Don’t Bother Trying to Destroy Rubble Pile Asteroids

The asteroids in our Solar System are survivors. They’ve withstood billions of years of collisions. The surviving asteroids are divided into two groups: monolithic asteroids, which are intact chunks of planetesimals, and rubble piles, which are made of up fragments of shattered primordial asteroids.

It turns out there are far more rubble pile asteroids than we thought, and that raises the difficulty of protecting Earth from asteroid strikes.

The early days of planetary formation were marked by endless collisions that shattered countless planetesimals. The fragments populate the main asteroid belt and other regions in the inner Solar System. But some of those fragments reassembled into rubble pile asteroids, and surprisingly, they’re more resistant to collisions and harder to destroy than their monolithic brethren.

Rubble-pile asteroids are detectable by their density, which is much lower than monolithic asteroids. Peanut-shaped Itokawa was the first confirmed rubble-pile asteroid, and astronomers think the well-known asteroids Bennu and Ryugu are both rubble-pile asteroids, too. When the Japanese spacecraft Hayabusa visited Itokawa in 2005, images showed that its surface was free of impact craters, a dead giveaway that it was a loose collection of rubble since a monolithic asteroid would most certainly show signs of impacts.

Hayabusa brought home some samples from Itokawa, and a new research article in the Proceedings of the National Academy of Sciences is based on those samples. The article is “Rubble pile asteroids are forever,” and the lead author is Professor Fred Jourdan from the School of Earth and Planetary Sciences at Curtin University.

Itokawa is only about 500 meters long and is about 2 million km (1.2 million miles) from Earth. Hayabusa collected 1500 tiny grains of rock from the asteroid, and they were returned to Earth in June 2010. This research article is based on the study of three of those particles, and thanks to advanced analytical technologies, those three particles revealed a lot.

Scientists think that monolithic asteroids have a lifespan of a few hundred million years. For asteroids in the main belt, it’s even shorter: a few hundred thousand years. There are so many opportunities for collisions in the main belt that few are likely to remain unscathed. But rubble piles aren’t as brittle and can last much longer.

“Unlike monolithic asteroids, Itokawa is not a single lump of rock but belongs to the rubble pile family, which means it’s entirely made of loose boulders and rocks, with almost half of it being empty space,” Professor Jourdan said.

This image from JAXA’s Hayabusa spacecraft shows a boulder on Itokawa’s surface. Hayabusa’s images were the first to show the existence of rubble pile asteroids. JAXA scientists wrote: “This is a very important clue to studying the asteroid’s formation history. It is safe to assume that a larger celestial body originally existed before Itokawa. And on its destruction, a fragment from it became Itokawa as other finer fragments piled on the asteroid surface.” Image Credit: JAXA

While monolithic asteroids can be shattered by collisions, rubble piles are more elastic and can more easily absorb kinetic energy. An impact can alter a rubble pile’s shape without shattering it. The new research shows that Itokawa is extremely ancient—more than four billion years old. It wouldn’t have survived this long unless it was a rubble pile.

“The survival time of monolithic asteroids the size of Itokawa is predicted to be only several hundreds of thousands of years in the asteroid belt,” Jourdan said. “The huge impact that destroyed Itokawa’s monolithic parent asteroid and formed Itokawa happened at least 4.2 billion years ago. Such an astonishingly long survival time for an asteroid the size of Itokawa is attributed to the shock-absorbent nature of rubble pile material.”

“In short, we found that Itokawa is like a giant space cushion and very hard to destroy.”

“Hence, such asteroids represent a major threat to Earth, and we really need to understand them better.”

Fred Jourdan, lead author, School of Earth and Planetary Sciences at Curtin University.

One of the methods the researchers used to study the three Itokawa fragments is called Electron Backscattered Diffraction. It uses an electron microscope to study the crystallographic structure and orientation of the rocks. It can detect misalignment in the crystal structure that results from heat and shocks. Along with other analytical techniques, the analysis showed that the three fragments were “initially located deep in the monolithic parent asteroid,” the paper states.

Deep inside the asteroid, they were protected from all the bombardment and shock heating in the Solar System’s early, chaotic era. These particles were from the surface of Itokawa, and if they’d been there since the early days, they would’ve shown evidence of shock and heating. Collisions are far too plentiful for an asteroid to avoid them. The particles show evidence of only weak shocks and heating. “In order to be affected or subsequently affectable by impact-related thermal events at ~4.2 Ga, the particles would need to be brought near the surface, either by total disruption of the parent body or by deep crater excavations,” the authors explain in their paper.

The research explains Itokawa’s history. 4.6 billion years ago, a monolithic asteroid formed that was Itokaway’s parent body. Between 4.6 and 4.2 billion years ago, successive impacts created progressive fracturing. Then 4.2 billion years ago, one of two things happened. Either an impact excavated a deep crater, or else it totally destroyed the asteroid. In a very short period of time, the debris reformed into Itokawa. Throughout its history since then, Itokawa’s suffered many impacts, but the asteroid’s rubble-pile nature allowed it to absorb those impacts without being cratered or destroyed.

This figure from the study explains Itokawa’s history. Image Credit: Jourdan et al. 2023.

“Argon dating reveals the age of the particles as about 4.2 billion years. “Such a long survival time for an asteroid is attributed to the shock-absorbent nature of rubble pile material and suggests that rubble piles are hard to destroy once they are created,” the authors write.

The results apply to more than only Itokawa. If they’re so much harder to destroy, then there’s likely a much higher population of rubble-pile asteroids than thought. We know that Bennu, Ryugu, and others are rubble-pile asteroids. That has implications for our ability to defend Earth from asteroid strikes.

This image shows Bennu’s boulder-strewn surface. When NASA’s OSIRIS-REx collected samples, the sampling arm sank much deeper into the asteroid than expected, indicating that it’s a rubble-pile asteroid. Image Credit: NASA/University of Arizona.

“We set out to answer whether rubble pile asteroids are resistant to being shocked or whether they fragment at the slightest knock,” Associate Professor and co-author Nicholas Timms said. “Now that we have found they can survive in the solar system for almost its entire history, they must be more abundant in the asteroid belt than previously thought, so there is more chance that if a big asteroid is hurtling toward Earth, it will be a rubble pile.”

In an article in The Conversation, Jourdan emphasized the threat they pose. “In fact, they are very abundant, and since they are the shattered bits of monolithic asteroids, they are relatively small and thus hard to spot from Earth,” he writes. “Hence, such asteroids represent a major threat to Earth, and we really need to understand them better.”

The risk for us is that these asteroids can absorb a lot of kinetic energy. That means that kinetic impactors like in NASA’s DART mission might not effectively direct them away from Earth. “Here, we showed that small rubble pile asteroids can survive billions of years against the ambient bombardment in the inner solar system due to their resistance to collisions and fragmentations. Therefore, more aggressive approaches (e.g., nuclear blast deflection) might have a higher chance of success against rubble pile asteroids,” the authors write in their paper.

More:

• Press Release: Asteroid findings from specks of space dust could save the planet
• Research Article: Rubble pile asteroids are forever
• The Conversation: Our Solar System is filled with asteroids that are particularly hard to destroy, new study finds

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Watch This 12-Year Timelapse of Exoplanets Orbiting Their Star

Back in 2008, astronomers made a big announcement: for the first time, they had taken pictures of a multi-planet solar system, much like ours, orbiting another star. At the time, the star system, named HR8799 was known to have three planets, but follow-up observations a year later revealed a fourth world.

Astronomers have continued to watch this intriguing star system, and now, using observations from the last 12 years, astrophysicist Jason Wang has put together a time lapse video showing the orbital motions of the four planets.

“Astronomical events either happen too quickly or too slowly to capture in a movie,” said Wang.” But this video shows planets moving on a human time scale. I hope it enables people to enjoy something wondrous.”

The dusty young star HR8799 ch is 140 light years away and about 1.5 times the size of our Sun. Even more intriguing is that HR8799 is visible to the naked eye. It has a magnitude 5.96 and it is located inside the western edge of the great square of Pegasus almost exactly halfway between Scheat and Markab.

Location of HR8799. Credit: Wikimedia Commons.

The planets were imaged using high-contrast, near-infrared adaptive optics observations with the Keck and Gemini telescopes. In a press release from Northwestern University, Wang said he was instantly fascinated by the system when the news broke in 2008, and has been watching it ever since. He and his colleagues applied for time on the W. M. Keck Observatory, located on the top of Mauna Kea in Hawaii, to observe the system each year.

Using 12 years of imaging data, Wang put together the time lapse video, which shows the entire time period in a condensed 4.5-second time lapse.

“There’s nothing to be gained scientifically from watching the orbiting systems in a time lapse video, but it helps others appreciate what we’re studying,” Wang said. “It can be difficult to explain the nuances of science with words. But showing science in action helps others understand its importance.”

The image from 2008 of the three exoplanets orbiting HR8779 using Keck Observatory near-infrared adaptive optics. The planets are labeled and the two outer ones have arrows showing the size of their motion over a 4 year period. Credit: Keck Observatory.

The outer planet orbits inside a dusty disk, much like our own Kuiper belt. Astronomers says it is one of the most massive disks known around any star within 300 light years of Earth. There is an additional debris disk just inside the orbit of the innermost planet – which was the fourth planet to be found. Astronomers say that would be room in the inner system for terrestrial planets.  The planet nearest the star takes about 45 Earth years to make one revolution. The farthest planet, on the other hand, takes nearly 500 years to orbit the star.  

Wang and his collaborators aren’t finished making observations of this system, and now are examining the light emitted from the star and its planets in order to better understand what they are made of.

“In astrophysics, most of the time we are doing data analysis or testing hypotheses,” he said. “But this is the fun part of science. It inspires awe.”

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Freezing Ocean Might Not Be Responsible for Cryovolcanic Flows on Pluto’s Moon, Charon

In a recent study scheduled to be published in the journal Icarus in March 2023, a team of researchers led by the Southwest Research Institute (SwRI) modeled a potential correlation between an ancient freezing ocean with cryovolcanic flows and surface canyons on Pluto’s largest moon, Charon. Their hypothesis was that when Charon’s interior ocean froze long ago, the significant stress put on the icy outer shell from the addition of more ice to the bottom of the existing shell could have been responsible for the cryovolcanic flows on the surface.

In the end, the researchers found a freezing interior ocean was likely not responsible for Charon’s cryovolcanic flows due to the ice shell needing to be much thinner than indicated by current models. But if an interior ocean isn’t responsible for Charon’s cryovolcanic flows, then what could be responsible?

“My best guess is that Charon’s thermal evolution and geologic processes created pockets of melt within the ice shell that eventually migrated to the surface,” Dr. Alyssa Rhoden, who is a Principal Scientist at SwRI and lead author of the study, recently told Universe Today. “On moons like Europa, we think of areas with a high concentration of salt, which can affect the melting temperature and density of ice in a local region. On Charon, there are also nitrogen-bearing compounds, like ammonia, that can affect how melt forms and moves through the ice shell.

“It is also possible that the flows were made of oceanic material,” Dr. Rhoden continued. “Our study looked at the combined effects of fracture formation and ocean pressurization that occurs as an ocean freezes out. We found that ocean freezing could not generate both the conduits that connect the ice shell with the ocean and the pressure needed to bring ocean material to the near-surface, unless the ice shell was much MUCH thinner than models suggest it could have been. It’s still possible that fractures were created by some other process (or combination of processes) that enabled ocean material to transit the ice shell. But we can’t simply invoke ocean freezing as the direct path to ocean-sourced eruptions.”

As stated, Charon is the largest moon of Pluto, and is nearly half the size of its parent dwarf planet, making it the largest known satellite relative to its parent body, and is even larger than Pluto’s other four moons combined. The only spacecraft to have visited both Pluto and Charon was NASA’s New Horizons in July 2015, which took incredible images and gave us new insights about both celestial bodies. Despite this flyby happening more than seven years ago, scientists continue to learn more about this mysterious moon, to include its ancient ocean and how it could have affected the surface.

“What this research teaches us is that Charon’s freezing ocean had a more limited role in the development of Charon’s surface geology than has been previously suggested,” Dr. Rhoden recently told Universe Today. “Most likely, Charon’s large canyon systems are the main geologic indicators of ocean freezing.”

As it turns out, Charon isn’t the only ocean-bearing world in our solar system, even though its ocean has long since frozen. Moons like Europa, Enceladus, and Titan have all been examined in-depth regarding their (potential) interior bodies of liquid water. So, can this research teach us anything new about other ocean-bearing worlds in our solar system?

“All ocean worlds should be influenced by the same processes,” Dr. Michael Manga, who is a Professor and Chair of the Department of Earth and Planetary Sciences at UC Berkeley and a co-author on the study, recently told Universe Today. “The differences will be controlled by the size of the world which affects gravity and the thickness of the ice shell. On Enceladus, for example, the small size and this ice shell make it possible to produce cracks the connect the ocean to the surface.”

“Diversity is important! Dr. Rhoden recently exclaimed to Universe Today. “Not just diversity of people and perspectives (which is also critical) but harnessing the power of comparative planetology is key to understanding the properties and processes of icy worlds. Here, we built upon an investigation of Europa and expanded to better understand Enceladus and Charon. And now, we can use our understanding of the effects and limits of ocean freezing to constrain the histories of many other moons in the solar system.”

While several missions have been proposed to return to the Pluto system, there are currently no scheduled missions at this time. What new insights will we continue to unlock regarding Charon and other ocean worlds in the coming years? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!

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South Korea’s Danuri Mission Sends Home Pictures of the Earth and Moon

The Korea Aerospace Research Institute (KARI) both ended 2022 and started 2023 on a very high note as its first-ever lunar orbiter, Danuri, sent back black-and-white images of the Earth with the Moon’s surface in the foreground that were photographed between December 24 and January 1, KARI announced in a January 3^rd statement. Both the images and videos were taken less than 120 kilometers (75 miles) above the Moon’s surface, and will be “used to select potential sites for a Moon landing in 2032,” KARI added in the statement.

As stated, Danuri, also known as the Korea Pathfinder Lunar Orbiter (KPLO), is South Korea’s first-ever lunar orbiter, and was launched on August 4, 2022, onboard a SpaceX Falcon 9 from Cape Canaveral, Florida, and successfully achieved lunar orbit in December 2022. Danuri is slated to begin its scientific mission in February 2023, which has several objectives: analyzing and mapping the lunar surface; measuring gamma rays and magnetic strength; and testing an experimental “space internet” technology by sending images and videos back to Earth, which this most recent image and video cache demonstrated; and identifying potential future landing sites, as noted above.

South Korea’s President Yoon Suk-yeol lauded Danuri’s recent milestones as a “historical moment” in South Korea’s space program.

While Danuri weighs in at 550 kilograms (1212 pounds), the scientific payloads only encompass about 40 kilograms (88 pounds), and consist of several instruments, which include the Lunar Terrain Imager (LUTI), Wide-Angle Polarimetric Camera (PolCam), Magnetometer (KMAG), Gamma-Ray Spectrometer (KGRS), and a NASA-developed high-sensitivity camera (ShadowCam).

ShadowCam is an especially prudent instrument since it will be searching for ice deposits within the Moon’s permanently shadowed regions (PSRs) at the Moon’s poles, and will be beneficial for future exploration, specifically NASA’s Artemis missions which will land astronauts at the lunar south pole later this decade.

KARI has outlined ambitious objectives for outer space, which they refer to as Future Vision 2050, with the goals of landing a spacecraft on the lunar surface by 2032 and Mars by 2045.

As always, keep doing science & keep looking up!

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Soon We’ll Detect Extreme Objects Producing Gravitational Waves Continuously

The cosmic zoo contains objects so bizarre and extreme that they generate gravitational waves. Scorpius X-1 is part of that strange collection. It’s actually a binary pair: a neutron star orbiting with a low-mass stellar companion called V818 Scorpii. The pair provides a prime target for scientists hunting for so-called “continuous” gravitational waves. Those waves should exist, although none have been detected—yet.

“Scorpius X-1 is one of the most promising sources for detecting these continuous gravitational waves,” said Professor John Whelan from Rochester Institute of Technology’s School of Mathematical Sciences. He’s the principal investigator of RIT’s group in the LIGO Scientific Collaboration, part of a group of scientists focused on the direct detection of gravitational waves. LIGO is the Laser Interferometer Gravitational-Wave Observatory, situated in Washington State and Louisiana. Virgo (in Italy) and KAGRA (in Japan) are also searching for gravitational waves, often in conjunction with LIGO.

Hunting for Gravitational Waves at Scorpius X-1

Whelan’s team used data from the third LIGO-Virgo observing run in their search for continuous gravitational waves from Scorpius X-1. “It’s fairly close at only 9,000 light years away,” said Whelan. “We can see it very brightly in x-rays because the gaseous matter from the companion star is pulled onto the neutron star.”

Despite its brightness, the team did not detect a continuous wash of gravitational waves from Scorpius X-1. That doesn’t mean the waves aren’t there. In fact, their data provide important goalposts as they plan more observations of the pair. It helped them improve their search methodology and should eventually result in the detection of these elusive waves.

“This search yielded the best constraint so far on the possible strength of gravitational waves emitted from Scorpius X-1,” said Jared Wofford, an astrophysical sciences and technology Ph.D. candidate. “For the first time, this search is now sensitive to models of the possible torque balance scenario of the system, which states that the torques of the gravitational wave and accretion of matter onto the neutron star are in balance. In the coming years, we expect better sensitivities from more data taken by Advanced LIGO observing runs probing deeper into the torque balance scenario in hopes to make the first continuous wave detection.”

The Scorpius X-1 System

Scorpius X-1 is the strongest x-ray source in our sky (after the Sun). Astronomers discovered it in 1962 when they sent a sounding rocket with an x-ray detector up to space. Over the years, they figured out that its strong x-ray emissions come from a 1.4-solar mass neutron star that’s gobbling up matter streaming from its smaller 0.4-solar-mass companion. The strong gravitational field of the neutron star accelerates the stellar material as it falls onto the star. That superheats the matter and causes it to give off x-rays.

An artist’s conception of a neutron star shows a schematic of its magnetic field and possible jets of material escaping from the poles. In the Scorpius X-1 system, the neutron star is paired with a low-mass star. Material escapes from the smaller star onto the surface of the neutron star. irregularities in the surface of the neutron star may play a role in creating gravitational waves.Credit: Kevin Gill, Attribution 2.0 Generic (CC BY 2.0)

While the system is a strong x-ray emitter and is bright in optical light, it’s actually classified as a low-mass x-ray binary. The two objects have an 18.9-hour orbital period. It’s not clear if they formed together early in their history. Some astronomers suggest they could have come together when a supermassive star and the small companion had a close encounter in a globular cluster environment. The larger companion eventually exploded as a supernova, which created the neutron star.

Using Gravitational Waves to Understand the Scorpius X-1 Binary Pair

Most of us are familiar with gravitational waves generated by the mergers of black holes and/or neutron stars. The first detection of those waves happened in 2015. Since then, LIGO and its sister facilities KAGRA and Virgo have detected these “stronger” waves regularly. It’s important to remember that those detections record specific collisions—essentially “one-off” events. However, they aren’t the only sources of gravitational waves in the universe. Astronomers think that massive objects that spin hundreds of times per second—such as neutron stars—can produce weaker continuous waves that should be detectable.

So, what might cause the waves in a neutron star/companion star binary pair? Look at the outer structure of neutron stars. Scientists describe them as uniformly smooth objects, with strong gravitational and magnetic fields. However, they could have tiny surface irregularities (called “mountains”). These stick out only fractions of a millimeter above the surface of the neutron star’s “crust”. The mountains are really deformations in that crust. They’re created by extreme stresses in the electromagnetic field of the neutron star.

It’s also possible that these deformities happen as the spin of the object slows down. Or, possibly when its spin suddenly speeds up. However they’re formed, they affect the magnetic and gravitational fields of the neutron star. That may be what’s causing the gravitational waves. If so, those mountains may be small, but their influence could be big.

What’s Next

The challenge now is to measure those waves. Eventually, astronomers will detect a constant “wash” of waves coming from Scorpius X-1. Their data will tell them more about the neutron star itself. It should also give clues to the dynamics of the binary pair as the members orbit with respect to each other.

For More Information

RIT scientists reach a milestone in the search for continuous gravitational waves
Model-based Cross-correlation Search for Gravitational Waves from the Low-mass X-Ray Binary Scorpius X-1 in LIGO O3 Data
Modelling Neutron Star Mountains in Relativity
Ligo Scientific Collaboration

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Scientists Examine Geological Processes of Monad Regio on Neptune’s Largest Moon, Triton

In a recent study submitted to the journal Icarus, a team of researchers at the International Research School of Planetary Science (IRSPS) located at the D’Annunzio University of Chieti-Pescara in Italy conducted a geological analysis of a region on Neptune’s largest moon, Triton, known as Monad Regio to ascertain the geological processes responsible for shaping its surface during its history, and possibly today. These include what are known as endogenic and exogenic processes, which constitute geologic processes occurring internally (endo-) and externally (exo-) on a celestial body. So, what new insights into planetary geologic processes can we learn from this examination of Monad Regio?

“Exogenic geological features, such as glaciers, channels, and coastlines, characterize the bodies of the Solar System that possess, or possessed, a dense atmosphere,” Dr. Davide Sulcanese, who is a Junior Scientist within IRSPS and lead author of the study, recently told Universe Today. “The surface of Earth, Mars and Titan contains a large variety of similar features. Surprisingly, we observed that even in one of the farthest and coldest bodies of the Solar System, the icy satellite Triton, the surface can be reshaped by exogenic processes, including deposition and flowing of ice (though in this case we refer to nitrogen ice).

“Such exogenic activity has already been observed on another body of the outer Solar System, Pluto, where the high-resolution images acquired by the New Horizons spacecraft in 2015 revealed for the first time the presence of active glaciers and dendritic channels on its surface,” Dr. Sulcanese continued. “We showed that also the surface of Triton (at least in Monad Regio) could host several ice flow-related features, like glaciers, moraines, ogives, and subglacial channels, that have probably played a fundamental role in the rejuvenation of its surface.”

For the study, the researchers created a geomorphological map at a scale of 1:1,000,000 of an extended area of Monad Regio, meaning the measurement of 1 on their map is equivalent to 1 million of the same measurement on Monad Regio. They then used a combination of images from NASA’s Voyager 2, a roughness map of the study area, and a digital elevation model to conduct their geological analysis of the area. Their findings indicate that an endogenic phase is potentially followed by an exogenic phase, which could help explain the surface features we see today.

“Most of the morphologies we observed on Triton are a consequence of the internal geological activity of the moon, like diapirism, explosive events, faulting, cryovolcanism and consequent flow of cryolava,” Dr. Sulcanese recently told Universe Today. “However, we infer that after this first endogenic phase, some of these landforms in Monad Regio have been further modified by deposition and flow of solid and liquid nitrogen, forming features strikingly similar to terrestrial glaciers, morains, ogives, channels, and even coastlines.” The study notes that while endogenic processes could be responsible for reshaping the surface early in the moon’s evolutionary history, it is the exogenic processes that could be responsible for actively reshaping its surface today.

“The almost total absence of craters on Triton denotes that its surface is extremely young, geologically speaking,” Dr. Sulcanese recently told Universe Today. “This means that there is some kind of process that modified, or perhaps is still modifying, its surface. While in the south polar region of Triton the reason of such rejuvenation is probably attributable to the active geyser-like plumes (observed by the Voyager 2 spacecraft in 1989), in Monad Regio the cause could be the exogenic processes mentioned above.”

NASA’s Voyager 2 spacecraft is still the only spacecraft to have visited Neptune and its largest moon, Triton, meaning the only images we have of Triton are over 30 years old, which Dr. Sulcanese informed Universe Today as being “the challenge of this work.”

“Still now, the only available information we have about the surface of this satellite derives from these images,” Dr. Sulcanese recently told Universe Today. “Many of our findings were made possible thanks to the availability of a Digital Elevation Model (DEM), that we were able to generate here at the International Research School of Planetary Sciences (IRSPS) (University of G. d’Annunzio in Pescara), by applying a technique called photoclinometry. This is to say that, although new space missions are crucial for improving our knowledge of planetary bodies, modern software can help rework old data in a different way and extract new information that was not accessible earlier.”

While there are currently no missions slated to return to Neptune, NASA’s Neptune Odyssey mission was one of the finalists for a NASA Discovery mission, but it was announced in June 2021 that it was not selected, as two missions to Venus, DAVINCI and VERTITAS, were chosen instead.

What new information will we continue to learn about Neptune’s largest moon, Triton, in the coming years, and possibly decades? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!

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Astronomers are Working on a 3D map of Cosmic Dawn

The frontiers of astronomy are being pushed regularly these days thanks to next-generation telescopes and scientific collaborations. Even so, astronomers are still waiting to peel back the veil of the cosmic “Dark Ages,” which lasted from roughly 370,000 to 1 billion years after the Big Bang, where the Universe was shrouded with light-obscuring neutral hydrogen. The first stars and galaxies formed during this same period (ca. 100 to 500 million years), slowly dispelling the “darkness.” This period is known as the Epoch of Reionization, or as many astronomers call it: Cosmic Dawn.

By probing this period with advanced radio telescopes, astronomers will gain valuable insights into how the first galaxies formed and evolved. This is the purpose of the Hydrogen Epoch of Reionization Array (HERA), a radio telescope dedicated to observing the large-scale structure of the cosmos during and before the Epoch of Reionization located in the Karoo desert in South Africa. In a recent paper, the HERA Collaboration reports how it doubled the array’s sensitivity and how their observations will lead to the first 3D map of Cosmic Dawn.

The HERA Collaboration is an international consortium comprised of astronomers and astrophysicists from South Africa, Australia, the U.S., the U.K., Israel, Italy, and India. The research was led by Joshua Dillon, a research scientist at UC Berkeley’s Department of Astronomy and the lead author of the paper. The paper that describes their research and findings recently appeared online and has been accepted for publication by the Astrophysical Journal. Their results provide new insight into how reionization occurred in the early Universe.

A timeline of the cosmos showing which eras will be observed by the Planck satellite, HERA, and NASA’s JWST. Credit: HERA

From Dark to Dawn

Based on current cosmological models, the Universe began 13.8 billion years ago with the Big Bang, which produced a flurry of energy and elementary particles that slowly cooled to create the first protons and electrons (which combined to form the first hydrogen and helium atoms). The leftover “relic radiation” is observable today in the form of the Cosmic Microwave Background (CMB). Thanks to missions like the COBE, WMAP, and Planck, astronomers have mapped the faint variations in temperature that existed 380,000 years after the Big Bang.

Meanwhile, thanks to missions like Hubble, astronomers have observed galaxies as they existed roughly 1 billion years after the Big Bang (ca. 13 billion years ago). This has led to a greater understanding of how galaxies evolved and the possible role of Dark Matter and Dark Energy in the process. However, there is a gap between these observations of the CMB and early galaxies: the aforementioned “Dark Ages” (ca. 370,000 to 1 billion years after the Big Bang). This epoch cannot be studied with conventional telescopes because photons in this period were either part of the CMB or those released by neutral hydrogen atoms – the 21-centimeter hydrogen line.

As the first stars and galaxies gradually formed, the intense radiation they emitted reionized much of the surrounding Universe. This led to the Epoch of Reionization, where neutral hydrogen began to form clouds of plasma of free electrons and protons. To map these bubbles, HERA and other sophisticated radio telescopes were created to observe the hydrogen line (which has a frequency of 1,420 megahertz). This wavelength of light is one that neutral hydrogen absorbs and emits, but ionized hydrogen does not.

Since the Epoch of Reionization, this radiation has been redshifted by the expansion of the Universe to a wavelength of about 2 meters (6 feet). HERA’s simple antennas, built from chicken wire, PVC pipe, and telephone poles, are 14 meters (46 feet) in diameter, allowing them to focus this radiation onto detectors. The backend is where things get sophisticated, consisting of a supercomputer and machine learning algorithms performing advanced data analysis. This map could track galactic evolution from the very early Universe to today.

An artist’s representation of what the first stars to light up the Universe might have looked like in the Cosmic Dawn. Credit: NASA/WMAP Science Team

Latest Analysis

The team’s results showed that the earliest stars, which may have formed around 200 million years after the Big Bang, contained few other elements than hydrogen and helium. The finding is consistent with accepted models of stellar evolution, which state that metals (from lithium to uranium) formed within the first generation of stars. When these stars collapsed after a comparatively short lifespan (hundreds of millions of years rather than billions), these metals were shed with the stars’ outer layers, seeding the Universe with metals that became part of subsequent generations of stars.

Astronomers are interested in the atomic composition of these early stars since this would show how long they took to heat the intergalactic medium (IGM) and cause reionization to occur. A key element here is high-energy radiation (primarily X-rays) produced by binary stars once one of them goes supernova, collapsing into a black hole or neutron star and eventually consuming their companion. Since the earliest stars had very few heavy elements (low metallicity), they would not have heated the surrounding region much and produced fewer X-rays.

Ultimately, the HERA Collaboration did not find the signal these bubbles would have emitted in the data. According to Aaron Parsons, the principal investigator for HERA, an associate professor of astronomy at UC Berkeley, and the director of its Radio Astronomy Laboratory, this rules out some theories of how stars evolved in the early Universe. “Early galaxies have to have been significantly different than the galaxies that we observe today for us not to have seen a signal,” he said. “In particular, their X-ray characteristics have to have changed. Otherwise, we would have detected the signal we’re looking for.”

The absence of the signal largely rules out the “Cold Reionization” theory, which posits that reionization had a colder starting point. Instead, the HERA researchers suspect that the X-rays from binary stars heated the intergalactic medium (IGM) first. Said Joshua Dillon, a research scientist at UC Berkeley’s Department of Astronomy and lead author of the paper:

“Our results require that even before reionization and by as late as 450 million years after the Big Bang, the gas between galaxies must have been heated by X-rays. These likely came from binary systems where one star loses mass to a companion black hole. Our results show that if that’s the case, those stars must have been very low ‘metallicity,’ that is, very few elements other than hydrogen and helium in comparison to our sun, which makes sense because we’re talking about a period in time in the Universe before most of the other elements were formed.”

Artist’s impression of GNz7q, the earliest galaxy ever observed by the Hubble Space Telescope. Credit: NASA/ESA/N. Bartmann

These findings agree with the preliminary results from the first analysis of HERA data (reported last year) that hinted that alternative theories like “Cold Reionization” were unlikely. These results were based on 18 nights of observation by Phase I of the HERA project (about 40 antennas) and were the most sensitive observations of the early Universe to date. This latest is based on 94 nights of Phase I observations (between 2017 and 2018) and demonstrates how the HERA team has improved the array’s sensitivity.

This includes a 2.1-factor increase for light emitted about 650 million years after the Big Bang (a redshift value (z) of 7.9) and a 2.6-factor increase for radiation emitted about 450 million years after the Big Bang (z=10.4). This represents a great step forward for the project and astronomers’ understanding of the early Universe. According to Eloy de Lera Acedo, an astrophysicist from the University of Cambridge’s Cavendish Astrophysics, these latest observations are the “best evidence we have of heating of the intergalactic medium by early galaxies.”

Looking Ahead

The HERA team continues to improve the telescope’s calibration and data analysis in the hopes of seeing the predicted ionization bubbles in the early Universe. Filtering out the local radio noise to see the radiation of the early Universe remains a challenge since the radio emissions from this era are about one-millionth the intensity of radio noise in the vicinity of Earth. When all of HERA’s radio dishes are online and fully calibrated, the team hopes to construct a 3D map of the ionized and neutral hydrogen bubbles from ca. 200 million to 1 billion years after the Big Bang.

Once that is complete, the HERA Collaboration and other astronomers expect to see a “Swiss-cheese” pattern in the early Universe, where galaxies make holes in a neutral hydrogen background. Said Dillion:

“This is moving toward a potentially revolutionary technique in cosmology. Once you can get down to the sensitivity you need, there’s so much information in the data. A 3D map of most of the luminous matter in the universe is the goal for the next 50 years or more. What we’ve done is we’ve said the cheese must be warmer than if nothing had happened. If the cheese were really cold, it turns out it would be easier to observe that patchiness than if the cheese were warm.”

The Milky Way Galaxy in the nighttime sky above the HERA array. Credit: Dara Storer

Other cutting-edge telescopes are allowing astronomers to peer into the early Universe. This includes the Canadian Hydrogen Intensity Mapping Experiment (CHIME) in British Columbia, which is also observing the 21-cm hydrogen line to study how the Universe evolved. There’s also the James Webb Space Telescope (JWST), which observed a galaxy that existed about 325 million years after the Big Bang this past summer. This established a new record for the earliest galaxy ever observed. However, the JWST can only observe the brightest galaxies from this epoch, while arrays like HERA and CHIME continue to probe the “darker” regions of the early Universe.

“HERA is continuing to improve and set better and better limits,” said Parsons. “The fact that we’re able to keep pushing through, and we have new techniques that are continuing to bear fruit for our telescope, is great.”

Further Reading: University of Berkeley, arXiv

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Future Space Telescopes Could be 100 Meters Across, Constructed in Space, and Then Bent Into a Precise Shape

It is an exciting time for astronomers and cosmologists. Since the James Webb Space Telescope (JWST), astronomers have been treated to the most vivid and detailed images of the Universe ever taken. Webb‘s powerful infrared imagers, spectrometers, and coronographs will allow for even more in the near future, including everything from surveys of the early Universe to direct imaging studies of exoplanets. Moreover, several next-generation telescopes will become operational in the coming years with 30-meter (~98.5 feet) primary mirrors, adaptive optics, spectrometers, and coronographs.

Even with these impressive instruments, astronomers and cosmologists look forward to an era when even more sophisticated and powerful telescopes are available. For example, Zachary Cordero 
of the Massachusetts Institute of Technology (MIT) recently proposed a telescope with a 100-meter (328-foot) primary mirror that would be autonomously constructed in space and bent into shape by electrostatic actuators. His proposal was one of several concepts selected this year by the NASA Innovative Advanced Concepts (NIAC) program for Phase I development.

Corder is the Boeing Career Development Professor in Aeronautics and Astronautics at MIT and a member of the Aerospace Materials and Structures Lab (AMSL) and Small Satellite Center. His research integrates his expertise in processing science, mechanics, and design to develop novel materials and structures for emerging aerospace applications. His proposal is the result of a collaboration with Prof. Jeffrey Lang (from MIT’s Electronics and the Microsystems Technology Laboratories) and a team of three students with the AMSL, including Ph.D. student Harsh Girishbhai Bhundiya.

Their proposed telescope addresses a key issue with space telescopes and other large payloads that are packaged for launch and then deployed in orbit. In short, size and surface precision tradeoffs limit the diameter of deployable space telescopes to the 10s of meters. Consider the recently-launched James Webb Space Telescope (JWST), the largest and most powerful telescope ever sent to space. To fit into its payload fairing (atop an Ariane 5 rocket), the telescope was designed so that it could be folded into a more compact form.

This included its primary mirror, secondary mirror, and sunshield, which all unfolded once the space telescope was in orbit. Meanwhile, the primary mirror (the most complex and powerful ever deployed) measures 6.5 meters (21 feet) in diameter. Its successor, the Large UV/Optical/IR Surveyor (LUVOIR), will have a similar folding assembly and a primary mirror measuring 8 to 15 meters (26.5 to 49 feet) in diameter – depending on the selected design (LUVOIR-A or -B). As Bhundiya explained to Universe Today via email:

“Today, most spacecraft antennas are deployed in orbit (e.g., Northrop Grumman’s Astromesh antenna) and have been optimized to achieve high performance and gain. However, they have limitations: 1) They are passive deployable systems. I.e. once you deploy them you cannot adaptively change the shape of the antenna. 2) They become difficult to slew as their size increases. 3) They exhibit a tradeoff between diameter and precision. I.e. their precision decreases as their size increases, which is a challenge for achieving astronomy and sensing applications that require both large diameters and high precision (e.g. JWST).”

While many in-space construction methods have been proposed to overcome these limitations, detailed analyses of their performance for building precision structures (like large-diameter reflectors) are lacking. For the sake of their proposal, Cordero and his colleagues conducted a quantitative, system-level comparison of materials and processes for in-space manufacturing. Ultimately, they determined that this limitation could be overcome using advanced materials and a novel in-space manufacturing method called Bend-Forming.

This technique, invented by researchers at the AMSL and described in a recent paper co-authored by Bhundiya and Cordero, relies on a combination of Computer Numerical Control (CNC) deformation processing and hierarchical high-performance materials. As Harsh explained it:

“Bend-Forming is a process for fabricating 3D wireframe structures from metal wire feedstock. It works by bending a single strand of wire at specific nodes and with specific angles, and adding joints to the nodes to make a stiff structure. So to fabricate a given structure, you convert it into bending instructions which can be implemented on a machine like a CNC wire bender to fabricate it from a single strand of feedstock. The key application of Bend-Forming is to manufacture the support structure for a large antenna on orbit. The process is well-suited for this application because it is low-power, can fabricate structures with high compaction ratios, and has essentially no size limit.”

In contrast to other in-space assembly and manufacturing approaches, Bend-Forming is low-power and is uniquely enabled by the extremely low-temperature environment of space. In addition, this technique enables smart structures that leverage multifunctional materials to achieve new combinations of size, mass, stiffness, and precision. Additionally, the resulting smart structures leverage multifunctional materials to achieve unprecedented combinations of size, mass, stiffness, and precision, breaking the design paradigms that limit conventional truss or tension-aligned space structures.

In addition to their native precision, Large Bend-Formed structures can use their electrostatic actuators to contour a reflector surface with sub-millimeter precision. This, said Harsh, will increase the precision of their fabricated antenna in orbit:

“The method of active control is called electrostatic actuation and uses forces generated by electrostatic attraction to precisely shape a metallic mesh into a curved shape which acts as the antenna reflector. We do this by applying a voltage between the mesh and a ‘command surface’ which consists of the Bend-Formed support structure and deployable electrodes. By adjusting this voltage, we can precisely shape the reflector surface and achieve a high-gain, parabolic antenna.”

An arrangement of 3 exoplanets to explore how the atmospheres can look different based on the chemistry present and incoming flux. Credit: Jack H. Madden used with permission

Harsh and his colleagues deduce that this technique will allow for a deployable mirror measuring more than 100 meters (328 ft) in diameter that could achieve a surface precision of 100 m/m and a specific area of more than 10 m²/kg. This capability would surpass existing microwave radiometry technology and could lead to significant improvements in storm forecasts and an improved understanding of atmospheric processes like the hydrologic cycle. This would have significant implications for Earth Observation and exoplanet studies.

The team recently demonstrated a 1-meter (3.3 ft) prototype of an electrostatically-actuated reflector with a Bend-Formed support structure at the 2023 American Institute of Aeronautics and Astronautics (AIAA) SciTech Conference, which ran from January 23rd to 27th in National Harbor, Maryland. With this Phase I NIAC grant, the team plans to mature the technology with the ultimate aim of creating a microwave radiometry reflector.

Looking ahead, the team plans to investigate how Bend-Forming can be used in geostationary orbit (GEO) to create a microwave radiometry reflector with a 15km (9.3 mi) field of view, a ground resolution of 35km (21.75 mi) and a proposed frequency span of 50 to 56 GHz – the super-high and extremely-high frequent range (SHF/EHF). This will enable the telescope to retrieve temperature profiles from exoplanet atmospheres, a key characteristic allowing astrobiologists to measure habitability.

“Our goal with the NIAC now is to work towards implementing our technology of Bend-Forming and electrostatic actuation in space,” said Harsh. “We envision fabricating 100-m diameter antennas in geostationary orbit with have Bend-Formed support structure and electrostatically-actuated reflector surfaces. These antennas will enable a new generation of spacecraft with increased sensing, communication, and power capabilities.”

Further Reading: NASA

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NASA has Simulated a Tiny Piece of the Moon Here on Earth

Before going to the Moon, the Apollo astronauts trained at various sites on Earth that best approximated the lunar surface, such as the volcanic regions Iceland, Hawaii and the US Southwest.  To help prepare for upcoming robotic and the human Artemis missions, a newly upgraded “mini-Moon” lunar testbed will allow astronauts and robots to test out realistic conditions on the Moon including rough terrain and unusual sunlight.

The Lunar Lab and Regolith Testbed at the Ames Research Center in California simulates conditions on the Moon in a high-fidelity environment, allowing researchers to test hardware designs intended for the lunar surface. The lab is currently being used as a test environment for the next phases of the Artemis Program, to conduct studies on optical sensing and drill testing, and tests for in-situ resource utilization identification and extraction techniques.

A look at the lighting system for Lunar Lab and Regolith Testbeds. Credit: NASA/Uland Wong.

The facility was originally built in 2009 but has now been expanded and upgraded to include a lunar lab with multiple testbeds with a variety of simulated lunar regolith. These large indoor “sandboxes” can be configured and customized to simulate various regions on the Moon. In addition, a special lighting system can re-create realistic lighting conditions on the Moon, such as the darkness of a lunar polar crater, or the glaring rays of the Sun that the Apollo astronauts had to deal with in the lunar mares.

The testbeds aren’t huge, but big enough to provide a variety of conditions. The first original sandbox measures approximately 13 feet by 13 feet by 1.5 feet (4 meters by 4 meters by 0.5 meter) and is filled with eight tons a lunar regolith simulant called Johnson Space Center One simulant (JSC-1A), which makes this the world’s largest collection of the material. The JSC-1A simulant mimics the Moon’s mare basins and is dark grey in color.

The new larger testbed, measures 62 feet by 13 feet by 1 foot (19 meters by 4 meters by 0.3 meter) and is  filled with more than 20 tons of Lunar Highlands Simulant-1 (LHS-1), which is light grey to simulate the lunar highlands. This larger sandbox can be reconfigured if needed to be a smaller, but deeper, testbed.

Some of the things tested are how various tools and rovers work in the incredibly abrasive and “sticky” regolith. Moon dust has grains as fine as powder, but it can also be sharp as tiny shards of glass. In addition, it has the annoying ability to electrostatically cling to everything.

The special lighting system can mimic both the dark polar regions of the Moon and the glaring, unfiltered light elsewhere on the Moon.

“When rovers and astronauts carry out missions at the lunar South Pole, they’ll have to navigate in low-angle lighting and overcome harsh solar glare that makes it difficult to see,” NASA said in a press release. “Because the Sun will never rise overhead, even the smallest rock or crater will cast long shadows and cloak craters in darkness. And, at times, the Sun will blaze at eye-level as it reflects off the soil.”

In the Regolith Testbeds at NASA’s Ames Research Center, which are designed to mimic lunar terrain as it would appear in different areas at the Moon’s poles, the VIPER team tests out lighting systems for the rover with a very low-angle illumination simulating the Sun. Credit: NASA/Dominic Hart

The new testbeds have been instrumental in testing out NASA’s new Moon rover, the Volatiles Investigating Polar Exploration Rover (VIPER). VIPER’s rover drivers will rely on a system of rover-mounted lights and cameras to steer clear of boulders, descend steep declines into craters, and avoid other potentially mission-ending dangers. The facilities at the Regolith Testbed  allowed research teams create over 12 different scenarios of craters and rock formations to improve the rover’s autonomous navigation system, so it can navigate safely through unknown terrain and harsh conditions.

An artist’s concept of the completed design of NASA’s Volatiles Investigating Polar Exploration Rover, or VIPER. VIPER will get a close-up view of the location and concentration of ice and other resources at the Moon’s South Pole, bringing us a significant step closer to NASA’s ultimate goal of a long-term presence on the Moon. Credits: NASA/Daniel Rutter

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Astronomers Prepare to Launch LuSEE Night, A Test Observatory on the Far Side of the Moon

Astronomers have not yet been able to map large portions of the radio emissions from our universe because of interference from the Earth itself. A team of astronomers hopes to change that, beginning with the LuSEE Night mission to the far side of the Moon. It will launch in 2025 and chart a new pathway to Lunar observatories.

The Earth is really loud in the radio, especially at frequencies below 20 megahertz. The ionosphere of the planet itself crackles at those frequencies, obscuring radio emissions from more distant sources. Plus we use low frequency radio waves for communication and radar searches, swamping cosmic sources.

The only way to mitigate all that terrestrial contamination is to get up and away from it. The best place is the far side of the Moon, so that the bulk of the Moon’s body blocks out radio emissions from the Earth. The Sun itself is also a rather loud emitter of radio signals at those frequencies, so the best time to observe is during the Lunar night, when the far side of the Moon is plunged in darkness.

But building radio observatories on the far side of the Moon is no easy task, so we have to start small. One of the first steps is LuSEE Night, the Lunar Surface Electromagnetic Explorer, a small radio antenna and instrument package that is scheduled to be delivered to the far side of the Lunar surface as early as 2025.

LuSEE Night owes its technological heritage to the Parker Solar Probe, and is in fact nearly an identical copy of one of the instruments onboard that spacecraft. LuSEE Night consists of two 6m long antenna set in a cross-shaped pattern along with a bare bones set of electronics. 

In observing mode the instrument is relatively quiet, so it doesn’t add to any radio contamination. It can then send up any data to an orbiting Lunar spacecraft which sends the data back to Earth.

The team behind LuSEE Night hopes to capture some of the first observations of the very low frequency radio universe, which includes emissions from cosmic rays spiraling around the magnetic fields of the Milky Way galaxy and distant bright sources like supernovae and white dwarfs.

LuSEE Night is just the first step. The astronomers hope that it will prove to be a success, so that future observatories and missions on the Lunar far side can open up new windows into the cosmos.

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Astronomers Find 25 Fast Radio Bursts That Repeat on a Regular Basis

Like Gravitational Waves (GWs) and Gamma-Ray Bursts (GRBs), Fast Radio Bursts (FRBs) are one of the most powerful and mysterious astronomical phenomena today. These transient events consist of bursts that put out more energy in a millisecond than the Sun does in three days. While most bursts last mere milliseconds, there have been rare cases where FRBs were found repeating. While astronomers are still unsure what causes them and opinions vary, dedicated observatories and international collaborations have dramatically increased the number of events available for study.

A leading observatory is the Canadian Hydrogen Intensity Mapping Experiment (CHIME), a next-generation radio telescope located at the Dominion Radio Astrophysical Observatory (DRAO) in British Columbia, Canada. Thanks to its large field of view and broad frequency coverage, this telescope is an indispensable tool for detecting FRBs (more than 1000 sources to date!) Using a new type of algorithm, the CHIME/FRB Collaboration found evidence of 25 new repeating FRBs in CHIME data that were detected between 2019 and 2021.

The CHIME/FRB Collaboration comprises astronomers and astrophysicists from Canada, the U.S., Australia, Tawain, and India. Its partner institutions include the DRAO, the Dunlap Institute for Astronomy and Astrophysics (DI), the Perimeter Institute for Theoretical Physics, the Canadian Institute for Theoretical Astrophysics (CITA), the Anton Pannekoek Institute for Astronomy, the National Radio Astronomy Observatory (NRAO), the Institute of Astronomy and Astrophysics, the National Centre for Radio Astrophysics (NCRA), and the Tata Institute of Fundamental Research (TIFR), and multiple Universities and institutes.

Despite their mysterious nature, FRBs are ubiquitous and the best estimates indicate that events arrive at Earth roughly a thousand times a day over the entire sky. None of the theories or models proposed to date can fully explain all the properties of the bursts or the sources. While some are believed to be caused by neutron stars and black holes (attributable to the high energy density of their surroundings), others continue to defy classification. Because of this, other theories persist, ranging from pulsars and magnetars to GRBs and extraterrestrial communications.

CHIME was originally designed to measure the expansion history of the Universe through the detection of neutral hydrogen. Roughly 370,000 years after the Big Bang, the Universe was permeated by this gas, and the only photons were either the relic radiation from the Big Bang – the Cosmic Microwave Background (CMB) – or that released by neutral hydrogen atoms. For this reason, astronomers and cosmologists refer to this period as the “Dark Ages,” which ended roughly 1 billion years after the Big Bang as the first stars and galaxies began reionizing neutral hydrogen (the Reionization Era).

Specifically, CHIME was designed to detect the wavelength of light that neutral hydrogen absorbs and emits, known as the 21-centimeter hydrogen line. This way, astronomers could measure how fast the Universe was expanding during the “Dark Ages” and make comparisons to later cosmological eras that are observable. However, CHIME has since proven itself to be ideally suited for studying FRBs, thanks to its wide field of view and the range of frequencies it covers (400 to 800 MHz). This is the purpose of the CHIME/FRB Collaboration, which is to detect and characterize FRBs and trace them back to their sources.

As Dunlap Postdoctoral Fellow and lead author Ziggy Pleunis told Universe Today, each FRB is described by its position in the sky and a quantity known as its Dispersion Measure (DM). This refers to the time delay from high to low frequencies caused by the burst’s interactions with material as it travels through space. In a paper released in August 2021, the CHIME/FRB Collaboration presented the first large-sample catalog of FRBs containing 536 events detected by CHIME between 2018 and 2019, including 62 bursts from 18 previously reported repeating sources.

Artist‘s impression of a fast radio burst and the observatories dedicated to detecting them. Credit: Danielle Futselaar

For this latest study, Pleunis and his colleagues relied on a new clustering algorithm that looks for multiple events co-located in the sky with similar DMs. “We can measure the fast radio burst’s sky position and dispersion measure up to a certain precision that depends on the design of the telescope that’s being used,” said Pleunis. “The clustering algorithm considers all fast radio bursts that the CHIME telescope has detected and looks for clusters of FRBs that have consistent sky positions and dispersion measures within the measurement uncertainties. We then do various checks to make sure the bursts in a cluster are really coming from the same source.”

Of the over 1000 FRBs detected to date, only 29 were identified as repeating in nature. What’s more, virtually all repeating FRBs were found to be repeating in irregular ways. The only exception is FRB 180915, discovered by researchers at CHIME in 2018 (and reported on in 2020) and pulses every 16.35 days. With the help of this new algorithm, the CHIME/FRB collaboration detected 25 new repeating sources, almost doubling the number available for study. In addition, the team noted some very interesting features that could provide insight into their causes and characteristics. As Pleunis added:

“When we carefully count all our fast radio bursts and the sources that repeat we find that only about 2.6% of all fast radio bursts that we discover repeat. For many of the new sources we have detected only a few bursts, which makes the sources quite inactive. Almost as inactive as the sources that we have only seen once.

“We thus cannot rule out that the sources for which we have so far only seen one burst, will eventually show repeat bursts as well. It is possible that all fast radio burst sources eventually repeat, but that many sources are not very active. Any explanation for fast radio bursts should be able to explain why some sources are hyperactive while others are mostly quiet.”

An illustration of CHIME detecting Fast Radio Bursts (FRBs) in the night sky. Credit: James Josephides/Mike Dalley

These findings could help inform future surveys, which will benefit from next-generation radio telescopes that will become operational in the coming years. These include the Square Kilometer Array Observatory (SKAO), which is expected to gather its first light by 2027. Located in Australia, this 128-dish telescope will be merged with the MeerKAT array in South Africa to create the world’s largest radio telescope. In the meantime, the prodigious rate at which new FRBs are being detected (including repeating events) could mean that radio astronomers could be close to a breakthrough!

Further Reading: arXiv

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Molecular Clouds Have Long Lives By Constantly Reassemble Themselves

Astronomers have recently discovered that giant clouds of molecular hydrogen, the birthplace of stars, can live for tens of millions of years despite the facts that individual molecules are constantly getting destroyed and reassembled. This new research helps place a crucial piece of understanding in our overall picture of how stars are born.

In order to make stars you first need giant clouds of molecular hydrogen gas. These are the reservoirs that can undergo catastrophic collapse. When this happens dozens or even hundreds of stars can appear at once. Without these reservoirs of gas, you can’t make stars, and so astronomers are especially interested in how these clouds behave. The evolution of these clouds within a galactic environment can tell us about the star formation history of the galaxy.

Recent observations have shown that when new stars appear within a giant molecular cloud, they quickly blow out bubbles surrounding themselves. With the reduced density of molecules surrounding those stars, the remaining molecules suffer bombardment from ionizing radiation, breaking apart the molecular hydrogen into an ionized state. 

But other observations have shown that these giant clouds last for incredibly long times. So how can that be if newly born stars constantly tear apart their parent clouds?

A team of researchers turned to sophisticated computer simulations to answer the question. They simulated a portion of a galaxy and examined the behavior of molecular clouds as stars formed within them. They found that their simulations agreed with observations: that newborn stars can easily tear apart a molecular cloud. But they also found a balancing factor. Giant molecular clouds constantly vacuum up any surrounding hydrogen that happens to be wandering by in the galaxy. This action of accumulation replenishes the cloud’s stock of hydrogen.

The researchers found that individual molecular clouds can live for up to almost 100 million years. But any individual hydrogen molecule will last only up to four million years within that cloud before it disassociates. But for every molecule that evaporates a new one enters the cloud, keeping everything in balance. As long as a cloud can keep accumulating material, it will continue living.

These results explain how giant molecular clouds can live so long despite their individual molecules disappearing. And since these giant molecular clouds are the birthplaces of stars, this research helps paint the picture of how galaxies can continue manufacturing stars for billions of years.

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Nuclear Rocket In 2027, JWST Problems, Starship WDR

Starship completes its wet-dress rehearsal, another problem for Webb, a nuclear rocket test is coming, and more cool NIAC grants.

Starship Wet Dress Rehersal

SpaceX made another important step towards the first orbital test of Starship. This week they performed a full wet-dress rehearsal, meaning that both stacked Starship and Super Heavy booster were filled up with fuel, just as if they were going to launch. The test was successful. Now Ship 24 was taken off the booster and SpaceX are getting ready to perform a test fire of all the 33 Raptor v2 engines of Super Heavy.

Webb’s NIRISS Problems

This week NASA announced that they’re taking the James Webb Space Telescope’s Near Infrared IMager and Slitless Spectrograph offline. According to the agency, the instrument experienced an internal communications error that caused its software to time out. It doesn’t seem like the device is damaged in any way; just experiencing this internal error. NIRISS is a Canadian-built infrared instrument that can act like a camera but also has additional modes that let it characterize exoplanet atmospheres and the light of distant galaxies. We don’t know when the instrument will return to operation.

More about NIRISS going offline.

Webb’s First Occultation

Asteroid Chariklo is one of the few worlds in the Solar System that have rings. They were originally discovered back in 2013 but now Webb had a chance to have a look at them. This was made possible because of an event called an occultation. The asteroid crossed the path of a bright background star. So, by observing dips in the brightness of the star, astronomers were able to observe Chariklo’s rings and study them in more detail.

More about Chariklo’s rings by JWST.

DARPA Nuclear Rocket Test by 2027

Nuclear Thermal Propulsion rockets (NTPs) were first tested by NASA and the Department of Energy 50 years ago. They use a fission reactor to heat a propellant like hydrogen and blast it out the back of the rocket with high velocity. Although we know the technology works, we’ve never seen it tested in space before. NASA announced a partnership with DARPA that will construct a working NTP and launch it into space for a test in 2027. A rocket like this could decrease flight times to Mars by months, maybe even completing the journey within 45 days.

More about upcoming nuclear engine test.

How to Miniaturize Nuclear Batteries

One of the problems of deep space missions is power. Once you go past Jupiter, solar power is no longer enough. So, the solution that is currently available is an RTG powered by decaying Plutonium. However, they are big, expensive and not very efficient. One of the NIAC grants that were awarded this year aims to solve this problem. The plan is to shrink RTGs from 200 litres to about 0.2 litres and increase their efficiency. If this can be achieved, this can change future space missions forever. If RTGs will be available for cubesat-sized missions, we will definitely see much more exploration of our Solar System.

More about shrinking space RTGs.

Tiny Tractor Beam

Tractor beams are a staple in science fiction, with spacecraft pulling objects with a beam of light. Like most ideas in science fiction, there’s a grain of truth, and scientists are working on ways to make them a reality. You have to scale your expectations down, way down. There are microscopic tractor beams already in use in science labs called “optical tweezers,” using lasers to move tiny objects around like atoms and nanoparticles. Now researchers have demonstrated a larger version with three orders of magnitude more light pressure.

More about the real-life tractor beam.

Growing Structures on Mars

Travelling to Mars will require living off the land and harvesting the local resources to stay alive. There’s plenty of raw regolith to work with, but how can you turn it into valuable structures like roads, landing pads, and buildings? A new NIAC study is looking into a method for building bricks on Mars using a combination of cyanobacteria and fungi to serve as binding agents to hold the regolith together. The regolith is put into a mold inside a bioreactor, and the bacteria and fungi grow together into a living cement.

More about growing Mars habitats.

Light Pollution Is Getting Worse

A recent study by the Globe At Night program shows that light pollution on Earth is getting progressively worse. Fewer and fewer people have access to the proper night sky. For the past 11 years, the situation was getting about 10% worse each year. One of the main problems causing this trend is advancements in LED technology. Instead of saving power by using more efficient lights, people tend to use same amount of power and increase light output.

More about light pollution on Earth.

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