Light quark mass determines carbon and oxygen production and the viability of carbon-based life. Image credit: Dean Lee. Earth and Mercury images from NASA.
Life as we know it is based upon the elements of carbon and oxygen. Now a team of physicists, including one from North Carolina State University, is looking at the conditions necessary to the formation of those two elements in the universe. They’ve found that when it comes to supporting life, the universe leaves very little margin for error.
Both carbon and oxygen are produced when helium burns inside of giant red stars. Carbon-12, an essential element we’re all made of, can only form when three alpha particles, or helium-4 nuclei, combine in a very specific way. The key to formation is an excited state of carbon-12 known as the Hoyle state, and it has a very specific energy – measured at 379 keV (or 379,000 electron volts) above the energy of three alpha particles. Oxygen is produced by the combination of another alpha particle and carbon.
NC State physicist Dean Lee and German colleagues Evgeny Epelbaum, Hermann Krebs, Timo Laehde and Ulf-G. Meissner had previously confirmed the existence and structure of the Hoyle state with a numerical lattice that allowed the researchers to simulate how protons and neutrons interact. These protons and neutrons are made up of elementary particles called quarks. The light quark mass is one of the fundamental parameters of nature, and this mass affects particles’ energies.
In new lattice calculations done at the Juelich Supercomputer Centre the physicists found that just a slight variation in the light quark mass will change the energy of the Hoyle state, and this in turn would affect the production of carbon and oxygen in such a way that life as we know it wouldn’t exist.
“The Hoyle state of carbon is key,” Lee says. “If the Hoyle state energy was at 479 keV or more above the three alpha particles, then the amount of carbon produced would be too low for carbon-based life.
“The same holds true for oxygen,” he adds. “If the Hoyle state energy were instead within 279 keV of the three alphas, then there would be plenty of carbon. But the stars would burn their helium into carbon much earlier in their life cycle. As a consequence, the stars would not be hot enough to produce sufficient oxygen for life. In our lattice simulations, we find that more than a 2 or 3 percent change in the light quark mass would lead to problems with the abundance of either carbon or oxygen in the universe.”
The researchers’ findings appear in Physical Review Letters.
Hidden in a tiny tile of interwoven DNA is a message. The message is simple, but decoding it unlocks the secret of dynamic nanoscale assembly. Researchers at the University of Illinois at Urbana-Champaign have devised a dynamic and reversible way to assemble nanoscale structures and used it to encrypt a Morse code message. Led by Yi Lu, the Schenck Professor of Chemistry, the team published its development in the Journal of the American Chemical Society.
Scientists and engineers who work with nanoscale materials use an important technique called programmable assembly to strategically combine simple building blocks into larger functional components or structures. Such assembly is important for applications in electronics, photonics, medicine and much more.
Most standard nano-assembly techniques yield a particular, static product. But looking at biology, Lu saw a lot of dynamic assemblies: reversible building processes, or substitutions that could be made after assembly to add or change function. Such versatility could enable many more applications for nanoscale materials, so Lu’s group set out to explore nanoscale systems that could reliably and reversibly assemble.
“I think a critical challenge facing nanoscale science and engineering is reversible assembly,” Lu said. “Researchers are now pretty good at putting components in places they desire, but not very good at putting something on and taking it off again. Many applications need dynamic assembly. You don’t just want to assemble it once, you want to do it repeatedly, and not only using the same component, but also new components.”
The group took advantage of a chemical system common in biology. The protein streptavidin binds very strongly to the small organic molecule biotin – it grabs on and doesn’t let go. A small chemical tweak to biotin yields a molecule that also binds to streptavidin, but holds it loosely.
The researchers started with a template of DNA origami – multiple strands of DNA woven into a tile. They “wrote” their message in the DNA template by attaching biotin-bound DNA strands to specific locations on the tiles that would light up as dots or dashes. Meanwhile, DNA bound to the biotin derivative filled the other positions on the DNA template.
Then they bathed the tiles in a streptavidin solution. The streptavidin bonded to both the biotin and its derivative, making all the spots “light up” under an atomic force microscope and camouflaging the message. To reveal the hidden message, the researchers then put the tiles in a solution of free biotin. Since it binds to streptavidin so much more strongly, the biotin effectively removed the protein from the biotin derivative, so that only the DNA strands attached to the unaltered biotin kept hold of their streptavidin. The Morse code message, “NANO,” was clearly readable under the microscope.
The researchers also demonstrated non-Morse characters, creating tiles that could switch back and forth between a capital “I” and a lowercase “i” as streptavidin and biotin were alternately added. (See an animation of the process.)
“This is an important step forward for nanoscale assembly,” Lu said. “Now we can encode messages in much smaller scale, which is interesting. There’s more information per square inch. But the more important advance is that now that we can carry out reversible assembly, we can explore much more versatile, much more dynamic applications.”
Next, the researchers plan to use their technique to create other functional systems. Lu envisions assembling systems to perform a task in chemistry, biology, sensing, photonics or other area, then replacing a component to give the system an additional function. Since the key to reversibility is in the different binding strengths, the technique is not limited to the biotin-streptavidin system and could work for a variety of molecules and materials.
“As long as the molecules used in the assembly have two different affinities, we can apply this particular concept into other templates or processes,” Lu said. Video of the new technique can be watched here.
One of the discovery images of the system obtained at the Keck II telescope using the adaptive optics system and NIRC2 Near-Infrared Imager. The rectangle indicates the field-of-view of the OSIRIS instrument for planet C. Credit: Image courtesy of NRC-HIA, C. Marois and Keck Observatory.
The most detailed look yet at the atmosphere of a distant exoplanet has revealed a mixture of water vapor and carbon monoxide blanketing a world ten times the size of Jupiter about 130 light years away from Earth. But even with water present on this world, it is incredibly hostile to life. Like Jupiter, it has no solid surface, and it has a temperature of more than a thousand degree. Additionally, no tell-tale methane signals were detected in the atmosphere. But this solar system is still of great interest, as three other giant worlds orbit the same star and scientists said studying this system will not only help solve mysteries of how it was formed, but also how our own solar system formed as well.The observations were made at the Keck II telescope in Hawaii, using an infrared imaging spectrograph called OSIRIS, which was able to uncover the chemical fingerprints of specific molecules.
“This is the sharpest spectrum ever obtained of an extrasolar planet,” said Dr. Bruce Macintosh, from the Lawrence Livermore National Laboratory. “This shows the power of directly imaging a planetary system. It is the exquisite resolution afforded by these new observations that has allowed us to really begin to probe planet formation.”
“With this level of detail,” said co-author Travis Barman from the Lowell Observatory, “we can compare the amount of carbon to the amount of oxygen present in the atmosphere, and this chemical mix provides clues as to how the planetary system formed.”
Artist’s rendering of HR 8799c at an early stage in the evolution of the planetary system, showing the planet, a disk of gas and dust, rocky inner planets, and HR 8799. Credit: Dunlap Institute for Astronomy & Astrophysics
The planets around the star, known as HR 8799, weigh in between five to 10 times the mass of Jupiter and are still glowing in infrared with the heat of their formation. The research team says their observations suggest the solar system was created in a similar way to our own, with gas giants forming far away from their parent star and smaller, rocky planets closer in. However, no Earth-like rocky planets have yet been detected in this system.
“The results suggest the HR 8799 system is like a scaled-up Solar System,” said Quinn Kanopacky, an astronomer from the University of Toronto in Canada. “Once the solid cores grew large enough, their gravity quickly attracted surrounding gas to become the massive planets we see today. Since that gas had lost some of its oxygen, the planet ends up with less oxygen and less water than if it had formed through a gravitational instability.”
There are two leading models of planetary formation: core accretion and gravitational instability. When stars form, a planet-forming disk surrounds them. With core accretion, planets form gradually as solid cores slowly grow big enough to start acquiring gas from the disk, while in the gravitational instability model, planets form almost instantly as the disk collapses on itself.
Properties such as the composition of a planet’s atmosphere are clues to how the planet formed, and in this case core accretion seems to win out. Although there was evidence of water vapor, that signature is weaker than would be expected if the planet shared the composition of its parent star. Instead, the planet has a high ratio of carbon to oxygen – a fingerprint of its formation in the gaseous disk tens of millions of years ago. As the gas cooled with time, grains of water ice formed, depleting the remaining gas of oxygen. Planetary formation then began when ice and solids collected into planetary cores.
“Once the solid cores grew large enough, their gravity quickly attracted surrounding gas to become the massive planets we see today,” said Konopacky. “Since that gas had lost some of its oxygen, the planet ends up with less oxygen and less water than if it had formed through a gravitational instability.”
“Spectral information of this quality not only provides clues about the formation of the HR8799 planets but also provides the guidance we need to improve our theoretical understanding of exoplanet atmospheres and their early evolution,” said Barman. “The timing of this work could not be better as it comes on the heels of new instruments that will image dozens more exoplanets, orbiting other stars, that we can study in similar detail.”
This system was also the study as part of remote reconnaissance imaging with Project 1640. The video below explains more:
Rock dust drilled from sediments in the giant Gale crater on the red planet were found to contain clay minerals that can have formed only in water, scientists said.
The discovery of other substances alongside the clays, such as calcium phosphate, suggest the soil was neutral or mildly alkaline, making the environment suitable for microbes.
Instruments aboard the Curiosity rover have allowed scientists to build up a gradual picture of the planet’s geological past, but the latest analyses are the strongest evidence yet that Mars was once hospitable to life.
“A fundamental question for this mission is whether Mars could have supported a habitable environment,” Michael Meyer, a lead scientist…
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NASA’s Wide-field Infrared Survey Explorer (WISE) has discovered a pair of stars that has taken over the title for the third-closest star system to the sun. The duo is the closest star system discovered since 1916.
Both stars in the new binary system are “brown dwarfs,” which are stars that are too small in mass to ever become hot enough to ignite hydrogen fusion. As a result, they are very cool and dim, resembling a giant planet like Jupiter more than a bright star like the sun.
“The distance to this brown dwarf pair is 6.5 light-years — so close that Earth’s television transmissions from 2006 are now arriving there,” said Kevin Luhman, an associate professor of astronomy and astrophysics at Penn State University, University Park, Pa., and a researcher in Penn State’s Center for Exoplanets and Habitable Worlds.
“It will be an excellent hunting ground for planets because the system is very close to Earth, which makes it a lot easier to see any planets orbiting either of the brown dwarfs.”
The results will be published in the Astrophysical Journal Letters.
The star system is named “WISE J104915.57-531906″ because it was discovered in an infrared map of the entire sky obtained by WISE. It is only slightly farther away than the second-closest star, Barnard’s star, which was discovered 6 light-years from the sun in 1916. The closest star system consists of: Alpha Centauri, found to be a neighbor of the sun in 1839 at 4.4 light-years away, and the fainter Proxima Centauri, discovered in 1917 at 4.2 light-years.
Edward (Ned) Wright, the principal investigator for the WISE satellite at UCLA, said, “One major goal when proposing WISE was to find the closest stars to the sun. WISE J1049-5319 is by far the closest star found to date using the WISE data, and the close-up views of this binary system we can get with big telescopes like Gemini and the future James Webb Space Telescope will tell us a lot about the low-mass stars known as brown dwarfs.”
The Gemini South telescope in Chile was also used in this study for follow-up observations.
WISE completed its all-sky survey in 2011, after surveying the entire sky twice at infrared wavelengths. The maps have been released to the public, but an ongoing project called “AllWISE” will combine data from both sky scans. AllWISE will provide a systematic search across the sky for the nearby moving stars such as WISE J104915.57-531906, and also uncover fainter objects from the distant universe. Those data will be publicly available in late 2013.