The ionosphere is a layer of weakly ionized plasma bathed in Earth’s geomagnetic field extending about 50–1,500 kilometres above Earth1. The ionospheric total electron content varies in response to Earth’s space environment, interfering with Global Satellite Navigation System (GNSS) signals, resulting in one of the largest sources of error for position, navigation and timing services2. Networks of high-quality ground-based GNSS stations provide maps of ionospheric total electron content to correct these errors, but large spatiotemporal gaps in data from these stations mean that these maps may contain errors3. Here we demonstrate that a distributed network of noisy sensors—in the form of millions of Android phones—can fill in many of these gaps and double the measurement coverage, providing an accurate picture of the ionosphere in areas of the world underserved by conventional infrastructure. Using smartphone measurements, we resolve features such as plasma bubbles over India and South America, solar-storm-enhanced density over North America and a mid-latitude ionospheric trough over Europe. We also show that the resulting ionosphere maps can improve location accuracy, which is our primary aim. This work demonstrates the potential of using a large distributed network of smartphones as a powerful scientific instrument for monitoring Earth.
[…]
Although measurements from individual mobile phones are noisier than those from conventional monitoring stations, we have shown that millions of phones in concert yield valuable measurements of ionospheric TEC. Other recent work has shown that phone accelerometers can detect earthquakes to provide early warning33 and that phone barometers can improve weather forecasting34. Building on these examples, our work continues to illuminate the potential for mobile phone sensors as a powerful tool to improve the scientific understanding of our planet.
The world’s first wood-panelled satellite has been launched into space to test the suitability of timber as a renewable building material in future exploration of destinations like the Moon and Mars.
Made by researchers in Japan, the tiny satellite weighing just 900g is heading for the International Space Station […]. It will then be released into orbit above the Earth.
Named LignoSat, after the Latin word for wood, its panels have been built from a type of magnolia tree, using a traditional technique without screws or glue.
Researchers at Kyoto University who developed it hope it may be possible in the future to replace some metals used in space exploration with wood.
“Wood is more durable in space than on Earth because there’s no water or oxygen that would rot or inflame it,” Kyoto University forest science professor Koji Murata told Reuters news agency.
[…]
Dr Barber said it wasn’t the first time that wood had been used on spacecraft.
“We use wood – cork – on the re-entry, outer shell of vessels of spacecraft to help them survive re-entry into Earth’s atmosphere.”
Russian and Soviet lunar landers used cork to help the rover have grip as it was descending to the surface, he added.
“There’s nothing wrong with using wood in space – it’s using the right material for the right task.”
He pointed out that wood has properties that are hard to control.
“So from an engineering point of view it’s quite a difficult material to work with… I think wood’s always going to have a problem to make critical structures like parts of spacecraft where you need to predict how strong it’s going to be.”
The researchers at Kyoto University hope using wood in making spacecraft could also be much less polluting than metal ones when they burn-up on re-entry at the end of their life.
The dawn of annoyingly massive satellites is upon us, shielding our views of the shimmering cosmos. Five of the largest communication satellites just unfolded in Earth orbit, and this is only the beginning of a Texas startup’s constellation of cellphone towers in space.
AST SpaceMobile announced today that its first five satellites, BlueBirds 1 to 5, unfolded to their full size in space. Each satellite unfurled the largest ever commercial communications array to be deployed in low Earth orbit, stretching across 693 square feet (64 square meters) when unfolded. That’s bad news for astronomers as the massive arrays outshine most objects in the night sky, obstructing observations of the universe around us.
Things are just getting started for AST SpaceMobile, however, as the company seeks to create the first space-based cellular broadband network directly accessible by cell phones. “The deployment of our first five BlueBird commercial satellites marks just the beginning of our journey,” Abel Avellan, founder and CEO of AST SpaceMobile, said in a statement. “Our team is already hard at work building the next generation of satellites, which will offer ten times the capacity of our current BlueBirds, further transforming mobile connectivity and delivering even greater benefits to our customers and partners worldwide.”
[…]
Unfortunately, now there’s five more of them. AST SpaceMobile launched its five BlueBird satellites on September 12, seeking to build a constellation of more than 100 satellites in low Earth orbit to provide nationwide coverage across the U.S.
The latest constellation is an indication of an increasingly worrying problem that’s suffocating Earth orbit, with the number of large satellites increasing five times over the past 12 years, according to a letter sent by a group of space experts to the Federal Communications Commission (FCC).
“Experts from top universities are warning we’re in a short window of time when we can prevent making a mess of space and our atmosphere rather than spend decades cleaning it up,” Lucas Gutterman, director of the U.S. PIRG Education Fund’s Designed to Last Campaign, said in the letter. “The new space race doesn’t need to create massive space waste.”
The letter calls on the FCC to follow the recommendations of the U.S. Government Accountability Office and stop excluding satellites from environmental reviews. AST SpaceMobile isn’t the only company trying to build cellular towers in space. SpaceX is building its own constellation of satellites, with more than 6,000 Starlink satellites currently in low Earth orbit. Amazon, OneWeb, and Lynk Global are other companies trying to get in on the action.
Those satellites, however, have a major impact that can’t be ignored. “Artificial satellites, even those invisible to the naked eye, can obstruct astronomical observations that help detect asteroids and understand our place in the universe,” Robert McMillan, an astronomy professor and founder of the Spacewatch Project at the University of Arizona, said in the letter.
Orbital mechanics is a fun subject, as it involves a lot of seemingly empty space that’s nevertheless full of very real forces, all of which must be taken into account lest one’s spacecraft ends up performing a sudden lithobraking maneuver into a planet or other significant collection of matter in said mostly empty space. The primary concern here is that of gravitational pull, and the way it affects one’s trajectory and velocity. With a single planet providing said gravitational pull this is quite straightforward to determine, but add in another body (like the Moon) and things get trickier. Add another big planetary body (or a star like our Sun), and you suddenly got yourself the restricted three-body problem, which has vexed mathematicians and others for centuries.
The three-body problem concerns the initial positions and velocities of three point masses. As they orbit each other and one tries to calculate their trajectories using Newton’s laws of motion and law of universal gravitation (or their later equivalents), the finding is that of a chaotic system, without a closed-form solution. In the context of orbital mechanics involving the Earth, Moon and Sun this is rather annoying, but in 1772 Joseph-Louis Lagrange found a family of solutions in which the three masses form an equilateral triangle at each instant. Together with earlier work by Leonhard Euler led to the discovery of what today are known as Lagrangian (or Lagrange) points.
Having a few spots in an N-body configuration where you can be reasonably certain that your spacecraft won’t suddenly bugger off into weird directions that necessitate position corrections using wasteful thruster activations is definitely a plus. This is why especially space-based observatories such as the James Webb Space Telescope love to hang around in these spots.
Stable and Unstable Stable
Although the definition of Lagrange points often makes it sound like you can put a spacecraft in that location and it’ll remain there forever, it’s essential to remember that ‘stationary’ only makes sense in particular observer’s reference frame. The Moon orbits the Earth, which orbits the Sun, which ultimately orbits the center of the Milky Way, which moves relative to other galaxies. Or it’s just the expansion of space-time which make it appear that the Milky Way moves, but that gets one quickly into the fun corners of theoretical physics.
A contour plot of the effective potential defined by gravitational and centripetal forces. (Credit: NASA)
Within the Earth-Sun system, there are five Lagrange points (L1 – L5), of which L2 is currently the home of the James Webb Space Telescope (JWST) and was the home to previous observatories (like the NASA WMAP spacecraft) that benefit from always being in the shadow of the Earth. Similarly, L1 is ideal for any Sun observatory, as like L2 it is located within easy communication distance
Perhaps shockingly, the L3 point is not very useful to put any observatories or other spacecraft, as the Sun would always block communication with Earth. What L3 has in common with L1 and L2 is that all of these are unstable Lagrange points, requiring course and attitude adjustments approximately every 23 days. This contrasts with L4 and L5, which are the two ‘stable’ points. This can be observed in the above contour plot, where L4 and L5 are on top of ‘hills’ and L1 through L3 are on ‘saddles’ where the potential curves up in one direction and down another.
One way to look at it is that satellites placed in the unstable points have a tendency to ‘wander off’, as they don’t have such a wide region of relatively little variance (contour lines placed far from each other) as L4 and L5 do. While this makes these stable points look amazing, they are not as close to Earth as L1 and L2, and they have a minor complication in the fact that they are already occupied, much like the Earth-Moon L4 and L5 points.
Because of how stable the L4 and L5 points are, the Earth-Moon system ones have found themselves home to the Kordylewski clouds. These are effectively concentrations of dust which were first photographed by Polish astronomer Kazimierz Kordylewski in 1961 and confirmed multiple times since. Although a very faint phenomenon, there are numerous examples of objects caught at these points in e.g. the Sun-Neptune system (Neptune trojans) and the Sun-Mars system (Mars trojans). Even our Earth has picked up a couple over the years, many of them asteroids. Of note that is the Earth’s Moon is not in either of these Lagrange points, having become gravitationally bound as a satellite.
All of which is a long way to say that it’s okay to put spacecraft in L4 and L5 points as long as you don’t mind fragile technology sharing the same region of space as some very large rocks, with an occasional new rocky friend getting drawn into the Lagrange point.
Stuff in Lagrange Points
A quick look at the Wikipedia list of objects at Lagrange points provides a long list past and current natural and artificial objects at these locations, across a variety of system. Sticking to just the things that we humans have built and sent into the Final Frontier, we can see that only the Sun-Earth and Earth-Moon systems have so far seen their Lagrange points collect more than space rocks and dust.
These will be joined if things go well by IMAP in 2025 along with SWFO-L1, NEO Surveyor in 2027. These spacecraft mostly image the Sun, monitor solar wind, image the Earth and its weather patterns, for which this L1 point is rather excellent. Of note here is that strictly taken most of these do not simply linger at the L1 point, but rather follow a Lissajous orbit around said Lagrange point. This particular orbital trajectory was designed to compensate for the instability of the L1-3 points and minimize the need for course corrections.
Moving on, the Sun-Earth L2 point is also rather busy:
Many of the planned spacecraft that should be joining the L2 point are also observatories for a wide range of missions, ranging from general observations in a wide range of spectra to exoplanet and comet hunting.
Despite the distance and hazards of the Sun-Earth L4 and L5 points, these host the Solar TErrestrial RElations Observatory (STEREO) A and B solar observation spacecraft. The OSIRIS-REx and Hayabusa 2 spacecraft have passed through or near one of these points during their missions. The only spacecraft planned to be positioned at one of these points is ESA’s Vigil, which is scheduled to launch by 2031 and will be at L5.
Contour plot of the Earth-Moon Lagrange points. (Credit: NASA)
Only the Moon’s L2 point currently has a number of spacecraft crowding about, with NASA’s THEMIS satellites going through their extended mission observations, alongside the Chinese relay satellite Queqiao-2 which supported the Chang’e 6 sample retrieval mission.
In terms of upcoming spacecraft to join the sparse Moon Lagrange crowd, the Exploration Gateway Platform was a Boeing-proposed lunar space station, but it was discarded in favor of the Lunar Gateway which will be placed in a polar near-rectilinear halo orbit (NRHO) with an orbital period of about 7 days. This means that this space station will cover more of the Moon’s orbit rather than remain stationary. It is intended to be launched in 2027, as part of the NASA Artemis program.
Orbital Mechanics Fun
The best part of orbits is that you have so many to pick from, allowing you to not only pick the ideal spot to idle at if that’s the mission profile, but also to transition between them such as when traveling from the Earth to the Moon with e.g. a trans-lunar injection (TLI) maneuver. This involves a low Earth orbit (LEO) which transitions into a powered, high eccentric orbit which approaches the Moon’s gravitational sphere of influence.
Within this and low-energy transfer alternatives the restricted three-body problem continuously applies, meaning that the calculations for such a transfer have to account for as many variables as possible, while in the knowledge that there is no perfect solution. With our current knowledge level we can only bask in the predictable peace and quiet that are the Lagrange points, if moving away from all those nasty gravity wells like the Voyager spacecraft did is not an option.
A Texas telecommunications startup launched its first five massive “BlueBird” communications satellites into orbit on September 12. Each device is nearly 700-feet-wide when fully deployed, and like BlueWalker 3—AST SpaceMobile’s 2022 prototype, also in orbit—every BlueBird will soon shine brighter than most stars and planets in the night sky. But despite the concerns of critics and experts alike, the company’s CEO vows they are “just getting started.”
Founded in 2017, AST SpaceMobile is currently working with AT&T to construct the world’s first space-based cellular broadband network. In a statement on Thursday, AT&T Chief Operating Officer Jeff McElfresh said it’s all part of a plan to offer “a future where our customers will only be hard to reach if they choose to be.” AST SpaceMobile successfully delivered its BlueWalker 3 prototype into low-Earth orbit (LEO) in September 2022, and demonstrated it by allowing a smartphone to make a voice call the following September. Less than a month after the milestone, an international study published in Nature confirmed BlueWalker 3’s peak brightness matched that of Procyon and Achernar, two of the ten brightest stars in the night sky. Subsequent observations recorded even higher magnitudes similar to the stars that make up the constellation of Orion.
Each of the five BlueBirds now in orbit are roughly the same size as BlueWalker 3, meaning they will soon offer similar experiences for sky observers—sometimes visible even to the naked eye. But to achieve a reliable, high speed, and commercially viable satellite broadband network, AST SpaceMobile says it will need to deploy a constellation of nearly 90 satellites.
During a livestream of Thursday’s launch, company founder, chairman, and CEO Abel Avellan said many future satellite iterations will be “three-and-a-half-times larger” than the current BlueBirds. Such a scaling up would make each new, fully deployed device around 2425-square-feet in diameter, or about half the size of a regulation NBA basketball court. As Gizmodo noted on September 13, there are currently no legal restrictions for satellite brightness.
Gigantic satellite constellation arrays are growing at a rate that eclipses both regulatory oversight and experts’ concerns. Shortly after BlueWalker 3’s launch in 2022, the committee speaking on behalf of the International Astronomical Union uniformly denounced its delivery, describing it as “a big shift in the constellation satellite issue [that] should give us all reason to pause.”
AST SpaceMobile is far from the only company pursuing similar projects. SpaceX’s ongoing Starlink internet endeavor intends to eventually include as many as 7,000 satellites in orbit, in spite of its own share of public criticism. Meanwhile, advocates continue to stress the dangers of orbital pollution from decommissioned satellites and debris, often referred to as “space junk.” Without proper oversight and cleanup efforts, experts have repeatedly warned of the possibility of initiating a “Kessler cascade.” In these scenarios, the untenable amount of human-made objects leads to ever-increasing collisions, causing debris to deorbit and pose a danger to anything in its path.
In a statement provided to Popular Science, a spokesperson said that “AST SpaceMobile is committed to the responsible use of space as we advance our goal of using space-based, satellite technology to connect directly with everyday smartphones and help bring broadband to billions of people worldwide who do not have access today.”
The U.S. Space Force is testing a new ground-based satellite jamming weapon to help keep U.S. military personnel safe from potential “space-enabled” attacks.
The tests were conducted by Space Training and Readiness Command, or STARCOM, which is responsible for educating and training U.S. Space Force personnel. The satellite jammer is known as the Remote Modular Terminal (RMT) and, like other jammers, is designed to deny, degrade, or disrupt communications with satellites overhead, typically through overloading specific portions of the electromagnetic spectrum with interference.
The RMT is “small form-factor system designed to be fielded in large numbers at low-cost and operated remotely” according to Space Force statement. Specifically, the RMT will “unlock the scale to provide counterspace electronic warfare capability to all of the new Space Force components globally,” Lt. Col. Gerrit Dalman said in the statement, meaning it can be used from virtually anywhere to deny adversaries the use of satellites orbiting overhead.
Details about the test are scarce, but Space Force’s statement explains that two RMT units were installed at separate locations and controlled by a third. The jammer was evaluated according to metrics such as “system latency” and “target engagement accuracy,” as well as for how secure its communications were.
Guardians and an Airman during a test of the Space Force’s Remote Modular Terminal (RMT) in Colorado Springs, Colo., April 4, 2024. (Image credit: U.S. Air Force photo by Capt. Charles Rivezzo)
The need for new space-based and counterspace technologies has been stressed by Space Force leadership in recent months.
[…]
According to a slide deck the Space Rapid Capabilities Office presented to industry in October 2023, these jammers are “small transportable systems that can be emplaced in both garrison and austere environments,” meaning they can be used whether infrastructure is present or not.
The mysterious brightening of a galaxy far, far away has been traced to the heart of the star system and the sudden awakening of a giant black hole 1m times more massive than the sun.
Decades of observations found nothing remarkable about the distant galaxy in the constellation of Virgo, but that changed at the end of 2019 when astronomers noticed a dramatic surge in its luminosity that persists to this day.
Researchers now believe they are witnessing changes that have never been seen before, with the black hole at the galaxy’s core putting on an extreme cosmic light show as vast amounts of material fall into it.
“We discovered this source at the moment it started to show these variations in luminosity,” said Dr Paula Sánchez-Sáez, a staff astronomer at the European Southern Observatory headquarters in Garching, Germany. “It’s the first time we’ve see this in real time.”
The galaxy, which goes by the snappy codename SDSS1335+0728 and lies 300m light years away, was flagged to astronomers in December 2019 when an observatory in California called the Zwicky Transient Facility recorded a sudden rise in its brightness.
The alert prompted a flurry of new observations and checks of archived measurements from ground- and space-based telescopes to understand more about the galaxy and its past behaviour.
The scientists discovered the galaxy had recently doubled in brightness in mid-infrared wavelengths, become four times brighter in the ultraviolet, and at least 10 times brighter in the X-ray range.
What triggered the sudden brightening is unclear, but writing in Astronomy and Astrophysics, the researchers say the most likely explanation is the creation of an “active galactic nucleus” where a vast black hole at the centre of a galaxy starts actively consuming the material around it.
Active galactic nuclei emit a broad spectrum of light as gas around the black hole heats up and glows, and surrounding dust particles absorb some wavelengths and re-radiate others.
But it is not the only possibility. The team has not ruled out an exotic form of “tidal disruption event”, a highly restrained phrase to describe a star that is ripped apart after straying too close to a black hole.
Tidal disruption events tend to be brief affairs, brightening a galaxy for no more than a few hundred days, but more measurements are needed to rule out the process. “With the data we have at the moment, it’s impossible to disentangle which of these scenarios is real,” said Sánchez-Sáez. “We need to keep monitoring the source.”
[…] The Chinese Academy of Sciences (CAS) has released the highest-resolution geological maps of the Moon yet. The Geologic Atlas of the Lunar Globe, which took more than 100 researchers over a decade to compile, reveals a total of 12,341 craters, 81 basins and 17 rock types, along with other basic geological information about the lunar surface. The maps were made at the unprecedented scale of 1:2,500,000.
[…]
The CAS also released a book called Map Quadrangles of the Geologic Atlas of the Moon, comprising 30 sector diagrams which together form a visualization of the whole Moon.
Jianzhong Liu, a geochemist at the CAS Institute of Geochemistry in Guiyang and co-leader of the project, says that existing Moon maps date from the 1960s and 1970s. “The US Geological Survey used data from the Apollo missions to create a number of geological maps of the Moon, including a global map at the scale of 1:5,000,000 and some regional, higher-accuracy ones near the landing sites,” he says. “Since then, our knowledge of the Moon has advanced greatly, and those maps could no longer meet the needs for future lunar research and exploration.”
[…]
Liu says that his team has already started work to improve the resolution of the maps, and will produce regional maps of higher accuracy on the basis of scientific and engineering needs. In the meantime, the completed atlas has been integrated into a cloud platform called the Digital Moon, and will eventually become available to the international research community.
A spacecraft containing pharmaceutical drugs that were grown on orbit has finally returned to Earth today after more than eight months in space.
Varda Space Industries’ in-space manufacturing capsule, called Winnebago-1, landed in the Utah desert at around 4:40 p.m. EST. Inside the capsule are crystals of the drug ritonavir, which is used to treat HIV/AIDS. It marks a successful conclusion of Varda’s first experimental mission to grow pharmaceuticals on orbit, as well as the first time a commercial company has landed a spacecraft on U.S. soil, ever.
The capsule will now be sent back to Varda’s facilities in Los Angeles for analysis, and the vials of ritonavir will be shipped to a research company called Improved Pharma for post-flight characterization, Varda said in a statement. The company will also be sharing all the data collected through the mission with the Air Force and NASA, per existing agreements with those agencies.
The first-of-its-kind reentry and landing is also a major win for Rocket Lab, which partnered with Varda on the mission. Rocket Lab hosted Varda’s manufacturing capsule inside its Photon satellite bus; through the course of the mission, Photon provided power, communications, attitude control and other essential operations. At the mission’s conclusion, the bus executed a series of maneuvers and de-orbit burns that put the miniature drug lab on the proper reentry trajectory. The final engine burn was executed shortly after 4 p.m. EST.
[…] how can we determine the mass of something larger, such as the Milky Way? One method is to estimate the number of stars in the galaxy and their masses, then estimate the mass of all the interstellar gas and dust, and then rough out the amount of dark matter… It all gets very complicated.
A better way is to look at how the orbital speed of stars varies with distance from the galactic center. This is known as the rotation curve and gives an upper mass limit on the Milky Way, which seems to be around 600 billion to a trillion solar masses. The wide uncertainty gives you an idea of just how difficult it is to measure our galaxy’s mass. But a new study introduces a new method, and it could help astronomers pin things down.
Estimated escape velocities at different galactic radii. Credit: Roche, et al
The method looks at the escape velocity of stars in our galaxy. If a star is moving fast enough, it can overcome the gravitational pull of the Milky Way and escape into interstellar space. The minimum speed necessary to escape depends upon our galaxy’s mass, so measuring one gives you the other. Unfortunately, only a handful of stars are known to be escaping, which is not enough to get a good handle on galactic mass. So the team looked at the statistical distribution of stellar speeds as measured by the Gaia spacecraft.
The method is similar to weighing the Moon with a handful of dust. If you were standing on the Moon and tossed dust upward, the slower-moving dust particles would reach a lower height than faster particles. If you measured the speeds and positions of the dust particles, the statistical relation between speed and height would tell you how strongly the Moon pulls on the motes, and thus the mass of the Moon. It would be easier just to bring our kilogram and scale to measure lunar mass, but the dust method could work.
In the Milky Way, the stars are like dustmotes, swirling around in the gravitational field of the galaxy. The team used the speeds and positions of a billion stars to estimate the escape velocity at different distances from the galactic center. From that, they could determine the overall mass of the Milky Way. They calculated a mass of 640 billion Suns.
This is on the lower end of earlier estimates, and if accurate it means that the Milky Way has a bit less dark matter than we thought.
Our planet sits in the Habitable Zone of our Sun, the special place where water can be liquid on the surface of a world. But that’s not the only thing special about us: we also sit in the Galactic Habitable Zone, the region within the Milky Way where the rate of star formation is just right.
The Earth was born with all the ingredients necessary for life – something that most other planets lack. Water as a solvent. Carbon, with its ability to form long chains and bind to many other atoms, a scaffold. Oxygen, easily radicalized and transformable from element to element, to provide the chain reactions necessary to store and harvest energy. And more: hydrogen, phosphorous, nitrogen. Some elements fused in the hearts of stars, other only created in more violent processes like the deaths of the most massive stars or the collisions of exotic white dwarfs.
And with that, a steady, long-lived Sun, free of the overwhelming solar flares that could drown the system in deadly radiation, providing over 10 billion years of life-giving warmth. Larger stars burn too bright and too fast, their enormous gravitational weight accelerating the fusion reactions in their cores to a frenetic pace, forcing the stars to burn themselves out in only a few million years. And on the other end of the spectrum sit the smaller red dwarf stars, some capable of living for 10 trillion years or more. But that longevity does not come without a cost. With their smaller sizes, their fusion cores are not very far from their surfaces, and any changes or fluctuations in energy result in massive flares that consume half their faces – and irradiate their systems.
And on top of it all, our neighborhood in the galaxy, on a small branch of a great spiral arm situated about 25,000 light-years from the center, seems tuned for life: a Galactic Habitable Zone.
Too close to the center and any emerging life must contend with an onslaught of deadly radiation from countless stellar deaths and explosions, a byproduct of the cramped conditions of the core. Yes, stars come and go, quickly building up a lot of the heavy elements needed for life, but stars can be hundreds of times closer together in the core. The Earth has already suffered some extinction events likely triggered by nearby supernovae, and in that environment we simply wouldn’t stand a chance. Explosions would rip away our protective ozone layer, exposing surface life to deadly solar UV radiation, or just rip away our atmosphere altogether.
And beyond our position, at greater galactic radii, we find a deserted wasteland. Yes, stars appear and live their lives in those outskirts, but they are too far and too lonely to effectively spread their elemental ash to create a life-supporting mixture. There simply isn’t enough density of stars to support sufficient levels of mixing and recycling of elements, meaning that it’s difficult to even build a planet out there in the first place.
And so it seems that life would almost inevitably arise here, on this world, around this Sun, in this region of the Milky Way galaxy. There’s little else that we could conceivably call home.
Astronomers have discovered stars that appear to be blowing out plumes of smoke. The “old smokers”, as they have been nicknamed, challenge our ideas of what happens at the end of giant stars’ lives.
Generally, when red giant stars grow old, they begin to pulsate. They become brighter, dimmer, brighter again and so on, while simultaneously throwing off their outer layers. These pulsating stars are called Mira variables, and it is thought that the pulses are caused by waves of plasma travelling within the stars that help them shed material into space.
Read more
Is the universe conscious? It seems impossible until you do the maths
When Philip Lucas at the University of Hertfordshire in the UK and his colleagues peered towards the centre of our galaxy using the Visible and Infrared Survey Telescope for Astronomy in Chile, they saw many Mira variables – but they also spotted something else. “These old red giants not doing any pulsating – they’rejust sitting there as normal and then suddenly dimming for six months to several years,” says Lucas. “This is almost completely unheard of.”
Further observations revealed that the stars seem to be emitting huge plumes of dusty smoke that prevents their starlight reaching us. The smoke takes months to years to dissipate, offering an explanation for the prolonged dimming. This may be a new way for giant stars to end their lives, but it is unclear how or why it is happening.
The enormity of these stars gives them a powerful gravitational field that makes it difficult for them to blow any of their material away. The fact that they are not pulsating makes it even harder to explain the plumes of smoke. Lucas suggests that it may be connected to the high concentration of relatively heavy elements near the galactic centre, where most of these old smokers are located. That could make it easier for grains of dust to form and then float away as smoke. “It’s quite possible that it’s not that, but it’s the only thing that’s really weird about that region that could be connected,” he says.
The researchers are now looking for more of these strange stars – they have found about 90 so far, Lucas says. Their prevalence suggests that they could be important to the environment in the centre of the Milky Way, and maybe even more so in other galaxies with more heavy elements.
Astronomers using the NASA/ESA Hubble Space Telescope observed the smallest exoplanet where water vapor has been detected in its atmosphere. At only approximately twice Earth’s diameter, the planet GJ 9827d could be an example of potential planets with water-rich atmospheres elsewhere in our galaxy.
GJ 9827d was discovered by NASA’s Kepler Space Telescope in 2017. It completes an orbit around a red dwarf star every 6.2 days. The star, GJ 9827, lies 97 light-years from Earth in the constellation Pisces.
“This would be the first time that we can directly show through an atmospheric detection that these planets with water-rich atmospheres can actually exist around other stars,” said team member Björn Benneke of the Université de Montréal. “This is an important step toward determining the prevalence and diversity of atmospheres on rocky planets.”
The study is published in The Astrophysical Journal Letters.
However, it remains too early to tell whether Hubble spectroscopically measured a small amount of water vapor in a puffy hydrogen-rich atmosphere, or if the planet’s atmosphere is mostly made of water, left behind after a primeval hydrogen/helium atmosphere evaporated under stellar radiation.
[…]
At present the team is left with two possibilities. The planet is still clinging to a hydrogen-rich envelope laced with water, making it a mini-Neptune. Alternatively, it could be a warmer version of Jupiter’s moon Europa, which has twice as much water as Earth beneath its crust. “The planet GJ 9827d could be half water, half rock. And there would be a lot of water vapor on top of some smaller rocky body,” said Benneke.
[…]
More information: Pierre-Alexis Roy et al, Water Absorption in the Transmission Spectrum of the Water World Candidate GJ 9827 d, The Astrophysical Journal Letters (2023). DOI: 10.3847/2041-8213/acebf0
One promising technology is the Rotating Detonation Engine (RDE), which relies on one or more detonations that continuously travel around an annular channel.
In a recent hot fire test at NASA’s Marshall Space Flight Center in Huntsville, Alabama, the agency achieved a new benchmark in developing RDE technology. On September 27th, engineers successfully tested a 3D-printed rotating detonation rocket engine (RDRE) for 251 seconds, producing more than 2,630 kg (5,800 lbs) of thrust. This sustained burn meets several mission requirements, such as deep-space burns and landing operations. NASA recently shared the footage of the RDRE hot fire test (see below) as it burned continuously on a test stand at NASA Marshall for over four minutes.
While RDEs have been developed and tested for many years, the technology has garnered much attention since NASA began researching it for its “Moon to Mars” mission architecture. Theoretically, the engine technology is more efficient than conventional propulsion and similar methods that rely on controlled detonations. The first hot fire test with the RDRE was performed at Marshall in the summer of 2022 in partnership with advanced propulsion developer In Space LLC and Purdue University in Lafayette, Indiana.
During that test, the RDRE fired for nearly a minute and produced more than 1815 kg (4,000 lbs) of thrust. According to Thomas Teasley, who leads the RDRE test effort at NASA Marshall, the primary goal of the latest test is to understand better how they can scale the combustor to support different engine systems and maximize the variety of missions they could be used for. This ranges from landers and upper-stage engines to supersonic retropropulsion – a deceleration technique that could land heavy payloads and crewed missions on Mars. As Teasley said in a recent NASA press release:
“The RDRE enables a huge leap in design efficiency. It demonstrates we are closer to making lightweight propulsion systems that will allow us to send more mass and payload further into deep space, a critical component to NASA’s Moon to Mars vision.”
Meanwhile, engineers at NASA’s Glenn Research Center and Houston-based Venus Aerospace are working with NASA Marshall to identify ways to scale the technology for larger mission profiles.
[…] humans have sent over 15,000 satellites into orbit. Just over half are still functioning; the rest, after running out of fuel and ending their serviceable life, have either burned up in the atmosphere or are still orbiting the planet as useless hunks of metal.
[…]
That has created an aura of space junk around the planet, made up of 36,500 objects larger than 10 centimeters (3.94 inches) and a whopping 130 million fragments up to 1 centimeter (0.39 inches).
[…]
“Right now you can’t refuel a satellite on orbit,” says Daniel Faber, CEO of Orbit Fab. But his Colorado-based company wants to change that.
[..]
the lack of fuel creates a whole paradigm where people design their spacecraft missions around moving as little as possible.
“That means that we can’t have tow trucks in orbit to get rid of any debris that happens to be left. We can’t have repairs and maintenance
[…]
Orbit Fab has no plans to address the existing fleet of satellites. Instead, it wants to focus on those that have yet to launch, and equip them with a standardized port — called RAFTI, for Rapid Attachable Fluid Transfer Interface — which would dramatically simplify the refueling operation, keeping the price tag down.
“What we’re looking at doing is creating a low-cost architecture,” says Faber. “There’s no commercially available fuel port for refueling a satellite in orbit yet. For all the big aspirations we have about a bustling space economy, really, what we’re working on is the gas cap — we are a gas cap company.”
A rendering of the future Orbit Fab Shuttle, which will deliver fuel to satellites in need directly on orbit.
Orbit Fab
Orbit Fab, which advertizes itself with the tagline “gas stations in space,” is working on a system that includes the fuel port, refueling shuttles — which would deliver the fuel to a satellite in need — and refueling tankers, or orbital gas stations, which the shuttles could pick up the fuel from. It has advertized a price of $20 million for on-orbit delivery of hydrazine, the most common satellite propellant.
In 2018, the company launched two testbeds to the International Space Station to test the interfaces, the pumps and the plumbing. In 2021 it launched Tanker-001 Tenzing, a fuel depot demonstrator that informed the design of the current hardware.
The next launch is now scheduled for 2024. “We are delivering fuel in geostationary orbit for a mission that is being undertaken by the Air Force Research Lab,” says Faber. “At the moment, they’re treating it as a demonstration, but it’s getting a lot of interest from across the US government, from people that realize the value of refueling.”
Orbit Fab’s first private customer will be Astroscale, a Japanese satellite servicing company that has developed the first satellite designed for refueling. Called LEXI, it will mount RAFTI ports and is currently scheduled to launch in 2026.
[…]
He adds that once the pattern of sending and delivering fuel in orbit is established, the next step is to start making the fuel there. “In 10 or 15 years, we’d like to be building refineries in orbit,” he says, “processing material that is launched from the ground into a range of chemicals that people want to buy: air and water for commercial space stations, 3D printer feedstock minerals to grow plants. We want to be the industrial chemical supplier to the emerging commercial space industry.”
Before a massive star explodes as a supernova, it convulses and sends its outer layers into space, signalling the explosive energy about to follow. When the star does explode, it sends a shockwave out into its own ejected outer layer, lighting it up as different chemical elements shine with different energies and colours. Intermingled with this is any pre-existing matter near the supernova. The result is a massive expanding shell with filaments and knots of ionized gas, populated by even smaller bubbles.
“With NIRCam’s resolution, we can now see how the dying star absolutely shattered when it exploded, leaving filaments akin to tiny shards of glass behind.”
Danny Milisavljevic, Purdue University
Cassiopeia A exploded about 10,000 years ago, and the light may have reached Earth around 1667. But there’s much uncertainty, and it’s possible that English astronomer John Flamsteed observed it in 1680. It’s also a possibility that it was first observed in 1630. That’s for historians to determine.
But whenever the exact date is, the light has reached us and continues to reach us, making Cassiopeia A an object of astronomical fascination. It’s one of the most-studied SNRs, and astronomers have observed it in multiple wavelengths with different telescopes.
The SNR is about 10 light-years across and is expanding between 4,000 and 6,000 km/second. Some outlying knots are moving much more quickly, with velocities from 5,500?14,500 km/s. The expanding shell is also extremely hot, at about 30 million degrees Kelvin (30 million C/54 million F.)
The JWST’s NIRCam high-resolution image of Cass. A reveals intricate detail that remains hidden from other telescopes. Image Credit: NASA, ESA, CSA, STScI, Danny Milisavljevic (Purdue University), Ilse De Looze (UGent), Tea Temim (Princeton University)
But none of our prior images are nearly as breathtaking as these JWST images. These images are far more than just pretty pictures. The cursive swirls and knotted clumps of gas reveal some of nature’s detailed interactions between light and matter.
The JWST sees in infrared, so its images need to be translated for our eyes. The wavelengths the telescope can see are translated into different visible colours. Clumps of bright orange and light pink are most noticeable in these images, and they signify the presence of sulphur, oxygen, argon, and neon. These elements came from the star itself, and gas and dust from the region around the star are intermingled with it.
The image below highlights some parts of the Cassiopeia A SNR.
1 shows tiny knots of gas comprised of sulphur, oxygen, argon, and neon from the star itself. 2 shows what’s known as the Green Monster, a loop of green light in Cas A’s inner cavity, which is visible in the MIRI image of the SNR. Circular holes are outlined in white and purple and represent ionized gas. This is likely where debris from the explosions punched holes in the surrounding gas and ionized it. 3 shows a light echo, where light from the ancient explosion has warmed up dust which shines as it cools down. 4 shows an especially large and intricate light echo known as Baby Cas A. Baby Cas A is actually about 170 light-years beyond Cas A. Image Credit: NASA, ESA, CSA, STScI, Danny Milisavljevic (Purdue University), Ilse De Looze (UGent), Tea Temim (Princeton University)
The JWST’s MIRI image shows different details. The outskirts of the main shell aren’t orange and pink. Instead, it looks more like smoke lit up by campfire flames.
Seeing the NIRCam image (L) and the MIRI image (R) tells us about the SNR and the JWST. First of all, the NIRCam image is sharper because of its higher resolution. The NIRCam image also appears less colourful, but that’s because of the wavelengths of light being emitted that are more visible in Mid-Infrared. In the MIRI image, the outer ring is lit up more brightly than in the NIRCam image, while the MIRI image also shows the ‘Green Monster,’ the green inner ring that is invisible in the NIRCam image. Image Credit: NASA, ESA, CSA, STScI, Danny Milisavljevic (Purdue University), Ilse De Looze (UGent), Tea Temim (Princeton University)
The Hubble Space Telescope, the Spitzer Space Telescope, and the Chandra X-Ray Observatory have all studied Cas A. In fact, Spitzer’s first light image back in 1999 was of Cas A.
This X-ray image of the Cassiopeia A (Cas A) supernova remnant is the official first light image of the Chandra X-ray Observatory. The bright object near the center may be the long-sought neutron star or black hole that remained after the explosion that produced Cas A. Image Credit: By NASA/CXC/SAO – http://chandra.harvard.edu/photo/1999/0237/, Public Domain, https://commons.wikimedia.org/w/index.php?curid=33394808
The Hubble has imaged Cas A too. This image is from 2006 and is a composite of 18 separate images. While interesting and stunning at the time, the JWST’s image surpasses it in both visual and scientific detail.
This NASA/ESA Hubble Space Telescope image provides a detailed look at the tattered remains of Cassiopeia A (Cas A). It is the youngest known remnant from a supernova explosion in the Milky Way. Image Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration. Acknowledgement: Robert A. Fesen (Dartmouth College, USA) and James Long (ESA/Hubble)
The JWST’s incredible images are giving us a more detailed look at Cas A than ever. Danny Milisavljevic leads the Time Domain Astronomy research team at Purdue University and has studied SNRs extensively, including Cas A. He emphasizes how important the JWST is in his work.
“With NIRCam’s resolution, we can now see how the dying star absolutely shattered when it exploded, leaving filaments akin to tiny shards of glass behind,” said Milisavljevic. “It’s really unbelievable after all these years studying Cas A to now resolve those details, which are providing us with transformational insight into how this star exploded.”
Scientists have discovered the first indication of nuclear fission occurring amongst the stars. The discovery supports the idea that when neutron stars smash together, they create “superheavy” elements — heavier than the heaviest elements of the periodic table
[…]
“People have thought fission was happening in the cosmos, but to date, no one has been able to prove it,” Matthew Mumpower, research co-author and a scientist at Los Alamos National Laboratory, said in a statement.
The team of researchers led by North Carolina State University scientist Ian Roederer searched data concerning a wide range of elements in stars to discover the first evidence that nuclear fission could therefore be acting when neutron stars merge. These findings could help solve the mystery of where the universe‘s heavy elements come from.
[…]
The picture of so-called nucleosynthesis for heavier elements like gold and uranium, however, has been somewhat more mysterious. Scientists suspect these valuable and rare heavy elements are created when two incredibly dense dead stars — neutron stars — collide and merge, creating an environment violent enough to forge elements that can’t be created even in the most turbulent hearts of stars.
The evidence of nuclear fission discovered by Mumpower and the team comes in the form of a correlation between “light precision metals,” like silver, and “rare earth nuclei,” like europium, showing in some stars. When one of these groups of elements goes up, the corresponding elements in the other group also increases, the scientists saw.
The team’s research also indicates that elements with atomic masses — counts of protons and neutrons in an atomic nucleus — greater than 260 may exist around neutron star smashes, even if this existence is brief. This is much heavier than many of the elements at the “heavy end” of the periodic table.
“The only plausible way this can arise among different stars is if there is a consistent process operating during the formation of the heavy elements,” Mumpower said. “This is incredibly profound and is the first evidence of fission operating in the cosmos, confirming a theory we proposed several years ago.”
[…]
Neutron stars are created when massive stars reach the end of their fuel supplies necessary for intrinsic nuclear fusion processes, which means the energy that has been supporting them against the inward push of their own gravity ceases. As the outer layers of these dying stars are blown away, the stellar cores with masses between one and two times that of the sun collapse into a width of around 12 miles (20 kilometers).
This core collapse happens so rapidly that electrons and protons are forced together, creating a sea of neutrons so dense a mere tablespoon of this neutron star “stuff” would weigh more than 1 billion tons if it were brought to Earth.
When these extreme stars exist in a binary pairing, they spiral around one another. And as they spiral around one another, they lose angular momentum because they emit intangible ripples in spacetime called gravitational waves. This causes neutron stars to eventually collide, merge and, unsurprisingly given their extreme and exotic nature, create a very violent environment.
This ultimate neutron star merger releases a wealth of free neutrons, which are particles normally bound up with protons in atomic nuclei. This can allow other atomic nuclei in these environments to quickly grab these free neutrons — a process called rapid neutron capture or the “r-process.” This allows the atomic nuclei to grow heavier, creating superheavy elements that are unstable. These superheavy elements can then undergo fission to split down into lighter, stable elements like gold.
In 2020, Mumpower predicted how the “fission fragments” of r-process-created nuclei would be distributed. Following this, Mumpower’s collaborator and TRIUMF scientist Nicole Vassh calculated how the r-process would lead to the co-production of light precision metals such as ruthenium, rhodium, palladium and silver — as well as rare earth nuclei, like europium, gadolinium, dysprosium and holmium.
This prediction can be tested not only by looking at neutron star mergers but also by looking at the abundances of elements in stars that have been enriched by r-process-created material.
This new research looked at 42 stars and found the precise correlation predicted by Vassh, thus showing a clear signature of the fission and decay of elements heavier than found on the periodic table, further confirming that neutron star collisions are indeed the sites where elements heavier than iron are forged.
“The correlation is very robust in r-process enhanced stars where we have sufficient data. Every time nature produces an atom of silver, it’s also producing heavier rare earth nuclei in proportion. The composition of these element groups are in lockstep,” Mumpower concluded. “We have shown that only one mechanism can be responsible — fission — and people have been racking brains about this since the 1950s.”
The team’s research was published in the Dec. 6 edition of the journal Science.
Sir Richard Branson is leaving his space tourism company, Virgin Galactic, to stand or fall on its own two feet after declaring that his business empire will not be tipping any more cash into the project.
Branson told the Financial Times: “We don’t have the deepest pockets after COVID, and Virgin Galactic has got $1 billion, or nearly. It should, I believe, have sufficient funds to do its job on its own.”
Branson’s flight proved controversial, and attracted the ire of the Federal Aviation Authority (FAA) for venturing outside of its allocated airspace. Other issues have kept Virgin Galactic’s suborbital tourism ambitions on the ground until 2023.
Things appeared to be looking up this year as the luxury operator began commercial business again after a successful suborbital test flight and approached a near-monthly cadence. But with tickets starting at $450,000 and a maximum of four paying passengers per flight, turning a profit using the VSS Unity spaceplane and VMS Eve carrier aircraft combination is wishful thinking.
To that end, Virgin Galactic is looking to its upcoming Delta class of spaceplane, which can carry up to six passengers. It also expects eight flights – and revenues of between $21.6 million and $28.8 million per ship – per month from the forthcoming class, according to its third quarter 2023 earnings update [PDF].
However, Virgin Galactic will still be burning cash to get there. Revenue guidance for Q4 2023 stood at $3 million, while its cash flow was expected to be between $125 and 135 million. Virgin Galactic will also be switching to a quarterly cadence before pausing flights of VSS Unity in mid-2024 to focus on building the Delta ships.
Why the need to pause? As well as calling a halt to unprofitable flights, this is likely due, at least in part, to staff cuts announced by boss Michael Colglazier. All told, approximately 185 employees – around 18 percent of the workforce – are to leave the building as the biz seeks to cut costs and focus on what is most likely to make money: the Delta class spaceplanes.
Those employees will not be alone. While Branson told the FT he was “still loving” the Virgin Galactic project, that love does not appear to extend to the entrepreneur’s wallet.
His other rocket startup, Virgin Orbit, perished earlier this year
Dream Chaser, built by Sierra Space, is being prepped for transport to a NASA facility in Ohio, where it will undergo a series of tests to make sure the spaceplane can survive its heated reentry through Earth’s atmosphere. Starting these tests is crucial, demonstrating Dream Chaser’s readiness for flights and potentially transforming commercial space travel.
Sierra Space is hoping to see its spaceplane fly to the International Space Station (ISS) in 2024 as part of a contract with NASA. The first commercial spaceplane is currently at the company’s facility in Louisville, Colorado, and will soon make the roughly 60 mile (96 kilometer) journey to the Neil Armstrong Test Facility in Sandusky, Ohio, local media outlet Denver 7 reported.
The Colorado-based company was awarded a NASA Commercial Resupply Services 2 (CRS-2) contract in 2016, under which it will provide at least seven uncrewed missions to deliver cargo to and from the ISS. Sierra Space is targeting 2024 for the inaugural flight of the first model of the Dream Chaser fleet spacecraft, named Tenacity, from the Kennedy Space Center in Florida.
[…]
Dream Chaser is designed to fly to low Earth orbit, carrying cargo and passengers on a smooth ride to pitstops such as the ISS. The spaceplane will launch from Earth atop a rocket, and is designed to survive atmospheric reentry and perform runway landings on the surface upon its return. Sierra Space’s Dream Chaser is designed with foldable wings that fully unfurl once the spaceplane is in flight, generating power through solar arrays. The spaceplane is also equipped with heat shield tiles to protect it from the high temperatures of atmospheric reentry.
Unlike Virgin Galactic’s suborbital spaceplane, Sierra Space designed Dream Chaser to reach orbit and stay there for six months. The U.S. Space Force has its own spaceplane, which wrapped up a mysterious two-and-a-half-year mission in low Earth orbit in November 2022.
[…]
For its debut flight, Tenacity will ride atop United Launch Alliance’s Vulcan Centaur rocket. The spaceplane is scheduled for the rocket’s second mission, although Vulcan is yet to fly for the first time due to several delays. The spaceplane is tentatively slated for an April launch, but that still depends on the rocket’s first test flight.
In the future, Sierra Space also wants to launch crewed Dream Chaser missions to its own space station, as opposed to the Orbital Reef space station, which it is designing in collaboration with Jeff Bezos’ Blue Origin—a relationship that appears to be in doubt.
A team of astronomers have detected over 500 planet-like objects in the inner Orion Nebula and the Trapezium Cluster that they believe could shake up the very definition of a planet.
The 4-light-year-wide Trapezium Cluster sits at the heart of the Orion Nebula, or Messier 42, about 1,400 light-years from Earth. The cluster is filled with young stars, which make their surrounding gas and dust glow with infrared light.
The Webb Space Telescope’s Near-Infrared Camera (NIRCam) observed the nebula at short and long wavelengths for nearly 35 hours between September 26, 2022, and October 2, 2022, giving researchers a remarkably sharp look at relatively small (meaning Jupiter-sized and smaller) isolated objects in the nebula. These NIRCam images are some of the largest mosaics from the telescope to date, according to a European Space Agency release. Though they cannot be hosted in all their resolved glory on this site, you can check them out on the ESASky application.
A planet, per NASA, is an object that orbits a star and is large enough to have taken on a spherical shape and have cast away other objects near its size from its orbit. According to the recent team, the Jupiter-mass binary objects (or JuMBOs) are big enough to be planetary but don’t have a star they’re clearly orbiting. Using Webb, the researchers also observed low-temperature planetary-mass objects (or PMOs). The team’s results are yet to be peer-reviewed but are currently hosted on the preprint server arXiv.
[…]
In the preprint, the team describes 540 planetary mass candidates, with the smallest masses clocking in at about 0.6 times the mass of Jupiter. According to The Guardian, analysis revealed steam and methane in the JuMBOs’ atmospheres. The researchers also found that 9% of those objects are in wide binaries, equivalent to 100 times the distance between Earth and the Sun or more. That finding is perplexing, because objects of JuMBOs’ masses typically orbit a star. In other words, the JuMBOs look decidedly planet-like but lack a key characteristic of planets.
[…]
So what are the JuMBOs? It’s still not clear whether the objects form like planets—by accreting the gas and dust from a protoplanetary disk following a star’s formation—or more like the stars themselves. The Trapezium Cluster’s stars are quite young; according to the STScI release, if our solar system were a middle-aged person, the cluster’s stars would be just three or four days old. It’s possible that objects like the JuMBOs are actually common in the universe, but Webb is the first observatory that has the ability to pick out the individual objects.
How massive is the Milky Way? It’s an easy question to ask, but a difficult one to answer. Imagine a single cell in your body trying to determine your total mass, and you get an idea of how difficult it can be. Despite the challenges, a new study has calculated an accurate mass of our galaxy, and it’s smaller than we thought.
One way to determine a galaxy’s mass is by looking at what’s known as its rotation curve. Measure the speed of stars in a galaxy versus their distance from the galactic center. The speed at which a star orbits is proportional to the amount of mass within its orbit, so from a galaxy’s rotation curve you can map the function of mass per radius and get a good idea of its total mass. We’ve measured the rotation curves for several nearby galaxies such as Andromeda, so we know the masses of many galaxies quite accurately.
But since we are in the Milky Way itself, we don’t have a great view of stars throughout the galaxy. Toward the center of the galaxy, there is so much gas and dust we can’t even see stars on the far side. So instead we measure the rotation curve using neutral hydrogen, which emits faint light with a wavelength of about 21 centimeters. This isn’t as accurate as stellar measurements, but it has given us a rough idea of our galaxy’s mass. We’ve also looked at the motions of the globular clusters that orbit in the halo of the Milky Way. From these observations, our best estimate of the mass of the Milky Way is about a trillion solar masses, give or take.
The distribution of stars seen by the Gaia surveys. Credit: Data: ESA/Gaia/DPAC, A. Khalatyan(AIP) & StarHorse team; Galaxy map: NASA/JPL-Caltech/R. Hurt
This new study is based on the third data release of the Gaia spacecraft. It contains the positions of more than 1.8 billion stars and the motions of more than 1.5 billion stars. While this is only a fraction of the estimated 100-400 billion stars in our galaxy, it is a large enough number to calculate an accurate rotation curve. Which is exactly what the team did. Their resulting rotation curve is so precise, that the team could identify what’s known as the Keplerian decline. This is the outer region of the Milky Way where stellar speeds start to drop off roughly in accordance with Kepler’s laws since almost all of the galaxy’s mass is closer to the galactic center.
The Keplerian decline allows the team to place a clear upper limit on the mass of the Milky Way. What they found was surprising. The best fit to their data placed the mass at about 200 billion solar masses, which is a fifth of previous estimates. The absolute upper mass limit for the Milky Way is 540 billion, meaning that the Milky Way is at least half as massive as we thought. Given the amount of known regular matter in the galaxy, this means the Milky Way has significantly less dark matter than we thought.
NASA’s Parker Solar Probe has racked up an impressive list of superlatives in its first five years of operations: It’s the closest spacecraft to the sun, the fastest human-made object and the first mission to ever “touch the sun.”
Now, Parker has one more feather to add to its sun-kissed cap: It’s the first spacecraft ever to fly through a powerful solar explosion near the sun.
As detailed in a new study published Sept. 5 in The Astrophysical Journal—exactly one year after the event occurred—Parker Solar Probe passed through a coronal mass ejection (CME).
These fierce eruptions can expel magnetic fields and sometimes billions of tons of plasma at speeds ranging from 60 to 1,900 miles (100 to 3,000 kilometers) per second. When directed toward Earth, these ejections can bend and mold our planet’s magnetic field, generating spectacular auroral shows and, if strong enough, potentially devastate satellite electronics and electrical grids on the ground.
Cruising on the far side of the sun just 5.7 million miles (9.2 million kilometers) from the solar surface—22.9 million miles (36.8 million kilometers) closer than Mercury ever gets to the sun—Parker Solar Probe first detected the CME remotely before skirting along its flank. The spacecraft later passed into the structure, crossing the wake of its leading edge (or shock wave), and then finally exited through the other side.
A composite of images collected by Parker Solar Probe’s Wide-field Imager for Solar Probe (WISPR) instrument captures the moment the spacecraft passed through a coronal mass ejection (CME) on Sept. 5, 2022. The event becomes visible at 0:14 seconds. The sun, depicted on the left, comes closest on Sept. 6, when Parker reached its 13th perihelion. The sound in the background is magnetic field data converted into audio. Credit: NASA/Johns Hopkins APL/Naval Research Laboratory/Brendan Gallagher/Guillermo Stenborg/Emmanuel Masongsong/Lizet Casillas/Robert Alexander/David Malaspina
In all, the sun-grazing spacecraft spent nearly two days observing the CME, providing physicists an unparalleled view into these stellar events and an opportunity to study them early in their evolution.
“This is the closest to the sun we’ve ever observed a CME,” said Nour Raouafi, the Parker Solar Probe project scientist at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, which built the spacecraft within NASA’s timeline and budget, and currently manages and operates the mission. “We’ve never seen an event of this magnitude at this distance.”
The CME on Sept. 5, 2022, was an extreme one. As Parker passed behind the shock wave, its Solar Wind Electrons, Alphas and Protons (SWEAP) instrument suite clocked particles accelerating up to 840 miles (1,350 kilometers) per second. Had it been directed toward Earth, Raouafi suspects it would have been close in magnitude to the Carrington Event—a solar storm in 1859 that is held as the most powerful on record to hit Earth.
[…]
More information: O. M. Romeo et al, Near-Sun In Situ and Remote-sensing Observations of a Coronal Mass Ejection and its Effect on the Heliospheric Current Sheet, The Astrophysical Journal (2023). DOI: 10.3847/1538-4357/ace62e
A recent study submitted to Acta Astronautica explores the potential for using aerographite solar sails for traveling to Mars and interstellar space, which could dramatically reduce both the time and fuel required for such missions. This study comes while ongoing research into the use of solar sails is being conducted by a plethora of organizations along with the successful LightSail2 mission by The Planetary Society, and holds the potential to develop faster and more efficient propulsion systems for long-term space missions.
“Solar sail propulsion has the potential for rapid delivery of small payloads (sub-kilogram) throughout the solar system,” Dr. René Heller, who is an astrophysicist at the Max Planck Institute for Solar System Research and a co-author on the study, tells Universe Today. “Compared to conventional chemical propulsion, which can bring hundreds of tons of payload to low-Earth orbit and deliver a large fraction of that to the Moon, Mars, and beyond, this sounds ridiculously small. But the key value of solar sail technology is speed.”
Unlike conventional rockets, which rely on fuel in the form of a combustion of chemicals to exert an external force out the back of the spacecraft, solar sails don’t require fuel. Instead, they use sunlight for their propulsion mechanism, as the giant sails catch solar photons much like wind sails catching the wind when traveling across water. The longer the solar sails are deployed, the more solar photons are captured, which gradually increases the speed of the spacecraft.
For the study, the researchers conducted simulations on how fast a solar sail made of aerographite with a mass up to 1 kilogram (2.2 pounds), including 720 grams of aerographite with a cross-sectional area of 104 square meters, could reach Mars and the interstellar medium, also called the heliopause, using two trajectories from Earth known as direct outward transfer and inward transfer methods, respectively.
The direct outward transfer method for both the trip to Mars and the heliopause involved the solar sail both deploying and departing directly from a polar orbit around the Earth. The researchers determined that Mars being in opposition (directly opposite Earth from the Sun) at the time of solar sail deployment and departure from Earth would yield the best results for both velocity and travel time. This same polar orbit deployment and departure was also used for the heliopause trajectory, as well. For the inward transfer method, the solar sail would be delivered to approximately 0.6 astronomical units (AU) from the Sun via traditional chemical rockets, where the solar sail would deploy and begin its journey to either Mars or the heliopause. But how does an aerographite solar sail make this journey more feasible?
Image taken by The Planetary Society’s LightSail 2 on 25 November 2019 during its mission orbiting the Earth. The curved appearance of the sails is from the spacecraft’s 185-degree fisheye camera lens, and the image was processed with color-correction along with removal of parts of the distortion. (Credit: The Planetary Society)
“With its low density of 0.18 kilograms per cubic meter, aerographite undercuts all conventional solar sail materials,” Julius Karlapp, who is a Research Assistant at the Dresden University of Technology and lead author of the study, tells Universe Today. “Compared to Mylar (a metallized polyester foil), for example, the density is four orders of magnitude smaller. Assuming that the thrust developed by a solar sail is directly dependent on the mass of the sail, the resulting thrust force is much higher. In addition to the acceleration advantage, the mechanical properties of aerographite are amazing.”
Through these simulations, the researchers found the direct outward transfer method and inward transfer method resulted in the solar sail reaching Mars in 26 days and 126 days, respectively, with the first 103 days being the travel time from Earth to the deployment point at 0.6 AU. For the journey to the heliopause, both methods resulted in 5.3 years and 4.2 years, respectively, with the first 103 days of the inward transfer method also being devoted to the travel time from the Earth to the deployment point at 0.6 AU, as well. The reason the heliopause is reached in a faster time with the inward transfer method is due to the solar sail achieving maximum speed at 300 days, as opposed to achieving maximum speed with the outward transfer method at approximately 2 years.
Current travel times to Mars range between 7-9 months, which only happens during specified launch windows every two years while relying on the positions of both planets to be aligned at both launch and arrival of any spacecraft going to, or coming from, Mars. Estimating current travel times to the heliopause can be done using NASA’s Voyager 1 and Voyager 2 probes, which reached the heliopause at approximately 35 years and 41 years, respectively.
The researchers note that one major question of using solar sails is deceleration, or slowing down, upon arriving at the destination, specifically Mars, and while they mention aerocapture as one solution, they admit this still requires further study.
“Aerocapture maneuvers for hyperbolic trajectories (like flying from Earth to Mars) use the atmosphere to gradually reduce velocity due to drag,” Dr. Martin Tajmar, who is a physicist and Professor of Space System at the Dresden University of Technology and a co-author on the study, tells Universe Today. “Therefore, less fuel is required to enter the Martian orbit. We use this braking maneuver to eliminate the need for additional braking thrusters, which in turn reduces the mass of the spacecraft. We’re currently researching what alternative strategies might work for us. Yet the braking method is only one of many different challenges we are currently facing.”
While solar sail technology has been proposed by NASA as far back as the 1970s, a recent example of solar sail technology is the NASA Solar Cruiser, which is currently scheduled to launch in February 2025.
What new discoveries will researchers make about solar sail technology in the coming years and decades? Only time will tell, and this is why we science!
OSIRIS-REx weighs 4,650 pounds (or 2,110 kg). On September 8th of 2016, NASA first launched the spacecraft on its 3.8-billion mile mission to land on an asteroid and retrieve a sample.
That sample has just returned.
Throughout Sunday morning, NASA tweeted historic updates from the sample’s landing site in Utah. “We’ve spotted the #OSIRISREx capsule on the ground,” they announced about 80 minutes ago (including a 23-second video clip). “The parachute has separated, and the helicopters are arriving at the site. We’re ready to recover that sample!”
UPI notes that the capsule “reached temperatures up to 5,000 degrees Fahrenheit during reentry, so protective masks and gloves are required to handle it,” describing its payload as “a 250-gram dust sample.”
15 minutes later NASA shared footage of “the first persons to come into contact with this hardware since it was on the other side of the solar system.” A recovery team approached the capsule to perform an environmental safety sweep confirming there were no hazardous gas.
“The impossible became possible,” NASA administrator Bill Nelson said in a statement. The Guardian reports he confirmed the capsule “brought something extraordinary — the largest asteroid sample ever received on Earth.
“It’s going to help scientists investigate planet formation, it’s going to improve our understanding of the asteroids that could possibly impact the earth and it will deepen our understanding of the origin of our solar system and its formation.”
“This mission proves that NASA does big things, things that have inspired us, things that unite us…
“The mission continues with incredible science and analysis to come. But I want to thank you all, for everybody that made this Osiris-Rex mission possible.”
Professor Neil Bowles of the University of Oxford, one of the scientists who will study the sample, told the Guardian that he was excited to see the sample heading to the clean room at Johnson Space Center. “So much new science to come!”
And that 4,650-pound spacecraft is still hurtling through space. 20 minutes after delivering its sample, the craft ” fired its engines to divert past Earth toward its new mission to asteroid Apophis,” NASA reports. The name of its new mission? OSIRIS-APEX. Roughly 1,000 feet wide, Apophis will come within 20,000 miles of Earth — less than one-tenth the distance between Earth and the Moon — in 2029. OSIRIS-APEX is scheduled to enter orbit of Apophis soon after the asteroid’s close approach of Earth to see how the encounter affected the asteroid’s orbit, spin rate, and surface.
Using Solar Orbiter’s Extreme Ultraviolet Imager (EUI), the team of scientists behind the mission was able to record part of the Sun’s atmosphere at extreme ultraviolet wavelengths. The last-minute modification to the instrument involved adding a small, protruding “thumb” to block the bright light coming from the Sun such that the fainter light of its atmosphere could be made visible.
“It was really a hack,” Frédéric Auchère, an astrophysicist at the Institute of Astrophysics of the Université Paris-Sud in France, and a member of the EUI team, said in a statement. “I had the idea to just do it and see if it would work. It is actually a very simple modification to the instrument.”
EUI produces high-resolution images of the structures in the Sun’s atmosphere. The team behind the instrument added a thumb to a safety door on EUI, which slides out of the way to let light into the camera so it can capture images of the Sun. If the door stops halfway, however, the thumb ends up shielding the bright light coming from the Sun’s disc in the center so that the fainter ultraviolet light coming from the corona (the outermost part of the atmosphere) can be visible.
A new way to view the Sun
The result is an ultraviolet image of the Sun’s corona. An ultraviolet image of the Sun’s disc has been superimposed in the middle, in the area left blank by the thumb hack, according to ESA.
The corona is usually hidden by the bright light of the Sun’s surface, and can mostly be seen during a total solar eclipse. The camera hack sort of mimics that same effect of the eclipse by blocking out the Sun’s light. The Sun’s corona has long baffled scientists as it is much hotter than the surface of the Sun with temperatures reaching 1.8 million degrees Fahrenheit (1 million degrees Celsius), one of the greatest mysteries surrounding our host star.
“We’ve shown that this works so well that you can now consider a new type of instrument that can do both imaging of the Sun and the corona around it,” Daniel Müller, ESA’s Project Scientist for Solar Orbiter, said in a statement.
