Scientists identify 29 planets where aliens could observe Earth

Astronomers estimate 29 habitable planets are positioned to see Earth transit and intercept human broadcasts

The scientists identified 1,715 star systems where alien observers could have discovered Earth in the past 5,000 years by watching it ‘transit’ across the face of the sun. Photograph: c/o Cornell

Ian Sample Science editor@iansampleWed 23 Jun 2021 11.00 EDT

For centuries, Earthlings have gazed at the heavens and wondered about life among the stars. But as humans hunted for little green men, the extraterrestrials might have been watching us back.

In new research, astronomers have drawn up a shortlist of nearby star systems where any inquisitive inhabitants on orbiting planets would be well placed to spot life on Earth.

The scientists identified 1,715 star systems in our cosmic neighbourhood where alien observers could have discovered Earth in the past 5,000 years by watching it “transit” across the face of the sun.

Among those in the right position to observe an Earth transit, 46 star systems are close enough for their planets to intercept a clear signal of human existence – the radio and TV broadcasts which started about 100 years ago.Advertisement

The researchers estimate that 29 potentially habitable planets are well positioned to witness an Earth transit, and eavesdrop on human radio and television transmissions, allowing any observers to infer perhaps a modicum of intelligence. Whether the broadcasts would compel an advanced civilisation to make contact is a moot point.

“One way we find planets is if they block out part of the light from their host star,” said Lisa Kaltenegger, professor of astronomy and director of the Carl Sagan Institute at Cornell University in New York. “We asked, ‘Who would we be the aliens for if somebody else was looking?’ There is this tiny sliver in the sky where other star systems have a cosmic front seat to find Earth as a transiting planet.”

Earthly astronomers have detected thousands of planets beyond the solar system. About 70% are spotted when alien worlds pass in front of their host stars and block some of the light that reaches scientists’ telescopes. Future observatories, such as Nasa’s James Webb Space Telescope due to launch this year, will look for signs of life on “exoplanets” by analysing the composition of their atmospheres.

To work out which nearby star systems are well placed to observe an Earth transit, Kaltenegger and Dr Jackie Faherty, an astrophysicist at the American Museum of Natural History, turned to the European Space Agency’s Gaia catalogue of star positions and motions. From this they identified 2,034 star systems within 100 parsecs (326 light years) that could spot an Earth transit any time from 5,000 years ago to 5,000 years in the future.

One star known as Ross 128, a red dwarf in the Virgo constellation, is about 11 light years away – close enough to receive Earth broadcasts – and has a planet nearly twice the size of Earth. Any suitably equipped life on the planet could have spotted an Earth transit for more than 2,000 years, but lost the vantage point 900 years ago. If there is intelligent life on any of the two known planets orbiting Teegarden’s star, 12.5 light years away, it will be in a prime position to watch Earth transits in 29 years’ time.

At 45 light years away, another star called Trappist-1 is also close enough to eavesdrop on human broadcasts. The star hosts at least seven planets, four of them in the temperate, habitable zone, but they will not be in position to witness an Earth transit for another 1,642 years, the scientists write in Nature.

The findings come as the US government prepares to publish a hotly anticipated report on unidentified flying objects (UFOs). The report from the Pentagon’s Unidentified Aerial Phenomena Task Force, which was set up to gain insights into the nature and origins of unknown aircraft, is not expected to reveal evidence of alien antics, or rule it out.

Prof Beth Biller at Edinburgh University’s Institute for Astronomy, who was not involved in the Nature study, said the work could change how scientists approach Seti, the search for extraterrestrial life. “What was striking to me was how few of the stars within 100 parsecs could have viewed a transiting Earth,” she said.

“The transit method requires a very precise alignment between the transiting planet, its star, and the sun for a given planet to be detectable, so this result is not surprising. Now I am curious about what fraction of the stars in the Gaia catalogue of nearby stars have the right vantage point to detect the Earth via other exoplanet detection methods, such as the radial velocity method or direct imaging!”

An enormous ‘mega comet’ is flying into our solar system

SPACE 21 June 2021

By Jonathan O’Callaghan

New Scientist Default Image
A large object in the outer solar system may be a “mega comet”MARK GARLICK/Getty Images/Science Photo Library RF

Astronomers have discovered a huge and previously unknown object entering our solar system that will reach the orbit of Saturn in 2031. It is possibly the largest body from the outer reaches of our solar system ever found to make such a close approach to the sun.

Known as 2014 UN271, it is estimated to be between 100 and 370 kilometres across. The object was spotted by the Dark Energy Survey (DES), a project using the Victor …

Continue reading

Read more:

The surface of Venus is geologically active

22 June 2021/

Amalyah Hart

New study of the ‘hellish’ planet reveals tectonic activity, disproves solid lithosphere theory.

A 1,100 km-wide, false-color radar view of Lavinia Planitia, one of the lowland regions on Venus where the lithosphere has fragmented into blocks (purple) delineated by belts of tectonic structures (yellow). Image credit:NC State University based upon NASA/JCL imagery

Venus’ surface is not a single, solid “lithosphere”, as once thought, but a patchwork of tectonic plates with similar activity to – but not the same as – those here on Earth, according to a new study out today in Proceedings of the National Academy of Sciences. 

The study shows that these tectonic plates jostle and bump against one another like pack ice on a frozen lake, suggesting Venus is still geologically active.

“We’ve identified a previously unrecognised pattern of tectonic deformation on Venus, one that is driven by interior motion just like on Earth,” says Paul Byrne, associate professor of planetary science at North Carolina State University, the lead and co-corresponding author of the work. “Although different from the tectonics we currently see on Earth, it is still evidence of interior motion being expressed at the planet’s surface.”

Byrne and an international team of researchers used radar images from NASA’s Magellan spacecraft, which imaged the entire surface of Venus before plunging into the Venusian atmosphere in the summer of 1993 and breaking apart. Looking at the extensive Venusian lowlands, the team saw areas where large blocks of the lithosphere appeared to have moved, some pulling apart, others pushing together, and others sliding past one another.

By creating a computer model of this deformation, the team found that sluggish motion in the planet’s interior explains the more gentle tectonic activity occurring on Venus – as opposed to the violent tectonic motions on Earth, which can create huge mountain ranges or vast subduction systems.

The find is significant because Venus was once thought to have a motionless, solid surface just like Mars or the Moon, rather than a geologically active, moving surface.

“We know that much of Venus has been volcanically resurfaced over time, so some parts of the planet might be really young, geologically speaking,” Byrne says. “But several of the jostling blocks have formed in and deformed these young lava plains, which means that the lithosphere fragmented after those plains were laid down. This gives us reason to think that some of these blocks may have moved geologically very recently – perhaps even up to today.”

The new “pack ice” pattern identified on our furnace-hot neighbour may offer clues about the deformation of tectonic plates on planets outside the solar system, as well as the geological formation of early Earth.

“The thickness of a planet’s lithosphere depends mainly upon how hot it is, both in the interior and on the surface,” Byrne says. “Heat flow from the young Earth’s interior was up to three times greater than it is now, so its lithosphere may have been similar to what we see on Venus today: not thick enough to form plates that subduct, but thick enough to have fragmented into blocks that pushed, pulled, and jostled.”

The new study is part of a renaissance in interest surrounding our neighbouring planet. Both NASA and the European Space Agency recently approved three new missions to Venus that will observe the planet’s surface and assess whether it once held oceans – and potentially life.

“It’s great to see renewed interest in the exploration of Venus, and I’m particularly excited that these missions will be able to test our key finding that the planet’s lowlands have fragmented into jostling crustal blocks,” Byrne says.

Hundreds of mysterious fast radio bursts detected in space

By Ashley Strickland, CNN

Updated 1:28 AM ET, Thu June 10, 2021

(CNN)Hundreds of mysterious fast radio bursts have been detected in space thanks to a Canadian telescope and an international group of researchers.The origins of these bright, millisecond-long flashes of light are unknown because the bursts, or FRBs, are unpredictable and vanish quickly. Scientists first observed them in 2007. In the decade following, they only observed about 140 bursts across the universe.”The thing about FRBs is that they are really hard to catch,” said Kiyoshi Masui, assistant professor of physics at MIT and member of the university’s Kavli Institute for Astrophysics and Space Research. “You have to have your radio telescope pointed at just the right place at just the right time and you can’t predict where or when that will be.”

Most radio telescopes only see a patch of sky the size of the moon at a given time, meaning the vast majority of FRBs go unseen, Masui said.

That all changed when the CHIME telescope, located at the Dominion Radio Astrophysical Observatory in British Columbia, Canada, began receiving radio signals in 2018 during its first year of operation.

The CHIME radio telescope array, pictured here, detected 535 fast radio bursts in its first year of operation.The CHIME radio telescope array, pictured here, detected 535 fast radio bursts in its first year of operation.The stationary radio telescope, called the Canadian Hydrogen Intensity Mapping Experiment, detected 535 new fast radio bursts between 2018 and 2019.This enabled scientists to create the CHIME catalog of fast radio bursts, which was presented Wednesday at the 238th American Astronomical Society Meeting, an event that’s occurring virtually.

Not only does the catalog expand on the known number of fast radio bursts, but it also broadens the information available about their locations and properties. While most of the fast radio bursts occurred just once, 61 of them were repeating fast radio bursts from 18 sources. The repeating bursts appear differently — each flash lasts a little longer than the single bursts.When a burst repeats, scientists have a much better chance of tracing it back to its point of origin. These locations could help scientists determine what causes the bursts as well.

Fast radio burst may have come from the Milky Way

Fast radio burst may have come from the Milky WayBased on their observations, the researchers believe that single fast radio bursts may have sources that are different from repeating ones.”With all these sources, we can really start getting a picture of what FRBs look like as a whole, what astrophysics might be driving these events, and how they can be used to study the universe going forward,” said Kaitlyn Shin, CHIME member and a graduate student in the Massachusetts Institute of Technology’s Department of Physics, in a statement.

How CHIME works

The CHIME telescope functions a bit differently from others used for radio astronomy. The array of four giant radio antennas, comparable to the size and shape of half-pipes used for snowboarding, are entirely motionless. As Earth rotates on its axis, this array receives radio signals from half of the sky.Typically, radio dishes move to capture light from different areas in the sky. Instead, CHIME uses an all digital design and has a correlator, a digital signaling processor to capture incoming radio signals. It can churn through massive amounts of data — about 7 terabits per second, or the equivalent of a small percentage of global internet traffic.

Mysterious fast radio bursts traced to spiral galaxy arms

Mysterious fast radio bursts traced to spiral galaxy arms“Digital signal processing is what makes CHIME able to reconstruct and ‘look’ in thousands of directions simultaneously,” Masui said. “That’s what helps us detect FRBs a thousand times more often than a traditional telescope.”The 535 bursts detected by CHIME came from all parts of the sky — and space. Based on the information they gathered, the researchers calculated that these bright fast radio bursts likely occur about 800 times per day across the entire sky.”That’s kind of the beautiful thing about this field — FRBs are really hard to see, but they’re not uncommon,” Masui said. “If your eyes could see radio flashes the way you can see camera flashes, you would see them all the time if you just looked up.”While these bursts would be intriguing enough based on their mysterious nature alone, scientists also believe they can use the bursts to have a better understanding of the universe and even map the distribution of gas across it.Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more.When these radio waves travel through space, it’s likely they’re encountering gas or plasma. This can distort the waves, change their properties and even their trajectory. Determining this information about a radio burst could help scientists estimate the distance it traveled and how much gas it encountered.”This carries a record within it of the structure of the universe that it has traveled through on its way to get from the source to us,” Masui said. “Because of this, we think that they are going to be the ultimate tool for studying the universe.”Many of these bright radio bursts detected by CHIME traveled from distant galaxies and were likely created by incredibly energetic sources — but researchers are still trying to determine the exact nature of those sources.This sky map shows fast radio bursts based on CHIME detections. This sky map shows fast radio bursts based on CHIME detections.

With enough fast radio bursts, it may be possible to map out the large-scale structure of the universe.”These large structures make up the filaments of the cosmic web,” said Alex Josephy, a doctoral student in physics at McGill University in Canada. “With the FRB catalog, we have detected this correlation between FRBs and large-scale structure. This is really, really exciting and ushers in a new era of (fast radio burst) cosmology.”

Scientists discover new exoplanet with an atmosphere ripe for study

JUNE 9, 2021

by University of New Mexico

Scientists discover new exoplanet with an atmosphere ripe for study
An artist’s impression shows an exoplanet orbiting the Sun-like star. Credit: ESO/M. Kornmesser

An international group of collaborators, including scientists from NASA’s Jet Propulsion Laboratory and The University of New Mexico, have discovered a new, temperate sub-Neptune sized exoplanet with a 24-day orbital period orbiting a nearby M dwarf star. The recent discovery offers exciting research opportunities thanks to the planet’s substantial atmosphere, small star, and how fast the system is moving away from the Earth.

The research, titled TOI-1231 b: A Temperate, Neptune-Sized Planet Transiting the Nearby M3 Dwarf NLTT 24399, will be published in a future issue of The Astronomical Journal. The exoplanet, TOI-1231 b, was detected using photometric data from the Transiting Exoplanet Survey Satellite (TESS) and followed up with observations using the Planet Finder Spectrograph (PFS) on the Magellan Clay telescope at Las Campanas Observatory in Chile. The PFS is a sophisticated instrument that detects exoplanets through their gravitational influence on their host stars. As the planets orbit their hosts, the measured stellar velocities vary periodically, revealing the planetary presence and information about their mass and orbit.

The observing strategy adopted by NASA’s TESS, which divides each hemisphere into 13 sectors that are surveyed for roughly 28 days, is producing the most comprehensive all-sky search for transiting planets. This approach has already proven its capability to detect both large and small planets around stars ranging from sun-like down to low-mass M dwarf stars. M dwarf stars, also known as a red dwarf, are the most common type of star in the Milky Way making up some 70 percent of all stars in the galaxy.

M dwarfs are smaller and possess a fraction of the sun’s mass and have low luminosity. Because an M dwarf is smaller, when a planet of a given size transits the star, the amount of light that is blocked out by the planet is larger, making the transit more easily detectable. Imagine an Earth-like planet passing in front of a star the size of the sun, it’s going to block out a tiny bit of light; but if it’s passing in front of a star that’s a lot smaller, the proportion of light that’s blocked out will be larger. In a sense, this creates a larger shadow on the surface of the star, making planets around M dwarfs more easily detectable and easier to study.

Although it enables the detection of exoplanets across the sky, TESS’s survey strategy also produces significant observational biases based on orbital period. Exoplanets must transit their host stars at least twice within TESS ‘s observing span to be detected with the correct period by the Science Processing Operations Center (SPOC) pipeline and the Quick Look Pipeline (QLP), which search the 2-minute and 30-minute cadence TESS data, respectively. Because 74 percent of TESS’ total sky coverage is only observed for 28 days, the majority of TESS exoplanets detected have periods less than 14 days. TOI-1231b’s 24-day period, therefore, makes its discovery even more valuable.×280&!1&btvi=1&fsb=1&xpc=7tK2NikwAf&p=https%3A//

NASA JPL scientist Jennifer Burt, the lead author of the paper, along with her collaborators including Diana Dragomir, an assistant professor in UNM’s Department of Physics and Astronomy, measured both the radius and mass of the planet.

“Working with a group of excellent astronomers spread across the globe, we were able to assemble the data necessary to characterize the host star and measure both the radius and mass of the planet,” said Burt. “Those values in turn allowed us to calculate the planet’s bulk density and hypothesize about what the planet is made out of. TOI-1231 b is pretty similar in size and density to Neptune, so we think it has a similarly large, gaseous atmosphere.”

“Another advantage of exoplanets orbiting M dwarf hosts is that we can measure their masses easier because the ratio of the planet mass to the stellar mass is also larger. When the star is smaller and less massive, it makes detection methods work better because the planet suddenly plays a bigger role as it stands out more easily in relation to the star,” explained Dragomir. “Like the shadow cast on the star. The smaller the star, the less massive the star, the more the effect of the planet can be detected.

“Even though TOI 1231b is eight times closer to its star than the Earth is to the Sun, its temperature is similar to that of Earth, thanks to its cooler and less bright host star,” says Dragomir. “However, the planet itself is actually larger than earth and a little bit smaller than Neptune—we could call it a sub-Neptune.”

Burt and Dragomir, who actually initiated this research while they were Fellows at MIT’s Kavli Institute, worked with scientists specializing in observing and characterizing the atmospheres of small planets to figure out which current and future space-based missions might be able to peer into TOI-1231 b’s outer layers to inform researchers exactly what kinds of gases are swirling around the planet. With a temperature around 330 Kelvin or 140 degrees Fahrenheit, TOI-1231b is one of the coolest, small exoplanets accessible for atmospheric studies discovered thus far.

Past research suggests planets this cool may have clouds high in their atmospheres, which makes it hard to determine what types of gases surround them. But new observations of another small, cool planet called K2-18 b broke this trend and showed evidence of water in its atmosphere, surprising many astronomers.

“TOI-1231 b is one of the only other planets we know of in a similar size and temperature range, so future observations of this new planet will let us determine just how common (or rare) it is for water clouds to form around these temperate worlds,” said Burt.

Additionally, with its host star’s high Near-Infrared (NIR) brightness, it makes an exciting target for future missions with the Hubble Space Telescope (HST) and the James Webb Space Telescope (JWST). The first set of these observations, led by one of the paper’s co-authors, should take place later this month using the Hubble Space Telescope.

“The low density of TOI 1231b indicates that it is surrounded by a substantial atmosphere rather than being a rocky planet. But the composition and extent of this atmosphere are unknown!” said Dragomir. “TOI1231b could have a large hydrogen or hydrogen-helium atmosphere, or a denser water vapor atmosphere. Each of these would point to a different origin, allowing astronomers to understand whether and how planets form differently around M dwarfs when compared to the planets around our Sun, for example. Our upcoming HST observations will begin to answer these questions, and JWST promises an even more thorough look into the planet’s atmosphere.”

Another way to study the planet’s atmosphere is to investigate whether gas is being blown away, by looking for evidence of atoms like hydrogen and helium surrounding the planet as it transits across the face of its host star. Generally, hydrogen atoms are almost impossible to detect because their presence is masked by interstellar gas. But this planet-star system offers a unique opportunity to apply this method because of how fast it’s moving away from the Earth.

“One of the most intriguing results of the last two decades of exoplanet science is that, thus far, none of the new planetary systems we’ve discovered look anything like our own solar system,” said Burt. “They’re full of planets between the size of Earth and Neptune on orbits much shorter than Mercury’s, so we don’t have any local examples to compare them to. This new planet we’ve discovered is still weird—but it’s one step closer to being somewhat like our neighborhood planets. Compared to most transiting planets detected thus far, which often have scorching temperatures in the many hundreds or thousands of degrees, TOI-1231 b is positively frigid.”

In closing, Dragomir reflects that “this planet joins the ranks of just two or three other nearby small exoplanets that will be scrutinized with every chance we get and using a wide range of telescopes, for years to come so keep an eye out for new TOI1231b developments!”

This article is in press at The Astronomical Journal.

Explore furtherNew sub-Neptune exoplanet discovered by astronomers

A Record-Breaking Flare Has Erupted From The Closest Star to Our Solar System

(NRAO/S. Dagnello)SPACE


Two years ago, our star’s next door neighbor – Proxima Centauri – got a little emotional. It happens from time to time, only this time, the small red star really let go. A storm of fury that breaks its previous records, outdoing anything our own Sun could manage by magnitudes.

Sure, we were eavesdropping, but it’s all in the name of science. Besides, we now have some galactic gossip we’re dying to share – this was not your typical solar eruption.

As far as neighbors go, you could do worse than Proxima Centauri. At a mere 4 light-years (just over 30 trillion kilometers) over the back fence, it’s close enough to keep an eye on without being prone to blowing up in a life-destroying cataclysm.  

That doesn’t mean it’s quiet. Like most hot-tempered red dwarf stars, Proxima Centauri vents its rage every now and then in a brilliant display of radiation, spilling streams of plasma and light out into its system with a manic snapping and rejoining of its magnetic fields.

This is bad news for its host of innermost planets, which periodically cop a roasting that makes it unlikely that any complex organic chemistry on the surface would have remained intact long enough to spark into life.

But for us, watching these outbursts from a safe distance gives insight into the mechanisms of stellar physics. In 2019, astronomers trained nine telescopes around the globe on Proxima Centauri for a marathon 40-hour session.

They weren’t planning on missing any details – using telescopes such as the Australian Square Kilometre Array Pathfinder, the Atacama Large Millimeter/submillimeter Array, and the Transiting Exoplanet Survey Satellite, they listened in on multiple frequencies, from radio to X-ray.

“It’s the first time we’ve ever had this kind of multi-wavelength coverage of a stellar flare,” says astrophysicist Meredith MacGregor from University of Colorado Boulder.

“Usually, you’re lucky if you can get two instruments.”

And oh boy, they weren’t disappointed. Not only did five of their instruments catch sight of the largest flare to be observed in the Proxima Centauri system to date, the signature of the eruption was strange enough to suggest they had an entirely new kind of solar event on their hands.

Back in 2016, astronomers caught a similar superflare, one that could be seen without telescopes.

Though technically bigger, becoming 14,000 times brighter over the span of a few seconds, this more recent activity was largely in the form of wavelengths we can’t see, such as in the ultraviolet and radio parts of the spectrum.

Finding such a strong surge in the radio zone of millimeter range waves was completely unexpected, making this flare really worth paying attention to.

“In the past, we didn’t know that stars could flare in the millimeter range, so this is the first time we have gone looking for millimeter flares,” says MacGregor.  

The timing and energies of the different wavelengths of light in the flare provide astrophysicists with a novel look into the mechanisms behind flare production, adding details to our models.

Knowing that solar flares emit in this part of the spectrum means researchers will be more inclined to train a greater range of instruments on variable stars in the future in the hopes of catching a stray whisper of radiation they missed before.

“There will probably be even more weird types of flares that demonstrate different types of physics that we haven’t thought about before,” says MacGregor.

This won’t be the last tantrum we’ll see Proxima Centauri have, and probably not even the biggest. While this unusual eruption was the largest of the flares seen during the 40-hour window of observations, it wasn’t the only one the researchers saw.

In fact, our tiny neighbor could be in a near constant rage, unleashing its hostility at least once a day. Maybe more.

At least its temper isn’t as bad as AD Leonis, another angry red dwarf in our neighborhood. Now there’s some gossip.

This research was published in The Astrophysical Journal Letters.

This ‘super-Earth’ seems lovely, until you look up

Mike WehnerMon, April 19, 2021, 2:36 PM·3 min read

Earth is great, but what if it were bigger? So-called “super-Earths” are rocky worlds like our own but are several times bigger, and could offer us a new home if we ever were to leave our solar system. Some of the super-Earths that scientists have discovered are too far away from their star to be warm enough for liquid water, so those are a no-go. Some are within or near the habitable zone, which is great news for us, but the vast majority of those are too distant to consider visiting right now. A newly-discovered super-Earth around the star GJ-740 is special because it’s very close to Earth, relatively speaking — only 36 light-years — but there’s another problem. It’s very, very hot.

The planet is estimated to be around three times as massive as Earth. That’s a sizeable chunk of rock, and it’s orbiting a star that is much cooler than our own Sun. GJ-740 is a red dwarf, meaning that its peak temperature is thousands of degrees cooler than our own Sun. Unfortunately, the planet is incredibly close to its star, canceling most of the benefits of orbiting a cooler star and ensuring that the super-Earth’s surface is still very, very warm.

Earth takes a full 365 days to complete an orbit of our Sun. On this newly-discovered super-Earth, a day is much shorter. In fact, the planet completes a full “year” in a mere 2.4 Earth days. That indicates that the planet is incredibly close to its star and, as a result, is absorbing a huge amount of the star’s radiation in the form of heat and various wavelengths of light. The scientists don’t offer a guess as to how hot the planet’s surface is, but it would be absolutely unlivable for any life forms originating on Earth.- ADVERTISEMENT -

“This is the planet with the second shortest orbital period around this type of star. The mass and the period suggest a rocky planet, with a radius of around 1.4 Earth radii, which could be confirmed in future observations with the TESS satellite”, Borja Toledo Padrón, the first author of the article, said in a statement. “The search for new exoplanets around cool stars is driven by the smaller difference between the planet’s mass and the star’s mass compared with stars in warmer spectral classes (which facilitates the detection of the planets’ signals), as well as the large number of this type of stars in our Galaxy”

Story continues

An Exploding Star 65 Light-Years Away From Earth May Have Triggered a Mass Extinction

Composite image of supernova 1987A. (NASA, ESA et al.)SPACE


Life was trying, but it wasn’t working out. As the Late Devonian period dragged on, more and more living things died out, culminating in one of the greatest mass extinction events our planet has ever witnessed, approximately 359 million years ago.

The culprit responsible for so much death may not have been local, scientists say. In fact, it might not have even come from our Solar System.

Rather, a study published in August last year, led by astrophysicist Brian Fields from the University of Illinois Urbana-Champaign, suggests this great extinguisher of life on Earth could have been a distant and completely foreign phenomenon – a dying star, exploding far across the galaxy, many light-years away from our own remote planet.

Sometimes, mass die-offs like the Late Devonian extinction are thought to be triggered by exclusively terrestrial causes: a devastating volcanic eruption, for instance, which chokes the planet into lifelessness.

Or, it could be a deadly visitor barging in from out of town – an asteroid collision, like the kind that took out the dinosaurs. Death from space, however, could ultimately come from far more remote places.

“The overarching message of our study is that life on Earth does not exist in isolation,” Fields said back in 2020.

“We are citizens of a larger cosmos, and the cosmos intervenes in our lives – often imperceptibly, but sometimes ferociously.”

In their new work, Fields and his team explore the possibility that the dramatic decline in ozone levels coinciding with the Late Devonian extinction might not have been a result of volcanism or an episode of global warming.

Instead, they suggest it’s possible the biodiversity crisis exposed in the geological record could have been caused by astrophysical sources, speculating that the radiation effects from a supernova (or multiple) approximately 65 light-years from Earth may have been what depleted our planet’s ozone to such disastrous effect.

It may be the first time such an explanation has been put forward for the Late Devonian extinction, but scientists have long considered the potentially deadly repercussions of near-Earth supernovas in this kind of context.

Speculation that supernovas could trigger mass extinctions dates back to the 1950s. In more recent times, researchers have debated the estimated ‘kill distance’ of these explosive events (with estimates ranging between 25 to 50 light-years).

In their recent estimates, though, Fields and his co-authors propose that exploding stars from even farther away could have harmful effects on life on Earth, through a possible combination of both instantaneous and long-lived effects.

“Supernovae (SNe) are prompt sources of ionizing photons: extreme UV, X-rays, and gamma rays,” the researchers explain in their paper.

“Over longer timescales, the blast collides with surrounding gas, forming a shock that drives particle acceleration. In this way, SNe produce cosmic rays, that is, atomic nuclei accelerated to high energies. These charged particles are magnetically confined inside the SN remnant, and are expected to bathe Earth for ~100 ky [approximately 100,000 years].”

These cosmic rays, the researchers argue, could be strong enough to deplete the ozone layer and cause long-lasting radiation damage to life-forms inside Earth’s biosphere – which roughly parallels evidence of both loss of diversity and deformations in ancient plant spores found in the deep rock of the Devonian–Carboniferous boundary, laid approximately 359 million years ago.

Of course, it’s just a hypothesis for now. At present, we don’t have any evidence that can confirm a distant supernova (or supernovae) was the cause of the Late Devonian extinction. But we might be able to find something almost as good as proof.

In recent years, scientists examining the prospect of near-Earth supernovas as a basis for mass extinctions have been looking for traces of ancient radioactive isotopes that could only have been deposited on Earth via exploding stars.

One isotope in particular, iron-60, has been the focus of much research and has been found in numerous locations on Earth.

In the context of the Late Devonian extinction, though, other isotopes would be strongly indicative of the extinction-by-supernova hypothesis put forward by Fields and his team: plutonium-244 and samarium-146.

“Neither of these isotopes occurs naturally on Earth today, and the only way they can get here is via cosmic explosions,” explained co-author and astronomy student Zhenghai Liu from the University of Illinois Urbana-Champaign.

In other words, if plutonium-244 and samarium-146 and can be found buried in the Devonian–Carboniferous boundary, the researchers say we’ll basically have our smoking gun: interstellar evidence that firmly implicates a dying star as the trigger behind one of Earth’s worst-ever die-offs.

And we’ll never look up at the skies in quite the same way again.

The findings were reported in PNAS.

A version of this article was first published in August 2020.

Bizarre Space Object Is Likely From Another Solar System, New Study Says

It’s believed to have come from a Pluto-like planet.

playPlayvolumeMutedUnmuteAutoplay setting: OnWesley LeBlancBy Wesley LeBlancUpdated: 23 Mar 2021 9:13 amPosted: 22 Mar 2021 9:59 amAn interstellar object previously believed by some to be from aliens might actually be a piece of a planet from another solar system, according to a new study.A massive cigar-shaped object known as Oumuamua passed by Earth in 2017 at 196,000 mph and Harvard professor, Avi Loeb, said earlier this year that it likely originated from aliens. A new study from two Arizona State University scientists suggests the object to actually be the piece of a Pluto-like planet in a different solar system knocked off the surface about half a billion years ago.

“This research is exciting in that we’ve probably resolved the mystery of what Oumuamua is and we can reasonably identify it as a chunk of an ‘exo-Pluto,’ a Pluto-like planet in another solar system,” ASU astrophysicist, Steven Desch, said in a press release. “Until now, we’ve had no way to know if other solar systems have Pluto-like planets, but now we have seen a chunk of one pass by Earth.”Scientist Says Object That Flew By Earth Could Have Been Made By Aliens – IGN NewsshareShareAutoplay setting: On1:00Desch mentioned that some have deemed Oumuamua as something originating from aliens, but they said that might have been the result of an inability to “immediately explain it in detail.”

“Everybody is interested in aliens, and it was inevitable that this first object outside the solar system would make people think aliens,” Desch said. “But it’s important in science not to jump to conclusions. It took two or three years to figure out a natural explanation — a chunk of nitrogen ice — that matches everything we know about Oumuamua. That’s not long in science, and far too soon to say we had exhausted all natural explanations.”

Rather than aliens, Desch’s study with fellow ASU researcher and astronomer, Alan Jackson, posits that Oumuamua is actually a piece of solidified nitrogen. The reason the pair conclude the object is likely from a Pluto-like planet is because Pluto’s surface is also made of solidified nitrogen.

Jackson said it was likely knocked off the surface of a planet about half a billion years ago, at which point, it was thrown out of its solar system. Floating through space at nearly 200,000 mph, it eventually arrived to our solar system.Cosmos: Possible Worlds Gallery


“Oumuamua likely wasn’t flat when it entered our solar system, but melted away to a sliver, losing more than 95% of its mass, during its close encounter with the Sun,” Jackson said in the press release.

The interstellar object passed by Earth as a bizarre, cigar-shaped object, but it likely looked something more like a comet when it first left its origin point. Jackson said the outer layers of solid nitrogen evaporated as it floated through space, especially as it endured the heat of our Sun, which led to its flattened shape. They compared this shedding of nitrogen layers to the way a bar of soap slowly flattens out as it’s used.

The duo theorized multiple types of ice for the object, but studies revealed that it had to have been nitrogen.

“We knew we had hit on the right idea when we completed the calculation for what albedo (which is the proportion of the incident light or radiation that is reflected by a surface) would make the motion of Oumuamua match the observations,” Jackson said. “That value came out as being the same as we observe on the surface of Pluto or Triton, bodies covered in nitrogen ice.”Cosmos: Possible Worlds Exclusive Season Finale ClipshareShareAutoplay setting: On2:02NASA said in 2018 that Oumuamua is, “the first object ever seen in our solar system that is known to have originated elsewhere.” Desch and Jackson said that as more interstellar objects like Oumuamua are discovered, scientists like themselves can continue to learn more about what lies beyond our solar system.

“It’s hoped that in a decade or so we can acquire statistics on what sorts of objects pass through the solar system, and if nitrogen ice chunks are rare or as common as we’ve calculated,” Jackson said. “Either way, we should be able to learn a lot about other solar systems, and whether they underwent the same sorts of collisional histories that ours did.”

Worlds With Underground Oceans – Like Europa, Titan, and Enceladus – May Be More Conducive to Supporting Life Than Earth

TOPICS:AstrobiologyAstronomyAstrophysicsEnceladusMoonsPopularSaturnSouthwest Research Institute


Interior water ocean worlds like Saturn’s moon, Enceladus, are prevalent throughout the universe. New research from Southwest Research Institute suggests that layers of rock and ice may shield life within such oceans, protecting it from impacts, radiation and other hazards and concealing it from detection. Layers of rock and ice may therefore shield and protect life residing in them, and also sequester them from threats and detection. Credit: NASA/JPL-Caltech/Southwest Research Institute

Layers of ice and rock obviate the need for “habitable zone” and shield life against threats.

SwRI researcher theorizes worlds with underground oceans may be more conducive to life than worlds with surface oceans like Earth.

One of the most profound discoveries in planetary science over the past 25 years is that worlds with oceans beneath layers of rock and ice are common in our solar system. Such worlds include the icy satellites of the giant planets, like Europa, Titan, and Enceladus, and distant planets like Pluto.

In a report presented at the 52nd annual Lunar and Planetary Science Conference (LPSC 52) this week, Southwest Research Institute planetary scientist S. Alan Stern writes that the prevalence of interior water ocean worlds (IWOWs) in our solar system suggests they may be prevalent in other star systems as well, vastly expanding the conditions for planetary habitability and biological survival over time.

It has been known for many years that worlds like Earth, with oceans that lie on their surface, must reside within a narrow range of distances from their stars to maintain the temperatures that preserve those oceans. However, IWOWs are found over a much wider range of distances from their stars. This greatly expands the number of habitable worlds likely to exist across the galaxy.

Worlds like Earth, with oceans on their exterior, are also subject to many kinds of threats to life, ranging from asteroid and comet impacts, to stellar flares with dangerous radiation, to nearby supernova explosions and more. Stern’s paper points out that IWOWs are impervious to such threats because their oceans are protected by a roof of ice and rock, typically several to many tens of kilometers thick, that overlie their oceans.

“Interior water ocean worlds are better suited to provide many kinds of environmental stability, and are less likely to suffer threats to life from their own atmosphere, their star, their solar system, and the galaxy, than are worlds like Earth, which have their oceans on the outside,” said Stern.

He also points out that the same layer of rock and ice that protects the oceans on IWOWs also conceals life from being detected by virtually all astronomical techniques. If such worlds are the predominant abodes of life in the galaxy and if intelligent life arises in them — both big “ifs,” Stern emphasizes — then IWOWs may also help crack the so-called Fermi Paradox. Posed by Nobel Laureate Enrico Fermi in the early 1960s, the Fermi Paradox questions why we don’t see obvious evidence of life if it’s prevalent across the universe.

“The same protective layer of ice and rock that creates stable environments for life also sequesters that life from easy detection,” said Stern.

In 2015, NASA created the Ocean Worlds Exploration Program, which seeks to explore an ocean world to determine habitability and seek life. Moons that harbor oceans under a shell of ice, such as Europa and Titan, are already the targets of NASA missions to study the habitability of these worlds.

The paper, “Some Implications for Both Life and Civilizations Regarding Interior Water Ocean Worlds” at LPSC 52 is available here (PDF).

Meeting: 52nd annual Lunar and Planetary Science Conference (LPSC 52)