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Do Red Dwarfs Provide Enough Sunlight for Plants to Grow? – Universe Today

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To date, 5,250 extrasolar planets have been confirmed in 3,921 systems, with another 9,208 candidates awaiting confirmation. Of these, 195 planets have been identified as “terrestrial” (or “Earth-like“), meaning that they are similar in size, mass, and composition to Earth. Interestingly, many of these planets have been found orbiting within the circumsolar habitable zones (aka. “Goldilocks zone”) of M-type red dwarf stars. Examples include the closest exoplanet to the Solar System (Proxima b) and the seven-planet system of TRAPPIST-1.

These discoveries have further fueled the debate of whether or not these planets could be “potentially-habitable,” with arguments emphasizing everything from tidal locking, flare activity, the presence of water, too much water (i.e., “water worlds“), and more. In a new study from the University of Padua, a team of astrobiologists simulated how photosynthetic organisms (cyanobacteria) would fare on a planet orbiting a red dwarf. Their results experimentally demonstrated that oxygen photosynthesis could occur under red suns, which is good news for those looking for life beyond Earth!

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The study was led by Nicoletta La Rocca and Mariano Battistuzzi, biologists from the Center for Space Studies and Activities (CISAS) at the University of Padua. They were joined by researchers from the National Council of Research of Italy’s Institute for Photonics and Nanotechnologies (CNR-IFN), the National Institute for Astrophysics (INAF), and the Astronomical Observatory of Padua. The paper that describes their findings was published on February 7th, 2023, in the Frontiers of Plant Science.

The “pale orange dot.” Artist’s impression of what early Earth would have looked like. Credit: NASA/Goddard Space Flight Center/Francis Reddy

The subject of M-type stars, photosynthesis, and the implications for astrobiology has been explored at length in recent decades. Not only are red dwarfs the most common type of star in the Universe, accounting for 75% of stars in the Milky Way alone. Recent surveys have shown they are also very good at forming rocky planets that orbit within the parent star’s habitable zone (in many cases, tidally locked with their stars). Given the unstable nature of red dwarfs, their tendency to flare, and other factors, the jury is still out on whether or not they could support life – especially in their early phases. As Dr. Battistuzzi told Universe Today via email:

“M-dwarfs can profoundly change their activity depending on their stage of evolution. 25% of early-life M-dwarfs release X-rays and UV through flares and chromospheric activity. Instead, quiescent stars emit little UV radiation and have no flares. Planets orbiting around M-dwarfs often receive high doses of these kinds of radiation during stellar flares, changing rapidly the radiation environment on the surface and possibly eroding the ozone shield, if present, as well as part of the atmosphere.

“However, it has been pointed out that these planets could remain habitable. Atmospheric erosion could be avoided through a strong magnetic field or with thick atmospheres. Also, in addition to this, possible organisms could develop UV-protecting pigments and DNA repair mechanisms as happens on Earth or develop in subsurface niches, underwater or under the ice, where radiation is less intense.”

On Earth, life is theorized to have emerged during the Archean Eon (ca. 4 billion years ago) in the form of simple, single-celled (prokaryote) bacteria. Earth’s atmosphere was still largely composed of carbon dioxide, methane, and other volcanic gases at this time. Between 3.4 and 2.9 billion years ago, the first photosynthetic organisms – green-blue microbes called cyanobacteria – began flourishing in Earth’s oceans. These organisms metabolized carbon dioxide with water and sunlight to create gaseous oxygen (O2), eventually leading to more complex, multi-celled organisms (eukaryotes).

Artist’s impression of the Archean Eon. Credit: Tim Bertelink

Hence the concern regarding young red dwarf suns and their rocky planets. These dimmer, cooler stars emit the majority of their radiation in the red and infrared wavelengths (lower energy than the yellow light of the Sun peaks). As a result, scientists have speculated that additional photons would be needed to achieve excitation potentials comparable to those needed for photosynthesis on Earth. For their study, La Rocca and Battistuzzi sought to determine experimentally if this was the case. According to Battistuzzi, this consisted of subjecting cyanobacteria to different wavelengths of light and monitoring the bacteria’s growth:

“We exposed a couple of cyanobacteria to a simulated M-dwarf light spectrum and measured their growth, acclimation responses (for example, the changes in the pigment composition and the organization of the photosynthetic apparatus, crucial to absorbing light and converting it into sugars), and oxygen production capabilities under this light spectrum. We compared these data to 2 different control conditions: a monochromatic far-red light and a solar light spectrum.”

The experiment utilized two types of cyanobacteria. This included Chlorogloeopsis fritschii, a small group of cyanobacteria capable of synthesizing special pigments (chlorophyll d and f) that are able to absorb far-red light. Unlike most other photosynthetic organisms (like plants), this gives this strain the ability to grow and produce oxygen using far-red light alone or in addition to visible light. The second strain, Synechocystis sp., is a broader group of freshwater cyanobacteria that cannot utilize far-red light alone for photosynthesis and needs visible light.

“The monochromatic far-red light was used as a control to ensure different responses of the far-red utilizing cyanobacterium and the non-far utilizing one: the first should grow in far-red, and the second one should not,” added Battistuzzi. “The simulated solar light spectrum was used as a control to check the growth, acclimation responses, and oxygen production in optimal conditions (terrestrial organisms evolved under the Sun’s spectrum, so they are adapted to it).”

Three of the TRAPPIST-1 planets – TRAPPIST-1e, f, and g – dwell in their star’s so-called “habitable zone.” Credit: NASA/JPL

As they indicate in their study, the results were surprisingly encouraging. Both cyanobacteria grew at a similar rate under the red dwarf and Solar light conditions. This was impressive, considering that visible light is rather scarce in the M-type stellar spectrum. In the case of C. fritschii, the results could be explained by its capability of synthesizing the necessary pigments to harvest far-red light and its ability to harness visible light. While Synechocystis sp. did not grow under far-red light alone, it could also grow at a similar rate to C. fritschii when exposed to both. While the exact cause is not certain, Battistuzzi and La Rossa have some theories:

“This could be explained by recent studies on plants showing that far-red light just helps oxygenic photosynthesis when in combination with visible light, while instead is poorly utilized when provided alone (as demonstrated in this work by Synechocystis sp., which could not grow under this only light source).

“The acclimations of both cyanobacteria moreover led to efficient O2 evolution under the M-dwarf light spectrum. This shows the potentiality of cyanobacteria to utilize light regimes that could arise on tidally locked planets orbiting the Habitable Zone of M-dwarf stars, and also their potential in producing O2 biosignatures detectable from remote.”

In a previous study conducted in 2021, La Rocca, Battistuzzi, and their teammates conducted a similar experiment where they studied the growth and acclimation of cyanobacteria. This study was led by Riccardo Claudi of the Astronomical Observatory of Padua (INAF-OAPD), a co-author of the current paper. For this experiment, the team relied on solid media to cultivate cyanobacteria as biofilms, which allowed them to obtain results more rapidly but limited the amount and the type of experiments they could conduct.

Artist’s impression of a water world, where half of its mass consists of water. Just like our Moon, the planet is bound to its star by tidal forces and always shows the same face to its host star. Credit: Pilar Montañés

This time, the cyanobacteria were cultivated in liquid media, which yielded more samples. This, in turn, allowed far more detailed examinations of the growth, acclimation processes, and oxygen evolution of cyanobacteria exposed to different light conditions. The implications of these latest experiments and what they revealed are potentially groundbreaking. According to Battistuzzi, this includes a new understanding under which photosynthesis can occur, better prospects for red dwarf habitability, and new opportunities for detected biotic oxygen in exoplanet atmospheres:

“Even if the visible light in the M-dwarf spectrum is very low, it can still be utilized by some oxygenic photosynthetic organisms efficiently. This highlights the importance of taking into account the huge diversity of oxygenic photosynthetic organisms, which not only comprise plants but also basal plants, and microalgae, down to the simplest cyanobacteria.

“It is also important to consider how the new findings demonstrate the role of far-red light in helping photosynthetic performance and the growth of all photosynthetic organisms (higher plants included). If life evolved oxygenic photosynthesis on an exoplanet orbiting the habitable zone of an M-dwarf, this process could be far more similar to what happens on Earth than previously anticipated.”

“If oxygenic photosynthesis evolved in M-dwarf’s exoplanets, with the right conditions, oxygen could, in theory, accumulate in their atmospheres, as happened on Earth billions of years ago during the Great Oxidation Event, becoming a permanent component. This would allow astronomers to detect such biologically produced oxygen, a biosignature, in the atmosphere and infer from that the presence of life from remote.”

Artist’s conception of a rocky Earth-mass exoplanet like Wolf 1069 b orbiting a red dwarf star. If the planet has retained its atmosphere, chances are high that it would feature liquid water and habitable conditions over a wide area of its dayside. Credit: NASA/Ames Research Center/Daniel Rutter

This last implication is especially significant, as astronomers and astrobiologists have explored the possibility that when it comes to red dwarfs, oxygen might not be the smoking gun we tend to think it is. Red dwarfs have an extended pre-main sequence phase (roughly 1 billion years), which means that planets orbiting in what will eventually become their habitable zones would be exposed to elevated radiation. This could trigger a runaway greenhouse effect where water is evaporated and broken down by radiation exposure into hydrogen and oxygen (photolysis).

The hydrogen gas would then be lost to space while the oxygen would be retained as a thick abiotic oxygen atmosphere. Such atmospheres would be inherently hostile to photosynthetic bacteria and other terrestrial organisms that existed when the Earth was young. In short, what is considered a leading biosignature and indicator of life could actually be an indication that a planet is sterile. But as Battistuzzi adds, there is plenty of uncertainty here, and more research is needed before any conclusions can be drawn:

“Of course, these are big ifs. It is not a guarantee that life would evolve even if habitability conditions are met on an exoplanet orbiting an M-dwarf, and it is not a guarantee that life would evolve oxygenic photosynthesis at all, as it could also evolve anoxygenic photosynthesis, a kind of photosynthesis which still uses light but does not produce oxygen as a by-product.”

Further Reading: arXiv

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The total solar eclipse in North America could shed light on a persistent puzzle about the sun – Phys.org

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The total solar eclipse in North America could shed light on a persistent puzzle about the sun

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The path of eclipse totality passes through Mexico, the US and Canada. Credit: NASA’s Scientific Visualization Studio

A total solar eclipse takes place on April 8 across North America. These events occur when the moon passes between the sun and Earth, completely blocking the sun’s face. This plunges observers into a darkness similar to dawn or dusk.

During the upcoming eclipse, the path of totality, where observers experience the darkest part of the moon’s shadow (the umbra), crosses Mexico, arcing north-east through Texas, the Midwest and briefly entering Canada before ending in Maine.

Total solar eclipses occur roughly every 18 months at some location on Earth. The last that crossed the US took place on August 21 2017.

An international team of scientists, led by Aberystwyth University, will be conducting experiments from near Dallas, at a location in the path of totality. The team consists of Ph.D. students and researchers from Aberystwyth University, Nasa Goddard Space Flight Center in Maryland, and Caltech (California Institute of Technology) in Pasadena.

There is valuable science to be done during eclipses that is comparable to or better than what we can achieve via space-based missions. Our experiments may also shed light on a longstanding puzzle about the outermost part of the sun’s atmosphere—its corona.

The sun’s intense light is blocked by the moon during a total solar eclipse. This means that we can observe the sun’s faint corona with incredible clarity, from distances very close to the sun, out to several solar radii. One radius is the distance equivalent to half the sun’s diameter, about 696,000km (432,000 miles).

Measuring the corona is extremely difficult without an eclipse. It requires a special telescope called a coronagraph that is designed to block out direct light from the sun. This allows fainter light from the corona to be resolved. The clarity of eclipse measurements surpasses even coronagraphs based in space.

We can also observe the corona on a relatively small budget, compared to, for example, spacecraft missions. A persistent puzzle about the corona is the observation that it is much hotter than the photosphere (the visible surface of the sun). As we move away from a hot object, the surrounding temperature should decrease, not increase. How the corona is heated to such high temperatures is one question we will investigate.

We have two main scientific instruments. The first of these is Cip (coronal imaging polarimeter). Cip is also the Welsh word for “glance,” or “quick look.” The instrument takes images of the sun’s corona with a polariser.

The light we want to measure from the corona is highly polarized, which means it is made up of waves that vibrate in a single geometric plane. A polarizer is a filter that lets light with a particular polarization pass through it, while blocking light with other polarizations.

The Cip images will allow us to measure fundamental properties of the corona, such as its density. It will also shed light on phenomena such as the solar wind. This is a stream of sub-atomic particles in the form of plasma—superheated matter—flowing continuously outward from the sun. Cip could help us identify sources in the sun’s atmosphere for certain solar wind streams.

Direct measurements of the magnetic field in the sun’s atmosphere are difficult. But the eclipse data should allow us to study its fine-scale structure and trace the field’s direction. We’ll be able to see how far magnetic structures called large “closed” magnetic loops extend from the sun. This in turn will give us information about large-scale magnetic conditions in the corona.

The second instrument is Chils (coronal high-resolution line spectrometer). It collects high-resolution spectra, where light is separated into its component colors. Here, we are looking for a particular spectral signature of iron emitted from the corona.

It comprises three , where light is emitted or absorbed in a narrow frequency range. These are each generated at a different range of temperatures (in the millions of degrees), so their relative brightness tells us about the coronal temperature in different regions.

Mapping the ‘s temperature informs advanced, computer-based models of its behavior. These models must include mechanisms for how the coronal plasma is heated to such high temperatures. Such mechanisms might include the conversion of magnetic waves to thermal plasma energy, for example. If we show that some regions are hotter than others, this can be replicated in models.

This year’s eclipse also occurs during a time of heightened solar activity, so we could observe a coronal mass ejection (CME). These are huge clouds of magnetized plasma that are ejected from the sun’s atmosphere into space. They can affect infrastructure near Earth, causing problems for vital satellites.

Many aspects of CMEs are poorly understood, including their early evolution near the sun. Spectral information on CMEs will allow us to gain information on their thermodynamics, and their velocity and expansion near the sun.

Our eclipse instruments have recently been proposed for a space mission called moon-enabled solar occultation mission (Mesom). The plan is to orbit the moon to gain more frequent and extended eclipse observations. It is being planned as a UK Space Agency mission involving several countries, but led by University College London, the University of Surrey and Aberystwyth University.

We will also have an advanced commercial 360-degree camera to collect video of the April 8 eclipse and the observing site. The video is valuable for public outreach events, where we highlight the work we do, and helps to generate public interest in our local star, the sun.

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How the 2024 total solar eclipse is different than the 2017 eclipse



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Mar 30: An Australian Atlantis and other lost landscapes, and more… – CBC.ca

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Quirks and Quarks54:00An Australian Atlantis and other lost landscapes, and more…


On this week’s episode of Quirks & Quarks with Bob McDonald: 

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Archaeologists identify a medieval war-horse graveyard near Buckingham Palace 

Quirks and Quarks9:04Archaeologists identify a medieval war-horse graveyard near Buckingham Palace

We know knights in shining armour rode powerful horses, but remains of those horses are rare. Now, researchers studying equine remains from a site near Buckingham Palace have built a case, based on evidence from their bones, that these animals were likely used in jousting tournaments and battle. Archaeologist Katherine Kanne says the bone analysis also revealed a complex, continent-crossing medieval horse trading network that supplied the British elite with sturdy stallions. This paper was published in Science Advances.

University of Exeter researchers analyzed horse skeletons found near Buckingham Palace and conducted isotope tests on teeth to find out more about the animals’ origins. (University of Exeter)

In an ice-free Arctic, polar bears are dining on duck eggs — and gulls are taking advantage

Quirks and Quarks9:22In an ice-free Arctic, Polar bears are dining on duck eggs — and gulls are taking advantage

Researchers using drones to study ground-nesting birds in the Arctic have observed entire colonies being devastated by marauding polar bears that would normally be out on the ice hunting seals, except the ice isn’t there. What’s more, now they’re enabling a second predator — hungry gulls that raid the nests in the bears’ wake. Andrew Barnas made the observations of this “gull tornado” by following around polar bears in East Bay Island in Nunavut. The research was published in the journal Ecology and Evolution.

Aerial video of a polar bear on grassy, rocky terrain with white birds circling nearby.
A polar bear storms eider duck nests on East Bay island in Nunavut, while herring gulls follow closely behind to snack on any remaining eggs. (Submitted by Andrew Barnas)

A NASA mission might have the tools to detect life on Europa from space

Quirks and Quarks8:05A NASA mission might have the tools to detect life on Europa from space

NASA’s Europa Clipper mission, due to launch this fall, is set to explore the jewel of our solar system: Jupiter’s moon, Europa. The mission’s focus is to determine if the icy moon, thought to harbour an ocean with more water than all of the water on Earth, is amenable to life. However, postdoctoral researcher Fabian Klenner, now at the University of Washington, demonstrated how the spacecraft may be able to detect fragments of bacterial life in a single grain of ice ejected from the surface of the moon. The study was published in the journal Science Advances.

The silhouette of the spacecraft is flying over a brightly pink, blue and orange tinted moon with lots of darker coloured veins underneath with a slightly eclipsed Jupiter looming in the backdrop.
Scientists think under Europa’s icy shell, there is a global, saltwater ocean with twice the volume of Earth’s oceans combined. (NASA/Jet Propulsion Laboratory/Caltech)

Pollution is preventing pollinators from recognizing floral plants by scent

Quirks and Quarks7:50Pollution is preventing pollinators from finding plants by scent

Our polluted air is transforming floral scents so pollinators that spread their pollen can no longer recognize them. In a new study in the journal Science, researchers found that a certain compound in air pollution reacts with the flower’s scent molecules so pollinators — like the hummingbird hawk-moths that pollinate at night — fail to recognize them. Jeremy Chan, a postdoctoral researcher at the University of Naples, said the change in scent made the flowers smell “less fruity and less fresh.”

A huge insect that looks like a hummingbird hovers over a vibrant pink flower with its long antenna inside one of the blooms.
Scientists found that a hummingbird hawk-moth’s ability to recognize the smell of flowers is hampered by air pollution. (Thomas Kienzle/AFP/Getty Images)

An Australian Atlantis and underwater archeological remains in the Baltic 

Quirks and Quarks17:14An Australian Atlantis and underwater archeological remains in the Baltic

During the last ice age, sea levels were more than 100 metres lower than they are today, which means vast tracts of what are currently coastal seafloor were dry land back then. Geologists and archaeologists are searching for these lost landscapes to identify places prehistoric humans might have occupied. These included a country-sized area of Australia that could have been home to half a million people. Archaeologist Kasih Norman and her colleagues published their study of this now-drowned landscape in Quaternary Science Reviews

Another example is an undersea wall off the coast of Northern Germany that preserves an underwater reindeer hunting ground, described in research led by Jacob Geersen, published in the journal PNAS.

a black-and-white depiction of a small group of caribou walking between a low stone wall and an ocean coastline.
An artist’s representation of caribou being directed by a hunters’ stone wall, as it would have appeared 8-11,000 years ago, before rising sea levels left it 20m below the surface of the Baltic Sea. (Michał Grabowski)

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Solar eclipse April 8 – South Grey News

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March 28, 2024

Graphic: Appalachian Mtn Club

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Grey Bruce Public Health is urging residents to resist the temptation to look directly at the sun during the upcoming solar eclipse and take steps to safeguard their visual health during this relatively rare celestial event.

On April 8, 2024, parts of southern and eastern Ontario will experience a total solar eclipse for the first time since 1925. Grey-Bruce will be outside of the so-called Path of Totality — a narrow area where the moon will completely block out the sun — but will still experience a partial eclipse.

The eclipse is expected to begin at about 2 pm and continue until 4:30 pm The eclipse will peak around 3:20 pm.

It is never safe to stare directly at the sun, but it may be tempting to do so during a solar eclipse.

Looking directly at the sun during an eclipse can cause retinal burns, blurred vision, and/or temporary or permanent loss of visual function, according to the Ontario Association of Optometrists. Damage to the eyes can occur without any sensation of pain.

Grey Bruce Public Health advises the following:

  • Do not look directly at the sun without proper eye protection during the solar eclipse. Looking at even a small sliver of the sun before or after the eclipse without proper eye protection can harm vision.
  • Keep a close eye on children and other vulnerable family members during the eclipse to ensure they do not inadvertently look up at the sun without proper eye protection.
  • To safely view the eclipse, ISO-certified eclipse glasses that meet the ISO 12312-2 international safety standard must be worn. Ensure these glasses are in good condition, without any wrinkles or scratches, and that they fully cover the entire field of vision. Put on the glasses when looking away from the sun, then look at the eclipse. Look away from the sun before taking the glasses off.
  • Regular sunglasses or homemade filters will not protect the eyes.
  • It is not safe to view the eclipse through a camera/phone lens, telescope, binoculars, or any other optical device.

Other ways to safely experience the solar eclipse include watching a livestream of the event or creating and using an eclipse box or pinhole projector.

Anyone experiencing temporary vision loss or blurred vision during or after the eclipse should speak with their eye care professional or healthcare provider as soon as possible.

Anyone experiencing blindness (immediate or delayed) after viewing the eclipse must seek emergency care immediately.

More information on the upcoming eclipse is available on the GBPH website.


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South Grey News does not have the resources of a big corporation. We are a small, locally owned-and-operated organization. Research, analysis and physical attendance at public meetings and community events requires considerable effort. But contributions from readers and advertisers, however big or small, go a long way to helping us deliver positive, open and honest journalism for this community.

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