A mysterious wave discovered in the Milky Way suggests our galaxy is still ringing like a bell from a galactic collision, a crash that possibly occurred within the last 100 million years, scientists say.

Astronomers discovered that stars north and south of the midplane of the galaxy are distributed differently, suggesting that some recent event perturbed them. The most likely explanation is that a small satellite galaxy or clump of invisible dark matter plowed through the Milky Way, leaving behind the echoes that we see.

"Our part of the Milky Way is ringing like a bell," Brian Yanny, of the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Ill., said in a statement. "But we have not been able to identify the celestial object that passed through the Milky Way. It could have been one of the small satellite galaxies that move around the center of our galaxy, or an invisible structure such as a dark matter halo."

The wave was discovered in data from the Sloan Digital Sky Survey, which has observed roughly 300,000 nearby Milky Way stars.

© A. Justo and D. Floudas
White rot fungi, like the "turkey tails" mushroom pictured here, can break down lignin--the molecule that helps make wood rigid and resist decay.

The evolution of the ability to break down a plant's protective lignin largely stopped the geologic burial of carbon that formed present-day coal deposits - and may provide secrets to making biofuels from inedible parts of plants.

A toughened crosshatch of carbon-based molecules is all that stands between plants and their total destruction at the hands of an array of microbes and fungi. Called lignin, the compound enables redwoods to tower and woody herbs to resist rot. As a result, lignin is the second-most abundant biological compound on the planet - and the bane of would-be biofuel-makers everywhere, blocking their best efforts to make fuels from the inedible parts of plants. It is also the reason for the vast deposits of coal laid down millions of years ago.

Now a new genomic analysis suggests why Earth significantly slowed its coal-making processes roughly 300 million years ago - mushrooms evolved the ability to break down lignin.

"These white rot fungi are major decomposers of wood and the only organism that achieves substantial degradation of lignin," explains mycologist David Hibbett of Clark University in Massachusetts, who led the research published in Science on June 29.

By comparing 12 newly sequenced genomes of mushroom fungi with 19 existing genomes, the researchers determined that an ancestral white rot fungi (Agaricomycetes) first evolved the ability to break down lignin. The scientists then used so-called "molecular clock analysis" - a dating technique based on the hypothesis that genes accumulate mutations at a relatively regular rate like trees form rings that record their growth. Such an analysis suggests that an ancestral white rot fungi developed this lignin-degrading ability roughly 290 million years ago, a conclusion backed by comparison with the appearance in the fossil record of three other types of fungi (although the first definitive white rot fossil does not appear until roughly 260 million years ago) and the subsequent expansion and refinement of the arsenal of enzymes employed. The 60-million-year-long Carboniferous period - when the bulk of the world's coal deposits were laid down and atmospheric CO2 levels declined - ended roughly 300 million years ago.

Astronomers working with the United Kingdom Infrared Telescope on Hawaii have discovered four pairs of stars that orbit each other in less than 4 hours.

Until now it was thought that such close-in binary stars could not exist.

About half of the stars in our Milky Way galaxy are, unlike our Sun, part of a binary system in which two stars orbit each other. Most likely, the stars in these systems were formed close together and have been in orbit around each other from birth onwards. It was always thought that if binary stars form too close to each other, they would quickly merge into one single, bigger star. This was in line with many observations taken over the last three decades showing the abundant population of stellar binaries, but none with orbital periods shorter than 5 hours.

For the first time, the team has investigated binaries of red dwarfs, stars up to ten times smaller and a thousand times less luminous than the Sun. Although they form the most common type of star in the Milky Way, red dwarfs do not show up in normal surveys because of their dimness in visible light.

For days, giant sunspot AR1515 has looked capable of producing a really strong explosion. On July 6th it finally did. Yesterday, the sunspot's magnetic canopy erupted, producing a brief but potent X1.1-class solar flare. NASA's Solar Dynamics Observatory recorded the extreme ultraviolet flash.

The explosion hurled a CME into space. According to this movie from the Solar and Heliospheric Observatory, the cloud appears to be heading south and away from Earth. However, we cannot yet rule out a glancing blow to our planet on July 8th or 9th. Stay tuned for further analysis.

Video

Observations of a 'single' electron apparently splitting into two independent entities -- so-called quasi-particles -- are reported in this week's Nature.

An electron has been observed to decay into two separate parts, each carrying a particular property of the electron: a spinon carrying its spin - the property making the electron behave as a tiny compass needle - and an orbiton carrying its orbital moment - which arises from the electron's motion around the nucleus. These newly created particles, however, cannot leave the material in which they have been produced. This result is reported in a paper published in Nature by an international team of researchers led by experimental physicists from the Paul Scherrer Institute (Switzerland) and theoretical physicists from the IFW Dresden (Germany).

All electrons have a property called "spin", which can be viewed as the presence of tiny magnets at the atomic scale and which thereby gives rise to the magnetism of materials. In addition to this, electrons orbit around the atomic nuclei along certain paths, the so-called electronic "orbitals". Usually, both of these quantum physical properties (spin and orbital) are attached to each particular electron. In an experiment performed at the Paul Scherrer Institute, these properties have now been separated.

Stick a shovel in the ground and scoop. That's about how deep scientists need to go in order to find evidence for ancient life on Mars, if there is any to be found, a new study suggests. That's within reach of Curiosity, the Mars Science Laboratory rover expected to land on the Red Planet next month.

The new findings, which suggest optimal depths and locations to probe for organic molecules like those that compose living organisms as we know them, could help the newest Mars rover scout for evidence of life beneath the surface and within rocks. The results suggest that, should Mars harbor simple organic molecules, NASA's prospects for discovering them during Curiosity's explorations are better than previously thought, said Alexander Pavlov of the NASA Goddard Space Flight Center in Greenbelt, Maryland, lead author of the study.

While these simple molecules could provide evidence of ancient Martian life, they could also stem from other sources like meteorites and volcanoes. Complex organic molecules could hint more strongly at the possibility of past life on the planet. These molecules, made up of 10 or more carbon atoms, could resemble known building blocks of life such as the amino acids that make up proteins.

Researchers in the US have come up with a solution to the problem of headlight glare reducing driver visibility in the rain. It is a problem with which anyone driving on UK roads in the last three months will be more than familiar. Scientists at Carnegie Mellon University have developed a smart headlight that can shine "around" rain.

The idea is that the headlight will be able to predict where rain falls and adjust light beams accordingly.

Prototype success

Using low-cost, off-the-shelf components the researchers set about developing a system that switches off rays of light that hit raindrops. The smart headlight consists of a projector, camera and beam-splitter.

The camera takes images of the raindrops, a processor uses a predictive algorithm to work out where rain will fall, and then the projector switches off light rays that would have normally hit the raindrops.

Neuropathologists at the University of Zurich have solved the puzzle surrounding the origins of follicular dendritic cells -- cells of lymphoid organs that play an important role in many autoimmune and infectious diseases. The UZH research team has demonstrated that follicular dendritic cells originate in cells located in the walls of blood vessels. Thanks to these findings, scientists now have the means to investigate key features of the development of autoimmune diseases, chronic inflammation, tumors, and prion infections.

Chronic inflammatory conditions are extremely common diseases in humans and in the entire animal kingdom. Both in autoimmune diseases and pathogen-caused diseases, the inflamed areas are rapidly colonized by antibody producing B lymphocytes -- which organize themselves in highly structured areas called "lymphoid follicles." The scaffold of such follicles is provided by follicular dendritic cells (FDCs). FDCs have important roles in the development of immune responses, since they trap antigens for protracted periods of, thereby training B lymphocytes to recognize the invaders. However, FDCs can also play deleterious roles in disease, because they can provide sanctuaries for infectious pathogens such as the human immunodeficiency virus and prions.

A traffic officer standing at a busy intersection directing the flow of vehicles may be a rare sight these days, but a similar scene appears to still frequently play out in our cells. A protein called Lem4 directs a crucial step of cell division by preventing the progress of one molecule while waving another through, scientists at the European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany, have found.

The study is published online July 6 in Cell.

For an embryo to grow or a tissue to regenerate, its cells must divide. When one of our cells divides to give rise to two, the membrane that surrounds the cell's nucleus -- the nuclear envelope -- has to be broken down and later rebuilt, once the chromosomes have been dragged apart. For this re-assembly to take place, a protein called BAF has to have chemical tags called phosphates removed. Changing a protein's phosphorylation state -- its possession or lack of phosphate tags -- can involve regulating the activity of proteins that add phosphate, proteins that remove phosphate, or both. The EMBL scientists discovered a new molecule, Lem4, which acts as a traffic officer, stopping one protein from adding phosphate tags to BAF and bringing in another protein to remove the existing tags.

A lack of cash could end the only survey dedicated to searching the southern skies for Earth-grazing comets and asteroids. That would create a blind spot in our global view of objects that could cause significant devastation should they hit Earth.

The Siding Spring Survey uses images from the Siding Spring observatory in Australia as part of the global Catalina Sky Survey, an effort to discover and track potentially dangerous near-Earth objects. Astronomers sift through virtually identical images of the sky, looking for moving objects.

Catalina uses a range of northern hemisphere telescopes - and the Sliding Spring Survey. But in October, Catalina cut off cash to the survey due to growing costs, caused partly by changes in the exchange rate between the Australian and US dollars. That decision was "very difficult", says Steve Larson, who heads Catalina.

Since then, the southern survey has been limping along with temporary funding from the Australian National University in Canberra, but the extension is set to expire at the end of July, says survey operator Rob McNaught.

The leftover building blocks of planets, near-Earth objects orbit the sun in highly elliptical orbits, and sometimes graze or hit Earth. Seeing an asteroid before it hits could save lives by providing time to evacuate a region. "Given the very best circumstances, you can predict an impact to 1 second and 1 kilometre," says McNaught. "There's no other natural disaster that you can do that for."