Free Astronomy Magazine September-October 2019

51 SEPTEMBER-OCTOBER 2019 SPACE CHRONICLES we felt that all the pain, all the ef- forts were worth it.” Mathias Jones, another VLT astron- omer involved in these observations, elaborated on the difficulties. “Dur- ing the observations the atmospheric conditions were a bit unstable. In addition, the asteroid was relatively faint and moving very fast in the sky, making these observations particu- larly challenging, and causing the AO system to crash several times. It was great to see our hard work pay off despite the difficulties!” While 1999 KW 4 is not an impact threat, it bears a striking resem- blance to another binary asteroid system called Didymos which could pose a threat to Earth sometime in the distant future. Didymos and its companion called “Didymoon” are the target of a future pioneering planetary defence experiment. NASA’s DART spacecraft will impact Didymoon in an attempt to change its orbit around its larger twin, in a test of the feasibility of deflecting asteroids. After the impact, ESA’s Hera mission will survey the Didymos as- teroids in 2026 to gather key information, including Didymoon’s mass, its sur- face properties and the shape of the DART crater. The success of such mis- sions depends on collabo- rations between organisa- tions, and tracking Near- Earth Objects is a major focus for the collaboration between ESO and ESA. This cooperative effort has been ongoing since their first successful tracking of a potentially hazardous NEO in early 2014. “We are delighted to be play- ing a role in keeping Earth safe from asteroids,” said Xavier Bar- cons, ESO’s Director General. “As well as employing the sophisticated capabilities of the VLT, we are work- ing with ESA to create prototypes for a large network to take asteroid detection, tracking and characteri- zation to the next level.” ! T his info- graphic shows the minimum dis- tance between the asteroid 1999 KW 4 an Earth — the closest the as- teroid comes to our planet during its fly- by. [ESO] Taking a break from its usual night job hunting exoplanets, SPHERE data helped astronomers charac- terise the double asteroid. In partic- ular, it is now possible to measure whether the smaller satellite has the same composition as the larger ob- ject. “These data, combined with all those that are obtained on other tel- escopes through the IAWN cam- paign, will be essential for evaluating effective deflec- tion strategies in the event that an asteroid was found to be on a collision course with Earth,” explained ESO astronomer Olivier Hain- aut. “In the worst possible case, this knowledge is also essential to predict how an asteroid could interact with the atmosphere and Earth’s surface, allowing us to mitigate damage in the event of a collision.” “The double asteroid was hurtling by the Earth at more than 70000 km/h, making observing it with the VLT challenging,” said Diego Parraguez, who was piloting the tel- escope. He had to use all his expert- ise to lock on to the fast asteroid and capture it with SPHERE. Bin Yang, VLT astronomer, declared “When we saw the satellite in the AO-corrected images, we were ex- tremely thrilled. At that moment, T his artist’s impression shows both components of the double asteroid 1999 KW 4 tumbling through space dur- ing its Earth fly-by. [ESO/M. Kornmesser]