Researchers Puzzled By Lack Of Light Curve From New Horizon’s Flyby Target

Posted: Dec 29 2018, 1:37pm CST | by , Updated: Dec 29 2018, 1:40pm CST, in Latest Science News


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Researchers Puzzled by Lack of Light Curve from New Horizon’s Flyby Target
Ultima Thule passed in front of a star on July 17, 2017. Credit: NASA/JHUAPL/SwRI

At more than 4 billion miles from Earth, Ultima Thule will be the most distant object ever explored by a spacecraft.

NASA’s New Horizons spacecraft is hurtling toward a historic New Year's Day flyby of the most distant object ever explored. The ancient Kuiper Belt object (KBO) 2014 MU69, also known as Ultima Thule, lies more than four billion miles from Earth. On Jan. 1, 2019, New Horizons will make a close encounter with this frozen relic of the early solar system, but the distant object is already revealing some surprises.

Over the past three months, New Horizons’ team has captured hundreds of images to assess size, shape, environment and other conditions around MU69 and is able to gather some critical encounter-planning information. Based on the previous occultation observations, team members already know that MU69 may not be a spherical object. Instead, it might be elongated or even two objects orbiting one another. But researchers have not detected the repeated dips in brightness that they'd expect from a rotating object of that shape. The periodic changes in brightness during every rotation usually produce a phenomenon called light curve.

"It's really a puzzle," said New Horizons Principal Investigator Alan Stern from the Southwest Research Institute. "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."

Researchers have also provided many explanations for this puzzling behavior.

"It's possible that Ultima's rotation pole is aimed right at or close to the spacecraft.” Marc Buie from the Southwest Research Institute said.

The idea sounds logical, but requires further data to determine if this scenario could explain the object’s strange behavior.

"Another explanation 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.” SETI Institute's Mark Showalter said.

An even extreme scenario is that Ultima is surrounded by many tiny tumbling moons. Together, these moons make it look like the object has a small light curve.

“It's hard to say which of these ideas is right," said Stern. "Perhaps its even something we haven't even thought of. In any case, we'll get to the bottom of this puzzle soon – New Horizons will swoop over Ultima and take high-resolution images on Dec. 31 and Jan. 1, and the first of those images will be available on Earth just a day later. When we see those high—resolution images, we'll know the answer to Ultima's vexing, first puzzle. Stay tuned!"

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<a href="/latest_stories/all/all/47" rel="author">Hira Bashir</a>
The latest discoveries in science are the passion of Hira Bashir (). With years of experience, she is able to spot the most interesting new achievements of scientists around the world and cover them in easy to understand reporting.




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