For the first time, images of Styx and Kerberos, the smallest and the faintest of five known moons in Pluto, have been captured by the New Horizons spacecraft. NASA released images of Pluto's moons Wednesday, marking a point in the spacecraft's journey.

New Horizons is slowly getting closer to Pluto, and since it's already spotted five of the planet's moons, any additional moons it observes will have never been seen before, according to John Spencer, a mission science team member from the Southwest Research Institute. The spacecraft will start searching first for rings or new moons that might impede its passage through Pluto's system.

The two moons were discovered in 2011 and 2012 respectively. Styx and Kerberos were first observed by New Horizons team members with the help of the Hubble Space Telescope. Styx goes around Pluto in 20-day intervals, passing between the orbits of Charon and Nix. Kerberos, on the other hand, orbits between Hydra and Nix and measures between six and 20 miles in diameter. Likely, Styx is smaller than Kerberos at just four to 13 miles in diameter, but both are between 20 and 30 times fainter than Hydra and Nix.

The images showing Styx and Kerberos were taken using the Long Range Reconnaissance Imager or LORRI, aboard New Horizons. From April 25 to May 1, five exposures lasting 10 seconds each were captured and then combined to come up with the moons' images released by NASA. Extensive processing had to be employed though, to reduce bright glares from Charon and Pluto and reveal the orbits and positions of the moons.

In some of the frames captured, Styx and Kerberos were more visible than the other moons because of fluctuations in brightness caused by rotating on axes. However, the moons were confirmed as they were in the exact spots where they were predicted to be located.

Alan Stern, principal investigator for New Horizons and also from the Southwest Research Institute, said it was amazing to be able to detect such tiny moons given their distance of over 55 million miles. He credits the team responsible for building LORRI and John Spencer's team with the achievement.

The Johns Hopkins University Applied Physics Laboratory designed and built New Horizons. The APL also operates the spacecraft, managing the mission for NASA's Science Mission Directorate. New Horizons is included in the New Frontiers Program overseen by the Marshal Space Flight Center.