From Harvard Astronomy via Science Alert: “Harvard Scientists Will Actually Launch a Geoengineering Experiment Next Year”

From Harvard Astronomy

via

Science Alert

(Johnson Space Centre/NASA)

4 DEC 2018
PETER DOCKRILL

Last month, new research from Harvard and Yale led to a flurry of news claiming scientists were proposing to ‘dim the Sun’ [Environmental Research Letters] in an “ingenious but as-yet-unproven way to tackle climate change”.

Only, they weren’t. As other outlets made clear, the paper was actually an analysis of whether solar geoengineering is technically and economically feasible, nothing more.

The funny thing is, though, those overblown headlines almost did get it right after all, even if only by accident.

As it happens, other Harvard scientists are indeed moving ahead with a groundbreaking plan to test the effects of solar geoengineering in the skies above our heads, and their US$3 million experiment could begin as early as next year [Nature].

The project – called the Stratospheric Controlled Perturbation Experiment (SCoPEx) – is part of Harvard’s Solar Geoengineering Research Program.

While most studies looking at the effects of spraying chemicals into the atmosphere to cool the planet rely on computer simulations to test their hypotheses, SCoPEx will conduct its testing in the real world.

In the experiment, a high-altitude balloon will fly up to the stratosphere, at an altitude of about 20 kilometres, and release a small aerosol plume of calcium carbonate.

Once the chemical payload is released, it’s expected to disperse into a perturbed air mass about 1 kilometre long and 100 metres in diameter. The balloon will then fly back and forth through this cloud repeatedly for about 24 hours, analysing the particles’ behaviour and evolution in the sky.

The reason we might want to do this is to see whether sunlight-reflecting particles in the atmosphere could cool down the surface of the planet, in an intentionally contrived recreation of the effects of a volcano eruption – most notably, the observed global cooling effects of the Mount Pinatubo eruption in 1991.

But solar geoengineering is not without its controversies. Some studies suggest spraying huge amounts of sunlight-reflecting particles into the atmosphere could have grave consequences, leading to unintended issues for things like crops, weather patterns, or the ozone layer.

The ozone layer in particular is one of the reasons the team behind SCoPEx is working with calcium carbonate – because their previous research indicated it could be the safest in terms of stratospheric chemistry.

That said, there’s still a huge amount we don’t know about what solar geoengineering might unleash, which is all the more reason to conduct small-scale experiments like SCoPEx, which will only release about the same amount of particulate as one minute of commercial airliner emissions.

“There are all of these downstream effects that we don’t fully understand,” atmospheric chemist and SCoPEx principal investigator Frank Keutsch told Nature.

As always, even if the experiments prove successful – and demonstrate that solar geoengineering is something we could potentially roll out on a larger scale – it’s not a silver bullet for global warming.

Drastically reducing existing levels of carbon emissions should still be humanity’s first response to climate change, because that’s the root cause of our heat-trapping problems – and solar geoengineering won’t be able to help other related issues, like ocean acidification.

“Solar reengineering is a supplement, and in the end we still have to cut emissions,” one of the team, applied physicist David Keith, said in 2016.

While the world takes care of that, scientists will be testing just what this supplement is capable of, and from the sounds of it, we won’t have to wait too long to find out if ‘dimming the Sun’ can help us.

A 2014 paper on the SCoPEx research is available here.

See the full article here .

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From UC Berkeley via Science Alert: “Earth Might Have Once Had a Different Kind of Magnetic Field, And It’s Good News For Life on Other Planets”

From UC Berkeley

(dottedhippo/iStock)

23 NOV 2018
MIKE MCRAE

A new study suggests that Earth might have once had a different kind of magnetic field – one generated by oceans of magma on its surface, instead of the rotation of its core.

And that’s good news, because it means more exoplanets than we thought could have a protective magnetic shield sheltering them from the harsh radiation of space, and a chance of hosting life.

According to the research, long before Earth had a skin, when its molten insides flowed on its outside and its heart was yet to harden, a magnetic cage was already beginning to bloom overhead.

An analysis of the electrochemistry of moving magma has found sufficiently sized oceans of liquid rock can generate their own magnetic fields, helping us understand not just our own planet’s history, but the chances of life arising on other worlds.

Two Earth and planetary scientists from UC Berkeley went back to first principles to simulate the surface conditions of young super-Earths – huge rocky worlds with sub-surface pressures and temperatures guaranteed to keep the planets toasty.

They found the make-up of these molten crusts could give rise to an electrical conductivity large enough to form a planetary dynamo, and it would take a current of rock flowing at a speed of just 1 millimetre per second to manage it.

“This is the first detailed calculation for higher temperature and pressure conditions, and it finds that the conductivities appear to be a little bit higher, so the fluid motions you would need to make this all work are maybe a little bit less extreme,” says planetary scientist Burkhard Militzer.

Our own world has a powerful dynamo churning away deep underfoot in the form of a rotating core of liquid iron and nickel swirling amid a gooey soup of lighter minerals and charged particles.

We should be super thankful for it – without it, we probably wouldn’t be here.

“A magnetic field is helpful in protecting a planetary atmosphere from being blown away by the stellar winds,” says co-author François Soubiran, now at the École Normale Supérieure in Lyon, France.

Not only do we need that atmosphere to keep the surface temperature constant and for life-sustaining chemical reactions, it shields the biosphere from lethal doses of radiation.

Magnetic fields also do a pretty good job of forming an umbrella that deflects high energy particles from bombarding the crust. So it’s a safe bet that no magnetic field equals no life.

Knowing which planets outside of our own Solar System can generate magnetic fields might help us sort those that are likely to be sterile from the handful that just might be worth studying for biology.

What’s more, categorising the different ways planets create magnetic fields opens the way to studying the geology of a planet without needing to set down on its surface.

“On Jupiter, it arises from the convection of liquid metallic hydrogen,” says Militzer.

“On Uranus and Neptune, it is assumed to be generated in the ice layers. Now we have added molten rocks to this diverse list of field-generating materials.”

Just how a surface dynamo might interact with core processes is still anybody’s guess, especially given we know so little about our planet’s interior.

“The interaction between the liquid core magnetic field and the magma ocean is not easy to predict, but could result in a significant – or even dominant – dipolar component,” the authors write.

Ideally, to form a protective bubble, a magnetic field should have a neat dipole shape, as opposed to a mess of loops like a poodle’s haircut.

Magnetosphere of Earth, original bitmap from NASA. SVG rendering by Aaron Kaase

This could be good news for anybody hoping to include super-Earths in their list of potential alien hotspots.

Most of these insanely big planets – massive rocky bodies that fall short of Neptune’s girth – tend to be pulled close to their temper-prone stars, where solar eruptions and constant heat would make short work of any atmosphere.

A sufficient dipole magnetic field would give some of them a fighting chance of holding onto precious air while shielding the surface from a scouring brush of solar activity.

Unfortunately any close proximity to a star also increases the chances such a world would be tidally locked, making its day and year more or less the same length. The team’s analysis suggests a distinct dipole formation would require a relatively rapid rotation, ruling out those slower-spinning worlds.

With the number of exoplanets in our library climbing into the thousands, and a number of Earth-like worlds among them, we’re going to need better ways to study them.

Hunting for hints of magnetic fields from afar could help us prioritise our search for life among the stars.

This research was published in Nature Communications.

See the full article here .

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Founded in the wake of the gold rush by leaders of the newly established 31st state, the University of California’s flagship campus at Berkeley has become one of the preeminent universities in the world. Its early guiding lights, charged with providing education (both “practical” and “classical”) for the state’s people, gradually established a distinguished faculty (with 22 Nobel laureates to date), a stellar research library, and more than 350 academic programs.

From Australian National University via Science Alert: “We’ve Found a Special Type of Light That Could Be a Crucial Ingredient For Life in The Universe”

From Australian National University

Science Alert

22 NOV 2018
MICHELLE STARR

A stellar nursery at the heart of the Tarantula Nebula. (NASA, ESA, P Crowther/University of Sheffield)

ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
•KUEYEN (UT2; The Moon ),
•MELIPAL (UT3; The Southern Cross ), and
•YEPUN (UT4; Venus – as evening star).
elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo

The most extreme of these stars was found in the cluster RMC 136a (or R136 as it is more usually named). Named R136a1, it is found to have a current mass of 265 times that of the Sun. Being a little over a million years old, R136a1 is already “middle-aged” and has undergone an intense weight-loss programme, shedding a fifth of its initial mass over that time, or more than fifty solar masses. It also has the highest luminosity, close to 10 million times greater than the Sun. R136 is a cluster of young, massive and hot stars located inside the Tarantula Nebula, in one of the neighbourhood galaxies of the Milky Way, the Large Magellanic Cloud, 165 000 light-years away.

Large Magellanic Cloud. Adrian Pingstone December 2003

R136 contains so many stars that on a scale equivalent to the distance between the Sun and the nearest star there are tens of thousands of stars. Hundreds of these stars are so incredibly bright that if we were to sit on a (hypothetical) planet in the middle of the cluster the sky would never get dark. This montage shows a visible-light image of the Tarantula nebula as seen with the Wide Field Imager on the MPG/ESO 2.2-metre telescope (left) along with a zoomed-in visible-light image from the Very Large Telescope (middle).

Wide Field Imager on the 2.2 Meter on the 2.2 meter MPG/ESO telescope at Cerro LaSilla Wide Field Imager on the 2.2 meter MPG/ESO telescope at Cerro LaSilla Wide Field Imager on the 2.2 meter MPG/ESO telescope at Cerro LaSilla

MPG/ESO 2.2 meter telescope at Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres

ESO MAD on the VLT Unit 3

If life is to spark in the Universe like it does on Earth, a few things seem to be required, such as an atmosphere, ozone layer, liquid water, and habitable temperatures.

But before it ever gets to that point – before planets even form – space itself needs to be primed, courtesy of ultraviolet and optical light shining from massive, newly formed stars.

According to new research, this particular form of starlight provides a type of pressure that counteracts gravity, which slows down the rate of a galaxy’s star formation.

“If star formation happened rapidly, all stars would be bound together in massive clusters, where the intense radiation and supernova explosions would likely sterilise all the planetary systems, preventing the emergence of life,” explained astrophysicist Roland Crocker of the Australian National University.

“The conditions in these massive star clusters would possibly even prevent planets from forming in the first place.”

Gravity is vital to star formation. Most stars are born in stellar nurseries – dense molecular clouds in space that are rich with dust and gas. As interstellar winds and sometimes gravitational shockwaves ripple through, the material gets pushed into denser clumps, which then collapse under their own gravitational attraction.

These collapsed lumps continue to subsume surrounding material, rapidly growing in mass until nuclear fusion causes them to shine with light.

According to the paper by Crocker and his team, the very act of emitting starlight drives gas out of dense, isolated stellar protoclusters undergoing a furious rate of star formation, preventing them from further coalescing.

The ultraviolet and optical light from new massive stars scatters among the gas. The absorption of photons by the gas creates direct radiation pressure, whereas photons absorbed by the gas and re-emitted as infrared light create indirect radiation pressure.

Combined, the two types of radiation pressure can constitute a source of feedback – the process whereby star formation is quenched. This can also come from the powerful winds originating around an active supermassive black hole at a galaxy’s core.

“The phenomenon we studied occurs in galaxies and star clusters where there’s a lot of dusty gas that is forming heaps of stars relatively quickly,” Crocker said.

“In galaxies forming stars more slowly – such as the Milky Way – other processes are slowing things down. The Milky Way forms two new stars every year, on average.”

This is not a newly discovered process, but the mathematical modelling performed by Crocker and his team have put an upper limit on how quickly new stars can form. They found it takes significantly more than half the material in a molecular cloud to have been converted to stars for direct radiation pressure to push the remaining gas away.

“This and other forms of feedback help to keep the Universe alive and vibrant,” Crocker said.

The paper has been published in the journal Monthly Notices of the Royal Astronomical Society.

See the full article here .

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ANU is a world-leading university in Australia’s capital city, Canberra. Our location points to our unique history, ties to the Australian Government and special standing as a resource for the Australian people.

Our focus on research as an asset, and an approach to education, ensures our graduates are in demand the world-over for their abilities to understand, and apply vision and creativity to addressing complex contemporary challenges.

From Science Alert: “Astronomers Found a Black Hole Rotating So Fast, It Could Be Spinning Space Itself”

From Science Alert

8 NOV 2018
PRABHJOTE GILL

(keanu2/iStock)

Black holes, while fascinating, are hardly a new discovery – but a black hole spinning at one of the highest speeds ever, according to the Hindustan Times, is a completely different story – especially when there have only ever been four others like it.

In 2016, India’s first dedicated astronomy satellite, the AstroSat, spotted a black hole in the binary star system called 4U 1630-47, which is bursting out X-rays that astronomers found unusual.

ISRO Astrosat India

NASA’s Chandra X-Ray Observatory later confirmed the outburst.

NASA/Chandra X-ray Telescope

Those X-rays were caused by gas and dust falling into the black hole, which is about 10 times the mass of the Sun, and they revealed to researchers that the object is spinning very, very rapidly.

In fact, according to NASA this particular black hole is spinning very close to the limit set by Albert Einstein’s theory of relativity, according to Rodrigo Nemmen, the lead author on the research paper. That means it is spinning close to the speed of light.

Currently, scientists only have two ways of measuring black holes – either by their mass or by their spin rate. A spin rate can be anywhere between 0 and 1: this black hole was spinning at the rate of 0.9.

Einstein’s theory further implies that if a black hole is spinning that fast, then it is capable of making space itself rotate.

In fact, if the conditions around black holes are hypothesised to be correct, then the high spin rate coupled with the gaseous elements entering the black hole and high temperatures, could be the key to understanding how galaxies are formed.

Including the black hole discovered by the AstroSat, there are only five black holes that have accurately measured high spin rates. Even if you’re not taking spin rates into account, this black hole is one of only 20 others that have been spotted in the Milky Way galaxy.

The Indian Space Research Organisation’s (ISRO) AstroSat along with the National Aeronautics and Space Administration’s (NASA) Chandra X-Ray Observatory have confirmed the speed of the spinning black hole.

The study was conducted by researchers from multiple institutions led by the Tata Institute of Fundamental Research (TIFR) and has been accepted for publication in The Astrophysical Journal.

See the full article here .

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From Science Alert: “CERN’s About to Release Details on Tantalising ‘Bumps’ in Large Hadron Collider Data”

From Science Alert

1 NOV 2018
MICHELLE STARR

Strap yourselves in, because CERN has something up its sleeve.

On Thursday 1 November, Large Hadron Collider (LHC) physicists will be discussing the fact that they may have found a new and unexpected new particle.

“I’d say theorists are excited and experimentalists are very sceptical,” CERN physicist Alexandre Nikitenko told The Guardian. “As a physicist I must be very critical, but as the author of this analysis I must have some optimism too.”

The telltale signal is a bump in the data collected by the LHC’s Compact Muon Solenoid (CMS) detector as the researchers were smashing together particles to look for something else entirely.

CERN/CMS Detector

When heavy particles – such as the Higgs Boson – are produced through particle collisions, they decay almost immediately. This produces a shower of smaller mass particles, as well as increased momentum, which can be picked up by the LHC’s detectors.

CERN CMS Higgs Event

CERN ATLAS Higgs Event

When these particle showers produced pairs of muons (a type of elementary particle that is similar to an electron but with a much higher mass), the team sat up and paid attention. But what they traced these pairs back to was, to be very scientific about it, mega weird.

The new and unknown particle that seems to have produced the muons has a mass of around 28 GeV (giga-electronvolts), just over a fifth of the mass of the Higgs boson (125 GeV).

There’s nothing in any of the current models that predicts this mass.

It’s unlikely to be physics-breaking, sorry to disappoint. But it is strange – a mass that has formed where no mass was expected.

A word of caution, though: it’s too early to get excited.

The signal could just be a glitch in the data, generated from random noise, which ended up being the case with what had been a tremendously exciting 750 GeV signal in 2016 – until it was found to be just a statistical fluctuation.

Until this data has been checked against newer CMS data, as well as data from the ATLAS detector, the discovery remains unconfirmed.

CERN/ATLAS detector

Still, an anomalous detection is always interesting – so we’ll be tuning in tomorrow to see what the research team has to say when they give their talk.

You can also check out their paper – which has yet to be peer-reviewed – on pre-print resource arXiv.

See the full article here .

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From Science Alert: “Astronomers Have Detected a Ghostly Dust Cloud Orbiting Our Earth”

From Science Alert

29 OCT 2018
PETER DOCKRILL

(J. Slíz-Balogh) The L5 point, with central region of the Kordylewski cloud visible in bright red pixels (J. Slíz-Balogh)

For decades the existence of weird space clouds in Earth’s orbit has been speculative and controversial, but new research looks to validate their strange reality after all.

The Kordylewski clouds – two mysterious swarms of dust trapped between the competing gravitational fields of Earth and the Moon – were first hypothesised back in the 1950s, although evidence for their existence was faint.

Kordylewski clouds are large concentrations of dust that exist at the L4 and L5 Lagrangian points of the Earth–Moon system. They were first reported by Polish astronomer Kazimierz Kordylewski in the 1960s, and confirmed to exist in October 2018.

Now, a new study by researchers at Eötvös Loránd University in Hungary helps make the case for these unusual, ever-present satellites in the sky.

“The Kordylewski clouds are two of the toughest objects to find, and though they are as close to Earth as the Moon, [they] are largely overlooked by researchers in astronomy,” says first author of the study, astronomer Judit Slíz-Balogh.

“It is intriguing to confirm that our planet has dusty pseudo-satellites in orbit alongside our lunar neighbour.”

The Kordylewski clouds have been speculated about for decades, but the science that underpins their existence goes back even longer.

In space, the Kordylewski clouds occupy positions that are called Lagrange points – locations where small objects get stuck in a gravitational nexus between the forces exerted by two larger bodies.

Lagrange points were first discovered in the 18th century, and there are five of these co-orbital points in any applicable system, such as the Sun-Earth system, the Earth-Moon system, and many others.

In the case of the Earth-Moon system, two of these five points – L4 and L5, sometimes called trojan points – form an equal-sided triangle with Earth and the Moon.

Theoretically, interplanetary particles could be trapped inside these points forever, were it not for the gravitational perturbation of even greater bodies (such as the Sun, in this instance) or other destabilising forces (like solar wind) eventually coaxing them out into the open.

In 1961, Polish astronomer Kazimierz Kordylewski became the first scientist to claim photographic evidence of this dust accumulation phenomenon, although the extreme faintness of dust almost 400,000 kilometres (about 250,000 miles) away makes such observations difficult to confirm.

Artist’s impression of Kordylewski cloud in the night sky (G. Horváth)

Nonetheless, that’s what Slíz-Balogh’s team set out to do in their new research.

In the first paper of a two-part study, the researchers modelled how Kordylewski clouds (KDC) might form, with almost 2 million particle simulations confirming that swathes of interplanetary dust would become trapped at L5, if only temporarily, before making an escape days later, depending on orbital configurations.

“According to our computer simulations, the KDC has a continuously changing, pulsing, and whirling shape, furthermore, the probability of dust particles being trapped is random due to the occasional incoming of particles and their incidental velocity vectors,” they write.

“Therefore, the structure and particle density of the KDC is not constant.”

In the second part of their research, the researchers attempted to photograph the phenomenon themselves.

After several months of perseverance – waiting for a sufficiently cloudless and moonless night in Hungary – the team captured evidence of the Kordylewski cloud at L5, using a technique called sequential imaging polarimetry to detect the extreme faintness of the particles.

“Since this dust cloud is illuminated by direct sunlight, the faint light scattered from the dust particles can be observed and photographed from the Earth surface with appropriately radiance-sensitive detectors,” the authors explain.

“We conclude that for the first time we have observed and registered polarimetrically the KDC around the Lagrange point L5 of the Earth and Moon.”

As for now, photographic evidence of the same accumulation taking place at L4 is something that still has to be regarded as hypothetical, but the new research makes a strong case that Kordylewski got it right almost 60 years ago.

In the longer term, there’s a lot more than just interplanetary particles swirling around here.

In the same way that natural orbital satellites congregate at L4 and L5 points, there’s a history of spacecraft exploiting the same phenomena, using Lagrange points as stable zones for things like probes and space telescopes.

Pretty handy parking spots to know about, if you don’t mind a bit of dust.

The findings are reported in the Monthly Notices of the Royal Astronomical Society here and here.

See the full article here .

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From Science Alert: “The USGS Has Just Listed These 18 North American Volcanoes as “Very High” Risk”

From Science Alert

26 OCT 2018
MIKE MCRAE

The US Geological Survey (USGS) has recently updated their assessment of potentially threatening volcanoes across the nation, making changes in light of more than a decade of fresh research.

First, the good news: all of that data has revealed a handful of volcanoes with minimal threat of causing wanton destruction can now be crossed off the list altogether.

The bad news? There are still 18 bad boys to keep a close eye on. And it’s probably not a huge surprise that 16 out of those are on the North American west coast.

The last time the USGS ranked volcanic threats was back in 2005. A lot has been discovered about geology since then, so the National Volcanic Threat Assessment figured it was time to go back to the list and double check their sums.

Given the US is one of the most volcanically active nations on the planet, eruptions are a way of life. Just ask Hawaii, which saw some spectacular displays from Kīlauea volcano earlier this year.

Kilauea volcano (Photo: U.S. Geological Survey via EPA-EFE)

An aerial view of the erupting Pu’u ‘O’o crater on Hawaii’s Kilauea volcano taken at dusk on June 29, 1983.
Credit: G.E. Ulrich, USGS

A calmer scene at Hawaii’s Kilauea volcano. Approximately August 8, 2018(United States Geological Survey)

Then there are those occasional cataclysmic time bombs on the North American continent itself, like Mount St. Helens in Washington, which took the lives of 57 people nearly 40 years ago.

Knowing which mountains are going to blow sky high in a local apocalypse and which are likely to be smoking duds informs authorities on how to plan for the worst.

So the USGS categorises volcanoes according to numerous factors that describe their threat, as either very low, low, moderate, high, and very high.

These levels don’t so much as describe their chances of erupting any time soon, as much as their impact should they did awaken in a pyrotechnic blaze of molten rock and ash plumes.

There’s the obvious lava flows and flying boulders to contend with, but billowing clouds of dust particles can interfere with air traffic, potentially costing hundreds of millions in cancelled flights and rerouting.

That’s not to mention toxic gases and fine particulates polluting the atmosphere, increasing health risks. Long after the fireworks die away, volcanoes can still cause immense damage in a variety of ways, depending on their remoteness.

Take Imuruk Lake for example. Its volcano sits out in the Alaskan wilds, where any ash-laden plume is unlikely to interfere with aircraft. Last seeing action around 300 CE, it’s way down the bottom of the list of potential threats at number 161.

It joins 20 other volcanoes in the lowest threat category, which now contains 11 fewer occupants than in the 2005 assessment.

All up, 20 volcanoes have had their risk demoted or removed altogether following their revaluation. Mt Washington in Oregon is now considered dead as a dodo, and just as likely to come back. So has the state’s Four Craters lava field.

But the 18 red-alert monsters that sit in the list of highest threats are the same ones that were identified in 2005.

Number one should come as no surprise. Kīlauea’s latest activity saw more than 700 homes and businesses destroyed, making it the most threatening volcano the US has to contend with right now.

Washington’s Mt Saint Helens and Mt Rainier follow close behind, with Redoubt Volcano in Alaska at number four and California’s Mt Shasta at number five.

Looking at the top 25, people might be somewhat relieved to see that the much-feared Yellowstone caldera doesn’t make the riskiest top 18, sitting at 21.

If you’re seeing a pattern, most of the most severe threats are on the US West Coast, with three of the 18 in California, five in Alaska, four in Washington and another four in Oregon.

None of this means it’s time to pack up and head to Florida. We wouldn’t recommend it anyway, what with their human-sized lizards prowling neighbourhoods, toxic algal blooms, and annual tropical storms building up steam.

But it does give scientists a better idea of what to prioritise in their research, and governments a good sense of where to put their money.

As populations swell, air traffic increases, and new kinds of technology and infrastructure stretch across the nation, there’s no doubt we’ll be seeing more additions to the high threat categories in future editions of the assessment.

Thankfully somebody is keeping a close eye on these sleeping giants.

See the full article here .

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From Science Alert: “Dark Matter Could Be Forming Strange Cold ‘Stars’ Out There in The Universe”

From Science Alert

25 OCT 2018
MIKE MCRAE

(pixelparticle/iStock)

Deep inside the diffuse haze of gas and dust that surround the smallest galaxies, dark matter could be clumping into cold droplets called ‘Bose stars’.

Of course, we don’t even know what the mysterious dark matter is, let alone have evidence of invisible ‘stars’. But if current assumptions pan out, a new mathematical model suggests dark matter might have some strange interactions.

Women in STEM – Vera Rubin

Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster

Coma cluster via NASA/ESA Hubble

But most of the real work was done by Vera Rubin

Fritz Zwicky from http:// palomarskies.blogspot.com

Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)

Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)

Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

The model was proposed by a team of Russian physicists who considered the way hypothetical particles of dark matter might aggregate in the smallest of galactic halos.

“In our work, we simulated the motion of a quantum gas of light, gravitationally interacting dark matter particles,” says physicist Dmitry Levkov from the Institute for Nuclear Research of the Russian Academy of Sciences.

Around 80 percent of the mass in the Universe is made of something we can’t seem to detect. Whatever it is, it doesn’t interact with normal matter through the usual channels, such as by exchanging photons via the electromagnetic field.

The only sign of its presence is the added oomph it adds to the clumping of galaxies. Still, that’s no small thing – this unseen gravitational tax has already been mapped out in detail, providing us with key information on its nature.

Thanks to its clear affinity for galaxies, we can assume the speed of the stuff making up dark matter isn’t fast enough to shoot off into the voids of space. It has to be relatively slow moving.

One candidate for this sluggish dark matter is a hypothetical particle called an axion. They’re a type of boson – not unlike the photon – that was proposed as a solution for another perplexing paradox in quantum physics.

Dark Matter map by Chihway Chang of the Kavli Institute for Cosmological Physics, University of Chicago, DES collaboration

Inside the ADMX experiment hall at the University of Washington Credit Mark Stone U. of Washington

Another option is fuzzy dark matter. It’s yet another type of boson, invented as a solution to a dilemma in astrophysics concerning the distribution of dark matter in galactic haloes.

Neither of these bespoke bosons have been shown to exist. But if at least one of them turned out to be real, under some circumstances they could do some interesting things.

The authors claim the model is the first to look at the kinetics of such a dark matter Bose-Einstein condensate actually forming.

Bose-Einstein condensates are the Anonymous rallies of quantum particles. When the temperature drops to just above absolute zero, particles quit mixing and lose their individual identities to look eerily the same.

Previous attempts have stuck to asking what happens when the bosons have already come together, such as in an infant Universe. In this case, they began with a jumble of interacting bosons.

“We started from a virialised state with maximal mixing, which is kind of opposite to the Bose-Einstein condensate,” says Levkov.

“After a very long period, 100,000 times longer than the time needed for a particle to cross the simulation volume, the particles spontaneously formed a condensate, which immediately shaped itself into a spherical droplet, a Bose star, under the effect of gravity.”

In effect, a cloud of ‘dark’ bosons becomes the same particle. Not only that, the physicists have worked out this cloud can pull together under gravitational effects to form a globe – a Bose ‘star’.

The conditions for these hypothetical objects would need to be fairly specific, such as concentrated in the middle of the relatively small halo surrounding a dwarf galaxy. And even then, while it should take place within the lifetime of the Universe, it would still be a slow process.

These kinds of ‘what if?’ scenarios might sound a little sci-fi, but they help us improve boundaries on where to hunt for clues on this whole dark matter mystery.

“The next obvious step is to predict the number of the Bose stars in the Universe and calculate their mass in models with light dark matter,” says Levkov.

One day we will finally have a grasp on the fundamental nature of this ghostly mass. When we do, we’re almost certainly going to find some fascinating new structures hiding in plain view among the stars.

This research was published in Physical Review Letters.

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From Science Alert: “Massive Sinkhole in China Has Led to The Discovery of a ‘World Class’ Geological Wonder”

From Science Alert

23 OCT 2018
MICHELLE STARR

(Euronews/YouTube)

A expedition to explore a giant sinkhole in the forest of Guangxi, China has resulted in the discovery of a tremendous cave hall complex under the ground.
At 6.7 million cubic metres (236 million cubic feet), the cave’s volume is of a rare enormity, making it ‘world class,’ geological experts are reported as saying.

The expedition was a joint venture between China and the UK, led by Zhang Yuanhai of the Institute of Karst Geology of the Chinese Academy of Geological Sciences, and British Caving Association chairman Andy Eavis.

From 4 to 8 October, the 19-member team lowered themselves into the tiankeng – the Chinese name given to this type of unusually large sinkhole – using just a single rope. Once inside, they set about mapping the interior.

“This giant cave hall was actually discovered by the Hong Kong expedition last year, so it was named Hong Kong·Haiting Hall,” Zhang Yuanhai explained to Chinese news website Science and Technology Daily.

“This time we mainly determined its volume and world-class status through three-dimensional scanning.”

They discovered that the sinkhole pit is 100 metres (328 ft) wide and nearly 200 metres (656 ft) long, with a maximum depth of 118 metres (387 ft). Towards the southeast end, the slope collapses into a huge cave complex.

It contains corridors, halls, craters, collapsed rocks, stone pillars and a type of formation called cave pearls – small, round stones polished smooth by water and deposited in cave crannies, where they sit undisturbed.

A shaft in the large cave hall was found to connect to an underground river, which feeds into the nearby Panyang River.

The 3D scanning will also let geologists reconstruct how the sinkhole collapsed.

“Three-dimensional scanning found that Hong Kong·Haiting Hall has retained a lot of evidence of the collapse of the crater evolution, especially the traces of rock mechanics produced after the collapse, which are clearly visible, demonstrating the evolutionary characteristics of this tiankeng,” Zhang Yuanhai said.

Tiankengs are usually the result of the collapse of an underground cavern, which has slowly been eroded by geological forces, such as water.

For example, the 626 metre (2,054 ft) long Xiaozhai Tiankeng, or Heavenly Pit – the largest sinkhole in the world – formed over the the limestone Difeng cave, which had been carved out by a powerful underground river.

Xiaozhai Tiankeng (Wikimedia Commons/Public Domain)

It’s likely that Hong Kong·Haiting Hall was formed in a similar manner.

“These giant caves are natural caves, most of which are caused by collapses and are related to underground rivers,” said Zhang Yuanhai.

But he also added, “The formation of all caves is not a one-step process. They basically have a history of more than 2 million years.”

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From Australian National University via Science Alert: “For The First Time, We Have Confirmation That Earth’s Core Is Actually Solid”

From Australian National University

via

Science Alert

19 OCT 2018
MIKE MCRAE

(forplayday/iStock)

It’s also a bit squishy.

For the first time, geologists have confirmed that our planet’s inner core is indeed solid – although not quite as firm as previous models have suggested.

Thanks to a new method for detecting soft whispers of seismic waves, analysis of an elusive type of earthquake ripple has revealed key properties of our planet’s deepest layer.

Researchers from the Australian National University (ANU) zeroed in on a low amplitude ‘J-phase’ seismic wave that passes through the planet’s core, allowing them to finally put constraints on its solidity.

As the planet’s crust grinds and groans on the surface, waves of energy are sent rippling their way through its gooey insides.

These come in various forms. Some, described as compressional waves, push back and forth through the planet’s body like a series of jittering train carriages. Others, called shear waves, surge up and down like the ocean’s surf along surfaces.

How one converts into the other according to various phase changes can tell you a lot about the properties of the material it’s passing through.

One particular variation called a J-phase should pass through the planet’s inner core, picking up details of the layer’s elasticity. That’s always been the theory, at least. The only problem is they’re rather quiet, making them virtually impossible to detect, so geologists have seen their measurement as something of a ‘Holy Grail’ of seismology.

Two ANU Earth scientists have now worked out a clever way to listen to these incredibly faint waves in the hum of earthquake vibrations echoing through our planet.

The method relies on taking any two seismic receivers on the planet’s surface and comparing notes several hours after the loudest rumbles have died away. With enough pairs of signals, a pattern can emerge.

“Using a global network of stations, we take every single receiver pair and every single large earthquake – that’s many combinations – and we measure the similarity between the seismograms,” says researcher Hrvoje Tkalčić.

“That’s called cross correlation, or the measure of similarity. From those similarities we construct a global correlogram – a sort of fingerprint of the Earth.”

A similar process was recently used [Journal of Geophysical Research:Solid Earth] to accurately measure the thickness of ice in Antarctica, providing a novel way to determine not just the properties of Earth’s layers, but potentially of other worlds as well.

Getting a grip on the nature of our planet’s guts is no easy task. We can barely dig more than 12 kilometres (about 7.5 miles) into the crust, which hardly scratches the surface, let alone reveals what’s thousands of kilometres underfoot.

A century ago, it was thought our planet had a thick crunchy outer coating and a gooey centre made of molten metals.

That all changed in the 1930s [American Museum of Natural History], following seismic readings of a large earthquake in New Zealand, which threw up signs of compression waves that shouldn’t have been there. A Danish seismologist by the name of Inge Lehmann suggested these patterns were most likely an echo bouncing off a solid centre.

This inner core has been firmly established in geological models of our planet’s structure. It’s about three quarters the size of our Moon, made of iron and nickel, and sizzles at a temperature roughly as hot as the Sun’s surface.

There might even be a complexity to its structure, with differences in how its iron crystals align giving the inner core its own ‘inner core’.

But even if all that is already established in geological models, it’s nice to now get firm evidence that scientists have been on the right track – besides, we got a bit of a surprise, too.

“We found the inner core is indeed solid, but we also found that it’s softer than previously thought,” says Tkalčić.

“It turns out – if our results are correct – the inner core shares some similar elastic properties with gold and platinum.”

All of this information is vital if we’re to build a firm understanding of phenomena like planetary formation, or how magnetic fields work.

Our own protective bubble of magnetism reverses regularly [PNAS], for example, and we still haven’t nailed down exactly how this happens.

“The understanding of the Earth’s inner core has direct consequences for the generation and maintenance of the geomagnetic field, and without that geomagnetic field there would be no life on the Earth’s surface,” says Tkalčić.

With a new way to listen to our planet’s rumbling, we’re almost certain to learn more about what its soft heart is telling us.

This research was published in Science.

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ANU is a world-leading university in Australia’s capital city, Canberra. Our location points to our unique history, ties to the Australian Government and special standing as a resource for the Australian people.

Our focus on research as an asset, and an approach to education, ensures our graduates are in demand the world-over for their abilities to understand, and apply vision and creativity to addressing complex contemporary challenges.