NASA Pluto flyby honored with USPS stamp series

CAPE CANAVERAL, Fla. -- The U.S. Postal Service on Wednesday previewed a new series of 2016 space-themed stamp sets honoring both the planetary discoveries made by NASA and a stand alone set honoring the exciting views of the dwarf planet Pluto.

One of the space milestones of 2015 was the arrival and flyby of Pluto by NASA's New Horizons spacecraft. New Horizons captured thousands of colorful photographs of the farthest planet from the Sun, a place yet unseen by human eyes until last July.

A four stamp sheet will feature two of the color enhanced view of Pluto highlighted by the popular heart shaped region named Tombaugh Regio. The second stamp is an artist's depiction of the spacecraft soaring through space. The Pluto stamps will be available in June.

“The New Horizons project is proud to have such an important honor from the U.S. Postal Service,” New Horizons principal investigator Alan Stern said on Wednesday. “It’s a wonderful feeling to see these new stamps join others commemorating first explorations of the planets.”

The Pluto stamps will arrive 25 years after the Postal Service released the first Pluto stamp which featured an artist's rendition of the unseen planet. The 29-cent stamp was titled "Pluto Not Yet Explored". In 2006, NASA launched that stamp aboard New Horizons and today that stamp

NASA New Horizons historic flyby of Pluto underway

New Horizon images of the icy dwarf planet Pluto. (NASA)

After traveling over three billion miles a small NASA spacecraft is making a historic fly-by of the icy dwarf planet Pluto and returning the first up close images and science data ever recorded.

Soaring at the edge of our solar system at 30,802 m.p.h., New Horizons closest approach to Pluto occurs at 7:49 a.m. EDT on Tuesday. However, new color images and scans of the small planet by a host of science instruments have already giving scientists a fresh look at the size of the unknown celestial body.

(NASA is live streaming video and images of the Pluto encounter here. You can also have real time access to exactly where the space craft is here. Follow the mission on social media via #PlutoFlyby.)

New Horizons mission scientist Bill McKinnon stated on Monday that the decades old debate on the size of Pluto has been answered -- 1,473 miles in diameter. "The size of Pluto has been debated since its discovery in 1930. We are excited to finally lay this question to rest,” McKinnon added.

New images are making NASA scientists grin. "For the first time on Pluto, (new) views reveals linear features that may be cliffs, as well as a circular feature that could be an impact crater," NASA Spokesperson Tricia Talbert discussed on Monday. "Rotating into view (above) is the bright heart-shaped feature that will be seen in more detail during New Horizons’ closest approach."

Pluto (right) and its moon Charon from New Horizons (NASA)

The size of three of the planet's five moons were also discovered, including its largest moon Charon at 751 miles. McKinnon said that the moon's atmosphere does not have a substantial atmosphere.

NASA is referring to Pluto and Charon as the "dynamic duo". Principal Investigator Alan Stern of Boulder, Colorado explained, “These two objects have been together for billions of years, in the same orbit, but they are totally different."

Pluto's smaller moons Hydra and Nix -- 30 miles and 20 miles in diameter, respectively -- likely have icy surfaces giving the two a brilliantly light surface as seen from a distance. These two moons were discovered in 2005 during an observation by the Hubble Space Telescope.