A team of astronomers studied two nearby globular clusters, 47 Tucanae and Omega Centauri, searching for signals produced by annihilating dark matter. Those the searches turned up empty, they weren’t a failure. The lack of a detection placed strict upper limits on the mass of the hypothetical dark matter particle.
Shining a light on dark matter
Dark matter makes up around 80% of all the mass in the universe, although it’s completely invisible. It simply doesn’t interact with the electromagnetic force, and so it doesn’t glow or reflect or absorb or anything. So far, the only evidence we have for its existence is through its gravitational effects on the rest of the universe. Because of this, astronomers aren’t exactly sure about what dark matter is, although many physicists believe that it’s some new kind of particle, previously unknown to the standard model of particle physics.
One possibility is that dark matter is made of some ultra-light particle, like an axion. And while these particles wouldn’t interact with normal matter, they might very rarely interact with themselves, colliding together and annihilating. If the energy of the collision is high enough, it can result in the production of a gamma ray, which then splits off to become an electron and positron.
The globular cluster Messier 54. Credit: NASA
Those electrons and positrons can glue together to form bound states, called positronium. However, the positronium atoms aren’t stable, and they eventually decay, leaving behind a flash of radio emission.
So even though dark matter doesn’t interact with electromagnetism directly, there’s still the possibility of us seeing the radio emission from the collision and decay of dark matter particles.
Look to the globular clusters
To make this work you need a lot of dark matter. If the dark matter particles collided easily enough, we would’ve seen it already. So the collisions must be rare. The density of dark matter in our galactic neighborhood is far too low to make detectable emission, but the dense cores of galaxies may offer better access.
The natural place to look is our galactic core, but that place is swamped with all kinds of radio emission, so it’s difficult to tell if a particular signal is coming from annihilating dark matter or something more mundane. So that’s why a team of astronomers looked to two nearby globular clusters, as reported in a paper recently appearing in the preprint journal arXiv.
The two clusters, 47 Tucanae and Omega Centauri, are only a few thousand light-years away, making them relatively easy to observe. And astronomers believe that they are the remnants of dwarf galaxies, the bulk of their stars stripped away from them through interactions with the Milky Way.
This makes the clusters ideal laboratories, because they are essentially balls of dense dark matter with very little contamination. The team of astronomers went looking for the unique radio signal of decaying positronium using the Parkes observatory in Australia.
They didn’t find anything, which isn’t necessarily a bad thing. Based on their observations, they were able to place the best upper limits yet on the mass and cross-section (a measure of how frequently the particles interact) of these light dark matter models. Sure, it would have been awesome to see a confirmed signal and finally put this dark matter mystery to rest, but new knowledge in any direction is always welcome and always helpful.
Way back in the late 1980s, the Voyager 2 spacecraft visited Uranus and Neptune. During the flybys, we got to see the first close-up views of those ice giants. Even then, planetary scientists noticed a marked color difference between the two. Yes, they both sport shades of blue. But, if you look closely at Uranus, you see a featureless pale blue planet. Neptune, on the other hand, boasts interesting clouds, dark banding, and dark spots that come and go. They’re all set against a darker blue backdrop.
So, why the difference? Planetary scientists have long suspected aerosols (droplets of gas that have liquids or dust suspended in them) in each atmosphere. But, according to a team of scientists studying the layers of the planets, the hazes those aerosols create may only be part of the story.
Uranus and Neptune: The Big Picture
To understand what’s happening let’s look at what we know about Uranus and Neptune. They’re called “ice giants” because their cores have high proportions of oxygen, carbon, nitrogen, and sulfur. Those elements are called “ices” because they are volatile chemical compounds that freeze right around 100 K. However, the clue to the different colors lies in the planets’ atmospheres. Each has hydrogen, helium, and methane as its main components. These blankets of gases are where each planet’s “weather” occurs. It turns out you need a lot of observations—both visually and in other wavelengths of light—over long periods of time to watch weather play out on these two worlds.
Voyager gave astronomers a taste of what’s “out there”. That led to more long-term observations using other ground-based and space-based observatories. Those studies reveal details about the weather at those worlds and what it does specifically to turn Uranus so pale.
Concentrated Hazes on Uranus and Neptune
Why so blue on Neptune and not so blue on Uranus? As the headline says: hazes. But, scientists needed to explain the existence and activity of hazes in the upper atmospheres of ice giant planets. So, they created a model. The work was done by a team led by Patrick Irwin, Professor of Planetary Physics at Oxford University in England.
Their model actually uses observations of multiple atmospheric layers on Uranus and Neptune. “This is the first model to simultaneously fit observations of reflected sunlight from ultraviolet to near-infrared wavelengths,” explained Irwin in a press release statement. He is the lead author of a paper presenting the team’s model in an upcoming issue of the Journal of Geophysical Research: Planets. “It’s also the first to explain the difference in visible color between Uranus and Neptune.”
Irwin’s team analyzed a set of observations of both planets in ultraviolet, visible, and near-infrared wavelengths (from 0.3 to 2.5 micrometers). The data came from the Near-Infrared Integral Field Spectrometer (NIFS) on the Gemini North telescope (part of the NOIRLab) as well as archival data from the NASA Infrared Telescope Facility. Images and data from the NASA/ESA Hubble Space Telescope also contributed to the study. Together the data revealed surprising structure and activity in both atmospheres.
Inside Blue Planet Atmospheres
The resulting model reveals striking differences between two worlds that otherwise look fairly similar. If we look at each planet in visible light, of course, we see the different shades of blue. The infrared and other data go deeper and reveal details about haze layers. The team’s model shows three layers of aerosols at different heights in the atmosphere. The layer that affects the colors is the middle layer, which is thick with haze particles and is called the Aerosol-2 layer. Both planets have that layer, but it’s the one that appears thicker on Uranus than on Neptune.
The Cause and Effect of Hazes on Uranus and Neptune
This diagram shows three layers of aerosols in the atmospheres of Uranus and Neptune, as modeled by a team of scientists led by Patrick Irwin. The height scale on the diagram represents the pressure above 10 bar. The deepest layer (the Aerosol-1 layer) is thick and composed of a mixture of hydrogen sulfide ice and particles produced by the interaction of the planets’ atmospheres with sunlight. The key layer that affects the colors is the middle layer, which is a layer of haze particles (referred to in the paper as the Aerosol-2 layer) that is thicker on Uranus than on Neptune. Above both of these layers is an extended layer of haze (the Aerosol-3 layer) similar to the layer below it but more tenuous. On Neptune, large methane ice particles also form above this layer. Courtesy International Gemini Observatory/NOIRLab/NSF/AURA, J. da Silva/NASA /JPL-Caltech /B. Jónsson
Let’s look at how hazes are created on both planets. It turns out the process is roughly the same for each one. Both have outer atmospheres rich in methane, which freezes out at roughly 91 K. That methane ice condenses onto particles in the Aerosol-2 layer mentioned above, which makes the atmospheric particles slightly more massive. The result is methane “snow” that showers down onto layers below. It actually seems like a case of “constant winter” at certain levels of each atmosphere.
However, there’s a final twist that explains the color differences between the two planets. Neptune has an active, turbulent atmosphere. That churns up the methane “snow” particles and sends more of the snow and haze deeper into the atmosphere. Thus, Neptune “grooms itself”, has a thinner haze layer, and gets to keep its pretty blue color. That same churning may also explain the dark spots on the planet.
Uranus, on the other hand, has a more sluggish atmosphere. Not as much churning of the methane “snow” goes on there and the haze particles aren’t pulled downward. That means the haze layer persists and is thicker, providing a lighter shade of pale blue on Uranus.
Two peculiar spiral galaxies are in the latest image release from the Hubble Space Telescope. The two galaxies, collectively known as Arp 303, are located about 275 million miles away from Earth. IC 563 is the odd-shaped galaxy on the bottom right while IC 564 is a flocculent spiral at the top left.
Fittingly, these two oddball galaxies are part of the Atlas of Peculiar Galaxies, which is a catalog of unusual galaxies produced by astronomer Halton Arp in 1966. He put together a total of 338 galaxies for his atlas, which was originally published in 1966 by the California Institute of Technology.
Two spiral galaxies, collectively known as Arp 303, are seen in this image from the Hubble Space Telescope. Credit: NASA, ESA, K. Larson (STScI), and J. Dalcanton (University of Washington); Image Processing: G. Kober (NASA Goddard/Catholic University of America).
What Arp wanted to do in his catalog was provide examples of the different kinds of peculiar structures found among galaxies. While most of the entries in the catalog consist of single galaxies, some of the objects were entered as interacting galaxies, and others as groups of galaxies.
Interacting galaxies usually have a distorted shape, while galaxy groups are simply gravitationally bound to each other but not necessarily close enough to each other to induce major structural changes.
While the two galaxies in Arp 303 aren’t exceptionally close to each other, they do look distorted. Therefore, Arp entered Arp 303 as “unclassified.” Objects 298–310 in his atlas are considered unclassified, and they are mostly interacting galaxy pairs.
Another unusual Arp pair, Arp 299 (parts of it are also known as IC 694 and NGC 3690) is a pair of colliding galaxies approximately 134 million light-years away in the constellation Ursa Major. Credit: NASA/ESA/Hubble Heritage team.
Since the Hubble Space Telescope is able to zoom in on the individual galaxies with its multiple instruments, this image is actually created from two separate Hubble observations of Arp 303. The first used Hubble’s Wide Field Camera 3 (WFC3) to study the pair’s clumpy star-forming regions in infrared light. The Hubble team said that galaxies like IC 563 and IC 564 are very bright at infrared wavelengths and host many bright star-forming regions.
The second observation was taken with Hubble’s Advanced Camera for Surveys (ACS) to take quick looks at bright, interesting galaxies across the sky. The observations filled gaps in Hubble’s archive and looked for promising candidates that Hubble, the James Webb Space Telescope, and other telescopes could study further.
Now less than one year until the projected launch date, ESA’s JUICE mission is in the final phases of development. The JUpiter ICy moons Explorer (JUICE) is now fully built with all ten instruments integrated into the spacecraft bus. Next comes all-up testing in a full flight configuration.
Launch is currently scheduled for April of 2023, with the mission slated to conduct detailed investigations of Jupiter and its system of moons, focusing on Europa, Callisto and especially Ganymede.
“This milestone is very important,” said Maneula Baroni, the spacecraft assembly, integration and test engineer. “The spacecraft is ready for the test campaign to verify, finally, that everything works as expected with the performances we are expecting.”
This is the first large-class mission of ESA’s Cosmic Vision program, which has the goal of helping scientists figure out what conditions are best for life – not only in our Solar System, but for our galaxy and the Universe.
Artist concept of JUICE, a Jupiter moons orbiter mission. Credit: ESA
Jupiter and its moons are very much like a solar system in itself. By studying the Jupiter system, scientists hopes to learn more about the icy worlds around Jupiter and the origins and possibility of life in our Universe, while gaining insights into how gas giant planets form. This should shed light on how life might emerge in Jupiter-like exoplanetary systems.
After launch, it will take eight years to reach the Jupiter system. The current mission timeline expects the spacecraft to operate for at least three years once there.
The spacecraft will do several fly-bys of Europa and Callisto before going into orbit around Ganymede, to conduct a more in-depth analysis. This will be the first time a spacecraft will orbit an outer Solar System moon.
JUICE will have a suite of ten science instruments which will help map out the surfaces of the three moons, as well as a get a glimpse into their icy interiors and subsurface oceans.
The spacecraft will map out Ganymede’s magnetic field, the only moon in the Solar System known to have one. At Europa, JUICE will search for the chemicals of life, and organic materials that could be on the surface, as well as learn more about its tenuous atmosphere. And JUICE will also be equipped with a radar system that will measure the depth of its subsurface oceans.
“Humanity always poses these questions,” said Baroni. “Are we alone in the Universe? Is there life outside Earth? Are there environments where life can be sustained? This is one of the main objectives for Juice: to search if on the environment, on the ocean worlds of Europa and Ganymede, are there the conditions to sustain life?”
In about 5 billion years, the Sun will leave the main sequence and become a red giant. It’ll expand and transform into a glowering, malevolent ball and consume and destroy Mercury, Venus, Earth, and probably Mars. Can humanity survive the Sun’s red giant phase? Extraterrestrial Civilizations (ETCs) may have already faced this existential threat.
Could they have survived it by migrating to another star system without the use of spaceships?
Universe Today readers are well-versed in the difficulties of interstellar travel. Our nearest neighbouring solar system is the Alpha Centauri system. If humanity had to flee an existential threat in our Solar System, and if we could identify a planetary home in Alpha Centauri, it would still take us over four years to get there—if we could travel at the speed of light!
It still takes us five years to get an orbiter to Jupiter at our technological stage. There’s lots of talk about generation starships, where humans could live for generations while en route to a distant habitable planet. Those ships don’t need to reach anywhere near the speed of light; instead, entire generations of humans would live and die on a journey to another star that takes hundreds or thousands of years. It’s fun to think about but pure fantasy at this point.
This is an image of the Nauvoo generation ship from “The Expanse.” Generation ships are the stuff of science fiction, for now. Image Credit: Legendary Television Distribution.
Is there another way we, or other civilizations, could escape our doomed homes?
The author of a new research article in the International Journal of Astrobiology says that ETCs may not need starships to escape existential threats and travel to another star system. They could instead use free-floating planets, also known as rogue planets. The article is “Migrating extraterrestrial civilizations and interstellar colonization: implications for SETI and SETA.” The author is Irina Romanovskaya. Romanovskaya is a Professor of Physics and Astronomy at Houston Community College.
“I propose that extraterrestrial civilizations may use free-floating planets as interstellar transportation to reach, explore and colonize planetary systems,” Romanovskaya writes. And when it comes to the search for other civilizations, these efforts could leave technosignatures and artifacts. “I propose possible technosignatures and artifacts that may be produced by extraterrestrial civilizations using free-floating planets for interstellar migration and interstellar colonization, as well as strategies for the search for their technosignatures and artifacts,” she said.
It’s possible that rogue planets, either in the Milky Way or some of the other hundreds of billions of galaxies, carry their own life with them in subsurface oceans kept warm by radiogenic decay. Then if they meet a star and become gravitationally bound, that life has effectively used a rogue planet to transport itself, hopefully, to somewhere more hospitable. So why couldn’t a civilization mimic that?
We think of free-floating planets as dark, cold, and inhospitable. And they are unless they have warm subsurface oceans. But they also offer some advantages. “Free-floating planets can provide constant surface gravity, large amounts of space and resources,” Romanovskaya writes. “Free-floating planets with surface and subsurface oceans can provide water as a consumable resource and for protection from space radiation.”
An advanced civilization could also engineer the planet for an even greater advantage by steering it and developing energy sources. Romanovskaya suggests that if we’re on the verge of using controlled fusion, then advanced civilizations might already be using it, which could change a frigid rogue planet into something that could support life.
The author outlines four scenarios where ETCs could take advantage of rogue planets.
The first scenario involves a rogue planet that happens to pass by the homeworld of an ETC. How often that might occur is tied to the number of rogue planets in general. So far, we don’t know how many there are, but there are certainly some. In 2021, a team of researchers announced the discovery of between 70 and 170 rogue planets, each the size of Jupiter, in one region of the Milky Way. And in 2020, one study suggested there could be as many as 50 billion of them in our galaxy.
Where do they all come from? Most are likely ejected from their solar systems due to gravitational events, but some may form via accretion as stars do.
Another source of rogue planets is our Solar System’s Oort Cloud. If other systems also have a cloud of objects like this, they can be an abundant source of rogue planets ejected by stellar activity. Romanovskaya writes: “Stars with 1–7 times solar mass undergoing the post-main-sequence evolution, as well as a supernova from a 7–20 times solar mass progenitor, can eject Oort-cloud objects from their systems so that such objects become unbound from their host stars.”
But how often can an ETC, or our civilization, expect a rogue planet to come close enough to hitchhike on? A 2015 study showed that the binary star W0720 (Scholz’s star) passed through our Solar System’s Oort Cloud about 70,000 years ago. While that was a star and not a planet, it shows that objects pass relatively close by. If the studies that predict billions of free-floating planets are correct, then some of them likely passed close by, or right through, the Oort Cloud long before we had the means to detect them.
The Oort Cloud is a long way away, but a sufficiently advanced civilization could have the capability to see a rogue planet approaching and go out and meet it.
Zooming out; the inner solar system (upper left), the outer solar system (upper right), the orbit of Sedna (lower right) and the inner edge of the Oort cloud (lower left). Image credit: NASA
The second scenario involves using technology to steer a rogue planet closer to a civilization’s home. With sufficient technology, they could choose an object from their own Oort Cloud—assuming they have one—and use a propulsion system to direct it towards a safe orbit near their planet. With sufficient lead time, they could adapt the object to their needs, for example, by building underground shelters and other infrastructure. Maybe, with adequate technology, they could alter or create an atmosphere.
The third scenario is similar to the second one. It also involves an object from the civilization’s outer Solar System. Romanovskaya uses the dwarf planet Sedna in our Solar System as an example. Sedna has a highly eccentric orbit that takes it from 76 AUs from the Sun to 937 AU in about 11,000 years. With sufficient technology and lead time, an object like Sedna could be turned into an escape ship. The author notes that “Civilizations capable of doing so would be advanced civilizations that already have their planetary systems explored to the distances of at least 60 AU from their host stars.”
Artist’s conception of Sedna, a dwarf planet in the solar system that only gets within 76 astronomical units (Earth-sun distances) of our Sun. Credit: NASA/JPL-Caltech
There are lots of potential problems. Bringing a dwarf planet from the distant reaches of the Solar System into the inner Solar System could disrupt the orbits of other planets, leading to all sorts of hazards. But the dangers are mitigated if a civilization around a post-main sequence star has already migrated outward with the changing habitable zone. Romanovskaya discusses the energy needed and the timing required in more detail in her article.
The fourth scenario also involves objects like Sedna. When a star leaves the main sequence and expands, there’s a critical distance where objects will be ejected from the system rather than remain gravitationally bound to the dying star. If an ETC could accurately determine when these objects would be ejected as rogue planets, they could prepare it beforehand and ride it out of the dying solar system. That could be extraordinarily perilous, as periods of violent mass loss from the star creates an enormous hazard.
Three rings of ejected gas sail away from an aging star named V Hydrae, seen in this false-colour radio image from the Atacama Large Millimeter/submillimeter Array in Chile. Image Credit: ALMA
In all of these scenarios, the rogue planet or other body isn’t a permanent home; it’s a lifeboat. “For all the above scenarios, free-floating planets may not serve as a permanent means of escape from existential threats,” the author explains. “Because of the waning heat production in their interior, such planets eventually fail to sustain oceans of liquid water (if such oceans exist).”
Free-floating planets are also isolated and have fewer resources than planets in a solar system. There are no asteroids to mine, for example, and no free solar energy. There are no seasons and no night and day. There are no plants, animals, or even bacteria. They’re simply a means to an end. “Therefore, instead of making free-floating planets their permanent homes, extraterrestrial civilizations would use the free-floating planets as interstellar transportation to reach and colonize other planetary systems,” writes Romanovskaya.
In her article, Professor Romanovskaya speculates where this could lead. She envisions a civilization that does this more than once, not to escape a dying star but to spread throughout a galaxy and colonize it. “In this way, the parent-civilization may create unique and autonomous daughter-civilizations inhabiting different planets, moons or regions of space.”
“A civilization of Cosmic Hitchhikers would act as a ‘parent-civilization’ spreading the seeds of ‘daughter-civilizations’ in the form of its colonies in planetary systems,” she writes. “This applies to both biological and post-biological species.”
Artist’s rendering of an Earth-sized rogue planet approaching a star. Credit: Christine Pulliam (CfA)
Humanity is only in the early stages of protecting ourselves from catastrophic asteroid impacts, and we can’t yet manage our planet’s climate with any degree of stability. So thinking about using rogue planets to keep humanity alive seems pretty far-fetched. But Romanovskaya’s research isn’t about us; it’s about detecting other civilizations.
All of this activity could create technosignatures and artifacts that signified the presence of an ETC. The research article outlines what they might be and how we could detect them. Rogue planets used as lifeboats could create technosignatures like electromagnetic emissions or other phenomena.
An ETC could use solar sails to control a rogue planet or use them on a spaceship launched from a rogue planet once they have reached their destination. In either case, solar sails produce a technosignature: cyclotron radiation. Maneuvering either a spacecraft or a rogue planet with solar sails would produce “… cyclotron radiation caused by the interaction of the interstellar medium with the magnetic sail.”
Infrared emissions could be another technosignature emitted as waste heat by an ETC on a rogue planet. An excessive amount of infrared or unnatural changes in the amount of infrared could be detected as a technosignature. Infrared could be emitted unevenly across the planet’s surface, indicating underlying engineering or technology. An unusual mix of different wavelengths of electromagnetic energy could also be a technosignature.
The atmosphere itself, if one existed, could also hold technosignatures. Depending on what was observed, it could contain evidence of terraforming.
For now, astronomers don’t know how many rogue planets there are or if they’re concentrated in some areas of the galaxy. We’re at the starting line when it comes to figuring these things out. But soon, we may get a better idea.
The Vera Rubin Observatory should see first light by 2023. This powerful observatory will image the entire available sky every few nights, and it’ll do it in fine detail. It houses the largest digital camera ever made: a 3.2 gigabyte CCD.
In Chile, the Vera C. Rubin Observatory is under construction at Cerro Pachon. This image shows construction progress in late 2019. The VCO should be able to spot rogue planets that approach our Solar System. Image Credit: Wil O’Mullaine/LSST CC BY-SA 4.0, https://ift.tt/mWMVpgT
The Vera Rubin will be especially good at detecting transients, that is, anything that changes position or brightness in a couple of days. It’ll have a good chance of spotting any interlopers like rogue planets that might approach our Solar System.
There’s a strong possibility that some of those rogue planets will exhibit unusual emissions or puzzling phenomena. Scientists will probably puzzle over them as they did over Oumuamua.
Maybe another civilization more advanced than us has already faced an existential threat from their dying star. Maybe they made a Herculean effort to capture a rogue planet and engineer it to suit their needs. Maybe they’ve already boarded it and launched it towards a distant, stable, long-lived yellow star, with rocky planets in its habitable zone. Maybe they’re wondering if there’s any life at their destination and how they might be received after their long journey.
Solar sailing technology has been a dream of many for decades. The simple elegance of sailing on the light waves of the sun does have a dreamy aspect to it that has captured the imagination of engineers as well as writers. However, the practicalities of the amount of energy received compared to that needed to move useful payloads have brought those dreams back to reality. Now, a team led by Amber Dubill of John Hopkins University Applied Physics Laboratory and supported by the NASA Innovative Advanced Concepts (NIAC) program is developing new solar sail architecture that might have already found its killer app – heliophysics.
The technique they are using is known as diffractive light sailing. It has significant advantages over existing solar sail technology, including the ability to turn. That is a big problem for most solar sails, which lose effectiveness if they are not directly facing the sun. Diffraction causes light to spread out when it passes through an opening. Utilizing this property in a solar sail material would allow a craft to turn away from the sun while still getting the pressure of light pushing it in whatever direction it turned.
To create such diffractive pressure, the team created a material with very small gratings embedded in it to diffract the light on a surface that could still benefit from the force created when that light is absorbed. This would allow any spacecraft using the sail as a propulsion system to turn slightly away from the sun and still benefit from a forceful push from the light’s photons.
UT video describing what solar cells are.
To prove this technology, the NIAC is supporting it with a Phase III grant after successfully completing Phase I and Phase II over the past few years. Phase III comes with $2 million in funding for two years to continue the development of the material used on the solar sail, culminating in ground tests that could presage a move to use in deep space.
Deep space is the most likely place for an application such as these diffractive sails. In particular, the researchers think they will be instrumental in heliophysics. Traditional propulsion technologies don’t work well around the sun’s poles, given the magnetic interference in that space. Traditional solar sails wouldn’t work well either, as the incident light falling on them in these locations would either push them farther away from the sun or not push them at all.
Weekly Space Hangout with UT publisher Fraser Cain & Amber Dubill – lead researcher on the diffractive solar sail technology.
With a diffractive solar sail, a spacecraft could still orient itself in the right direction while also using the force from light to move effectively. This would allow a craft equipped with one to observe the sun from an angle never before seen. But there’s still a long way to go before any craft is outfitted with one. The funding path past Phase III of NIAC is murky at best for now, and there will still be more development work left to be done after two more years of development. But, with luck, a new type of solar sail might be attached to the next generation of heliophysics lab. And it might eventually be used on many other programs too.
Humans aren’t the only living things in place onboard the ISS. Bacteria, which has found a way to integrate itself into every biome on Earth, has also found a home in the aseptic microgravity of the space station high above it. Unfortunately, this poses a hazard to both the astronauts that live on the ISS and the station itself. But now, a team of researchers funded by ESA and the Instituto Italiano di Tecnologia (IIT) think they have a solution – make the surfaces on the ISS antimicrobial.
That is easier said than done – there are hundreds of different materials on the ISS, and each has its own mechanical and chemical properties. Scientists already know there are dozens of species of bacteria and fungi that live on the space station. Some are even dangerous to humans, such as Staphylococcus aureus, which can cause respiratory infections.
What’s more, some of those bacteria can be harmful to the space station itself. Microbe colonies are known to form biofilms, which can eat through plastic, rubber, glass, and even metal if left untreated. In fact, the biofilm problem got so bad on Mir that there were concerns for the station’s long-term viability before it was mothballed.
Astronaut experimenting with bacteria on the ISS.
Credit – NASA
One obvious answer to this problem is to clean. But let’s be honest – astronauts have much better things to do with their time. And, admittedly, they have a team of very brainy scientists who are being paid to develop a system for them never to have to clean again.
That system is supported by the “Optimization of Photo-catalytic Antibacterial coatings” or PATINA project and is funded by ESA’s Open Space Innovation Forum. Other research paths in the project include superhydrophobic materials, though they have a different use case than the antimicrobial ones developed by IIT and ESA engineers.
Those antimicrobial coatings are based around titanium dioxide – a material that, when exposed to light, will break water vapor into “free oxygen radicals” that destroy any living thing touching its surface, including bacteria and fungi. Titanium dioxide also has advantages over the more traditional antimicrobial material – silver.
Image of some fungi growing onboard the ISS.
Credit – NASA / ESA
Silver has been used for its antimicrobial properties for centuries – it’s why we have silverware. However, silver also has undesirable properties when a person is consistently exposed to it, such as eye and skin irritation. It can even change the color of a person’s skin in high enough quantities. And it’s much harder to avoid in the enclosed environment of the ISS rather than in the open air around most people’s tables.
Titanium dioxide doesn’t have any of those adverse side effects, at least so far known to science. The researchers developing this coating are actively trying to artificially age the coatings and damage them in as many ways as possible to ensure they aren’t harmful. As Fabio Di Fonzo, one of the researchers from IIT, says, “Obviously, we don’t want end products more toxic than the microbes themselves.”
So far, they haven’t found any hazardous side effects, and the team has successfully coated several different types of surfaces, including clean-room grade paper and aluminum foil, which is in abundant use on the ISS. They have also done so with layers as small as 50 to 100 nanometers in an attempt to maintain the mechanical properties of whatever surfaces they are coated on.
Petri dish with bacteria samples collected on the ISS.
Credit – NASA / JPL
The total number of different types of surfaces exposed to bacteria in space will continue to grow as human space exploration evolves, and ESA is already taking the fight against harmful bacteria seriously. Two other ESA-supported projects are already researching bacterial growth on the ISS – MATISS, a French experiment, and a German experiment called Touching Surfaces. While it is inevitable that humans will share long-term space habitats with microbes of all kinds, it’s best to do so so that it won’t harm any humans or the craft they rely on.
Some of the Hubble Space Telescope’s most famous and stunning images are of distant galaxies, and this one is drop-dead gorgeous too.
This new image features the Grand Design Spiral, NGC 3631, which is located about 53 million light-years away in the direction of the constellation Ursa Major.
The “arms” of grand design spirals appear to wind around and into the galaxy’s nucleus.
A ‘Grand Design’ spiral galaxy is a type of spiral galaxy with prominent and well-defined spiral arms. The arms of this galaxy look as though they are winding around and spiraling out from the galaxy’s center, like a classic spiral galaxy. Other spiral galaxies might have multiple arms or be more “flocculent” or fluffy. But about 10% of spiral galaxies are considered Grand Design Spirals.
Image Credit: NASA, ESA, A. Filippenko (University of California – Berkeley), and D. Sand (University of Arizona); Image Processing: G. Kober (NASA Goddard/Catholic University of America)
Take a closer look at NGC 3631 and you can see bright star forming regions along the inner part of the spiral arms, and the new stars show up as a bright blue (remember the old astronomical adage: new and blue, red and dead.)
The image includes data taken with Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys.
Lead image caption: Image Credit: NASA, ESA, A. Filippenko (University of California – Berkeley), and D. Sand (University of Arizona); Image Processing: G. Kober (NASA Goddard/Catholic University of America)
Most of the stars in the Milky Way are single stars. But between one-third and one-half of them are binary stars. Can habitable planets form in these environments?
New research shows that habitable planets could exist around binary stars, but they would form differently than worlds around single stars.
A young binary star system about 1,000 light-years away is at the heart of this research. It’s called NGC 1333-IRAS2A, and it’s a low-mass binary protostar. The binary pair is so young it’s still gathering mass. It’s the focus of several studies into protostars and protostellar disks because it’s young and still forming.
The new study is titled “Binarity of a protostar affects the evolution of the disk and planets,” published in the journal Nature. The lead author is Professor Jes K. Jørgensen from the Niels Bohr Institute at the University of Copenhagen. Professor Jørgensen is co-author of several papers on NGC 1333-IRAS2A.
The study is based on ALMA (Atacama Large Millimetre/submillimetre Array) observations of NGC 1333-IRAS2A. These observations are only snapshots of a process that takes millions of years. But with these observations, and the knowledge gleaned from the study of young protostars in general, the research team created computer simulations of the binary protostar that reach backward and forward in time.
The study shows that planet formation is different around binary stars than solitary stars like our Sun. It’s because of the way the young stars behave as they form.
“The observations allow us to zoom in on the stars and study how dust and gas move towards the disc. The simulations will tell us which physics are at play, how the stars have evolved up till the snapshot we observe, and their future evolution,” explained Postdoc Rajika L. Kuruwita from the Niels Bohr Institute, who is the study’s second author.
Young protostars are surrounded by protoplanetary disks made of gas and dust. Inside the disks, planets form mostly via accretion. After millions of years of chaos and collision, planets coalesce and take up orbits. It’s a highly complex process that scientists are studying intently. Solar systems like ours are simple in one way: there is only one star. The star’s mass and gravity influence the morphology and behaviour of the protoplanetary disk and the planets that form in the disk.
But in a system with two protostars, there’s even more complexity.
In a single star system, the star accretes material more uniformly. There are still variations in accretion, but things progress more predictably with only one massive object. But as this study shows, binary protostars behave much differently as they form. Rather than a steady accretion process, the star formation process is marked by cyclical bursts of brightness as the stars orbit their common center of mass and periodically absorb large amounts of material. Those punctuated episodes of absorption trigger outbursts of energy which distort the disk. And that has implications for any planets forming in the disk of material around the stars.
This image is a screenshot of one of the study’s MHD (magneto-hydrodynamic) simulations of the binary protostar. A gas bridge (yellow) connects the pair, and the white lines indicate an outflowing burst of material resulting from an episode of rapid accretion. These powerful bursts shape and disrupt the protoplanetary disks where planets form. Image Credit: Jørgensen, Kuruwita et al. 2022.
“The falling material will trigger significant heating. The heat will make the star much brighter than usual,” says Kuruwita. “These bursts will tear the gas and dust disc apart. While the disc will build up again, the bursts may still influence the structure of the later planetary system.”
This figure from the study shows some of the activity at the binary protostar. The stars orbit their common center of gravity, shown with the black dot. When one of the stars absorbs an elevated amount of material, it flares in brightness and produces an outflow. Because of the binary motion of the protostars, the outflows are not bipolar. Image Credit: Jørgensen, Kuruwita et al. 2022.
The episodes of increased infalling material are cyclical. For tens or hundreds of years, every thousand years or so, material movement into the stars becomes very strong. The binary stars brighten by tens or hundreds of times their normal brightness during these episodes before subsiding.
“The falling material will trigger a significant heating. The heat will make the star much brighter than usual,” says Kuruwita. “These bursts will tear the gas and dust disc apart. While the disc will build up again, the bursts may still influence the structure of the later planetary system.”
This MHD simulation from the study shows accretion flows and outbursts from young binary protostars. Credit: Jørgensen, Kuruwita et al. 2022.
NGC 1333-IRAS2A is kind of like a laboratory for watching young systems form. There are no planets yet, so it’s too soon to conclude what effect this activity has on planetary formation or if habitable planets can form there. But other objects might also be a part of the habitability equation, and the research team intends to use ALMA to study the system some more, particularly comets.
Comets in our Solar System are known to carry some of the building blocks of life. Scientists have detected the amino acid glycine on comet 67P/Churyumov-Gerasimenko. They’ve also found ammonia salts and aliphatic compounds. These discoveries lend weight to the long-standing idea that comets can spread the materials for life throughout solar systems.
Comet 67P as seen by Rosetta on 7 July 2015. By ESA/Rosetta/NAVCAM, CC BY-SA IGO 3.0, CC BY-SA 3.0-igo, https://ift.tt/gomK2AD
“Comets are likely to play a key role in creating possibilities for life to evolve. Comets often have a high ice content with the presence of organic molecules. It can well be imagined that the organic molecules are preserved in comets during epochs where a planet is barren and that later comet impacts will introduce the molecules to the planet’s surface,” said Professor Jørgensen.
Recent research shows that building blocks can form on icy grains in space. But in a system like NGC 1333-IRAS2A, the episodes of pronounced heating could disrupt or change the chemistry in that process.
“The heating caused by the bursts will trigger evaporation of dust grains and the ice surrounding them. This may alter the chemical composition of the material from which planets are formed,” said Jørgensen.
ALMA can detect some of these chemicals, particularly in gaseous form. And it can see some complex chemistry. In this study, the authors detected several complex chemicals around the protostars.
This figure from the study shows some of the molecules detected around VLA1, one of the stars in the binary pair. The team detected them in the warm gas in the protostellar envelope. Image Credit: Jørgensen, Kuruwita et al. 2022.
“The wavelengths covered by ALMA allow us to see quite complex organic molecules, so molecules with 9-12 atoms and containing carbon. Such molecules can be building blocks for more complex molecules which are key to life as we know it,” said Jørgensen. “For example, amino acids which have been found in comets.”
Humanity will have to watch NGC 1333-IRAS2A for millions of years to see what type of planets form. But we won’t have to wait that long to understand some of the chemistry in the system and what type of building blocks are present. The James Webb Space Telescope, ALMA, the upcoming Square Kilometer Array (SKA) and the European Extremely Large Telescope (E-ELT) will all work together to detect the elusive chemistry. Not only in this young binary protostar system but in others as well.
“The SKA will allow for observing large organic molecules directly. The James Webb Space Telescope operates in the infrared, which is especially well suited for observing molecules in ice. Finally, we continue to have ALMA, which is especially well suited for observing molecules in gas form. Combining the different sources will provide a wealth of exciting results,” Jørgensen said.
Utilizing tools for purposes they weren’t initially intended for is a strength of the astronomical community. Scrounging through data collected for one purpose and looking for hints of another seems to be a favorite pastime of many a professional astronomer. That tradition is alive and well, with a team reanalyzing the first few data sets from Gaia, ESA’s star cataloging explorer. They found hints of exoplanets, and it turns out the probe launched in 2013 is a much better planet hunter than initially thought.
Gaia’s original mission was to track stars very carefully. Initially, it aimed to create a catalog of over 1 billion astronomical objects, including everything from quasars to asteroids. So far, it has far exceeded expectations by cataloging 1.8 billion stars alone. It does so using three main instruments. Astro is an astrometry instrument that measures the angular position of many of the stars it is observing. Photometry is covered by the BP/RP instrument, which measures the luminosity of its subjects. Finally, the RVS instrument measures the speed at which the objects are musing using the radial-velocity technique.
Combining data from these three instruments allows Gaia to sense how far away hundreds of millions of astronomical objects are and how fast they are moving. And it has delivered spectacularly on its original promise, with its data underpinning dozens of papers ranging from observations of globular cluster mergers to the dimmest galaxy ever discovered.
UT video discussing Gaia’s findings
But that’s not all; the international team of researchers involved in analyzing and releasing Gaia’s data sets thought they might be able to find other ghosts hiding in the star cataloger’s data. Thousands of exoplanets have been found thus far, many of them using the radial-velocity method of watching a star move back and forth as the orbiting planet’s gravity makes it jiggle slightly in the sky. They believed that Gaia could do just that.
With Gaia’s super precise instruments, it was well placed to detect the minute changes in a star’s position when it was disturbed by a planet. In fact, the team utilized photometric data sets from all three primary instruments on the craft. They then fed that data into a training algorithm that used TESS’s exoplanet survey results to help train the algorithm on what to look for as a positive exoplanet finding.
What they did find were at least two new planets. Now known as Gaia-1 and Gaia-2, these two planets are both “hot Jupiters” – giant planets that have an orbital period so fast that they are tidally locked to their star. However, despite first having shown up in the Gaia data, the existence of the planets was confirmed by observations from TESS, an observatory much more focused on exoplanet hunting.
Collaboration with UT’s editor, Fraser Cain, and YouTuber Isaac Arthur.
TESS has an entirely different underlying observational strategy than Gaia. It focuses on repeated, high-accuracy measurements of a star that might host a planet. In contrast, Gaia takes much less frequent images of its target as part of its whole sky observational requirements. That didn’t stop the researchers from trying, though. They managed to find that even with Gaia’s sparse data points, they were able to detect not only the two confirmed new planets but also 41 other exoplanet candidates that still need further validation before officially being accepted into the ranks of known exoplanets.
Overall that is an excellent record for Gaia searching for things it was not designed for. But there is more yet to come, with the next release of Gaia data, known as DR3, expected for release in June this year. There is undoubtedly evidence of even more exoplanets just waiting to be found in Gaia’s new data with this newly trained algorithm.
Ever since astronomers found that Earth and the Solar System are not unique in the cosmos, humanity has dreamed of the day when we might explore nearby stars and settle extrasolar planets. Unfortunately, the laws of physics impose strict limitations on how fast things can travel in our Universe, otherwise known as Einstein’s General Theory of Relativity. Per this theory, the speed of light is constant and absolute, and objects approaching it will experience an increase in their inertial mass (thereby requiring more mass to accelerate further).
While no object can ever reach or exceed the speed of light, there may be a loophole that allows for Faster-Than-Light (FTL) travel. It’s known as the Alcubierre Warp Metric, which describes a warp field that contracts spacetime in front of a spacecraft and expands it behind. This would allow the spacecraft to effectively travel faster than the speed of light while not violating Relativity or causality. For more than a decade, Dr. Harold “Sonny” White has been investigating this theory in the hopes of bringing it closer to reality.
Previously, Dr. White pursued the development of an Alcubierre Warp Drive with his colleagues at the Advanced Propulsion Physics Research Laboratory (NASA Eagleworks) at NASA’s Johnson Space Center. In 2020, he began working with engineers and scientists at the Limitless Space Institute, a non-profit organization dedicated to education, outreach, research grants, and the development of advanced propulsion methods – which they hope will culminate in the creation of the first warp drive!
Warp Fields 101
While the idea of “warp drives” and FTL have been with us for decades, these concepts have overwhelmingly been the stuff of science fiction and pure speculation. It was not until 1994 that an actual proposal was made to explain how FTL could work within the realm of known physics. The credit for this goes to Mexican theoretical physicist Miguel Alcubierre, who proposed what would come to be known as the “Alcubierre Drive” as part of his Ph.D. study at Cardiff University, Wales.
In his research paper, “The warp drive: hyper-fast travel within general relativity,” he offered a possible solution to Einstein’s field equations that considered how a spacecraft could achieve apparent Faster-Than-Light (FTL) travel without violating Relativity. Alcubierre concluded that it was possible, provided a field could be created with a lower energy density than the vacuum of space (aka. negative mass or “exotic matter“).
According to Alcubierre, quantum field theory allows for the existence of regions of spacetime that have negative energy densities. This is known as the Casimir Effect, which describes the attractive force between two surfaces in a vacuum. If a “ring” of negative mass could be created around a spacecraft, spacetime could theoretically be contracted in front of the ship and expanded behind. This would allow the spacecraft to effectively travel faster than the speed of light.
“By a purely local expansion of spacetime behind the spaceship and an opposite contraction in front of it, motion faster than the speed of light as seen by observers outside the disturbed region is possible,” he wrote. “The resulting distortion is reminiscent of the “warp drive” of science fiction. However, just as it happens with wormholes, exotic matter will be needed in order to generate a distortion of spacetime.”
Dr. White explained the concept to Universe Today via Zoom using an everyday metaphor. Basically, he said, it’s like using (what he refers to as) a “travelator,” those horizontal conveyor belts at major airports:
“Normally, you walk along at about three miles an hour going from one gate to another. But in some locations, you have these horizontal ‘travelators,’ and you step on top of them. So you’re still walking at three miles an hour, but the belt is moving as well. Conceptually speaking, the belt is contracting space in front of you and expanding space behind you, so that it augments your apparent speed. But locally, you’re still going at the same speed.”
This way, an object would not be violating Relativity since it is merely riding a wave generated by the expansion and contraction of local spacetime. This would allow spacecraft to circumvent the problems of time dilation (where time slows down as objects approach the speed of light), the massive increase in inertial mass, and the extreme energy required to keep accelerating. Ah, but there was a snag, and it was a doozy!
According to Alcubierre’s original paper, the amount of negative mass required to achieve a warp field was beyond anything humanity could achieve. However, his work has been revisited in the nearly thirty years since he first proposed it, and some of the strict energy requirements that he outlined have been reconsidered. In essence, revised calculations have shown that the amount of exotic matter required to generate a warp field might be within the realm of possibility.
Dr. White’s own revised take on the Alcubierre Metric came in 2011 while he was preparing to deliver a speech at the first 100 Year Starship symposium, a joint project hosted by NASA and the Defense Advanced Research Projects Agency (DARPA):
“I was asked to give a talk about space works at the inaugural NASA-DARPA 100 Year Starship symposium. I didn’t just want to rehash what I had already talked about in the past, so I went through and did some sensitivity analysis with the field equations. I was looking at what happens when you change some of the input parameters to the preliminary requirement for the phenomena – just because I wanted to have something new to talk about.
“In the process of that, it became very clear that you could significantly reduce the amount of negative vacuum energy density that’s necessary to make the trick work, non-trivially so. The stuff I published in 11′, 12′, and 13′ – three different conferences back to back- I was able to duplicate the best prediction that had been done prior to that by my colleague.”
The Enterprise using a warp drive, as seen in Star Trek Beyond. Credit: Paramount Pictures
That colleague was none other than astrophysicist Richard Obousy, who co-founded Project Icarus with starship engineer Kevin Long in 2009. In a study released that same year (“Casimir energy and the possibility of higher dimensional manipulation“), Obousy and co-author Aram Saharian considered how next-generation particle accelerations could produce Standard Model fields that could adjust the density of dark energy locally and change the expansion of spacetime.
Their calculations further indicated that this could be done with a negative vacuum energy density roughly equivalent to the size of Jupiter (1.898×1024 kg; 4.18×1024 lbs). While mathematically possible, this energy requirement is beyond anything we can currently conceive, let alone accomplish! However, Dr. White found that reconsidering the “shell-thickness parameter” of the warp bubble would further reduce that energy requirement.
As he explained, a thicker warp shell would reduce the strain on spacetime, thus allowing a spacecraft to achieve speeds of up to 10 times the speed of light (10 c) using only two metric tons (2.2 U.S. tons) of exotic matter:
“I went through the process and showed that allowing the shell of the warp bubble to get thicker reduces the magnitude of the York time field. Think of that as the strain that you put on spacetime. And so, by making the warp bubble thicker, you could reduce the magnitude of the York time [field]. And it’s non-linear. And so, by doing that, we were able to reduce the amount of exotic matter from Jupiter down to two metric tons – about the size of the Voyager 1 spacecraft.”
Based on these findings, which were outlined in his seminal paper (“Warp Field Mechanics 101“), Dr. White concluded that an Alcubierre Warp Drive was not just mathematically possible but plausible. As for feasibility, that still requires that scientists find a way to generate negative vacuum energy, which will require a significant breakthrough in physics.
Between 2012 and 2019, Dr. White and his colleagues at NASA investigated the possibility of achieving this breakthrough at NASA Eagleworks, along with other advanced propulsion concepts (like the E.M. Drive). Since then, he has continued to pursue these efforts through the Limitless Space Institute, a non-profit organization dedicated to developing the science and technology that will allow humanity to “Go Incredibly Fast!”
Limitless Space Institute
The LSI was founded in 2020 by astronaut Brian K. (B.K.) Kelly, the former Director of Flight Operations at NASA’s Johnson Space Center before retiring in 2019. This non-profit was founded with the vision of advancing human space exploration beyond the Solar System by the end of the 21st century. To this end, the LSI is committed to education and outreach efforts that will inspire the next generation and the research and development of enabling technologies.
To help him realize this vision, Kelly turned to Dr. Harold “Sonny” White, his one-time colleague at the Johnson Space Center. As Dr. White recounted, his involvement with the Institute began in 2019 after his former colleague reached out to him:
“He wanted to talk to me about some education outreach topics. In the process of talking with him, he [asked if I would] potentially leave NASA and come help him stand up and define Limitless Space Institute. After a lot of thought and prayer, it just felt like I could be a little bit more effective at trying to make progress in this domain of advanced power and propulsion. So I made the decision to pull the D-ring at the end of 2019 and join the Limitless Space Institute as the Director of Advanced Research and Development.”
In addition to Kelly and Dr. White, many former astronauts and commercial space heavyweights have joined LSI to realize the goal of interstellar FTL travel. These include its Board of Directors, which consists of such luminaries as Gregory “Ray J” Johnson (Secretary of the Board). Johnson is a retired NASA astronaut who piloted the final Space Shuttle mission (STS-135), which took place on July 8th, 2011, and saw the Space Shuttle Atlantis make its final trip to International Space Station (ISS).
There’s also Kam Ghaffarian (Chairman of the Board), an engineer and entrepreneur who is the co-founder and Executive Chairman of X-energy, Intuitive Machines, Axiom Space, and the CEO of the innovation and investment firm IBX. And then there’s Gwynne Shotwell (Independent Advisor to the Board), whom fans of commercial space will immediately recognize as the President and Chief Operations Officer (COO) of SpaceX, and a member of their Board of Directors.
A spacecraft equipped with an Alcubierre Warp Drive in orbit around an exoplanet. Credit: Limitless Space
A Three-Step Project
The goal of realizing interstellar spaceflight, said Dr. White, is an extremely tall order and will require some revolutionary breakthroughs:
“When people think of space travel today, they might think of sending human beings back to the surface of the Moon or neat rovers on the surface of Mars doing interesting things. And those are amazing examples of space exploration, but those are all possible using chemical propulsion. If we want to send human beings to the outer Solar System, if we want to get a crew from the Earth to Saturn in 200 days, the amount of energy that’s necessary to make something like that possible is an entire order of magnitude larger than it takes to get a payload from the surface of Earth to Low Earth Orbit.
Simply put, there’s no way long-distance missions can be done in a reasonable amount of time using chemical propulsion. For that to happen, says Dr. White, we need to think beyond the realm of known physics. To that end, he and his colleagues have adopted a research plan based on three broad categories of theoretical propulsion, each one more advanced than the last. The first (Fission) is dedicated to advancing the technology of Nuclear Electric Propulsion (NEP), which NASA and other space agencies are investigating for their future exploration goals.
This time-honored concept uses nuclear reactors to power Hall-effect thrusters (aka. ion engines) that ionize inert gases (like xenon) to create a charged plasma used to generate propulsion. The benefits of this method include the fact that it is within the realm of known physics and has been validated by past experiments by both NASA and the Soviet space programs. This includes NASA’s Systems for Nuclear Auxiliary Power-10A (SNAP-10A) nuclear satellite, tested in 1965 and flew in space for 43 days.
Limitless Space Institute’s three-step program from realizing interstellar flight. Credit: LSI
The Soviets, meanwhile, sent about 40 nuclear-electric satellites into space, the most powerful of which was the TOPAZ-II reactor that produced 10 kilowatts of electricity. There’s also the ground-tested Nuclear Engine for Rocket Vehicle Application (NERVA), a nuclear thermal propulsion (NTP) concept developed by NASA in 1968-69. Compared to NEP, this method uses a nuclear reactor to heat hydrogen propellant and the resulting plasma to generate propulsion. This remains the only concept capable of generating power in the megawatt (MW) range, which is absolutely required for crewed missions.
Specifically, Dr. White and his team are working towards a NEP engine that could generate 2-50 MW power that would allow for rapid transit to Saturn and other locations in the outer Solar System – about ~1,000 AU (149.6 billion km; 92.9 billion mi) from our Sun. However, these NEP spacecraft would still take a few thousand years to get to Proxima Centauri. Going faster, said Dr. White, requires pushing beyond fission and moving “a little bit into the unknown.”
This is where the next step in LSI’s comes into play (Fusion), which calls for the development of fusion electric propulsion (FEP) – which is in the 50 to 500 MW range. As Dr. White described it:
“[I]nstead of fission and uranium, we’re using deuterium and tritium or some combination of gases that we could fuse of very high temperatures when they’re in the form of a plasma. Fusion propulsion is a little more capable than nuclear-electric propulsion. The one caveat is [that] we don’t have fusion reactors all over the planet. So the engineering of a fusion reactor, we still have to work that out. But that may actually be a little closer than most people think.
“But fusion propulsion would enable us to send large payloads to Proxima Centauri in 100 years. Maybe less, if you want to get aggressive with the delta-v (acceleration). But if we want to do an interstellar mission to Proxima Centauri, and we want to get there in 20 years or less, that’s where we have to look to the frontiers of physics – move firmly into the unknown.”
Comparison of the Daedalus spacecraft and Saturn V Moon rocket. Credit/copyright: Adrian Mann.
This is where the third step (Breakthrough) comes into play, where significant progress needs to be made in our understanding of physics. This step requires that we find an answer to how the four fundamental forces that govern the Universe fit together. This includes Relativity, which describes how gravity governs interactions on a large scale, and quantum mechanics, which describes how matter behaves on the smallest scales (the atomic and subatomic levels).
Basically, we need a Theory of Everything (or a theory of “quantum gravity”), which has eluded scientists for about a century. This is why Dr. White and LSI are taking an incremental approach that includes future innovations and discoveries. These may be coming sooner than expected, said Dr. White, due to the introduction of artificial intelligence, machine learning, and advanced computing. In the meantime, there’s plenty of research to be done that’s within the realm of known physics.
Progress to Date
With Limitless Space, Dr. White and his colleagues are currently studying custom Casimir cavities, which consist of two plates in a vacuum chamber with pillars in between. These tests aim to measure how the quantum vacuum responds to the shapes inside these cavities, and the predicted characteristics of these cavities could be measured. Recently, Dr. White and his team performed work for DARPA, where these custom cavities were used to explore the possible existence of a vacuum polarization field.
But in the process of looking at how the vacuum responds to these shapes, he and his team noticed something completely unexpected:
“The custom Casimir cavities consist of two plates, and in between the two plates, we have pillars. When we were looking at how the models we have predicted how the quantum vacuum responds to those pillar-plate geometries – when we looked at a two-dimensional section cut of the vacuum energy distribution, it looked like a two-dimensional section cut of the energy density distribution needed for the Alcubierre Warp Metric.
The one provision to this quantitative similarity was that the custom Casimir cavities had these lenticular energy distributions prismatic in shape. In contrast, the Alcubierre Warp Metric requires this toroidal ring of negative vacuum energy density. Feeling that they were close, Dr. White and his team chose to implement a different approach.
“So we looked at creating a mathematical model where it consisted of a one-micron diameter sphere centered inside a four-micron diameter cylinder,” he said. “We looked at how the quantum vacuum would respond to such a nanostructure’s shape, and that nanostructure is predicted to manifest a negative vacuum energy density that would meet the Alcubierre Warp Metric.”
These numerical analysis results were presented in a paper published in the European Physics Journal C – (EPJ C) in 2021. This paper indicated to the general public that an object built with a specific geometry would manifest a nanoscale warp bubble. While this is a far cry from spacecraft capable of FTL travel, it is a significant precedent and a step in that direction. According to Dr. White, the next step is to create an experiment for measuring any optical properties that this apparatus could manifest.
As always, the work continues. Step-by-step!
Education, Outreach, Grants & Partnerships
Another important aspect of LSI is its partnerships with other scientific organizations and educational institutions. In particular, LSI continues to conduct research and development in the Eagleworks laboratory facilities to explore the dynamic vacuum model. The LSI is also in partnership with Texas A&M and the Massachusetts Institute of Technology (MIT), who lend their nanomanufacturing capabilities to make the devices LSI uses in their lab experiments.
In addition, the Institute started a grant program designed to foster scientific research that could lead to major breakthroughs. This program is overseen by the Interstellar Initiatives (I2) grants program, which awards universities and organizations worldwide for theoretical work (tactical grant) and empirical work (strategic grant) that helps advance space exploration. The program conducted its first biannual round of grants and awards in 2020. This year, said Dr. White, the Institute will be expanding its focus:
“This year, we’re doing our second biannual grant cycle and we’re augmenting the original call to also fund graduate and postdoc fellowships. So that’s a new addition to the 2022-2024 cycle. We have LSI scholarships, where we give undergraduate students scholarships. We have a program called LSI Lab Boosters. That is a program that we started to address K-12 so that’s where we provide small seed awards of 3 to 7k to worthy organizations that work with kids in elementary, middle school, and high school. We also have classes, we commissioned the Institute for Interstellar Studies (I4IS) to do a week-long summer class.”
The focus of last year’s summer class was “Human Exploration of the Far Solar System and on to the Stars,” which provided an overview of the spacecraft systems and technology needed for interstellar flight (with an emphasis on power and propulsion). This summer, the Institute will be holding a series of online events with featured guests that address a wide range of topics, from space medicine and diversity in the space industry to coding and languages.
They also partner with universities to fund research, including their current partnership with Texas A&Ms nuclear engineering department to conduct a detailed white paper study on a portable nuclear reactor that meets the program requirements of Project Pele. This is a program by the U.S. Department of Defense (DoD) to create microreactors to provide power at forward bases for a growing fleet of electrical vessels.
Another interesting example is the support LSI has given to its sister institution, Breakthrough Starshot, which is currently investigating directed-energy propulsion (DEP) to accelerate lightsails to relativistic speeds (a fraction of the speed of light). This research is overseen by Prof. Philip Lubin, head of the Experimental Cosmology Group at U.C. Santa Barbara. This group specializes in directed-energy (laser) technology, with applications ranging from space exploration (NASA’s Starlight program) to planetary defense against asteroids (DE-STAR).
“We awarded Phil Lubin’s group an Interstellar Initiatives grant as part of our inaugural grant cycle of 2020,” said Dr. White. “We paid for some work for him to mature his laser design, have multiple lasers work in cooperation in the field with a cooperative target.” This combination of “inspire, educate, and research” (the three pillars of LSI’s efforts) allows for the mutually-beneficial advancement of technologies and the promotion of future leaders and innovators in the space industry.
Today, many research and non-profit groups are dedicated to making interstellar spaceflight a reality. Examples include Icarus Interstellar, the British Interplanetary Society (BIS), and their spinoff, Tau Zero Foundation. There are also predecessor projects like the previously-mentioned Breakthrough Starshot, which is committed to creating lightsail spacecraft that could reach nearby star systems in our lifetimes and confirm if there are any habitable planets there (and possibly life).
While the aim is to go faster and reach farther, the true purpose is to grow humanity as a species and improve our understanding of life and the cosmos. This will invariably have applications for improving life on Earth, which will emerge far sooner than any FTL concepts. Dr. White, who considers himself a very practical thinker (concerned with “what’s under the hood,” as he put it), still has some philosophical thoughts on how reaching farther out into space will have implications here at home:
“Establishing the capability to send human beings to every destination in the Solar System – think about that. Having an entire Solar System of materials and resources would change the very concept of scarcity. Diamond is rare, but if you have a whole Solar System at your disposal, maybe that changes the definition of what that is. Second, in order to allow and facilitate human beings to go throughout all the destinations in our Solar System, we have to have compact light and very energetic forms of power.
“As we know from life here on Earth, the quality of life is directly tied to how many watts each citizen has at their disposal. Having that capability will also mean that planet Earth will [be in] a much different position when it comes to generating and utilizing power. In a future where we can ‘Go Incredibly Fast’ – within the context of our Solar System or nearby stars – the argument is still similar. It changes the whole concept of scarcity and prosperity.”
Perhaps the most important aspect of the attempts to realize FTL and interstellar travel is the way it inspires people. Knowing that the science behind it is sound and that humanity could one day realize the dream of interstellar travel (within an individual’s lifetime) brings hope to people today. Amid all the bad news of wars, pandemics, insurrections, and climate change, there are many who believe that human civilization will not survive the 21st century. It’s little wonder why many look to space as the solution and the means to our long-term survival.
And for those who would say “we should fix Earth first,” the idea of FTL and interstellar spaceflight offers a counter-argument. What better way to “fix Earth” than by reducing our impact and dependence on it? If and when the entire Solar System is accessible, and nearby stars can be reached in a matter of years (instead of millennia), humanity will have the means to ensure that Earth and our civilization will survive any calamity.
In the immortal words of Konstantin Tsiolkovsky: “Earth is the cradle of humanity, but one cannot live in a cradle forever.” Nuff said?
