The planets in our Solar System all rotate on axes that roughly match the Sun’s rotational axis. This agreement between the axes of rotation is the typical arrangement in any system in space where smaller objects orbit a larger one.
But in one distant binary system, the large central object has an axis of rotation tilted about 40 degrees compared to its smaller satellite. This situation is even more strange because the main body isn’t a star but a black hole.
The Sun and the planets formed from the same cloud of gas. Things naturally rotate in our Universe, and the Sun is no exception. As it rotated, the gas and dust in its solar nebula naturally began to rotate, too. It spread out into a pancake shape called a protoplanetary disk. Inside that disk, individual planets formed, and their orbital path around the Sun matches the Sun’s rotational axis with only slight variations.
But in a distant binary object called MAXI J1820+070, something’s amiss. A companion star orbits a stellar-mass black hole, but the black hole’s spin axis is different than the star’s orbital plane by 40 degrees. What could’ve caused the black hole to tilt like this?
“The expectation of alignment, to a large degree, does not hold for the bizarre objects such as black hole X-ray binaries,” said Juri Poutanen, Professor of Astronomy at the University of Turku and the lead author of a new paper. The paper is “Extreme black hole spin–orbit misalignment in x-ray binary MAXI J1820+070.” It’s published in the journal Science.
MAXI J1820+070 is a fairly well-studied object. It’s a binary x-ray source about 10,000 light-years away. The donor star is likely a subgiant with a radius not much larger than our Sun.
This image shows the Milky Way with MAXI-J1820+070’s position marked by a white cross. The inset image is a Chandra X-ray Observatory image of the binary object. Image Credit: Chandra X-ray Observatory ACIS Image
MAXI J1820+070 is known for its energetic outbursts. The outbursts happen when the black hole accretes material from its companion star, or donor star, and emits jets of x-rays from its poles at near light speed. MAXI J1820+070 was discovered in 2018 by the MAXI (Monitor of All-sky X-ray Image) instrument on the ISS.
Usually, two characteristics define astrophysical black holes: mass and spin. But in a binary pair, other aspects emerge. They are the mass accretion rate or the rate that the black hole accretes matter from its companion and the misalignment between the black hole’s spin and the orbital spin.
The mass accretion creates the jets, and by monitoring the jets, astrophysicists learn a lot about the black hole. “Now we see the black hole dragging matter from the nearby, lighter companion star orbiting around it. We see bright optical and X-ray radiation as the last sigh of the infalling material, and also radio emission from the relativistic jets expelled from the system,” Poutanen said in a press release.
The relativistic jets of material give scientists a way to study the system. The jets aren’t steady over time, and by measuring their active and less active states, the researchers determined the black hole’s rotational axis.
The MAXI instrument on the ISS discovered the binary when the jets were energetically active. But that activity lessened as less material flowed to the black hole from the donor star. As the jets from the black hole dimmed, more of the light from the system came from the donor star. That allowed Poutanen and his colleagues to measure the orbital inclination with spectroscopy. They found that the orbital inclination nearly coincided with the inclination of the ejections.
“To determine the 3D orientation of the orbit, one additionally needs to know the position angle of the system on the sky, meaning how the system is turned with respect to the direction to the North on the sky. This was measured using polarimetric techniques,” said Poutanen.
“Together with a previously obtained orientation of the relativistic jet and the inclination of the orbit, this
allowed us to determine a lower limit of 40 degrees on the misalignment angle,” the authors explained in their paper.
This figure from the paper shows the probability distribution function for the misalignment angle. The red hatched region corresponds to the 68% confidence interval. Image Credit: Poutanen et al. 2022
There are different models for black hole formation and the evolution of binary systems like MAXI J1820+070. But it’s difficult for any of them to account for such a wide misalignment. “The large degree
of misalignment puts strong constraints on the supernova explosion and black hole formation
mechanisms, as it can only decrease during the accretion stage,” the authors write in their paper.
“The observed difference of ? 44? between the jet position angles and the PA (polarization angle) gives the first direct observational evidence for a large, at least ? 40?, misalignment between the black hole spin and the orbital angular momentum,” the authors write.
“The difference of more than 40 degrees between the orbital axis and the black hole spin was completely unexpected. Scientists have often assumed this difference to be very small when they have modelled the behaviour of matter in a curved time-space around a black hole. The current models are already really complex, and now the new findings force us to add a new dimension to them,” Poutanen states.
The Great Pyramid of Giza might be the most iconic structure humans ever built. Ancient civilizations constructed archaeological icons that are a testament to their greatness and persistence. But in some respects, the Great Pyramid stands alone. Of the Seven Wonders of the Ancient World, only the Great Pyramid stands relatively intact.
A team of scientists will use advances in High Energy Physics (HIP) to scan the Great Pyramid of Khufu at Giza with cosmic-ray muons. They want to see deeper into the Great Pyramid than ever before and map its internal structure. The effort is called the Explore the Great Pyramid (EGP) mission.
The Great Pyramid of Giza has stood since the 26th century BC. It’s the tomb of the Pharoah Khufu, also known as Cheops. Construction took about 27 years, and it was built with about 2.3 million blocks of stone—a combination of limestone and granite—weighing in at about 6 million tons. For over 3,800 years, it was the tallest human-made structure in the world. We see now only the underlying core structure of the Great Pyramid. The smooth white limestone casing was removed over time.
The Great Pyramid is well-studied, and over the years, archaeologists have mapped out the interior structure. The pyramid and the ground under it contain different chambers and passageways. Khufu’s (Cheops’) chamber sits roughly in the pyramid’s center.
This figure is an elevation diagram of the interior structures of the Great Pyramid. The inner and outer lines indicate the pyramid’s present and original profiles. 1. Original entrance 2. Robbers’ Tunnel (tourist entrance) 3, 4. Descending Passage 5. Subterranean Chamber 6. Ascending Passage 7. Queen’s Chamber & its “air-shafts” 8. Horizontal Passage 9. Grand Gallery 10. King’s Chamber & its “air-shafts” 11. Grotto & Well Shaft. Image Credit: By Flanker, CC BY-SA 3.0, https://ift.tt/e8SzwFH
In recent times, archaeological teams have used some high-tech methods to probe the insides of the pyramids more rigorously. In the late 1960s, American Physicist Luis Alvarez and his team used muon tomography to scan the pyramid’s interior. In 1969, Alvarez reported that they examined 19% of the pyramid and found no new chambers.
In 2016-17, the ScanPyramids team used non-invasive techniques to study the Great Pyramid. Like Alvarez before them, they used muon tomography, along with infrared thermography and other tools. Their most significant discovery is the “Big Void,” a massive void above the Grand Gallery. The discovery was published in the journal Nature and is considered one of the most significant scientific discoveries that year.
Muons are elementary particles similar to electrons but more massive. They’re used in tomography because they penetrate deeply into structures. More deeply than even X-rays can.
Cosmic ray muons are created when high-energy particles known as cosmic rays slam into Earth’s atmosphere. Cosmic rays are fragments of atoms—high-energy protons and atomic nuclei— that constantly stream into Earth from the Sun, outside the Solar System, and outside the galaxy. When these particles collide with Earth’s atmosphere, the collision produces showers of secondary particles. Some of those particles are muons.
This diagram shows what happens when a primary cosmic particle collides with a molecule of atmosphere, creating an air shower. An air shower is a cascade of secondary decay particles, including muons, indicated with the symbol ?. Image Credit: By SyntaxError55 at the English Wikipedia, CC BY-SA 3.0, https://ift.tt/S350bkx
Muons are unstable and decay in only a couple of microseconds or millionths of a second. But they travel at near light speed, and at such a high velocity, they can penetrate deeply before they decay. There’s an unending source of muons from the cosmic rays that constantly bombard Earth. The task in muon tomography is to measure the muons effectively.
Muon tomography is used in different applications, like examining shipping containers for contraband. Recent technological innovations in muon tomography increase its power and lead to new applications. For example, scientists in Italy will use muon tomography to image the inside of the volcanic Mount Vesuvius, hoping to understand when it might erupt again.
The Explore the Great Pyramid (EGP) mission uses muon tomography to take the next step in imaging the Great Pyramid. Like ScanPyramids before them, EGP will use muon tomography to image the structure’s interior. But EGP says that their muon telescope system will be 100 times more powerful than previous muon imaging. “We plan to field a telescope system that has upwards of 100 times the sensitivity of the equipment that has recently been used at the Great Pyramid, will image muons from nearly all angles and will, for the first time, produce a true tomographic image of such a large structure,” they write in the paper explaining the mission.
EGP will use very large telescope sensors moved around to different positions outside the Great Pyramid. The detectors will be assembled in temperature-controlled shipping containers for ease of transportation. Each unit will be 12 m long, 2.4 m wide, and 2.9 m tall (40 ft long, 8 ft wide, and 9.5 ft tall.) Their simulations used two muon telescopes, and each telescope consists of four containers.
On the left is an illustration of the containers that make up the telescope. On the right is an illustration of how the telescope will be set up on-site. Image Credit: Explore Great Pyramid mission/Bross et al. 2022.
There are five critical points in the EGP mission:
Produce a detailed analysis of the entire internal structure which does not just differentiate between stone and air, but can measure variations in density.
Answer questions regarding construction techniques by being able to see relatively small structural discontinuities.
The large size of the telescope system yields not only the increased resolution, but enables fast collection of the data, which minimizes the required viewing time at the site. The EGP team anticipates a two-year viewing time.
The telescope is very modular in nature. This makes it very easy to reconfigure and deploy at another site for future studies.
From a technical perspective, the system being proposed uses technology that has been largely engineered and tested and presents a low risk approach.
EGP is still building telescope prototypes and determining which data-handling techniques they will use. Along the way, they’re doing simulations and other work to prepare for the mission. One critical piece is how they’ll corral all those muons into a tomographic image.
But the team is confident in the work they’ve done so far and satisfied with their new approach. EGP says their effort will create an actual tomographic image of the Great Pyramid for the first time, rather than a 2d image.
“The Exploring the Great Pyramid Mission takes a different approach to imaging large structures with cosmic-ray muons. The use of very large muon telescopes placed outside the structure, in our case, the Great Pyramid of Khufu on the Giza plateau, can produce much higher resolution images due to the large number of detected muons. In addition, by moving the telescopes around the base of the pyramid, true tomographic image reconstruction can be performed for the first time.”
Most of EGP’s work so far has been data simulations. But they won’t be starting from scratch when they build the telescope. “The detector technology employed in the telescopes is well established, and prototyping of specific components has already begun,” they write.
When ScanPyramids discovered the Big Void in 2017, it was big news. It caused some controversy, too. Egyptologist Zahi Hawass pooh-poohed the findings. He told the New York Times that “They found nothing…This paper offers nothing to Egyptology. Zero.”
But most other Egyptologists embraced the discovery and its scientific nature. Physicists were supportive of the discovery, too. Particle physicist Lee Thompson told Science that: “The scientists have “seen” the void using three different muon detectors in three independent experiments, which makes their finding very robust.”
There’s bound to be some drama when scientists use modern high-energy physics to probe one of humanity’s most ancient archaeological treasures. Some Egyptologists seem possessive and might view physicists as interlopers in their field. They might not like physicists using mysterious particles from outer space to open the veil on our ancient past.
The NASA Institute for Advanced Concepts (NIAC) has been a significant funder of pie in the sky research for a long time now. From extrasolar object interceptors to beaming power into a lunar crater, we love reporting about NIAC funded concepts here at UT. Now, a new crop of Phase I and a smaller but more focused crop of Phase II fellows are funded to push the boundaries of space exploration forward.
We’ve reported on some of the Phase I concepts that received $175,000 to work on refining their concept for the next nine months, including the Venus Atmosphere and Cloud Particle Sample Return for Astrobiology, submitted by Sara Seager of MIT. Other exciting concepts receiving first-round funding are a solid-state, electric vertical take-off and landing system, and a gigantic starshade that would allow Earth-based telescopes to search for signs of life in alien atmospheres.
Details of BREEZE – a NIAC funded project that would explore the atmosphere of Venus, among other places.
Credit – NASA
Phase II concepts, which have already completed a Phase I project, receive a total of $600,000 for two years of study. Only five were selected this year, ranging from a deployable 1km long artificial gravity structure to 3D printed swarm-bots. If nothing else, NIAC can always claim to be supporting incredible, cutting-edge technology. Maybe sometime, some of it will even become a reality.
Astronomers have a thing for big explosions and collisions, and it always seems like they are trying to one-up themselves in finding a bigger, brighter one. There’s a new entrant to that category – an event so big it created a burst of particles over 1 billion years ago that is still visible today and is 60 times bigger than the entire Milky Way.
That shockwave was created by the merger of two galaxy clusters to create a supercluster known as Abell 3667. This was one of the most energetic events in the universe since the Big Bang, according to calculations by Professor Francesco de Gasperin and his time from the University of Hamburg and INAF. When it happened over 200 million years ago, it shot out a wave of electrons, similar to how a particle accelerator would. All these years later, those particles are still traveling at Mach 2.5 (1500 km / s), and when they pass through magnetic fields, they emit radio waves.
Picture of galaxy cluster Abell 3667, where the white color in the center is a concatenation of 550 distinct galaxies, but the red structures represent the shockwaves formed during the creation of this supercluster.
Credit – Francesco de Gasperin, SARAO
Those radio waves are what Dr. de Gasperin and his colleagues observed using a new telescope array in South Africa known as MeerKAT. Radio signals alone weren’t enough to characterize the shockwave itself, though – the XMM-Newton X-ray observatory also spent some time focused on Abell 3667.
The results of all those observations is a better understanding of the physics of the merger of these galaxy clusters, which were “much more complex than we initially thought,” said Dr. de Gasperin. The shockwaves themselves look like “filaments that trace the location of giant magnetic field lines.” What is clear from the pictures is that, even when scientists are simply looking for big collisions, the resulting radio images might be awe-inspiring in themselves.
Venus is a difficult place to explore. Only a few missions have ever made it to the surface, in no small part because of how difficult it is to traverse the planet’s atmosphere. That difficulty was confirmed recently by a team led researchers at the University of Lisbon, who found that the upper part of Venus’ atmosphere suffers from hurricane-force winds of up to 360 kilometers per hour.
What’s even more impressive – that speed is 150 kilometers per hour more than the lower level atmosphere. Dr. Pedro Machado and his team posit that the difference in wind speed may be directly tied to the heat engine on Venus’ surface, which usually sits at a roasting 460 degrees Celsius.
How the researchers coordinated observations between the ground- and space-based observatories.
Credit – Pedro Machado, et al.
All that energy can contribute to wind speed, but the wind speed doesn’t get that high at lower altitudes and lower and higher latitudes. Differentiating these speeds was one of the unique parts of this study.
To do so, the researchers utilized data collected by two different instruments – the Telescopio Nazionale Galileo (TNG) and the Venus Express probe. The data was collected back in July 2012, when the TNG looked at the wind speeds of the lower decks of the atmosphere on the night side of Venus in infrared from Earth, while Venus Express took a look at the upper cloud deck on the daylight side as it was orbiting the planet.
Infrared images of Venus used in the research, including a partial image of the night side of the planet (right side of first image).
Credit – Pedro Machado et al.
This wasn’t the first time the wind speed of the lower cloud deck had been studied, and from previous observations and computer models, the researchers knew that the speed would be the same day or night. So, combining that knowledge with the direct measurements from TNG and Venus Express, they found the vast difference in wind speeds at different altitudes.
Those differences will play into the design of the next generation of Venus explorers, which we’ve reported on several times. Of particular interest to the team is EnVision, which will contain an infrared spectrograph tuned to specific wavelengths based on the atmospheric conditions being studied now.
UT video discussing the surface of Venus.
Before EnVision launches, though, there are still more opportunities to learn about Venus’ atmosphere. This would include a collaboration between an Earth-based telescope and Akatsuki, a JAXA probe currently orbiting Venus. Updated information could not only provide more insight into whatever difficulty a future Venus lander might face but also help inform the design decisions of the craft that will stay well out of the way of any atmospheric hurricanes.
Both quantum computing and machine learning have been touted as the next big computer revolution for a fair while now. However, experts have pointed out that these techniques aren’t generalized tools – they will only be the great leap forward in computer power for very specialized algorithms, and even more rarely will they be able to work on the same problem. One such example of where they might work together is modeling the answer to one of the thorniest problems in physics: how does General Relativity relate to the Standard Model?
A team led by researchers at the University of Michigan and RIKEN think they might have developed just such an algorithm. There aren’t many places where the two great physics models collide, but around a black hole is one of them. Black holes themselves are massive gravity wells ruled entirely by the physics defined by General Relativity. However, innumerable particles are swirling around their event horizons that are effectively immune to gravity but do fall under the Standard Model structure, which deals directly with the physics of particles.
There has been a long-standing theory that the motions and accelerations of the particles directly above a black hole might be a two-dimension projection of what the black hole itself is doing in three dimensions. This concept is called holographic duality and might offer a way to look for that critical interface between relativity (i.e., black hole physics) and the Standard model (i.e., particle physics).
UT video discussing the Holographic Principle
Holographic duality itself is challenging to model with modern-day computing algorithms, though. So Enrico Rinaldi, a physicist at the University of Michigan and RIKEN, attempted to develop a new model that utilized those two very hyped computing architectures – quantum computing and machine learning.
Quantum computing itself can be helpful in modeling particle physics, as some of the physics underlying the computing platform itself are subject to those physical laws that are so foreign to us at a macro scale. In this case, Dr. Rinaldi and his team used an algorithm running on a quantum computer to simulate the particles that make up the project part of the holographic duality.
To do so, they utilized a concept called a quantum matrix model. As with many physics simulations, the end goal of the simulation was to find the lowest energy state of the system. Quantum matrix models would help effectively solve the optimization problems that would find the lowest energy state of the particle systems projected above a black hole.
PBS Space Time video explaining how we might just live in a hologram.
Credit – PBS Space Time YouTube
Algorithms utilizing a quantum computer aren’t the only way to find those “ground states,” as the lowest energy state of the system is called. Another method would be to utilize a type of AI technique called a neural network. These are based around using systems similar to those found in human brains.
The team applied these algorithms to a type of matrix model still based on quantum ideas but not requiring quantum computing. Known as a quantum wave function, these again represented the activity of the particles on the surface of the black hole. And once again, the neural network algorithm was able to solve the optimization problem and find its “ground state.”
According to Rinaldi, these new techniques represent a significant improvement upon other previous efforts at solving these algorithms. “Other methods people typically use can find the energy of the ground state, but not the entire structure of the wave function,” Rinaldi said in a press release.
Artist view of an active supermassive black hole.
Credit: ESO/L. Calçada
What this means for understanding the inside of a black hole, or the interface between the standard model and general relativity, is still a bit of a black box. Theoretically, there should be a way to model the inside of a black hole using the types of quantum wave functions defined by these algorithms. But that work, which could lead to an underlying quantum theory of gravity according to Rinaldi, remains to be done. As these hyped computing architectures continue to gain in popularity, though, it’s almost a certainty that someone will attempt to shine some light on that black box.
Between the exponential growth of the commercial space industry (aka. NewSpace) and missions planned for the Moon in this decade, it’s generally agreed that we are living in the “Space Age 2.0.” Even more ambitious are the proposals to send crewed missions to Mars in the next decade, which would see astronauts traveling beyond the Earth-Moon system for the first time. The challenge this represents has inspired many innovative new ideas for spacecraft, life-support systems, and propulsion.
In particular, missions planners and engineers are investigating Directed Energy (DE) propulsion, where laser arrays are used to accelerate light sails to relativistic speeds (a fraction of the speed of light). In a recent study, a team from UCLA explained how a fleet of tiny probes with light sails could be used to explore the Solar System. These probes would rely on a low-power laser array, thereby being more cost-effective than similar concepts but would be much faster than conventional rockets.
The study was conducted by Ho-Ting Tung, an aerospace engineering grad student from UCLA, and assistant professor Artur R. Davoyan, both of whom are members of the Davoyan Research Group (DRG), of which Prof. Davoyan is the founder. This group is dedicated to the study of directed energy and light-material interactions for the purpose of developing “space photonics.” The paper that describes their findings recently appeared in the journal Nano Letters, an publication overseen by the American Chemistry Society (ACS).
For decades, scientists have investigated light sails as a possible means of space exploration. These spacecraft offer many advantages over conventional concepts, foremost of which is how they forego the need for propellant. For most designs, propellant constitutes a big chunk of a spacecraft’s mass, which necessitates large storage tanks, resulting in additional mass, and so on. Where interstellar space travel is concerned, it becomes a terrible burden.
Using conventional propulsion, getting to even the nearest star system – Proxima Centauri, located about 4.25 light-years away – could take several thousand years. For this reason, multiple organizations are exploring light sail mission concepts as a means of interstellar travel. This includes Breakthrough Starshot, Project Dragonfly, and Project Lyra, which involve using large arrays up to 100 GigaWatts (GW) in power to propel spacecraft to relativistic speeds and achieve interstellar travel.
But as Prof. Davoyan told Universe Today via email, these approaches have applications for exploring the Solar System as well:
“Getting to other star systems is very hard due to astronomical distances. For example, the closest system is about 4 light years away from us. Reaching it with any conventional way of propulsion would require thousands of years.There are several different approaches that are considered to accelerate spaceflight: mainly fusion propulsion and directed energy, such as with the use of lasers.
“At the same time, even getting to the outer reaches of our solar system, such as to outer planets, the Kuiper belt, and entering the interstellar medium is very very challenging. It takes years of flight time and mission development. We discuss a new way of using beamed laser propulsion to send probes to outer planets.”
Artist’s impression of the Dragonfly spacecraft concept. Credit and Copyright: David A Hardy (2015)
For the sake of their study, Ho-Ting and Davoyan considered various spacecraft profiles with varying degrees of size and laser wattage. These included an array ranging from 100 kiloWatts (kW) to 1 megaWatt (MW), which is low-power compared to interstellar concepts. Like Starshot and Dragonfly, they calculated for gram-scale probes ranging from 10 to 100 grams in mass. From this, they envisioned a wafer probe about 45 cm (18 inches) in diameter with integrated electronics on one side and a nanoscale structure on the other.
Beyond directed energy, this concept incorporates another of the Davoyan Research Group’s areas of expertise. This is the field known as nanophotonics, the science of how materials that are a few nanometers in scale interact with light, with applications ranging from broadband communications and photovoltaics to spacecraft propulsion. In the end, they found that 100 kW arrays and sails of silicon or boron nitride would allow for cost-effective and rapid interplanetary missions. Said Davoyan:
“We show that our approach can be much faster than any other conventional propulsion system, such as electric and chemical propulsion. Voyager 1 is the fastest interplanetary spacecraft that was ever built. Traveling at about 17 km/s of cruise velocity it took ~45 years to reach 100 AU. Our system can be 4 times faster than that. Some conceptual approaches with nuclear propulsion with several gravity assists can be similarly fast.
“However, the probes we discuss are low cost and are not constrained by development time or launch window, which makes them more agile. In general, very low cost and the ability to leverage mass manufacturing allow a new way of space exploration, in which everyone can get easy access to deep space missions. We believe this will be transformative to space science.”
In this illustration, NASA’s Hubble Space Telescope is looking along the paths of NASA’s Voyager 1 and 2 spacecraft as they journey through the Solar System and into interstellar space. Credit: NASA, ESA, and Z. Levy (STScI).
The ability to conduct low-cost, rapid-deployment missions presents many advantages. The New Horizons mission holds the record for the fastest object ever launched from Earth, with an escape trajectory of about 16.26 km/s (58,500 km/h; 36,400 mph). Nevertheless, it took the probe nine and a half years to reach Pluto and capture the most detailed images ever taken of its surface. The same is true of the Voyager 1 and 2 missions, which launched from Earth in 1977 and reached the edge of the Solar System in 2004 and 2007, respectively.
While the scientific returns from all of these missions were immeasurable, a low-cost option that could reach their destinations in a fraction of the time would yield these types of returns on a much more regular basis. There will be no shortage of opportunities with missions planned for Europa, Titan, Triton, and the Kuiper Belt in the coming years. In addition to making such missions faster and cheaper, light sail probes could also allow for more missions for the same cost. As Davoyan summarized:
“We believe that our approach could allow a new way for space missions, when the time it takes from an idea to getting science data back would take less than a year. This is not possible today. We foresee that many probes can be sent to different destinations, including Mars to collect science data and therefore accelerate discoveries.
“Today we have to choose between going to Enceladus, Europa or Titan. And then it takes decades and billions to develop a flagship mission. With probes that cost less than $1000 and can be developed in less than a month the space exploration can be changed dramatically.”
Right now, light sail proposals are being considered for rendezvousing with ‘Oumuamua, exploring the Solar System, and mounting interstellar missions to Alpha Centauri in a matter of decades instead of centuries. Variations on the concept, such as directed energy thermal propulsion, are even being considered for sending crewed missions to Mars in a matter of weeks instead of months. With no chemical propellants weighing them down, these missions could be developed at a fraction of the cost.
Over time, the creation of laser arrays throughout the Solar System could lead to a transportation infrastructure that spans the Solar System. Who knows? Combined with next-generation spacecraft that rely on various types of nuclear propulsion, this vision could lead to humans becoming “interplanetary” in terms of their habitation but interstellar in terms of their exploration.
Every journey begins with a single step, and the first step of NASA’s return to the Moon begins with a four-mile rollout to the launchpad. NASA announced their target date for rolling out the Space Launch System rocket for the four-mile crawl to the launch pad for March 17. The full rocket stack will spend about a month at the pad undergoing several tests before heading back to the Vehicle Assembly Building. If all goes well with the tests, NASA hopes to launch its uncrewed Artemis test flight, likely by early summer.
Mike Bolger, the Exploration Ground Systems program manager at Kennedy Space Center, said the rollout will begin at 6 pm Eastern Time. It will take about an hour for the vehicle and its mobile launch tower to move out of the VAB on a giant crawler-transporter vehicle, then 11-hour trip to the pad.
“The crawler transporter will use a range of speeds,” Bolger said in a call with reporters, “from .1 mph to .82 mph. The slower speeds are for departing the VAB and the ‘higher’ speed is the cruising speed, so to speak.”
The stack of the Space Launch System rocket in the Vehicle Assembly Building at Kennedy Space Center. ESA has built the service module for the Orion crew capsule. Credit and copyright: Alan Walters, for Universe Today.
The last time a vehicle capable of carrying a crew rolled out from the VAB was in 2011 for the final flight of the Space Shuttle program. Bolger said that while space shuttle rollouts usually began at midnight, they wanted to start this rollout earlier so that everyone could be part of it, including KSC workers and their families as well as the media.
“The crawler transporter will be carrying this 17 million pound stack,” Bolger said, “and top of the umbilical will be about 400 feet off the ground, so it will really be a sight.”
Graphic via ESA.
The main goal of the test on the launchpad will be the “wet dress” rehearsal, which includes filling the core stage fuel tanks with liquid hydrogen and liquid oxygen propellants and then going through a practice countdown that will stop at T-9.34 seconds, just before the core stage’s four RS-25 engines would ignite during an actual launch.
As far as the timeframe for the launch of the test flight, Tom Whitmeyer, NASA’s deputy associate administrator for exploration systems development, said the agency is waiting to see how the wet dress rehearsal goes, and they will set the date after that.
The stack of the Space Launch System rocket in the Vehicle Assembly Building at Kennedy Space Center. Credit and copyright: Alan Walters, for Universe Today.
“It is a complicated test,” he said, “and we will continue to evaluate the May window but also recognize there is a lot of work ahead of us and we need to get through that before we set the date.”
The May launch window runs from May 7 to 21. While future launch windows are June 6 to 16, and June 29 to July 12, with a “cutout” of July 2 to 4 when a launch would not be possible. The launch windows take into account being able to splashdown during daylight hours and the best hours for the tests they want to accomplish.
Asked about any potential complications due to Russia’s invasion of Ukraine and how that may affect operations on the International Space Station Whitmeyer said he could not comment on ISS operations, but he did not know of any components of the SLS or Orion capsule that come from Russia or Ukraine. He added that a lot of the vehicle’s hardware has shuttle-derived heritage, and the only non-US major component is the Orion service module, which was built by the European Space Agnecy. Ten European countries involved in the development of the European Service Module, with input from 26 European companies
Lead image caption: The stack of the Space Launch System rocket in the Vehicle Assembly Building at Kennedy Space Center. Credit and copyright: Alan Walters, for Universe Today.
The Curiosity rover took a picture of something pretty enticing this week on the surface of Mars. While the object in question looks like a tiny little flower or maybe even some type of organic feature, the rover team confirmed this object is a mineral formation, with delicate structures that formed by mineral precipitating from water.
Curiosity has actually seen these types of features before, which are called diagenetic crystal clusters. Diagenetic means the recombination or rearrangement of minerals, and these features consist of three-dimensional crystal clusters, likely made of a combination of minerals. Curiosity deputy project scientist Abigail Fraeman said on Twitter that these features that were seen previously were made of salts called sulfates.
(1/3) Your Friday moment of zen: A beautiful new microscopic image from @MarsCuriosity shows teeny, tiny delicate structures that formed by mineral precipitating from water.
From studies of previous features like this found on Mars (you can read a paper on them here), originally the feature was embedded within a rock, which eroded away over time. These mineral clusters, however, appear to be resistant to erosion.
Another name for these features is concretion, which you may remember from the Opportunity rover, who saw features that were nicknamed ‘blueberries,’ since they were small and round. You can see round concretions next to the flower-like feature in this image.
The rover science team saw this feature earlier this week and named it ‘Blackthorn Salt’. They used the rover’s Mars Hand Lens Imager, called MAHLI, to take these close-up images. This camera is the rover’s version of the magnifying hand lens that geologists usually carry with them into the field. MAHLI’s close-up images reveal the minerals and textures in rock surfaces.
Curiosity rover obtained this ‘Hand Lens’ extreme close-up of one of the very small and rather unusual concretion features. This one has been called ‘Blackthorn Salt’. Credit: NASA/JPL-Caltech/MSSS/Kevin M. Gill
Here you can see a 3-D model of the object, thanks to Simeon Schmauss:
@MarsCuriosity imaged a funky looking mineral formation the other day. This is a 3D model created from 6 images taken by the MAHLI instrument.
Credit: NASA/JPL-Caltech/MSSS
Curiosity found another flower-like feature back in 2013, and the Spirit rover found similar-looking rocks that were nicknamed ‘cauliflower’ features because of their knobby protuberances.
“Cauliflower” shaped silica-rich rocks photographed by the Spirit Rover near the Home Plate rock formation in Gusev Crater in 2008. Credit: NASA/JPL-Caltech
Remember that iconic scene in Star Wars, where a young Skywalker steps out onto the surface of Tatooine and watches the setting of two suns? As it turns out, this may be what it is like for lifeforms on the exoplanet known as Kepler-16, a rocky planet that orbits in a binary star system. Originally discovered by NASA’s Kepler mission, an international team of astronomers recently confirmed that this planet orbits two stars at once – what is known as a circumbinary planet.
The international team, led by Professor Amaury Triaud of the University of Birmingham, comprises members of the BEBOP collaboration. This observation campaign began in 2013 and relied on telescopes from around the world to conduct radial velocity surveys for circumbinary planets. The team’s research is published in Monthly Notices of the Royal Astronomical Society.
The planet, known as Kepler-16b, is located approximately 245 light-years from Earth and orbits its binary stars with a period of 228.8 days. Like Tatooine, life forms on this planet would look up into the sky and see two suns rising and setting. However, the planet orbits outside its two stars’ “habitable zone,” meaning that conditions on the surface are likely very cold. It was discovered in 2011 by Kepler using the Transit Method (aka. Transit Photometry).
An illustration of the Kepler-47 circumbinary planet system. Credit: NASA/JPL Caltech/T. Pyle
For this method, astronomers observe stars for periodic dips in brightness that indicate the presence of orbiting planets. Astronomers also rely on this method because it effectively establishes constraints on an exoplanet’s size. For the sake of their study, the team relied on the SOPHIE echelle spectrograph on the 193-cm telescope at the Observatoire de Haute-Provence to perform Radial Velocity (aka. Doppler Spectroscopy) measurements on the system.
This method consists of observing stars for signs of “wobble,” which indicates that gravitational forces are acting on them (caused by one or more planets). As co-author Dr. Alexandre Santerne (a researcher from Aix-Marseille University) explained in a Royal Astronomical Society press release:
“Kepler-16b was first discovered 10 years ago by NASA’s Kepler satellite using the transit method. This system was the most unexpected discovery made by Kepler. We chose to turn our telescope to Kepler-16 to demonstrate the validity of our radial-velocity methods.”
Their measurements confirmed that Kepler-16b orbits both stars (which orbit each other), a finding that may help resolve an open question about binary star systems. According to the most widely-accepted model of planet formation, planets are believed to form within a disk of dust and gas surrounding young stars – aka. a protoplanetary disk. This presents some difficulties where binary systems are concerned, as the model predicts that the gravitational forces might interfere with planet formation.
TOI 1338 b is a circumbinary planet orbiting its two stars. Credit: NASA’s GSFC/Chris Smith
In recent years, the discovery and statistical significance of “Hot Jupiters” have also raised questions for astronomers. According to the protoplanetary disk model, gas giants cannot form this close to their stars due to insufficient mass and excessive heat. The only possible explanation, according to astronomers, is that planets (while they are still in the process of formation) migrate within the disk as a result of gravitational interactions with other bodies.
These findings indicate that disc-driven migration is a viable process and a relatively common occurrence. Said Prof. Triaud:
“Using this standard explanation it is difficult to understand how circumbinary planets can exist. That’s because the presence of two stars interferes with the protoplanetary disc, and this prevents dust from agglomerating into planets, a process called accretion.
“The planet may have formed far from the two stars, where their influence is weaker, and then moved inwards in a process called disc-driven migration – or, alternatively, we may find we need to revise our understanding of the process of planetary accretion.”
Artist’s impression of a hypothetical planet orbiting the star Alpha Centauri B, a member of the triple star system neighboring the Solar System. Credit: ESO
The detection of Kepler-16b using a ground-based telescope and the Radial Velocity Method was also significant. Essentially, it demonstrated that it is possible to detect circumbinary planets using more traditional methods with greater efficiency and lower costs than space-based observatories. With this success under their belts, the team plans to continue searching for previously unknown circumbinary planets and help answer questions about planetary formation.
As co-author Dr. Isabelle Boisse, the scientist in charge of the SOPHIE instrument at Aix-Marseille University, summarized:
“Our discovery shows how ground-based telescopes remain entirely relevant to modern exoplanet research and can be used for exciting new projects. Having shown we can detect Kepler-16b. We will now analyze data taken on many other binary star systems and search for new circumbinary planets.”
It’s coming together! Engineers for the James Webb Space Telescope have now completed two more phases of the seven-step, three-month-long mirror alignment process. This week, the team made more adjustments to the mirror segments along with updating the alignment of its secondary mirror. These refinements allowed for all 18 mirror segments to work together — for the first time — to produce one unified image.
As you can see in the image above, this view of the star HD 84406 shows one image instead of the 18 views – one from each segment – that we saw earlier this week. NASA engineers say that after future alignment steps, the image will be even sharper.
“We still have work to do, but we are increasingly pleased with the results we’re seeing,” said Lee Feinberg, optical telescope element manager for Webb, in a blog post. “Years of planning and testing are paying dividends, and the team could not be more excited to see what the next few weeks and months bring.”
The star that engineers and scientists are using to focus the telescope is a G-type main-sequence star that is a lot like our own Sun, located near the ‘bowl’ of the Big Dipper (Ursa Major). JWST’s Near Infrared Camera (NIRCam) instrument took the images of this star, which are being used to align the mirrors and calibrate the telescope.
The two steps that were taken this week are called Segment Alignment and Image Stacking. Segment Alignment corrects most of the large positioning errors for the segments. A process called Phase Retrieval uses mathematical analysis to determine the precise positioning errors of the segments. At this phase, the segments still don’t work together as a single mirror.
Before and after Segment alignment. Credit: NASA/STScI
This animated gif shows the “before” and “after” images from Segment Alignment, when the team corrected large positioning errors of its primary mirror segments and updated the alignment of the secondary mirror.
In Image Stacking, the images from each segment image are stacked on top of one another. Then the individual segment images are moved so that they fall precisely at the center of the field of view to produce one unified image. This puts all the light in one place on the detector.
“We still have to ensure the light arrives at the detector in perfect unison, which will make the resolution 5 times better than what you see here,” said JWST project scientist Klaus Pontoppidan on Twitter.
Next, the team will now begin making even smaller adjustments to the positions of Webb’s mirrors.
Although Image Stacking put all the light from a star in one place on NIRCam’s detector, the mirror segments are still acting as 18 small telescopes rather than one big one. The segments now need to be lined up to each other with an accuracy smaller than the wavelength of the light.
JWST primary mirror size compared to the Hubble Space Telescope. Credit: NASA
The team is now working on that, beginning the fourth phase of mirror alignment, called Coarse Phasing, where NIRCam is used to capture light spectra from 20 separate pairings of mirror segments. This helps the team identify and correct vertical displacement between the mirror segments, or small differences in their heights. This will make the single dot of starlight progressively sharper and more focused in the coming weeks.
But from here on, the process will be iterative, where once a certain level of alignment and focus is achieved, the engineers may have to go back and re-do certain steps to achieve perfect alignment.
“You align the mirrors, then check them, and then you need to go back a few steps and adjust and recenter, and then go back through the entire process again,” Feinberg told me last month, “which is why the process will take approximately three months.”
Team members continue to share their experiences and provide more info on the alignment process at the JWST blog.
Can one type of planet become another? Can a mini-Neptune lose its atmosphere and become a super-Earth? Astronomers have found two examples of mini-Neptunes transitioning to super-Earths, and the discovery might help explain a noted “gap” in the size distribution of exoplanets.
It’s only natural that we classify exoplanets in ways related to our Solar System’s planets. We use the terms Hot Jupiters, mini-Neptunes, and Super-Earths because they help us quickly recognize what astronomers are talking about. Why do astronomers find so many of these planets in other solar systems rather than planets similar to our Solar System?
That question highlights what’s called the “size gap” in exoplanets.
Two new studies examine a pair of mini-Neptunes that are losing their atmospheres. The discovery not only provides examples of a phenomenon that scientists have theorized about, but it might also help explain the gap in the sizes of exoplanets we find.
The researchers used the Hubble Space Telescope and the W.M. Keck Observatory to study the planets. They found that both of these mini-Neptunes are undergoing similar transformations. Radiation from their stars strips away their atmospheres and drives the gases into space. The observations suggest that the planets are slowly transitioning into super-Earths.
Mini-Neptunes are planets like Neptune but less massive. Like Neptune, they have thick atmospheres of hydrogen and helium. There are probably deeper layers of ice, rock, maybe even liquid oceans. They have rocky cores and are between 1.7 and 3.9 Earth radii. Mini-Neptunes are also called gas dwarfs.
Mini Neptunian planets range in size from about 1.5 to 4 times the size of Earth and have a rocky core and puffy gaseous shell of varying thickness. Credit: Geoff Marcy
Super-Earths are terrestrial planets larger than Earth but smaller than our Solar System’s ice giants, Uranus and Neptune. Super-Earths have radii as large as 1.6 times Earth’s radius. The term “super-Earth” does not indicate a planet’s potential habitability, only of its size.
This illustration compares Earth and Neptune to the super-Earth CoRoT-7b (center.) Image Credit: By Aldaron, a.k.a. Aldaron – Own work, incorporating public domain images for reference planets (see below), inspired by Thingg’s size comparison, CC BY-SA 3.0, https://ift.tt/VBTljLb
One way of looking at these names is that mini-Neptunes are just planets on the upper end of the size scale for super-Earths.
Both these terms became common as we found more and more exoplanets. Sometimes they’re used interchangeably, depending on the context. NASA’s exoplanet catalogue contains 4933 confirmed exoplanet discoveries, and 1723 of them are “Neptune-like,” while 1538 are “super-Earth’s.”
This is a screenshot from NASA’s exoplanet catalogue from February 23rd, 2022. This chart tracks the current number of known planet discoveries beyond our solar system, sorted by type. Image Credit: NASA.
The new papers present examples of mini-Neptunes losing their atmospheres and sliding down the size scale to potentially become super-Earths. Astronomers predicted this phenomenon long ago, but observing it in action was challenging.
“Most astronomers suspected that young, mini-Neptunes must have evaporating atmospheres,” said Michael Zhang, lead author of both studies and a graduate student at Caltech. “But nobody had ever caught one in the process of doing so until now,” he said in a press release.
One of the mini-Neptunes is HD 63433c. It orbits a star about 73 light-years away and 2.67 times Earth’s radius. It’s on an 18.8-day orbit around a star similar to our Sun, but much younger at about 440 million years old. According to the paper, HD 53433c has already lost most of its primordial atmosphere.
The second mini-Neptune undergoing mass-loss is TOI 560.01 (also known as HD 73583b.) Its radius is 2.8 Earth radii. It also orbits a young star, in this case, a 600 million-year-old K-dwarf. Its orbital period is 6.4 days.
This is an artist’s conception of a mini-Neptune or “gas dwarf.” These two new studies present observational evidence that mini-Neptune’s lose portions of their atmosphere due to photoevaporation and transition to super-Earths. Image Credit: By Pablo Carlos Budassi – Own work, CC BY-SA 4.0, https://ift.tt/lnN219e
There’s an evident size gap in the range of exoplanets discovered so far. Most exoplanets are in the super-Earth to the mini-Neptune range, but the range is not populated evenly. Super-Earths can be as large as 1.6 times Earth’s size. Mini-Neptunes are between 2 and 4 times the size of Earth. Astronomers have discovered very few exoplanets with sizes between 1.6 and 2 Earth radii. The few that have been found mean it’s more of a size “valley” than a “gap.” It’s also called the small planet radius gap, the Fulton gap, the photoevaporation valley, or the Sub-Neptune Desert. But whatever we want to call it, it’s there.
Why?
This figure is a histogram of planets with given radii from a sample of 900 Kepler systems. The decreased occurrence rate between 1.5 and 2.0 Earth radii is apparent. Image Credit: Fulton et al. 2017
Exoplanet scientists call the low number of planets between about 1.5 and 2 times Earth’s radius the photoevaporation valley because photoevaporation is behind it. Evidence for the photoevaporation goes back years, and many papers have covered it, though these two new papers are the first to present direct observational evidence supporting it.
Both mass-losing mini-Neptunes are in young solar systems, which helps explain the photoevaporation valley. Theory shows that these planets are shrouded in an atmosphere of hydrogen and helium left over after their star formed. Our own Neptune is far from the Sun, but if a smaller mini-Neptune was closer to its star, then the star could strip away the hydrogen and helium. The atmospheric stripping wouldn’t take long, and these studies show it happening in young solar systems. The photoevaporation can leave behind the mini-Neptune’s rocky core, now a super-Earth. The super-Earth could retain some of its atmosphere depending on the characteristics of the star, the planet, and their separation. The fact that it happens in only hundreds of millions of years would explain the observed photoevaporation valley.
“A planet in the size gap would have enough atmosphere to puff up its radius, making it intercept more stellar radiation and thereby enabling fast mass loss,” said Zhang. “But the atmosphere is thin enough that it gets lost quickly. This is why a planet wouldn’t stay in the gap for long.”
In this artist’s illustration, the small planet transiting close to its star is Kepler-19b. Kepler-19b is a mini-Neptune orbiting a star about 700 light-years away. Kepler 19b has lost much of its atmosphere but is massive enough that it’s retained about 50% of its original atmosphere. Other mini-Neptunes aren’t so massive and can lose much greater percentages of their atmospheres. The larger planet in the foreground is Kepler-19c. Credit: David A. Aguilar (CfA)
Studying the photoevaporative removal of a planet’s atmosphere in a solar system tens of light-years away or more takes away some of the impact. The forces involved in stripping away an atmosphere are epic. “The speed of the gases provides the evidence that the atmospheres are escaping. The observed helium around TOI 560.01 is moving as fast as 20 kilometres per second,” Zhang said. 20 km/s is equal to 72,000 kilometres per hour. For comparison, the International Space Station travels at 28,000 km/h.
Zhang also said the hydrogen escaping from HD 63433c moves at speeds up to 50 kilometres per second. That’s 180,000 kilometres per hour.
“The gravity of these mini-Neptunes is not strong enough to hold on to such fast-moving gas,” Zhang said.
It’s not only the measured speed of the helium and hydrogen around these planets that indicate an escaping atmosphere; it’s the size of their atmospheric envelopes.
“The extent of the outflows around the planets also indicates escaping atmospheres; the cocoon of gas around TOI 560.01 is at least 3.5 times as large as the radius of the planet, and the cocoon around HD 63433c is at least 12 times the radius of the planet.”
If this were happening in our Solar System, what would it look like? The Sun’s stellar wind has battered the Earth for billions of years. We’re only here because Earth’s magnetosphere deflects enough of the Sun’s radiation to hold onto the atmosphere and protect it from photoevaporation. It’s not the same because Earth’s atmosphere is not remnant hydrogen and helium from the solar nebula. So Earth never had a massive gaseous envelope as mini-Neptunes do.
The two mini-Neptunes in the papers have orbital periods of only 18.8 days and 6.4 days. They’re very close to their stars, which makes them great observational targets. What would it be like if our Solar System was home to one of these mini-Neptunes losing its atmosphere?
Imagine a planet with a radius several times larger than Earth, closer to the Sun than Mercury is. It would transit in front of the Sun every week or month. It would be one of the brightest objects in the sky, and periodically the Earth-Moon system might travel through the stream of hydrogen/helium escaping from its atmosphere. It would be something to behold and would’ve shaped all of humanity’s early myths. A massive planet in that location could’ve completely reshaped the inner Solar System’s history.
Some scientists refer to these mass-losing exoplanets as “gas-rich adolescents.” But if they’re adolescents, they’re not the type of adolescents that can become more like Earth. Earth’s atmosphere has a high molecular weight. Like a mini-Neptune, its atmosphere isn’t remnant hydrogen and helium from the solar nebula. Earth’s atmosphere likely has a combination of causes: volcanic out-gassing, loss of lighter atmospheric components to space, even plate tectonics, and magma ocean crystallization on the very young Earth. So finding mini-Neptunes in distant solar systems doesn’t tell us much about how many Earth-like planets might be out there.
This study brings observational evidence to support a long-standing theory. But it also holds a surprise.
The gas escaping from TOI 560.01 moves toward its star rather than away. Is that an anomaly? Exoplanet scientists aren’t sure what might constitute “normal” in many parts of their field. They’ve discovered many oddball planets that don’t look like anything in our Solar System. As far as gas flowing from a mini-Neptune’s atmosphere towards its star, only observations of more transitioning planets can explain if that’s an anomaly or not.
This artist’s image shows Roche-lobe overflow between a mini-Neptune and its star. Image Credit: NASA/GSFC/Frank Reddy
“This was unexpected, as most models predict that the gas should flow away from the star,” said professor of planetary science Heather Knutson of Caltech, Zhang’s advisor and a co-author of the study. “We still have a lot to learn about how these outflows work in practice.”
“As exoplanet scientists, we’ve learned to expect the unexpected,” Knutson said. “These exotic worlds are constantly surprising us with new physics that goes beyond what we observe in our solar system.”
