Tracking spacecraft as they traverse deep space isn’t easy. So far, it’s been done manually, with operators of NASA’s Deep Space Network, one of the most capable communication arrays for contacting probes on interplanetary journeys, checking data from each spacecraft to determine where it is in the solar system. As more and more spacecraft start to make those harrowing trips between planets, that system will not be scalable. So engineers and orbital mechanics experts are rushing to solve this problem – and now a team from Politecnico di Milano has developed an effective technique that would be familiar to anyone who has seen an autonomous car.
Visual systems are at the heart of most autonomous vehicles here on Earth, and they are also the heart of the system outlined by Eleonora Andreis and her colleagues. Instead of taking pictures of the surrounding landscape, these visual systems, essentially highly sensitive cameras, take pictures of the light sources surrounding the probe and focus on a specific kind.
Those light sources are known to wander and are also known as planets. Combining their positioning in a visual frame with a precise time calculated on the probe can accurately place where the probe is in the solar system. Importantly, such a calculation can be done with relatively minimal computing power, making it possible to automate the entire process on board, even a Cubesat.
Fraser discusses how to get around in deep space.
This contrasts with more complicated algorithms, such as those that use pulsars or radio signals from ground stations as their basis for navigation. These require many more images (or radio signals) in order to calculate an exact position, thereby requiring more computing power that can reasonably be put onto a Cubesat at their current levels of development.
Using planets to navigate isn’t as simple as it sounds, though, and the recent paper describing this technique points out the different tasks that any such algorithm has to accomplish. Capturing the image is just the start – figuring out what planets are in the image, and therefore, which would be the most useful for navigation, would be the next step. Using that information to calculate trajectories and speeds is up next and requires an excellent orbital mechanics algorithm.
After calculating the current position, trajectory, and speed, the probe must make any course adjustments to ensure it stays on the right track. On Cubesats, this can be as simple as firing off some thrusters. Still, any significant difference between the expected and actual thrust output can result in significant discrepancies in the probe’s eventual location.
Curious Droid also has an explanation of how to get around in space.
Credit – Curious Droid YouTube Channel
To calculate those discrepancies and any other problems that might arise as part of this autonomous control system, the team in Milan implemented a model of how the algorithm would work on a flight from Earth to Mars. Using just the visual-based autonomous navigation system, their model probe calculated its location within 2000 km and its speed to within .5 km/s at the end of its journey. Not bad for a total trip of around 225 million kilometers.
However, implementing a solution in silicon is one thing – implementing it on an actual Cubesate deep space probe is another. The research that resulted in the algorithm is part of an ongoing European Research Council funding program, so there is a chance that the team could receive additional funding to implement their algorithm in hardware. For now, though, it is unclear what the next steps are for the algorithm are. Maybe an enterprising Cubesat designer somewhere can pick it up and run with it – or better yet, let it run itself.
How massive is the Milky Way? It’s an easy question to ask, but a difficult one to answer. Imagine a single cell in your body trying to determine your total mass, and you get an idea of how difficult it can be. Despite the challenges, a new study has calculated an accurate mass of our galaxy, and it’s smaller than we thought.
One way to determine a galaxy’s mass is by looking at what’s known as its rotation curve. Measure the speed of stars in a galaxy versus their distance from the galactic center. The speed at which a star orbits is proportional to the amount of mass within its orbit, so from a galaxy’s rotation curve you can map the function of mass per radius and get a good idea of its total mass. We’ve measured the rotation curves for several nearby galaxies such as Andromeda, so we know the masses of many galaxies quite accurately.
But since we are in the Milky Way itself, we don’t have a great view of stars throughout the galaxy. Toward the center of the galaxy, there is so much gas and dust we can’t even see stars on the far side. So instead we measure the rotation curve using neutral hydrogen, which emits faint light with a wavelength of about 21 centimeters. This isn’t as accurate as stellar measurements, but it has given us a rough idea of our galaxy’s mass. We’ve also looked at the motions of the globular clusters that orbit in the halo of the Milky Way. From these observations, our best estimate of the mass of the Milky Way is about a trillion solar masses, give or take.
The distribution of stars seen by the Gaia surveys. Credit: Data: ESA/Gaia/DPAC, A. Khalatyan(AIP) & StarHorse team; Galaxy map: NASA/JPL-Caltech/R. Hurt
This new study is based on the third data release of the Gaia spacecraft. It contains the positions of more than 1.8 billion stars and the motions of more than 1.5 billion stars. While this is only a fraction of the estimated 100-400 billion stars in our galaxy, it is a large enough number to calculate an accurate rotation curve. Which is exactly what the team did. Their resulting rotation curve is so precise, that the team could identify what’s known as the Keplerian decline. This is the outer region of the Milky Way where stellar speeds start to drop off roughly in accordance with Kepler’s laws since almost all of the galaxy’s mass is closer to the galactic center.
The Keplerian decline allows the team to place a clear upper limit on the mass of the Milky Way. What they found was surprising. The best fit to their data placed the mass at about 200 billion solar masses, which is a fifth of previous estimates. The absolute upper mass limit for the Milky Way is 540 billion, meaning that the Milky Way is at least half as massive as we thought. Given the amount of known regular matter in the galaxy, this means the Milky Way has significantly less dark matter than we thought.
Since time immemorial, humans have gazed up at the stars and wondered if we’re alone in the universe. We have asked if there are other intelligent beings out there in the vastness of the cosmos, also known as extraterrestrial intelligence (ET). Yet, despite our best efforts, we have yet to confirm the existence of ET outside of the Earth. While the search continues, it’s fair to speculate if they might look “human” or humanoid in appearance, or if they could look like something else entirely. Here, we present a general examination and discussion with astrobiologists pertaining to what ET might look like and what environmental parameters (e.g., gravity, atmospheric makeup, stellar activity) might cause them to evolve differently than humans.
“Some body plans may be more optimal than others, in the sense that they may be more streamlined, suitable for locomotion, etc,” Dr. Manasvi Lingam, who is an astrobiologist and Assistant Professor in the Department of Aerospace, Physics, and Space Sciences at the Florida Institute of Technology, tells Universe Today. “However, if extraterrestrial technological species do exist, they might take a number of forms. We cannot rule out humanoid species, but I believe that one could conceive of other body plans. For example, they could have decentralized brains akin to octopuses.”
Science fiction often depicts ET as being humanoid in form: average human height, bipedal, two arms and two legs, and even the head, eyes, and brain in the same location. However, this is likely due to the human actors playing the roles, and while their physical appearance differs from species to species, the “universal” (no pun intended) understanding is the majority of interstellar species are humanoid in appearance. Therefore, as the search for ET continues at a breakneck pace, what could the species of an advanced extraterrestrial technological civilization look like? Could they be humanoid like us, or have another appearance?
“I have no idea!” Dr. Ramses Ramirez, who is an Assistant Professor in the Department of Physics at the University of Central Florida, tells Universe Today. “But it all depends on whether the evolutionary transition from single-cellular – to multi-cellular – to animals (and apes like us!) is a universal one or if it is a unique one-off that is specific to the Earth. If the former, then they may look rather humanoid, with only slight differences (kind of like the culturally pervasive greys). Otherwise, they could literally be anything – from a hive mind to sentient beams of light. It is also possible that a highly technological species may become advanced enough to transcend evolution itself, voluntarily becoming artificial intelligence or robots.”
It is this last part that has sparked the interest of Dr. Seth Shostak, who is a Senior Astronomer at the SETI Institute and published a 2010 paper in Acta Astronautica discussing how SETI should expand their search for ET beyond exoplanets within the star’s habitable zone. In this study, he notes how biological species have limited timescales and an intelligent species who are purely comprised of artificial intelligence could offer far more avenues in terms of their existence, including being possibly immortal or capable of unlimited repair, along with likely not relying on biological environments for survival. In terms of where we should look for such forms of intelligent life, Dr. Shostak said in a 2016 interview that such species could be inhabiting locations in the Universe with lots of energy, such as the center of galaxies of where other plentiful minerals are available that are required for the species to both survive and thrive.
Dr. Shostak tells Universe Today that “any species more advanced than our own will have perfected artificial intelligence. It’s much better for venturing into space anyways. So, most of the sophisticated aliens will be synthetic intelligence.”
But could some ET be land-dwellers like us, or maybe even sea-dwellers? While life on Earth started in the oceans and eventually made its way to land, what if life on other worlds started in the oceans and stayed there? What if there are worlds that are almost entirely absent of the massive continents we see here on Earth? Could a marine environment, specifically with the lack of gravitational pull, have an influence on ET’s appearance?
Dr. Ramirez tells Universe Today, “Marine animals are (on average) able to get bigger and larger than terrestrial animals partially because the buoyancy of water helps free them from the gravitational constraints, but also because the cold sea makes heat loss more efficient. Bigger animals generate more heat, so it is better to be big in the cold ocean.” The notion of varying species types depending on land, sea, or air is also echoed by Dr. Lingam, as he notes his 2023 study exploring (sub)surface ocean worlds.
One possibility could be convergent evolution, which is when similar features appear in various species at different geologic periods or epochs. One example is how different species seem to be evolving crablike bodies over time, known as carcinization. What if intelligent ETs have evolved in such a way, either from their marine-only environment, or a combination of both land and sea life?
Example of possible carcinization, which is a form of convergent evolution, on another world. (Credit: Midjourney Illustration)
If we are to find intelligence on habitable worlds, how could the atmospheric compositions of such planets affect their appearance? On Earth, currently the only known planet with intelligent life, our atmosphere is comprised of approximately 78 percent nitrogen, 21 percent oxygen, and 1 percent argon, along with trace gases of approximately 0.04 percent comprised of ozone, nitrous oxide, methane, and carbon dioxide. Despite oxygen comprising only 21 percent of our atmosphere, most life on Earth requires oxygen to survive, from humans to animals to plants. Therefore, could varying atmospheric compositions also play a role in the evolution of intelligent life on other worlds, and could it play a role in terms of their appearance?
“Yes, atmospheric composition could definitely do that,” Dr. Ramirez tells Universe Today. “For instance, the major transition from small lifeforms and large animals occurred around 540 Myr ago, in an event called the Cambrian explosion. This was when O2 levels rose high enough to support large animals, like us. So, one would expect lifeforms on a planet with very low O2 levels to be rather small.”
Along with our specific atmospheric composition, the Earth’s surface has a gravitational pull measured at 9.81 m/s2, referred to as 1g, and is based on our planet’s mass. As the Apollo astronauts demonstrated on the Moon, the smaller the planetary object, the weaker the gravity, and this is the same for objects larger than Earth, as well. Although humans on Earth have evolved to an average height of 5 feet 9 inches (175 centimeters), could intelligent beings evolve differently on worlds with different levels of gravity? For instance, Mars has a gravitational pull of 3.71 m/s2, which is 38 percent of the Earth. Would this mean if intelligent beings ever lived on Mars, they might have evolved to be taller than humans on Earth?
Dr. Ramirez tells Universe Today that “on an alien planet that is more massive than Earth, with a stronger acceleration due to gravity, one may expect the native life to be shorter and stockier (which thicker muscles, skeletal structure) than what we have on our planet. They’d have to be that way to cope with the stronger gravity. Likewise, on a terrestrial planet with a weaker gravitational pull, the native life would evolve to be taller and lankier on average.”
Another factor that could contribute to ET’s appearance is the star type, with stars transmitting light across what’s known as the electromagnetic spectrum, which consists of gamma rays, X-rays, ultraviolet, visible, microwave, infrared, and radio. Our Sun emits light primarily in visible wavelengths largely due to its temperature, and as such, the human eye has evolved to see objects in visible light. However, what if ET evolved on a world orbiting a star that emits light in other wavelengths?
Dr. Ramirez tells Universe Today, “Different stars put out energy at different wavelengths, which may affect the types of plants that could photosynthesize on an alien planet (if photosynthesis is still possible under those conditions!). So, perhaps differences in the nature of starlight a planet receives could potentially change how evolution proceeds on a planet.”
Dr. Lingam echoes these sentiments as he tells Universe Today that “the planet’s star could affect the wavelengths at which they see (e.g., species on planets around M-dwarfs might see primarily in the infrared).” Also known as red dwarf stars, M-dwarfs are smaller than our Sun and the smallest known star type, capable of being as small as 0.08 the mass of our own Sun. As a result, they are much cooler and give off much redder light, as noted by their name, which makes them harder to detect.
As the search for ET continues, we will also continue to wonder how they might have evolved in appearance, especially if the environmental parameters are different than our own. What might ET look like, and would they resemble humans, or something else? Only time will tell, and this is why we science!
Exoplanet studies have come a long way in a short time! To date, 5,523 exoplanets have been confirmed in 4,117 systems, with another 9,867 candidates awaiting confirmation. With all these planets available for study, exoplanet researchers have been shifting their focus from detection to characterization – i.e., looking for potential signs of life and biological activity (biosignatures). Some major breakthroughs are expected in the coming years, thanks in part to next-generation observatories like NASA’s James Webb and Nancy Grace Roman Space Telescope and the ESA’s PLAnetary Transits and Oscillations of stars (PLATO) mission.
ESO’s Very Large Telescope (VLT) has captured an unprecedented series of images showing the passage of the exoplanet Beta Pictoris b around its parent star. Credit: ESO
As mentioned above, exoplanet research has been moving into characterization thanks to improvements in instrumentation and machine learning. With such a large sample of planets, scientists are now characterizing individual planet atmospheres and can draw statistical conclusions on large samples. These improvements are also leading to a transition in terms of methods, where exoplanets are being studied using Direct Imaging more than ever before. This method consists of detecting exoplanets by imaging the light reflected from their atmospheres and surfaces.
This stands in contrast to indirect methods like Transit Photometry or Doppler Spectroscopy (aka. the Transit Method and Radial Velocity Method), which have been responsible for the majority of exoplanet detections and confirmations so far. A major benefit of Direct Imaging is that astronomers can examine the reflected light using spectrometers to determine the chemical composition of an exoplanet’s atmosphere. Said Dr. Vigan via email:
“Detection of these objects and measuring accurate spectra is still quite challenging because they are typically at extremely small angular separation from their host star and with a huge difference in brightness. A classical analogy is that of trying to image a candle located 1 m apart from a lighthouse when you observe from 700 km away! In the field of direct imaging, the combination of high-contrast imaging, which enables the detection of these planets, with high-resolution spectroscopy is a really hot topic right now. This is exactly what HiRISE enables on the VLT.”
The HiRISE instrument is designed to characterize extrasolar giant planets (EGPs) in the infrared H band, an atmospheric transmission window astronomers use to measure the absorption by water vapor, volcanic activity, and other atmospheric phenomena. It combines the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) imager with the recently upgraded high-resolution CRyogenic high-resolution InfraRed Echelle Spectrograph (CRIRES) using single-mode optic fibers. The addition of this instrument will greatly enhance the VLT’s imaging capabilities, which are currently limited in terms of spectral resolution relative to other observatories.
The SPHERE (Spectro-Polarimetric High-contrast Exoplanet REsearch) instrument is installed on the ESO Very Large Telescope and will assist researchers by directly imaging exoplanets larger than Jupiter. Credit: ESO
This is particularly the case for SPHERE, said Dr. Vigan, which is dedicated to finding exoplanets via Direct Imaging but has a maximum resolution of just ~70. “Other instruments like SINFONI (retired) or now ERIS provide higher resolutions, but they are not really optimized for exoplanet imaging, and GRAVITY provided some great results with interferometry, but except in a few cases, it is limited to a resolution of a few hundred,” he said. “By contrast, HiRISE enables a resolution of 100,000! This opens the door to much more detailed spectral characterization and to measuring dynamical parameters such as the speed at which these planets orbit around their star and how fast they spin.”
In addition to atmospheric characterization, these measurements will help astronomers investigate EGP formation, composition, and evolution, addressing some significant mysteries and helping astronomers refine their models for solar system formation. Based on the first light collected using the new HiRISE instrument, the team demonstrated how its incorporation into the VLT has led to improved astrometry, temporal stability, optical aberrations, and transmission. Moreover, their paper demonstrates how existing instruments and observatories can be upgraded to provide high-contrast imaging or high-dispersion spectroscopy by coupling them using optical fibers.
This offers a cost-effective alternative to creating entirely new facilities from the ground up, which is the case with the ELT, GMT, and TMT. As these examples have demonstrated, the creation of new facilities is expensive, subject to delays, and can generate controversy when it comes to where facilities are being built (sensitive ecosystems, protected environments, Indigenous land, etc.). As Dr. Vigan explained:
“Designing, manufacturing, testing, and installing a brand new instrument on a large ground-based telescope is both long and costly: 10 years and ~20 million euros (including 10 million in hardware) for the SPHERE instrument on the VLT. This is even without taking into account that you need an available focus on the telescope for the new instrument. The advantage of coupling existing instruments is that you can go much faster and much cheaper while still making a great instrument that benefits from existing ones.”
This image, taken in late June 2023, shows a night view of the construction site of ESO’s Extremely Large Telescope at Cerro Armazones, in Chile’s Atacama Desert. Credit: ESO.
In the case of HiRISE, he added, it took about five years of development and cost around €900,000 to build, including another €200,000 to pay for the hardware, for a total of €1.1 million ($1.16 million). In contrast, the European Southern Observatory placed the cost of building the ELT at $1.5 billion in 2020 (€1.42 billion). This was after the ESO approved a budget increase of 10%, and the facility will not be completed for several more years. Meanwhile, Dr. Vigan and the ESO hope to commence observations with the upgraded VLT by November, which will serve as a pathfinder for other observatories:
“Hopefully, HiRISE will pave the way for future instruments, for exemple on the extremely large telescopes (ELTs). We have learned a lot while designing the instrument and we will now investigate its limits. The European ELT built by ESO will at some point have an exoplanet imaging instrument aiming at the detection of Earth analogs around nearby stars. It’s already foreseen that the instrument will include a high-resolution spectroscopy mode to help boost the detection. Everything we have done and learned with HiRISE will be a great starting point.”
There may come a day when we grow weary of JWST images. But it’s not today. Today, we can lose ourselves in the space telescope’s engrossing image of NGC 6822, also called Barnard’s Galaxy.
Barnard’s Galaxy was discovered by the accomplished American astronomer E. E. Barnard in 1884. He spotted it with a 6-inch refractor telescope. It’s the closest galaxy to the Milky Way that isn’t a satellite galaxy, and it’s quite similar to our neighbour, the Small Magellanic Cloud. It’s a dwarf irregular galaxy about 7,000 light-years across and about 1.6 million light-years away.
The JWST captured this image with its NIRCam instrument, and it shows the galaxy in deep detail. Dust and gas are pervasive in the galaxy, but the JWST has the power to see right through it with its infrared instruments. One of the reasons JWST was built was to peer through gas and dust and see what’s going on behind it.
Zooming in reveals the JWST’s power. Here and there, distant galaxies pop into view well beyond Barnard’s Galaxy.
Zooming into almost any part of the image reveals distant galaxies. In this portion, a trio of galaxies lines up diagonally. Image Credit: ESA/Webb, NASA & CSA, M. Meixner
Webb doesn’t take colour pictures, so when it sends data back to Earth, it’s all black and white. But it does an excellent job of capturing photons, and the images are processed into colour for our enjoyment and for scientific detail. In the image, the brightest stars are blue and cyan, while the fainter stars are warm-coloured.
This part of the image highlights one of NGC 6822’s star clusters in the upper center. A smaller cluster is in the lower left. Image Credit: ESA/Webb, NASA & CSA, M. Meixner
The little bit of gas and dust visible in the image is also a testament to the JWST’s power. Gas and dust pervade the galaxy, but in this image, only a small amount is visible.
Gas and dust appear only as red wisps in this image, thanks to the JWST’s powerful instruments. Image Credit: ESA/Webb, NASA & CSA, M. Meixner
The JWST team published another image of NGC 6822 last summer. That image was captured with both the NIRcam and MIRI instruments. It highlights the space telescope’s power and the flexibility it gains from its multiple instruments and filters.
The JWST captured this image of NGC 6822 with NIRCam and MIRI. This image captured more of the galaxy’s dust and gas, and it shows how powerful and flexible the telescope is. Image Credit: ESA/Webb, NASA & CSA, M. Meixner
Barnard’s Galaxy is a bit of a puzzle. Its oldest stars are 10 billion years old, and some research suggests they’re even older. But most of the stars in NGC 6822 formed in the last 3 to 5 billion years. It’s been isolated for most of its life, but some research shows it came close enough to the Milky Way in the last 3 or 4 billion years to trigger star formation. The star formation rate may have accelerated even more in the last 100 to 200 million years.
Overall, the stars in NGC 6822 have low metallicity, meaning they’re mostly made of hydrogen and helium and almost nothing heavier. All stars in the early Universe had low metallicity because elements heavier than hydrogen and helium can only be forged in stars. When the stars die, the metals are spread back out into the Universe, to eventually form new stars with higher metallicity. Astronomers are greatly interested in contemporary objects with low metallicity, like NGC 6822. Studying it helps astronomers gain insight into the cycle of interstellar gas as it’s taken up in star formation and then expelled back into the interstellar medium. It also helps them understand how stars evolve.
Prior to the JWST’s mission, this was the type of image we had of NGC 6822. The image on the left is from the 2.2-meter MPG/ESO telescope, with star-forming regions in yellow boxes. On the right are ALMA images of each region. Needless to say, there’s a dramatic difference between these images and the JWST’s images. Image Credit: By ESO, ALMA (ESO/NAOJ/NRAO)/A. Schruba, VLA (NRAO)/Y. Bagetakos/Little THINGS – https://ift.tt/zkNuSUG, CC BY 4.0, https://ift.tt/s9fGlU3
NGC 6822 has a place in astronomical history. It was the first object that astronomers were certain was outside of the Milky Way. We take that for granted now, but at the time, there was a raging debate about the size of the Universe, and astronomers weren’t certain there were any objects outside the Milky Way.
Famous American astronomer Edwin Hubble studied it extensively and published a paper on it in the Astrophysical Journal in 1925. “NGC 6822 is a faint irregular cluster of stars with several small nebulae involved,” Hubble wrote. “NGC 6822 lies far outside the limits of the galactic system.”
This image was captured by Edwin Hubble in 1925 with the 100-inch reflector at Mount Wilson Observatory. It’s a three-and-a-half hour exposure. Some of the labelled parts are diffuse nebula. Image Credit: From “NGC 6822, a remote stellar system,” by Edwin Hubble, Astrophysical Journal, 1925.
The JWST was a long time coming. It’s development was a highly-contested affair sometimes, and Congress threatened to cancel it. But it stands as the pinnacle of astronomical achievement, and now that it’s operating, it’s expanding and deepening our understanding of the cosmos, and of nature.
With gorgeous images like this one of Barnard’s Galaxy, we’re all along for the ride.
The upcoming solar eclipses and the current high sunspot activity means it’s a great time to observe the Sun. Eclipses also mean that large groups of people will be together to view these events. However, rule #1 for astronomy is to never look at the Sun with unprotected eyes, especially with a telescope or binoculars.
So, how can you safely show the changing Sun to a large group of people without having them line up forever to look through a telescope with a solar filter, or having a lot of equipment?
A group of astronomers have a solution: Get a disco ball.
If you set up a disco ball in a sunlit room, they say, it will project tiny images of the Sun onto the walls, similar to how a pinhole camera works. But a disco ball can show the state of a solar eclipse or the presence of sunspots, and allow dozens of people to see it simultaneously.
“Commercial disco balls provide a safe, effective and instructive way of observing the Sun,” a group of astronomers from several universities wrote in a pre-print paper published on arXiv. The paper explores the optics of solar projections with disco balls, and the researchers found that while sunspot observations are challenging, the solar disk and its changes during eclipses are “easy and fun to observe.”
They also explore the disco ball’s potential for observing the Moon and other bright astronomical phenomena.
The astronomers note that simple pinholes have been used to observe the Sun since antiquity, along with other commonly used tools for projecting eclipses, such as pinhole projectors, colanders, or tree canopies.
Tiny ‘eclipses’ showing through the holes of a colander during the solar eclipse in 2017. Credit: Nancy Atkinson.
Unlike more traditional solar projection tools like pinhole projectors and colanders, the disco ball spreads its solar images across a room, producing recognizable solar disks from distances of about 2 meters and onwards, the researchers said.
“But a disco ball is able to function for large crowds because it does not merely work on the area where it casts its shadow, but across the entire illuminated hemisphere, which can project solar images across an entire room or courtyard,” they wrote.
A disco ball projector during the partial solar eclipse of 25 October 2022 in Potsdam, Germany. An enlarged solar image is shown in the lower right corner.Via Cumming et al.
During March-May 2023, the astronomers tested out a portable disco ball as part of a permanent exhibition at a university observatory in Potsdam, Germany, with visitors in groups of all ages. When illuminated by the Sun, the ball was popular with visitors, “in particular, children enjoyed the opportunity of spinning the ball and watching the reflected images move across the walls,” they said.
The researchers argue the disco ball is more accessible tool for larger or socially distanced groups. It is also possible to observe large sunspots with a disco ball with small enough mirror segments. They also tested out observing the Moon and its phases, but that “requires a darker environment than we have yet been able to achieve.”
A sunspot group observed on 2023 May 27 observed with a disco ball projector (left) and observed with the SDO/HMI Satellite (right; Scherrer 2011). Via Cumming et al.
The list of advantages of a disco ball goes on: “Additionally, it does not need to be pointed or moved to project the Sun, as new segments get illuminated as the Sun moves out of the older ones. This means that it is enough to simply place a disco ball close to a window in order to fill a large part of the space with solar projections. In fact, the disco ball encourages a crowd to disperse, as they walk towards the walls to look at the projected images.”
With the annular eclipse coming up on October 14, 2023 and a total solar eclipse on April 8, 2024, the astronomers said a disco ball is a safe way for larger groups of people to view these events and share them together.
“We believe that the disco ball is a versatile and engaging tool for educational purposes,” the researchers wrote, “deserving wider use both for classroom demonstrations and for public events.”
Plus, there are also some unique disco balls out there, like this one, available at Amazon, to make it even more fun:
If we could wind the clock back billions of years, we’d see our Solar System the way it used to be. Planetesimals and other rocky bodies were constantly colliding with each other, and new objects would coalesce out of the debris. Asteroids rained down on the planets and their moons. The gas giants were migrating and contributing to the chaos by destroying gravitational relationships and creating new ones. Even moons and moonlets would’ve been part of the cascade of collisions and impacts.
When nature crams enough objects into a small enough space, it breeds collisions. A new study says that’s what happened at Saturn and created the planet’s dramatic rings.
The research is “A Recent Impact Origin of Saturn’s Rings and Mid-sized Moons,” and it’s published in The Astrophysical Journal.” The lead author is Luis Todorow, a Research Fellow at the School of Physics and Astronomy at the University of Glasgow.
Saturn’s rings are so iconic that even schoolchildren can identify them. Astronomers have puzzled over them for a long time, trying to figure out how they formed and when. We know they’re mostly made of ice, but a consensus for their formation has been hard to reach.
This study, conducted by NASA and its partners, says a collision between two icy moons is responsible, and the debris is still circling the planet.
We don’t have to wind the clock back too far to find the impact the research identifies. It occurred only a few hundred million years ago, maybe even more recently than that. The research team says that it was triggered by “resonant instabilities in a previous satellite system.”
The research is based on detailed simulations of Saturn and its system of moons (it has 146 confirmed satellites) and rings.
NASA’s Cassini mission laid the groundwork for this research. The spacecraft spent more than ten years in the Saturn system. One of its main discoveries was that the gas giant’s rings and moons are not very old in astronomical terms. The larger ones are probably old, and their cratered surfaces are a clue to their ages. But some of the planet’s smaller moons are likely much younger.
An annotated picture of Saturn’s many moons captured by the Cassini spacecraft. Image Credit: By Kevin Gill from Los Angeles, CA, United States – Saturn – September 9, 2007 – Annotated, CC BY 2.0, https://ift.tt/zMIZkxq
A moon’s distance from its planet plays a role in this. The gravitational struggle between a planet and its moon tends to drive moons away. Earth’s Moon is receding a tiny yet measurable amount each year. Some research shows that if the moons nearest to Saturn’s rings were old, they would’ve been pushed away by now. Since they’re still there, they must be young.
But it’s not that cut and dry because the smaller inner moons also have cratered surfaces.
Saturn’s moon Mimas is covered in craters, including the dramatic Herschel crater that gives the moon its “Death Star” nickname. But it’s close to Saturn. What’s going on? Image credit: NASA/JPL/SSI
So Saturn is still mysterious.
Adding to the intrigue is our fascination with icy moons. Saturn’s moon Enceladus, as well as other moons like Jupiter’s Europa, contain vast oceans underneath icy shells. They’re prime targets in the search for life, so their histories have elevated importance. If two of them collided to form Saturn’s rings, what does it all mean?
“There’s so much we still don’t know about the Saturn system, including its moons that host environments that might be suitable for life,” said Jacob Kegerreis, a research scientist at NASA’s Ames Research Center and one of the paper’s co-authors. “So, it’s exciting to use big simulations like these to explore in detail how they could have evolved.”
There’s abundant research into Saturn’s rings. One study in 2022 proposed that there used to be an additional moon between Iapetus and Titan. The moon’s presence helped the Saturn system form a resonance with Neptune, and that drove Saturn’s obliquity. As the system became more destabilized, the moon grazed Saturn, the planet’s powerful gravity tore it to pieces, and the debris formed the icy rings while also kicking Saturn out of the resonance. This evidence supports a young age for Saturn’s rings, perhaps only 100 million years old.
This new research is in the same vein, but instead of a single moon getting torn apart by Saturn, two moons experience a high-speed impact that destroys them both.
An artist’s conception of two bodies smacking into each other. A collision like this could’ve formed Saturn’s rings. Credit: NASA/JPL-Caltech
The researchers performed simulations with the powerful Distributed Research using the Advanced Computing (DiRAC) supercomputing facility at Durham University’s Institute of Computational Cosmology in the UK. It’s dedicated to particle physics, astronomy, and cosmology. The team used the powerful computer to model collisions between precursor moons in the Saturn system.
The Roche Limit governs a critical part of the relationship between a planet and its moons. It’s the minimum distance a moon can approach its planet without being torn apart by the planet’s gravity. Saturn’s rings are inside the Roche Limit, and beyond that limit, planets can form from debris. So debris beyond the Roche Limit wouldn’t last long because the material would likely coalesce into new moons.
That’s basically what happened, according to this research. An ancient collision between two moons created a shower of debris inside Saturn’s Roche Limit. The massive planet’s powerful gravity prevented the debris from forming a new moon, so the debris formed into rings. The team performed almost 200 simulated collisions, each one with different masses, velocities, and angles of impact. In a wide range of scenarios, material settled into rings around Saturn, inside its Roche Limit.
“This scenario naturally leads to ice-rich rings,” said Vincent Eke, Associate Professor in the Department of Physics/Institute for Computational Cosmology at Durham University and a co-author on the paper. “When the icy progenitor moons smash into one another, the rock in the cores of the colliding bodies is dispersed less widely than the overlying ice.”
This is a strong point of the study. Icy moons still have rocky cores, and other scenarios can’t explain why there would be almost no rock in Saturn’s rings. The simulations show that only a negligible amount of rock from the collisions finds its way inside the Roche Limit, which matches the icy nature of Saturn’s rings.
This would’ve been a messy process that played out over time. The study shows there would’ve been a lot of debris from the collision and that it would’ve impacted other moons, which may have led to collisional cascades.
“Furthermore, more than a Mimas mass of material—and even more than an Enceladus mass in some cases—is placed onto crossing orbits with present-day Mimas, Enceladus, and Tethys (and Titan), facilitating the possibility of a collisional cascade to further distribute material across the system,” the paper states.
It would’ve taken a long time for things to settle down. But what caused it?
Everything in the Universe is in motion, and every object exerts a gravitational force on other objects. In our Solar System, the Sun’s mass dominates. So even though Saturn is almost 1.5 billion km (932 million mi) away from the Sun, the star’s gravity still affects things.
The Sun’s gravitational input at that distance is small, but it can build up in orbital resonances. Eventually, things can become destabilized, and Moons are driven from their circular orbits into elongated and tilted orbits. Saturn is rich in moons, so it’s only a matter of time until their orbits cross, and that causes a high-speed impact and the resulting cloud of mostly icy debris.
Saturn’s moon Rhea has something to tell us about this collision scenario. It’s Saturn’s second-largest moon, and its orbit is significant. It’s just beyond the point where these orbital resonances would affect it. Since moons tend to drift away from their planets, Rhea should’ve crossed this threshold of resonance eviction recently. That would’ve messed with its orbit, but its orbit is circular and flat. This supports the moon’s recent formation.
Saturn’s moon Rhea, as imaged by the Cassini-Huygens space probe. Credit: NASA/JPL-Caltech
But if Rhea formed recently, it clouds some of our thinking about Saturn’s icy moon Enceladus and its potential for life. How old is Enceladus? Did it form only a few hundred million years ago, maybe even more recently? If so, that’s not enough time for life to appear, as far as we understand it.
Saturn and its rings and moons are a fascinating system. There are so many factors at work that scientists struggle to come up with definitive explanations. The Cassini mission showed us that the rings are likely much younger than thought, somewhere between 10 million and 100 million years old. These simulations support that idea, though they’re not conclusive.
“We conclude that the impact of two destabilized icy moons is a promising scenario for the recent formation or rejuvenation of Saturn’s rings and reaccretion of mid-sized moons,” the researchers say in their conclusion.
But more research is needed before we can rule out other scenarios.
“Future work on the long-term evolution of the orbit-crossing debris, combined with further and more detailed modelling of collisions between both icy moons and smaller fragments, will help to constrain the implications of this scenario for Saturn’s rings, its moons, their craters, and other surface environments,” they write.
In 1960, while preparing for the first meeting on the Search for Extraterrestrial Intelligence (SETI), legendary astronomer and SETI pioneer Dr. Frank Drake unveiled his probabilistic equation for estimating the number of possible civilizations in our galaxy – aka. The Drake Equation. A key parameter in this equation was ne, the number of planets in our galaxy capable of supporting life – aka. “habitable.” At the time, astronomers were not yet certain other stars had systems of planets. But thanks to missions like Kepler, 5523 exoplanets have been confirmed, and another 9,867 await confirmation!
Based on this data, astronomers have produced various estimates for the number of habitable planets in our galaxy – at least 100 billion, according to one estimate! In a recent study, Professor Piero Madau introduced a mathematical framework for calculating the population of habitable planets within 100 parsecs (326 light-years) of our Sun. Assuming Earth and the Solar System are representative of the norm, Madau calculated that this volume of space could contain as much as 11,000 Earth-sized terrestrial (aka. rocky) exoplanets that orbit within their stars’ habitable zones (HZs).
Prof. Madua is a professor of astronomy and astrophysics at the University of California, Santa Cruz (UCSC). Central to his study is the Copernican Principle, named for famed Polish astronomer Nicolaus Copernicus, inventor of the heliocentric model. Also known as the Cosmological Principle (or Mediocrity Principle), the principle states that neither humans nor Earth are not in a privileged position to observe the Universe. In short, what we see when we look upon the Solar System and out into the cosmos is representative of the whole.
For his study, Madua considered how time-dependent factors have played a vital role in the emergence of life in our Universe. This includes the star formation history of our galaxy, the enrichment of the interstellar medium (ISM) by heavy elements (forged in the interior of the first population of stars), the formation of planets, and the distribution of water and organic molecules between planets. As Madua explained to Universe Today, the central role of time and age are not explicitly stressed in the Drake Equation:
“The Drake equation amounts to a useful pedagogical summary of the factors (probabilities) that may affect the likelihood of detecting life-bearing worlds – and eventually technologically advanced extraterrestrial civilizations – around us today. But that likelihood and those factors depend, among other quantities, on the star formation and chemical enrichment history of the local Galactic disk, as well as on the timeline of the emergence of simple microbial and eventually complex life.”
Earth is a relative newcomer to our galaxy, having formed with our Sun roughly 4.5 billion years ago (making it less than 33% the age of the Universe). Life, meanwhile, took about 500 million years to emerge from the primordial conditions that existed on Earth ca. 4 billion years ago. About 500 million years after that, photosynthesis emerged in the form of single-celled organisms that metabolized carbon dioxide and produced oxygen gas as a byproduct. This gradually altered the chemical makeup of our atmosphere, triggering the Great Oxidation Event about 2.4 billion years ago and the eventual rise of complex life forms.
A long and complex process of chemical and biological evolution followed, eventually leading to conditions suitable for complex life and the emergence of all known species. Given the importance of these time-dependent steps, Madua argues that the Drake Equation is only part of the story. Looking beyond it, he created a mathematical framework to estimate when “temperate terrestrial planets” (TTPs) formed in our corner of the galaxy and microbial life could have emerged.
The Drake Equation, a mathematical formula for the probability of finding life or advanced civilizations in the Universe. Credit: University of Rochester
This framework allows astronomers to determine which potential target stars (based on mass, age, and metallicity) may be optimal candidates in the search for atmospheric biosignatures. As Madua described it, his approach consists of considering the local population of long-lived stars, exoplanets, and TTPs as a series of mathematical equations, which can be solved numerically as a function of time:
“These equations describe the changing rates of star, metal, giant, and rocky planets, and habitable world formation over the history of the solar neighborhood, the locale where more detailed calculations are justified by an avalanche of new data from space-based and ground-based facilities and the target of current and next-generation stellar and planetary surveys. The equations are statistical in nature, i.e. they do not describe the birth and evolution of individual planetary systems but rather the changing (over time) population (by number) of TTPs within 100 parsecs of the Sun.”
Ultimately, Madua’s analysis showed that within 100 parsecs of the Sun, there may be as many as 10,000 rocky planets orbiting with their star’s HZs. He also found that the formation of TTPs near our Solar System was likely episodic, starting with a burst of star formation roughly 10-11 billion years ago, followed by another event that peaked about 5 billion years ago that produced the Solar System. Another interesting takeaway from Madua’s mathematical framework indicates that most TTPs within 100 parsecs are likely older than the Solar System, confirming that we are a relative latecomer to the party!
Equally interesting are the implications this study could have on the search for extraterrestrial life. Using the generally accepted timeline of the emergence of life on Earth (abiogenesis) and applying a conservative estimate of the prevalence of life on other planets – the fl parameter of the Drake Equation – Madua’s framework also indicated how far away the closest exoplanet harboring life could be:
“So, if microbial life arose as soon as it did on Earth in more than 1% of TTPs (and that is a big if), then one expects the closest, life-harboring Earth-like planet to be less than 20 pc away [65 light-years],” he said. “This may be cause for some cautious optimism in the search for habitability markers and biosignatures by the next generation of large ground-based facilities and instrumentation. Needless to say, biosignatures are going to be extremely challenging to detect. And it is also possible that life may be so rare that there are no biosignatures within a kpc or more for us to detect.”
This artist’s impression shows the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. Credit: ESO/M. Kornmesser
Of course, there are no guarantees that any TTPs near our Solar System could support life. The causes and commonality of abiogenesis is one of the least-understood scientific pursuits, mainly because it is so data-poor. Armed with only one example (Earth and terrestrial organisms), scientists cannot confidently say what combination of conditions is necessary for life to emerge. Madua also stresses that (like the Drake Equation), his approach is statistical in nature. Nevertheless, his work could have significant implications for astrobiology in the near future.
Using our Solar System as a guide, along with many other parameters for which there are volumes of data (i.e., star formation, mass, size, metallicity, and the number of nearby exoplanets orbiting within a star’s HZ), scientists will be able to prioritize star systems for investigation using next-generation telescopes. Said Madua:
“The yield and characterization of Earth-like planets will be a primary science metric for future space-based flagship missions. With the fast-approaching opportunity to make a search for habitable environments and life on exoplanets comes the real challenge of actually designing an optimal observational strategy. Detailed spectral studies of a few exoplanet atmospheres must be accompanied by population studies designed to reveal trends in planet properties and statistical studies that will allow us to evaluate the likelihood of biosignature detectability.”
On Sunday, September 23rd, the Sample Retrieval Capsule (SRC) from NASA’s OSIRIS-REx mission landed in the Utah desert. Shortly thereafter, recovery teams arrived in helicopters, inspected and secured the samples, and flew them to the Utah Test and Training Range (UTTR). On Monday, the sample canister was transferred to the Astromaterials Research and Exploration Science Directorate (ARES) in Houston, Texas. Yesterday, on Tuesday, September 26th, NASA announced that the process of unsealing and removing the samples from the canister had begun with the removal of the initial lid.
Housed at NASA’s Johnson Space Center, ARES holds the world’s largest collection of samples returned from space – aka. “astromaterials.” In anticipation of OSIRIS-REx’s sample return, this facility was augmented with a special clean room built exclusively for the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission. This clean room includes custom “glove boxes” built to assist with the disassembly process (shown above). For months, curation experts have been rehearsing the intricate process of removing the samples from their container.
The first step, performed yesterday, involved the removal of the aluminum lid that protects the Touch and Go Sample Acquisition Mechanism (TAGSAM) head. This component was part of the robotic arm used by OSIRIS-REx to collect rocks and dust from the surface of asteroid Bennu in October 2020. The next step will consist of separating the TAGSAM from the canister and inserting it into a sealed transfer container that will preserve it in a nitrogen environment for about two hours. This container will allow the curation team enough time to insert the TAGSAM into another unique glovebox.
These steps speed up the disassembly process while ensuring that the samples are not contaminated by contact with lab hardware or Earth’s environment. According to NASA Shaneequa Vereen, a Public Affairs Officer and Live Mission Commentator at NASA, NASA scientists reportedly found “black dust and debris on the avionics decks of the canister” once the lid was removed. While no indication has been provided, this dust and debris is likely part of the Bennu sample that escaped from the TAGSAM head during retrieval or its transport back to Earth.
The final step, the removal of the sample, will be part of a special live broadcast event on October 11th at 11 AM EDT (08:00 AM PDT), which will be streamed on NASA Live and the agency’s website. Stay tuned for more, or check out the OSIRIS-REx mission page at NASA Blods for regular updates.
Earth was once entirely molten. Planetary scientists call this phase in a planet’s evolution a magma ocean, and Earth may have had more than one magma ocean phase. Earth cooled and, over 4.5 billion years, became the vibrant, life-supporting world it is today.
Can the same thing happen to exo-lava worlds? Can studying them shed light on Earth’s transition?
Planet-hunters like the Kepler Spacecraft and TESS have found thousands of worlds around other stars. Many of these worlds orbit their stars very closely, so close that they’re heated to extreme temperatures. A lot of these planets are gas giants, but a significant number are rocky, and the extreme heat keeps them molten, or at least partially molten. At least half of these super-heated rocky worlds are capable of maintaining magma on their surfaces.
There’s nothing like a lava world in our Solar System. The closest is Jupiter’s moon Io. But it’s volcanically active, which isn’t the same as a magma ocean. Studying lava worlds gives scientists a glimpse into Earth’s molten past, and luckily, they’re not hard to find.
A new study looked at hot rocky super-Earths, how their magma oceans affect our observations, and how they also influence their evolutionary paths.
“When planets initially form, particularly for rocky terrestrial planets, they go through a magma ocean stage as they’re cooling down,” said Boley. “So lava worlds can give us some insight into what may have happened in the evolution of nearly any terrestrial planet.”
“Being able to trap a lot of volatile elements within their mantles could have greater implications for habitability.”
Kiersten Boley, lead author, Ohio State University.
The team used exoplanet modelling software to simulate Super-Earths that orbit their stars very closely. These planets are called ultra-short period (USP) planets. They simulated multiple evolutionary pathways for a planet similar to Earth but with surface temperatures between 2600 and 3860 F (1426 and 2126 C.) Within this range, a planet’s solid mantle would melt into magma depending largely on its composition.
Their work produced three classes of magma oceans, each with different mantle structures: a mantle magma ocean, a surface magma ocean, and one consisting of a surface magma ocean, a solid rock layer, and a basal magma ocean.
This figure from the study shows the three types of mantle structures in the simulations. The researchers found that the mantle may be a mantle magma ocean, a surface magma ocean and solid rock layer, or a MOSMO structure (i.e., Surface Magma Ocean (MO)–Solid Rock Layer (S)–Basal Magma Ocean (MO)). Image Credit: Boley et al. 2023.
The research shows that mantle magma ocean planets are less common than the other two, but not by much. But when it comes to evolutionary pathways that might lead to habitable planets, it’s the planet’s composition that’s more important than its mantle structure. In lava worlds without atmospheres, the composition dictates how effective the magma is at trapping volatiles. That’s critical when it comes to life as we know it.
For a planet to one day express life, it needs an atmosphere with critical components like carbon and oxygen. Earth life is based on carbon, and oxygen is key to complex life here on Earth. So a magma planet with ample carbon and oxygen in its magma could eventually off-gas these critical materials into a planet’s burgeoning atmosphere if it held onto one.
Water, as we all know, is also critical to life, and some of the simulated planets had massive reserves of water. According to the study, a basal magma planet four times more massive than Earth—a Super-Earth—can trap over 130 times more water than in all of Earth’s oceans. The same planet can also trap 1,000 times more carbon than there is in Earth’s crust and mantle.
“When we’re talking about the evolution of a planet and its potential to have different elements that you would need to support life, being able to trap a lot of volatile elements within their mantles could have greater implications for habitability,” said Boley.
The study also looks at planet density and what it can tell us from a distance when we observe lava worlds. The magma and the volatiles determine a planet’s density, and temperature plays a large role in the volatile content.
This figure from the research shows the bulk density differences between modelled planets at two different surface temperatures. The main point is that with greater mass, the density difference between a magma ocean and an equivalent-mass solid planet decreases. That’s largely due to higher pressure and greater magma compression. “Broadly speaking, all models find that low-mass planets exhibit the largest fractional inflation due to magma, compared to higher-mass planets,” the authors explain. Image Credit: Boley et al. 2023.
To understand the nature of magma planets and how they might evolve, astronomers need to know how magma oceans affect the properties they can observe from a distance. But the study actually shows that when it comes to lava worlds, measuring their densities might not be the best way to understand them. Not, at least, when they’re being compared to solid exoplanets. That’s because the magma ocean doesn’t have a pronounced effect on density. In fact, according to this research, the presence of a magma ocean can’t explain low-density magma ocean planets.
The researchers came to other conclusions about magma oceans. For a planet of a given mass, there’s a range of temperatures in which a planet can have a basal magma ocean that could hold a lot of volatiles. And in their models, they injected H2O and CO2 into the magma of some planets and found that it made very little difference in the density.
Earth as viewed from the cabin of the Apollo 11 spacecraft. Earth was once a magma ocean, a hellish place hostile to life. Now it’s a beautiful, benign ocean world covered in life. Credit: NASA
What does this all amount to? The study’s objective was to determine if a planet’s bulk density indicates a magma ocean and if volatiles are trapped in the interior. Did it accomplish that? Sort of.
It narrows down the observable characteristics that can tell planetary scientists about magma worlds. The density fluctuations aren’t large enough in most cases to reveal much about the planet and if it might contain enough volatiles like carbon and oxygen to eventually form a life-supporting atmosphere. Instead, the results show that researchers should focus on other things like fluctuations in an exoplanet’s surface density.
The researchers write that they “cannot attribute the extremely low densities of some likely lava worlds primarily to magma. Instead, models addressing hot, relatively low-density planets should consider an atmosphere or smaller core-mass fraction in addition to magma.”
So it’s complicated, and while there are some answers here, it really leads to more questions.
“This work, which is a combination of earth sciences and astronomy, basically opens up exciting new questions about lava worlds,” said Boley.
Earth eventually cooled down, and as it cooled, it released volatiles from the magma and formed an atmosphere. Now only its core remains molten, and the molten core makes life possible by generating our protective magnetosphere. Might something similar happen on some magma ocean planets?
Most of the magma oceans we find are USPs and are very close to their stars. These planets will likely never cool enough to solidify if they maintain their close separation. But our detection methods are biased toward planets close to their stars. As planet-finding methods get better, we may find young magma planets further away from their stars, maybe in the habitable zones. Or, for some reason, some of the magma ocean USPs could migrate outward.
The magma ocean planets we’ve found are very close to their stars. Image Credit: NASA
Almost half of the rocky planets we’ve found around other stars could maintain magma on their surfaces. So there are probably billions of these planets in the Milky Way alone. It’s possible that one of them, probably as yet undiscovered, is very similar to Earth, with ample carbon and oxygen sequestered in its magma.
It’s possible that astronomers one day spot an Earth analogue among these lava worlds, but one that’s billions of years behind.
