Next Stop for New Horizons

On January 1, 2019, New Horizons will flyby “the most distant, most primitive object ever explored,” according to Alan Stern of the Southwest Research Institute (SwRI). But beyond that, 2014 MU69 (or just MU69) really isn’t exceptional—“there are hundreds of thousands of objects in the Kuiper Belt that are the same size as MU69,” says SwRI’s John Spencer—but that’s the whole point. When scientists get MU69 observations back from New Horizons, they’ll be able to extrapolate those data to help understand the other hundreds of thousands of its Kuiper Belt neighbors.

Stern, Spencer, and a handful of others shared information about MU69 and the New Horizons mission at the American Geophysical Union fall meeting this week. And they could barely contain their excitement over average MU69. The Kuiper Belt Object (KBO), four billion miles (6.5 million kilometers) from Earth, may not get its moment of glory until early 2019 (through fall of 2020, since it will take that long to transmit all of the data from New Horizons to Earth), but scientists are frantically studying it now.

Mark Buie from the SwRI team described how this past summer, the team gained a lot of information about the tiny object through occultations. MU69, likely no larger than 20 miles (30 kilometers) in length or diameter, passed in front of three different stars in June and July, allowing telescopes here on (or just above) Earth to gather more information about the KBO. The first occultation, in June, registered nothing. The second on July 10, observed from NASA’s Stratospheric Observatory for Infrared Astronomy (a.k.a. SOFIA, and you can learn more about SOFIA and occultations in this video we produced recently), only registered one small blip, and not quite at the target location the team was expecting. And on July 17, five telescopes in Argentina recorded the final occultation, providing information on MU69’s size and shape.

Observations during the last occultation raised the possibility that MU69 might be two binary objects, or a single body resembling something like a snowman—with one body on top of the other. And now, the team reports, the blip discovered during the SOFIA observation could point to a moon. A binary with a moon, perhaps! “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.”

So now we wait. Well, not exactly. Since its flyby of Pluto two and a half years ago, New Horizons has been heading toward MU69, which is no small task. The two are as far apart as Saturn is from the Sun! Alice Bowman, the New Horizons Mission Operations Manager, described how the spacecraft will soon go into hibernation, waking up in June and going into a mode in mid-August where it can start collecting data about other KBOs it spies—from a bit of a distance, yes, but still closer than anything else out there. In September 2018, the team should have more information, provided by the Hubble Space Telescope, of MU69’s location. They can then start diverting the spacecraft from mid-September through mid-December to get it on target for the 12:33 a.m. Eastern January 1, 2019, flyby.

MU69 will likely be New Horizons’s last flyby, Spencer added. The spacecraft is very low on fuel and the data transmission will take another year and a half. But the small, average, and special KBO will give us so much information about its kind, it will fill in our knowledge about our farthest neighbors in the Kuiper Belt.