Hubble Space Telescope discovers a moon orbiting the Dwarf Planet Makemake.

Makemake is the largest known body in the Kuiper Belt and the second-brightest Trans-Neptunian Object (after Pluto). It has a very bright albedo (it reflects a lot of light), with a surface apparently covered by methane ice, and is known to rotate on its access every 7.771 hours. However much less is known about the mass and density of Makemake than the other two largest Kuiper Belt Objects, Pluto and Eris, as in the case of these objects satellites have been discovered, the orbital properties of which have helped astronomers to understand the parent bodies.

In a paper published on the online arXiv database at Cornell University Library on 25 April 2016, Alex Parker and Marc Buie of the Southwest Research Institute, Will Grundy of the Lowel Observatory and Keith Noll of NASA's Goddard Space Flight Center announce the discovery of a moon orbiting Makemake by the Hubble Space Telescope.

The moon was detected in two sets of images, take on 1 & 29 April 2015 with the Hubble Space Telescope's Wide-Field Camera 3, with the change in relative position between Earth and Makemake between these dates sufficient to make it extremely unlikely that the object is unrelated to the Dwarf Planet. Since Makemake has previously been imaged by Hubble instruments capable of spotting such an object, it is thought that the moon must be in an orbit edge on to the telescope, so that it is hidden by the brightness of the planet much of the time.

The new moon is provisionally named S/2015 (136472) 1, where 'S' indicates the body is a satellite, '2015' is the year of the discovery, '136472' refers to Makemake (the 136 472nd minor planet discovered) and '1' indicates the first such satellite of Makemake discovered in 2015.

Left panels: Co-registered stack of all visit 1 images (top) and visit 2 images (bottom). Images are displayed in their original array coordinates with identical stretch to best compare PSF structure. Right: WCS-rotated stack of visit 1 images with co-registered visit 2 images subtracted, showing S/2015 (136472) 1. Stack is 33rd percentile of six input images. Arrows indicate 100in Ecliptic North and East for each visit; white for visit 1 and green for visit 2. Green trace indicates masked region where S/2015 (136472) 1 would not have been recoverable in visit 2 as determined by injecting synthetic sources. White cross indicates centroid of Makemake. Parker et al. (2016).

S/2015 (136472) 1 is estimated to have an average orbital distance of between 21 100 and 300  000 km, and an orbital period of between 12.4 and 660 days and to have an orbit with an inclination between 63° and 87° to the Makemake equator and between 83° and 105° to the plane of the Solar System. This would result in the moon being visible to the Hubble Space Telescope between 50% and 90% of the time.

See also...

Sputnik Planum: An apparently young feature on the surface of Pluto.                                 Pluto was the first known and is one of the largest bodies in the Kuiper Belt, a field of Dwarf Planets and smaller bodies beyond Neptune which are thought to have been beyond the zone of true-planet formation, and therefore to reflect the nature of the early Solar System. In July 2015 the New Horizons spacecraft flew past Pluto, making a detailed survey of the surface...

Deciphering the rings of 10199 Chariklo. 10199 Chariklo is a Centuar (asteroid or comet-like body found between the orbits of Jupiter and Neptune), which was first discovered in 1997 and subsequently found to be the largest such body, with an...

 

Assessing the composition of ices on the surface of Makemake.                                  The Dwarf Planet Makemake is one of the three largest Trans-Neptunian Objects, with a diameter of about 1400 km, along with Pluto and Eris (2370 km 2330 km respectively). Makemake is thought to have a...

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