When astrophysicists observe the cosmos, they see different types of black holes. They range from gargantuan supermassive black holes with billions of solar masses to difficult-to-find intermediate-mass black holes (IMBHs) all the way down to smaller stellar-mass black holes.
But there may be another class of these objects: primordial black holes (PBHs) that formed in the very early Universe. If they exist, the Nancy Grace Roman Space Telescope should be able to spot them.
Stellar-mass black holes form when massive stars explode as supernovae. SMBHs grow over time by merging with other black holes. How IMBHs form is still unclear, but it could involve mergers between stellar-mass black holes or multiple stellar collisions in dense star clusters.
Primordial black holes, if they exist, didn’t have any of these mechanisms available to them.
“If we find them, it will shake up the field of theoretical physics.”
William DeRocco, postdoctoral researcher, University of California Santa Cruz.
Nobody knows if primordial black holes exist. They’re theoretical. No physical process we know of can form them. But the early Universe was much different.
New research published in Physical Review D shows how the upcoming Nancy Grace Roman Telescope could detect these primordial Earth-mass objects. It’s titled “Revealing terrestrial-mass primordial black holes with the Nancy Grace Roman Space Telescope.” The lead author is William DeRocco, a postdoctoral researcher at the University of California Santa Cruz.
“Detecting a population of Earth-mass primordial black holes would be an incredible step for both astronomy and particle physics because these objects can’t be formed by any known physical process,” lead author DeRocco said. “If we find them, it will shake up the field of theoretical physics.”
In the modern Universe, only stars with at least eight stellar masses can become black holes. Less massive stars will become neutron stars or white dwarfs. (The Sun will become a white dwarf.)
But things were different in the early Universe. During a period of rapid inflation, space expanded faster than the speed of light. In these unusual conditions, dense areas could have collapsed into PBHs. The scale of these objects is remarkably small. They would be the size of Earth or smaller and have event horizons about as wide as a coin.
The least massive of these ones would’ve disappeared due to evaporation. That’s what Stephen Hawking figured out. But some, the ones as massive as Earth, could’ve survived.
Even though they’re theoretical, there are some evidential hints of their presence. Those hints come from gravitational microlensing.
Two efforts have used microlensing to study objects in the Universe. One is OGLE, the Optical Gravitational Lensing Experiment. Another is MOA, Microlensing Observations in Astrophysics. OGLE found 17 isolated Earth-mass objects in space.
These objects could be PBHs, or they could be rogue planets. Unfortunately, it’s very difficult to differentiate on an individual basis. But since theory predicts the masses and the abundance of rogue planets, that could provide a way for the Roman Telescope to tell them apart from PBHs.
“There’s no way to tell between Earth-mass black holes and rogue planets on a case-by-case basis,” DeRocco said. “Roman will be extremely powerful in differentiating between the two statistically.”
In their research, the authors explain it more fully. “The key point is that though PBH and FFP events cannot be discriminated on an event-by-event basis, the two populations can be distinguished by the statistical distribution of their event durations.” Scientists think that Roman will find 10 times as many objects in this mass range than ground-based efforts like OGLE and MOA.
Finding primordial black holes would create a big upheaval.
“It would affect everything from galaxy formation to the universe’s dark matter content to cosmic history,” said Kailash Sahu, an astronomer at the Space Telescope Science Institute in Baltimore. Sahu wasn’t involved in the research but understands the impact the results would have. “Confirming their identities will be hard work and astronomers will need a lot of convincing, but it would be well worth it.”
If the Roman Space Telescope can find the black holes and confirm them, it could be a defining moment in astronomical history. The discovery would be strong evidence in favour of a period of rapid inflation in the early Universe, an epoch that so far is unproven. Physicists think there must have been a period like this as it helps explain so much else about the Universe.
More excitingly, these primordial black holes could comprise a percentage of dark matter. A small percentage, but a massive improvement over our current understanding of what dark matter is. Scientists keep looking for things like WIMPs (Weakly Interacting Massive Particles) and other particles that could be dark matter, but they never find them.
“The nature of dark matter remains one of the most pressing open questions in fundamental physics. While multiple lines of compelling evidence indicate its existence, its microphysical nature remains unknown,” the authors explain.
The elegant thing about the Roman and PBHs is that it won’t require a special effort to find them. The Roman will already search for planets. “Roman’s Galactic Bulge Time Domain Survey is expected
to observe hundreds of low-mass microlensing events, enabling a robust statistical characterization
of this population,” the authors write in their paper.
Each space telescope we launch is a new window into some aspect of the Universe. The Nancy Grace Roman Space Telescope sure will be. “Though its Galactic Bulge Time Domain Survey targets bound and unbound exoplanets, we have shown that it will have unprecedented sensitivity to physics beyond the Standard Model as well,” DeRocco and his co-researchers write in their paper. That’s because it can “probe the fraction of dark matter composed of primordial black holes,” they write.
“This is an exciting example of something extra scientists could do with data Roman is already going to get as it searches for planets,” Sahu said. “And the results are interesting whether or not scientists find evidence that Earth-mass black holes exist. It would strengthen our understanding of the universe in either case.”
And who doesn’t want a stronger understanding of the Universe?
The post Roman Space Telescope Will Be Hunting For Primordial Black Holes appeared first on Universe Today.
Even though Venus and Earth are so-called sister planets, they’re as different as heaven and hell. Earth is a natural paradise where life has persevered under its azure skies despite multiple mass extinctions. On the other hand, Venus is a blistering planet with clouds of sulphuric acid and atmospheric pressure strong enough to squash a human being.
But the sister thing won’t go away because both worlds are about the same mass and radius and are rocky planets next to one another in the inner Solar System. Why are they so different? What do the differences tell us about our search for life?
The international astronomical community recognizes that understanding planetary habitability is a critical part of space science and astrobiology. Without a stronger understanding of terrestrial planets and their atmospheres, whether habitable or not, we won’t really know what we’re seeing when we examine a distant exoplanet. If we find an exoplanet that exhibits some signs of life, we’ll never visit it, never study it up close, and never be able to sample its atmosphere.
That shifts the scientific focus to the terrestrial planets in our own Solar System. Not because they appear to be habitable but because a complete model of terrestrial planets can’t be complete without including ones that are near-literal hellholes, like sister Venus.
A recent research perspective in Nature Astronomy examines how the two planets diverged and what might have driven the divergence. It’s titled “Venus as an anchor point for planetary habitability.” The lead author is Stephen Kane, from the Department of Earth and Planetary Sciences, University of California, Riverside. His co-author is Paul Byrne from the Department of Earth, Environmental, and Planetary Sciences, Washington University in St. Louis.
“A major focus of the planetary science and astrobiology community is understanding planetary habitability, including the myriad factors that control the evolution and sustainability of temperate surface environments such as that of Earth,” Kane and Byrne write. “The few substantial terrestrial planetary atmospheres within the Solar System serve as a critical resource for studying these habitability factors, from which models can be constructed for application to extrasolar planets.”
From their perspective, our Solar System’s twins provide our best opportunity to study how similar planets can have such divergent atmospheres. The more we understand that, the better we can understand how rocky worlds evolve over time and how different conditions benefit or restrict habitability.
Earth is an exception. With its temperate climate and surface water, it’s been habitable for billions of years, albeit with some climate episodes that severely restricted life. But when we look at Mars, it seems to have been habitable for a period of time and then lost its atmosphere and its surface water. Mars’ situation must be more common than Earth’s.
It’s a monumental challenge to understand an exoplanet when we know nothing of its history. We only see it at one epoch of its climate and atmospheric history. But the discovery of thousands of exoplanets is helping. “The discovery of thousands of exoplanets, and the confirmation that terrestrial planets are among the most common types, provides a statistical framework for studying planetary properties and their evolution generally,” the authors write.
A narrow range of properties allows biochemistry to emerge, and those properties may not last. We need to identify these properties and their parameters and build a better understanding of habitability. From this perspective, Venus is a treasure trove of information.
But Venus is a challenge. We can’t see through its dense clouds except with radar, and nobody’s tried landing a spacecraft there since the USSR in the 1980s. Most of those attempts failed, and the ones that survived didn’t last long. Without better data, we can’t understand Venus’ history. The simple answer is that it’s closer to the Sun. But it’s too simple to be helpful.
“The evolutionary pathway of Venus to its current runaway-greenhouse state is a matter of debate, having traditionally been attributed to its closer proximity to the Sun,” Kane and Byrne explain.
But when scientists look closer at Venus and Earth, they find many fundamental differences between them beyond their distances from the Sun. They have different rotation rates, they have differing obliquities, and they have different magnetic fields, to name a few. That means that we can’t measure the precise effect greater solar insolation has on the planet.
This is the authors’ main point. The differences between Earth and Venus make Venus a powerful part of understanding rocky exoplanet habitability. “Venus thus offers us a critical anchor point in the planetary habitability discourse, as its evolutionary story represents an alternate pathway from the Earth-based narrative—even though the origins of both worlds are, presumably, similar,” they write.
The authors point out that the basic requirement for life is surface water. But the bigger question is what factors govern how long surface water can persist. “By this measure, investigations of planetary habitability can then focus on the conditions that allow surface liquid water to be sustained through geological time,” they write.
Earth and Venus are on opposite ends of the spectrum of rocky planet habitability. That’s an important lesson we can learn from our own Solar System. For that reason, “…understanding the pathway to a Venus scenario is just as important as understanding the pathway to habitability that characterizes Earth,” the authors write.
The pair of researchers created a list of some of the factors that govern habitability on Earth and Venus.
There’s so much we don’t know about Venus. How big is its core? Did it ever have water? Some research shows that when the planet lost its water and became totally inhabitable, there was lots of oxygen in its atmosphere. If we saw that same amount of oxygen on a distant exoplanet, we might interpret it as a sign of life. Big mistake. “Venus thus acts as a cautionary tale for interpretations of apparently oxygen-rich atmospheres,” the authors write.
Kane and Byrne’s research perspective is a call to action. It mirrors what recent Decadal Surveys have said. “The recent astronomy and astrophysics, and planetary science and astrobiology decadal surveys both emphasize the need for an improved understanding of planetary habitability as an essential goal within the context of astrobiology,” they write. For the authors, Venus can anchor the effort.
But for it to serve as an anchor, scientists need answers to lots of questions. They need to study its atmosphere more thoroughly at all altitudes. They need to study its interior and determine the nature and size of its core. Critically, they need to get a spacecraft to its surface and examine its geology up close. In short, we need to do at Venus what we’ve done at Mars.
That’s challenging, considering Venus’ hostile environment. But missions are being prepared to explore Venus in more detail. VERITAS, DAVINCI, and EnVision are all Venus missions scheduled for the 2030s. Those missions will start to give scientists the answers we need.
As we learn more about Venus, we also need to learn more about exo-Venuses. “A parallel approach to studying the intrinsic properties of Venus is the statistical analysis of the vast (and still rapidly growing) inventory of terrestrial exoplanets,” the authors write.
We’re living in an age of exoplanet discovery. We’ve discovered over 5,000 confirmed exoplanets, and the tally keeps growing. We’re launching spacecraft to study the most interesting ones more thoroughly. But at some point, things will shift. How many of them do we need to catalogue? Is 10,000 enough? 20,000? 100,000?
It’s all new right now, and the enthusiasm to find more exoplanets, especially rocky ones in habitable zones, is understandable. But eventually, we’ll reach some kind of threshold of diminishing returns. In order to understand them, our effort might be more wisely spent studying Venus and how it evolved so differently.
Just as Kane and Byrne suggest.
The post What Deadly Venus Can Tell Us About Life on Other Worlds appeared first on Universe Today.
The Gum Nebula is an emission nebula almost 1400 light-years away. It’s home to an object known as “God’s Hand” among the faithful. The rest of us call it CG 4.
Many objects in space take on fascinating, ethereal shapes straight out of someone’s psychedelic fantasy. CG4 is definitely ethereal and extraordinary, but it’s also a little more prosaic. It looks like a hand extending into space.
The Dark Energy Camera (DECam) on the NSF’s Víctor M. Blanco 4-meter Telescope captured the image. DECam’s primary job is to survey hundreds of millions of galaxies in its study of dark energy. But it’s also a general-purpose instrument used for other scientific endeavours.
CG 4 is called a cometary globule because of its appearance. But it’s actually a star-forming region. It has a head that’s about 1.5 light-years in diameter and a tail that’s about 8 light-years long. The head is dense and opaque and is lit up by a nearby star. The globule is surrounded by a diffuse red glow, emissions from ionized hydrogen.
There are lots of cometary globules in the Milky Way. They’re a sub-class of objects called Bok globules, after astronomer Bart Bok, who discovered them. Both types of globules are dark nebulae, molecular clouds so dense they block optical light. Astronomers aren’t absolutely certain how cometary globules get their shape.
But they do know what’s happening to them.
The red glow surrounding CG 4 is ionized hydrogen lit up by radiation from nearby hot, massive stars. That same radiation is eroding CG 4 away. Since the globule is denser than its surroundings, it’s resisting diffusion. It still contains enough gas and dust to form several new stars about as massive as the Sun.
Even though there are many of these globules in the Milky Way, the majority of them are in the Gum Nebula. Scientists know of 31 other globules in the nebula. This one’s called CG 4 (Cometary Globule 4) because they’re all numbered.
The Gum Nebula is likely the remnant of a huge supernova explosion, and that could be the reason the globules have their unique shape. They may have originally been spherical nebula like the Ring Nebula. But a powerful supernova explosion about one million years ago stretched them into their long, comet-like forms.
Astronomers also suggest another reason for their shape. Nearby hot, massive stars exert radiation pressure on the globules, and their stellar wind also slams into them. In the Gum Nebula, their tails point away from the Vela Supernova Remnant and the pulsar that sits in its centre. Since the Vela Pulsar is a spinning neutron star, it’s possible that its winds and radiation pressure are shaping CG 4.
Whatever its cause, the Hand of God is a visually intriguing object. If you really want to lose yourself in this amazing nebula, download the TIFF file here.
The post A Nebula that Extends its Hand into Space appeared first on Universe Today.
Earth is naked without its protective barrier. The planet’s magnetic shield surrounds Earth and shelters it from the natural onslaught of cosmic rays. But sometimes, the shield weakens and wavers, allowing cosmic rays to strike the atmosphere, creating a shower of particles that scientists think could wreak havoc on the biosphere.
This has happened many times in our planet’s history, including 41,000 years ago in an event called the Laschamps excursion.
Cosmic rays are high-energy particles, usually protons or atomic nuclei, that travel through space at relativistic speeds. Normally, they’re deflected into space and away from Earth by the planet’s magnetic shield. But the shield is a natural phenomenon and its strength fluctuates, as does its orientation. When that happens, cosmic rays strike the Earth’s atmosphere.
That creates a shower of secondary particles called cosmogenic radionuclides. These isotopes become embedded in sediments and ice cores and even in the structure of living things like trees. There are different types of these isotopes, including ones like Calcium 41 and Carbon 14.
Some of the isotopes are stable, and some are radioactive. The radioactive ones have half-lives ranging from only 20 minutes (Carbon 11) up to 15.7 million years (Xenon 129.)
When Earth’s shield weakens, more of these isotopes reach the planet’s surface and collect in sediments and ice. By studying these cores and sediments, scientists can determine the magnetic shield’s history. Their observations show that Earth experienced a geomagnetic excursion or reversal 41,000 years ago. It’s called the Laschamps excursion after the Laschamps lava flows in France, where geomagnetic anomalies revealed its occurrence.
Every few hundred thousand years, the Earth’s magnetic poles flip. North becomes South and vice versa. In between those major events are more minor events called excursions. During excursions, the poles shift around for a while without swapping places. The excursions weaken the Earth’s shield and can last from a few thousand to tens of thousands of years. When that happens, more cosmic rays strike the atmosphere, creating more radionuclides that shower down onto Earth.
Scientists often focus on one particular radioactive isotope in paleomagnetic studies. Beryllium 10 has a relatively long half-life of 1.36 million years and tends to accumulate on the soil surface.
Sanja Panovska is a researcher at GFZ Potsdam, Germany, who studies geomagnetism. At the recent European Geosciences Union (EGU) General Assembly 2024, Panovska presented new research on the Laschamps excursion. She found that during the Laschamps excursion, production of Be 10 was twice as high as normal.
To understand the Laschamps excursion more thoroughly, Panovska combined cosmogenic radionuclide and paleomagnetic data to reconstruct the Earth’s magnetic field at the time. She found that when the field decreased in strength, it also shrank. The transition from normal field to reversed field took about 250 years, and it stayed flipped for about 440 years. During the transition, the Earth’s shield weekend to as little as 5% of its normal strength. When it was fully reversed, it was at about 25% of its regular strength. This weakening allowed more Be 10 and other cosmogenic radionuclides to reach Earth’s surface.
![Each map shows the intensity of Earth's geomagnetic field at different snapshots in time, according to Panovska's reconstructions that are constrained by both paleomagnetic data and records of cosmogenic beryllium-10 radionuclides. DM stands for Dipole Moment, which is a measure of the field's polarity or separation of positive and negative. Age [ka BP] is the age measures in thousands of years before the present. Image Credit: Sanja Panovska.](https://www.universetoday.com/wp-content/uploads/2024/05/Panovska-summary-map.jpg)
These radionuclides do more than collect in sediments and ice. Some of them are radioactive. The weakening of the shield also weakened the ozone layer, letting more UV radiation reach Earth’s surface. The high-altitude atmosphere also cooled, which changed the wind flows. This could’ve caused drastic changes on the Earth’s surface.
For these reasons, the Laschamps event has been linked to the extinction of the Neanderthals, the extinction of Australian megafauna, and even to the appearance of cave art. Those links haven’t withstood scientific scrutiny, but that doesn’t mean that events like the Laschamps event aren’t hazardous. If it occurred now, it would knock out our power grids. The Earth’s equatorial region would light up with aurorae.
“Understanding these extreme events is important for their occurrence in the future, space climate predictions, and assessing the effects on the environment and on the Earth system,” Panovska said.
Scientists are learning that the magnetic shield isn’t static. There are anomalies. One of them is the South Atlantic Anomaly, a region where the magnetic field is weakest near Earth. When satellites pass over this region, they’re exposed to higher levels of ionizing radiation. The anomaly is likely caused by a reservoir of dense rock inside Earth, illustrating how complex the magnetic shield is.
Scientists are uncertain about what effect the cosmic rays have on life when the magnetic shield is weak. It’s tempting to correlate extinctions with events like the Laschamps excursion when they line up temporally. But the poles have shifted, weakened, and reversed many times and life is still here and still thriving.
If humanity lasts long enough, we’ll go through one of these reversals. Then we’ll know.
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No human being will ever encounter a black hole. But we can’t stop wondering what it would be like to fall into one of these massive, beguiling, physics-defying singularities.
NASA created a simulation to help us imagine what it would be like.
Jeremy Schnittman is an astrophysicist at NASA’s Goddard Space Flight Center and he created the visualizations. “People often ask about this, and simulating these difficult-to-imagine processes helps me connect the mathematics of relativity to actual consequences in the real universe,” he said. “So I simulated two different scenarios, one where a camera — a stand-in for a daring astronaut — just misses the event horizon and slingshots back out, and one where it crosses the boundary, sealing its fate.”
In one, the viewpoint plunges directly into the black hole like a free-falling astronaut, with explanatory text to guide us through what we’re seeing. The other is a 360-degree view of the black hole.
Schnittman created them with a NASA supercomputer called Discover in only five days, generating about 10 terabytes of data. The computer used only about 0.3% of its power. The same visualization would’ve taken more than a decade to create on an average laptop computer.
The black hole in the visualization is the same size as Sagittarius A star, the supermassive black hole (SMBH) at the heart of the Milky Way. It has 4.3 million solar masses and dominates the galaxy’s inner regions. Its event horizon reaches about 25 million km (16 million miles). That’s about 17% of the distance from Earth to the Sun. The event horizon is surrounded by an accretion disk, a swirling disk of superheated material drawn in by the black hole’s overpowering gravity.
Another type of black hole, the stellar-mass black hole, is much less massive. Schnittman says that if you’re going to fall into a black hole, you’d rather fall into the supermassive one.
“If you have the choice, you want to fall into a supermassive black hole,” Schnittman explained. “Stellar-mass black holes, which contain up to about 30 solar masses, possess much smaller event horizons and stronger tidal forces, which can rip apart approaching objects before they get to the horizon.”
Powerful gravity is the reason. The SMBH’s gravity is so strong that it pulls harder on the end of the object nearest it. That stretches the object and elongates it. Stephen Hawking was the first to call this ‘spaghettification,’ and the name has stuck. Presumably, you’d get a better look if you fall into an SMBH.
In the movies, the camera begins at a distance of 640 million km (400 million miles.) Since space-time is warped around a black hole, so are the images of the sky, the black hole’s disk, and the photon ring. It takes the camera three hours of real-time to fall into the event horizon, and it completes almost two 30-minute orbits as it falls. A distant observer would never see an object ever reach the black hole. From a distance, the object would freeze at the event horizon.
When a falling object reaches the event horizon, it and space-time itself reach the speed of light. After crossing the horizon, the object and the space-time around it surge toward the singularity, a point of infinite density and gravity. “Once the camera crosses the horizon, its destruction by spaghettification is just 12.8 seconds away,” Schnittman said.
In the second video, the camera never crosses the event horizon and instead escapes. But the powerful black hole still has an effect. Imagine if the camera were an astronaut, and they flew this six-hour roundtrip while a separate astronaut stayed far away from the SMBH. The astronaut would return and be 36 minutes younger than the astronaut who never approached the black hole.
“This situation can be even more extreme,” Schnittman noted. “If the black hole were rapidly rotating, like the one shown in the 2014 movie ‘Interstellar,’ she would return many years younger than her shipmates.”
The bottom line is, don’t fall into a black hole. In fact, resist your fascination and don’t even approach one.
Leave them for the physicists.
The post Fall Into a Black Hole With this New NASA Simulation appeared first on Universe Today.
The Sun is increasing its intensity on schedule, continuing its approach to solar maximum. In just over a 24-hour period on May 5 and May 6, 2024, the Sun released three X-class solar flares measuring at X1.3, X1.2, and X4.5. Solar flares can impact radio communications and electric power grids here on Earth, and they also pose a risk to spacecraft and astronauts in space.
NASA released an animation that shows the solar flares blasting off the surface of the rotating Sun, below.
Predicting when solar maximum will occur is not easy and the timing of it can only be confirmed after it happens. But NOAA’s Space Weather Prediction Center (SWPC) currently estimates that solar maximum will likely occur between May 2024 and early 2026. The Sun goes through a cycle of high and low activity approximately every 11 years, driven by the Sun’s magnetic field and indicated by the frequency and intensity of sunspots and other activity on the surface. The SWPC has been working hard to have a better handle on predicting solar cycles and activity. Find out more about that here.
Solar flares are explosions on the Sun that release powerful bursts of energy and radiation coming from the magnetic energy associated with the sunspots. The more sunspots, the greater potential for flares.
Flares are classified based on a system similar to the Richter scale for earthquakes, which divides solar flares according to their strength. X-class is the most intense category of flares, while the smallest ones are A-class, followed by B, C, M and then X. Each letter represents a 10-fold increase in energy output. So an X is ten times an M and 100 times a C. The number that follows the letter provides more information about its strength. The higher the number, the stronger the flare.
Flares are our solar system’s largest explosive events. They are seen as bright areas on the Sun and can last from minutes to hours. We typically see a solar flare by the photons (or light) it releases, occurring in various wavelengths.
Sometimes, but not always, solar flares can be accompanied by a coronal mass ejection (CME), where giant clouds of particles from the Sun are hurled out into space. If we’re lucky, these charged particles will provide a stunning show of auroras here on Earth while not impacting power grids or satellites.
Thankfully, missions like the Solar Dynamics Observatory, Solar Orbiter, the Parker Solar Probe are providing amazing views and new details about the Sun, helping astronomers to learn more about the dynamic ball of gas that powers our entire Solar System.
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Does another undetected planet languish in our Solar System’s distant reaches? Does it follow a distant orbit around the Sun in the murky realm of comets and other icy objects? For some researchers, the answer is “almost certainly.”
The case for Planet Nine (P9) goes back at least as far as 2016. In that year, astronomers Mike Brown and Konstantin Batygin published evidence pointing to its existence. Along with colleagues, they’ve published other work supporting P9 since then.
There’s lots of evidence for the existence of P9, but none of it has reached the threshold of definitive proof. The main evidence concerns the orbits of Extreme Trans-Neptunian Objects (ETNOs). They exhibit a peculiar clustering that indicates a massive object. P9 might be shepherding these objects along on their orbits.
The names Brown and Batygin, both Caltech astronomers, come up often in regard to P9. Now, they’ve published another paper along with colleagues Alessandro Morbidelli and David Nesvorny, presenting more evidence supporting P9.
It’s titled “Generation of Low-Inclination, Neptune-Crossing TNOs by Planet Nine.” It’s published in The Astrophysical Journal Letters.
“The solar system’s distant reaches exhibit a wealth of anomalous dynamical structure, hinting at the presence of a yet-undetected, massive trans-Neptunian body—Planet Nine (P9),” the authors write. “Previous analyses have shown how orbital evolution induced by this object can explain the origins of a broad assortment of exotic orbits.”
To dig deeper into the issue, Batygin, Brown, Morbidelli, and Nesvorny examined Trans-Neptunian Objects (TNOs) with more conventional orbits. They carried out N-body simulations of these objects that included everything from the tug of giant planets and the Galactic Tide to passing stars.
29 objects in the Minor Planet Database have well-characterized orbits with a > 100 au, inclinations < 40°, and q (perihelia) < 30 au. Of those 29, 17 have well-quantified orbits. The researchers focused their simulations on these 17.
The researchers’ goal was to analyze these objects’ origins and determine if they could be used as a probe for P9. To accomplish this, they conducted two separate sets of simulations. One set with P9 in the Solar System and one set without.
The simulations began at t=300 million years, meaning 300 million years into the Solar System’s existence. At that time, “intrinsic dynamical evolution in the outer solar system is still in its infancy,” the authors explain, while enough time has passed for the Solar System’s birth cluster of stars to disperse and for the giant planets to have largely concluded their migrations. They ended up with about 2000 objects, or particles, in the simulation with perihelia greater than 30 au and semimajor axes between 100 and 5000 au. This ruled out all Neptune-crossing objects from the simulation’s starting conditions. “Importantly, this choice of initial conditions is inherently linked with the assumed orbit of P9,” they point out.
The figure below shows the evolution of some of the 2,000 objects in the simulations.
These are interesting results, but the researchers point out that they in no way prove the existence of P9. These orbits could be generated by other things like the Galactic Tide. In their next step, they examined their perihelion distribution.
“Accounting for observational biases, our results reveal that the orbital architecture of this group of objects aligns closely with the predictions of the P9-inclusive model,” the authors write. “In stark contrast, the P9-free scenario is statistically rejected at a ~5? confidence level.”
The authors point out that something other than P9 could be causing the orbital unruliness. The star was born in a cluster, and cluster dynamics could’ve set these objects on their unusual orbits before the cluster dispersed. A number of Earth-mass rogue planets could also be responsible, influencing the outer Solar System’s architecture for a few hundred million years before being removed somehow.
However, the authors chose their 17 TNOs for a reason. “Due to their low inclinations and perihelia, these objects experience rapid orbital chaos and have short dynamical lifetimes,” the authors write. That means that whatever is driving these objects into these orbits is ongoing and not a relic from the past.
An important result of this work is that it results in falsifiable predictions. And we may not have to wait long for the results to be tested. “Excitingly, the dynamics described here, along with all other lines of evidence for P9, will soon face a rigorous test with the operational commencement of the VRO (Vera Rubin Observatory),” the authors write.
If P9 is real, what is it? It could be the core of a giant planet ejected during the Solar System’s early days. It could be a rogue planet that drifted through interstellar space until being caught up in our Solar System’s gravitational milieu. Or it could be a planet that formed on a distant orbit, and a passing star shepherded it into its eccentric orbit. If astronomers can confirm P9’s existence, the next question will be, ‘what is it?’
If you’re interested at all in how science operates, the case of P9 is very instructive. Eureka moments are few and far between in modern astronomy. Evidence mounts incrementally, accompanied by discussion and counterpoint. Objections are raised and inconsistencies pointed out, then methods are refined and thinking advances. What began as one over-arching question is broken down into smaller, more easily-answered ones.
But the big question dominates for now and likely will for a while longer: Is there a Planet Nine?
Stay tuned.
The post New Evidence for Our Solar System’s Ghost: Planet Nine appeared first on Universe Today.
It’s that time again. NIAC (NASA Innovative Advanced Concepts) has announced six concepts that will receive funding and proceed to the second phase of development. This is always an interesting look at the technologies and missions that could come to fruition in the future.
The six chosen ones will each receive $600,000 in funding to pursue the ideas for the next two years. NASA expects each team to use the two years to address both technical and budgetary hurdles for their concepts. When this second phase comes to an end, some of the concepts could advance to the third stage.
“These diverse, science fiction-like concepts represent a fantastic class of Phase II studies,” said John Nelson, NIAC program executive at NASA Headquarters in Washington. “Our NIAC fellows never cease to amaze and inspire, and this class definitely gives NASA a lot to think about in terms of what’s possible in the future.”
Here they are.
Fluidic Telescope (FLUTE): Enabling the Next Generation of Large Space Observatories
Telescopes are built around mirrors and lenses, whether they’re ground-based or space-based. The JWST’s large mirror is 6.5 meters in diameter but had to be folded up to fit inside the rocket that launched it and then unfolded in space. That’s a tricky engineering feat. Engineers are building larger and larger ground-based telescopes, too, and they’re equally tricky to design and build. Could FLUTE change this?
FLUTE envisions lenses made of fluid, and the FLUTE team’s concept describes a space telescope with a primary mirror 50 meters (164 ft.) in diameter. Creating glass lenses for a telescope this large isn’t realistic. “Using current technologies, scaling up space telescopes to apertures larger than approximately 33 feet (10 meters) in diameter does not appear economically viable,” the FLUTE website states.
But in the microgravity of space, fluids behave in an intriguing way. Surface tension holds liquids together at their surfaces. We can see this on Earth, where some insects use surface tension to glide along the surfaces of ponds and other bodies of water. Also, on Earth, surface tension holds small drops of water together. But in space, away from Earth’s dominating gravity, surface tension is much more effective. There, water maintains the most energy efficient shape there is: a sphere.
Another force governs water: adhesion. Adhesion causes liquids to cling to surfaces. In the microgravity of space, adhesion can bind liquid to a circular, ring-like frame. Then, due to surface tension, the liquid will naturally adopt a spherical shape. If the liquid can be made to bulge inward rather than outward, and if the liquid is reflective enough, it creates a telescope mirror.
The FLUTE team would like to make optical components in space. The liquid would stay in the liquid state and form an extremely smooth light-collecting surface. As a bonus, FLUTE would also self-repair after any micrometeorite strike.
The FLUTE study is led by Edward Balaban from NASA’s Ames Research Center in California’s Silicon Valley. The FLUTE team has already done some tests on the ISS and on zero-g flights.
Pulsed Plasma Rocket (PPR): Shielded, Fast Transits for Humans to Mars
It takes too long to get to Mars. It’s a six-month journey each way, plus time spent on the surface. All that time in microgravity, exposure to radiation, and other challenges make the trip very difficult for astronauts. PPR aims to fix that.
PPR isn’t a launch vehicle for escaping Earth’s gravity well. It would be launched on a heavy lift vehicle like SLS and then sent on its way.
PPR was originally derived from the Pulsed Fission Fusion concept. But it’s more affordable, and also smaller and simpler. PPR might generate 100,000 N of thrust with a specific impulse (Isp) of 5,000 seconds. Those are good numbers. PPR could reduce the travel time to Mars to two months.
It has other benefits as well. It could propel larger spacecraft to Mars on trips longer than two months, carrying more cargo and also provide heavier shielding against cosmic rays. “The PPR enables a whole new era in space exploration,” the team writes.
PPR is basically a fusion system ignited by fission. It’s similar to a thermonuclear weapon. But rather than a run-away explosion, the combined energy is directed through a magnetic nozzle to produce thrust.
In phase two, the PPR team intends to optimize the engine design to produce more specific impulse, perform proof-of-concept experiments for major components, and design a shielded ship for human missions to Mars.
This study is led by Brianna Clements with Howe Industries in Scottsdale, Arizona.
The Great Observatory for Long Wavelengths (GO-LoW)
One of modern astronomy’s last frontiers is the low-frequency radio sky. Earth’s ionosphere blocks our ground-based telescopes from seeing it. And space-based telescopes can’t see it either. It’s because the wavelengths are so long, in the meter to the kilometre scale. Only extremely massive telescopes could see these waves clearly.
GO-LoW is a potential solution. It’s a space-based array of thousands of identical Small-Sats arranged as an interferometer. It would sit at an Earth-Sun Lagrange point and observe exoplanet and stellar magnetic fields. Exoplanet magnetic fields emit radio waves between 100 kHz and 15 MHz. The GO-LoW team says their interferometer could perform the first survey of exoplanetary magnetic fields within 5 parsecs (16 light years.) Magnetic fields tell scientists a lot about an exoplanet, its evolution, and its processes.
While there’s no doubt that large telescopes like the JWST are powerful and effective, they’re extremely complex and expensive. And if something goes wrong with a critical component, the mission could end.
GO-LoW takes a different approach. By using thousands of individual satellites, the system is more resilient. GO-LoW would have a hybrid constellation. Some of the satellites would be smaller and simpler satellites called “listener nodes” (LN,) while a smaller number of them would be “communication and computation” nodes (CCNs). They would collect data from the LNs, process it, and beam it back to Earth.
The GO-LoW says it would only take a few heavy launches to place an entire 100,000 satellite constellation in space.
The technology for the SmallSats already exists. The challenge the GO-LoW team will address with their phase two funding is developing a system that will harness everything together effectively. “The coordination of all these physical elements, data products, and communications systems is novel and challenging, especially at scale,” they write.
GO-LoW is led by Mary Knapp with MIT in Cambridge, Massachusetts.
Radioisotope Thermoradiative Cell Power Generator
It’s sort of like solar power in reverse.
The RTCPG is a power source for spacecraft visiting the outer planets. They promise smaller, more efficient power generation for smaller science and exploration missions that can’t carry a solar power system or nuclear power system. Both those systems are bulky, and solar power is limited the further away from the sun a spacecraft goes.
The thermoradiative cell (TRC) uses radioisotopes to create heat as an MMRTG does. But the TRC uses the heat to generate infrared light which generates electricity. In initial testing, the system generated 4.5 times more power from the same amount of PU-238.
Much of phase two’s work will involve materials. “Metal-semiconductor contacts capable of surviving the required elevated temperatures will be investigated,” the team explains. The team developed a special cryostat testing apparatus in phase one.
“Building on our results from Phase I, we believe there is much more potential to unlock here,” the team writes.
This power generation concept study is from Stephen Polly at the Rochester Institute of Technology in New York.
FLOAT: Flexible Levitation on a Track
What if Artemis is enormously successful? How will astronauts move their equipment around the lunar surface efficiently?
FLOAT would provide autonomous transportation for payloads on the Moon. “A durable, long-life robotic transport system will be critical to the daily operations of a sustainable lunar base in the 2030’s,” the FLOAT team writes.
The heart of FLOAT is a three-layer flexible track that’s unrolled into position without major construction. It consists of three layers: a graphite layer, a flex-circuit layer, and a solar panel layer.
The graphite layer allows robots to use diamagnetic levitation to float over the track. The flex-circuit layer supplies the thrust that moves them, and the thin-film solar panel layer generates electricity for a lunar base when it’s in sunlight.
The system can be used to move regolith around for in-situ resource utilization and to transport payloads around a lunar base, for example, from landing zones to habitats.
“Individual FLOAT robots will be able to transport payloads of varying shape/size (>30 kg/m^2) at useful speeds (>0.5m/s), and a large-scale FLOAT system will be capable of moving up to 100,000s kg of regolith/payload multiple kilometres per day,” the FLOAT team explains.
With their phase two funding, the FLOAT team intends to design, build, and test scaled-down versions of FLOAT robots and track. Then, they’ll test their system in a lunar analog testbed. They’ll also test environmental effects on the system and how they alter the system’s performance and longevity.
Ethan Schaler leads FLOAT at NASA’s Jet Propulsion Laboratory in Southern California.
SCOPE: ScienceCraft for Outer Planet Exploration
Some of the most intriguing planets and moons in the Solar System are well beyond Jupiter. But exploring them is challenging. Extremely long travel times, restrictive mission windows, and large expenses limit our exploration. But SCOPE aims to address these limitations.
Typically, a spacecraft carries a propulsion and power system along with its instruments and communication systems. NASA’s Juno mission to Jupiter, for example, carries a chemical rocket engine for propulsion, 50 square meters of solar panels, and 10 science instruments. The solar panels alone weigh 340 kg (750 lbs.) Juno is powerful, produces a wide variety of quality science data, and is expensive.
ScienceCraft takes a different approach. It combines a single science instrument and spacecraft into one monolithic structure. It’s basically a solar sail with a built-in spectrometer. They’re aiming their design at the Neptune-Triton system.
“By printing an ultra-lightweight quantum dot-based spectrometer, developed by the PI Sultana, directly on the solar sail, we create a breakthrough spacecraft architecture allowing an unprecedented parallelism and throughput of data collection and rapid travel across the solar system,” the ScienceCraft team writes.
Instead of merely providing the propulsion, the sail doubles as the spacecraft’s science instrument. The small mass means that ScienceCraft could be carried into orbit as a secondary payload. The team says they’ll use phase two to identify and develop key technologies for the spacecraft and to further mature the mission concept. They say that because of the low cost and simplicity, they could be ready by 2045.
“By leveraging these benefits, we propose a mission concept to Triton, a unique planetary body in our solar system, within the short window that closes around 2045 to answer compelling science questions about Triton’s atmosphere, ionosphere, plumes and internal structure,” the ScienceCraft team explains.
ScienceCraft is led by NASA’s Mahmooda Sultana at the agency’s Goddard Space Flight Center in Greenbelt, Maryland.
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On Friday, May 3rd, the sixth mission in the Chinese Lunar Exploration Program (Chang’e-6) launched from the Wenchang Spacecraft Launch Site in southern China. Shortly after, China announced that the spacecraft separated successfully from its Long March 5 Y8 rocket. The mission, consisting of an orbiter and lander element, is now on its way to the Moon and will arrive there in a few weeks. By June, the lander element will touch down on the far side of the Moon, where it will gather about 2 kg (4.4 lbs) of rock and soil samples for return to Earth.
The mission launched four years after its predecessor, Chang’e-5, became China’s first sample-return mission to reach the Moon. It was also the first lunar sample return mission since the Soviet Luna 24 mission landed in Mare Crisium (the Sea of Crisis) in 1976. Compared to its predecessor, the Chang’e-6 mission weighs an additional 100 kg (220 lbs), making it the heaviest probe launched by the Chinese space program. The surface elements also face lesser-known terrain on the far side of the Moon and require a relay satellite for communications.
Speaking of surface elements, the China Academy of Space Technology (CAST) has since released images showing how the mission also carries a rover element. This payload was not part of mission data disclosed by China before the flight. But as SpaceNews’ Andrew Jones pointed out, the rover can be seen in the CAST images (see above) integrated onto the side of the lander.
“Little is known about the rover, but a mention of a Chang’e-6 rover is made in a post from the Shanghai Institute of Ceramics (SIC) under the Chinese Academy of Sciences (CAS),” he wrote. “It suggests the small vehicle carries an infrared imaging spectrometer.” This rover is no doubt intended to assist the lander with investigating resources on the far side of the Moon. This is consistent with China’s long-term plans for building the International Lunar Research Station (ILRS) around the southern polar region in collaboration with Roscosmos and other international patterns.
Similar to NASA’s plans for the Lunar Gateway and Artemis Base Camp, this requires that building sites be selected near sources of water ice and building materials (silica and other minerals). Ge Ping, the deputy director of the Center of Lunar Exploration and Space Engineering (CLESE) with the China National Space Administration (CNSA), related the importance of the sample-return mission to CGTN (a state-owned media company) before the launch:
“The Aitken Basin is one of the three major terrains on the Moon and has significant scientific value. Finding and collecting samples from different regions and ages of the Moon is crucial for our understanding of it. These would further study of the moon’s origin and its evolutionary history.”
In addition, the Chang’e-6 orbiter carries four international payloads and satellites including a French radon detector contributed by the ESA. Known as the Detection of Outgassing Radon (DORN), this payload will study how lunar dust and other volatiles (especially water) are transferred between the lunar regolith and the lunar exosphere. Then there’s the Italian INstrument for landing-Roving laser Retroreflector Investigations (INRRI), similar to those used by the Schiaparelli EDM module and InSight lander, that precisely measures distances from the lander to orbit.
There’s also the Swedish Negative Ions on Lunar Surface (NILS), an instrument that will detect and measure negative ions reflected by the lunar surface. Lastly, there’s the Pakistani ICUBE-Q CubeSat developed by the Institute of Space Technology (IST) and Shanghai Jiao Tong University (SJTU), which will take images of the lunar surface using two optical cameras and measure the Moon’s magnetic field. The data these instruments provide will reveal new information about the lunar environment that will inform plans for long-duration missions on the surface.
By 2026, the Chang’e-6 mission will be joined by Chang’e-7, including an orbiter, lander, rover, and a mini-hopping probe. The data provided by the program will assist China’s plans to land taikonauts around the lunar south pole by 2030, followed by the completion of the ILRS by 2035.
Further Reading: CGTN
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Earth is the only life-supporting planet we know of, so it’s tempting to use it as a standard in the search for life elsewhere. But the modern Earth can’t serve as a basis for evaluating exoplanets and their potential to support life. Earth’s atmosphere has changed radically over its 4.5 billion years.
A better way is to determine what biomarkers were present in Earth’s atmosphere at different stages in its evolution and judge other planets on that basis.
That’s what a group of researchers from the UK and the USA did. Their research is titled “The early Earth as an analogue for exoplanetary biogeochemistry,” and it appears in Reviews in Mineralogy. The lead author is Eva E. Stüeken, a PhD student at the School of Earth & Environmental Sciences, University of St Andrews, UK.
When Earth formed about 4.5 billion years ago, its atmosphere was nothing like it is today. At that time, the atmosphere and oceans were anoxic. About 2.4 billion years ago, free oxygen began to accumulate in the atmosphere during the Great Oxygenation Event, one of the defining periods in Earth’s history. But the oxygen came from life itself, meaning life was present when the Earth’s atmosphere was much different.
This isn’t the only example of how Earth’s atmosphere has changed over geological time. But it’s an instructive one and shows why searching for life means more than just searching for an atmosphere like modern Earth’s. If that’s the way we conducted the search, we’d miss worlds where photosynthesis hadn’t yet appeared.
In their research, the authors point out how Earth hosted a rich and evolving population of microbes under different atmospheric conditions for billions of years.
“For most of this time, Earth has been inhabited by a purely microbial biosphere albeit with seemingly increasing complexity over time,” the authors write. “A rich record of this geobiological evolution over most of Earth’s history thus provides insights into the remote detectability of microbial life under a variety of planetary conditions.”
It’s not just life that’s changed over time. Plate tectonics have changed and may have been ‘stagnant lid’ tectonics for a long time. In stagnant lid tectonics, plates don’t move horizontally. That can have consequences for atmospheric chemistry.
The main point is that Earth’s atmosphere does not reflect the solar nebula the planet formed in. Multiple intertwined processes have changed the atmosphere over time. The search for life involves not only a better understanding of these processes, but how to identify what stage exoplanets might be in.
It’s axiomatic that biological processes can have a dramatic effect on planetary atmospheres. “On the modern Earth, the atmospheric composition is very strongly controlled by life,” the researchers write. “However, any potential atmospheric biosignature must be disentangled from a backdrop of abiotic (geological and astrophysical) processes that also contribute to planetary atmospheres and would be dominating on lifeless worlds and on planets with a very small biosphere.”
The authors outline what they say are the most important lessons that the early Earth can teach us about the search for life.
The first is that the Earth has actually had three different atmospheres throughout its long history. The first one came from the solar nebula and was lost soon after the planet formed. That’s the primary atmosphere. The second one formed from outgassing from the planet’s interior. The third one, Earth’s modern atmosphere, is complex. It’s a balancing act involving life, plate tectonics, volcanism, and even atmospheric escape. A better understanding of how Earth’s atmosphere has changed over time gives researchers a better understanding of what they see in exoplanet atmospheres.
The second is that the further we look back in time, the more the rock record of Earth’s early life is altered or destroyed. Our best evidence suggests life was present by 3.5 billion years ago, maybe even by 3.7 billion years ago. If that’s the case, the first life may have existed on a world covered in oceans, with no continental land masses and only volcanic islands. If there had been abundant volcanic and geological activity between 3.5 and 3.7 billion years ago, there would’ve been large fluxes of CO2 and H2. Since these are substrates for methanogenesis, then methane may have been abundant in the atmosphere and detectable.
The third lesson the authors outline is that a planet can host oxygen-producing life for a long time before oxygen can be detected in an atmosphere. Scientists think that oxygenic photosynthesis appeared on Earth in the mid-Archean eon. The Archean spanned from 4 billion to 2.5 billion years ago, so mid-Archean is sometime around 3.25 billion years ago. But oxygen couldn’t accumulate in the atmosphere until the Great Oxygenation Event about 2.4 billion years ago. Oxygen is a powerful biomarker, and if we find it in an exoplanet’s atmosphere, it would be cause for excitement. But life on Earth was around for a long time before atmospheric oxygen would’ve been detectable.
The fourth lesson involves the appearance of horizontal plate tectonics and its effect on chemistry. “From the GOE onwards, the Earth looked tectonically similar to today,” the authors write. The oceans were likely stratified into an anoxic layer and an oxygenated surface layer. However, hydrothermal activity constantly introduced ferrous iron into the oceans. That increased the sulphate levels in the seawater which reduced the methane in the atmosphere. Without that methane, Earth’s biosphere would’ve been much less detectable. Complicated, huh?
“Planet Earth has evolved over the past 4.5 billion years from an entirely anoxic planet
with possibly a different tectonic regime to the oxygenated world with horizontal plate
tectonics that we know today,” the authors explain. All that complex evolution allowed life to appear and to thrive, but it also makes detecting earlier biospheres on exoplanets more complicated.
We’re at a huge disadvantage in the search for life on exoplanets. We can literally dig into Earth’s ancient rock to try to untangle the long history of life on Earth and how the atmosphere evolved over billions of years. When it comes to exoplanets, all we have is telescopes. Increasingly powerful telescopes, but telescopes nonetheless. While we are beginning to explore our own Solar System, especially Mars and the tantalizing ocean moons orbiting the gas giants, other solar systems are beyond our physical reach.
“We must instead remotely recognize the presence of alien biospheres and characterize their biogeochemical cycles in planetary spectra obtained with large ground- and space-based telescopes,” the authors write. “These telescopes can probe atmospheric composition by detecting absorption features associated with specific gases.” Probing atmospheric gases is our most powerful approach right now, as the JWST shows.
But as scientists get better tools, they’ll start to go beyond atmospheric chemistry. “We might also be able to recognize global-scale surface features, including light interaction with photosynthetic pigments and ‘glint’ arising from specular reflection of light by a liquid ocean.”
Understanding what we’re seeing in exoplanet atmospheres parallels our understanding of Earth’s long history. Earth could be the key to our broadening and accelerating search for life.
“Unravelling the details of Earth’s complex biogeochemical history and its relationship with remotely observable spectral signals is an important consideration for instrument design and our own search for life in the Universe,” the authors write.
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