On New Year’s Eve Hawaii Time, the NASA New Horizons spacecraft will pass by an object known as 2014 MU69, nicknamed Ultima Thule. The name Ultima Thule comes from Greek and Roman literature and map-making meaning “the farthermost northern place, almost mythical in its existence.” It’s an appropriate nickname for the object, as the flyby of MU69 is the farthest planetary flyby in history.
The New Horizons mission rocketed to fame in July of 2015 when it passed by Pluto. The flyby gave us the best images of Pluto to data and showed everyone the dwarf planet’s “heart,” a feature on Pluto’s surface that became the arguably the most famous image of Pluto.
After the Pluto flyby, the New Horizons team received a mission extension to continue studying the outer solar system through 2021. The team began the search for potential new targets for New Horizons, which utilized many of the telescopes in the world, including the biggest cameras on Maunakea at the Canada-France-Hawaii (CFHT) and Subaru Telescopes.
As science would have it, astronomers used CFHT to conduct a survey of the outer solar system called Canada-France Ecliptic Plane Survey (CFEPS). CFEPS, started in 2003, provided the very first detailed map of the outer solar system. Two of the astronomers leading the survey, JJ Kavelaars from Canada and Jean-Marc Petit from France, used the CFEPS map to determine which part of the sky was most likely to contain an object that met New Horizons’ criteria.
In 2014, the Hubble Space Telescope turned towards the CFEPS field and discovered 2014 MU69. MU69 is very faint, very small – only 18 miles in diameter (for reference Waimea to Paauilo is about 21 miles) and 3.7 billion miles away from the Earth. Only the Hubble Space Telescope could find the object, but they would not have known where to look without the CFHT data.
Finding MU69 was hard, getting there took very careful planning and an another excellent map. Once New Horizons passed by Pluto, the spacecraft had to make an early and precise change of course to reach MU69.
While Hubble is an excellent telescope, it is hard to determine exactly where Hubble is pointing to the level of precision needed for the course correction. Using CFHT data, another Canadian astronomer, Stephen Gwyn, produced a catalog of stars. In Gwyn’s catalog, the position of the stars is known to 20 milliarcseconds, or roughly the diameter of FDR’s eye on a dime at a distance of a half mile away. Needless to say, it’s an incredible map. Gwyn’s precise stellar map was used to calibrate the Hubble image, which allowed the New Horizons’ team to calculate the exact orbit of MU69. Once they had MU69’s orbit, the team changed the path of New Horizons.
Astronomers, known as the New Horizons hazard watch team, used the probe’s own camera to look for potential hazards orbiting the object. New Horizons is traveling at 31,500 mph. At that speed, even a piece of dust the size of a rice grain can cause catastrophic problem to the piano sized New Horizons probe.
Earlier this month, New Horizons was given the go ahead to stay on its path to MU69. The probe will pass 2,200 miles away from the surface of MU69 at 7:33 p.m. HST on Dec. 31. Representatives from CFHT will be on hand for the flyby at the New Horizons’ Mission Control at the Johns Hopkins University Applied Physics Lab in Laurel Maryland.
Not feeling the name MU69 or Ultima Thule? It will receive an official name after the fly-by.