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Pluto’s Moon System
These two images, taken about a week apart by NASA's Hubble Space Telescope, show four moons orbiting the distant, icy dwarf planet Pluto. The green circle in both snapshots marks the newly discovered moon, temporarily dubbed P4, found by Hubble in June.
P4 is the smallest moon yet found around Pluto, with an estimated diameter of 8 to 21 miles (13 to 34 km). By comparison, Pluto's largest moon Charon is 746 miles (1,200 km) across. Nix and Hydra are roughly 20 to 70 miles (32 to 113 km) wide.
The new moon lies between the orbits of Nix and Hydra, two satellites discovered by Hubble in 2005. It completes an orbit around Pluto roughly every 31 days.
The moon was first seen in a photo taken with Hubble's Wide Field Camera 3 on June 28, 2011. The sighting was confirmed in follow-up Hubble observations taken July 3 and July 18.
P4, Nix, and Hydra are so small and so faint that scientists combined short and long exposures to create this image of Pluto and its entire moon system. The speckled background is camera "noise" produced during the long exposures. The linear features are imaging artifacts.
The tiny satellite was uncovered in a Hubble survey to search for rings around the frigid dwarf planet. The observations will help NASA's New Horizons mission, scheduled to fly through the Pluto system in 2015.
About the Object
- DistanceDistanceThe physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs.Although its orbit is highly eccentric, Pluto's average distance from the Sun is 39.44 astronomical units (roughly 3.6 billion miles or 5.9 billion kilometers).
- DimensionsDimensionsThe physical size of the object or the apparent angle it subtends on the sky.Pluto has a diameter of roughly 1,416 miles (2,280 kilometers) at the equator.
About the Data
- Data DescriptionData DescriptionProposal: A description of the observations, their scientific justification, and the links to the data available in the science archive.
Science Team: The astronomers who planned the observations and analyzed the data. "PI" refers to the Principal Investigator.This image was created from HST data from proposal 12436: M. Showalter (SETI Institute) and D. Hamilton (University of Maryland). - InstrumentInstrumentThe science instrument used to produce the data.HST>WFC3/UVIS
- Exposure DatesExposure DatesThe date(s) that the telescope made its observations and the total exposure time.June 28, 2011 and July 3, 2011
- FiltersFiltersThe camera filters that were used in the science observations.F606W (V)
- Object NameObject NameA name or catalog number that astronomers use to identify an astronomical object.Pluto
- Object DescriptionObject DescriptionThe type of astronomical object.Dwarf Planet
- Release DateJuly 20, 2011
- Science ReleaseNASA’s Hubble Discovers Another Moon Around Pluto
- Credits
This image was originally black and white and recorded only overall brightness. These brightness values were translated into a range of bluish hues. Such color "maps" can be useful in helping to distinguish subtly-varying brightness in an image. The colors in this image are not what human eyes would see looking at Pluto.
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Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov
