Nearly two decades ago, a near-Earth asteroid was discovered to have a moon, and the binary system was given the name “Didymos,” which in Greek means “twin,” a loose description of the largest main body and the moon. in smaller orbit, which became unofficially known as Didymos B.
In 2022, that moon will be the target of POTThe Double Asteroid Redirection Test (DART), the first large-scale demonstration of an asteroid deflection technology for planetary defense. The DART spacecraft will execute a kinetic impactDeliberately crashing into the asteroid to change its motion in space. To mark this historic mission, Didymos B is receiving an official name of its own: Dimorphos.
“Upon discovery, asteroids get a temporary name until we know their orbits well enough to know that they will not be lost. Once the Didymos system was identified as the ideal target for the DART mission, we had to formally distinguish between the main body and the satellite, “said Andy Rivkin, research astronomer and co-director of DART research at the Johns Hopkins Laboratory of Applied Physics (APL), which is building and managing the mission for NASA.
A global effort
Just as defending our planet from potentially dangerous asteroids requires a global effort, so does naming an asteroid’s moon.
In 2003, the astronomer Petr Pravec, at the Ondřejov Observatory in the Czech Republic, was tracking the brightness of a still-nameless asteroid when he recognized a pattern consistent with a small moon. Across the world, planetary scientists Lance Benner, at NASA’s Jet Propulsion Laboratory in Pasadena, California, and Mike Nolan, then at the Arecibo Observatory in Puerto Rico, gathered corroborating evidence. Together, the findings pointed to the existence of a binary asteroid.
The near-Earth asteroid was originally discovered in 1996 by Joe Montani of the Spacewatch Project at the University of Arizona, but its orbit needed to be confirmed before it could be named. Backed by the work of Pravec, Benner, Nolan and other astronomers, Montani suggested “Didymos” to the International Astronomical Union (IAU), which he quickly approved.
After Didymos B was identified as the DART target, mission leaders in APL encouraged discoverers to come up with a separate name for the system’s moon. Weighing many possibilities, they finally came with a suggestion from Kleomenis Tsiganis, a planetary scientist at Aristotle University of Thessaloniki and a member of the DART team. This week, the IAU announced the official approval of the name.
“Dimorphos, which means ‘two shapes’, reflects the status of this object as the first celestial body to have the ‘shape’ of its orbit significantly changed by humanity, in this case, by the impact of DART,” he said. Tsiganis. As such, it will be the first object known to humans in two very different ways, the one seen by DART before impact and the other seen by Hera from the European Space Agency (ESA) a few years later. “
Measuring 525 feet (160 meters) in diameter, Dimorphos is the perfect target for the DART test because of its orbit around the larger main body Didymos (measuring 780 meters, or 0.48 miles, in diameter), and because the pair is relatively very close to Earth in late 2022.
“Astronomers will be able to compare observations of ground-based telescopes before and after DART’s kinetic impact to determine how much Dimorphos’s orbital period changed,” said Tom Statler, a DART program scientist at NASA headquarters. “That is the key measure that will tell us how the asteroid responded to our diversion effort.”
DART’s impact with Dimorphos will also be recorded in space by LICIACube, a CubeSat companion provided by the Italian Space Agency that will travel to and deploy from DART. ESA’s Hera mission will conduct additional investigation of Didymos and Dimorphos a few years after the DART impact. The DART and Hera mission teams are working together through an international collaboration called Asteroid Impact and Diversion Assessment (AIDA).
“DART is a first step in testing methods for the diversion of dangerous asteroids,” said Andrea Riley, DART Program Executive at NASA headquarters. “Potentially dangerous asteroids are a global concern, and we are excited to work with our Italian and European colleagues to collect the most accurate data possible from this kinetic impact deflection demonstration.”
DART is the first mission developed for NASA’s Planetary Defense Coordination Office, and a piece of NASA’s broader planetary defense planning. In 2016, NASA established the Planetary Defense Coordination Office (PDCO) to lead the efforts of the US Government. USA To detect and warn of potentially dangerous comets and asteroids and to study ways to mitigate the danger when possible.
From Didymos B to Dimorphos, it is a fitting name for an asteroid that will fulfill dual roles as a test target and as part of a plan to protect the planet in the future.