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Currently, 5,788 exoplanets have been confirmed in 4,326 star systems, while thousands more candidates await confirmation. So far, the vast majority of these planets have been gas giants (3,826) or Super-Earths (1,735), while only 210 have been “Earth-like” – meaning rocky planets similar in size and mass to Earth. What’s more, the majority of these planets have been discovered orbiting within M-type (red dwarf) star systems, while only a few have been found orbiting Sun-like stars. Nevertheless, no Earth-like planets orbiting within a Sun-like star’s habitable zone (HZ) have been discovered so far.

This is largely due to the limitations of existing observatories, which have been unable to resolve Earth-sized planets with longer orbital periods (200 to 500 days). This is where next-generation instruments like the ESA’s PLAnetary Transits and Oscillations of stars (PLATO) mission come into play. This mission, scheduled to launch in 2026, will spend four years surveying up to one million stars for signs of planetary transits caused by rocky exoplanets. In a recent study, an international team of scientists considered what PLATO would likely see based on what it would see if observing the Solar System itself.

The study was led by Andreas F. Krenn, a PhD student at the Space Research Institute at the Austrian Academy of Sciences. He was joined by researchers from the Observatoire Astronomique de l’Université de Genève, Aix Marseille University, the Columbia Astrophysics Laboratory, the Leibniz Institute for Astrophysics Potsdam (AIP), the Institute of Astronomy at KU Leuven, the National Center for Atmospheric Research, and the Kanzelhöhe Observatory for Solar and Environmental Research at the University of Graz. The paper that describes their research recently appeared in the journal Astronomy & Astrophysics.

As they note in their study, an Earth-like planet orbiting within the HZ of a G-type star would be a prime target to search for biosignatures. These include oxygen gas, carbon dioxide, methane, ammonia, and water vapor in the atmosphere, as well as indications of photosynthesis taking place on the surface – i.e., the vegetation red edge (VRE). This has been very difficult for telescopes as Earth-like planets are more likely to orbit closer to Sun-like stars, making it difficult to obtain data on their atmospheres using either Direct Imaging or transmission spectra.

This latter technique involves the Transit Photometry (or the Transit Method), where astronomers measure the light curve of distant stars for periodic dips in brightness. These are often the result of exoplanets passing in front of the star (i.e., transiting) relative to the observer. To date, the vast majority of exoplanets – more than 4,300, or 74.5% – have been confirmed using this method. When the conditions are right, astronomers sometimes observe light as it passes through the exoplanet’s atmosphere, which is then studied using spectrometers to determine its chemical composition.

But as Krenn told Universe Today via email, this has been a significant challenge for astronomers:

“The main difficulty is the small signals that such planets generate. For example, the radial velocity amplitude of the Earth is roughly 0.1 m/s. This is about the speed of a giant Galapagos tortoise. That means that if a distant observer would like to see the Sun’s motion around the common center of mass of the Earth-Sun system, they would need to see the Sun move at the speed of a giant Galapagos tortoise from light years away.

“Similarly, the relative amount emitted by the Sun that is blocked by the Earth when a distant observer observes the Earth transiting across the solar disk is 84 parts per million, which is 0.0084%. So a distant observer would need to see the light of that star being dimmed by 0.0084% in order to detect Earth.”

Moreover, Krenn added that existing spectrographs have not been precise enough to measure such small signals. Whereas exoplanet-hunting missions like the ESA’s CHaracterising ExOPlanets Satellite (CHEOPS) have managed to obtain spectra from transiting exoplanets, several transit events were needed to achieve this precision. This isn’t easy when dealing with planets like Earth with longer orbital periods that fit into the 200- to 500-day range. Lastly, instrumental effects and stellar variability can be orders of magnitude larger than a planetary signal.

This is expected to change considerably with the ESA’s next-generation PLAnetary Transits and Oscillations of stars (PLATO) space telescope. This mission will rely on a multi-telescope approach involving 26 cameras, including 24 “normal” cameras organized in 4 groups and 2 “fast” cameras for bright stars. These instruments will continuously observe the same area of the sky for at least two years to detect transit signals by Earth-like planets around solar analogs. Said Krenn:

“PLATO’s photometric instrument will be precise enough to detect the transit of an Earth-like planet orbiting a solar-like star using a single transit event. Supported by its stellar variability program and ground-based follow-up campaign, we will hopefully be able to correctly account for the influences of noise sources. In short, PLATO will utilize the interdisciplinary of exoplanet science on a whole new level. It will combine high-precision photometry, up-to-date data analysis tools, a dedicated stellar variability program, and its own ground-based follow-up campaign.

“Experts from all of these fields will work together to try and make the detection of these tiny planetary signals possible. Additionally, PLATO will also utilize a special observing strategy that allows it to observe thousands of stars a the same time and produce 2 years of almost continuous photometric data for each of them.”

ESA’s trifecta of dedicated exoplanet missions – Cheops, Plato, and Ariel – will also be complemented by the James Webb Space Telescope mission Credit: ESA

To assess what PLATO might see when observing thousands of Sun-like stars for Earth analogs, the team modeled the impact of short-term solar variability using the Sun as a proxy. This consisted of using data obtained by the Helioseismic and Magnetic Imager (HMI) aboard NASA’s Solar Dynamics Observatory, which has been observing the Sun continuously since 2010. Using 88 consecutive days of HMI observations, they injected Earth-like transit signals and noise models into the data and simulated PLATO observations for five scenarios and five stellar magnitudes.

Their results showed that transit signals can be reliability detected with a high signal-to-noise ratio for bright targets, but still very likely for faint ones. They further found that the PLATO mission has a good shot at precisely and accurately measuring the size of Earth-like planets, one of its chief objectives. As Krenn explained, these findings could help inform the PLATO mission and assist in finding the signals of Earth analogs amid all the noise, though much work needs to be done to ensure all sources of noise are accounted for:

“In our analysis, we focused only on the effects of short-term variability, which we know is only one of many noise sources that will affect PLATO observations. We have seen that even correctly accounting for this single type of noise can be challenging. The final analysis of PLATO data will need to combine a variety of complex noise models simultaneously to correctly account for all of the different noise sources. I think our research has shown that we need to have an in-depth understanding of individual noise sources but, at the same time, also need to learn how to best combine all of the individual models.”

Other next-generation instruments, such as the James Webb Space Telescope (JWST), the Atmospheric Remote-sensing Infrared Exoplanet Large-survey (ARIEL) telescope, and the Nancy Grace Roman Space Telescope will also allow for the discovery and characterization of countless exoplanets using the Direct Imaging Method. Along with upcoming ground-based observatories, these missions will rely on advanced optics, coronographs, and spectrometers to locate more Earth analogs and analyze their atmospheres and surfaces for evidence of life. Soon enough, astronomers will do away with terms like “potentially habitable” and be able to say with confidence that an exoplanet is “habitable” (and perhaps even “inhabited”!)

Further Reading: Astronomy & Astrophysics

The post Could the ESA’s PLATO Mission Find Earth 2.0? appeared first on Universe Today.

Most galaxies are thought to play host to black holes. At the center of Centaurus A, a galaxy 12 million light years away, a jet is being fired out into space. Images that have been captured by NASA’s Chandra X-ray observatory show that the high energy particles have struck a nearby object creating a shockwave. The target is thought to be a giant star, maybe even a binary system, where the collision and turbulence has increased density in the region.

A black hole is an object and a region of space! At the centre is the singularity, a single point object where density is infinite and all the laws of physics seem to fail us. Surrounding the singularity is a region of space where the velocity needed to escape the singularity’s gravitational pull is in excess of the speed of light. The boundary between the region of space dominated by the singularity and dare I say ‘normal space’ is known as the event horizon. Collectively we call this phenomenon a black hole. 

3D rendering of a rapidly spinning black hole’s accretion disk and a resulting black hole-powered jet. Credit: Ore Gottlieb et al. (2024)

Black holes at the centre of galaxies are usually supermassive, often millions to billions of times more massive than the Sun. They exert an immense pull of gravity which has an impact on the motion of stars and gas within their host galaxy. Matter getting drawn toward a black hole by its immense gravitational pull forms into an accretion disk surrounding the black hole. Here the gravitational force is high and so it heats the incoming material. The material falling in to the black hole gets heated to extreme temperatures generating strong electromagnetic fields. The fields can accelerate the particles outward forming into the familiar jet structure. 

A simulation of a galaxy’s ‘heart and lungs’ at work is pictured inset on an artist’s impression of bi-polar jets of gas originating from a supermassive black hole at the centre of a galaxy. Credit ESA/Hubble, L. Calçada (ESO) / C Richards/MD Smith/University of Kent Licence type Attribution (CC BY 4.0)

Our own Milky Way galaxy has a black hole at the centre as does the galaxy Centaurus A. At a distance of 12 million light years, it’s relatively in our back yard! A team of astronomers have turned NASA’s Chandra X-Ray observatory on Centaurus A and found the jet of its black hole striking an unidentified object. The team of astronomers discovered that parts of the jet are moving at speeds close to the speed of light. They also detected the region where it seemed to be striking something, appearing as a bright source of X-rays in the image, known as C4. 

This is Centaurus A, the nearest galaxy with an active nucleus. The active nucleus is where a supermassive black hole resides. One of the questions in astrophysics is how SMBHs grow so large, and the JWST should help answer that question. Image Credit: By ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray)

At a distance of 12 million light years, it’s too far away for the object to be seen but the team theorise that it’s either a massive star or one with a companion star. It’s thought that the X-rays are caused by a collision between the particles in the jet and the stellar wind from the star. The impact from the collision can be the generation of turbulence which leads to an increase in the density of gas in the jet, driving the X-ray emissions that have been detected. 

In the deepest image from Chandra, at the C4 source there appeared a strange V-shaped structure. The shape is not fully understood but analysis revealed the arms of the ‘V’ are at least 700 light years long! The results were published in the Astrophysical Journal by lead author David Bogensberger from the University of Michigan and a team of US astronomers. 

Source : Black Hole Jet Stumbles Into Something in the Dark

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More and more people under 50 have been diagnosed with bowel cancer in different parts of the world over the past few decades

On 24 December, the Parker Solar Probe will be the closest human-made object ever to a star, taking unprecedented measurements of the sun

Just a few months after the previous record was set, a start-up called Quantinuum has announced that it has entangled the largest number of logical qubits – this will be key to quantum computers that can correct their own errors

Do we have a planetary bias when it comes to understanding where life can perpetuate? It’s only natural that we do. After all, we’re on one.

However, planets may not be necessary for life, and a pair of scientists from Scotland and the USA are inviting us to reconsider the notion.

We focus on planets as habitats for life because they meet the conditions necessary for life to survive. Liquid water, the right temperature and pressure to keep it in a liquid state, and protection from harmful radiation are the primary requirements for photosynthetic life. But what if other environments, even ones maintained by organisms themselves, can also provide these necessities?

In new research published in the journal Astrobiology, researchers point out that ecosystems could generate and sustain the conditions necessary for their own survival without requiring a planet. The paper is titled “Self-Sustaining Living Habitats in Extraterrestrial Environments.” The authors are Robin Wordsworth, Professor of Earth and Planetary Sciences at Harvard, and Charles Cockell, Professor of Astrobiology in the School of Physics and Astronomy at the University of Edinburgh.

“Standard definitions of habitability assume that life requires the presence of planetary gravity wells to stabilize liquid water and regulate surface temperature,” they write. “Here the consequences of relaxing this assumption are evaluated.”

Wordsworth and Cockell write that biologically generated barriers and structures can mimic the planetary conditions that enable life without the planet. They can let light in for photosynthesis while blocking UV light. They can also prevent volatile loss while in a vacuum and maintain the temperature and pressure range required for water to remain in a liquid state.

“Biologically generated barriers capable of transmitting visible radiation, blocking ultraviolet, and sustaining temperature gradients of 25-100 K and pressure differences of 10 kPa against the vacuum of space can allow habitable conditions between 1 and 5 astronomical units in the Solar System,” they write.

“To understand the constraints on life beyond Earth, we can start by reviewing why our home planet is a good habitat for life in the first place,” write the authors.

The Earth is our only example of a biosphere, but it’s possible that extraterrestrial life could create its own self-sustaining habitat. Image Credit: ESA/Meteosat

Earth does more than just provide liquid water and protection from radiation. It’s an entire system with layers of interacting complexity. The planet’s surface is exposed to an easily accessible source of energy from the Sun that drives the whole biosphere. The elements we think of as essential for life are available, though sometimes limited: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorous, and Sulfur. They cycle through the biosphere via volcanism and plate tectonics and become available again. Earth is also oxidizing in the atmosphere and on the surface and reducing in other regions like sediments and the deep subsurface. This allows for “the exploitation of redox gradients for metabolic purposes,” the authors explain.

Those conditions don’t exist elsewhere. Astrobiology targets the solar system’s frozen moons because of their warm, salty oceans. But do they have nutrient cycles?

Low-mass objects in the outer Solar System have ample surface area, but the Sun’s energy is weak. They’re unlikely to be able to hold onto their atmospheres, so the correct pressure and temperature for liquid water are out of reach. They’re also unprotected from UV radiation and cosmic rays.

“To persist beyond Earth,” the authors write, “any living organism must modify or adapt to its environment enough to surmount these challenges.”

The authors write that biological materials here on Earth can already do that. It’s plausible that ecosystems could develop the conditions for their own survival, and if photosynthetic life can do it in the vacuum of space, then so could we. It would be a major benefit for human space exploration.

It starts with water, and when it comes to liquid water, scientists refer to its triple point. A triple point is a thermodynamic reference point that explains phase transitions and how water behaves under different pressures and temperatures. “The minimum pressure required to sustain liquid water is the triple point: 611.6 Pa at 0?C (273 K),” the researchers explain. That number rises to a few kPa between 15 to 25 Celsius.

Cyanobacteria can grow with air headspace pressures of 10 kPa so long as the light, temperature and pH are in the right ranges. The question is, do any living things that we know of generate walls that can maintain 10kPa?

“Internal pressure differences of order 10 kPa are easily maintained by biological materials and in fact common in macroscopic organisms on Earth,” the authors write. “The blood pressure increase from the head to the feet of a 1.5-m tall human is around 15 kPa.” Seaweed can also sustain internal float nodule pressures of 15-25 kPa by releasing CO2 from photosynthesis.

Ascophyllum nodosum grows egg-shaped air bladders that sustain internal pressure. Image Credit: By Dozens at en.wikipedia, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=10867583

Temperature is the next consideration when it comes to liquid water. Earth maintains its temperature through the atmospheric greenhouse effect. But small rocky bodies, for example, are unlikely to replicate this. “Hence, a biologically generated habitat must achieve the same effect via solid-state physics,” write the authors.

Incoming energy and outgoing energy need to be balanced, and some organisms on Earth have evolved to maintain this balance. “Saharan silver ants, for example, have evolved the ability to enhance both their surface near-infrared reflectivity and their thermal emissivity, allowing them to survive in ambient temperatures above the range of all other known arthropods,” Wordsworth and Cockell write. It allows them to survive by foraging in the heat of the day when predators must stay out of the Sun.

Saharan Silver Ants devouring a camel tick. Image Credit: By Bjørn Christian Tørrissen – Own work by uploader, http://bjornfree.com/galleries.html, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=17131784

Humans have made silica aerogels with extremely low density and thermal conductivity. While there are no direct biological equivalents, the authors write that “many organisms do exist in nature that produce complex silica structures.”

In fact, some diatoms can produce silica structures by manipulating silica particles smaller than those used in our manufacturing processes. Aerogels manufactured from organic materials have similar characteristics to artificial ones. “Given this, it is plausible that highly insulating materials could be produced artificially from biogenic feedstocks or even directly by living organisms,” the authors write.

This figure from the research shows two different geometries for aerogel-type habitats: (a) a spherically symmetric geometry and (b) a Sun-facing geometry. Blue color represents translucent solid-state greenhouse material of thickness a few cm, while grey represents a thicker layer of opaque, thermally insulating material. Image Credit: Wordsworth and Cockell, 2024

The authors calculated that these types of structures could maintain the right temperature and pressure to maintain liquid water.

“As can be seen, maintaining internal temperature at 288 K is possible for a wide range of orbital distances,” they explain. “This calculation assumes a free-floating habitat, but similar considerations apply to habitats on the surface of an asteroid, moon or planet.”

This figure shows how passive solid-state warming can enable habitability beyond Earth. It shows the thermal conductivity of a solid-state greenhouse layer vs. orbital distance, given a habitat interior temperature of 288 K. Red and blue curves show cases assuming spherically symmetric and Sun-facing geometry, respectively. The green shaded area indicates typical thermal conductivities for translucent silica and organic aerogels reported in other research. Image Credit: Wordsworth and Cockell, 2024.

Volatile loss is another problem. A habitat that can’t hold onto its atmosphere can’t maintain the temperature and pressure necessary for liquid water. “All materials have some permeability to atoms and small molecules, and over long timescales, the vacuum of space represents an essentially permanent sink for volatile species,” the authors explain.

This can be solved by the same barriers that maintain pressure and temperature. “Inhibition of volatile escape would be most easily achieved by the same part of the habitat wall responsible for maintaining the pressure differential necessary to stabilize liquid water,” write the authors.

The authors also consider the effects of UV radiation. Radiation can be deadly, but there are examples of life here on Earth that have evolved to figure it out. “However, it is easily blocked by compounds such as amorphous silica and reduced iron, which attenuate UV in silicified biofilms and stromatolites today without blocking the visible radiation needed for photosynthesis,” they write.

The availability of solar energy for photosynthesis likely isn’t much of a barrier in many parts of the Solar System. The authors point out that Arctic algae grows in extremely weak light under the ice.

Some type of nutrient cycle would be required, just like on Earth. “Long-term, an additional consideration is the ability of a closed-loop ecosystem to process waste products such as recalcitrant organic matter and to sustain internal redox gradients,” explain the authors. The extreme heat in Earth’s interior gets it done, but without those extremes, “a fully closed-loop ecosystem in space would require some internal compartmentalization to establish chemical gradients and specialist biota capable of breaking down recalcitrant waste products,” they write.

In their paper, the authors cover other factors like cell size and the factors that limit the size of unicellular organisms and larger, more complex organisms. They conclude that fully autonomous living habitats can’t be ruled out. “Nonetheless, a fully autonomous system capable of regeneration and growth is apparently not prohibited by any physical or chemical constraints and is therefore interesting to consider a little further,” they write.

It’s possible as long as the system can regenerate its walls. The authors point out that existing photosynthetic life can already produce amorphous silica and organic polymers. These materials could serve as walls and at least show that there’s a pathway where organisms could evolve to create habitat walls. “A more autonomous living habitat would be able to grow its own wall material, just as plant cells regenerate their own walls on the micrometre scale,” they explain.

We tend to think that if life exists elsewhere, it follows the same evolutionary pathway as it did here on Earth, but that may not be true. “Because the evolution of life elsewhere may have followed very different pathways from on Earth, living habitats could also exist outside traditional habitable environments around other stars, where they would have unusual but potentially detectable biosignatures,” the authors write.

The authors ask, “Could the kind of biological structures we discuss here evolve naturally, without intelligent intervention?” They argue that non-sentient life can sustain all of the conditions necessary to survive in extraterrestrial environments.

“Life on Earth has not yet done this, although it has certainly adapted to an increasingly wide range of environmental conditions over time,” they conclude. “Investigating the plausibility of different evolutionary pathways for life under alternative planetary boundary conditions will be an interesting topic for future research.”

The post Does Life Really Need Planets? Maybe Not appeared first on Universe Today.

Scientists have leveraged fundamental features of chemical building blocks to transform chemical reaction analysis from minutes to milliseconds.

Stunning new photographs by a team of astronomers have revealed a newly forming galaxy that looks remarkably similar to a young Milky Way. The extraordinary images give us an unprecedented picture of what our own galaxy might have looked like when it was being born.

Canada should focus on building mass utility-scale solar mega-projects to kickstart its green energy transition, according to a new report. The recommendation comes from a new article which looks at the current state of solar power and compares the benefits of both mass-scale projects and smaller, decentralized approached like individual homes and commercial buildings installing their own solar panels.

A new study highlights a hidden challenge of using AI in medical imaging research -- the phenomenon of highly accurate yet potentially misleading results known as 'shortcut learning.' The researchers analyzed thousands of knee X-rays and found that AI models can 'predict' unrelated and implausible traits such as whether patients abstained from eating refried beans or beer. While these predictions have no medical basis, the models achieved high levels of accuracy by exploiting subtle and unintended patterns in the data.

An interdisciplinary team has created tiny bubble-like microrobots that can deliver therapeutics right where they are needed and then be absorbed by the body.

An interdisciplinary team has created tiny bubble-like microrobots that can deliver therapeutics right where they are needed and then be absorbed by the body.

Researchers developed a non-invasive imaging technique that enables laser light to penetrate deeper into living tissue, capturing sharper images of cells. This could help clinical biologists study disease progression and develop new medicines.

We know that interstellar objects occasionally visit our solar system. So far, we have only discovered two interstellar objects (ISOs), but that’s mainly because we can only distinguish them from solar system bodies by their orbital motion, and that takes a series of observations over time. The two we have discovered, ?Oumuamua and Borisov, were only noticed because they had highly unusual orbits that moved through the inner solar system. But when sky survey telescopes such as the Vera Rubin Observatory come online, we will likely find new interstellar objects all the time. It’s estimated that several ISOs enter the solar system every year, and there could be hundreds of them passing by at any given time. But that raises an interesting question about how these objects arrive. Do they enter our solar system randomly from all directions, or do they appear in clusters a few at a time?

That is the question addressed in a new paper on the *arXiv*. It looks at how streams of interstellar bodies might escape a solar system and how they would then move through the Milky Way. While it is always possible for a random asteroid or comet to have a random flyby near a large planet that tosses it out of a system, most interstellar bodies would occur during the tumultuous early period of a star system when it is cleared of debris. In our solar system this process created the Oort cloud surrounding the Sun, which likely occurred in other systems. So star systems likely create bursts of ISOs, which then stream through the Milky Way until they encounter another star system.

Simulated streams of ISOs in the Milky Way. Credit: Forbes, et al

To study all this, the team started with simulated bursts and then modeled how the resulting streams would evolve. Based on the distribution and typical ages of stars in our region of the Milky Way, they could then simulate streams that might intersect the Sun’s path through the galaxy. They found that the Sun likely intersects with streams regularly, which would give us plenty of interstellar visitors. They also found that just as Earth experiences meteor showers as it passes through the remnant debris streams of comets, the Sun would experience bursts of interstellar objects as it passes through a stream. With the abilities of Rubin and other observatories, we should be able to identify ISOs that are “siblings,” having originated from the same star system. Over time, this could give us a better idea of the composition and diversity of planetary systems. We may even be able to pinpoint the origin of sibling ISOs to a particular star.

One final interesting aspect of these interstellar streams is their overall appearance. Several of the authors of this work are from Aotearoa New Zealand, and they noticed that the simulated patterns have a braided appearance similar to the braided rivers such as Rakaia on the South Island. So they named these interstellar streams he awa whiria, which means the braiding rivers in te reo M?ori, as an homage to that region and its people. It’s a nice reminder of our humanity and the connection between the world around us and the sky above.

Reference: Forbes, John C., et al. “He awa whiria: the tidal streams of interstellar objects.” arXiv preprint arXiv:2411.14577 (2024).

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From a fish with a tiny brain to the world’s oldest cheese, we have reported on plenty of strange and unusual science discoveries this year. Challenge yourself and see what you can remember in this fiendish set of questions from our quizmaster Bethan Ackerley

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