A Hidden Moon For A Distant Mini-World?



A Hidden Moon For A Distant Mini-World?
By Judith E Braffman-Miller

Ah, but a man’s reach should exceed his grasp,

or, what’s a heaven for?

“Andrea del Sarto”, Robert Browning

We are an inquisitive species. For all of our human flaws, one of our more admirable traits is our need to explore–to go where no one has ever gone before, to see what no one has ever seen before. This distant hum of singing Sirens perpetually haunts our dreams, tantalizing our imaginations, luring us into regions of distant, frigid darkness–far, far away. NASA’s New Horizons spacecraft has now left Pluto and its quintet of moons behind, and is well on its way to explore more distant regions of the Kuiper Belt, where a vast multitude of icy worldlets swim in a mysterious sea of everlasting twilight. In August 2015, a Kuiper Belt Object (KBO), with the lengthy name of (486958) 2014 MU69, was chosen as New Horizons’ next target of exploration–and this enchanting little world, that does its mesmerizing dance in our Solar System’s frigid Twilight Zone, is now whispering to us some of its well-kept secrets. 2014 MU69 may have a hidden moon all its own!

Astronomers are already anticipating that something exciting will be revealed to them when New Horizons finally reaches little 2014 MU69 in 2019, after sailing through the darkness of our Solar System’s most remote region of ice–that has, up until now, been entirely unexplored. This little KBO twirls around our Star a billion miles past Pluto–and it could possibly be shaped like a peanut or–alternatively–it could really be a duo of objects orbiting around one another (binary). Now, more recent data hints that another possibility might explain some of 2014 MU69’s newly-observed odd attributes. It may have company.

The KBO’s company, according to the latest theory–coming courtesy of NASA’s New Horizons spacecraft–is a tiny, frigid, and very well-hidden moon, that is enshrouded in the distant darkness of interplanetary space, far from the light and heat of our Sun. Meanwhile, New Horizons continues to explore, and then analyze, telescope data that it is gathering about this icy target of its planned New Year’s Day 2019 flyby. “We really won’t know what MU69 looks like until we fly past it, or even gain a full understanding of it until after the encounter. But even from afar, the more we examine it, the more interesting and amazing this little world becomes,” commented Dr. Marc Buie in a December 11, 2017 Johns Hopkins University: Pluto Press Release. Dr. Buie, of the Southwest Research Institute in Boulder, Colorado, presented this updated analysis at the American Geophysical Union’s (AGU’s) Fall 2017 held in New Orleans.

2014 MU69 was discovered by astronomers using the Hubble Space Telescope (HST) on June 26, 2014. This irregularly shaped distant denizen of our Solar System’s dark deep freeze is a classical KBO that has previously been suspected of being a contact binary, or even a close binary system. It measures approximately 30 kilometers in diameter.

NASA’s New Horizons spacecraft was launched on January 19, 2006, with the original goal of exploring the distant Pluto system.

Shortly after it had finished its rendezvous with Pluto and its moons, 2014 MU69 was chosen to be the next object visited by this very plucky traveling spacecraft. The flyby is expected to occur on January 1, 2019, which will make 2014 MU69 the most ancient object in our Solar System to be visited by a spacecraft. After a quartet of course changes in October and November 2015, New Horizons is now swiftly en route to 2014 MU69.

2014 MU69

When 2014 MU69 was first discovered, it was given the designation of 1110113Y–nicknamed “11”, for short. Its potential as the next target for the New Horizon probe was announced by NASA in October 2014. At this time it was unofficially referred to as “Potential Target 1” (PT1). The KBO’s official name, 2014 MU69, was assigned to it by the Minor Planet Center (MPC) in March 2015. When additional observations were conducted to precisely determine its distant orbit, 2014 MU69 was officially given the minor planet number of 486958 on March 12, 2017.

The provisional designation of 2014 MU69 shows that it was the 1745th object discovered during the latter half of June 2014. After New Horizons’ upcoming future flyby, when its true character is at last revealed, it will be given a proper name.

Observations conducted in 2017 concluded that 2014 MU69 is no larger than 20 miles in length–and extremely elongated. Because of this, many astronomers think that it may be a duo of closely knit KBOs in orbit around each other. Indeed, in an occultation on July 17, 2017, a two-lobe shape was detected, with diameters of 12 to 11 miles, respectively. This indicates the possibility that 2014 MU69 is a primordial binary, inhabiting the distant deep freeze of our Solar System–an ancient denizen of the dimly-lit Kuiper Belt. These orbital attributes tell scientists that 2014 MU69 is a classical cold KBO that probably has not experienced large disruptive perturbations. Observations conducted in May and July 2015 and October 2016 successfully reduced the number of unknowns concerning the orbit of this small world. The most recent orbit parameters can be found on the MPC’s database.

Having now completed its observations of Pluto and its five frigid moons, the New Horizons spacecraft has been maneuvered for a flyby of 2014 MU69. New Horizons’ closest approach will occur on January 1, 2019, at which point it will be about 43.4 astronomical units (AU) from our Star in the constellation Sagittarius. One AU is equal to the average distance between our planet and the Sun, which is about 93,000,000 miles. At this incredible distance, the one-way duration for radio signals to be transmitted from New Horizons to Earth will be six hours. The first pictures, courtesy of New Horizons, are to be taken on December 28, 2018, three days before the historic flyby. If problems arise, New Horizons may postpone its rendezvous with this puzzling KBO.

2014 MU69 has the distinction of being the first object to be targeted for a flyby that was discovered after a spacecraft was launched. The New Horizons spacecraft is currently planned to fly within 2,200 miles of its icy quarry–three times closer than the spacecraft’s earlier encounter with Pluto. Pictures with a resolution of up to 98 feet are anticipated.

The science of the flyby include characterizing the geology and morphology of 2014 MU69, mapping the surface conditions (looking for methane, carbon monoxide, ammonia, and water ice). The search will be conducted for a coma, rings, surrounding environment–and, of course, the possible presence of a moonlet.

A moon is defined as a natural satellite in orbit around another body that, in turn, circles a Star. The moon is kept in place both by its host’s gravitational grip, as well as by the tug of its own gravity. Some planets are orbited by moons; some are not. Several asteroids possess small moons, and some dwarf planets–such as Pluto–are also circled by moons. Pluto’s largest moon, Charon, is about half the size of Pluto, and is thought to be a chunk of Pluto itself, that was blasted off as the result of a catastrophic collision with another ill-fated body approximately 4.5 billion years ago. Because Charon is about 50% the size of Pluto, some astronomers categorize the distant duo as a “double planet”.

There are more than 100 moons orbiting the eight major planets of our Solar System. Most of these moons are small, icy worldlets, containing a relatively small amount of rocky material, in orbit around the quartet of giant, gaseous planets in our Solar System’s outer realm–far from the brilliant light and heat of our Star. The four giant planetary inhabitants of our Solar System’s outer limits–Jupiter,Saturn, Uranus, and Neptune–are cloaked within heavy, dense blankets of gas, and are circled by a multitude of dancing moons and moonlets. In contrast, the inner region of our Solar System is almost devoid of moons. Of the quartet of rocky, relatively small, and solid terrestrial planets–Mercury, Venus, Earth, and Mars–Mercury and Venus are moonless, and Mars is orbited by two misshapen little moons dubbed Phobos and Deimos. The potato-shaped little Martian moons are considered to be asteroids that were rudely evicted from the Main Asteroid Belt that is located between Mars and Jupiter. During their travels, the two asteroids were snared by the gravitational grip of the Red Planet–thus becoming Martian moons. Earth’s own bewitching, bequiling Moon is the only large moon inhabiting the inner Solar Sysem.

A Hidden Moon For A Distant Mini-World?

The data that led New Horizons astronomers to consider the possibility that 2014 MU69 has a moon of its own, were collected over six weeks in June and July 2017, when the team made three attempts to place telescopes in the narrow shadow of 2014 MU69 as it floated in front of a glaring star. The most important discovery came on July 17, 2017, when five telescopes deployed by the New Horizons team in Argentina, were in the right place at the right time. Because of this stroke of good luck, the astronomers were able to catch the fleeting shadow–known as an occultation–and collect valuable data on 2014 MU69’s shape, size, and orbit. That data obtained suggested that the KBO might really be a duo of similarly-sized objects–or what’s termed a binary.

The suspicion that 2014 MU69 might have a moon of its own was based on data obtained during a different occultation that occurred on July 10, 2017, by NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA). This airborne observatory focused its eye in the sky on 2014 MU69’s predicted location, while it was soaring over the Pacific Ocean. SOFIA detected what appeared to be a very brief dip in the star’s light. Dr. Buie noted in the December 11, 2017 Johns Hopkins University Press Release that additional analysis of that data, including syncing it with 2014 MU69 orbit calculation, that had been provided by the European Space Agency’s (ESA’s) Gaia mission, presented the possibility that the “blip” SOFIA had spotted could really be another object orbiting around the targeted KBO.

“A binary with a smaller moon might also help explain the shifts we see in the position of MU69 during these various occultations. It’s all very suggestive, but another step in our work to get a clear picture of MU69 before New Horizons flies by, just over a year from now,” Dr. Buie continued to explain.

The historic flyby will be the most distant to date in the history of space exploration. The primordial 2014 MU69, discovered in 2014, is more than 1 billion miles from our planet. It appears to be a mere 20 miles long, or, if it is a binary, each approximately 9 to 12 miles in diameter. In a way that is similar to other objects dancing around in the distant Kuiper Belt, 2014 MU69 provides an up-close and personal peek at relics of the ancient planet-building era in our Solar System’s past. KBOs contain important clues about how the outer region of our Solar System formed billions of years ago. This is because they have been preserved in a kind of murky deep-freeze, and are believed to be the frozen left-overs of the ancient bodies that built up the quartet of giant, gaseous outer planets–the icy planetesimals–that hold in their frigid hearts the well-kept secrets of their primeval kind.

New Horizons Principal Investigator Dr. Alan Stern, who is also of the Southwest Research Institute, commented in the December 11, 2017 Johns Hopkins University Press Release that “The occultation effort that Marc Buie and his team led for New Horizons has been invaluable in opening our eyes to the very real possibilities that MU69 is both a lot more complex than anyone suspected, and that it holds many surprises for us at flyby on New Year’s Eve and New Year’s Day 2019. The allure of its exploration is becoming stronger and stronger as we learn more and more about it. It’s just fantastic!”

Judith E. Braffman-Miller is a writer and astronomer whose articles have been published since 1981 in various journals, newspapers, and magazines. Although she has written on a variety of topics, she particularly loves writing about astronomy because it gives her the opportunity to communicate to others the many wonders of her field. Her first book, “Wisps, Ashes, and Smoke” will be published soon.

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