1. The Johns Hopkins University Applied Physics Laboratory, Space Department, 11100 Johns Hopkins Road, Laurel, Maryland 20723-6099, USA
2. Department of Space Studies, Southwest Research Institute, 1050 Walnut Street, Suite 400, Boulder, Colorado 80302, USA
3. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218, USA
4. Lowell Observatory, 1400 W. Mars Hill Road, Flagstaff, Arizona 86001, USA

Correspondence to: H. A. Weaver¹ Correspondence and requests for materials should be addressed to H.A.W. (Email: hal.weaver@jhuapl.edu).

Abstract

Pluto's first known satellite, Charon, was discovered¹ in 1978. It has a diameter (1,200 km) about half that of Pluto^{2, 3, 4, 17}, which makes it larger, relative to its primary, than any other moon in the Solar System. Previous searches for other satellites around Pluto have been unsuccessful^{5, 6, 7}, but they were not sensitive to objects 150 km in diameter and there are no fundamental reasons why Pluto should not have more satellites⁶. Here we report the discovery of two additional moons around Pluto, provisionally designated S/2005 P 1 (hereafter P1) and S/2005 P 2 (hereafter P2), which makes Pluto the first Kuiper belt object known to have multiple satellites. These new satellites are much smaller than Charon, with estimates of P1's diameter ranging from 60 km to 165 km, depending on the surface reflectivity; P2 is about 20 per cent smaller than P1. Although definitive orbits cannot be derived, both new satellites appear to be moving in circular orbits in the same orbital plane as Charon, with orbital periods of 38 days (P1) and 25 days (P2).

1. The Johns Hopkins University Applied Physics Laboratory, Space Department, 11100 Johns Hopkins Road, Laurel, Maryland 20723-6099, USA
2. Department of Space Studies, Southwest Research Institute, 1050 Walnut Street, Suite 400, Boulder, Colorado 80302, USA
3. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218, USA
4. Lowell Observatory, 1400 W. Mars Hill Road, Flagstaff, Arizona 86001, USA

Correspondence to: H. A. Weaver¹ Correspondence and requests for materials should be addressed to H.A.W. (Email: hal.weaver@jhuapl.edu).

MORE ARTICLES LIKE THIS

These links to content published by NPG are automatically generated.