Universe Today

The JWST is flexing its muscles with its interferometry mode. Researchers used it to study a well-known extrasolar system called PDS 70. The goal? To test the interferometry mode and see how it performs when observing a complex target.

The mode uses the telescope’s NIRISS (Near Infrared Imager and Slitless Spectrograph) as an interferometer. It’s called Aperture Masking Interferometry (AMI) and it allows the JWST to reach its highest level of spatial resolution.

A team of astronomers used the JWST’s AMI to observe the PDS 70 system. PDS 70 is a young T-Tauri star about 5.4 million years old. At that young age, its protoplanetary disk still surrounds it. PDS 70 is a well-studied system that’s caught the attention of astronomers. It’s unique because its two planets, PDS 70 b and c, make it the only multiplanet protoplanetary disk system we know of.

The researchers wanted to determine how easily the AMI would find PDS 70’s two known planets and what else it could observe in the system.

Their research is “The James Webb Interferometer: Space-based interferometric detections of PDS 70 b and c at 4.8 µm.” It’s available on the pre-print site arxiv.org and hasn’t been peer-reviewed yet. The lead author is Dori Blakely from the Department of Physics and Astronomy at the University of Victoria, BC, Canada.

PDS 70 is known for its pair of planets. PDS 70 b is about 3.2 Jupiter masses and follows a 123-year orbital period. PDS 70 c is about 7.5 Jupiter masses and follows a 191-year orbit. One of the most puzzling things about the system is that PDS 70 b appears to have its own accretion disk. The system also shows intriguing evidence of a third body, maybe another star.

The JWST’s interferometry easily detected both planets. In fact, the observations found evidence of circumplanetary disk emissions around PDS 70 b and c. “Our photometry of both PDS 70 b and c provide evidence for circumplanetary disk emission,” the researchers write. That means we can see the star and its protoplanetary disk, where planets form, and the individual circumplanetary disks around each planet. Those disks are where moons form, and seeing them in a system 366 light-years away is very impressive.

The PDS 70 system as seen by the JWST’s interferometry mode and after extensive data processing. A yellow star marks the location of PDS 70, with PDS 70 b and c also shown. The JWST shows the infrared emissions coming from the disk. Image Credit: Blakely et al. 2024.

The JWST’s AMI observations also found a third point source. Its light is different from the light from the pair of planets and more similar to the light from the star. If it’s another planet, its composition is different from the others. If it’s not another planet, that doesn’t mean it necessarily has to be another star. The JWST could be seeing scattered starlight from another gaseous, dusty structure or clump in the disk. “This indicates that what we observe is not due to a simple inner disk structure, and may hint at a complex inner disk morphology such as a spiral or clumpy features,” the researchers explain.

The unexplained third source could be something more exotic. Previous research also identified the source and suggested that it could be an accretion stream flowing between PDS 70 b and c. “We interpret its signal in the direct vicinity of planet c as tracing the accretion stream feeding its circumplanetary disk,” the authors of the previous research wrote.

These images are from previous research that used the JWST but not its interferometry mode. The top row is from the telescope’s F187N filter, and the bottom row is from the telescope’s F480M filter. The left column shows the complete images. The middle column shows the system with the disk subtracted. The right column shows the system with the disk and both known planets extracted. What remains is a potential third planet, planet “d,” and an arm-like feature and potential accretion stream. Image Credit: V. Christiaens et al. 2024.

Or, perhaps most exciting, the source could be another planet. “Another scenario is that the signal we observe is due to an additional planet interior to the orbit of PDS 70 b,” the authors explain. “Follow-up observations will be needed to determine the nature of this emission,” the authors write.

Part of the observations’ success comes from what it didn’t detect. Protoplanetary disks are dusty and difficult to examine. The JWST has a leg up on it because it can see infrared light. When used in interferometry mode, it’s a powerful tool. The fact that it failed to detect any other planets is progress, though. “Additionally, we place the deepest constraints on additional planets,” in part of the disk. These constraints will help future researchers examine the PDS 70 system and other extrasolar systems.

The results also show another of AMI’s strengths: its ability to see into parts of the parameter space that other telescopes can’t. “Furthermore, our results show that NIRISS/AMI can reliably measure relative astrometry and contrasts of young planets in a part of parameter space (small separations and moderate to high contrasts) that is unique to this observing mode, and inaccessible to all other present facilities at 4.8 µm,” the authors explain.

The JWST has already established its place in the history of astronomy. It’s delivered on its promise and has already significantly contributed to our understanding of the cosmos. The telescope’s observations with its Aperture Masking Interferometry mode will further cement its place in history.

“Here, using the power of the James Webb Interferometer, we detect PDS 70, its outer disk, and its two protoplanets, b and c. These are the first planets detected with space-based interferometry,” the authors write.

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Brown dwarfs span the line between planets and stars. By definition, a star must be massive enough for hydrogen fusion to occur within its core. This puts the minimum mass of a star around 80 Jupiters. Planets, even large gas giants like Jupiter, only produce heat through gravitational collapse or radioactive decay, which is true for worlds up to about 13 Jovian masses. Above that, deuterium can undergo fusion. Brown dwarfs lay between these two extremes. The smallest brown dwarfs resemble gas planets with surface temperatures similar to Jupiter. The largest brown dwarfs have surface temperatures around 3,000 K and look essentially like stars.

Because of this, it can be difficult to study brown dwarfs, particularly ones that don’t orbit other stars. Without much reflected or emitted light, we can’t easily analyze their spectra to determine their composition. Fortunately, some brown dwarfs do emit radio light thanks to their strong magnetic fields.

Planets such as Earth and Jupiter have strong magnetic fields, and this means they can trap ionized particles such as hydrogen. These charged particles then spiral along the magnetic field lines until they collide with the planet’s upper atmosphere, generating glowing aurora. On Earth, we see them as the Northern Lights. For brown dwarfs, we can’t see the visible light of their aurora, but we can detect their radio glow.

Recently a team looked at the auroral light from a brown dwarf known as W1935. It is a cold brown dwarf 47 light-years from Earth with a surface temperature of just 200 °C. Within the spectra the team found light emissions from methane. While the presence of methane was expected in cold brown dwarfs, the fact that the methane emitted light was not. This means the atmosphere of W1935 likely has a thermal inversion, where the upper atmosphere is warmer than the lower layers.

This is true for the atmosphere of Earth but is driven by solar radiance. W1935 doesn’t orbit a star, so how can its upper atmosphere get so warm? One possible explanation is that the brown dwarf has an undetected small companion. This companion could be ejecting material similar to the way Saturn’s moon Enceleadus ejects water vapor. Once ionized in the vacuum of space, it would become trapped by the magnetic fields of W1935, eventually colliding with the brown dwarf’s upper atmosphere and giving it a bit of thermal heating.

This discovery shows that even the smallest brown dwarfs defy easy classification. Though they resemble planets, they may have their own planetary system like a star.

Reference: Faherty, Jacqueline K., et al. “Methane emission from a cool brown dwarf.” Nature 628.8008 (2024): 511-514.

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Life on Earth would not be possible without food, water, light, a breathable atmosphere and surprisingly, a magnetic field. Without it, Earth, and its inhabitants would be subjected to the harmful radiation from space making life here, impossible. If we find exoplanets with similar magnetospheres then those worlds may well be habitable. The Square Kilometer Array (SKA) which is still under construction should be able to detect such magnetospheres from radio emissions giving us real insight into our exoplanet cousins. 

The magnetic field of Earth is the result of churning motion of liquid iron and nickel in the outer core. The resultant magnetic field has properties of a giant magnet with a north pole and a south pole and it extends from the core outward, enveloping the entire planet.  The presence of the field stops harmful solar radiation and cosmic particles. Magnetic fields are not static though and it is not uncommon for them to flip, as has happened to our own magnetic field. 

Since we have been hunting exoplanets (and to date, over 5,000 have been discovered) it has become clear that there are a good number of super sized gas gas giants. As our detection technology and methods improve, smaller, more Earth like planets are starting to be discovered. It is therefore not unreasonable to think that, among them, there may well be alien planets with magnetic fields making them, therefore good candidates for habitable environments. 

Artist impression of glory on exoplanet WASP-76b. Credit: ESA

Understanding exoplanet magnetic fields is in its infancy. So far, we have only explored magnetic fields around the planets in our Solar System. What we do know is that any planetary magnetic field emits radio signals due to the Electron Cyclotron Maser Instability mechanism. Sounds like something out of StarTrek or StarWars depending on your preference but either way, electromagnetic radiation is amplified by electrons that are trapped in the field. It is this amplified radiation that can be detected remotely IF we have a radio telescope with the capability. 

A recent paper authored by Fatemeh Bagheri and team from the University of Texas explores whether it might be possible to detect the emissions using the Square Kilometre Array. The concept of the SKA is a radio interferometer with components in Australia and Africa and its headquarters in the UK. The international array of radio telescopes that are joined together electronically to operate as one collecting area of a square kilometre. It affords the ability to study the radio sky with higher sensitivity and resolution than ever before and it’s this, that Bagheri and team are focusing their attention. 

Aerial image of the South African MeerKAT radio telescope, part of the Square Kilometer Array (SKA). Credit: SKA

Using NASA’s exoplanet archive data, they calculated the strength of radio signal from 80 confirmed planets. They took the planet’s radius, mass and orbital distance from the host star, along with the stars’ mass, radius and distance form us to estimate the signal from the magnetosphere. The results were promising and suggest that, according to their analysis exoplanets; Qatar-4 b, TOI-1278 b, and WASP-173 A b would indeed emit radio signals from their magnetosphere that the SKA could detect. Unfortunately we will have to wait until 2028 when SKA is operational but already, it seems researchers are lining up to use it and this piece of research in particular looks set not only to herald a greater understanding of exoplanets but also the possibility of life in the Universe. 

Source : Exploring Radio Emissions from Confirmed Exoplanets Using SKA

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When I heard about this I felt an amused twinge of envy. Over the last year I have been using an unimpressive 4G broadband service and at best get 20 Mbps, NASA’s Psyche mission has STILL been getting 23 Mbps at 225 million km away! It’s all thanks to the prototype optical transmission system employed on the probe. It means it can get up to 100 times more data transmission rate than usual radio. 

NASA’s Pysche mission is on its way to explore the metal rich asteroid between the orbits of Mars and Jupiter called, not surprisingly Psyche. The intriguing thing about the asteroid is that it seems to be the iron rich core of an unformed planet. The spacecraft carried a wealth of scientific instruments to explore the asteroid including an imaging rig, gamma ray and neutron spectrometer, magnetometer and an X-band Gravity platform. 

It began its two year journey on 13 October with its destination, a tiny world that may help us unravel some of the mysteries of the formation of our Solar System. The theory that Psyche is a failed planetary core is not certain so this will be one of the first of its mission objectives; is it simply unmelted metal or was it a core. In order to understand this it’s necessary to work out its age. Secondary to the origin, other objectives are to explore the composition and its topography across the surface. 

Asteroid Psuche was discovered in March 1852 by Italian astronomer Annibale de Gasparis. Because he discovered it, he was allowed to name it and settled on Psyche after the Greek goddess of the soul. It orbits the Sun at a distance of between 378 million to 497 million kilometres and takes about 5 Earth years to complete an orbit. Shaped like a potato, or perhaps more accurately classed as ‘irregular’ it is actually a little ellipsoid in shape measuring 280 km across wide at its widest part and 232 km across long. 

Illustration of the metallic asteroid Psyche. Credit: Peter Rubin/NASA/JPL-Caltech/ASU

Of more interest than the objectives perhaps (although I for one am looking forward to learn more about this wonderful asteroid) was the trial communication system. The newly developed Deep Space Optical Communications technology (DSOC) is not the primary communications platform but it is there as a prototype. 

The optical system which relies upon laser technology successfully sent back engineering data at a distance of 226 million kilometres. Perhaps more impressively though, the spacecraft has shown that it can transmit at a rate of 267 Mbps (YES you read that right, just over quarter of a Gbps!) The impressive download speed was achieved on 11 December last year when a 15 second ultra high definition video was sent to Earth. Sadly though, as the spacecraft recedes, its data transmission capability will reduce. Still far better than normal radio communications though. 

Using a powerful modulated laser, the Optical Communication Telescope Laboratory in California will be able to send data at a low rate to Psyche. To receive data, a photon counting receiver has been installed at the Caltech Palomar Observatory to pickup information sent by the spacecraft. Communication has always been a great challenge in space exploration and, whilst we cannot reduce transit time for data, we can improve the amount of data sent at any one time. A great step forward in space exploration. 

Source : NASA’s Optical Comms Demo Transmits Data Over 140 Million Miles

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The Hubble Space Telescope has gone through its share of gyroscopes in its 34-year history in space. Astronauts replaced the gyros during the last servicing mission in 2009, bringing it back up to six (three with three spares), but they only last so long. Last week, HST went into safe mode because one of the gyros experienced fluctuations in power. NASA paused the telescope’s science operations today to investigate the fluctuations and perhaps come up with a fix.

With this one gyro experiencing problems, only two of the gyros remain fully operational. HST works best with three gyros, and so engineers are working to understand the issue and hopefully figure out a way to fix it remotely. However, several years ago, engineers figured out a way to still conduct science operations with only a single gyro.

HST entered safe mode on April 23, 2024 when the one gyro sent faulty readings. This particular gyro also caused Hubble to enter safe mode last November after returning similar faulty readings. The gyroscopes are part of Hubble’s Pointing Control System, which includes three Fine Guidance Sensors, reaction wheels and the gyros. This allows Hubble to track stars with incredible accuracy, helping the telescope find its way as it scans the heavens, as well as keep Hubble locked onto to its targets.

To work correctly, Hubble must be able to stay focused on a target without deviating more than 7/1000th of an arcsecond, or about the width of a human hair seen at a distance of a mile.

Hubble team created a contingency plan in preparation for a time when the spacecraft might find itself with less than three working gyros again. The team developed a two-gyro mode that substitutes other sensors for one missing gyro. Although less efficient, two-gyro mode allows Hubble to continue collecting ground-breaking science data.

The end of a Hubble gyro reveals the hair-thin wires known as flex leads. They carry data and electricity inside the gyro. Credit: NASA

NASA said that Hubble gyros fail over time, usually because of “wear and tear” of thin (less than the width of a human hair), metal wires, called flex leads that carry power in, and data out, of the mechanism. Hubble’s flex leads pass through a thick fluid inside the gyro. Over time, the flex leads begin to corrode and can physically bend or break.

During its 34-year history, Hubble has had eight out of 22 gyros fail due to a corroded flex lead. For example, in 1999, four out of six gyros had failed, with the last one failing about a month before a servicing mission was scheduled to replace them (and do other upgrades to the telescope). This meant Hubble sat in safe mode waiting for the space shuttle and astronauts to arrive.

Engineers developed a two-gyro mode when the final planned Hubble servicing mission was (temporarily) canceled following the space shuttle Columbia disaster. The mission was reinstated after outcry from scientists and the public, and so NASA figured out a way to mitigate the risks of flying the space shuttle. Servicing Mission 4 replaced all six gyros one last time in 2009.

With his feet firmly anchored on the shuttle’s robotic arm, astronaut Mike Good maneuvers to retrieve the tool caddy required to repair the Space Telescope Imaging Spectrograph during the final Hubble servicing mission in May 2009. Periodic upgrades have kept the telescope equipped with state-of-the-art instruments, which have given astronomers increasingly better views of the cosmos. Credits: NASA

However, during the time it was thought no future servicing mission would happen, the observatory was proactively put into two-gyro mode to prolong its life. During this time, the team also devised a one-gyro mode, which could further extend Hubble’s life if needed.

“We knew gyros would be a limiting factor so we started to working on a reduced gyro mode to extend their life,” the director of the Space Telescope Science Institute Ken Sembach told me back in 2015 for my book, “Incredible Stories From Space.” “As it turned out, we did need that reduced gyro mode, and now they aren’t [as big of a] limiting factor for Hubble because we now know how to use the gyro resources in a new way. That added a longer life to the mission we didn’t think we would have.”

While the difference between two-gyro mode and one gyro-mode is negligible, one-gyro mode provides the option to have one of the remaining gyros placed in reserve. As of now, three of the six gyros onboard Hubble have had a flex lead fail and are no longer functional. NASA has not announced if the faulty readings are due to flex lead fail or another issue. If this gyro fails, the team will invoke one-gyro mode.

NASA did say that all of the science instruments are in good shape and they anticipate Hubble will “continue making groundbreaking discoveries, working with other observatories throughout this decade and possibly into the next.”

Hubble launched in 1990, and recently celebrated its 34th anniversary. While everyone expected HST would revolutionize astronomy, I don’t think anyone expected it would continue to be such a productive, world-class observatory even more than a thirty years after it launched. But, please, let’s keep it going for as long as possible!

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Any event in the cosmos generates gravitational waves, the bigger the event, the more disturbance. Events where black holes and neutron stars collide can send out waves detectable here on Earth. It is possible that there can be an event in visible light when neutron stars collide so to take advantage of every opportunity an early warning is essential. The teams at LIGO-Virgo-KAGRA observatories are working on an alert system that will alert astronomers within 30 seconds fo a gravity wave event. If warning is early enough it may be possible to identify the source and watch the after glow. 

The very fabric of space-time can be thought of as a giant celestial ocean. Any movement within the ocean will generate waves. The same is true of movements and disturbances in space, causing a compression in one direction while stretching out in the perpendicular direction. Modern gravity wave detectors are usually L-shaped with beams shining down each arm of the building. The two beams are combined and the interference patterns are studied allowing the lengths of the two beams to be accurately calculated. Any change suggests the passage of a gravity wave. 

LIGO Observatory

A team of researchers at the University of Minnesota have run a study that endeavours to improve the detection of the waves. Not only do they hope to improve the detection itself but also to establish an alerting mechanism so that astronomers get a notification within 30 seconds after the event detection. 

The team used data from previous observations and created simulated gravity wave signal data so that they could test the system. But it is far more than just an alerting system. Once fully operational, it will be able to detect the shape of the signals, track how it evolves over time and even provide an estimate of the properties of the individual components that led to the waves. 

After it is fully operational, the software would detect the wave for example from neutron star or black hole collisions. The former usually too faint to be able to detect unless its location is known precisely. It would generate an alert from the wave to help precisely pinpoint the location giving an opportunity for follow up study. 

Light bursts from the collision of two neutron stars. Credit: NASA’s Goddard Space Flight Center/CI Lab

There are still many outstanding questions surrounding neutron star and black hole formation not least of which is the exact mechanism that leads to the formation of gold and uranium. 

graThe LIGO (Laser Interferometer Gravitational-Wave Observatory) has just finished its latest run but the next is due in February 2025. Between recent observing runs, enhancements and improvements have been made to improve the capability of detecting signals. Eventually of course it comes down to the data and once the current run ends, the teams will get started. 

Source : Researchers advance detection of gravitational waves to study collisions of neutron stars and black holes

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During the Space Race, scientists in both the United States and the Soviet Union investigated the concept of ion propulsion. Like many early Space Age proposals, the concept was originally explored by luminaries like Konstantin Tsiolkovsky and Hermann Oberth – two of the “forefathers of rocketry.” Since then, the technology has been validated repeatedly by missions like the Deep Space-1 (DS-1) technology demonstrator, the ESA’s Smart-1 lunar orbiter, JAXA’s Hayabusa and Hayabysa 2 satellites, and NASA’s Dawn mission.

Looking to the future of space exploration, researchers at the NASA Glenn Research Center (GRC) have been busy developing a next-generation ion engine that combines extreme fuel efficiency with high acceleration. These efforts have led to the NASA-H71M sub-kilowatt Hall-effect thruster, a small spacecraft electric propulsion (SSEP) system that will enable new types of planetary science missions. With the help of commercial partners like SpaceLogistics, this thruster will also be used to extend the lifetimes of spacecraft that are already in orbit.

Space exploration and commercial space have benefitted from the development of small spacecraft and small satellites. These missions are notable for being cost-effective since they require less propellant to launch, can be deployed in smarms, and take advantage of rideshares. Similarly, the proliferation of small satellite constellations in Low Earth Orbit (LEO) has made low-power Hall-effect thrusters the most common electric propulsion system in space today. These systems are noted for their fuel efficiency, allowing many years of orbital maneuvers, corrections, and collision avoidance.

Nevertheless, small spacecraft will need to be able to perform challenging propulsive maneuvers like achieving escape velocity, orbital capture, and other maneuvers that require significant acceleration (delta-v). The thrust required to perform these maneuvers – 8 km/s (~5 mps) of delta-v – is beyond the capability of current and commercially available propulsion technology. Moreover, low-cost commercial electric propulsion systems have limited lifetimes and typically process only about 10% of a small spacecraft’s propellant mass.

Similarly, secondary spacecraft are becoming more common thanks to rockets with excess capacity (enabling rideshare programs). Still, these are generally limited to scientific targets that align with the primary mission’s trajectory. Additionally, secondary missions typically have limited time to collect data during high-speed flybys. What is needed is an electric propulsion system that requires low power (sub-kilowatt) and has high-propellant throughout – meaning it is capable of using lots of propellant over its lifetime.

To meet this demand, engineers at NASA Glenn are taking many advanced high-power solar electric propulsion (SEP) elements developed over the past decade and are miniaturizing them. These elements were developed as part of NASA’s Moon to Mars mission architecture, with applications including the Power and Propulsion Element (PPE) of the Lunar Gateway. A SEP system was also part of the design for a Deep Space Transport (DST), the vehicle that will conduct the first crewed missions to Mars by 2040. The NASA-H71M system, however, is expected to have a major impact on small spacecraft, expanding mission profiles and durations.

According to NASA, missions using the NASA-H71M system could operate for 15,000 hours and process over 30% of the small spacecraft’s initial mass in propellant. This system could increase the reach of secondary spacecraft, allowing them to deviate from the primary mission’s trajectory and explore a wider range of scientific targets. By allowing spacecraft to decelerate and make orbital insertions, this technology could increase mission durations and the amount of time they have to study objects.

NASA-H71M Hall-effect thruster on the Glenn Research Center Vacuum Facility 8 thrust stand (left) and Dr. Jonathan Mackey tuning the thrust stand before closing and pumping down the test facility (right). Credit: NASA GRC

It’s also beyond the needs of most commercial LEO missions, and the associated costs are generally higher than what commercial missions call for. As such, NASA continues to seek partnerships with commercial developers working on small commercial spacecraft with more ambitious mission profiles. One such partner is SpaceLogistics, a wholly owned subsidiary of Northrop Grumman that provides in-orbit satellite servicing to geosynchronous satellite operators using its proprietary Mission Extension Vehicle (MEV).

This vehicle relies on Northrop Grumman NGHT-1X Hall-effect thrusters based on the NASA-H71M design. This propulsive capability will allow the MEV to reach satellites in Geosynchronous Earth Orbit (GEO), where it will dock with customer’s satellites, extending their lives for at least six years. Through a Space Act Agreement (SAA), Northrop Grumman is conducting long-duration wear tests (LDWT) at NASA Glenn’s Vacuum Facility 11. The first three MEP spacecraft are expected to launch in 2025 and extend the lives of three GEO communication satellites.

Further Reading: NASA

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The Milky Way has a missing pulsar problem in its core. Astronomers have tried to explain this for years. One of the more interesting ideas comes from a team of astronomers in Europe and invokes dark matter, neutron stars, and primordial black holes (PBHs).

Astronomer Roberto Caiozzo, of the International School for Advanced Studies in Trieste, Italy, led a group examining the missing pulsar problem. “We do not observe pulsars of any kind in this inner region (except for the magnetar PSR J1745-2900),” he wrote in an email. “This was thought to be due to technical limitations, but the observation of the magnetar seems to suggest otherwise.” That magnetar orbits Sagittarius A*, the black hole at the core of the Milky Way.

An x-ray map of the core of the Milky Way showing the position of the recently discovered magnetar orbiting the supermassive black hole Sgr A*. Courtesy Chandra and XMM-Newton.

The team examined other possible reasons why pulsars don’t appear in the core and looked closely at matnetar formation as well as disruptions of neutron stars. One intriguing idea they examined was the cannibalization of primordial black holes by neutron stars. The team explored the missing-pulsar problem by asking the question: could neutron star-primordial black hole cannibalism explain the lack of detected millisecond pulsars in the core of the Milky Way? Let’s look at the main players in this mystery to understand if this could happen.

Neutron Stars, Pulsars, and Little Black Holes, Oh My

Theory suggests that primordial black holes were created in the first seconds after the Big Bang. “PBHs are not known to exist,” Caiozzo points out, “but they seem to explain some important astrophysical phenomena.” He pointed at the idea that supermassive black holes seemed to exist at very early times in the Universe and suggested that they could have been the seeds for these monsters. If there are PHBs out there, the upcoming Nancy Grace Roman Telescope could help find them. Astronomers predict they could exist in a range of masses, ranging from the mass of a pin to around 100,000 the mass of the Sun. There could be an intermediate range of them in the middle, the so-called “asteroid-mass” PBHs. Astronomers suggest these last ones as dark matter candidates.

Primordial black holes, if they exist, could have formed by the collapse of overdense regions in the very early universe. Credit M. Kawasaki, T.T. Yanagida.

Dark matter makes up about 27 percent of the Universe, but beyond suggesting that PBH could be part of the dark matter content, astronomers still don’t know exactly what it is. There does seem to be a large amount of it in the core of our galaxy. However, it hasn’t been directly observed, so its presence is inferred. Is it bound up in those midrange PBHs? No one knows.

The third player in this missing pulsar mystery is neutron stars. They’re huge, quivering balls of neutrons left over after the death of a supergiant star of between 10 and 25 solar masses. Neutron stars start out very hot (in the range of ten million K) and cool down over time. They start out spinning very fast and they do generate magnetic fields. Some emit beams of radiation (usually in radio frequencies) and as they spin, those beams appear as “pulses” of emission. That earned them the nickname “pulsar”. Neutron stars with extremely powerful magnetic fields are termed “magnetars”.

Pulsars are fast-spinning neutron stars that emit narrow, sweeping beams of radio waves. A new study identifies the origin of those radio waves. NASA’s Goddard Space Flight Center The Missing Pulsar Problem

Astronomers have searched the core of the Milky Way for pulsars without much success. Survey after survey detected no radio pulsars within the inner 25 parsecs of the Galaxy’s core. Why is that? Caizzo and his co-authors suggested in their paper that magnetar formation and other disruptions of neutron stars that affect pulsar formation don’t exactly explain the absence of these objects in the galactic core. “Efficient magnetar formation could explain this (due to their shorter lifetime),” he said, “But there is no theoretical reason to expect this. Another possibility is that the pulsars are somehow disrupted in other ways.”

Usually, disruption happens in binary star systems where one star is more massive than the other and it explodes as a supernova. The other star may or may not explode. Something may kick it out of the system altogether. The surviving neutron star becomes a “disrupted” pulsar. They aren’t as easily observed, which could explain the lack of radio detections.

If the companion isn’t kicked out and later swells up, its matter gets sucked away by the neutron star. That spins up the neutron star and affects the magnetic field. If the second star remains in the system, it later explodes and becomes a neutron star. The result is a binary neutron star. This disruption may help explain why the galactic core seems to be devoid of pulsars.

Using Primordial Black Hole Capture to Explain Missing Pulsars

Caizzo’s team decided to use two-dimensional models of millisecond pulsars—that is, pulsars spinning extremely fast—as a way to investigate the possibility of primordial black hole capture in the galactic core. The process works like this: a millisecond pulsar interacts in some way with a primordial black hole that has less than one stellar mass. Eventually, the neutron star (which has a strong enough gravitational pull to attract the PBH) captures the black hole. Once that happens, the PBH sinks to the core of the neutron star. Inside the core, the black hole begins to accrete matter from the neutron star. Eventually, all that’s left is a black hole with about the same mass as the original neutron star. If this occurs, that could help explain the lack of pulsars in the inner parsecs of the Milky Way.

Could this happen? The team investigated the possible rates of capture of PBHs by neutron stars. They also calculated the likelihood that a given neutron star would collapse and assessed the disruption rate of pulsars in the galactic core. If not all the disrupted pulsars are or were part of binary systems, then that leaves neutron star capture of PBHs as another way to explain the lack of pulsars in the core. But, does it happen in reality?

Missing Pulsar Tension Continues

It turns out that such cannibalism cannot explain the missing pulsar problem, according to Caizzo. “We found that in our current model PBHs are not able to disrupt these objects but this is only considering our simplified model of 2 body interactions,” he said. It doesn’t rule out the existence of PHBs, only that in specific instances, such capture isn’t happening.

So, what’s left to examine? If there are PHBs in the cores and they’re merging, no one’s seen them yet. But, the center of the Galaxy is a busy place. A lot of bodies crowd the central parsecs. You have to calculate the effects of all those objects interacting in such a small space. That “many-body dynamics” problem has to account for other interactions, as well as the dynamics and capture of PBHs.

Astronomers looking to use PBH-neutron star mergers to explain the lack of pulsar observations in the core of the Galaxy will need to better understand both the proposed observations and the larger populations of pulsars. The team suggests that future observations of old neutron stars close to Sgr A* could be very useful. They’d help set stronger limits on the number of PBHs in the core. In addition, it would be useful to get an idea of the masses of these PBHs, since those on the lower end (asteroid-mass types) could interact very differently.

For More Information

Revisiting Primordial Black Hole Capture by Neutron Stars
Searching for Pulsars in the Galactic Centre at 3 and 2 mm

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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. 

source : Japan’s moon lander wasn’t built to survive a week long lunar night. It’s still going after 3

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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. 

Source : New JWST observations reveal black holes rapidly shut off star formation in massive galaxies

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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. 

Source : A first glimpse at our Galaxy’s magnetic field in 3D

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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. 

Source : Solar Sail CubeSat Has Deployed from Rocket

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