South Korea has canceled its effort to visit the space rock Apophis during a close, but harmless, flyby of our Earth in 2029, according to a media report.
The country’s science ministry says the proposed Apophis mission had a “lack of technical capabilities” that rendered the concept “unfeasible,” SpaceNews reported (opens in new tab) June 7. Ultimately, the ministry decided not to request the nearly $308 million it wanted to run the mission.
“The mission involved launching a robotic spacecraft between July 2026 and January 2027 to accompany Apophis as it whips by Earth in April 2029,” SpaceNews added. “The probe would observe and map Apophis the whole way, looking for changes in its structure due to its close encounter with Earth and the planet’s gravitational forces.”
Related: Huge asteroid Apophis revealed in photos
South Korea is a 2021 signatory of the NASA-led Artemis accords for peaceful space exploration, particularly of the moon, and plans its own lunar missions in the 2030s.
Early examinations of Apophis suggested it had a statistically unlikely, but still feasible, chance of hitting Earth in 2068. But newer analysis in the last year shows the asteroid doesn’t pose a threat for at least the last century. (NASA continues to keep an eye out for problems, but decades of scanning with partner telescopes have yielded no immediately worrisome near-Earth objects.)
Shin Won-sik, a science ministry official with South Korea, confirmed the cancelation of his country’s mission to SpaceNews, but added the country is considering more asteroid missions in the future. The country’s forthcoming fourth revision of its space development plan should include something “a bit more concrete and realistic” than what was feasible with the Apophis mission, he said.
The third revision (opens in new tab) of the plan, released in February 2018, had few technical details about the mission, SpaceNews added. Work on the fourth revision should begin in the second half of 2022, Shin said.
While South Korea is not expected to visit the once-notorious asteroid any more, there are other plans in the works to take advantage of the unique 2029 opportunity, many still in the mission concept stage.
In April, NASA announced its ongoing asteroid-scooping OSIRIS-REx mission, which stands for the Origins-Spectral Interpretation-Resource Identification-Security-Regolith Explorer, will be repurposed to visit Apophis. The mission will also acquire a new moniker: OSIRIS-APEX, which is short for OSIRIS-Apophis Explorer.
Follow Elizabeth Howell on Twitter @howellspace. Follow us on Twitter @Spacedotcom and on Facebook.
An early-stage mission concept could see laser-driven light-sail probes visit a notorious asteroid.
The space rock Apophis, which poses no threat to Earth whatsoever for at least 100 years, will make a harmless but very close flyby of our Earth in 2029. Scientists have already figured out a way to visit Apophis after the flyby: NASA’s OSIRIS-REx spacecraft will visit the asteroid after dropping off samples from another space rock at Earth, the agency decided in April.
But 2029 might be just enough time to squeeze out a few more mission ideas. A conference held online May 11 and 12 by the Houston-based Lunar and Planetary Institute investigated possible applications for planetary defense.
Among the presentations was one describing an idea to test out a rapid launch scenario in case of impending trouble, not that we have found any asteroids to worry about yet. It also could serve as an early test for another laser-driven craft that may go interstellar one day, known as Breakthrough Starshot.
Related: Huge asteroid Apophis revealed in photos
The May 12 presentation, by Paul Blase of small satellite startup Space Initiatives Inc. of Florida, outlined a mission concept that would launch a pair of mini spacecraft aboard a Black Brant sounding rocket. Each probe would be armed with a few simple instruments like tiny cameras and spectrometers.
One spacecraft would release above the thickest part of the atmosphere at 46 miles (75 kilometers), while the other would release at the rocket’s maximum altitude of 930 miles (1,500 kilometers). A laser array fired from Earth (potentially at NASA’s facility on Wallops Island in Virginia, Blase suggested), would then push each probe to an apogee of 18,600 miles (30,000 km). The Friday the 13th flyby of Apophis in 2029 will see the asteroid pass by in this range, which is so close that it is within the orbit of some satellites.
The first 3D-printed probe would impact the asteroid, while the second would observe the impact plume with a spectrometer, Blase explained. The data would be recovered from the second spacecraft after re-entry.
“This is only a gram,” he said of the impacting spacecraft’s mass, “so it’s not going to do much. But it will raise a plume.”
The team is considering other mission concepts, too. There could be regular flybys in the weeks before, during and after approach, for example. Each of these concepts would cost about $2 million, Blase estimated, which is relatively cheap for spacecraft development.
He estimated it would only take five years to put the mission together. “And then once Apophis comes through, everything’s done in about 12 hours,” he said.
Testing an asteroid rapid-response capability will be critical for planetary defense one day, Blase said. Space-rock tracking has improved, but many (harmless) near-Earth asteroids are spotted with a week or less to go before their first known flyby.
The team envisions having these little laser-driven craft on standby to rapidly approach a hazardous space rock and redirect it. “All of the basic technology in the this proposal currently exists,” he said, adding, “We believe that Apophis offers a good opportunity to develop these capabilities for future use.”
While this early-stage and so-far unfunded proposal is not associated with the ambitious Breakthrough Starshot that hopes to reach the Alpha Centauri system in a few decades, Blase said his team’s laser craft would serve as a help for that mission’s planning.
For example, the laser array necessary for the asteroid mission would be tens of megawatts instead of gigawatts, meaning testing could occur at a smaller scale for feasibility. The Apophis mission also would happen very close to Earth, allowing for engineering assessments to take place before an interstellar craft departs.
Follow Elizabeth Howell on Twitter @howellspace. Follow us on Twitter @Spacedotcom and on Facebook.
The study, in which the Universidad Carlos III de Madrid (UC3M) and the Universidad Estatal Paulista Júlio de Mesquita Filho (Júlio de Mesquita Filho Paulista State University) (UNESP) of Brazil are participating, analyzes the surface and dynamics of Apophis, an asteroid that will pass close to Earth in 2029.
The Apophis asteroid was discovered in 2004 and has been monitored since then due to its classification as a potentially hazardous asteroid (PHA), as it was estimated that it would have a 2% chance of hitting Earth. This possibility has already been ruled out and, according to the latest measurements, Apophis will reach its closest trajectory to Earth (38,000 kilometers) on the 13th of April, 2029.
This study analyzes the physical characteristics of this celestial body and the possible effects that its approach to Earth may have. Gabriel Borderes-Motta, a researcher at UC3M’s Department of Bioengineering and Aerospace Engineering, explains that “collision is not the only possibility in approach events like this one. The gravitational interaction between a planet and a body such as Apophis can change the shape of the body, break the body into pieces, disintegrate possible loose stones on the asteroid’s surface, or even remove other bodies orbiting the asteroid (such as rocks, satellites, or rings)… Our study focuses on the last two possibilities: what happens to the possible stones on the surface and the asteroid’s orbit.”
How to experiment with an asteroid
Research in the space sector presents the challenge that, in most cases, it is impossible to directly experiment with space materials. For this reason, numerous investigations are approached from the field of mathematics and physics, taking the greatest possible number of variables into account.
The research team responsible for this study has analyzed both the physical aspects of the asteroid—among them, its shape and the characteristics of its gravitational field—as well as the factors that can influence its trajectory and its slope angle, such as the radiation pressure or disturbance inflicted due to its proximity to Earth.
To carry out this piece of research, the team has carried out a set of numerical simulations—two simulation environments with three experimental cases each—using a disk of 15,000 particles of different sizes in the close environment of Apophis as a sample. The objective has been to try to predict how the particles orbiting the asteroid will react to different situations and how these assumptions may influence the behavior of Apophis.
The first set of simulations was designed considering only the gravitational disturbance of Apophis in 24-hour periods over 30 years. The second set of simulations included disturbance caused by solar radiation pressure. Three cases were proposed in both sets, in which the asteroid had different densities. “We evaluated a 340-meter polyhedron with a uniform density in three different cases. In each case, the starting point was a different particle density, from highest to lowest,” says Gabriel Borderes-Motta.
From these simulations, it was concluded that the asteroid’s slope angle was greater at low densities (4°) than at high densities (2°); in addition, the lower the particle density and the higher the solar radiation pressure, the fewer particles remained intact. In other words, in a scenario where Apophis has a low density, approximately 90% of the loose stones would be removed from its surface during the approach to Earth. In addition, the results have shown that Apophis’s approach could slightly affect the tides and cause some landslides on the asteroid’s surface.
The team hopes that the asteroid’s approach to Earth in 2029 will be an opportunity to improve the 3D model used to run space simulations, as well as to allow them to more accurately investigate and predict the effects on Apophis’s surface. All of this would mean an increase in knowledge about asteroids, which would allow us to be better prepared in the event that new celestial bodies pass close to Earth.
The research was published in Monthly Notices of the Royal Astronomical Society.
Massive asteroid subject of new findings
More information:
G Valvano et al, APOPHIS – effects of the 2029 Earth’s encounter on the surface and nearby dynamics, Monthly Notices of the Royal Astronomical Society (2021). DOI: 10.1093/mnras/stab3299
Provided by
Carlos III University of Madrid
Citation:
A research study analyzes the characteristics of Apophis, the asteroid that will approach Earth in 2029 (2022, March 22)
retrieved 23 March 2022
from https://phys.org/news/2022-03-characteristics-apophis-asteroid-approach-earth.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.
Apophis as it was imaged during its most recent flyby. Image: NASA/JPL-Caltech and NSF/AUI/GBO
Asteroid Apophis—one of the scariest rocks in the solar system—won’t pose a threat to Earth for at least another century, according to updated NASA calculations.
Every 80,000 years or so, an object measuring around three football fields in length smashes into Earth, unleashing the equivalent of over 1,000 megatons of TNT. The discovery of Apophis in 2004 fit the description of one of these once-in-80,000-year events, understandably freaking a lot of people out. A hit from Apophis wouldn’t be Chicxulub bad—the 10-mile-wide (16-kilometer) asteroid that wiped out most life on the planet some 66 million years ago—but it’d inflict catastrophic levels of local damage and trigger a global-scale impact winter.
In 2004, astronomers detected asteroid 99942 Apophis, a near Earth object measuring around 1,100 feet (340 meters) long. Its status as a potentially hazardous object has been continually refined over the years, but 2068 continued to represent a particularly worrisome year for the asteroid to hit us.
We can now breathe a sigh of relief, however, as the latest calculations suggest the asteroid won’t pose a threat to Earth for the time being, according to a NASA statement. A recent flyby of Apophis, in which the asteroid came to within 44 times the distance of Earth to the Moon, allowed NASA to refine its measurements, resulting in the new assessment.
“A 2068 impact is not in the realm of possibility anymore, and our calculations don’t show any impact risk for at least the next 100 years,” Davide Farnocchia of NASA’s Center for Near-Earth Object Studies explained in the space agency’s announcement.
G/O Media may get a commission
As a consequence, NASA has now removed Apophis from its naughty list, otherwise known as the Sentry Impact Risk Table. This table, maintained by CNEOS, had ranked Apophis as the third most dangerous known object, assessing an impact probability at around 1 in 150,000. The odds were slim but undeniably nonzero. The new calculations have allowed CNEOS to remove Apophis from the risk table altogether.
“With the support of recent optical observations and additional radar observations, the uncertainty in Apophis’ orbit has collapsed from hundreds of kilometers to just a handful of kilometers when projected to 2029,” said Farnocchia. “This greatly improved knowledge of its position in 2029 provides more certainty of its future motion, so we can now remove Apophis from the risk list.”
The year 2029 is notable because that’s the next time Apophis will fly past Earth, during which time it’ll seriously invade our personal space. It will come to within 20,000 miles (32,000 km) of our planet, which is a tenth the distance of Earth to the Moon and within the reach of some satellites. Apophis will be so close that it’ll be visible to small telescopes and binoculars.
When Apophis flew past Earth in early March this year, it was just 10.6 million miles (17 million km) away. NASA took the opportunity to study and refine the asteroid’s position, which the space agency did using the radio antenna at Deep Space Network’s Goldstone Deep Space Communications Complex in California. This instrument allowed the team to calculate Apophis’s position to an accuracy of roughly 490 feet (150 meters).
Marina Brozovic, the JPL scientist who led the radar campaign, said if “we had binoculars as powerful as this radar, we would be able to sit in Los Angeles and read a dinner menu at a restaurant in New York,” as she explained in the statement.
Using the Green Bank Telescope in West Virginia, the team was able to double the strength of the incoming radio signal, resulting in an imaging resolution of 127 feet (38.75 meters) per pixel.
Analysis of the data is still incomplete, and the team is hoping to better characterize the shape of Apophis (it’s suspected to have a bilobed appearance, in which two asteroids fused together to create a peanut-like shape), along with improved estimates of its rotation rate and spin state along its axis. These numbers will help to predict the object’s behavior for the 2029 flyby, which scientists say is a once-in-a-thousand-year opportunity to study an object of this size from such close proximity.
With Apophis officially booted from the Sentry Impact Risk Table, the top rated NEOs in terms of risk are the 0.8-mile-wide (1.3-km) asteroid 29075 (1950 DA), which has a 1 in 8,300 risk of hitting Earth in 2880; the 1,608-foot-wide (490-m) asteroid 101955 Bennu (1999 RQ36), which has a 1 in 2,700 chance of impact from 2175 to 2199; and the 121-foot-wide (37-meters) asteroid 2009 JF1, which has a 1 in 3,800 chance of hitting Earth next year (May 6, to be exact, so mark your calendars).
These rankings are based on the Palermo Technical Impact Scale, which takes other variables into account aside from impact probability, such as an object’s potential to inflict wide-scale damage.
When it comes back around again in 2068, the asteroid Apophis will have practically no chance of hitting Earth.
In fact, the 370-meter (1,210-foot) chunk of space rock won’t pose any sort of danger for at least another century, leading to its removal from both the ESA’s Risk List, and NASA’s Sentry Impact Risk Table.
“With the support of recent optical observations and additional radar observations, the uncertainty in Apophis’s orbit has collapsed from hundreds of kilometers to just a handful of kilometers when projected to 2029,” said astronomer Davide Farnocchia of NASA’s Center for Near-Earth Object Studies.
“This greatly improved knowledge of its position in 2029 provides more certainty of its future motion, so we can now remove Apophis from the risk list.”
Apophis was first discovered in 2004, and initial projections suggested the asteroid had a worrying 2.7 percent chance of impacting Earth in 2029. Although this was quickly ruled out, Apophis has a close approach to Earth roughly every eight years; because its orbit has been tricky to observe and characterize, the possibility of an impact at a later date remained undefined.
Gradually, over the 17 years that astronomers have been watching Apophis, its path through space has become clearer.
Last year, the biggest danger was determined to be the asteroid’s 2068 close approach. Farnocchia and his colleague David Tholen measured the Yarkovsky effect – that is, the heating on the asteroid’s Sun side that generates a small amount of thrust – and found that it generates 170 meters of drift a year.
The other big potential problem affecting the asteroid’s path is that 2029 flyby. According to projections, Apophis will fly past Earth at a distance of just 38,000 kilometers – roughly 10 times closer than the Moon. At that proximity, Earth’s gravity will affect the asteroid’s orbit, possibly bringing it closer to a collision course.
With these two influences in mind, the astronomers recalculated the projection of Apophis’s path. The chance of impact in 2068 remained. It was only one in 150,000, but that’s still a concern, considering how much damage it could do.
Now more data has been added to the calculations. The asteroid’s most recent flyby was just a few weeks ago – on 6 March 2021, Apophis came within 16.9 million kilometers of Earth.
For months prior, it had been visible in the sky, and astronomers watched it closely; then the March 6 flyby allowed scientists to narrow down its location to an incredibly precise distance of 150 meters.
In turn, the finding allowed for further refinement of the projections, and we’re now officially safe from Apophis for a very long time indeed. Considering that the asteroid has been sitting on the Risk List and the Sentry Impact Risk Table since it was discovered, this is a big relief.
When Apophis does swing by in 2029, it will afford scientists an excellent opportunity to study its size, shape, and spin rate, without the threat of doom looming, too. It will be the last such opportunity for a while – after 2029, its ‘close approaches’ will grow more and more distant.
“When I started working with asteroids after college, Apophis was the poster child for hazardous asteroids,” Farnocchia said.
“There’s a certain sense of satisfaction to see it removed from the risk list, and we’re looking forward to the science we might uncover during its close approach in 2029.”
The near-Earth object was thought to pose a slight risk of impacting Earth in 2068, but now radar observations have ruled that out.
After its discovery in 2004, asteroid 99942 Apophis had been identified as one of the most hazardous asteroids that could impact Earth. But that impact assessment changed as astronomers tracked Apophis and its orbit became better determined.
Now, the results from a new radar observation campaign combined with precise orbit analysis have helped astronomers conclude that there is no risk of Apophis impacting our planet for at least a century.
Estimated to be about 1,100 feet (340 meters) across, Apophis quickly gained notoriety as an asteroid that could pose a serious threat to Earth when astronomers predicted that it would come uncomfortably close in 2029. Thanks to additional observations of the near-Earth object (NEO), the risk of an impact in 2029 was later ruled out, as was the potential impact risk posed by another close approach in 2036. Until this month, however, a small chance of impact in 2068 still remained.
When Apophis made a distant flyby of Earth around March 5, astronomers took the opportunity to use powerful radar observations to refine the estimate of its orbit around the Sun with extreme precision, enabling them to confidently rule out any impact risk in 2068 and long after.
These images of asteroid Apophis were recorded by radio antennas at the Deep Space Network’s Goldstone complex in California and the Green Bank Telescope in West Virginia. The asteroid was 10.6 million miles (17 million kilometers) away, and each pixel has a resolution of 127 feet (38.75 meters). Credit: NASA/JPL-Caltech and NSF/AUI/GBO
“A 2068 impact is not in the realm of possibility anymore, and our calculations don’t show any impact risk for at least the next 100 years,” said Davide Farnocchia of NASA’s Center for Near-Earth Object Studies (CNEOS), which is managed by NASA’s Jet Propulsion Laboratory in Southern California. “With the support of recent optical observations and additional radar observations, the uncertainty in Apophis’ orbit has collapsed from hundreds of kilometers to just a handful of kilometers when projected to 2029. This greatly improved knowledge of its position in 2029 provides more certainty of its future motion, so we can now remove Apophis from the risk list.”
This animation depicts the orbital trajectory of asteroid 99942 Apophis as it zooms safely past Earth on April 13, 2029. Earth’s gravity will slightly deflect the trajectory as the 1,100-foot-wide (340-meter-wide) near-Earth object comes within 20,000 miles (32,000 kilometers) of our planet’s surface. The dots are the many man-made satellites that orbit our planet. The motion has been speeded up 2,000 times. Credit: NASA/JPL-Caltech
Farnocchia was referring to the Sentry Impact Risk Table. Maintained by CNEOS, the table keeps tabs on the few asteroids whose orbits take them so close to Earth that an impact can’t be ruled out. With the recent findings, the Risk Table no longer includes Apophis.
Relying on optical telescopes and ground-based radar to help characterize every known near-Earth object’s orbit to improve long-term hazard assessments, CNEOS computes high-precision orbits in support of NASA’s Planetary Defense Coordination Office.
Science Opportunity
To arrive at the latest Apophis calculations, astronomers turned to the 70-meter (230-foot) radio antenna at the Deep Space Network’s Goldstone Deep Space Communications Complex near Barstow, California, to precisely track Apophis’ motion. “Although Apophis made a recent close approach with Earth, it was still nearly 10.6 million miles [17 million kilometers] away. Even so, we were able to acquire incredibly precise information about its distance to an accuracy of about 150 meters [490 feet],” said JPL scientist Marina Brozovic, who led the radar campaign. “This campaign not only helped us rule out any impact risk, it set us up for a wonderful science opportunity.”
This animation shows the path along Earth where Apophis will be visible on April 13, 2029. As the asteroid passes over the Atlantic ocean, its path briefly turns from red to grey – that is the moment of closest approach. After closest approach, the asteroid will move into the daytime sky and will no longer be visible. Credit: Marina Brozović/JPL
Goldstone also worked in a collaboration with the 100-meter (330-foot) Green Bank Telescope in West Virginia in order to enable imaging of Apophis; Goldstone was transmitting while Green Bank was receiving – a “bistatic” experiment that doubled the strength of the received signal.
Although the radar imagery of Apophis appears pixelated, the images have a resolution of 38.75 meters (127 feet) per pixel, “which is a remarkable resolution, considering the asteroid was 17 million kilometers away, or about 44 times the Earth-Moon distance,” added Brozovic. “If we had binoculars as powerful as this radar, we would be able to sit in Los Angeles and read a dinner menu at a restaurant in New York.”
This animation shows the distance between the Apophis asteroid and Earth at the time of the asteroid’s closest approach. The blue dots are the many man-made satellites that orbit our planet, and the pink represents the International Space Station. Credit: Marina Brozović/JPL
As the radar team further analyzes their data, they also hope to learn more about the asteroid’s shape. Previous radar observations have suggested that Apophis has a “bilobed,” or peanutlike, appearance. This is a relatively common shape among the near-Earth asteroids larger than 660 feet (200 meters) in diameter; at least one in six have two lobes.
Astronomers are also working to develop a better understanding of the asteroid’s rotation rate and the axis it spins around (known as its spin state). That knowledge will enable them to determine the orientation the asteroid will have with Earth as it encounters our planet’s gravitational field in 2029, which could change that spin state and even cause “asteroid quakes.”
On April 13, 2029, the asteroid Apophis will pass less than 20,000 miles (32,000 kilometers) from our planet’s surface – closer than the distance of geosynchronous satellites. During that 2029 close approach, Apophis will be visible to observers on the ground in the Eastern Hemisphere without the aid of a telescope or binoculars. It’s also an unprecedented opportunity for astronomers to get a close-up view of a solar system relic that is now just a scientific curiosity and not an immediate hazard to our planet.
“When I started working with asteroids after college, Apophis was the poster child for hazardous asteroids,” said Farnocchia. “There’s a certain sense of satisfaction to see it removed from the risk list, and we’re looking forward to the science we might uncover during its close approach in 2029.”
Asteroid 99942 Apophis has been considered one of the most hazardous asteroids with the potential to impact Earth since its discovery in 2004. Now, scientists have revised that opinion after a precise analysis of the asteroid’s orbit.
Previous predictions noted that the 1,110-foot-wide asteroid might be too close for comfort in 2029, 2036, and it could have a slight chance of impacting Earth in 2068.
It recently passed within 10 million miles of Earth on March 5.
During that distant flyby, astronomers used radar observations to get a better handle on the asteroid’s orbit around the sun. Their results allowed them to rule out any risk of the asteroid impacting Earth in 2068. The previous concerns about 2029 and 2036 had already been put aside due to prediction refinements and research.
“A 2068 impact is not in the realm of possibility anymore, and our calculations don’t show any impact risk for at least the next 100 years,” said Davide Farnocchia, navigation engineer and researcher at NASA’s Center for Near-Earth Object Studies (CNEOS), in a statement.
“With the support of recent optical observations and additional radar observations, the uncertainty in Apophis’ orbit has collapsed from hundreds of kilometers to just a handful of kilometers when projected to 2029,” Farnocchia said. “This greatly improved knowledge of its position in 2029 provides more certainty of its future motion, so we can now remove Apophis from the risk list.”
The CNEOS Center maintains a risk list, tracking asteroids with orbits that bring them close to Earth — close enough to cause concern over a potential impact. Scientists at the center use radar and telescopes to study near-Earth objects and understand the dangers they may pose to the planet.
The European Space Agency’s Near-Earth Object Coordination Centre also has removed the asteroid from its risk list.
The CNEOS Center is managed by NASA’s Jet Propulsion Laboratory in Pasadena, California.
In order to observe Apophis and remove it from the risk list, astronomers used the Deep Space Network’s Goldstone radio antenna near Barstow, California. This dish is one of three around the globe that enable communications with spacecraft across deep space. Scientists also relied on a collaboration with the Green Bank Telescope in West Virginia.
“Although Apophis made a recent close approach with Earth, it was still nearly 10.6 million miles away,” said Marina Brozovic, a scientist at JPL, in a statement. “Even so, we were able to acquire incredibly precise information about its distance to an accuracy of about 150 meters (490 feet). This campaign not only helped us rule out any impact risk, it set us up for a wonderful science opportunity.”
While the images seem fuzzy, the resolution is quite strong considering the asteroid was about 17 million miles away, or 44 times the distance between Earth and the moon, at the time.
“If we had binoculars as powerful as this radar, we would be able to sit in Los Angeles and read a dinner menu at a restaurant in New York,” Brozovic said.
The data from this observation will help scientists learn more about the asteroid’s shape and rotation rate. The current belief is that Apophis is shaped like a peanut.
Even though Apophis poses no risk over the next century, it will encounter Earth’s gravitational field during its flyby on April 13, 2029, and will pass within 20,000 miles of Earth’s surface. That’s closer than satellites that orbit Earth and 10 times nearer than the moon.
Apophis will be visible to people in the Eastern hemisphere with the naked eye, no telescope or binoculars needed. And astronomers will get their chance to study the asteroid up close.
“When I started working with asteroids after college, Apophis was the poster child for hazardous asteroids,” Farnocchia said. “There’s a certain sense of satisfaction to see it removed from the risk list, and we’re looking forward to the science we might uncover during its close approach in 2029.”
Nasa has given Earth the all clear on the chances of an asteroid called Apophis hitting our planet any time in the next century, having worried space scientists for over 15 years.
The 340-metre (1,100ft) chunk of space rock hit the headlines in 2004 after its discovery led to some worrying forecasts about its orbit. It became a “poster child for hazardous asteroids”, according to one Nasa expert.
It was supposed to come frighteningly close in 2029 and again in 2036. Nasa ruled out any chance of a strike during those two close approaches a while ago, but a potential 2068 collision still loomed.
But new telescope observations mean that collision has been ruled out and Apophis has been officially taken off the US space agency’s asteroid “risk list”.
Davide Farnocchia of Nasa’s center for near-Earth object studies, said in a statement: “A 2068 impact is not in the realm of possibility any more, and our calculations don’t show any impact risk for at least the next 100 years.”
Scientists were able to refine Apophis’ orbit around the sun thanks to radar observations earlier this month, when the asteroid passed within 17m km (10.6m miles).
Apophis will come within 32,000km (20,000 miles) of Earth on Friday 13 April 2029, enabling astronomers to get a good look. That is about one-tenth of the distance to the moon and closer than the communication satellites that encircle the Earth at 36,000km.
“When I started working with asteroids after college, Apophis was the poster child for hazardous asteroids,” Farnocchia said. “There’s a certain sense of satisfaction to see it removed from the risk list.”
Although most asteroids are found in the belt of space between Mars and Jupiter, not all of them reside there. Apophis belongs to a group known as the Aten family. These do not belong to the asteroid belt and spend most of their time inside the orbit of the Earth, placing them between our planet and the sun.
That makes them particularly dangerous because they spend the majority of their orbit close to the sun, whose overwhelming glare obscures them to telescopes on Earth – rather like a second world war fighter ace approaching out of the sun.
The notorious Apophis space rock just shed its hazardous status — for the next 100 years at least — after fresh observations of the near-Earth asteroid.
Astronomers have been keeping an eye on Apophis since its discovery in 2004, after initial estimations based on a more preliminary orbit suggested it would come uncomfortably close to our planet in 2029. Apophis’ large size added to this concern, as it stretches 1,100 feet (340 meters) across — about 10 times larger than the object that created Meteor Crater in Arizona.
After refining the initial observations, astronomers found that there was no real risk of impact in 2029. Now, after Apophis safely passed by Earth earlier this month, there’s more good news: the asteroid won’t hit Earth in 2068 either. The space rock has also been removed from a risk list known as the Sentry Impact Risk Table, which is maintained by NASA’s Center for Near-Earth Object Studies (CNEOS), which is managed by the agency’s Jet Propulsion Laboratory.
Related: Huge Asteroid Apophis Revealed in Photos
The Sentry Impact Risk Table is a set of asteroids that show asteroids grazing so close to Earth that a future impact can’t be ruled out. This “risk list” tracks asteroids that are predicted to get close enough to Earth to where there is the possibility of impact, although happily, there are no imminent threats known to our planet..
“When I started working with asteroids after college, Apophis was the poster child for hazardous asteroids,” Davide Farnocchia, who analyzes asteroid orbits at CNEOS, said in a statement.
These NASA radar images show the asteroid Apophis on March 8, 9 and 10 as it passed within 10.6 million miles (17 million kilometers) of Earth in a 2021 flyby. (Image credit: NASA/JPL-Caltech and NSF/AUI/GBO)
“There’s a certain sense of satisfaction to see it removed from the risk list, and we’re looking forward to the science we might uncover during its [next] close approach in 2029,” Farnocchia added. In 2029, Apophis will zoom by Earth at roughly 20,000 miles (32,000 kilometers) from our planet’s surface, a little closer than geosynchronous orbiting satellites.
This new information came from observations of Apophis’ flyby of Earth on March 5, when the rock swooped within 0.11 astronomical units, with 1 AU representing the distance between the Earth and the sun (93 million miles or 150 million kilometers), of Earth. With observations of this flyby, astronomers used radar to further refine our understanding of Apophis’ path around the sun.
The radar telescope at Puerto Rico’s Arecibo Observatory unfortunately retired a few months ago after it collapsed in 2020, but observations were still possible with facilities such as the Deep Space Network’s Goldstone complex in California and the Green Bank Telescope in West Virginia. The various telescopes showed good news for an asteroid that has been deemed a risk for half a generation.
“A 2068 impact is not in the realm of possibility anymore, and our calculations don’t show any impact risk for at least the next 100 years,” Farnocchia said. This allowed the group to remove Apophis from the risk list
Goldstone and Green Bank worked together to obtain imaging of Apophis, with Goldstone transmitting a radar signal and Green Bank receiving the reflection. The resulting radar imagery was pixelated, but still showed a resolution of roughly 38.75 meters (127 feet) per pixel.
“If we had binoculars as powerful as this radar, we would be able to sit in Los Angeles and read a dinner menu at a restaurant in New York,” said JPL scientist Marina Brozovic, who led the radar campaign, in the same statement.
This new imagery will grow our understanding of asteroids. Also, using these observations, the teams studying the asteroid hope to figure out its shape; previous observations suggested that Apophis might be shaped like a peanut.
They also want to learn about the asteroid’s rotation rate and its axis spin, which will help predict what orientation the asteroid has with Earth when it flies by in 2029. The close encounter with our planet could harmlessly change the asteroid spin state or cause “asteroid quakes” on the rock’s surface, the team said.
The CNEOS information is fed to NASA’s Planetary Defense Coordination Office, which works with telescopes and institutional partners in the United States and worldwide to get the latest information about threats small bodies may pose to Earth.
Follow Elizabeth Howell on Twitter @howellspace. Follow uson Twitter @Spacedotcomand on Facebook.
On Friday, a large asteroid roughly the size of the Eiffel Tower zipped past the Earth. The asteroid posed no hazard to the Earth on this flyby as it was more than 40 times as far away from Earth as the moon. However, on April 13, 2029, Apophis will get much closer to the Earth.
Scientists considered this week’s flyby a dress rehearsal for 2029, when Apophis will get incredibly close to the Earth. That year, Apophis will get closer to the Earth than some of the highest-orbit satellites surrounding the planet. The asteroid measures 1120 feet wide and is made of rock, iron, and nickel.
Scientists believe it’s shaped roughly like a peanut and its near pass by the Earth on Friday gave them a closer opportunity to inspect the asteroid. Apophis was too far away to be seen by the naked eye so scientists used the NASA Goldstone Deep Space Communications Complex in California and the Green Bank Telescope in West Virginia to image the asteroid it flew by.
The planetary radar study was meant to give researchers a baseline for the significantly closer flyby in 2029. Apophis is expected to get as close as 19,800 miles to Earth on its next pass. Scientists say that Apophis has a very complicated spin state that sees the asteroid spinning and tumbling simultaneously.
Interestingly, during its closest approach in 2029, Apophis will be briefly visible by the naked eye over Western Australia. In that area, the asteroid will be as bright as the stars in the Big Dipper. Its closest pass to Earth will happen at 6 PM EDT on April 13, 2029. It won’t hit the Earth in 2029 or on its next pass in 2036. However, there is a slight chance the asteroid hit the Earth in 2068.
