NASA's new NASA horizon mission has not yet discovered any moons around the Ultima Thule facility, but team members are still searching for.
Credit: NASA / University of Applied Physics at Johns Hopkins University / Southwest Research Institute
The farthest celestial object ever explored can have moons, and astronomers try to find them.
In the first hours of January 1, the NASA spacecraft, New Horizons, zoomed in on the last small, frigid object Ultima Thule, which lies more than 4 billion miles (6.4 billion kilometers) from Earth. The probe has so far only a small portion of its flight data, but mission team members are already starting to get the goods on the far rock.
For example, scientists now know that the Ultima Thule with a length of 21 kilometers (33 kilometers) is composed of two roughly spherical lobes, which apparently started their lives as independent free-floating objects. The duo quickly turned closer and closer, joining in the earliest days of the solar system to form a reddish "snowman". [New Horizons at Ultima Thule: Full Coverage]
The modeling work suggests that both constituent bodies, called "Ultima" and "Thule," probably ended a rotation every 3 or 4 hours around the time they were attached, the members of the mission team said. But observations of the New Horizons show that today's Ultima Tule takes about 15 hours to make a full back.
"Well, how do they slow down? Well, the best way to understand this is if there was another moon, or two or three, orbiting this system," Mark Showalter, a co-explorer of New Horizons of SETI (Search for an Extraterrestrial Institute for intelligence) in Mountain View, California, during a press conference Thursday (January 3rd).
"Essentially, what those moons would do is put the brakes of the two bodies in the middle – let's slow them down," by taking the angular impulse of the duo, he added.
So, the search for the satellites of Ultima Tule, which began to work seriously, when the team's mission investigated potential dangers that could complicate the epic New Year's overflow, is difficult.
The mission team rejected the existence of all significant moons at 800 kilometers from Ultima Thule or within 160 kilometers of the facility, said Showalter. But that middle zone is a big questionnaire and will remain so until the end of January, when New Horizons will monitor domestic observations that cover the region.
And, essential, this inter-zone is most likely a place for the existence of satellites in the system, said Showalter.
He and his colleagues hope to become at least one moon because such a discovery will help them to extract key details of Ultima Thule that they will be hard pressed to determine in any other way.
"Every moon in general, in any orbit, will tell us the mass and density of a fairly decent usable precision," said Showalter. "And so we are very, very excited about that perspective."
Even if the search ultimately appeared empty, that does not mean that Ultima Thule – officially known as the 2014 MU69 – never hosted moons, he added. Since satellites are removing the angular impulse from the central bodies of their systems, these moons move further and further into space. So, it is possible that Ultima Thule once had such satellites, but these moons were moving so far that they were eventually lost.
The $ 700-million "New Horizon" mission began in January 2006 with the task of bringing back Pluto's first pictures closely. The mission took this target when it passed through the dwarf planet in July 2015, revealing Pluto as a world of incredible beauty and geological diversity.
The space of Ultima Thule is a central part of the expanded New Horizons mission that lasts until 2021. The spacecraft has enough fuel and power and is healthier enough to potentially fly past the past of the third building, if NASA has assigned another mission, the team members say.
Mike Wall's book for the search for extraterrestrial life "There"(Grand Central Edition, 2018, illustrated by Carl Tate) is now out. Follow it on Twitter @michaeldwall. Follow us @Spacedotcom or Facebook. Originally published on Space.com.