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Tracking icy objects, across the globe

Pilot project sets the stage for MIT-led globe-girdling efforts to learn about icy relics of the solar system's birth.
Diagram showing the predicted track of the occultation of a star by a Kuiper Belt Object on the night of Oct. 9.
Diagram showing the predicted track of the occultation of a star by a Kuiper Belt Object on the night of Oct. 9.
Diagram: Carlos Zuluaga; courtesy of the Planetary Astronomy Lab

On any given night, numerous icy bodies orbiting the sun far beyond the orbit of Pluto may happen to pass in front of a star (as seen from Earth). These events are called occultations, but because the icy moon-sized globes called Kuiper Belt Objects are so small, and their orbits not very accurately known, the vast majority of these events will go unobserved.

That's too bad, because there's a lot to be learned by watching occultations: It's a way to learn the exact size of the object, to discover whether it's actually a pair of objects or is accompanied by one or more moons, and whether or not it has an atmosphere. These questions bear directly on our understanding of the origins of our solar system, because Kuiper Belt Object — in a belt of tens of thousands of icy worlds that includes the former planet Pluto — are thought to be the nearly unchanged remnants of the small bodies called planetesimals that slammed together more than 4 billion years ago to form the planets themselves.

Now, an MIT-led group is aiming to pin down predictions of occultations so that they can be observed systematically by teams of observers scattered across the globe. Multiple observations are essential: they allow for the collection of as much data as possible from these events.

The group's first full-scale test of its system took place Thursday night, with at least 25 observing teams all the way from Australia and New Zealand, through Hawaii, and into the continental United States. The teams include both professional and experienced amateur astronomers, as well as at least one MIT graduate students.

James Elliot, a professor in the Department of Earth, Atmospheric and Planetary Sciences, is leading the project, and was due to discuss it and first-look results from Thursday night's observations on Friday at the annual meeting of the American Astronomical Society's Division for Planetary Sciences, being held in Puerto Rico.

Ultimately, the team hopes to be able to produce occultation predictions accurate enough to guide observations by NASA's new airplane-mounted telescope, called Sofia, which is expected to begin scientific work early next year. Thursday's observations were a kind of test case, Elliott says, because "with Sofia, it's going to be such a production, it would be very costly to get it wrong. This will test our ability to get it right."

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