A few weeks ago, NASA’s DART mission managed to change the orbit of the asteroid Dimorphos in a first-of-its-kind test of potential planetary defense systems. The DART spacecraft deliberately crashed into the asteroid, and the impact was observed by telescopes around the world, including the James Webb and Hubble Space Telescopes. Now, Hubble follow-up observations show a surprising finding: the asteroid now has a second tail.
These tails are more commonly associated with comets (made of ice and dust) than with asteroids (made mostly of rock). Because comets usually travel around the sun in elliptical orbits, they come closer to the sun at some times than at others. When a comet approaches the sun, it heats up and gives off dust and gas that forms a distinctive tail. In the case of the asteroid Dimorphos, the tails are composed of material released by the DART impact called ejecta.
Two tails of dust ejected from the Didymos-Dimorphos asteroid system are seen in new images from NASA’s Hubble Space Telescope, documenting the lingering aftermath of the impact from NASA’s Double Asteroid Redirect Test (DART) . SCIENCE: NASA, ESA, STScI, Jian-Yang Li (PSI) IMAGE PROCESSING: Joseph DePasquale
Dimorphos’ tail was first observed just days after the initial impact on September 26, as debris was left behind by the asteroid. But as Hubble continued to observe the asteroid in a series of 18 observations, researchers saw a second tail form between October 2 and 8.
“Repeated Hubble observations over the past few weeks have allowed scientists to present a more complete picture of how the system’s debris cloud has evolved over time,” Hubble scientists write. “The observations show that the ejected material, or ‘ejecta,’ has expanded and faded in brightness as time passed after the impact, much as expected. The twin tail is a unexpected development, although similar behavior is commonly seen in active comets and asteroids. The Hubble observations provide the best quality image of the double tail to date.”
Since this is the first time such an impact has been observed, we still have a lot to learn about the long-term effects on the asteroid and its orbit. Researchers will continue to look at Hubble data on the asteroid to gather more information, and the European Space Agency will launch its Hera mission in 2024 to visit the asteroid system and see the effects of the impact up close.
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