This image shows the far side of the Moon, illuminated by the Sun. Credit: NASA
A team of researchers from the U.K., France and the U.S. has found evidence that suggests that most of the water on Earth was present before the impact that created the moon. In their paper published on the open access site Science Advances, the group describes their study and comparison of moon and Earth rocks, and what they found.
The prevailing theory regarding how the moon’s origin is that a Mars-sized protoplanet slammed into protoplanetary Earth, and the ejected material coalesced to form the moon. The prevailing theory regarding how water came to exist on Earth is that most of it was delivered by asteroids and comets. In this new effort, the researchers present evidence that bolsters the first theory but conflicts strongly with the second.
The team studied both moon rocks brought back to Earth by the Apollo astronauts and volcanic rocks retrieved by others from the ocean floor. The researchers looked specifically at oxygen isotopes. Studying isotopes in rocks offers scientists a means for comparing material from different origins such as asteroids, planets or even comets—each tends to have its own unique composition signature.
The researchers report that oxygen isotopes from the moon and Earth are remarkably similar—they found just a three to four ppm difference between them. This finding bolsters the theory that the moon was formed from material from the Earth due to a collision. But it runs counter to the idea that water came from comets or asteroids, because if it had come from such sources, the isotopes would have differed from those found in rocks on the moon. Thus, most of the water that was present in the protoplanetary Earth likely survived the impact, suggesting it did not come from elsewhere.
The idea that water could survive such an impact has implications for the search for life beyond our solar system—exoplanets that are thought to have suffered collisions are typically removed from lists describing possible life-sustaining celestial bodies. Now, they may have to be included.
For six years Sarbjit Kaur Athwal was in fear, knowing her sister-in-law had been murdered. She explains how she found the courage to alert police
The Sunday Times
One seemingly normal Friday afternoon, Sarbjit Kaur Athwal was summoned by her husband to a meeting. When she walked into the living room of the Sikh family’s west London home, her mother-in-law was already settled on the sofa.
“It’s too much. I can’t handle it — people are talking,” Bachan Kaur Athwal hissed. “We have to get rid of her.” She was referring to Surjit, Sarbjit’s sister-in-law.
Sarbjit immediately grasped the significance of her words. Appalled, she listened as her husband, Hardave, made a lacklustre attempt at changing his mother’s mind, but Bachan, a widow, slapped his arguments away with a deft flick of the hand. “It’s decided.”
Within weeks of that meeting, Surjit — a vivacious mother of two — was dead, her body carried away by the Ravi river in northwest India.
Sitting in the lounge of her bright new Surrey home, Sarbjit has not only escaped her former life but has also become the first person from within a murderer’s family to appear as a key witness in open court in an honour killing trial.
Her testimony at the Old Bailey in 2007 led to the conviction of Bachan and her son Sukhdave for the killing of Surjit, his wife, and to a new focus on combating honour crimes — far too often covered up by misplaced family loyalties. Surjit’s children, who had stayed with their murderer father for nine years, went to live with an aunt.
Sarbjit’s brown eyes, framed by jet black hair, grow animated as she talks about the book she has written about her fight for justice. Like Surjit, Sarbjit had gone to live with the Athwal family after marrying one of Bachan’s sons, and the two women had grown close. “She was really sweet. She made me feel welcome. We did the cooking together and looked after the house.”
The women found their mother-in-law controlling. She would accompany Sarbjit and Hardave on dinner dates, and once Sarbjit got a job, Bachan insisted that her salary go towards the cost of having her under the roof. “There was no freedom. If I wanted to go out and buy something I had to ask my husband.” After she voiced her frustration to Surjit, her sister-in-law gave her some steely advice. “If you want to live in this family, then you’ve got to toughen up a bit.”
While Sarbjit was a docile, obedient wife, Surjit was searching for her own identity. “She wanted to go out and explore; she wanted a bit more from life,” Sarbjit says. Surjit got a job as a customs officer at Heathrow and began to socialise with her colleagues. Her husband and mother-in-law disapproved.
Bachan raged when Surjit went out in make-up and western clothes rather than traditional Sikh dress. She was horrified that her daughter-in-law drank alcohol and cut her hair. “She would vent her anger at her son, who would then shout at Surjit,” Sarbjit recalls.
Surjit grew more and more unhappy in her marriage and Sarbjit, through the walls of her bedroom, would hear her and her husband shouting at each other. Sukhdave became physically abusive and although Surjit left a few times, the family always lured her back home. With no sign of Surjit conforming and a divorce imminent, Bachan grew ever more desperate to stop her daughter-in-law “bringing shame on the family”. And so she hatched her plan to take Surjit to India.
When Bachan proposed the idea of Surjit as her chaperone for an Indian wedding in 1998, Sarbjit willed her sister-in-law to refuse. Yet Surjit was swayed by her mother-in-law’s promise of a shopping spree and celebration for her newly born son on her return.
Sarbjit wanted to warn Surjit but Bachan never left the two women alone. “I was scared. I was threatened and told to keep quiet but I was hoping I could do something. I didn’t get a chance to speak to her. Even the day she left I was hoping that I could have time with her. I went to the door and waited for her to come out but Bachan Kaur spotted me and told me to go inside.” She pauses for a few moments, before adding quietly: “There was nothing I could do. I was helpless.”
That morning she had plucked up the courage to leave the house and call Crimestoppers from a public payphone. She was petrified someone would spot her and tell her family. “I told them everything without revealing my name. ‘This is what they are going to do. Please can you do something.’ But nothing happened.”
Over the next few days Sarbjit waited anxiously for news and repeatedly asked her husband about Surjit. “Don’t talk about it; keep quiet,” was his standard refrain. Two weeks later her mother-in-law returned from India alone. “She came into our house, she sat on the sofa and she looked at me. ‘What’s happened?’ I asked. I knew what was coming. She got quite emotional and said, ‘It’s all done now. It’s all done. Surjit is gone.’”
Bachan revealed that Surjit had been picked up by her brother and another man, who, once on a quiet stretch of road, had drugged and strangled her before discarding her body in the river.
Sarbjit, who has four children, clears her throat before continuing. “My heart sank. I thought, ‘I’m sitting opposite a woman who has just killed someone.’” Bachan reminded her not to mention the murder to anyone. The implication was obvious to Sarbjit: “This is what I’m capable of; this is what I’ve done to my other daughter-in-law. Just be careful.”
Sarbjit felt compelled to report the murder, despite the risks. She wrote an anonymous letter describing all the details and dropped it into her local police station. Yet again the police failed to act.
Six years passed, and Sarbjit, still under her mother-in-law’s control, felt increasingly distraught about the murder and weighed down by the stress and fear of what her family might do to her. She developed a stomach ulcer that almost killed her. “The pressure had been building up — it was just too much,” Sarbjit says. “I thought constantly of suicide, hesitating only because of my children.”
After a stint in hospital in 2004 she asked her parents to take her to their home so she could recuperate. She finally unburdened herself to her father and he called the police. “I was really scared, as the police had let me down.”
Yet with Sarbjit’s courageous testimony the police felt they had sufficient evidence to prosecute Bachan and Sukhdave. That evening a newspaper reported a breakthrough in the case and Sarbjit was terrified that her in-laws would link her to the breakthrough. “My husband was saying, ‘Please, if you’ve said anything, let me know.’ I think by then he knew what I had done.”
Before the trial in 2007 she faced great intimidation from her husband and other members of the Sikh community — but she held firm. The day of her testimony was incredibly difficult: “As soon as I entered the court I saw Bachan Kaur and Sukhdave right in front of me. My knees went weak and I was thinking, ‘I’ve got to give evidence but I can’t do it.’” She asked for a screen but the judge refused. The police reminded her of the importance of getting justice for Surjit and she conquered her nerves.
Days later the jury returned their verdict. The pair were found guilty and sentenced to life in prison. Six years on, Sarbjit still receives threats from the Sikh community. She and Hardave are divorced. But she has taken inspiration from the police officers who helped her and for a time she worked as a police community support officer.
She is proud of her work and her children, who are thriving. “For the record, should any of them ask for an arranged marriage, they definitely will not be getting one.”
Shamed, by Sarbjit Kaur Athwal, is published by Virgin
The discovery of an eighth planet circling the distant star Kepler-90 by University of Texas at Austin astronomer Andrew Vanderburg and Google’s Christopher Shallue overturns our solar system’s status as having the highest number of known planets. We’re now in a tie.
The newly discovered Kepler-90i—a sizzling hot, rocky planet orbiting its star once every 14.4 days—was found using computers that “learned” to find planets in data from NASA’s Kepler space telescope. Kepler finds distant planets beyond the solar system, or exoplanets, by detecting the minuscule change in brightness when a planet transits (crosses in front of) a star.
Vanderburg, a NASA Sagan fellow at UT Austin, and Shallue, a Google machine learning researcher, teamed up to train a computer to learn how to identify signs of an exoplanet in the light readings from distant stars recorded by Kepler. Similar to the way neurons connect in the human brain, this “neural network” sifted through the Kepler data to identify the weak transit signals from a previously missed eighth planet orbiting Kepler-90, a sun-like star 2,545 light-years from Earth in the constellation Draco.
“For the first time since our solar system planets were discovered thousands of years ago, we know for sure that our solar system is not the sole record holder for the most planets,” Vanderburg said.
Other planetary systems, though, would probably hold more promise for life than Kepler-90’s system, which packs all eight planets closer to the host star than Earth is to the sun. In our solar system, only Mercury and Venus orbit between our planet and our sun. About 30 percent larger than Earth, Kepler-90i is so close to its star that its average surface temperature is thought to exceed 800 degrees Fahrenheit, on a par with Mercury. The outermost planet, Kepler-90h, is a gas giant that is about the size of Jupiter, circling with a “year” of 331.6 days.
“The Kepler-90 star system is like a mini version of our solar system. You have small planets inside and big planets outside, but everything is scrunched in much closer,” Vanderburg said.
The research paper reporting this finding has been accepted for publication in The Astronomical Journal.
The idea to apply a neural network to Kepler data came from Shallue, a senior software engineer at Google AI, a research team at the search-engine giant in Mountain View, California. Shallue became interested in exoplanet discovery after learning that astronomy, like other branches of science, is rapidly becoming inundated with data as the technology for collecting data from space advances.
“Machine learning really shines in situations where there is so much data that humans can’t search it for themselves,” Shallue said.
Kepler’s four-year data set, for example, consists of about 2 quadrillion possible orbits of planets. To verify the most promising signals of planets, automated tests, or sometimes human eyes, are typically used, but often the weakest signals are missed during this process. So, Shallue and Vanderburg thought there could be some more interesting exoplanet discoveries lurking in the data.
The two developed a neural network to search Kepler data for new planets. First, they trained the neural network to identify transiting exoplanets in a set of 15,000 previously vetted signals from the Kepler exoplanet catalog. Then, with the neural network having “learned” to detect the pattern of a transiting exoplanet, the researchers pointed their model at 670 star systems that already had multiple known planets and searched for weaker signals. Their assumption was that multiple-planet systems would be the best places to look for more exoplanets.
Kepler-90 had already made its mark in 2013 as the first seven-planet system identified with Kepler, but the signal from the eighth planet was so weak it was missed by previous methods.
“We got lots of false positives of planets but also potentially more real planets,” Vanderburg said. “It’s like sifting through rocks to find jewels. If you have a finer sieve, then you will catch more rocks, but you might catch more jewels as well.”
Kepler-90i wasn’t the only jewel this neural network sifted out. In the Kepler-80 system, they found a sixth planet. This one, the Earth-size Kepler-80g, and four of its neighboring planets form what is called a “resonant chain,” where the planets are locked by their mutual gravity in a rhythmic orbital dance. The result is an extremely stable system, similar to the seven planets in the TRAPPIST-1 system, so precisely balanced that the length of Kepler-80g’s year could be predicted with mathematics.
A laser-driven technique for creating fusion that dispenses with the need for radioactive fuel elements and leaves no toxic radioactive waste is now within reach, say researchers.
Dramatic advances in powerful, high-intensity lasers are making it viable for scientists to pursue what was once thought impossible: creating fusion energy based on hydrogen-boron reactions. And an Australian physicist is in the lead, armed with a patented design and working with international collaborators on the remaining scientific challenges.
In a paper in the scientific journal Laser and Particle Beams today, lead author Heinrich Hora from the University of New South Wales in Sydney and international colleagues argue that the path to hydrogen-boron fusion is now viable, and may be closer to realization than other approaches, such as the deuterium-tritium fusion approach being pursued by U.S. National Ignition Facility (NIF) and the International Thermonuclear Experimental Reactor under construction in France.
“I think this puts our approach ahead of all other fusion energy technologies,” said Hora, who predicted in the 1970s that fusing hydrogen and boron might be possible without the need for thermal equilibrium. Rather than heat fuel to the temperature of the Sun using massive, high-strength magnets to control superhot plasmas inside a doughnut-shaped toroidal chamber (as in ITER), hydrogen-boron fusion is achieved using two powerful lasers in rapid bursts, which apply precise non-linear forces to compress the nuclei together.
Hydrogen-boron fusion produces no neutrons and, therefore, no radioactivity in its primary reaction. And unlike most other sources of power production – like coal, gas and nuclear, which rely on heating liquids like water to drive turbines – the energy generated by hydrogen-boron fusion converts directly into electricity. But the downside has always been that this needs much higher temperatures and densities – almost 3 billion degrees Celsius, or 200 times hotter than the core of the Sun.
However, dramatic advances in laser technology are close to making the two-laser approach feasible, and a spate of recent experiments around the world indicate that an ‘avalanche’ fusion reactioncould be triggered in the trillionth-of-a-second blast from a petawatt-scale laser pulse, whose fleeting bursts pack a quadrillion watts of power. If scientists could exploit this avalanche, Hora said, a breakthrough in proton-boron fusion was imminent.
“It is a most exciting thing to see these reactions confirmed in recent experiments and simulations,” said Hora, an emeritus professor of theoretical physics at UNSW. “Not just because it proves some of my earlier theoretical work, but they have also measured the laser-initiated chain reaction to create one billion-fold higher energy output than predicted under thermal equilibrium conditions.”
Together with 10 colleagues in six nations – including from Israel’s Soreq Nuclear Research Centre and the University of California, Berkeley – Hora describes a roadmap for the development of hydrogen-boron fusion based on his design, bringing together recent breakthroughs and detailing what further research is needed to make the reactor a reality.
An Australian spin-off company, HB11 Energy, holds the patents for Hora’s process. “If the next few years of research don’t uncover any major engineering hurdles, we could have prototype reactor within a decade,” said Warren McKenzie, managing director of HB11.
“From an engineering perspective, our approach will be a much simpler project because the fuels and waste are safe, the reactor won’t need a heat exchanger and steam turbine generator, and the lasers we need can be bought off the shelf,” he added
After training a network of telescopes stretching from Hawaii to Antarctica to Spain at the heart of our galaxy for five nights running, astronomers said Wednesday they may have snapped the first-ever picture of a black hole.
It will take months to develop the image, but if scientists succeed the results may help peel back mysteries about what the universe is made of and how it came into being.
“Instead of building a telescope so big that it would probably collapse under its own weight, we combined eight observatories like the pieces of a giant mirror,” said Michael Bremer, an astronomer at the International Research Institute for Radio Astronomy (IRAM) and a project manager for the Event Horizon Telescope.
“This gave us a virtual telescope as big as Earth—about 10,000 kilometres (6,200 miles) is diameter,” he told AFP.
The bigger the telescope, the finer the resolution and level of detail.
The targeted supermassive black hole is hidden in plain sight, lurking in the centre of the Milky Way in a region called the Sagittarius constellation, some 26,000 light years from Earth.
Dubbed Sagittarius A* (Sgr A* for short), the gravity- and light-sucking monster weighs as much as four million Suns.
Theoretical astronomy tells us when a black hole absorbs matter—planets, debris, anything that comes too close—a brief flash of light is visible.
No going back
Black holes also have a boundary, called an event horizon.
The British astronomer Stephen Hawking has famously compared crossing this boundary to going over Niagra Falls in a canoe: if you are above the falls, it is still possible to escape if you paddle hard enough.
Once you tip over the edge, however, there’s no going back.
The Event Horizon Telescope radio-dish network is designed to detect the light cast-off when object disappear across that boundary.
“For the first time in our history, we have the technological capacity to observe black holes in detail,” said Bremer.
The virtual telescope trained on the middle of the Milky Way is powerful enough to spot a golf ball on the Moon, he said.
The 30-metre IRAM telescope, located in the Spanish Sierra Nevada mountains, is the only European observatory taking part in the international effort.
Other telescopes contributing to the project include the South Pole Telescope in Antarctica, the James Clerk Maxwell Telescope in Hawaii, and the Atacama Cosmology Telescope in the desert of northern Chile.
All the data—some 500 terabytes per station—will be collected and flown on jetliners to the MIT Haystack Observatory in Massachusetts, where it will be processed by supercomputers.
“The images will emerge as we combine all the data,” Bremer explained. “But we’re going to have to wait several months for the result.”
Material scientists have predicted and built two new magnetic materials, atom-by-atom, using high-throughput computational models. The success marks a new era for the large-scale design of new magnetic materials at unprecedented speed.
Although magnets abound in everyday life, they are actually rarities—only about five percent of known inorganic compounds show even a hint of magnetism. And of those, just a few dozen are useful in real-world applications because of variability in properties such as effective temperature range and magnetic permanence.
The relative scarcity of these materials can make them expensive or difficult to obtain, leading many to search for new options given how important magnets are in applications ranging from motors to magnetic resonance imaging (MRI) machines. The traditional process involves little more than trial and error, as researchers produce different molecular structures in hopes of finding one with magnetic properties. Many high-performance magnets, however, are singular oddities among physical and chemical trends that defy intuition.
In a new study, materials scientists from Duke University provide a shortcut in this process. They show the capability to predict magnetism in new materials through computer models that can screen hundreds of thousands of candidates in short order. And, to prove it works, they’ve created two magnetic materials that have never been seen before.
The results appear April 14, 2017, in Science Advances.
“Predicting magnets is a heck of a job and their discovery is very rare,” said Stefano Curtarolo, professor of mechanical engineering and materials science and director of the Center for Materials Genomics at Duke. “Even with our screening process, it took years of work to synthesize our predictions. We hope others will use this approach to create magnets for use in a wide range of applications.”
The group focused on a family of materials called Heusler alloys—materials made with atoms from three different elements arranged in one of three distinct structures. Considering all the possible combinations and arrangements available using 55 elements, the researchers had 236,115 potential prototypes to choose from.
To narrow the list down, the researchers built each prototype atom-by-atom in a computational model. By calculating how the atoms would likely interact and the energy each structure would require, the list dwindled to 35,602 potentially stable compounds.
From there, the researchers conducted a more stringent test of stability. Generally speaking, materials stabilize into the arrangement requiring the least amount of energy to maintain. By checking each compound against other atomic arrangements and throwing out those that would be beat out by their competition, the list shrank to 248.
Of those 248, only 22 materials showed a calculated magnetic moment. The final cut dropped any materials with competing alternative structures too close for comfort, leaving a final 14 candidates to bring from theoretical model into the real world.
But as most things in a laboratory turn out, synthesizing new materials is easier said than done.
“It can take years to realize a way to create a new material in a lab,” said Corey Oses, a doctoral student in Curtarolo’s laboratory and second author on the paper. “There can be all types of constraints or special conditions that are required for a material to stabilize. But choosing from 14 is a lot better than 200,000.”
For the synthesis, Curtarolo and Oses turned to Stefano Sanvito, professor of physics at Trinity College in Dublin, Ireland. After years of attempting to create four of the materials, Sanvito succeeded with two.
Both were, as predicted, magnetic.
The first newly minted magnetic material was made of cobalt, magnesium and titanium (Co2MnTi). By comparing the measured properties of similarly structured magnets, the researchers were able to predict the new magnet’s properties with a high degree of accuracy. Of particular note, they predicted the temperature at which the new material lost its magnetism to be 940 K (1232 degrees Fahrenheit). In testing, the actual “Curie temperature” turned out to be 938 K (1228 degrees Fahrenheit)—an exceptionally high number. This, along with its lack of rare earth elements, makes it potentially useful in many commercial applications.
“Many high-performance permanent magnets contain rare earth elements,” said Oses. “And rare earth materials can be expensive and difficult to acquire, particularly those that can only be found in Africa and China. The search for magnets free of rare-earth materials is critical, especially as the world seems to be shying away from globalization.”
The second material was a mixture of manganese, platinum and palladium (Mn2PtPd), which turned out to be an antiferromagnet, meaning that its electrons are evenly divided in their alignments. This leads the material to have no internal magnetic moment of its own, but makes its electrons responsive to external magnetic fields.
While this property doesn’t have many applications outside of magnetic field sensing, hard drives and Random Access Memory (RAM), these types of magnets are extremely difficult to predict. Nevertheless, the group’s calculations for its various properties remained spot on.
“It doesn’t really matter if either of these new magnets proves useful in the future,” said Curtarolo. “The ability to rapidly predict their existence is a major coup and will be invaluable to materials scientists moving forward.”