![]() ![]() The ALMA astrometry used a bright quasar named J1911-2006 with the goal to cut in half the uncertainty of Pluto’s position, said Ed Fomalont, an astronomer with the National Radio Astronomy Observatory in Charlottesville, Virginia, and currently assigned to ALMAs Operations Support Facility in Chile.ĪLMA was able to study Pluto and its largest moon Charon by picking up the radio emission from their cold surfaces, which are about 43 degrees Kelvin (-230 degrees Celsius). Though quasars appear very dim to optical telescopes, they are incredibly bright at radio wavelengths, particularly the millimeter wavelengths that ALMA can see. The most distant and most apparently stable objects in the Universe are quasars, galaxies more than 10 billion light-years away. For New Horizons, however, even more precise measurements were necessary to ensure its encounter with Pluto would be as on-target as possible. Normally, stars at great distances are used by optical telescopes for astrometry (the positioning of things on the sky) since they change position only slightly over many years. Finding such a reference point to accurately calculate trajectories of such small objects at such vast distances is incredibly challenging. To prepare for this first TCM, astronomers needed to pinpoint Pluto’s position using the most distant and most stable reference points possible. This maneuver helped ensure that New Horizons uses the minimum fuel to reach Pluto, saving as much as possible for a potential extended mission to explore Kuiper Belt objects after the Pluto system flyby is complete. The New Horizons team made use of the ALMA positioning data, together with newly analyzed visible light measurements stretching back to Pluto’s discovery, to determine how to perform the first such scheduled course correction for targeting, known as a Trajectory Correction Maneuver (TCM), in July. With these limited observational data, our knowledge of Plutos position could be wrong by several thousand kilometers, which compromises our ability to calculate efficient targeting maneuvers for the New Horizons spacecraft, said New Horizons Project Scientist Hal Weaver, from the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. Pluto was discovered in 1930 and takes 248 years to complete one revolution around the Sun. This lingering uncertainty is due to Pluto’s extreme distance from the Sun (approximately 40 times farther out than the Earth) and the fact that we have been studying it for only about one-third of its orbit. Though observed for decades with ever-larger optical telescopes on Earth and in space, astronomers are still working out Pluto’s exact position and path around our Solar System. Any changes could affect both the size of the spacecraft and the price tag, estimated to be a whopping $3 billion.Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) are making high-precision measurements of Pluto’s location and orbit around the Sun to help NASAs New Horizons spacecraft accurately home in on its target when it nears Pluto and its five known moons in July 2015. One of the biggest would be maintaining its power source-an array of radioisotope thermoelectric generators, or what amount to nuclear batteries-on such a long journey. “Although we undoubtedly would gain more knowledge by continuing to study the icy Kuiper Belt objects, I think that we stand to gain far more, far quicker if we keep our exploration a bit closer to home,” says Tyler.Īnd as with any mission, there are risks and challenges involved in getting Persephone off the ground. Instead of Pluto, Tyler says, we should go to the moons of Saturn and Jupiter, many of which we already know are home to oceans below their surface. ![]() But because NASA invests only in top science priorities, resources are limited. “In a perfect world we would be constantly putting together new missions to anything we could land a rover on,” says Dakotah Tyler, an astronomy PhD student at UCLA who studies exoplanets (planets orbiting stars other than our sun). ![]()
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