Free Astronomy Magazine November-December 2022

NOVEMBER-DECEMBER 2022 V iews of the Didymos and Dimorphos binary asteroid system obtained from facilities at NASA Jet Propulsion Laboratory’s Goldstone planetary radar in California and the Na- tional Science Foundation’s Green Bank Observatory in West Virginia. Shown at left are Oct. 4, 2022, observa- tions from Goldstone; at right are combined Gold- stone and Green Bank ob- servations from Oct. 9, 2022. The vertical axis shows radar range (distance from Earth) and the horizontal axis shows the Doppler effect (line of sight velocity). The final slide in the movie shows the difference be- tween where Dimorphos is observed compared to where it would have been with the original orbit. The object appears above (left image) and below in the orbit, consistent with the new 11 h 32 m orbital period, thus confirming the photometric result. [NASA/Johns Hopkins APL/JPL/ NASA − JPL Goldstone Planetary Radar/National Science Foundation’s Green Bank Observatory] T he last com- plete image of asteroid moonlet Di- morphos, taken by the DRACO imager on NASA’s DART mis- sion from ~7 miles (12 kilometers) from the as- teroid and 2 seconds be- fore impact. The image shows a patch of the asteroid that is 100 feet (31 me- ters) across. Dimorphos’ north is to- ward the top of the image. The red dot marks the impact point. The smallest pebbles on the surface are about two inches across (about 5 cm). [NASA/ Johns Hop- kins APL] The DART impact represents a signif- icant development in our quest to protect our planet. Now, we will wait for the final report that will contain additional information. For example, we will know the new ro- tational period with an error re- duced to seconds. We will also know the value of the parameter β , that measures the momentum enhance- ment due to the debris cloud. The European Space Agency, ESA, will launch the HERA spacecraft in 2024 that will reach Dimorphos two years later, and will photograph the crater left by DART. This information will be inputted into the impact model, and then, supposedly, we will be better prepared for whatever killing stones come our way. !