LICIACube image showing the plumes of debris streaming from Dimorphos shortly after the DART impact on September 26. “Each rectangle represents a different level of contrast in order to better see fine structure in the plumes,” according to the European Space Agency.
Image: ASI/NASA/APL
Earlier this week, NASA announced that its DART spacecraft successfully moved an asteroid by a few dozen feet. This raises a valid question: How the heck did scientists figure this out, given that Dimorphos is nearly 7 million miles away? Needless to say, this task required some clever astronomy and a veritable village of astronomers.
Watch
NASA’s Double Asteroid Redirection Test, or DART, shortened the amount of time it takes Dimorphos to orbit Didymos, as the spacecraft pushed the target asteroid slightly closer to its larger companion. Dimorphos’s orbital period around Didymos used to be 11 hours and 55 minutes, but it’s now 11 hours and 23 minutes—a change of 32 minutes, give or take two minutes. That represents “tens of meters” in terms of the altered distance, as Nancy Chabot, DART coordination lead at the Johns Hopkins Applied Physics Laboratory, told reporters on Tuesday.
A ‘watershed moment’
Speaking at the same press briefing, NASA administrator Bill Nelson described the successful test as a “watershed moment for humanity.” Indeed, it marks the first time that our species has purposefully changed the motion of a celestial object. Critically, it’s also the first full-scale demonstration of an asteroid deflection strategy, one that could eventually protect us from a bona fide asteroid threat.
Dimorphos doesn’t endanger Earth, but it did offer an ideal platform for testing kinetic impactor technology. The 1,340-pound DART spacecraft, following a 10-month journey to the binary asteroid system, plowed into the 525-foot-wide (160-meter) asteroid at speeds reaching 14,000 miles per hour (22,500 kilometers per hour). DART struck the asteroid with razor-like precision on September 26, but it wasn’t immediately obvious if the impact had any kind of effect.
A Hubble Space Telescope image showing the binary asteroid system shortly after the impact on September 26. The test triggered the formation of a comet-like tail composed of Sun-blown dust.
Image: NASA/ESA/STScI/Hubble
That the $308 million DART test did something to the unsuspecting asteroid was immediately obvious, with both space-based and ground-based observations revealing a dramatic plume and comet-like tail in the hours and days following the impact. It took about two weeks, however, for astronomers to confirm the new orbital dynamics imposed upon the Didymos-Dimorphos system. Two separate datasets were needed for the task, one optical and the other radar, but both pointed to the same answer: 11 hours and 23 minutes.
Catching an altered eclipse
Optical data came from ground-based observatories around the world, including the Las Cumbres Observatory (LCO) telescopes in South Africa and the Southern Astrophysical Research Telescope in Chile. A limitation of optical telescopes is that, due to the distance and small size of the Didymos-Dimorphous system, the two objects are seen as a single glowing dot. The asteroids are just 0.75 miles (1.2 km) apart, with Didymos, the larger of the two, measuring just 2,560 feet (780 meters) wide.
Ground-based optical telescopes can’t distinguish between the two, but that doesn’t mean Dimorphos is invisible to these eyes. The brightness of Didymos temporarily drops by around 10% each time Dimorphos passes in front of it. It’s through these clock-work eclipses that astronomers knew Dimorphos’s orbital period prior to the test and how they’re able to determine it now. That Dimorphos passes in front of Didymos from our perspective on Earth is fortuitous, and a key reason for why this system was chosen for the DART test.
The DART team studied reductions in brightness caused by Dimorphos’s eclipses of Didymos.
Image: NASA/Johns Hopkins APL/Astronomical Institute of the Academy of Sciences of the Czech Republic/Lowell Observatory/JPL/Las Cumbres Observatory/Las Campanas Observatory/European Southern Observatory Danish (1.54-m) telescope/University of Edinburgh/The Open University/Universidad Católica de la Santísima Concepción/Seoul National Observatory/Universidad de Antofagasta/Universität Hamburg/Northern Arizona University.
Optical observatories across the world performed continuous observations over hours-long timescales. “Since the [orbital] period was close to 12 hours, having telescopes in South Africa roughly six hours away from Chile meant we could capture the other times when Dimorphos went behind or in front of Didymos we couldn’t see from Chile,” Tim Lister, an astronomer with LCO, explained in a South African Astronomical Observatory press release. “This really helped nail down the new period and the amount of change caused by the DART impact.”
Detecting ‘faint radar echoes’
The radar data came from NASA JPL’s Goldstone planetary radar in California and the NSF’s Green Bank Observatory in West Virginia. Unlike optical telescopes, radar “can get distinct signals from both objects directly,” said Chabot.
Radar imagery from the two observatories, taken each night during a two-week campaign, were combined to create before-and-after views of the binary asteroid system. This allowed astronomers to measure the “difference between where Dimorphos is observed compared to where it would have been with the original orbit,” as NASA explained in its press package.
In this radar image, the green circle shows the location of Dimorphos around the larger Didymos asteroid, seen as the bright line across the middle of the images. The blue circle shows where Dimorphos would’ve been had the DART experiment not happened.
Image: NASA/Johns Hopkins APL/JPL/NASA JPL Goldstone Planetary Radar/National Science Foundation’s Green Bank Observatory
“The Green Bank Telescope’s large collecting area makes it extremely sensitive and a prime receiving station to detect these faint radar echoes,” Jim Jackson, director of the Green Bank Observatory, explained in a statement. “These radar measurements” were key to determining “just how dramatic the event really was by sensing changes in its orbit around Didymos and definitively establishing its deflection.”
The “two independent methods” provided “the same answer,” said Chabot, in reference to Dimorphos’s new 11 hour and 23 minute orbital period. She credited the international team for getting “onto this very quickly.” But plenty of work remains.
The beginning of the beginning
Indeed, much is unknown about the effect of the experiment. DART was a rousing success, but it’s clear that scientists still have lots to learn about kinetic impactors and the art of deflecting asteroids.
For example, astronomers need to refine their estimates of Dimorphos’s mass, shape, density, and surface composition. This will help them to understand how the DART spacecraft transferred its momentum into its target and how the ensuing effects contributed to the observed orbital shift.
Dimorphos, as imaged by the DRACO instrument aboard the DART spacecraft.
Image: NASA/Johns Hopkins APL
During Tuesday’s press briefing, Tom Statler, DART program scientist at NASA, said the recoil from the debris blasting off the surface was a major contributor to the orbital change. This is likely a consequence of Dimorphos’s physical makeup as a rubble pile asteroid, as opposed to it being a compact and cohesive rock. Statler also wondered if Dimorphos is now wobbling as a result of the impact. Astronomers are keeping a close watch on the system to refine their preliminary estimates and observe any further changes to the binary pair.
The European Space Agency is planning a follow-up mission to visit the asteroids up-close. The HERA probe, scheduled to launch in 2024, will observe Dimorphos in late 2026 and send back images and other data to help us better understand the effects of DART. A robust planetary defense system against asteroids won’t be built overnight, but this important work has now started in earnest.
NAIROBI, Kenya (AP) — The body of Ugandan Olympic athlete Rebecca Cheptegei — who died after being set on fire by her partner in Kenya — was received Friday by family and anti-femicide crusaders, ahead of her burial a day later.
Cheptegei’s family met with dozens of activists Friday who had marched to the Moi Teaching and Referral Hospital’s morgue in the western city of Eldoret while chanting anti-femicide slogans.
She is the fourth female athlete to have been killed by her partner in Kenya in yet another case of gender-based violence in recent years.
Viola Cheptoo, the founder of Tirop Angels – an organization that was formed in honor of athlete Agnes Tirop, who was stabbed to death in 2021, said stakeholders need to ensure this is the last death of an athlete due to gender-based violence.
“We are here to say that enough is enough, we are tired of burying our sisters due to GBV,” she said.
It was a somber mood at the morgue as athletes and family members viewed Cheptegei’s body which sustained 80% of burns after she was doused with gasoline by her partner Dickson Ndiema. Ndiema sustained 30% burns on his body and later succumbed.
Ndiema and Cheptegei were said to have quarreled over a piece of land that the athlete bought in Kenya, according to a report filed by the local chief.
Cheptegei competed in the women’s marathon at the Paris Olympics less than a month before the attack. She finished in 44th place.
Cheptegei’s father, Joseph, said that the body will make a brief stop at their home in the Endebess area before proceeding to Bukwo in eastern Uganda for a night vigil and burial on Saturday.
“We are in the final part of giving my daughter the last respect,” a visibly distraught Joseph said.
He told reporters last week that Ndiema was stalking and threatening Cheptegei and the family had informed police.
Four in 10 women or an estimated 41% of dating or married Kenyan women have experienced physical or sexual violence perpetrated by their current or most recent partner, according to the Kenya Demographic and Health Survey 2022.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.
Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”
Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.
“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.
B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.
Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.
Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.
Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.
“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”
Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”
“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.
Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.
“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.
This report by The Canadian Press was first published Sept. 9, 2024.
