If you, like me, have used telescopes to gaze out at the wonders of the Universe, then you too may have been a little captivated by the topic of gravitational lensing. Think about it: how cool is it that the very universe we are trying to explore is actually providing us with telescopes to probe the darkest corners of space and time?
The alignment of large clusters of galaxies is the usual culprit whose gravity bends distant light to give us nature’s own telescopes, but now part-time theoretical physicist Viktor T Toth poses the question, “Can there be multiple gravitational lenses lined up and can they provide a ‘communication bridge’ to allow civilisations to communicate?”
You might have heard of Albert Einstein. In his general theory of relativity, he describes how the presence of matter can distort space around them. The famous analogy of placing a bowling ball at the centre of a large rubber sheet causes a dip centred around the mass of the bowling ball. Any object rolling past the ball would find itself traveling through ‘curved space’ and, therefore, find its path to be altered. This very concept is used successfully by space mission planners to adjust the trajectory of spacecraft exploring the Solar System.
The same concept applies to light as it passes by massive objects like galaxy clusters and is the principle behind the gravitational lens. The first evidence of light being deflected by a massive object was performed in 1919 by Arthur Eddington and Frank Watson Dyson during a total solar eclipse. Gravitational lenses entered the scene 60 years later when they were first observed in 1979 by Dennis Walsh, Bob Carswell, and Ray Weymann using the 2.1m telescope at the Kitt Peak National Observatory.
An artist’s impression of a gravitational lens seen by Hubble. NASA, ESA and D. Player (STScI)
In a fascinating paper authored by Toth he explores the possibility that multiple gravitational lenses might provide extra amplification of light to provide a communication bridge between distant civilisations.
In a conventional gravitational lens, a large mass – such as a cluster of galaxies – sits between a more distant object and the Earth. As the light travels from the distant object, it is bent around the galaxy cluster, providing a lensing effect to astronomers on Earth, allowing them to a) study the distribution of matter in the lensing cluster but also to observe the more distant object a little more easily. Toth proposes that, just like a conventional telescope that uses multiple lenses, a multiple gravitational lens could provide even more amplification than a single system.
Toth explores combinations of multiple gravitational lenses using a variety of methods but focuses (sorry) attention on a two-lens system (so-called gravitational lens bridge), which is aligned along the central axis of the system, but found no advantages and no additional signal amplification over the results from a single lens system. In addition, photon mapping techniques were applied with the same outcome; a double-lens system offers no advantage over a single-lens system.
Applying the wave theory of light to the same two-lens system revealed the same results, but using computer graphics to perform ray tracing (which cannot be used to estimate amplification) can help to highlight visual features other techniques would be unable to produce. Using this approach, it suggested a two-lens system would produce two concentric Einstein rings; however, they would be very difficult to detect in real-world scenarios.
In summary, then, a fascinating concept, especially the possibility of using a lens bridge for communication with distant civilisations, but the results are less than promising. Yes, there may well be double gravitational lenses, but as this paper shows, it is unlikely we will be able to detect them for now and sadly I suspect the idea of using them as a long-distance cosmic telephone will for now remain science fiction.
What’s going on with Betelgeuse? In recent years it’s generated a lot of headlines as its luminosity has shifted dramatically several times. The red supergiant brightened by almost 50% earlier this year, triggering speculation that it may go supernova.
But new research suggests there’s something completely different happening with Betelgeuse that has nothing to do with its recent fluctuations. It may have consumed a smaller companion star.
Listen, when a star like Betelguese brightens and dims to such great extents, humans are bound to sit up and take notice. That’s because it’s a red supergiant and will certainly blow up as a supernovae. But there’s no need to run out and get more tinfoil for our protective head gear. It’s too far away to hurt us, but would be one heckuva light show.
Unfortunately for the spectacle-seeker inside all of us, none of the star’s recent luminosity fluctuations mean its explosion and destruction are imminent. Instead, the changes have been attributed to dust clouds and the star’s regular pulsations.
Some new research can’t explain Betelgeuse’s recent fluctuations, but it suggests something else happened with our supergiant neighbour in its past. The new study is “Betelgeuse as a Merger of a Massive Star with a Companion.” The lead author is Sagiv Shiber from the Department of Physics and Astronomy at Louisiana State University.
But did Betelgeuse have a companion?
You can’t miss Betelgeuse. It’s the red star on Orion the Hunter’s shoulder in this stunning image from astrophotographer Rogelio Bernal Andreo. Humanity’s been gazing at it since antiquity. Image Credit: By Rogelio Bernal Andreo – https://ift.tt/2YJvV3L, CC BY-SA 3.0, https://ift.tt/qb9UQN4
“It has been firmly established that the majority of massive stars exist within binary systems,” the authors write. Many of them will experience binary interactions at some point during their evolution. Sometimes, though rarely, the stars can merge. Is that why Betelgeuse is alone?
When a merger happens, a lot depends on the respective masses of the stars. There can be transient “merge-bursts,” mass loss, as well as other phenomena.
This is all determined by simulations in the new research. The researchers simulated a merger between a 16 solar mass star and a smaller 4 solar mass star. (Betelgeuse is between 16 and 19 solar masses.) The simulations show that as the stars move closer together and share a common envelope, eventually the minor star merges with the primary star’s helium core. “The companion eventually plunges into the envelope of the primary, leading to its spin-up and subsequent merger with the helium core,” the authors explain. That causes an exchange of both orbital and thermal energy. Eventually, it triggers a powerful pulse that travels from the core through the primary star’s envelope.
But it doesn’t stop there. Sometimes, it can also trigger mass loss. That happens because of the release of gravitational energy caused by the merger. That energy has to express itself somehow, and it’s converted into kinetic energy that drives high-speed mass flow away from the primary. In the team’s simulations, the mass loss reached as high as 0.6 Earth masses.
This figure from the study is a rendering of the mass loss coming from the simulated merger. From left to right, top to bottom, they show the gas at 7, 10, 14, 21, 27, and 40 days after the merger. Red is the most dense gas and blue is the least dense. Image Credit: Shiber et al. 2023.
But when it comes to Betelgeuse, the evidence for a merger sometime in the past may be in the star’s rotation. It rotates at about 5.5 km/second. For reference, our Sun rotates at about 2 km/second. “For instance, studies on Betelgeuse have demonstrated that a previous merger between a pre-main sequence massive star with a mass of approximately 15~17M Earth masses and a low-mass mainsequence companion with a mass of around 1 ~ 4M Earth masses could account for its implied high rotation rate,” the paper states.
The merger doesn’t interrupt the primary star’s evolution into its Red Super Giant (RSG) phase. But it does eject material, often through polar outflows. The gas can travel as fast as 200-300 km/s, which is characteristic of mergeburst events.
There’s precedent for this type of merger in V838 Monocerotis. It was a possible luminous red nova, a stellar explosion caused by the merger of two stars. It was unremarkable until 2002 when it suddenly brightened, and was one of the largest known stars for a period of time after the purported merger. A 2007 paper concluded that the mergeburst was the only explanation for V838 Monocerotis’ brightening and expansion.
This Hubble Space Telescope image shows the light echo of dust illuminated by nearby star V838 Monocerotis as it became 600,000 times more luminous than our Sun in January 2002. That may have been a mergeburst created when the star merged with and consumed a smaller star. Credit: NASA/ESA
So, is this what happened with Betelgeuse? Did it merge with and consume a smaller companion, leaving no trace? It’s implied rotation rate supports that conclusion, as does the star’s chemical composition.
This study can’t reach that conclusion, but it’s a distinct possibility. There’s a lot astrophysicists don’t yet know about these mergers and their effects. The size of the stars’ envelopes and eventual common envelope affects the eventual spin-up rate of the surviving primary. And the amount of mass loss can dispel different amounts of kinetic energy, so there’s a lot going on.
The authors made some progress in understanding these events, but they need improved methods and tools to understand them more completely.
“By delving deeper into the physics of stellar mergers, we aim to advance our understanding of massive star evolution, the properties of supernova progenitors, and the role of mergers in shaping the astrophysical transient landscape,” they write.
There’s no indication that this merger, if it occurred, is directly connected to Betelgeuse’s recent fluctuations, or to its eventual explosion as a supernova. But one day, Betelgeuse will explode. If humanity lasts long enough, then many future generations of scientists will be fortunate enough to watch the whole process play out. Then we may finally have answers.
But for now, the red supergiant keeps generating headlines.
According to new research we can start writing the eulogy for four exoplanets around a Sun-like star about 57 light years away. But there’s no hurry; we have about one billion years before the star becomes a red giant and starts to consume them.
The star is Rho Coronae Borealis, a yellow dwarf star like our Sun. It’s in the constellation Corona Borealis, and has almost the same mass, radius, and luminosity as the Sun. But where the Sun is about five billion years old, RCB is twice that, which means its red giant phase is looming, at least in astrophysical terms.
A new paper appearing in The Astrophysical Journal presents these results, and asks some questions about what happens to exoplanets in a star’s habitable zone when the star becomes a red giant. The paper is “Planetary Engulfment Prognosis within the Rho CrB System,” and the sole author is Stephen R. Kane, from the Department of Earth and Planetary Sciences, University of California, Riverside.
“Post main sequence stellar evolution can result in dramatic, and occasionally traumatic, alterations to the
planetary system architecture, such as tidal disruption of planets and engulfment by the host star,” Kane writes. Rho Coronae Borealis is both old and bright, making it “… a particularly interesting case of advanced main sequence evolution,” according to Kane. Not only because its similar to the Sun and easily observed, but also because it hosts four exoplanets.
Kane used stellar evolution models to try to determine Rho Coronae Borealis’ future, and the future of its planets. In 1 to 1.5 billion years, the star will leave the main sequence and become a red giant. Red giants can swell to epic proportions, and some can expand to one billion km in diameter. When our Sun becomes one in several billion years, it’s bloated form will likely consume or at least destroy all of the inner planets.
Rho CrB is no different.
It has four known exoplanets named Rho Coronae Borealis b, c, d, and e. They’re named in order of discovery, not distance from the star. The three planets in the most danger are e, b, and c, the closest planets to the star.
This figure from the study shows the Rho CrB System and its four planets. The inner edge of the optimistic habitable zone is shown in green, just beyond the orbit of the otuermost planet d. Image Credit: Kane 2023.
The four planets range in mass from super-Earth to Jovian. All of them are much closer to the star than Earth is to the Sun, and the two innermost planets are closer to their star than Mercury is to the Sun. They’re tightly-packed into their inner solar system, and this is what spells their doom.
This table shows the basic facts about the four exoplanets around Rho CrB. It shows their orbital period, P, semi-major axis, a, eccentricity, e, argument of periastron, w, and the minimum planetary mass, Mp sin i. Image Credit: from Brewer et al. 2023.
The research shows that e,b, and c are in the worst position. Rho CrB can totally engulf these three planets.
The engulfment of planets by an expanding star can have different outcomes depending on the overall architecture of the system. Planets can take decades to spiral in toward the star. On the way, they can be destroyed by evaporation. They can also destroyed by tidal disruption when they meet the Roche limit. In that case, they add to the star’s bulk, helping it puff up even more.
For sub-Jupiter mass planets between 3 to 5 AU, their fate is sealed according to some research. There’s no escape. But for others, despite the dire circumstances, there might be a way out.
Sometimes, scientific models show, planets start to interact in different ways gravitationally with one another as the star swells. As the star expands, it’s also losing mass as it continues to fuse material. This creates tidal effects in the system, and in some cases, it can drive planets into mean motion resonances, and also drive them further from the star. So, there’s a potential escape route. It’s difficult to determine so far in advance what exactly might happen, though.
But if some do survive, researchers think they can survive as the star leaves the Red Giant Branch (RGB) behind. They may even survive as the star enters the Asymptotic Giant Branch (AGB) phase. The AGB phase is similar to the RGB phase, but RGB stars have slightly different chemistries in their cores and their shells. But the details of the star aren’t that critical to the fate of the planets.
There’s a possible escape route for some of the planets, but the same tidal interactions that can rescue a planet can also work against it. Interactions can drive a planet inward toward the star too, to an earlier demise. Researchers are actively trying to understand all of these process by watching stars that are leaving the main sequence.
To understand what might happen in the Rho CrB system, Kane plotted the star’s future mass, luminosity, and radius.
This figure shows how Rho CrB will change over time. The dotted line represents the star’s current age, with the grey region representing the uncertainty of the age. The top panel shows mass, middle panel shows radius, and the bottom panel shows luminosity for the star as it transitions through the RGB, horizontal branch, and AGB. Image Credit: Kane 2023.
Kane also plotted the changes the star will go through alongside the positions of the four exoplanets. That puts the peril the planets face in stark relief.
It doesn’t look good for the four exoplanets orbiting Rho CrB. As the blue line representing the star shows, the RGB phase isn’t one smooth expansion. There are pulses and expansions as shells burn and different chemicals are dredged up from the core to the surface. Image Credit: Kane 2023.
So how much detail can models and simulations provide when it comes to the specifics of Rho CrB and its planets?
“Although all of the planets will enter the stellar atmosphere of Rho CrB, their individual prognoses vary considerably,” Kane explains.
Planet e, the innermost planet, is likely terrestrial. It’ll be the first to go and will probably evaporate as the star engulfs it deeply. It’s demise could be swift.
Planet b is the most massive of all four, at almost 350 Earth masses. It’s more massive than Jupiter, and as it enters the star’s expanding atmosphere, drag will cause it to in-spiral. Its fate is tidal disruption, as it simply won’t be able to hang onto itself.
Planet b’s fate can feed into planet c’s fate. If planet b’s material makes the star swell enough, that could hasten planet c’s demise by engulfment. The same stellar swelling and radial expansion could also hasten planet d’s demise by engulfment, all before the star leaves its RGB phase behind.
Planets c and d are both about Neptune-mass, and they would likely lose their mass by evaporation as they spiral in toward the star.
Unfortunately, the modelling did not account for orbital dynamics. But it’s possible that one planet could escape all of this mayhem. Planet d is the lone world with a chance to escape. “Our model further did not include the effects of orbital dynamics, which has the potential to cause planet d to migrate further outward and possibly escape engulfment,” Kane writes. If it does, it has a chance to survive for a lot longer, possibly in a newly-established habitable zone.
Artist’s impression of the structure of a solar-like star and a red giant. The two images are not to scale – the scale is given in the lower right corner. In red giants, the convection zone is much larger, encompassing more than 35 times more mass than in the Sun. Image Credit: By ESO – https://ift.tt/9kwdWMx, CC BY 4.0, https://ift.tt/t0zr8wN
That’s possible, but not likely in this case. “Since the inner planets of Rho CrB are engulfed prior to the AGB phase, it is unlikely that orbital dynamics will play a major role in the system during and after the stellar mass loss,” he writes.
There’s no way to know for certain what will happen in this system. But astrophysicists are busy watching other solar systems for clues. There’s not much observable evidence for engulfment so far, but that doesn’t mean it’s not happening.
“Thus far, observational evidence for planetary engulfment signatures has remained relatively sparse, suggesting that either engulfment scenarios are rarer than expected, or that signature detection is more challenging than anticipated,” the paper states.
The detailed specifics of Rho CrB may be beyond our observational reach or the reach of our simulations and models, for now. But there’s no denying the potential catastrophic consequences.
“The evolution of stars through their progression on the main sequence, expansion into a giant star, and then final contraction into a white dwarf, has profound consequences for the orbiting planets,” Kane writes. “Given the masses and semimajor axes of the four known planets, we predict that planet e will evaporate within the stellar atmosphere, planet b will in-spiral and be tidally disrupted, potentially further inflating the star, and planet c will be evaporated within the stellar atmosphere.”
This diagram shows the evolution of stars under most circumstances. It shows how the Sun will become a Red Giant, then a planetary nebula, then a white dwarf. (It’ll never be a type 1a supernova because those only occur in binary systems.) Credit: NASA
Planet d’s fate is a little less certain, but it’ll likely be destroyed, too. It’ll probably evaporate within the star at the end of the AGB phase.
It’s possible that there are other planets within the habitable zone that haven’t been detected. If there are, they can survive the stellar evolution on the inside of the HZ’s inner edge during the RGB/AGB phase. But after that, the star will be a white dwarf. These planets, if they exist, will be well outside of the new HZ at that time.
Part of understanding what happens to solar systems when their stars leave the main sequence lies in an accurate picture of their planet populations. Giant planets on distant orbits can affect the fate of inner system planets, potentially changing their orbits and moving them to safer distances.
Those types of planets are difficult to detect with the transit method, but improved radial velocity measurements in the future could find more of them.
This research is particularly interesting because our own Sun will become a red giant, and eventually a white dwarf. What will happen to our home?
It’s not known, but the Earth is in jeopardy. It could be destroyed, or it could migrate further outward. Either way, our Solar System will never look the same.
Fortunately, it’s so far in the future that it’s merely a curiosity to us.
Astronomers are currently pushing the frontiers of astronomy. At this very moment, observatories like the James Webb Space Telescope (JWST) are visualizing the earliest stars and galaxies in the Universe, which formed during a period known as the “Cosmic Dark Ages.” This period was previously inaccessible to telescopes because the Universe was permeated by clouds of neutral hydrogen. As a result, the only light is visible today as relic radiation from the Big Bang – the Cosmic Microwave Background (CMB) – or as the 21 cm spectral line created by the reionization of hydrogen (aka. the Hydrogen Line).
Now that the veil of the Dark Ages is being slowly pulled away, scientists are contemplating the next frontier in astronomy and cosmology by observing “primordial gravitational waves” created by the Big Bang. In recent news, it was announced that the National Science Foundation (NSF) had awarded $3.7 million to the University of Chicago, the first part of a grant that could reach up to $21.4 million. The purpose of this grant is to fund the development of next-generation telescopes that will map the CMB and the gravitational waves created in the immediate aftermath of the Big Bang.
Gravitational waves (GW), originally predicted by Einstein’s Theory of General Relativity, are ripples in spacetime caused by the merger of massive objects – like black holes and neutron stars. Scientists have also theorized that there are GWs formed during the Big Bang that could still be visible today as vibrations in the background. In collaboration with the Lawrence Berkeley National Laboratory (LBNL), researchers from the CMB-S4 project University of Chicago seek to build telescopes and infrastructure in Antarctica and Chile to search for these waves.
Illustration of the Big Bang (left), the distortion caused by Dark Matter and galaxies (wavy lines), and the warped light received by the Atacama Cosmological Telescope (right). Credit: Lucy Reading-Ikkanda/Simons Foundation/ACT Collaboration
The collaboration currently involves 450 scientists from over 100 institutions in 20 countries. The entire project is proposed to be jointly funded by the NSG and the U.S. Department of Energy (DoE), with the NSF’s portion being led by the University of Chicago, while Lawrence Berkeley National Laboratory will lead the DoE portion. The project is expected to cost a total of about $800 million and become operational by the early 2030s. In addition to searching for primordial GWs, these telescopes could also map the CMB in incredible detail and reveal how the Universe has changed over time.
These telescopes could also help search for the elusive “Dark Universe” and validate our current cosmological models. John Carlstrom is the Subrahmanyan Chandrasekhar Distinguished Service Professor of Astronomy and Astrophysics and Physics at UChicago and the project scientist for CMB-S4. “With these telescopes, we will be testing our theory of how our entire universe came to be, but also looking at physics at the most extreme scales in a way we simply cannot do with particle physics experiments on Earth,” he said in a UChicago News statement.
Because the CMB carries information about the birth of the Universe, scientists have been mapping it for decades. These include space-based telescopes like the Soviet RELIKT-1, NASA’s Cosmic Background Explorer (COBE), the Wilkinson Microwave Anisotropy Probe (WMAP), and the ESA’s Planck satellite. These missions have measured small temperature anisotropies (fluctuation) in the CMB with increasing detail, providing hints about how the Universe began. What is needed, however, are telescopes sensitive enough to answer the deeper cosmological questions, like whether the Universe began with a burst of inflation.
To this end, the CMB-S4 will build incredibly complex instruments to map the first light of the Universe from spacecraft and the ground. The array will include two new telescopes in the Chilean Atacama Plateau and nine smaller ones at the NSF’s South Pole Station (SPS). The project will also rely on the South Pole Telescope, which has been operational at the SPS since 2007. Each site will play an essential role, with the telescopes in Chile conducting a wide survey of the sky to capture a more detailed picture of the CMB. Meanwhile, the telescopes at the NSF’s South Pole Station would take a deep, continuous look at a smaller part of the sky.
The observations from Chile will help improve our understanding of the evolution and distribution of matter and look for relic light particles that may have existed in the early Universe. Meanwhile, the telescopes in Antarctica will offer a unique look at the Universe since it is here that the rest of the Earth spins around, permitting continuous observations of one section of the sky. Their combined efforts will allow astronomers to look for the ripples in spacetime that could only emerge from a space smaller than a subatomic particle suddenly expanding into a much larger volume.
Said Lawrence Berkeley National Laboratory physicist Jim Strait (the project director for CMB-S4), this is an ambitious but worthwhile goal. “In many ways, the theory of inflation looks good, but most of the experimental evidence is somewhat circumstantial,” he said. “Finding primordial gravitational waves would be what some people have called ‘the smoking gun’ for inflation.”
Since these ripples would interact with the CMB and leave a distinct (but extremely faint) signature, large-scale and continuous mapping of the CMB should provide indications of their existence. The CMB-S4 should also provide clues about the nature of Dark Matter and Dark Energy. Whereas the former is theorized to account for the majority of the mass in the Universe (about 69%), the latter is responsible for its accelerating rate of expansion. Furthermore, mapping primordial gravitational waves would also help scientists find the connection between the forces of gravity and quantum mechanics.
Microwave detectors are already so sensitive that measurements are dominated by background noise and local interference. Therefore, the plan is to outfit the combined CMB-S4 experiment with nearly 500,000 superconducting detectors, more than all previous experiments combined, and to greatly increase the number of measurements to provide a precise measurement of the signal level and reduce the noise. The new grant from the NSF will help fund the design of the new telescopes and site infrastructure, which will be the most complex ever built.
Astronomers have discovered two known interstellar objects (ISO), ‘Oumuamua and 21/Borisov. But there could be thousands of these objects passing through the Solar System at any time. According to a new paper, the upcoming Vera Rubin Telescope will be a fantastic interstellar object hunter, and could possibly find up to 70 objects a year coming from other star systems.
The Rubin Observatory is a ground-based telescope located high in the Chilean Andes. It is expected to see first light sometime in 2025, a timeline that has already been pushed back a few times. The observatory’s 8.4-meter Simonyi Survey Telescope will take images of the sky using the highest resolution digital camera in the world, a 3,200-megapixel camera that includes the world’s largest fish-eye lens. The camera is roughly the size of a small car and weighs almost 2800 kg (6200 lbs). This survey telescope is fast-moving and will be able to scan the entire visible sky in the southern hemisphere every few nights.
One of the main projects for Rubin Observatory is the Legacy Survey of Space and Time (LSST), expected to last at least 10 years. Researchers anticipate this project will gather data on more than 5 million asteroid belt objects, 300,000 Jupiter Trojans, 100,000 near-Earth objects, and more than 40,000 Kuiper belt objects. Since Rubin will be able to map the visible night sky every few days, many of these objects will be observed hundreds of times.
Because of the telescope’s repeated observations, there will be an enormous amount of data to calculate the positions and orbits of all these objects. With all that data and mapping, it is expected that Rubin will be able to detect faint interstellar objects – and these speedy ISOs might even actually stand out among all the other objects. Basically, the LSST will be able to capture a timelapse view of interstellar objects on their fast journeys through our Solar System.
‘Oumuamua (l) and 2I/Borisov (r) are the only two ISOs we know of for certain. Image Credit: Left: By Original: ESO/M. Kornmesser; right, Hubble Space Telescope/NASA/ESA.
Various estimates and predictions have been coming from various astronomers about how many interstellar objects Rubin will be able to detect. One estimate said five a year, another 7, another 21.
A new pre-print paper published on arXiv suggested that LSST could find up to 70 interstellar objects every year. “The annual rate at which LSST should discover ’Oumuamua-like interstellar objects ranges from about 0?70 detected objects per year,” write astronomers Dusan Marceta and Darryl Z. Seligman.
To come up with this number, they applied recently developed tool called the Object In Field (OIF) algorithm.
A rendering of the LSST Camera with a cut away to show the inner workings. Credit: LSST.
“It serves as an observation generator that simulates a real LSST campaign,” Marceta told Universe Today via email, “providing time and coordinates for every LSST field of view (FOV) and exposure time. It also allows for the inclusion of an arbitrary population of moving solar system objects, such as asteroids or comets. It then propagates their motion, determines their positions in the sky, and detects whether some of them appear in the mentioned FOVs.”
Marceta, a professor at the University of Belgrade said that they developed a method to generate a population of interstellar asteroids and utilized the OIF to assess how many of these objects can be detected by LSST under various conditions.
“Given the unconstrained nature of the interstellar objects’ population, we considered a wide range of possibilities for critical parameters,” he said. “This encompassed size distributions, the range of albedo, and their assumed motions in interstellar space. Taking all these factors into account, we arrived at a range of 0-70 objects per year.”
This assumes that at least that many interstellar objects actually exist. Marceta said they assumed a number density of 0.1 object per cubic astronomical unit, a value implied by the detection of ‘Oumuamua, “which remains highly uncertain, similar to other parameters associated with this population,” he said.
However, because ISOs move so fast, they might be easier to detect with the Rubin Observatory because of an effect called ‘trailing loss.’
“It’s an effect that occurs when a rapidly moving object is within the telescope’s FOV,” Marceta explained. “To excite a pixel on the CCD, a certain number of photons must land on it during the exposure time (which is 15 seconds in our simulations). For stationary objects like stars, all photons during the exposure time hit the same area of the CCD. However, for an object that changes its position during the exposure time, the photons land on different pixels as it moves.”
The complete focal plane of the future LSST Camera is more than 2 feet wide and contains 189 individual sensors that will produce 3,200-megapixel images. Crews at SLAC have now taken the first images with it. (Jacqueline Orrell/SLAC National Accelerator Laboratory)
Marceta said that even if the total number of photons may be sufficient to excite a pixel, if they are spread across a large number of pixels, it’s possible that none of the pixels receive enough photons to exceed the background noise.
“The faster the object moves, the greater the number of pixels that receive the photons, making trailing loss more noticeable,” he said. “Our simulation shows that interstellar objects can appear in the telescope’s field of view with velocities significantly exceeding those of the fastest solar system populations, which makes this issue particularly important.”
But of course, this is a chicken-and-the-egg type conundrum. Because of a sample size of only two, scientists can now only make loose predictions of how many interstellar objects Rubin will reveal. Once a larger sample of interstellar objects are able to be counted and analyzed, astronomers will have a much better idea of the population of these objects … which will likely only happen after the Rubin Observatory is up and running.
But Marceta and Seligman are hopeful that Rubin and the LSST will change everything.
“It is possible that the number density of ‘Oumuamua-like objects is higher than currently estimated due to a large fraction of interstellar objects currently undetectable due to trailing loss and rapid sky motions,” they write.
The more we can find, the better, because some of these will be in the perfect trajectory for an interstellar interceptor mission. Learning details about objects from other solar systems could fundamentally change our view of the universe and our place in it.
The Crab Nebula – otherwise known as the first object on Charles Messier’s list of non-cometary objects or M1 for short – has never really failed to visually underwhelm me! I have spent countless hours hunting down this example of a supernova remnant and found myself wondering why I have bothered. Yet here I am, after decades of looking at it, and I still find it one of the most intriguing objects in the sky.
Never has this interest been piqued more than right now after another mirror-smashing beauty of an image from the James Webb Space Telescope, and it’s already found its way to my mobile phone wallpaper!
The NASA/ESA/CSA James Webb telescope was launched back in December 2021, and from its position 1.5 million km away, it orbits the Sun, giving us a brand new window out into the Universe. Using its Near-Infrared Camera (NIRCAM) and the Mid-Infrared Instrument (MIRI) JWST has been exploring the Crab Nebula, the remains of a star whose explosion was recorded back in 1054. The object, which is 6,500 light years away, can be seen in small amateur telescopes and is without doubt one of the most studied supernova remnants of all.
Despite being the target of many, many observations, there are still plenty of unanswered questions about the nature of the star that exploded, the mechanics of the explosion itself, and the composition of the ejecta. Using JWSTs infrared capabilities, the image of the Crab reveals red/orange filaments of dust around the central region. The filaments weave an intricate pattern over the whole nebula, but it’s the core that has received more attention.
Compare and contrast the Hubble version on the left with the new, Webb version on the right. Credit: NASA, ESA, CSA, STScI, T. Temim (Princeton University)
It has been known that there is a pulsar at the core of the nebula, and it’s this pulsar that is the true remains of the progenitor star. When it went ‘supernova,’ the core collapsed to form the ultra-dense rotating object that, if you happen to be in the right place in space (hey, that rhymes), then you will see a pulse of radiation as it rotates. The infrared images from JWST reveal synchrotron emissions, which are a direct result of the rapidly rotating pulsar. As the pulsar rotates, the magnetic field accelerates particles in the nebula to astonishingly high speeds such that they emit synchrotron radiation. As a fabulously lucky quirk of nature, the radiation is particularly obvious in infrared, making it ideal for JWST.
Not only has JWST detected synchrotron radiation, but it has also mapped out locations of dust particles and even… locations where dust particles are forming. It’s fabulous to think that an object that was discovered almost a thousand years ago is still surprising us. That’s one of the things I love about astronomy: you think you have seen it all, but there is always more to learn. Over the coming years, teams of astronomers using both HST and JWST will continue to probe the depths of the Crab Nebula, and maybe one day, all of its secrets will finally be revealed.
Every year, NASA’s Breakthrough, Innovative, and Game-Changing (BIG) Idea Challenge invites student innovators to build and demonstrate concepts that can benefit future human missions to the Moon and beyond. This year’s theme is “Inflatable Systems for Lunar Operations,” which could greatly reduce the mass and stowed volume of payloads sent to the Moon. This is critical for the Artemis Program as it returns astronauts to the Moon for the first time since the Apollo Era over fifty years ago. It will also reduce the costs of sending payloads to the Moon, Mars, and other deep-space destinations.
Despite decades of growth and development, the greatest challenges for sending crewed missions to space remain volume and mass limitations. Like it or not, launches are still subject to the Rocket Equation, which creates a vicious cycle where larger payloads require more propellant to break free of Earth’s gravity. This, in turn, means larger rockets with heavier propellant tanks, and so on. As such, large structures cannot be placed on the lunar or Martian surface without complex deployment mechanisms and on-site assembly.
NASA has explored multiple solutions to this problem, which include using local resources to create building materials and provide for astronaut needs – aka. In-Situ Resource Utilization (ISRU). This has the advantage of reducing the amount of supplies astronauts will need to bring with them while reducing dependency on resupply missions. Another solution is to send large, inflatable systems, which are low-mass and can be tightly packed into payload fairings. Once they reach their destination and are inflated, they expand to become many times their stowed volume.
Along with advanced fabrics and internal pressure stiffening, inflatable systems can offer robust habitats and environmental protection against harsh extraterrestrial conditions. This is the purpose of the 2024 BIG Idea Challenge, where collegiate-level teams are tasked with designing habitats that incorporate inflatable components. These range from towers, gantries, and antennas to soft robotics, actuators, connectors, deployment mechanisms, airlocks, and temporary shelters. Niki Werkheiser, Director of Technology Maturation at NASA’s STMD, said in a recent NASA press release:
“This challenge is particularly exciting because it applies out-of-the-box thinking to the design and engineering processes that will be required to incorporate inflatable components into space missions. Harnessing the impressive creativity demonstrated by this collegiate cohort could present truly novel solutions for future space exploration.”
Finalists will be selected by a panel of NASA and industry experts who will evaluate the proposal and video package of mission scenarios that incorporate inflatable systems. The five to eight terms selected will receive a stipend of between $50,000 and $150,000, including expenses for hardware, materials, testing equipment, software, etc. The teams will spend the next nine months further developing, refining, and testing their proposals and preparing a 15-20 page technical write-up detailing their results. This will be followed by the annual BIG Idea Forum next Fall, where they will be invited to present their concepts for a technical design review.
Promotional poster for the 2023 Lunar Forge Challenge. Credit: NASA
This will include proof-of-concept demonstrations in analog test environments that simulate lunar conditions. Said Tomas Gonzalez-Torres, the space grant project manager for NASA’s Office of STEM Engagement:
“When it comes to mission-critical technology for upcoming space exploration efforts, academia is an important partner. Collegiate-level teams push the envelope in terms of creativity but also in demonstrating technology readiness for innovative ideas. These ideas can be infused into technology development at micro and macro scales.”
This year’s competition compliments the 2023 Lunar Forge Challenge, where undergraduate and graduate students were awarded up to $180,000 to design, develop, and demonstrate technologies that will enable the production of lunar infrastructure through ISRU-derived metals. These and other technologies will be crucial to the Artemis missions and the long-term goals that NASA, fellow agencies, and commercial partners have to establish permanent infrastructure on the Moon. In addition to fostering lunar exploration, research, and possibly settlement, these efforts will enable future missions to Mars and beyond.
To learn more about the 2024 BIG Ideas Challenge and how you may enter, check out the BIG Idea website at bigidea.nianet.org.
The Fomalhaut system is nearby in astronomical terms, and it’s also one of the brightest stars in the night sky. That means astronomers have studied it intensely over the years. Now that we have the powerful James Webb Space Telescope the observations have intensified.
The Fomalhaut system has a confounding and complex dusty disk, including a dusty blob. The blob has been the subject of an ongoing debate in astronomy. Can the JWST see through its complexity and find answers to the systems unanswered questions?
Like all stars this bright, Fomalhaut has been known since antiquity. Its name comes from ancient Arabic and means “mouth of the <southern> fish.” That makes sense, since it’s in the Piscis Austrinus (Southern Fish) constellation. Its designation is HR 8728, but in 2016 the IAU officially named it Fomalhaut.
Fomalhaut is the brightest star in the constellation Piscis Austrinus. Image Credit: By IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg) – [1], CC BY 3.0 https://ift.tt/3iH7hkD
Fomalhaut is young, only around 440 million years old. But it’s consuming its hydrogen at a furious rate and may only last about one billion years. That’s not very long in a Universe where some stars will last for trillions of years. Fomalhaut has two close friends, the K-type main-sequence star TW Piscis Austrini, and the M-type, red dwarf star LP 876-10. Together they’re a trinary star system.
In our modern age, astronomers have examined Fomalhaut and its complex disk. There’s something dense in the disk, and astronomers have struggled to identify exactly what it is. A team of researchers observed the Fomalhaut system with the JWST’s NIRCam instrument and coronagraph and published their results in the paper “Searching for Planets Orbiting Fomalhaut with JWST/NIRCam.”
In 2008, astronomers discovered a planet orbiting Fomalhaut and it took the conventional name Fomalhaut b. Then in 2012 the Hubble confirmed the object with its Advanced Camera for Surveys. But since then, there’s been an ongoing debate about the object as different researchers examined the evidence and the Fomalhaut system. The idea that Fomalhaut b was an exoplanet has fallen out of favour.
In 2012, Hubble Space Telescope observations seemed to confirm the existence of Fomalhaut b, but since then, the exoplanet hypothesis has fallen out of favour. Image Credit: NASA/HST
Since then, the scientific consensus on the blob in the star’s disk is leaning away from the exoplanet hypothesis towards the idea that it’s a debris cloud. The debris could may have come from a collision between two exoplanets, and the cloud may be on an escape trajectory.
One of the difficulties in understanding the system is all of the dust. It makes observations difficult. But the JWST was built for just this situation. It can see through dust much more effectively than other telescopes with its keen infrared vision.
Webb’s strength lies in its pair of instruments and their filters. NIRCam can see through dust and can see ionized gas, while MIRI can see the dust itself. Add in their filters, and astronomers can “tune” the JWST to different parts of the infrared spectrum.
This new research isn’t the first time the JWST has examined Fomalhaut. In May 2023, a team of researchers used the JWST’s MIRI to probe the complex dust environment around the star. They discovered a new intermediate dust belt that might be shepherded by an unseen planet. That research suggested that the blob, Fomalhaut b, could’ve originated in this belt.
That research also found evidence for another dust-creating collision. “We also discovered a large dust cloud within the outer ring, possible evidence of another dust-creating collision,” the paper states. “Taken together with previous observations, Fomalhaut appears to be the site of a complex and possibly dynamically active planetary system.”
This image shows how the JWST’s MIRI instrument identified a new intermediate gap in Fomalhaut’s complex dust ring. The two bottom panels show the newly-detected dust cloud in two of MIRI’s filters, and the upper panel shows the previously-discovered cloud that was once thought to be an exoplanet. Image Credit: Gaspar et al. 2023.
The new research includes some of the same researchers, and this time they used the JWST’s NIRCam instrument to probe the complex dust ring in different wavelengths of infrared light. This pair of studies perfectly illustrates the JWST’s power and effectiveness.
These new observations seem to put the nail in the coffin for the potential-exoplanet-formerly-known-as-Fomalhaut b. “Consistent with the hypothesis that Fomalhaut b is not a massive planet but is a dust cloud from a planetesimal collision, we do not detect it in either F356W or F444W (the latter band where a Jovian-sized planet should be bright),” the authors write.
So it’s a final farewell to Fomalhaut b. Or is it?
In the new observations with NIRCam and NIRSpec, the researchers detected 10 sources in the complex dusty rings. They’re consistent with coronagraphic images from the HST and the Keck Telescope. “We show them to be background objects, including the ‘Great Dust Cloud‘ identified in MIRI data,” they write.
But one of the 10 objects has no counterpart in previous observations. It’s at the edge of the inner dust ring.
This image from the research shows NIRCam’s findings lain over a MIRI image of the Fomalhaut’s dusty ring system. #7 is the newly-detected object, while the other objects were found with Keck and the HST. The dotted circle shows where Fomalhaut b should be, but NIRCam found no evidence of it. Image Credit: Ygouf et al. 2023.
So what is #7? Is it the new Fomalhaut b?
“What is most intriguing about this object, the only NIRCam object that cannot be immediately associated with a background source, is its proximity to the inner dust disk newly identified in the MIRI imaging,” the authors write. According to the research, if this is an exoplanet, it’s about the same mass as Jupiter. If it is a planet, “it should have substantial dynamical interactions with the inner debris disk,” they explain, but they don’t see any evidence of that in these images.
“It will be important to address its possible effects on the structure of the inner disk if its planetary nature is confirmed,” they write.
As this whole fascinating saga shows, confirming exoplanets in dusty rings like this is difficult. Yet it’s inside these rings that planet formation takes place, and there’s a lot we don’t know about the process. It’s one of the reasons the JWST was built.
These JWST observations can’t confirm this new planet, but it may not be finished with the system yet. “Whether this object is a background galaxy, brown dwarf, or a Jovian mass planet in the Fomalhaut system will be determined by an approved Cycle 2 follow-up program,” the authors explain.
Those observations will be longer duration, and that can help strengthen the signals and eliminate the noise in observations. That means smaller objects should be detectable, and “will push the detection limit from ~0.6 Jupiter masses down to ~0.3-0.4 Jupiter masses…??
“In addition to confirming (or rejecting) S7 as being associated with Fomalhaut, the Cycle 2 program might identify one or more of the planets expected to exist on the basis of the complex disk structure discovered in the MIRI results,” the authors conclude.
With thousands of known exoplanets and tens of thousands likely to be discovered in the coming decades, it could be only a matter of time before we discover a planet with life. The trick is proving it. So far the focus has been on observing the atmospheric composition of exoplanets, looking for molecular biosignatures that would indicate the presence of life. But this can be difficult since many of the molecules produced by life on Earth could also be produced by geologic processes. A new study argues that a better approach would be to compare the atmospheric composition of a potentially habitable world with those of other planets in the star system.
Since planets form within the debris disk of a young star, they will generally have similar compositions. Because of the migration of certain molecules such as water ice, the outer planets can have a slightly different composition than the inner planets, but overall their composition is similar. For this study, the team looked at the abundance of atmospheric carbon among worlds.
Carbon is not just a primary element for life on Earth, it also absorbs readily in water and can be bound geologically in rocks. So the idea is that if an exoplanet is in the potentially habitable zone of a star and has significantly less atmospheric carbon than similar worlds in its system, then that is a strong indicator of the presence of water and organic life. Take our solar system as an example. Earth, Venus, and Mars are all roughly in the habitable zone of the Sun, but both Venus and Mars have atmospheres comprised mostly of carbon dioxide. In contrast, Earth has an atmosphere of mostly nitrogen and oxygen, and only a fraction of a percent of carbon dioxide. Earth’s atmospheric carbon is so dramatically different from that of Venus and Mars that it stands out as a likely inhabited world.
How an inhabited planet might be discovered. Credit: Triaud, et al
As a demonstration, the team looked at how this might work for the Trappist-1 star system. It’s a red dwarf star with seven known planets roughly the size of Earth. Three of these worlds fall within the potentially habitable zone, so it’s an excellent test case for comparing worlds. Based on the capabilities of the James Webb Space Telescope (JWST), it should be able to detect atmospheric carbon dioxide levels in the Trappist-1 planets. The authors estimate that ten or so clear transits of a Trappist world would be sufficient to determine whether it has a depleted CO2 level. If one of the potentially habitable worlds in the Trappist system has a depleted level, it would be a good candidate for further study.
The authors are careful to note that depleted CO2 levels by itself could be a false positive. While large oceans and the presence of life would reduce atmospheric carbon, there are other ways as well. Certain rocks can absorb tremendous amounts of carbon, for example. Also, since the Trappist planets could be tidally locked, the dark side of the planets could get cold enough to freeze CO2, thus removing it from the atmosphere. There are also ways that life could exist on a world without depleting atmospheric carbon, so if none of the Trappist worlds have low atmospheric carbon that still wouldn’t eliminate it from potentially having life.
This method wouldn’t be definitive, but it would reveal worlds worth studying in detail. Just as early exoplanet observations began by finding candidate planets that were later confirmed, JWST could find candidate living worlds, pointing the way to confirming extraterrestrial life. And that makes this approach pretty exciting.
Researchers have built a superconducting camera with 400,000 pixels, which is so sensitive it can detect single photons. It comprises a grid of superconducting wires with no resistance until a photon strikes one or more wires. This shuts down the superconductivity in the grid, sending a signal. By combining the locations and intensities of the signals, the camera generates an image.
The researchers who built the camera, from the US National Institute of Standards and Technology (NIST) say the architecture is scalable, and so this current iteration paves the way for even larger-format superconducting cameras that could make detections across a wide range of the electromagnetic spectrum. This would be ideal for astronomical ventures such as imaging faint galaxies or extrasolar planets, as well as biomedical research using near-infrared light to peer into human tissue.
These devices have been possible for decades but with a fraction of the pixel count. This new version has 400 times more pixels than any other device of its type. Previous versions have not been very practical because of the low-quality output.
Animation depicts the special readout system that made it possible for NIST researchers to build a 400,000 single-wire superconducting camera, the highest resolution camera of its type. With further improvements, the camera will be ideal for such low-light endeavors as imaging faint galaxies or planets that lie beyond the solar system, measuring light in photon-based quantum computers, and biomedical studies that use near-infrared light to peer into human tissue. Credit: S. Kelley/NIST
In the past, it was found to be difficult-to-impossible to chill the camera’s superconducting components – which would be hundreds of thousands of wires – by connecting them each to a cooling system.
According to NIST, researchers Adam McCaughan and Bakhrom Oripov and their collaborators at NASA’s Jet Propulsion Laboratory in Pasadena, California, and the University of Colorado Boulder overcame that obstacle by constructing the wires to form multiple rows and columns, like those in a tic-tac-toe game, where each intersection point is a pixel. Then they combined the signals from many pixels onto just a few room-temperature readout nanowires.
The detectors can discern differences in the arrival time of signals as short as 50 trillionths of a second. They can also detect up to 100,000 photons a second striking the grid.
McCaughan said the readout technology can easily be scaled up for even larger cameras, and predicted that a superconducting single-photon camera with tens or hundreds of millions of pixels could soon be available.
In the meantime, the team plans to improve the sensitivity of their prototype camera so that it can capture virtually every incoming photon. That will enable the camera to tackle quantum imaging techniques that could be a game changer for many fields, including astronomy and medical imaging.
Just in time for Hallowe’en, astronomers confirmed the existence of spooky-looking infrared auroras on Uranus. Their existence reveals something about that planet’s misaligned magnetic field.
Auroras happen when charged particles in the solar wind and near-planet environment get trapped by a planet’s magnetic field. They funnel down to the atmosphere and collide with gas molecules. This happens on Earth and we see auroras over the north and south poles of our planet. They also happen at other planets. Astronomers detect them on the other giant planets, and a smaller version of them occurs on Mars. Venus probably doesn’t experience similar types of auroral displays, since it has no intrinsic magnetic field. However, it may experience something like them during particularly gusty solar wind events. At the outer planets, the gas mix is different in the atmospheres. That means their aurorae show up in ultraviolet and infrared wavelengths.
Detecting the Infrared Auroras of Uranus
Uranus has an interesting magnetic field. It does not originate from the exact center of the planet. It’s also offset by 59 degrees from the rotation axis. That’s tipped 90 degrees from the plane of the solar system. This arrangement means that the Uranian magnetosphere is asymmetric and its field strengths vary depending on location. It connects with the solar wind once every Uranian day (which is 17 hours long). The planet does show some auroral activity, particularly around the poles and Hubble Space Telescope detected some in 2011.
Auroras on Uranus Credit: NASA/ESA
The Uranus infrared aurorae showed up in observations made using the NIRSPEC spectrometer on the Keck II telescope on September 5, 2006. Astronomers from the University of Leicester analyzed the observations and zeroed in on wavelengths emitted by the H3+ charged particle. In the infrared spectrum, H3+ spectral lines will vary in brightness. Those variations depend on how hot or cold the particle is and how dense the layer of the atmosphere is where it exists. Essentially, H3+ lines can indicate something about the temperature of the atmospheric layer.
Interestingly, the Keck measurements showed that H3+ increases in density in the Uranian atmosphere. However, there’s not much change in temperature, which seems to be connected to the presence of the infrared auroras. Ph.D. student Emma Thomas, who led the observation team, p;ointed out that this may give a clue to the temperatures of the outer planets. “The temperature of all the gas giant planets, including Uranus, are hundreds of degrees Kelvin/Celsius above what models predict if only warmed by the Sun,” she said, “leaving us with the big question of how these planets are so much hotter than expected? One theory suggests the energetic aurora is the cause of this, which generates and pushes heat from the aurora down towards the magnetic equator.”
Implications of Uranian Auroras
The infrared auroras at Uranus may help planetary scientists understand something about similar-type planets around other stars, according to Thomas. “A majority of exoplanets discovered so far fall in the sub-Neptune category and hence are physically similar to Neptune and Uranus in size. This may also mean similar magnetic and atmospheric characteristics. By analyzing Uranus’s aurora which directly connects to both the planet’s magnetic field and atmosphere, we can make predictions about the atmospheres and magnetic fields of these worlds and hence their suitability for life,” she explained.
A NASA computer simulation of a reversal. The tubes represent magnetic field lines (blue when the field points towards the center and yellow when away). Earth’s rotation axis is centered and vertical. The dense clusters of lines are within the Earth’s core.
Another fascinating implication brings us right back to Earth. Periodically, our own planet’s geomagnetic pole locations flip. Scientists call that phenomenon “geomagnetic reversal.” Essentially, north flips to south and south flips to north. It’s a natural phenomenon but remains largely misunderstood. Thomas points out that there aren’t many studies of the flip. Such a flip could affect satellites, as well as communication and navigation systems. The Uranus results might provide a clue to any potential effects. “This process occurs every day at Uranus due to the unique misalignment of the rotational and magnetic axes,” she said. “Continued study of Uranus’s aurora will provide data on what we can expect when Earth exhibits a future pole reversal and what that will mean for its magnetic field.”
The team’s study of Uranian auroras is the latest in 30 years’ worth of Uranus observations, said Thomas. The infrared aurorae are the latest finding. “Our results will go on to broaden our knowledge of ice giant auroras and strengthen our understanding of planetary magnetic fields in our solar system, at exoplanets, and even our own planet,” she said.
In July of this year, an asteroid roughly 30 to 60 meters across passed Earth to within one-quarter of the distance to the Moon. It posed no threat to our world, but if it had struck Earth it would have created a blast three times greater than the 2013 Chelyabinsk impact. And we only noticed it two days after it passed. It’s a good example of how sizable asteroids still miss detection. Not ones large enough to threaten our extinction, but large enough to threaten millions of lives. If a similar asteroid was detected just days before impact, could we stop it? That’s the question raised by a recent study in the arXiv.
The paper considers an asteroid similar to the aforementioned 2023 NT1 and looks at whether it could be countered by the Pulverize It (PI) method. It sounds like something out of a blockbuster movie, where the heroes blow up the rock at just the last minute, but with only a short warning it is about the only option. Deflecting an asteroid can be done, but only if we have a long lead time. So the question really becomes whether we can launch a counter-offensive in time and whether that counter-offensive would be enough to fragment the asteroid into harmless bits.
Fragment clouds from interceptions of small (top) and large (bottom) asteroids. Credit: Lubin 2021
Surprisingly, the answer to both of those questions seems to be yes. Given current launch technology, we could launch a defense rocket within a day, assuming we were to keep one on standby. To pulverize the asteroid, the authors propose using a combination of kinetic and explosive impactors. The rocket would release a cloud of impactors at a high relative speed to the asteroid, shattering the body into fragments no more than 10 meters across. Given a typical density and composition, hypervelocity simulations show that this would be an effective way to destroy the asteroid. Even if the fragmentation occurred just hours before Earth impact, the resulting debris cloud would pose limited risk to us.
All that said, this proposal is still just a proof of concept. We have no rockets in place to launch, and no impactor system for it to carry. If we detected an imminent asteroid tomorrow we would have no way to counter it. We have the ability to build a planetary defense rocket, but the question remains on whether we have the will to build one.
![Fomalhaut is the brightest star in the constellation Piscis Austrinus. Image Credit: By IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg) - [1], CC BY 3.0 https://commons.wikimedia.org/w/index.php?curid=15412179](https://www.universetoday.com/wp-content/uploads/2023/10/Piscis-Austrinis.png)
