In 1991 the U.S. Postal Service issued a 29-cent stamp honoring Pluto as last unexplored planet in the solar system.
Twenty-five years later, Pluto has lost its designation as a full-fledged planet, but gained a visitor -- and a new stamp to set the record straight.
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NASA's New Horizons spacecraft soared past Pluto and its entourage of moons last July, the first probe to visit an object beyond what is now considered the solar system's outermost planet, Neptune.
"In 1991, the Postal Service issued a Pluto: Not Yet Explored stamp that served as a rallying cry for those who very much wanted to explore it," U.S. Postal Service chief operating officer David Williams said in a press release.
On Tuesday, the USPS issued two new sets of Forever stamps titled "Pluto – Explored!" and "Views of Our Planets" to honor the New Horizons team and NASA's ongoing exploration of the solar system.
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"We're grateful to the U.S. Postal Service for commemorating this historic achievement," Jim Green, NASA's director of planetary science, said in the press release.
"The 1991 stamp ... highlighted some important, unfinished business for NASA's first exploration of the planets of our solar system," added New Horizons lead scientist Alan Stern. "I'm thrilled that ... these new stamps recognize that Pluto has indeed been explored ... and revealed to be a complex and fascinating world."
Forever stamps are always equal in value to the cost of a First-Class, one-ounce stamp, currently 47 cents (following a rare price drop from 49 cents in April – the first time postage prices declined in almost 97 years.)
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