A future asteroid that threatens Earth may be near-indestructible, scientists concluded in a new study that offered some "aggressive" solutions for what to do if we ever face one. 

Scientists who studied tiny specks of dust recovered from a potentially hazardous asteroid  discovered that “rubble-pile” asteroids, which are loose conglomerations of smaller space rocks, are much more common and robust than previously assumed, a finding that suggests it might take nuclear devices to push them off course from Earth, should the need arise.

In 2010, Japan’s Hayabusa mission stunned the world by becoming the first spacecraft to successfully deliver pristine samples from an asteroid back to Earth. The trailblazing mission collected about 1,500 grains of dust from the surface of Itokawa, a rubble pile asteroid about the same size as the Eiffel Tower that is considered potentially hazardous because its path through space crosses Earth’s orbit.

Now, scientists led by Fred Jourdan, the director of the Western Australian Argon Isotope Facility at Curtin University, have used Itokawa’s dust particles to show that the asteroid may have formed over 4.2 billion years ago from the shattered remains of a “monolithic asteroid,” a type of space rock that is much denser than rubble piles. 

This surprisingly long lifespan indicates that rubble pile asteroids are far tougher than previously assumed, a finding that may necessitate the use of “more aggressive approaches (e.g., nuclear blast deflection)” to knock them off course in the event of a possible collision, according to a study published on Monday in Proceedings of the National Academy of Sciences. 

“Monolithic-type asteroids that are more than a kilometer in diameter have been predicted to have a lifespan of a few 100 million years,” Jourdan and his colleagues said in the study. “However, the durability of rubble pile asteroids is currently not known.” 

“This study shows that the formation age of the rubble pile Itokawa asteroid is older than 4.2 billion years,” they added. “Our results suggest that rubble piles are probably more abundant in the asteroid belt than previously thought and provide constraints to help develop mitigation strategies to prevent asteroid collisions with Earth.”

Jourdan and his colleagues reached this conclusion after examining three dust particles from Itokawa, each of which measures about 150 microns—about the same size as a grain of table salt. The team zoomed in on the tiny grains with spectroscopic instruments and used dating techniques to show that Itokawa has survived catastrophic collisions for almost the entire history of the solar system.

It seems counterintuitive that rubble piles, which are half-empty collections of loose boulders, would be so much tougher than hefty monolithic asteroids. However, a rubble pile asteroid is akin to a “giant space cushion,” Jourdan said in a statement, allowing these rocks to take punch after punch without accruing much damage. 

As a result, rubble piles are probably a lot more common than expected—especially small asteroids under 600 feet—raising the odds that one might crash into Earth in the future. If we were to detect one of these rocks before it hit, we could potentially push it off course by crashing an impactor into it, though we might need to break out the big guns to do it. 

Porous asteroids like Itokawa ”are harder to deflect by kinetic impact since porosity decreases the efficiency of the transfer of momentum,” the team noted in the study. “Here, we showed that small rubble pile asteroids can survive billions of years against the ambient bombardment in the inner solar system due to their resistance to collisions and fragmentations.”

“Therefore, more aggressive approaches (e.g., nuclear blast deflection) might have a higher chance of success against rubble pile asteroids,” the researchers said. This approach would involve setting off a nuclear blast near the asteroid and using the shockwave to redirect its trajectory.

The team noted that NASA’s Double Asteroid Redirection Test (DART) mission, which intentionally crashed into a rubble pile asteroid last year, will help scientists to understand how to protect humanity from these rocks. In addition to securing a safe future for our civilization, Hayabusa’s samples continue to reveal amazing new details about the evolution of Earth, and the solar system. 

“Even though most particles recovered from Itokawa’s surface regolith have a diameter significantly smaller than 100 microns, they provide an invaluable means to study early solar system processes such as the formation of Earth’s oceans and the formation, evolution, and longevity of rubble pile asteroids,” the team noted in the study.

Moreover, Hayabusa’s successor, Hayabusa 2, also returned samples from a rubble pile asteroid in 2020, and NASA’s OSIRIS-REx mission is currently headed back to our planet with its own asteroid haul. These precious deliveries from outer space will continue to expand our understanding of our cosmic past, and help us to preserve our future in a tumultuous universe.

After decades of effort, scientists have finally discovered the secret mechanism that powers the brightest light shows in the universe, which are emitted by absurdly energetic beams that shoot out of explosive galaxies known as blazars, reports a new study. 

The breakthrough was made possible by a new space mission that can see, for the first time, the mind-boggling physics that fuels these astrophysical jets, which are made of ultrafast particles and can shine with the brightness of 100 billion Suns. 

Though our own galaxy, the Milky Way, is in a sleepy phase at the moment, many other “active” galaxies are bursting at the seams with energetic matter that is juiced up by the supermassive black holes that lurk at their centers. Intense interactions between the huge black holes and their gassy surroundings can cause radiant jets to erupt from these galaxies at close to the speed of light; some jets extend for more than a million light years into deep space. 

Blazars are active galaxies with jets that point directly at Earth. These objects are located many millions or billions of light years away, so they don’t pose any risk to our planet, though their jets are so bright that they can be spotted even across those vast distances. Thousands of blazars have been observed by astronomers, but nobody has ever been able to explain the precise mechanisms that made them so overwhelmingly luminous—until now.

Scientists led by Ioannis Liodakis, a Gruber Fellow at the Finnish Centre for Astronomy with the European Southern Observatory at the University of Turku, were able to solve this mystery at last, thanks to the Imaging X-ray Polarimetry Explorer (IXPE), a joint mission between NASA and the Italian Space Agency that launched into orbit in December 2021. 

Liodakis and his colleagues used IXPE to examine an extremely bright blazar called Markarian 501, which is located more than 300 million light years from Earth. Because IXPE is the first mission that can capture a pattern called polarization in X-ray light, the researchers were able to show that the particles in these jets are supercharged by shock fronts, resolving a longstanding “unanswered question” about the dynamics of these brilliant objects, according to a study published on Wednesday in Nature.

“We’ve known about these sources from the 60s,” Liodakis said in an email to Motherboard, referring to blazar jets. “They are among the brightest objects in X-rays and for years we did not know how the X-rays are made. We had a few theories, but the radio and optical data we could get are not able to tell us much.” 

“That is because those come far from the acceleration site, whereas X-rays come right from the heart of the accelerator,” he continued. “They really let us look at the acceleration region and physical conditions there, making them the ideal tool to address our questions.” 

Put another way, each band of the light spectrum tells a different story about the nature of these jets, and scientists have been missing the key X-ray chapter. In particular, researchers have sought to capture the polarization of X-rays in the jets, which is essentially a pattern embedded in the configuration of light waves that contains information about how and where the light was produced. 

While scientists have long been able to study the polarization of blazar jets in many different bands of the light spectrum, only IXPE can resolve these patterns in the kind of high-energy X-ray light that illuminates the initial process that sends the jet particles careening into deep space at unthinkable energies.Liodakis said that the mission has been on the wishlist of astronomers for decades, and that its observations have helped to open “a new window to the Universe” that has enabled scientists to “be able to do the observations and after all those years to directly test our models.”

Indeed, IXPE’s view of Markarian 501, which was captured in March 2022, suggest that the particles in a jet are accelerated when they slam into slower-moving material in the galaxy, which produces a shock wave that spreads through the jet and boosts the particles to incredibly high energy levels. Particles that travel in this wave produce highly polarized X-ray light; as they move beyond it, their emission becomes less polarized.

These results confirm models that predicted the central role of shock waves in powering these  cosmic particle accelerators, which are natural laboratories for studying the behavior of light and matter at extremely high energies. To that end, Liodakis and his colleagues hope that IXPE, and similar instruments, will continue to expose the secrets of blazars and their pyrotechnic jets, including Markarian 501.  

“Our observations were done when Markarian 501 was in sort of an average activity state,” Liodakis said. “Those sources are always active, but there are periods of time that they go into these outbursts that can make them more than 100 times brighter. We are not sure our findings apply in those states.” 

“We have planned more observations that will hopefully take place soon, and we will be able to figure out what is happening in the jets during these outbursts,” he concluded.

Scientists are gaming out the best way to intercept objects that zoom into our solar system from interstellar space, an effort that could provide close-up views of entities that hail from alien star systems. Sending spacecraft to catch up with these interstellar objects, and potentially capture images of them from distances of just a few hundred miles, could reveal important details about their composition, evolution, and their origin beyond our solar neighborhood, reports a new study.

It’s been only five years since the discovery of the first known interstellar visitor—a mysterious 300-foot-wide object known as ‘Oumuamua—which was spotted traveling through the solar system in October 2017. In addition to its sheer novelty, ‘Oumuamua was something of an oddball that puzzled scientists, especially because it underwent a sudden speed boost that still remains unexplained. 

Scientists have presented many natural possible origins for the object, while the Harvard astronomer Avi Loeb has famously suggested that it may have been a piece of alien technology. If an intercept mission had been ready to chase down ‘Oumuamua five years ago, we might have some answers to the tantalizing question of the object’s nature and origin. To ensure we don’t miss our next shot at rendezvousing with a similarly strange object, scientists hope to develop a spacecraft that can lay in wait until it is given the green light to pursue an interstellar target.

Now, a team led by Amir Siraj, a student pursuing astrophysics at Harvard University, have outlined some of the physical parameters of such a mission, including the potential timeline, spacecraft speed, and optimal distance of a flyby. 

Whereas past studies have mapped out the feasibility of the concept, Siraj and his co-authors, including Loeb, investigated the “requirements for a rendezvous mission with the primary objective of producing a resolved image of an interstellar object” and discuss “the characterization from close range of interstellar objects that, like ‘Oumuamua, don’t have an unequivocally identified nature,” according to a forthcoming study in the Journal of Astronomical Instrumentation that was posted on Sunday to the preprint server arXiv.

“We thought that how we could be most helpful to the conversation is by laying out the physical considerations that go into planning an interceptor mission,” Siraj said in a call with Motherboard. “What are the limits, set by physics, you can't get around no matter what?”

“This can be a useful resource for any other team that is putting together specific designs for interstellar object missions,” he continued. “This is basically the physics checklist that the mission needs to satisfy, and this also contextualizes the type of mission that we would need to successfully do this.”

Siraj and Loeb have published many studies about interstellar objects, and have identified two meteors that hit Earth over the past decade that may have been interstellar in origin. The pair are now working on an expedition to try to recover the remains of one of the meteors, which struck in 2014, from the South Pacific seafloor. 

Loeb thinks that it’s possible that both ‘Oumuamua and the 2014 meteor could be artificial in origin, which has provoked pushback from many other scientists who have said there is insufficient evidence for this position. An intercept mission to an interstellar body could shed light on this question, which is why Siraj and his colleagues discuss ways to distinguish between artificial and natural objects. 

“We may anticipate that the spectra of artificial materials of extrasolar provenance may exhibit marked differences with respect to both naturally occurring and human-manufactured materials,” the researchers said in the new study. 

“If the main objective of the mission is to discriminate a possible artificial interstellar probe from a natural asteroid or cometary object,” then using a spectrometer “sensitive to the wavelength range of 0.4 to 2.5 µm may be sufficient, based on reference spectra of various artificial and natural minerals,” they added.

The new study also notes that the Vera C. Rubin Telescope’s Legacy Survey of Space and Time (LSST), a huge 10-year astronomical survey, will be an excellent detector for interstellar objects, and could potentially spot dozens of these visitors. An intercept mission would need to rapidly select one of these potentially abundant targets after its detection, then blast off within weeks in order to have enough time to catch up with it.

“If you're going to go after an interstellar object with a billion dollar spacecraft, you probably want it to look a little bit unusual,” Siraj said. “For an ‘Oumuamua-sized object, it's a couple of months for the trip and for an object 10 times dimmer than ‘Oumuamua, meaning a third of the size of ‘Oumuamua, the trip would be a couple of weeks, so you would need to really decide very quickly.”

For this reason, Siraj and his colleagues suggest parking a spacecraft in Lagrange Point 2 (L2), a stable region in space where the James Webb Space Telescope is currently located. From this spot, a spacecraft could swiftly chase after objects that appear interesting at first glance, though the team noted that a mission could also be parked in orbit around Earth or the Moon, or could launch from the ground. 

The mission would then conduct a flyby of the object, ideally from a distance of several hundred miles, which would reveal invaluable insights about its size, shape, composition, and potential origin. 

The European Space Agency is already developing a Comet Interceptor that will lurk in L2 and might end up pursuing an interstellar object, though the mission is more geared toward rendezvousing with a pristine comet from the outer regions of the solar system. A team of NASA scientists has also presented a “Bridge to the Stars” mission that aims to intercept an interstellar object, but this project remains in the concept phase for now.  

If an official interstellar intercept mission is eventually greenlit in the coming years, it would offer an unprecedented glimpse of an object from beyond the solar system. Meanwhile, the catalog of known interstellar objects will only expand as the LSST and other next-generation observatories scan the skies for these interlopers. Such surveys may reveal whether ‘Oumuamua was really an outlier, or if there are many objects like it wandering through interstellar space. 

“It's remarkable to me that there still isn’t an explanation that doesn't invoke a new type of astrophysical object for ‘Oumuamua,” Siraj said. “That's very motivating for me and, I think, for a lot of scientists.”