After scouring through Hubble images of one of the most extreme worlds in the badlands of our outer solar system, a small and very, very dark moon has been discovered.
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Makemake orbits the sun at an average distance of around 45 AU (astronomical units, where 1 AU is the average distance the Earth orbits the sun), so to zoom in on its location, the most powerful space telescope was needed to understand more of its nature. Hubble uncovered the landmark find in April, but before then, there was little evidence that Makemake possessed its own natural satellite and if it didn't have a moon, astronomers wanted to understand why. But that changed when observations by Hubble's Wide Field Camera 3 were analyzed and an extremely dark moon emerged as a faint point of light very close to the dwarf planet. The Kuiper belt object (KBO) was discovered in 2005 by a Caltech team led by astronomer Mike Brown.
"Makemake's moon proves that there are still wild things waiting to be discovered, even in places people have already looked," said astronomer Alex Parker, of the Southwest Research Institute (SwRI), who is credited with the discovery of the moon. "Makemake's moon -- nicknamed MK2 -- is very dark, 1,300 times fainter than the dwarf planet."
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Parker's research has now been published in the June 27 issue of Astrophysical Journal Letters.
It turns out that MK2 has an almost perfectly edge-on orbit from our perspective, ensuring that, for most of its short orbit that it remained hidden in the bright glare of Makemake's bright reflected light. Understanding why MK2 is so dark is a puzzle and will undoubtedly be the focus of future research.
Known to posses a shell of methane ice, Makemake measures around 870 miles across. It is estimated that MK2 is approximately 100 miles wide.
"With a moon, we can calculate Makemake's mass and density," said Parker. "We can contrast the orbits and properties of the parent dwarf and its moon, to understand the origin and history of the system. We can compare Makemake and its moon to other systems, and broaden our understanding of the processes that shaped the evolution of our solar system."
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The Kuiper belt is often viewed as the "blood spatter" of the solar system where shards of broken planets slowly orbit the sun, frozen in time. As we discover more objects in our sun's hinterland, we find more clues as to how the early planets formed and gain an insight to the dynamical chaos that rumbled the outer solar system billions of years ago.
So when a moon is discovered around a dwarf planet so far from the sun, we can measure its orbit to great precision, revealing the mass of the world and moon, and therefore derive a density that, in turn, can reveal its composition. Any world's composition provides an open book to its history and, int he case of Makemake, may help us better understand what powerful collision possibly shaped this unique little world.
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Source: SwRI