An elongated comet or two space rocks close together should show repeated pulsations in brightness known as a light curve. Instead, New Horizons hasn’t been able to pick up any light curve at all.
“It’s really a puzzle,” said New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute, in a statement. “I call this Ultima’s first puzzle – why does it have such a tiny light curve that we can’t even detect it? I expect the detailed flyby images coming soon to give us many more mysteries, but I did not expect this, and so soon.”
Marc Buie, also of the Southwest Research Institute, suggests that the mystery could be due to Ultima’s rotation with respect to the spacecraft. In other words, New Horizons is at just the wrong angle to see the light. But there are other theories.
“Another explanation,” said the SETI Institute’s Mark Showalter, “is that Ultima may be surrounded by a cloud of dust that obscures its light curve, much the way a comet’s coma often overwhelms the light reflected by its central nucleus.”
It’s a good theory, but such a coma would require some sort of heat-source to generate and the Sun is much too far away to be doing the job.
“An even more bizarre scenario is one in which Ultima is surrounded by many tiny tumbling moons,” said University of Virginia’s Anne Verbiscer, a New Horizons assistant project scientist. “If each moon has its own light curve, then together they could create a jumbled superposition of light curves that make it look to New Horizons like Ultima has a small light curve.”
That explanation would be really interesting, because no bodies in our own solar system match that scenario. Only New Horizons can find out who’s right, or if something even more bizarre is going on.
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NASA’s New Horizons spacecraft is preparing to strike its next target in the Kuiper Belt on New Year’s Day– the enigmatic Ultima Thule.
The probe is intending to swoop over the strangely-shaped things on New Year’s Eve and New Year’s Day, sending out the very first high-res images back to Earth simply a day later on.
In preparation, New Horizons has actually invested the last 3 months taking numerous pictures of Ultima’s brightness, determining how it alters as the things turns, in the hopes of finding out its shape. Researchers had actually currently puzzled out that Ultima isn’t a sphere, it’s either a lengthened area rock or perhaps even 2 things lose together. However inexplicably, New Horizons’ observations up until now aren’t backing that up.