Over the years, members of the public have regularly made exciting discoveries and meaningful contributions to the scientific process through citizen science projects. These citizen scientists sometimes mine large datasets for cosmic treasures, uncovering unknown objects such as Hanny’s Voorwerp, or other times bring an unusual phenomenon to scientists’ attention, such as the discovery of the new aurora-like spectacle called STEVE. Whatever the project, the advent of citizen science projects has changed the nature of scientific engagement between the public and the scientific community.
Now, unusual brown dwarf stars discovered by citizen scientists will be observed by the James Webb Space Telescope, with the hopes of learning more about these rare objects. Excitingly, one of the citizen scientists has been named as a co-investigator on a winning Webb proposal.
The brown dwarfs that will be observed by JWST were discovered by citizen scientists participating in Backyard Worlds: Planet 9, a project from the Zooniverse collaboration that uses the power of citizen science to help distinguish real celestial objects from image artifacts in data from NASA’s Wide-field Infrared Survey Explorer (WISE) mission.
A comparison of the sizes of a low mass star, a brown dwarf, Jupiter and Earth. Credit: NASA.
Brown dwarfs are objects which have a size between that of a giant planet like Jupiter and that of a small star. The Backyard Worlds: Planet 9 project asked citizen scientists to help find the Sun’s nearest neighbors — brown dwarfs and low-mass stars — as well as search for the hypothesized ninth planet in our Solar System.
In over 5 years, the project has generated over 20 scientific papers – such as this discovery of 34 new ultracool dwarf binary systems in the Sun’s neighborhood — with over 30 citizen science as co-authors. Some of the discoveries have already been granted observing time on the Spitzer Space Telescope, NASA’s Infrared Telescope Facility, and the Keck Telescope.
Now the newest and biggest telescope in space will be observing these objects.
“Even though the process was occasionally painstaking, it was worth it,” said Arttu Sainio, who discovered one of the brown dwarfs that JWST will examine. “I ended up discovering hundreds of brown dwarf candidates and many of them have been followed up and researched.” Citizen scientists Melina Thevenot was also discovered brown dwarfs that will be observed by JWST.
Because of his long-time involvement and many discoveries, citizen scientist Dan Caselden was named as a co-investigator on a winning Webb observing proposal. The proposal called “Explaining the Diversity of Cold Worlds” will study a group of twelve brown dwarfs that all appear to have the same temperature, but still have different infrared brightness.
“We will soon see our discoveries in ways never before seen,” said Caselden, in a NASA announcement. “These are special moments that we will remember forever.”
Last year, Caselden discovered an unusual object nicknamed “The Accident,” another weird brown dwarf that was faint in some key wavelengths, suggesting it was very cold (and old), but bright in others, indicating a higher temperature than other brown dwarfs.
The Backyard Worlds: Planet 9 project continues to search for brown dwarfs and other astronomical objects near the Sun. To join in and maybe even discover your own James Webb Space Telescope target, check out the project, or other Zooniverse or Cosmoquest citizen science projects.
What do UX Tauri, RW Aurigae, AS 205, Z CMajoris, and FU Orionis have in common? They’re young stellar systems with disks where planets could form. It appears those disks were disturbed by stellar flybys or other close encounters in the recent past. Astronomers want to know: did those events disrupt planet formation in the disks? What do they do? Does this happen in other systems? And, did our own solar system experience a strange encounter in its youth?
Some answers lie in a study made by astronomer Nicolás Cuello of the University of Grenoble Alpes who heads a team that studies the role of stellar flybys. In a recent paper, they discuss the processes these systems undergo. They examined the chances of any given disk experiencing a flyby/encounter and classified the types of encounters. The team also studied a set of disks to understand what happens during each type of encounter and looked at the implications of flybys for planet formation in other systems. Finally, they looked at possible clues to a flyby that our own Solar System might have experienced.
Intruder Alert! Disk Under Attack!
It all begins when star birth happens in clouds of gas and dust. The process creates batches of hot, young stars clustered together. Over time, some of those clusters dissipate. As stars leave the nest, they may pass close to other systems, causing disruptions to planet-forming disks. Cuello and his team came to the conclusion that near encounters will stir up or even disrupt these disks at some point in their evolution.
FU Orionis and its associated nebula. It’s likely the nebula was disrupted by a flyby, and the brightening is one effect of the event. Image cedit: ESO
“Stellar flybys and encounters happen more frequently than previously appreciated,” Cuello said in an email discussion. “These likely happen when stars are very young (less than a million years) and have planet-forming discs around. These discs are heavily affected by the gravitational perturbation of nearby stars, which modifies the initial conditions at the onset of planet formation. This is why it must be taken into account in our models.”
Flybys aren’t terribly rare, according to Cuello. “I would say that at least half of the stars and their discs are affected/shaped by flybys,” he said. “One important aspect to highlight is that the probability of such perturbations decreases over time but never goes to zero. So, even more-evolved stars (with planetary systems around) can experience a flyby during their lifetime. In that case, some planets might end up on misaligned orbits with respect to the rest of the planetary system or even be captured by the perturber star.”
How Much Damage Can a Stellar Flyby Do?
In typical star-forming regions, distances matter. A majority of the stars with protoplanetary disks experience close flybys—ones within a thousand astronomical units. That’s equivalent to about half the distance from the Sun to the Oort Cloud in our Solar System. Some of those encounters can really disturb a disk. For example, if an intruder star is traveling in a prograde direction, in a parabolic orbit that penetrates the disk, it can do enough damage to alter the shape of the disk. Sometimes the damage by an intruder causes the formation of a second disk of material.
This is, in fact, what’s happening with the star FU Orionis. Thanks to a close stellar flyby that crashed through its disk, FU Orionis appears to brighten by a factor of a thousand in about a year. And, such disruptions are evident in other young systems, too.
A gallery of flyby candidates disrupted by stellar flybys is shown in scattered light. Images courtesy Francois Menard (ISO-Oph 2, DO Tau, RW Aur, and FU Ori courtesy of Iain Hammond), Nicolas Cuello, Daniel J. Price.
During some encounters, the disk goes through what’s called “tidal truncation”. That can remove up to 80 percent of the disk’s mass. This has a catastrophic effect on planet formation because the encounter reduces the amount of material needed to form protoplanets. Such flybys might also create dust traps. Theoretically, those could be places where planetesimals could grow, given enough time.
In some cases, a close flyby can scatter planets within systems, or even eject a planet. Those left behind could get moved into orbits reminiscent of Pluto’s—eccentric and misaligned with the plane of the system. (To be clear, Pluto’s odd orbit is not due to a flyby. It’s more likely that gravitational influences from Neptune and other giant planets have shaped its odd orbit.)
Stellar Flybys and Our Solar System
Did our own solar system experience stellar flybys during its formation? It’s a possibility that Cuello and his colleagues explore in their paper. Such an encounter in or very near our birth cloud could have shaped the solar nebula. Ultimately that would have had an influence on the size of the disk and its mass. It’s hard to know how many times this may have happened, but remarkably, the protosolar nebula where the Sun was born was left in a fairly circular shape and most of the planets move in fairly circular, regular orbits.
Artist’s impression of the early Solar System in the making. Stellar flybys may have helped shape the birth cloud of the planets. Credit: NASA/JPL-Caltech
However, Cuello and his team concluded that the orbital arrangement of the solar system could have been affected the distribution of transNeptunian Objects (the region just beyond Neptune, where Pluto orbits). It’s also possible one or more stars passed through and disrupted the Oort Cloud. Astronomers have found a few candidates that they’re studying to see if this hypothesis plays out.
Certainly, our solar system has experienced other, more recent encounters during its lengthy history. Scholz’s Star, for example, is thought to have passed through the Oort Cloud some 70,000 years ago. Currently, this binary star lies about 22 light-years away from us. The passage didn’t seem to affect the orbits of any of the planets, but it probably had a very small effect on the numbers of Oort Cloud objects ejected into long-period orbits around the Sun. Still, it remains a useful example of the effect that a passing star can have on a planetary system or a protoplanetary disk.
We have a pretty good idea of what lurks within our solar system. We know there isn’t a Mars-sized planet orbiting between Jupiter and Saturn, nor a brown dwarf nemesis heading our way. Anything large and fairly close to the Sun would be easily spotted. But we can’t rule out a smaller, more distant world, such as the hypothetical Planet 9 (or Planet 10 if you want to throw down over Pluto). The odds against such a planet existing are fairly high, and a recent study finds it even less likely.
Many astronomers have wondered about the existence of planets that might hide at the edge of our solar system, particularly when the power of our telescopes were fairly limited. But as large sky surveys started to scan the heavens they found nothing beyond asteroid-sized worlds. But the orbits of the worlds we did find seemed to be clustered in a statistically odd way, as if they were being gravitationally perturbed by a larger object. If that were the case, this “Planet 9” would have a mass of about five Earths, and an orbital distance of a few hundred to a thousand astronomical units. In other words, just small enough and distant enough that it wouldn’t be easily seen in sky surveys.
Naturally, this motivated folks to search for the world, but it isn’t easy. Planet 9 would be too distant to be seen by reflected light, so you’d have to look for it by its faint infrared glow. And with a mass of only five Earths, it wouldn’t give off much heat. Adding to this is the fact that such a distant planet would orbit very slowly, such that within a single set of observations you wouldn’t notice it move at all. This is where this new study comes in.
To look for distant planets, the team used two infrared sky surveys, one from the InfraRed Astronomical Satellite (IRAS) and one from the AKARI Space Telescope. The two surveys were taken more than twenty years apart, giving any hypothetical planet plenty of time to move to a slightly different part of the sky. They assumed any distant planets would be fairly close to the equatorial plane, then combed through the data taking note of potential planets.
A faint integrated flux nebula near Polaris. Credit: Kush Chandaria, CC BY-SA 4.0
Surprisingly, they found more than 500 candidates. Based on the energy distribution of their spectra, most of these candidates had orbital distances less than 1,000 AU, and masses less than Neptune, which is exactly the range expected for Planet 9. But you shouldn’t get too excited. When the team looked at the infrared signatures by hand, they found none of them were that compelling. Most of them tended to be either within or near a faint integrated flux nebula, also known as galactic cirrus. They are diffuse clouds of interstellar gas that aren’t easily seen at visible wavelengths, but rather emit infrared light.
So it turns out these candidates aren’t planets, but rather the echoes of a faint nebula. Which pretty much rules out Planet 9. Hopes of another planet lost in the clouds.
Reference: Sedgwick, Chris, and Stephen Serjeant. “Searching for giant planets in the outer Solar System with far-infrared all-sky surveys.” arXiv preprint arXiv:2207.09985 (2022).
More than half a billion years ago, Earth experienced an almost-complete collapse of its magnetic field. It began in the early Cambrian period. Then, after a period of about 15 million years, the field began to grow again. The cause of that collapse and the bounceback of the field was a mystery. Then, a group of geologists studied rocks from Oklahoma that were created during that time. Magnetic markers in the rocks’ minerals pointed toward an event that began some 550 million years ago. That was before the introduction of multicellular life on our planet.
Look Deep into the Core
To understand what happened, look at our planet’s structure. Most of us learn in school that Earth is composed of layers. There’s the crust, where you’re sitting reading this right now. Underneath that is the mantle, Earth’s thickest layer. It lies over the molten outer core, which surrounds the solid inner core. That inner core has two parts—an outermost inner core and an innermost inner core. The core region lies some 2900 kilometers beneath the surface. The swirling action of liquid iron in the outer core is what generates our magnetic field. If it weren’t for that activity, we wouldn’t have a protective shield against the solar wind. In fact, without it, our planet might be more like Mars today.
The Earth’s layers, showing the Inner and Outer Core, the Mantle, and Crust. Credit: discovermagazine.com
So, what happened in the core? Why did our magnetic field fade to almost 10 percent of its strength and then regenerate again? According to John Tarduno, a professor of geophysics at the University of Rochester in New York, the cause was the formation of Earth’s solid inner core.
“The inner core is tremendously important,” he said. “Right before the inner core started to grow, the magnetic field was at the point of collapse, but as soon as the inner core started to grow, the field was regenerated.”
Paleomagnetism Reveals Changes in Our Magnetic Field
In a recent paper, Tarduno and a team of researchers cited crucial dates in the inner core’s history. They also gave a precise age estimate for the collapse and regeneration. Since they can’t reach down into the core and directly observe it, how did they figure out when these events happened? The team turned to paleomagnetism to find an answer. That’s the study of magnetic markers in rocks that were created when the rocks formed. Geologists often use this to trace the records of other changes in Earth’s magnetic field, such as pole-flipping.
Earth’s magnetic field stretches out from the core through the mantle and crust and out into space. It’s impossible to measure the magnetic field inside Earth directly. That’s due to the location and extreme temperatures of materials in the core. So, geologists thought of a better way. They looked for paleomagnetic markers in rocks and minerals that rose to the surface. Those markers are like tiny needles that lock in the direction and intensity of the magnetic field that existed when the minerals cooled after forming.
Tarduno and his team wanted to pinpoint the age and growth of Earth’s inner core using paleomagnetism to measure those particles. So, they used a CO2 laser and a superconducting quantum interference device (SQUID) magnetometer to analyze feldspar crystals from the rock anorthosite and study their perfect magnetic markers.
Dating Rocks Using Magnetism For the Win
By studying the magnetism locked in those ancient crystals, the researchers determined two new important dates. The first was when the magnetic field began to strengthen after nearly collapsing 15 million years earlier. That rapid regrowth was due to the formation of a solid inner core. It actually recharged the molten outer core and restored the magnetic field’s strength.
A depiction of Earth, first without an inner core; second, with an inner core beginning to grow, around 550 million years ago; third, with an outermost and innermost inner core, around 450 million years ago. University of Rochester researchers used paleomagnetism to determine these two key dates in the history of the inner core, which they believe restored the planet’s magnetic field just before the explosion of life on Earth. (University of Rochester illustration / Michael Osadciw)
Another interesting thing happened about 450 million years ago. That’s when the growing inner core’s structure changed. The result was a boundary between the innermost and outermost inner core. Far above the core, changes to the mantle took place due to plate tectonics on the surface.
Paleomagnetism made this new understanding of Earth’s core possible, according to Tarduno. “Because we constrained the inner core’s age more accurately, we could explore the fact that the present-day inner core is actually composed of two parts,” he said. “Plate tectonic movements on Earth’s surface indirectly affected the inner core, and the history of these movements is imprinted deep within Earth in the inner core’s structure.”
What about Magnetic Fields Elsewhere?
The team’s research into paleomagnetic clues to Earth’s interior evolution provides clues about the history and evolution of our planet. It also offers insight into how it became habitable. Finally, their work has implications for understanding the evolution of other planets in the solar system. Things could well be very different if they had no magnetic fields. For example, Mars once had a magnetic field, but it dissipated more than 4 billion years ago. That left the planet vulnerable to the solar wind and likely played a role in the loss of Martian oceans.
This figure shows a cross-section of the planet Mars revealing an inner, high-density core buried deep within the interior. Dipole magnetic field lines are drawn in blue, showing the global scale magnetic field associated with dynamo generation in the core. Ancient Mars must have had such a field, but today it is not evident. Perhaps the energy source that powered the early dynamo has shut down. Credit: NASA/JPL/GSFC
It’s not clear if Earth would have suffered the same fate if its magnetic field hadn’t regenerated. Tarduno said that our planet would have lost a lot of its water if the magnetic field had not come back. “The planet would be much drier and very different than the planet today,” he pointed out. “This research really highlights the need to have something like a growing inner core that sustains a magnetic field over the entire lifetime—many billions of years—of a planet.”
A Chinese Long March 5B rocket first stage made an uncontrolled, fiery reentry through Earth’s atmosphere over Southeast Asia today (Saturday), six days it launched a new science module to China’s Tiangong space station. While the eventual return of the booster was known, China made the decision to let it fall uncontrolled. They also did not share any tracking data, and the large size of the rocket stage drew concern about fragments possibly causing damage or casualties.
The US Space Command confirmed reentry of the debris from the roughly 30-meter-long core (100 ft.) stage of the Long March 5B occurred at 12:45 p.m. Eastern time (1645 UTC) on July 30, 2022 over the Indian Ocean.
#USSPACECOM can confirm the People’s Republic of China (PRC) Long March 5B (CZ-5B) re-entered over the Indian Ocean at approx 10:45 am MDT on 7/30. We refer you to the #PRC for further details on the reentry’s technical aspects such as potential debris dispersal+ impact location.
The core stage is about five meters wide (sixteen feet), weighing about 22 metric tons (55,000 lbs).
NASA Administrator Bill Nelson released a statement, condemning the uncontrolled entry, especially for not providing advance trajectory notice of the booster.
A rendering of the Chinese Tiangong space station. Credit: CMSA
“The People’s Republic of China (PRC) did not share specific trajectory information as their Long March 5B rocket fell back to Earth,” Nelson said. “All spacefaring nations should follow established best practices, and do their part to share this type of information in advance to allow reliable predictions of potential debris impact risk, especially for heavy-lift vehicles, like the Long March 5B, which carry a significant risk of loss of life and property. Doing so is critical to the responsible use of space and to ensure the safety of people here on Earth.”
Debris was likely observed from Kuching in Sarawak, Malaysia, and according to astronomer and orbital debris specialist Jonathan McDowell, debris would land downrange in northern Borneo, possibly Brunei.
Reentry looks to have been observed from Kuching in Sarawak, Malaysia. Debris would land downrange in northern Borneo, possbily Brunei. [corrected] https://t.co/sX6m1XMYoO
Experts say that while much of the empty rocket stage is expected to burn up on reentry, about 20 to 40 percent can survive, such as engine components designed to withstand high temperatures.
This is not the first time China has decided to let a booster fall back to Earth uncontrolled. They have done it at least twice previously, and after a similar event last year NASA said that China failed “to meet responsible standards regarding their space debris.”
China also did not share any information on why the booster would be falling back to Earth uncontrolled, but as NASA Associated Administrator for Science Thomas Zurbuchen said, something must have gone terribly wrong.
Whenever a heavy rocket plunges back to ?, uncontrolled, something terribly went wrong. Check out this list of such events by @planet4589 and draw your own conclusions. As a space community, without exceptions – we must do better! https://t.co/CaiE29dCznhttps://t.co/4102egBrXm
With the uptick in rocket launches around the world, a recent study concluded there’s a 6-10% chance that someone will die from debris falling from space over the next ten years.
Venus has almost been “the forgotten planet,” with only one space mission going there in the past 30 years. But the recent resurgence of interest in Earth’s closest neighbor has NASA and ESA committing to three new missions to Venus, all due to launch by the early 2030s.
ESA’s EnVision mission Venus is slated to take high-resolution optical, spectral and radar images of the planet’s surface. But to do so, the van-sized spacecraft will need to perform a special maneuver called aerobraking to gradually slow down and lower its orbit through the planet’s hot, thick atmosphere. Aerobraking uses atmospheric drag to slow down a spacecraft and EnVision will make thousands of passages through Venus’ atmosphere for about two years.
The aerobraking maneuver is a necessity for the mission.
“EnVision as currently conceived cannot take place without this lengthy phase of aerobraking,” said EnVision study manager Thomas Voirin. “The spacecraft will be injected into Venus orbit at a very high altitude, at approximately 250,000 km, then we need to get down to a 500 km altitude polar orbit for science operations. Flying on an Ariane 62, we cannot afford all the extra propellant it would take to lower our orbit. Instead, we will slow ourselves down through repeated passes through the upper atmosphere of Venus, coming as low as 130 km from the surface.”
Aerobraking has been performed by several spacecraft at Mars, such as the Mars Reconnaissance Orbiter and ExoMars Trace Gas Orbiter, to gradually slow the spacecraft down to place the spacecraft in the correct orbit for the mission parameters. But because of Venus’ ultra-thick atmosphere, ESA said that they are currently testing candidate spacecraft materials to “check they can safely withstand this challenging process of atmospheric surfing.”
However, this won’t be the first time a spacecraft has used aerobraking at Venus. ESA’s Venus Express, performed experimental aerobraking during the final months of its mission in 2014, gathering valuable data on the technique. The Venus Express mission was supposed to last 500 days, but the robust spacecraft ultimately spent eight years orbiting Venus before running out of fuel. It began a controlled descent, dipping further and further into Venus’s atmosphere, while using onboard accelerometers to measure its own deceleration.
Voirin said aerobraking around Venus is a challenge because the gravity of Venus is about 10 times higher than that of Mars. This means velocities are about two times higher than at Mars the spacecraft passes through the atmosphere – and heat is generated as a cube of velocity. Accordingly, EnVision has to target a lower aerobraking regime, resulting in an aerobraking phase twice as long.
Artist impression of ESA’s EnVision mission at Venus. Credit: ESA/VR2Planets/Damia Bouic
“On top of that, we are also going to be much closer to the Sun, experiencing around double the solar intensity of Earth’s, with the thick white clouds of the atmosphere reflecting a lot of sunlight straight back to space, which additionally needs to be taken into account,” Voirin said. “Then on top of all that, we realized we had to reckon with another factor over the thousands of orbits we envisage, previously only experienced in low Earth orbit: highly-erosive atomic oxygen.”
This is a phenomenon that remained unknown during the first decades of the space age. It was only when early Space Shuttle flights returned from low orbit in the early 1980s that engineers received a shock: the spacecraft’s thermal blankets had been severely eroded.
The culprit turned out to be highly reactive atomic oxygen – individual atoms of oxygen at the fringes of the atmosphere, the result of standard oxygen molecules of the kind found just above the ground being broken apart by powerful ultraviolet radiation from the Sun. Today, all missions below about 1,000 km need to be designed to resist atomic oxygen.
Space Shuttle Endeavour’s tail aglow with atomic oxygen, as seen during the STS-99 mission in February 2000. Highly erosive atomic oxygen turned out to eat away at unprotected thermal blankets during early Shuttle missions, until countermeasures were put in place. Credit: NASA
Spectral observations by past Venus orbiters of airglow above the planet confirm that atomic oxygen is widespread at the top of the Venusian atmosphere too, which is more than 90 times thicker than Earth’s.
Thomas says: “The concentration is quite high, with one pass it doesn’t matter so much but over thousands of times it starts to accumulate and ends up with a level of atomic oxygen fluence we have to take account of, equivalent to what we experience in low-Earth orbit, but at higher temperatures.”
ESA says the results of a test of materials are expected at the end of this year.
EnVision will use an array of instruments to perform comprehensive observations of Venus from its inner core to upper atmosphere to better understand how Venus and Earth evolved so differently.
The other upcoming Venus missions are DAVINCI+, a mission to understand the atmospheric evolution of Venus, and VERITAS, a mission to better map the Venusian surface and subsurface. Those two missions are aiming for launch between 2028 and 2030.
When the name Saturn is uttered, what comes to mind? For most people, the answer would probably be, “its fabulous system of rings.” There’s no doubt they are iconic, but what is perhaps lesser-known is that Jupiter, Uranus, and Neptune all have ring systems of their own. However, whereas Saturn’s rings are composed mainly of ice particles (making them highly reflective), Jupiter’s rings are composed mainly of dust grains. Meanwhile, Uranus and Neptune have rings of extremely dark particles known as tholins that are very hard to see. For this reason, none of the other gas giants get much recognition for their rings.
However, the question of why Jupiter doesn’t have larger, more spectacular rings than Saturn has been bothering astronomers for quite some time. As the larger and more massive of the two bodies, Jupiter should have rings that would dwarf Saturn’s by comparison. This mystery may have finally been resolved thanks to new research by a team from UC Riverside. According to their study, Jupiter’s massive moons (aka. Jupiter’s Galilean Moons) prevented it from developing a big, bright, beautiful ring system that would put Saturn’s to shame.
The research was conducted by Stephen R. Kane, a professor of astronomy and planetary astrophysics with the Department of Earth and Planetary Sciences at UC Riverside, and his graduate student Zhexing Li. The paper that describes their work, “The Dynamical Viability of an Extended Jupiter Ring System,” recently appeared online and is soon to be published in the Planetary Science Journal. As Kane stated in a recent article with UC Riverside News, the mystery of Jupiter’s missing rings is one he and Li were highly motivated to address.
Illustration of Jupiter and the Galilean satellites. Credit: NASA
“It’s long bothered me why Jupiter doesn’t have even more amazing rings that would put Saturn’s to shame,” he said. “If Jupiter did have them, they’d appear even brighter to us because the planet is so much closer than Saturn.” For their study, the team ran a series of dynamical N-body simulations that accounted for the orbits of Jupiter’s Galilean Moons (Io, Europa, Ganymede, and Callisto) and the availability of ring material.
Their results indicate that some of the icy material for Saturn’s rings may have come from comets, which were also responsible for distributing water to the planets of the inner Solar System billions of years ago. Jupiter would have been subject to the same level of comet activity in its early history, but the gravity of its massive moons was strong enough that they might have pushed this ice out of Jupiter’s orbit (or changed the orbit of the ice enough so that it collided with its moons). As Kane explained:
“Massive planets form massive moons, which prevents them from having substantial rings. We didn’t know these ephemeral rings existed until the Voyager spacecraft went past because we couldn’t see them. For us astronomers, they are the blood spatter on the walls of a crime scene. When we look at the rings of giant planets, it’s evidence something catastrophic happened to put that material there.”
While Saturn has many prominent moons of its own, only Titan rivals the Galileans in terms of mass. Eventhough that Saturn has 82 moons in orbit around it (that we know of), Titan accounts for 96% of their collective mass. While the gravitational interaction of these moons was enough to give Saturn its axial tilt (26.73° relative to the Sun’s ecliptic), their combined gravitational force was not strong enough to prevent Saturn from accumulating icy material into a series of bright rings.
Jupiter and its moon Europa are seen through the James Webb Space Telescope’s NIRCam instrument 2.12-micron filter. Credits: NASA, ESA, CSA, and B. Holler and J. Stansberry (STScI)
Among the images recently released by the JWST, some showed Jupiter and its faint rings, which are more prominent when seen in infrared wavelengths. This is one of many objectives of the Webb mission, which is to study the planets and moons of the outer Solar System. Using its advanced infrared cameras, Webb can spot faint ring structures and small objects around the gas giants that are hard to see in visible light. This is expected to yield valuable scientific returns, like telling us more about how planets in our Solar System formed and evolved.
Herein lies the value of studying planetary rings, where astronomers can learn more about the history of a planet because they are potential evidence of collisions with moons or comets that happened in the past. Their shape, size, and composition are all indications of events that might have led to their formation. Looking ahead, Kane plans to run simulations that address Uranus’ ring structure (smaller but more substantial than Saturn’s) to learn more about their history. A popular theory is that the same impact that is believed to have knocked Uranus on its side led to these rings.
The answer to this and other mysteries of planet formation and evolution will be the subject of considerable research in the coming years. The implications of these studies will go far beyond our Solar System and extend to the study of exoplanets, many of which are sure to have ring systems! For these distant worlds, the presence, size, and composition will provide clues about their formation and evolution.
The vast majority of stars have planets. We know that from observations of exoplanetary systems. We also know some stars don’t have planets, and perhaps they never had planets. This raises an interesting question. Suppose we see an old star that has no planets. How do we know if ever did? Maybe the star lost its planets during a close approach by another star, or maybe the planets spiraled inward and were consumed like Chronos eating his children. How could we possibly tell? A recent study on the arXiv answers half that question.
It all comes down to an odd little element known as lithium.
Lithium is the third element on the periodic table. Although most of the atoms formed during the big bang were hydrogen and helium, trace amounts of lithium were formed from the big bang. About one atom in ten billion so the current model goes. But it turns out there is less lithium in the universe than you’d expect. That’s because while other elements such as carbon, oxygen, and iron are created in the hearts of large stars, lithium is destroyed. It’s an effect known as lithium burning, and it means older stars typically don’t have much lithium present in their atmosphere.
Astronomers use this effect to distinguish between high-mass brown dwarfs and low-mass stars. If there is plenty of lithium present in the atmosphere, then fusion isn’t happening, and it’s a brown dwarf. Not much lithium and you have a star. But some stars have atmospheric lithium. They are clearly large enough and hot enough to undergo fusion, and they haven’t burned lithium out of their atmosphere. So what gives?
Modeled abundances for a star that consumes a planet vs one that does not. Credit: Savilla, J., et al
The common hypothesis has been that these unusual stars must undergo some unusual internal mixing that somehow prevents lithium from being cycled into the star’s interior where it can be consumed. This latest study proposes an alternative. Perhaps these stars happened to consume their young planets instead.
Since planets don’t burn lithium when a planet is eaten by a star its lithium is added into the star’s mix. The team simulated how that added lithium would behave in a star’s interior, and how long it would take to fade from the star’s upper layers. They found that smaller red dwarf stars are fairly effective in burning the new lithium. Because a small star has large convection zones that mix its interior really well, within a few hundred million years the new lithium is depleted. But for larger, more Sun-like stars, lithium can hang around for billions of years. Long after a planet is consumed, its lithium is still present in the stellar atmosphere.
So if we see an old Sun-like star with lithium in its atmosphere, it’s quite possible it once had planets. Stellar lithium seems to be a good sign of a sated star after a planetary meal.
JWST is doing after its micrometeorite strike, two more helicopters are flying to Mars, China will drop a 50+ meter booster… somewhere, and how do you stop the Milky Way from turning into self-replicating robot probes.
This week brought us many exciting and sometimes even scary space news. If you’re in the mood to relax and consume them in a convenient bite-size video format, you’re in luck! Because this is exactly what we have for you here:
How Bad the JWST Damage Is
A few weeks ago, we reported that JWST had taken a surprisingly large micrometeorite hit on one of its mirror segments. A new image released from NASA shows the extent of the damage. The telescope has been hit six times so far, with 5 of the 6 causing negligible damage to its optics, but the strike in May on the C3 mirror segment caused a “significant uncorrectable change.” After the strike, Webb’s operators could realign the segment to minimize the effect on its image quality.
Feast your eyes on another incredible image from the James Webb Space Telescope. This time you’re looking at galaxy IC 5332, located about 30 million light-years away. The image processing was done by Judy Schmidt, who downloaded Webb’s data in four different wavelengths and then combined them into a single image with colors that the human eye can see. You can see regions of dense star formation in the galaxy’s spiral arms, which are highlighted in the infrared spectrum.
China continues the construction of its Tiangong 3 space station, this week adding a new science module called Wentian. The new lab launched on July 23rd and was docked with the station on July 25th. One final laboratory module will be attached to the station in October called Mengtian. Once it’s complete, the station will have about 1/5th the internal volume of the International Space Station, with three crew members on board.
Satellites and space junk are always falling back to Earth, burning up in the atmosphere. Some debris is so large, however, that it can survive the trip through the atmosphere, crashing onto the surface of the Earth. Could one of these chunks kill a person? According to a new estimate, there’s a 6-10% chance that someone somewhere will die from falling space junk in the next decade. For comparison, 13 people are killed yearly by falling vending machines.
After the obvious success of the Ingenuity helicopter, which went to Mars with the Perseverance rover, NASA is planning to send more of them. It will be a part of the Sample Return Mission and there will be two helicopters. One of their tasks will be collecting samples, so they might be equipped with wheels and robotic hands. That makes future Mars missions even more exciting!
Sending swarms of self-replicating robots to explore the Universe isn’t a new idea. It’s called Von Neumann probes. It’s actually quite clever. You can explore an entire galaxy in just several million years. But there’s a challenge that we need to solve first before we should build those. It’s teaching robots to die.
The hunt for dark matter continues, with astronomers scanning the skies with telescopes, physicists generating exotic particles in the Large Hadron Collider, and new experiments watching for particle collisions. A new experiment deep underground in South Dakota has come online called LUX-Zeplin. It contains a vast volume of xenon gas surrounded by detectors. If a particle of dark matter happens to collide with xenon gas, it should generate a cascade of particles that would be detectable.
Compared to stars, planets are very dim. If we wanted to observe an Earth-sized world orbiting a sunlike star, we’d need to be able to block the light from the star to reveal a planet that’s a million million times less bright. An exciting solution to this problem is a starshade, a flower-like spacecraft that flies thousands of kilometres away from a telescope, blocking the light from the star, but letting the planet’s light through. NASA is looking for the public’s help to design a starshade that could fly in orbit, allowing ground-based observatories to see planets.
The surface of the Moon experiences severe temperature changes. In the daytime, the surface can heat up to 127 C and cool to -173 C at night. But new observations from NASA’s Lunar Reconnaissance Orbiter show that inside collapsed lava tubes on the Moon, the temperature always remains a comfortable 17 C. You could wear a short-sleeved shirt (inside a pressurized space suit) and wouldn’t need complex and power-hungry heaters and coolers. In the low gravity of Mars, these lava tubes can be hundreds or even thousands of meters tall, allowing room for enormous lunar bases.
If you would like to get a selection of the most important space and astronomy news every week, subscribe to our Weekly Email Newsletter and get magazine-size ad-free news directly from Fraser Cain.
If you prefer the news to be videoed at you, check out our Space Bites playlist on our YouTube channel.
NASA’s upcoming Mars Sample Return mission plan just received a glow-up: it will now carry a pair of twin helicopters, each capable of retrieving samples and delivering them to the ascent vehicle for return to Earth.
The helicopters take the place of a previously planned fetch rover, which has now been ditched from the plan altogether. The fetch rover would have required a second lander, while the helicopters can fit alongside the ascent vehicle, simplifying the mission and reducing its overall cost and complexity.
The decision was announced in a press release earlier this week, which indicated that NASA had finished the system requirements review for the Sample Return mission.
Sample return efforts are already in progress, as the Perseverance Rover is actively collecting samples from scientifically important sites in Jezero Crater on Mars, and has been since early 2021. The original plan was for Perseverance to cache the sample tubes for the fetch rover to collect at a later date. However, Perseverance is still going strong, and NASA expects that it will last long enough to deliver the samples to the ascent vehicle itself. The two helicopters will provide redundant delivery capabilities, should Perseverance fail.
Several recent developments made the updated plan possible. Perseverance’s longevity is one of these. The other is the unadulterated success of Ingenuity, Perseverance’s companion helicopter, which made the first-ever powered flight on Mars back in 2021. It has now lasted over a year longer than its expected operational lifetime, having performed 29 flights in that time. More than just a proof of concept, Ingenuity has demonstrated that powered flight vehicles can be adept, versatile workhorses for a variety of tasks on Mars.
At a media press conference on July 27, Richard Cook, Mars Sample Return Program Manager at the Jet Propulsion Laboratory, indicated that the new helicopters will be distinct from Ingenuity in two ways. The first is that they will feature a set of small wheels rather than landing legs “that allow the helicopters to traverse across the surface on the ground as well as fly…and secondly, each of the helicopters will have a little arm that can reach down and grab onto the…sample tubes.” These capabilities will only be necessary if Perseverance itself cannot deliver the samples, but their presence is a comforting insurance policy in case things go south with the rover.
Jezero Crater on Mars, where Perseverance and Ingenuity are collecting rock samples. They will be joined in 2028 by an ascent vehicle and two new drone helicopters to help return the samples to Earth. Image Credit: NASA/JPL/JHUAPL/MSSS/Brown University
The helicopters, along with the lander carrying the ascent stage, are expected to launch from Earth in 2028 (an orbiter built by the European Space Agency [ESA] will precede them in 2027). After Perseverance and/or the helicopters retrieve the samples, the ascent stage will carry them to Mars orbit and rendezvous with the orbiter, before returning the precious core samples to Earth in 2033.
The changes to the Mars Sample Return Program bear out the recommendations of the Planetary Science Decadal Survey, released back in April 2022. The survey indicated that a successful Mars sample return ought to be the highest scientific priority for NASA’s robotic exploration efforts this decade, but not at the expense of other missions. “Its cost should not be allowed to undermine the long-term programmatic balance of the planetary portfolio,” the survey cautioned. Restructuring the mission to make a second rover and lander unnecessary should help keep costs manageable, while Ingenuity’s success offers compelling evidence that the new plan ought to be feasible.
If all goes well, scientists may soon be spoiled with riches of Martian dust and rock. Alongside NASA’s and ESA’s efforts, a Chinese sample return mission is slated to return Martian soil to Earth by 2031, and a Japanese mission plans to bring samples back from Mars’ largest moon Phobos in 2029.
While in-situ geology performed by rovers like Perseverance and its predecessor Curiosity can tell us a lot about conditions on Mars, there are investigative tools and techniques possible in laboratories back on Earth that no rover can match. Sample return missions will allow scientists to study the minerals in more detail, uncovering the history of the Red Planet and, potentially, its ecosystems (if it ever had any).
The funding for the project is falling into place too. Yesterday, the US Senate released its FY23 draft spending bill, proposing to give NASA the funds it requested for the next year to move the project forward.
According to a new study by an international team of scientists, the JWST will allow astronomers to obtain accurate mass measurements of early galaxies. Using data from James Webb’s Near-Infrared Camera (NIRCam), which was provided through the GLASS-JWST-Early Release Science (GLASS-ERT) program, the team obtained mass estimates from some of the distant galaxies that were many times more accurate than previous measurements. Their findings illustrate how Webb will revolutionize our understanding of how the earliest galaxies in the Universe grew and evolved.
As they indicate in their study, stellar mass is one of the most important physical properties (if not the most) for understanding galaxy formation and evolution. It measures the total amount of stars in a galaxy, which are constantly being added through the conversion of gas and dust into new stars. Therefore, it is the most direct means of tracing a galaxy’s growth. By comparing observations of the oldest galaxies in the Universe (those more than 13 billion light years away), astronomers can study how galaxies evolved.
Unfortunately, obtaining accurate measurements of these early galaxies has been an ongoing problem for astronomers. Typically, astronomers will conduct mass-to-light (M/L) ratio measurements – where the light produced by a galaxy is used to estimate the total mass of stars within it – rather than computing the stellar masses on a source-by-source base. To date, studies conducted by Hubble of the most distant galaxies – like GN-z11, which formed about 13.5 billion years ago – were limited to the Ultraviolet (UV) spectrum.
This is because the light from these ancient galaxies experiences significant redshift by the time it reaches us. This means that as the light travels through spacetime, its wavelength is lengthened due to the expansion of the cosmos, effectively shifting it towards the red end of the spectrum. For galaxies whose redshift value (z) is seven or higher – at a distance of 13.46 light-years or more – much of the light will be shifted to the point where it is only visible in the infrared part of the spectrum. As Santini explained to Universe Today via email:
“The bulk of the stars in galaxies, those that mostly contribute to its stellar mass, emit at optical-near infrared (NIR) wavelengths… [B]y the time the light takes to travels from a distant galaxy to our telescopes, the light emitted by its stars is no more in the optical regime. E.g., for a z=7 galaxy, the light originally emitted at 0.6 micron, reaches our telescope with a wavelength of 4.8 micron. The higher the redshift (i.e. the more distant the galaxy), the stronger is this effect.”
“This implies that we need infrared detectors to measure galaxy stellar masses (the light emitted by the bulk of their stars is out of reach of the Hubble Space Telescope). The only IR telescope we had before the advent of JWST was Spitzer Space Telescope, dismissed a few years ago. However, its 85 cm mirror was not comparable with the 6.5 m mirror of JWST. Most of the distant galaxies were out of reach of Spitzer too: due to its limited sensitivity and angular resolution, they were not detected (or affected by high levels of noise) on its images.
A spectral diagram comparing emitted light from an object to the observed redshifted light. As the Universe expands, it stretches light into lower frequencies or towards the red portion of the spectrum. Credit: NASA/ESA/C. Christian/Z. Levay (STScI)
Moreover, previous surveys were likely to miss a large fraction of intrinsically red galaxies that are dust-rich (which obscures light) and faint in the UV spectrum. Consequently, previous estimates of the cosmic star stellar mass density of the early Universe could be off by a factor of up to six. But thanks to its advanced suite of infrared instruments and unparalleled sensitivity, the JWST is poised to open “a new window” (as Santini put it) into studying the oldest and faintest galaxies in the Universe. As Santini expressed, Webb will enable the first-ever precision measurements of galactic masses out to the furthest distances:
“Due to all these limitations in measuring the stellar mass, a commonly used approach before the launch of JWST was to convert the UV light (which is easily measured by HST) into a stellar mass estimate by assuming an average mass-to-UV light ratio. The mass-light relation was calibrated with the few and uncertain measurements we had, and it was representative only of those galaxy populations that were more easily observed (young, dust-free galaxies). Stellar mass measurements were therefore prone to large uncertainties (both when directly measured, and even more when inferred from the UV light).”
For their study, Santini and his international team of researchers relied on images acquired by NIRCam on June 28th-29th, 2022, as part of its first set of observations. They then measured the stellar mass of 21 distant galaxies (which ranged in redshift from 6.7 to 12.3) by probing their UV emission and redshifted-optical light. As Santini indicated, this allowed them to avoid the large extrapolations and uncertainties of past surveys and increased the accuracy of their mass measurements by a factor of 5 to 10.
“By comparing the stellar masses with the UV light (measured with the bluest NIRCam bands), we found that the M/L ratio is far from approximable with a single, average value,” he said. “It instead spans roughly two orders of magnitude for a given luminosity. From a physical point of view, this finding suggests that the population of early galaxies was largely heterogeneous, with galaxies exhibiting a broad variety of physical conditions.”
The first image taken by the James Webb Space Telescope. Credit: NASA, ESA, CSA, and STScI
These results are part of a growing collection of scientific studies emerging from the earliest James Webb observations, which show just how pivotal the mission will be. In this case, the ability to offer more tightly-constrained estimates of stellar mass in galaxies will greatly assist astronomers engaged in the study of the cosmos on the largest and longest of scales (aka. cosmology). Said Santini:
“The major implication is that previous results regarding the mass growth process in galaxies could be affected by significant systematics. In our work we assess, for example, the level of systematic uncertainty affecting the cosmic stellar mass density. The latter describes the global growth of galaxies in the Universe as a function of time. Its assessment at early epochs is subject to large variance from one work to another. We found that the systematic uncertainty resulting from the assumption of a standard mass-to-light can be as high as a factor of a few, definitely too large compared to the level of precision we aim to reach, and it could at least partly explain the mismatch in the results of the literature.”
So far, Webb has demonstrated its optical capabilities by capturing the clearest and most detailed images of the cosmos, which are already leading to new discoveries. Its spectrometers have obtained spectra from a distant exoplanet, demonstrating how it will assist in the characterization of exoplanet atmospheres and determine if they are truly “habitable.” This latest study shows that it will also play a vital role in determining the characteristics of the earliest galaxies in the Universe, how they have since evolved, and the possible role that Dark Matter and Dark Energy play.
Almost seven years ago (September 14th, 2015), researchers at the Laser Interferometer Gravitational-wave Observatory (LIGO) detected gravitational waves (GWs) for the first time. Their results were shared with the world six months later and earned the discovery team the Noble Prize in Physics the following year. Since then, a total of 90 signals have been observed that were created by binary systems of two black holes, two neutron stars, or one of each. This latter scenario presents some very interesting opportunities for astronomers.
If a merger involves a black hole and neutron star, the event will produce GWs and a serious light display! Using data collected from the three black hole-neutron star mergers we’ve detected so far, a team of astrophysicists from Japan and Germany was able to model the complete process of the collision of a black hole with a neutron star, which included everything from the final orbits of the binary to the merger and post-merger phase. Their results could help inform future surveys that are sensitive enough to study mergers and GW events in much greater detail.
The mergers of compact objects discovered so far by LIGO and Virgo (in O1, O2, and O3a). Credit: LIGO Virgo Collaboration / Frank Elavsky, Aaron Geller / Northwestern
To recap, GWs are mysterious ripples in spacetime originally predicted by Einstein’s General Theory of Relativity. They are created whenever massive objects merge and create tidal disruptions to the very fabric of the Universe, which can be detected thousands of light-years away. To date, only three mergers have been observed involving a binary system consisting of a black hole and a neutron star. During one of these – GW170817, detected on August 17th, 2017 – astronomers detected an electromagnetic counterpart to the GWs it produced.
In the coming years, telescopes and interferometers of greater sensitivity are expected to see much more from these events. Based on the mechanics involved, scientists anticipate that black hole-neutron star mergers will include matter ejected from the system and a tremendous release of radiation (which might include short gamma-ray bursts). For their study, the team modeled what black hole-neutron star mergers would look like to test these predictions.
They selected two different model systems consisting of a rotating black hole and a neutron star, with the black hole set at 5.4 and 8.1 solar masses and the neutron star at 1.35 solar masses. These parameters were selected so that the neutron star was likely to be torn apart by tidal forces. The merger process was simulated using the computer cluster “Sakura” at the MPIGP’s Department of Computational Relativistic Astrophysics. In an MPIGP press release, Department director and co-author Masaru Shibata explained:
“We get insights into a process that lasts one to two seconds – that sounds short, but in fact a lot happens during that time: from the final orbits and the disruption of the neutron star by the tidal forces, the ejection of matter, to the formation of an accretion disk around the nascent black hole, and further ejection of matter in a jet. This high-energy jet is probably also a reason for short gamma-ray bursts, whose origin is still mysterious. The simulation results also indicate that the ejected matter should synthesize heavy elements such as gold and platinum.”
The team also shared the details of their simulation in an animation (shown above) via the Max Planck Institute for Gravitational Physics’ Youtube Channel. On the left side, the simulation shows the density profile as blue and green contours, the magnetic field lines that penetrate the black hole are shown as pink curves, and the matter ejected from the system as cloudy white masses. On the right side, the magnetic field strength of the merger is depicted in magenta, while the field lines appear as light-blue curves.
In the end, their simulations showed that during the merger process, the neutron star is torn apart by tidal forces in a matter of seconds. About 80% of the neutron star’s matter was consumed by the black hole in the first few milliseconds, increasing the black hole’s mass by an additional solar mass. In the following ten milliseconds, the neutron star formed a one-armed spiral structure, part of the matter was ejected from the system while the rest (02.-0.3 solar masses) formed an accretion disk around the black hole.
After the merger was complete, the accretion disk fell into the black hole, causing a focused jet-like stream of electromagnetic radiation and matter. This jet emanates from the poles, similar to what is often seen with Active Galactic Nuclei (AGNs), and could result in a short gamma-ray burst. What was especially astounding was that while the simulations took two months to generate, the simulated merger lasted about two seconds! Said Dr. Kenta Kiuchi, the group leader in Shibata’s department who developed the simulation code:
“Such general relativistic simulations are very time-consuming. That’s why research groups around the world have so far focused only on short simulations. In contrast, an end-to-end simulation, such as the one we have now performed for the first time, provides a self-consistent picture of the entire process for given binary initial conditions that are defined once at the beginning.”
Artist’s illustration of two merging neutron stars. The narrow beams represent the gamma-ray burst, while the rippling spacetime grid indicates gravitational waves. Credit: National Science Foundation/LIGO/Sonoma State University/A. Simonnet
Long-term simulations also allow astronomers to explore the mechanism behind short-lived gamma-ray bursts (GRBs). In addition to being a transient phenomenon, like Fast Radio Bursts (FRBs) that also last for only seconds or milliseconds, GRBs are the most energetic phenomenon in the Universe, and astronomers are keen to investigate them further. Looking ahead, Shibata and his colleagues are working on more complex numerical simulations to model the merger of neutron stars and what results.
The merger of neutron stars is also expected to include an electromagnetic contribution and short-lived gamma-ray bursts. This study serves to illustrate how the study of GW has advanced by leaps and bounds in recent years and how more sensitive observations and keeping pace with improvements in computing and simulations. The result is breakthroughs in our understanding of the Universe that occur at an ever-increasing rate! Who knows what discoveries might be right around the next corner?
