College News

Professor Bill Keel discusses the most recent findings from NASA’s New Horizons mission

From the August 2015 Desktop News | The groundbreaking space probe New Horizons has given astronomers a sharp new eye on one of the most remote bodies in our solar system, Pluto. This new source of information hasn’t gone unnoticed in the College’s Department of Physics and Astronomy, with many astronomers interested in understanding the distant dwarf planet and its peculiarities.

“In our survey classes, Pluto is more than a blank placeholder — we now know about its history as a world,” said Dr. Bill Keel, a professor in the Department of Physics and Astronomy.

Astronomers at UA deal with celestial bodies far more distant than Pluto, often requiring the use of space-based telescopes to properly observe the foci of their research. They use the Hubble Space Telescope, Voyager 2 and Chandra X-ray Observatory to view distant galaxies through a dozen different slices of the electromagnetic spectrum. The New Horizons probe is equipped with instruments that investigate Pluto in the infrared, ultraviolet and visible light spectrums.

“Infrared is especially good for diagnosing molecular solids on the surface, such as methane and water ice, and the UV is particularly powerful for tracing the kinds of atoms in Pluto’s thin atmosphere,” Keel said. “These are fairly standard astronomical techniques, but the application is a lot closer than we’re used to.”

The time necessary to receive data from New Horizon gives observers a sense of the great distance to Pluto.  New Horizons is gathering data much faster than it can travel back to Earth. The communications array sends back about a kilobit per second, approximately 1/50th the speed of a dial-up Internet connection. There is also a delay of about 4.5 hours between data transmission and reception because of the limitations of the speed of light.

“At this distance, it will take over a year to send the full uncompressed data set back, so we expect new result to come in for a long time,” Keel said.

So far, the data that has come back is extraordinary. In addition to popular pictures, New Horizons has observed that Pluto and its largest moon, Charon, are warm inside, with no immediately observable explanation. The dwarf planet has defied expectations in other ways as well.

“Most people expected to see a surface more dominated by impact craters, the telltale sign that nothing else much has happened for billions of years. Not so for Pluto and its largest moon,” Keel said. “This is the first time we’ve seen a world come into view like this since Voyager 2 passed Neptune and Triton in 1989, and the first close-up we’ve had of what we now know to be thousands of icy objects in the outer solar system.”