Astronomers using the SOAR telescope in Chile captured the vast plume of dust and debris blasted from the surface of the asteroid Dimorphos by NASA’s DART spacecraft when it collided on September 26, 2022. In this image, the more than 10,000-kilometer-long dust trail — the ejecta that has been pushed away by the Sun’s radiation pressure, not unlike the tail of a comet — can be seen stretching from the center to the right-hand edge of the field of view. Credit: CTIO/NOIRLab/SOAR/NSF/AURA/T. Kareta (Lowell Observatory), M. Knight (US Naval Academy), Image processing: T.A. Rector (University of Alaska Anchorage/NSF’s NOIRLab), M. Zamani & D. de Martin (NSF’s NOIRLab)
SOAR Telescope Catches Dimorphos’s Expanding Comet-like Tail After DART Impact
The SOAR Telescope in Chile imaged the more than 10,000 kilometers long trail of debris blasted from the surface of Dimorphos two days after the asteroid was impacted by
“It is amazing how clearly we were able to capture the structure and extent of the aftermath in the days following the impact.” — Teddy Kareta
Two days after DART’s collision, astronomers Teddy Kareta (Lowell Observatory) and Matthew Knight (US Naval Academy) captured the vast plume of dust and debris blasted from the asteroid’s surface with the 4.1-meter Southern Astrophysical Research (SOAR) Telescope,[1] at NSF’s NOIRLab’s Cerro Tololo Inter-American Observatory in Chile. In this new image, the dust trail — the ejecta that has been pushed away by the Sun’s radiation pressure, similar to the tail of a comet — can be seen stretching from the center to the right-hand edge of the field of view, which is about 3.1 arcminutes at SOAR using the Goodman High Throughput Spectrograph. At Didymos’s distance from Earth at the time of the observation, that would translate to at least 6,000 miles (10,000 kilometers) from the point of impact.
An artist’s representation of NASA’s DART spacecraft flying toward the twin asteroids, Didymos and Dimorphos. The larger asteroid, Didymos, was discovered by the University of Arizona’s Spacewatch in 1996. Credit: NASA/Johns Hopkins University Applied Physics Laboratory
“It is amazing how clearly we were able to capture the structure and extent of the aftermath in the days following the impact,” said Kareta.
“Now begins the next phase of work for the DART team as they analyze their data and observations by our team and other observers around the world who shared in studying this exciting event,” said Knight. We plan to use SOAR to monitor the ejecta in the coming weeks and months. The combination of SOAR and AEON[2] is just what we need for efficient follow-up of evolving events like this one.”
These observations will allow researchers to gain knowledge about the nature of the surface of Dimorphos. They will be able to gauge how much material was ejected by the collision, how fast it was ejected, and the distribution of particle sizes in the expanding dust cloud. For example, the observations will reveal whether the impact caused the moonlet to throw off big chunks of material or mostly fine dust. Analyzing this data will help astronomers protect Earth and its inhabitants by better understanding the amount and nature of the ejecta resulting from an impact, and how that might alter an asteroid’s orbit.
SOAR’s observations demonstrate the capabilities of NSF-funded AURA facilities in planetary-defense planning and initiatives. In the future, Vera C. Rubin Observatory, funded by NSF and the US Department of Energy and currently under construction in Chile, will conduct a census of the Solar System to search for potentially hazardous objects.
Didymos was discovered in 1996 with the University of Arizona 0.9-meter Spacewatch Telescope located at Kitt Peak National Observatory, a Program of NSF’s NOIRLab.
Notes
SOAR is designed to produce the best quality images of any observatory in its class. Located on Cerro Pachón, SOAR is a joint project of the Ministério da Ciência, Tecnologia e Inovações do Brasil (MCTI/LNA), NSF’s NOIRLab, the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).
The Astronomical Event Observatory Network (AEON) is a facility ecosystem for accessible and efficient follow-up of astronomical transients and Time Domain science. At the heart of the network, NOIRLab, with its SOAR 4.1-meter and Gemini 8-meter telescopes (and soon the Víctor M. Blanco 4-meter Telescope at CTIO), has joined forces with Las Cumbres Observatory to build such a network for the era of Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST). SOAR is the pathfinder facility for incorporating the 4-meter-class and 8-meter-class telescopes into AEON.
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NSF’s NOIRLab, the US center for ground-based optical-infrared astronomy, operates the international Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), Kitt Peak National Observatory (KPNO), Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and Vera C. Rubin Observatory (operated in cooperation with the Department of Energy’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on Iolkam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O’odham Nation, to the Native Hawaiian community, and to the local communities in Chile, respectively.
Using some of the world’s most powerful telescopes, the DART investigation team completed a six-night observation campaign last month to confirm earlier calculations of the orbit of Dimorphos—DART’s asteroid target. Dimorphos is in orbit around its larger parent asteroid, Didymos. These observations confirm where the asteroid is expected to be located at the time of impact. DART, which is the world’s first attempt to change the speed and path of an asteroid’s motion in space, tests a method of asteroid deflection that could prove useful if such a need arises for planetary defense in the future.
“The measurements the team made in early 2021 were critical for making sure that DART arrived at the right place and the right time for its kinetic impact into Dimorphos,” said Andy Rivkin, the DART investigation team co-lead at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. “Confirming those measurements with new observations shows us that we don’t need any course changes and we’re already right on target.”
On the night of July 7, 2022, the Lowell Discovery Telescope near Flagstaff, Arizona captured the asteroid Didymos. Credit: Lowell Observatory/N. Moskovitz
Understanding the dynamics of Dimorphos’ orbit, however, is important for reasons beyond ensuring DART’s impact. If DART succeeds in altering Dimorphos’ path, the moonlet will move closer toward Didymos, decreasing the time it takes to orbit it. Although measuring that change is straightforward, scientists need to confirm that nothing other than the impact is affecting the orbit. This includes subtle forces such as radiation recoil from the asteroid’s Sun-warmed surface, which can gently push on the asteroid and cause its orbit to change.
“The before-and-after nature of this experiment requires exquisite knowledge of the asteroid system before we do anything to it,” said Nick Moskovitz, an astronomer with Lowell Observatory in Flagstaff, Arizona, and co-lead of the July observation campaign. “We don’t want to, at the last minute, say, ‘Oh, here’s something we hadn’t thought about or phenomena we hadn’t considered.’ We want to be sure that any change we see is entirely due to what DART did.”
On the night of July 7, 2022, the Lowell Discovery Telescope near Flagstaff, Arizona captured this sequence in which the asteroid Didymos, located near the center of the screen, moves across the night sky. The sequence here is sped up by about 1,800 times. Scientists used this and other observations from the July campaign to confirm Dimorphos’ orbit and the anticipated location at the time of DART’s impact. Credit: Lowell Observatory/N. Moskovitz
In late September to early October, around the time of DART’s impact, Didymos and Dimorphos will make their closest approach to Earth in recent years. This will place them at approximately 6.7 million miles (10.8 million kilometers) away. Since March 2021 the Didymos system had been out of range of most ground-based telescopes because of its distance from Earth. However, early this July the DART Investigation Team employed powerful telescopes in Arizona and Chile — the Lowell Discovery Telescope at Lowell Observatory, the Magellan Telescope at Las Campanas Observatory and the Southern Astrophysical Research (SOAR) Telescope — to observe the asteroid system and look for changes in its brightness. These changes, called “mutual events,” occur when one of the asteroids passes in front of the other because of Dimorphos’ orbit, blocking some of the light they emit.
“It was a tricky time of year to get these observations,” said Moskovitz. In the Northern Hemisphere, the nights are short, and it is monsoon season in Arizona. In the Southern Hemisphere, the threat of winter storms loomed. In fact, just after the observation campaign, a major snowstorm hit Chile, prompting evacuations from the mountain where SOAR is located. This resulted in the telescope being shut down for close to ten days. “We asked for six half-nights of observation with some expectation that about half of those would be lost to weather, but we only lost one night. We got really lucky.”
In all, the team was able to extract from the data the timing of 11 new mutual events. Analyzing those changes in brightness enabled scientists to determine precisely how long it takes Dimorphos to orbit the larger asteroid. Thereby they are able to predict where Dimorphos will be located at specific moments in time, including when DART makes impact. The results were consistent with previous calculations.
“We really have high confidence now that the asteroid system is well understood and we are set up to understand what happens after impact,” Moskovitz said.
Not only did this observation campaign enable the team to confirm Dimorphos’ orbital period and expected location at the time of impact, but it also allowed team members to refine the process they will use to determine whether DART successfully changed Dimorphos’s orbit post-impact, and by how much.
In October, after DART has smashed into the asteroid, the team will again use ground-based telescopes around the world to look for mutual events and calculate Dimorphos’ new orbit. They are expecting that the time it takes the smaller asteroid to orbit Didymos will have shifted by several minutes. These observations will also help constrain theories that scientists around the world have put forward about Dimorphos’ orbit dynamics and the rotation of both asteroids.
The DART mission will be the first to test asteroid deflection through kinetic impactor technology. Illustration: NASA
In order to protect the Earth, some sacrifices must be made. NASA’s DART spacecraft is currently on its way to a binary asteroid system known as Didymos and will essentially crash into one tiny asteroid to test out a deflection method. But rather than leaving behind an impact crater as initially intended, the DART spacecraft may actually deform the mini-moon, making it nearly unrecognizable.
Using a new model, a group of researchers have simulated the entire cratering process and discovered that the asteroid deflection mission might completely alter its target, changing its appearance far more severely than previously believed.
“The DART impact could globally deform Dimorphos, and therefore change its overall shape significantly, instead of creating just a small crater,” Martin Jutzi, co-author of the study, which was published in The Planetary Science Journal, told Gizmodo in an email.
This illustration shows the possible shapes that the asteroid might take following impact.Illustration: Courtesy of Martin Jutzi
As seen in the above illustration, the mini-moon, dubbed Dimorphos (formerly known as Didymoon), could take on one of these six possible shapes following the spacecraft’s impact. The whole cratering process could take a few hours, which is why previous models of the impact did not predict the asteroid’s subsequent deformation. “Previous models were only able to simulate the first seconds of such events,” Jutzi said.
Short for Double Asteroid Redirection Test, the DART mission launched in November 2021 towards the Didymos asteroid system. Didymos is an 800-meter wide rock with its own 170-meter wide moon known as Dimorphos, the main target of DART. The spacecraft will smash into the mini-moon at 15,000 miles per hour (24, 140 kilometers per hour), attempting to offset its orbit. The impact is scheduled for late September or early October, when the pair will come within 7 million miles (11 million kilometers) of Earth.
The purpose of the test is to experiment with kinetic impactor technology as a means of deflecting asteroids that could be headed towards Earth. NASA and other space agencies, keep a close watch on asteroids that come too close for comfort in order to assess whether or not they pose a threat to our planet. But as far as defending Earth from incoming asteroid impacts, there’s no clear cut plan on what to do.
“These weak asteroids could actually be deflected much more strongly and larger amounts of material could be ejected from the impact than the previous estimates predicted,” Jutzi said. “These larger effects should be easier to observe immediately after the DART impact.” So the DART mission will still be able to perform the experiment, just perhaps with a different outcome than initially anticipated.
The European Space Agency (ESA) is also planning a follow-up mission to the pair of space rocks. ESA is scheduled to launch its Hera mission in 2024, which will rendezvous with Didymos by 2026 to study the impact crater left behind by DART, and any other changes made to the asteroid. If Dimorphos has indeed taken on a different appearance, it may provide valuable data on the asteroid itself.
“Ideally, this will allow us to learn something about the asteroid’s interior, rather than just the surface,” Jutzi said. “This would in turn provide very valuable information about the asteroid’s bulk properties and improve our understanding of asteroids in general.”
More: The Spacecraft That’s Going to Smash Into an Asteroid Just Sent Back Its First Pictures
Artist’s impression of Dimorphos shortly after being struck by NASA’s DART spacecraft. China’s proposed kinetic impaction test would likely use a similar strategy. Image: ESA
The global effort to protect Earth from dangerous asteroids is set to become stronger, as China has announced its intentions to test an asteroid redirect system as early as 2025.
Speaking to China Central Television on Sunday, Wu Yanhua, deputy head of the China National Space Administration (CNSA), described China’s preliminary plans to embark on the planetary defense project, according to Chinese state-owned news agency Global Times. Wu’s comments coincided with Space Day, an annual event that commemorates the 1970 launch of China’s first satellite, Dongfanghong-1, in 1970.
For the proposed test, Wu said a probe would closely survey a near-Earth object prior to smashing into it. Known as kinetic impaction, the idea is to alter the orbital trajectory of a threatening asteroid by directing a large, high-speed spacecraft into the object. NASA is currently running a similar test, known as the Double Asteroid Redirection Test, or DART, which seeks to deliberately crash a space probe into Dimorphos—a tiny asteroid—later this year.
The Global Times says the CNSA project is in its infancy and is still being reviewed for approval. The Chinese space agency is targeting 2025 or 2026 to conduct the test, a timeline that coincides with the end of China’s 14th Five-year plan period, according to Wu.
In addition, Wu said the CNSA hopes to develop a ground-based monitoring and warning system to analyze and catalog potentially dangerous near-Earth objects. No further details were given, but the system will likely emulate NASA’s Sentry-II monitoring system, which autonomously evaluates asteroid impact risks. Software designed to simulate the risks posed by asteroids and tabletop exercises to rehearse the defense process are also planned, according to the Global Times, adding that China is “shouldering the responsibility as a major global power in safeguarding the Earth with other countries.” The proposed monitoring and warning system would precede the asteroid mitigation test, Wu said.
Having more eyes on the sky is a good thing. My hope is that CNSA, NASA, and other space agencies and astronomical groups will pool their resources to make sure no threatening asteroids are missed and to coordinate these efforts in meaningful ways. NASA says it’s currently tracking 28,000 near-Earth objects and that roughly 3,000 are being added to the list each year.
The proposed CNSA program and kinetic impaction test is welcome news and another sign of China’s ongoing ambitions in space and space exploration. The country’s space-based initiatives are advancing quickly, as evidenced by its robotic lunar and Martian missions and its nascent space station, which is being made available to foreign astronauts, including space tourists.
If you’re a fan, like I am, of not being crushed to death by a rock that falls from the sky, then you should be interested in the mission NASA launched today with a SpaceX Falcon 9 rocket. The spacecraft in the nose of that rocket is called DART (Double Asteroid Redirection Test), and that spacecraft is going to smack right into the asteroid Dimorphos in hopes of redirecting its path.
Now, I’m happy to say this is being done not because Dimorphos is actually threatening to hit the Earth but because it makes for a good test subject. See, Dimorphos is part of a binary pair of asteroids and orbits around the asteroid Didymos, so NASA can tell if the impact of DART into Dimorphos affected its orbit around Didymos. It can then use that information to calculate how a similar strike to an asteroid potentially headed to Earth could be deflected.
The spacecraft is small and boxy, and it will hit Dimorphos at an impressive 14,760 mph, sped along by its NEXT xenon ion thruster engine, which converts solar energy into gradual but persistent thrust.
Illustration: NASA
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An onboard camera and autonomous navigation software will guide DART to its self-sacrifice into the asteroid, which will change the speed of the asteroid’s orbit around the main asteroid by a fraction of a percent. But that should affect the orbital period by several minutes, all of which will be confirmed by observations from Earth.
Illustration: Ted Lopez / Johns Hopkins APL
DART won’t arrive at the asteroid pair until next September or so, which means you have plenty of time to figure out how to get close if you want a ringside seat.
The ability to deflect an asteroid could one day prove to be absolutely crucial to the safety of everything living on Earth. While, so far, NASA does not predict an asteroid of significant size hitting Earth in the next century or so, there have been 1,200 meteor impacts to Earth from asteroids over three feet in length since 1988, and only 0.42 percent of those—five—were actually predicted in advance.
So, it’s not exactly like we have a really solid handle on this whole asteroid-prediction thing, and figuring out a way to be ready to deflect something would really be a great idea. Ideally, if this test works, a similar deflecting spacecraft will be made available and be ready to go, should the situation arise in the future.
