Pale blue dot: Voyager 1 signal from interstellar space photographed
The Very Long Baseline Array (VLBA), a network of radio telescopes operated by the National Radio Astronomy Observatory, spotted the signal of NASA's Voyager 1 spacecraft from 11.5 billion miles (18.5 billion kilometers) away. The image was taken on Feb. 21.NRAO / AUI / NSF
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Scientists can't "see" our first interstellar ambassador in the visible spectrum, but they can detect Voyager 1's signal in radio light.
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The 36-year-old spacecraft's communications technology is lacking by today's standards. A smartphone has thousands of times more memory than Voyager 1, and the space probe's main transmitter radiates just 22 watts, about the same amount of power as a typical ham radio or a refrigerator light bulb, NASA said. But compared to many natural objects probed by radio telescopes, Voyager 1's signal is actually quite bright.
On Feb. 21, 2013, researchers tried to glimpse the spacecraft's radio signal using the Very Long Baseline Array (VLBA), a network of powerful radio telescopes spanning from Hawaii to St. Croix.
"They were able to see a blue speck," said Suzanne Dodd, Voyager's project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "And this image represents the Voyager radio signal as seen by the world's most sensitive ground-based telescope."
"It's just a speck in amongst a sea of darkness," Dodd added.
At the time of the observation, Voyager 1 was 11.5 billion miles (18.5 billion kilometers) away from Earth.
The image, which looks slightly oblong because of the array's configuration, is about 0.5 arcseconds on a side, according to NASA. One arcsecond — a unit of size for objects in the night sky — would describe the size of a penny as seen from 2.5 miles (4 kilometers) away. For comparison, the full moon is about 1,800 arcseconds across.
After launching more than three decades ago, Voyager 1 and its twin spacecraft Voyager 2 took a "grand tour" of the solar system, giving us the first up-close glimpses of Jupiter, Uranus and Neptune and several moons of those outer planets.