Hubble discovers new moon in our Solar System

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Artist's impression of the newly-discovered moon S/2015 (136472) 1 orbiting the dwarf planet Makemake(Credit: NASA, ESA, and A. Parker (Southwest Research Institute))

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A team of astronomers has announced the discovery of a new moon located in the far reaches of our Solar System, orbiting the little-known dwarf planet Makemake. Tentatively designated S/2015 (136472), or MK 2 for short, this newest addition to our little patch of the Milky Way could shed light on the enigmatic nature of minor planets traversing the Kuiper Belt.

Makemake is one of five officially recognized minor planets such as Pluto that are known to roam the Kuiper Belt. Following its discovery in 2005, a number of attempts have been made to ascertain whether the distant icy body played host to one or more satellite moons, but each bid had came up empty, until now.

MK 2 had been able to exist undiscovered up until now thanks to the surface characteristics of Makemake. Much like Pluto, Makemake is coated in a dense layer of methane ice. The reflective properties of the ice caused the dwarf planet to shine up to 1,300 times brighter than MK 2, essentially cloaking the moon in the glare of the planetoid.

Only with Hubble's high-resolution Wide Field Camera 3 were astronomers finally able to pierce through the interference and discover the elusive moon.

MK 2, which is estimated to boast a diameter of only 100 miles (161 km) across, around nine times smaller than Makemake, was spotted orbiting the dwarf planet at a distance of 13,000 miles (20,921 km). Initial observations suggest that MK 2 traverses a reasonably circular trajectory with a 12-day orbital period. Further analysis of the moon's orbit will be needed to confirm this first impression, and settle the question as to how MK 2 came to settle in orbit around Makemake.

Hubble image of Makemake and MK 2(Credit: NASA, ESA, and A. Parker and M. Buie (SwRI))

Confirmation of a circular orbit would support the theory that, at some point in the last several billion years, MK 2 collided with Makemake and was subsequently drawn in to a stable orbit by the dwarf planet's gravitational pull. Conversely, a more elongated orbit would suggest that MK 2 was captured following a close proximity pass of the planetoid that did not involve a direct collision.

The presence of the moon could also provide an explanation for a previous detection of increased infrared emissions from the planetoid, which had been taken to indicate unexpected warm spots on Makemake's surface. It is now thought that the instruments, which lacked the resolution to identify MK 2 as a separate body, were detecting the black surface of the moon in close proximity to Makemake.

It is thought that unlike the larger planetoid, MK 2's relatively weak gravitational influence was unable to maintain a covering of methane ice, which exposed the moon's charcoal-black surface, and allowed it to become warmed by sunlight.

The discovery of a satellite body orbiting Makemake opens numerous possibilities for further study of the planetoid. Furthermore, the similarities insofar as the methane ice surface and the presence of a satellite moon is helping to create a more detailed model for other Kuiper Belt bodies.

Just as observations of Pluto's moon Charon paved the way for for a more accurate determination of Pluto's mass, the discovery of MK 2 will allow for a more comprehensive characterization of Makemake, including its density and composition.

Scroll down to view a NASA video on the discovery of MK 2.

Source: NASA

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