and as a country and we felt it was important to make a statement to that effect," said Jet Propulsion laboratory scientist John Casani, NASA's Voyager project manager at the time it was launched, in a statement provided to SPACE.com this week. "I'm gratified that Voyager is still sailing out there, bearing America's colors. What it represents to us is an affirmation of the pride we had at that time."
Voyager 2's space flag is a 16-inch (40-cm) long version of the Stars and Stripes made of Dacron that engineers painstakingly sewed into the insulating blankets of the Voyager 2 spacecraft, which launched in 1977 on a tour of the solar system's gas giant planets. A similar flag is flying on the Voyager 1 spacecraft, which also launched in 1977 but is not as far from Earth as Voyager 2. [Voyager mission photos.]
The American flags riding the Voyager probes are not the only distant U.S. standards out in space. Flags were planted on the moon by American astronauts during the six Apollo lunar landings in the late 1960s and early 1970s. NASA probes to Mars and elsewhere also include the U.S. standard.
But the two Voyager probes are currently the farthest human-built objects from Earth, making their American flags the most distance from U.S soil. The probes' signals take nearly 13 hours to travel to NASA's worldwide Deep Space Network of listening antennas and back.
NASA launched both spacecraft in the summer of 1977, but only Voyager 2 took a so-called "grand tour" of the solar system when it visited the gas giant planets Jupiter, Saturn, Uranus and Neptune in the 1980s by taking advantage of a rare planetary alignment that occurs once every 176 years. Voyager 1 flew past Jupiter and Saturn.
On June 28, Voyager 2 hit a major milestone when it marked the 12,000th day of its mission. Voyager one, which launched later than its counterpart, will hit the same milestone on July 13.
"I'm proud of the people who worked on this and put so much of their life and energy into building, developing and flying that thing," Casani said. "They did it right."