Space travel and exploration was never going to be easy. Failures are sadly all too common but it’s wonderful to see missions exceed expectations. The Japanese Space Agency’s SLIM lunar lander was only supposed to survive a single day but it’s survived three brutal, harsh lunar nights and is still going. The temperatures plummet to -170C at night and the lander was never designed to operate into the night. Even sat upside down on the surface it’s still sending back pictures and data.
The Japanese agency’s lunar lander known as SLIM (Smart Lander for Investigating the Moon) began its lunar journey on 19 January 2024 when it touched down on the surface of the Moon. Its mission was to test the lunar landing technology and to collect data about the surface geology.
An artist’s conception shows Japan’s SLIM lander in its upended position on the lunar surface. (Credit: JAXA)
Unfortunately, soon after landing it became clear that the probe had landed at a strange angle, leaning forwards, resting on its face. The orientation of the solar panels was all wrong and it meant they could not generate as much electricity as expected allowing it to operate for a few hours just after dawn and just before sunset.
Of course it is important to note that a day on the Moon lasts many days compared to a day here on Earth and so, the first night for SLIM began on 31 January. Surprisingly, SLIM survived the first long night where temperatures to -170 degrees. SLIM was never designed to survive the cold harsh nights on the Moon so it was with some surprise that it powered back up successfully on the 15 February.
The operations team for SLIM were disbanded in March but to their surprise, after the second lunar night, a signal was received again. Surpassing everyones expectations it seems SLIM wasn’t going to give up yet and still sending images. The lander was even picked up after its second night by cameras on board the Chandrayaan-2 orbiter as it flew over.
Just a few days ago on Wednesday 24 January, JAXA, the Japanese Aerospace Exploration Agency announced it had survived a third night on the freezing lunar surface. Using the plucky littler lander which measures just 1.5m x 1.5m x 2m, the agency hope to be able to learn more about the origin of the Moon by analysing the surface geology.
One of the fascinating elements to the mission was the pinpoint landing technology that was being tested. On descent, the lander would be able to recognise the craters using technology that has been developed by facial recognition systems. Using the data, it would be able to determine its location with pinpoint accuracy and perform a touch down with an accuracy of 100m. The landing was successfully accurate albeit slightly wobbly leaving the lander in a strange orientation.
It’s difficult to actually visualise a universe that is changing. Things tend to happen at snails pace albeit with the odd exception. Take the formation of galaxies growing in the early universe. Their immense gravitational field would suck in dust and gas from the local vicinity creating vast collections of stars. In the very centre of these young galaxies, supermassive blackholes would reside turning the galaxy into powerful quasars. A recent survey by the James Webb Space Telescope (JWST) reveals that black holes can create a powerful solar wind that can remove gas from galaxies faster than they can form into stars, shutting off the creation of new stars.
To remove the confusion and mystique around black holes, they are the corpse of massive stars. When supermassive stars collapse at the end of their lives their core turns into a point source that is so incredibly dense that even light, travelling at 300,000 kilometres per second, is unable to escape. It’s believed that many galaxies have supermassive black holes at their core.
Swift scene change to the earlier part of the life of a star. Fusion in the core generates incredible amounts of energy as new elements are synthesised. Along with new elements, heat and light, a powerful outflow of electrically charged particles rushes away and permeates the surrounding space. Here in our Solar System, charged particles rush Earthward and on arrival we experience the glorious display of the northern lights.
Visualization of the solar wind encountering Earth’s magnetic “defenses” known as the magnetosphere. Clouds of southward-pointing plasma are able to peel back layers of the Sun-facing bubble and stack them into layers on the planet’s nightside (center, right). The layers can be squeezed tightly enough to reconnect and deliver solar electrons (yellow sparkles) directly into the upper atmosphere to create the aurora. Credit: JPL
A team of astronomers using the JWST have found that, over 90 percent of the wind that flows through a distant galaxy is made of neutral gas and to date, has been invisible. Until recently it was only possible to detect ionised gas – gas which carries an electric charge – which is warm. The neutral gas in the study revealed that neutral gas was cold but JWST was able to detect it.
The powerful outflow of neutral gas is thought to come from the supermassive blackholes at the core of some galaxies at the edge of the Universe. The team, led by Dr Rebecca Davies from Swinburne University first identified that black hole driven outflow in a distant galaxy over 10 billion light years away. The paper published in Nature explains how ‘The outflow is removing gas faster than gas is being converted into stars, indicating that the outflow is likely to have a very significant impact on the evolution of the galaxy.’
With a lack of gas and dust, star formation will slow and eventually stop. Just like a forest that always has new trees growing to replace old, dying trees, so galaxies usually have star formation to replace dying stars. Ultimately the forest, and a galaxy will be unable to grow and develop and eventually become static and slowly die with the final stars blinking out.
This is a JWST view of the Crab Nebula. Like other supernovae, a star exploded to create this scene.The result is a rapidly spinning neutron star (a pulsar) at its heart, surrounded by material rushing out from the site of the explosion. SN 2022jli could have either a neutron star or a black hole orbiting with a companion star.
The team found that the active galactic nuclei with supermassive black holes are the driving force behind this outflow of gas. Those with the most massive black holes can even strip the host galaxy of all the star forming gasses playing a major role in the evolution of the galaxy.
We are all very familiar with the concept of the Earth’s magnetic field. It turns out that most objects in space have magnetic fields but it’s quite tricky to measure them. Astronomers have developed an ingenious way to measure the magnetic field of the Milky Way using polarised light from interstellar dust grains that align themselves to the magnetic field lines. A new survey has begun this mapping process and has mapped an area that covers the equivalent of 15 times the full Moon.
Many people will remember experiments in school with iron filings and bar magnets to unveil their magnetic field. It’s not quite so easy to capture the magnetic field of the Milky Way though. The new method to measure the field relies upon the small dust grains which permeate space between the stars. The grains of dust are similar in size to smoke particles but they are not spherical. Just like a boat turning itself into the current, the dust particles’ long axis tends to align with the local magnetic field. As they do, they emit a glow in the same frequency as the cosmic background radiation and it is this that astronomers have been tuning in to.
Infrared image of the shockwave created by the massive giant star Zeta Ophiuchi in an interstellar dust cloud. Credit: NASA/JPL-Caltech; NASA and The Hubble Heritage Team (STScI/AURA); C. R. O’Dell, Vanderbilt University
Not only do the particles glow but they also absorb starlight that passes through them just like polarising filters. The polarisation of light is familiar to photographers that might use polarising filters to darken skies and manage reflections. The phenomenon of polarisation refers to the propagation of light. As it moves through a medium it carries energy from one place to another but on the way it displays wave like characteristics. The wave nature is made up of alternating displacements of the medium through which they are travelling (imagine a wave in water). The displacement is not always the same as the direction of travel; sometimes it is parallel and at other times it is perpendicular. In polarisation, the displacement is limited to one direction only.
In the particles in interstellar space, the polarising properties capture the magnetic field and polarise the light that travels through them revealing the details of the magnetic field. Just as they are on Earth, magnetic field lines are of crucial importance to galactic evolution. They regulate star formation, shape the structure of a galaxy and like gigantic galactic rivers, shape and direct the flow fo gas around the galaxy.
Researchers from the Inter-University Institute for High Energies in Belgium used the PASIPHAE survey – an international collaboration to explore the magnetic field from the polarisation in interstellar dust – to start the process. They measured the polarisation of more than 1500 stars which covered an area of the sky no more than 15 times the size of the full Moon. The team then used data from the Gaia astrometry satellite and a new algorithm to map the magnetic fields in the galaxy in that part of the sky.
This is the first time that any large scale project has attempted to map the gravitational field of the Milky Way. It will take some time to complete the full mapping but it when complete it will provide great insight not just into the magnetic field of galaxies but to the evolution of galaxies across the universe.
Solar Sails are an enigmatic and majestic way to travel across the gulf of space. Drawing an analogy to the sail ships of the past, they are one of the most efficient ways of propelling craft in space. On Tuesday a RocketLab Electron rocket launched NASA’s new Advanced Composite Solar Sail System. It aims to test the deployment of large solar sails in low-earth orbit and on Wednesday, NASA confirmed they had successfully deployed a 9 metre sail.
In 1886 the motor car was invented. In 1903 humans made their first powered flight. Just 58 years later, humans made their first trip into space on board a rocket. Rocket technology has changed significantly over the centuries, yes centuries. The development of the rocket started way back in the 13th Century with the Chinese and Mongolians firing rocket propelled arrows at each other. Things moved on somewhat since then and we now have solid and liquid rocket propellant, ion engines and solar sails with more technology in the wings.
A SpaceX Falcon 9 rocket rises from its Florida launch pad to send Intuitive Machines’ Odysseus moon lander spaceward. (NASA via YouTube)
Solar sails are of particular interest because they harness the power of sun, or star light to propel probes across space. The idea isn’t knew though, Johannes Kepler (of planetary motion fame) first suggested that sunlight could be used to push spacecraft in the 17th Century in his works entitled ‘Somnium’. We had to wait until the 20h Century though before Russian scientist Konstantin Tsiolkovsky outlined the principle of how solar sails might actually work. Carl Sagan and other members of the Planetary Society start to propose missions using solar sails in the 70’s and 80’s but it wasn’t until 2010 that we saw the first practical solar sail vehicle, IKAROS.
Image of the fully deployed IKAROS solar sail, taken by a separation camera. Credit: JAXA
The concept of solar sails is quite simple to understand, relying upon the pressure of sunlight. The sails are angled such that photons strike the reflective sail and bounce off it to push the spacecraft forward. It does of course take a lot of photons to accelerate a spacecraft using light but slowly, over time it is a very efficient propulsion system requiring no heavy engines or fuel tanks. This reduction of mass makes it easier for solar sails to be accelerated by sunlight but the sail sizes have been limited by the material and structure of the booms that support them.
NASA have been working on the problem with their Next Generation Solar Sail Boom Technology. Their Advanced Composite Solar Sail System uses a CubeSat built by NanoAvionics to test a new composite boom support structure. It is made from flexible polymer and carbon fibre materials to create a stiffer, lighter alternative to existing support structure designs.
On Wednesday 24 April, NASA confirmed that the CubeSat has reached low-Earth orbit and deployed a 9 metre sail. They are now powering up the probe and establishing ground contract. It took about 25 minutes to deploy the sail which spans 80 square metres. If the conditions are right, it may even be visible from Earth, possibly even rivalling Sirius in brightness.
Scientists detected the first long-predicted gravitational wave in 2015, and since then, researchers have been hungering for better detectors. But the Earth is warm and seismically noisy, and that will always limit the effectiveness of Earth-based detectors.
Is the Moon the right place for a new gravitational wave observatory? It might be. Sending telescopes into space worked well, and mounting a GW observatory on the Moon might, too, though the proposal is obviously very complex.
Most of astronomy is about light. The better we can sense it, the more we learn about nature. That’s why telescopes like the Hubble and the JWST are in space. Earth’s atmosphere distorts telescope images and even blocks some light, like infrared. Space telescopes get around both of those problems and have revolutionized astronomy.
Gravitational waves aren’t light, but sensing them still requires extreme sensitivity. Just as Earth’s atmosphere can introduce ‘noise’ into telescope observations, so can Earth’s seismic activity cause problems for gravitational wave detectors. The Moon has a big advantage over our dynamic, ever-changing planet: it has far less seismic activity.
We’ve known since the Apollo days that the Moon has seismic activity. But unlike Earth, most of its activity is related to tidal forces and tiny meteorite strikes. Most of its seismic activity is also weaker and much deeper than Earth’s. That’s attracted the attention of researchers developing the Lunar Gravitational-wave Antenna (LGWA).
The developers of the LGWA have written a new paper, “The Lunar Gravitational-wave Antenna: Mission Studies and Science Case.” The lead author is Parameswaran Ajith, a physicist/astrophysicist from the International Centre for Theoretical Science, Tata Institute of Fundamental Research, Bangalore, India. Ajith is also a member of the LIGO Scientific Collaboration.
A gravitational wave observatory (GWO) on the Moon would cover a gap in frequency coverage.
“Given the size of the Moon and the expected noise produced by the lunar seismic background, the LGWA would be able to observe GWs from about 1 mHz to 1 Hz,” the authors write. “This would make the LGWA the missing link between space-borne detectors like LISA with peak sensitivities around a few millihertz and proposed future terrestrial detectors like Einstein Telescope or Cosmic Explorer.”
If built, the LGWA would consist of a planetary-scale array of detectors. The Moon’s unique conditions will enable the LGWA to open a larger window into gravitational wave science. The Moon has extremely low background seismic activity that the authors describe as ‘seismic silence.’ The lack of background noise will enable more sensitive detections.
The Moon also has extremely low temperatures inside its permanently shadowed regions (PSRs.) Detectors must be super-cooled, and the cold temperatures in the PSRs make that task easier. The LGWA would consist of four detectors in a PSR crater at one of the lunar poles.
This schematic shows one of the LGWA’s detectors on the floor of a lunar PSR. Image Credit: LGWA
The LGWA is an ambitious idea with a potentially game-changing scientific payoff. When combined with telescopes observing across the electromagnetic spectrum and with neutrino and cosmic ray detectors—called multi-messenger astronomy—it could advance our understanding of a whole host of cosmic events.
The LGWA will have some unique capabilities for detecting cosmic explosions. “Only LGWA can observe astrophysical events that involve WDs (white dwarfs) like tidal disruption events (TDEs) and SNe Ia,” the authors explain. They also point out that only the LGWA will be able to warn astronomers weeks or even months in advance of solar mass compact binaries, including neutron stars, merging.
The LGWA will also be able to detect lighter intermediate-mass black hole (IMBH) binaries in the early Universe. IMBHs played a role in forming today’s supermassive black holes (SMBHs) at the heart of galaxies like our own. Astrophysicists have a lot of unanswered questions around black holes and how they’ve evolved and the LGWA should help answer some of them.
Double White Dwarf (DWD) mergers outside our galaxy are another thing that the LGWA alone will be able to sense. They can be used to measure the Hubble Constant. Over the decades, scientists have gotten more refined measurements of the Hubble constant, but there are still discrepancies.
A graphical summary of the LGWA science case, including multi-messenger studies with electromagnetic observatories and multiband observations with space-borne and terrestrial GW detectors. Image Credit: Ajith et al. 2024/LGWA
The LGWA will also tell us more about the Moon. Its seismic observations will reveal the Moon’s internal structure in more detail than ever. There’s a lot scientists still don’t know about its formation, history, and evolution. The LGWA’s seismic observations will also illuminate the Moon’s geological processes.
The LGWA mission is still being developed. Before it can be implemented, scientists need to know more about where they plan to place it. That’s where the preliminary Soundcheck mission comes in.
In 2023, the ESA selected Soundcheck into its Reserve Pool of Science Activities for the Moon. Soundcheck will not only measure seismic surface displacement, magnetic fluctuations and temperature, it will also be a technology demonstration mission. “The Soundcheck technology validation focuses on deployment, inertial sensor mechanics and readout, thermal management and platform levelling,” the authors explain.
This schematic shows one of the Soundcheck seismic stations. Image Credit: LGWA
In astronomy, astrophysics, cosmology, and related scientific endeavours, it always seems like we’re on the precipice of new discoveries and a new understanding of the Universe and how we fit into it. The reason it always seems like that is because it’s true. Humans are getting better and better at it, and the advent and flourishing of GW science exemplifies that, even though we’re just getting started. Not even a decade has passed since scientists detected their first GW.
Where will things go from here?
“Despite this well-developed roadmap for GW science, it is important to realize that the exploration of our Universe through GWs is still in its infancy,” the authors write in their paper. “In addition to the
immense impact expected on astrophysics and cosmology, this field holds a high probability for unexpected and fundamental discoveries.”
Well over 5,000 planets have been found orbiting other star systems. One of the satellites hunting for them is TESS, the Transiting Exoplanet Survey Satellite. Astronomers using TESS think they are made a rather surprising discovery; their first free-floating – or rogue – planet. The planet was discovered using gravitational microlensing where the planet passed in front of a star, distorting its light and revealing its presence.
We are all familiar with the eight planets in our Solar System and perhaps becoming familiar with the concept of exoplanets. But there is another category of planet, the rogue planets. These mysterious objects travel through space without being gravitationally bound to any star. Their origin has been cause for much debate but popular theory suggests they were ejected from their host star system during formation, or perhaps later due to gravitational interaction.
Artist impression of glory on exoplanet WASP-76b. Credit: ESA
Simulations have suggested that these ‘free-floating planets’ or FFPs should be abundant in the Galaxy yet until now, not many have been detected. The popular theory of ejection from star systems may not be the full story though. It is now thought that different formation mechanisms will be responsible for different FFP masses. Those FFPs that are high mass may form in isolation from the collapse of gas whilst those at the low mass end (comparable to Earth) are likely to have been subjected to gravitational ejection from the system. A paper published in 2023 even suggests that those FFPs are likely to outnumber those bound planets across the Galaxy!
Detecting such wandering objects among the stars is rather more of a challenge than you might expect. Their limited emission (or reflection) of electromagnetic radiation makes them pretty much impossible to observe. Enter gravitational microlensing, a technique that relies upon an FFP passing in front of a star, it’s gravity then focussing light from the distant star resulting in a brief brightness change as the planet moves along its line of sight. To date, only three FFPs have been detected from Earth using this technique.
A team of astronomers have been using TESS to search for such microlensing events. TESS was launched in April 2018 and whilst in orbit, scans large chunks of sky to monitor the brightness of tens of thousands of stars. The detection of light changes may reveal the passage of an FFP as it drifts silently in front of the star. It’s not an easy hunt though as asteroids in our Solar System, exoplanets bound to stars and even stellar flares can all give false indications but thankfully the team led by Michelle Kunimoto have algorithms that will help to identify potential targets.
Illustration of NASA’s Transiting Exoplanet Survey Satellite. Credit: NASA’s Goddard Space Flight Center
The team published their findings recently in the Astrophysical Journal and reported one FFP candidate event associated with the star TIC-107150013 which is 3.2 parsec away. The event lasted 0.074 days +/- 0,002 and revealed a light curve with features expected of a FFP. This marks the first FFP discovered by TESS, an exciting step along the way to start to unravel the mysteries surrounding these strange alien worlds.
Over the last few years I have been renovating my home. Building on Earth seems to be a fairly well understood process, after all we have many different materials to chose from. But what about future lunar explorers. As we head closer toward a permanent lunar base, astronauts will have very limited cargo carrying capability so will have to use local materials. On the Moon, that means relying upon the dusty lunar regolith that covers the surface. Researchers have now developed 20 different methods for creating building materials out of the stuff. They include solidification, sintering/melting, bonding solidification and confinement formation. But of all these, which is the best?
Apollo astronauts reported the surface of the Moon to be covered in a fine, powdery material, similar in texture to talcum powder. The material, known as the lunar regolith is thought to have formed by the constant bombardment from meteoroids over millions of years. The impacts bombarded the rocks on the Moon’s surface breaking them down into fine grains. The layer varies in depth across the surface from 5 metres to 10 metres and consists mostly of silicon dioxide, iron oxide, aluminium dioxide and a few other minerals. The fine nature of the dust makes it difficult for astronauts and machinery alike to operate on the surface and its sharp contours make it somewhat hazardous.
After taking the first boot print photo, Aldrin moved closer to the little rock and took this second shot. The dusty, sandy pebbly soil is also known as the lunar ‘regolith’. Click to enlarge. Credit: NASA
Any future engineers that visit the Moon to construct habitats will need to somehow employ the use of this material in their work. A paper published in the journal Engineering by Professor Feng from the Tsinghua University has conducted a review of possible techniques. Almost 20 techniques have been employed and these have been categorised into four main processes.
In what I can only assume to be a process similar to concrete and its reaction with water, reaction solidification takes regolith particles and reacts them with other compounds. These will have to be transported to the Moon and, when mixed with regolith, will solidify. The process would create a solid material where regolith comprises 60% to 95% of the overall mixture.
An alternative approach involves sintering or melting the regolith by subjecting it to high temperatures. The approach can create solid material composed of entirely regolith however, temperatures in excess of 1,000 degrees are required and this in itself will pose challenges and safety concerns on the lunar surface.
Bonding solidification is a process that uses other particles to bond regolith together. Similar to the reaction solidification, the result is 65% to 95% regolith in the final product. It requires lower temperatures than melting making it a safer process and it takes less time than solidification.
Finally a process known as confinement formation is an intriguing approach which uses a fabric to restrict and constrain the regolith, forming what are ultimately, bags of the stuff. This seems to be an advanced form of sand bag where the particles are not connected as they are in other processes, but still confined. 99% of the final product would be regolith and whilst it is a faster, lower temperature process, it may lack the strength of other techniques.
Based on a series of articles that were recently made available to the public, NASA predicts it could build a base on the Moon by 2022, and for cheaper than expected. Credit: NASA
Finding the best approach requires consideration of cost, performance, safety, energy consumption, and resource requirements. To address the many components, the team identified the 8IMEM quantification method which includes 8 indicators. Working through the processes that have been identified, the team recommend confinement formation as the best, most cost effective and safest approach.
The confinement formation, whilst the most cost effective and fastest method may not be suitable for all construction needs. It may be suitable for some laboratory needs for example but when it comes to living quarters may not be the best. The research will help to focus and inform future decisions on construction on the Moon.
