‘Great American Eclipse’ offers opportunity for millions

‘Great American Eclipse’ offers opportunity for millions:

On Aug. 21, 2017, the entire continental U.S. will see a solar eclipse. Only a 70-mile wide stripe across the central part of the country will experience totality. Image Credit: NASA

It’s not often an entire country has the opportunity to be an active part of something historic, but on Monday, August 21, 2017, anyone in the United States, most of Canada, some parts of Mexico, and some countries in the Caribbean will be able to do just that. This will mark the first time in nearly a century that a total solar eclipse will pass across the entirety of the U.S. from the Pacific to the Atlantic, and the next time this will happen won’t be until 2045.

Eclipses have been a part of the history of every culture since the beginning of humanity. Ancient societies as far back as 1375 B.C. have recorded total solar eclipses. Most believed that eclipses, both solar and lunar, were portents of events to come. The majority saw eclipses as fearful events – things that went against the laws of nature and their gods.

A total solar eclipse. Photo Credit: NASA

The alignment of celestial bodies is an astronomical event called syzygy. This can create an eclipse, occultation, or transit. As much as the average citizen looks forward to the wonder and beauty of an eclipse, scientists around the world use syzygy to do some remarkable science.

Some of the most pivotal discoveries in modern memory have been due to syzygy. These include Sir Arthur Eddington’s proof of Einstein’s Theory of Relativity by the observation of the Sun’s gravity bending the spacetime around it to reveal the light of a star hidden behind the Sun during an eclipse, and the discovery of thousands of extra-solar planets (exoplanets) by the Kepler Space Telescope using the transit method or even by ground-based telescopes using microlensing.

For instance, the scientists behind the New Horizons mission that visited Pluto in 2015 have recently used stellar occultation to gather more information on the small Kuiper belt object known as 2014 MU₆₉ prior to the spacecraft’s flyby of it coming up in January 2019.

Astronomers and other scientists use these events to gather information that can’t be gathered in any other way. Total solar eclipses provide an opportunity to view a part of the Sun we cannot properly see any other way – the corona.

The corona is the outermost layer of the Sun and is equivalent to its atmosphere. It is one of the most mysterious aspects of our closest star. NASA recently renamed Parker Solar Probe will be launched next year to study this mysterious part of the Sun.

Unlike every other place we are aware of, the farther you get from the center of a planet or other celestial body, the cooler the temperatures get. That’s not how it is with the corona of the Sun. In fact, the corona of the Sun is millions of degrees hotter than the surface of the Sun.

Capturing the moment

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For many astrophotographers, capturing a total solar eclipse is one of their bucket list items. It’s not a simple photograph to be able to capture for myriad reasons, the smallest of which is trying to be in the right place at just the right time. Even if you find the right spot along the line of totality, there’s no guarantee the weather will cooperate. Additionally, totality will only last for a maximum of 2 minutes, 40 seconds, depending on where you are. Click here for a list of totality times.

As many eclipse chasers can attest, you can spend large sums of money traveling to remote locales only to find that clouds block the view. Because the surface of the Earth is covered primarily in oceans, the likelihood of an eclipse happening on inhabited land is pretty low, which is what makes the August 21 eclipse a truly special event.

The path of totality for the Aug. 21, 2017, total solar eclipse. Image Credit: NASA

This eclipse has been billed by some as the “Great American Eclipse” since the entire path of totality occurs only touches land within the borders of the United States and has the potential to be the most-viewed eclipse ever.

Massive numbers of people from all over the planet are making the trek to locations along the path of totality in order to see this celestial event. Most of the areas where the eclipse will be viewable in totality happen to be relatively small towns and rural areas, some of which are expecting massive influxes of people.

Madras, Oregon, for example, normally has a population of approximately 6,000 people. That is expected to swell to over 100,000 for the days before and on the day of the eclipse. This poses a list of potential infrastructure problems including gas shortages, nightmare-level traffic jams, and price gouging on anything and everything.

Even so, people seem happy and excited to have even a chance to see the eclipse. Liam Kennedy, owner and inventor of ISS-Above, drove two days from Southern California to central Oregon to view the eclipse and is looking forward to “being enveloped in the Moon’s shadow”.

“I mean, literally, there will be a shadow on me from the Moon,” Kennedy said. “There will be a direct connection between me, and the Moon and the Sun! I mean, wow!”

This excitement and interest span a wide range of ages and genders. From school-age children to long-retired people who have never had the opportunity to see an eclipse before, the fevered interest is palpable.

Astrophotography hobbyist and amateur astronomer Chris Hetlage plans to stay mobile and try to outsmart Mother Nature. Hetlage, who began taking photographs in the late 1980s, has out run weather in order to get stunning images of lunar eclipses and even the transit of Venus. After capturing an annular eclipse in Chico, California, in 2012, he knew he wanted to photograph a total eclipse.

Hetlage plans to be well armed with a plethora of equipment in order to maximize the possibility of imaging the eclipse somewhere between Saint Louis and Kansas City in Missouri, and he will go as far as Nebraska or Montana depending on how the weather looks leading up to the eclipse.

The crew of the International Space Station witnessed the shadow of the Moon racing across Earth during the March 29, 2006, total solar eclipse. Photo Credit: NASA

Citizen science opportunities

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Once the eclipse starts, if you’re not in the path, it’s virtually impossible to chase it. The shadow of the Moon moves at speeds upward of 2,288 mph (3,683 km/h), which is greater than the speed of sound. People have stood on mountain tops and watched the Moon’s shadow race across hundreds of miles to find them in just a matter of minutes.

For those who aren’t familiar with the affects of a solar eclipse, the changes in temperature, development of clouds, shifts in winds, and even animal activity can be startling. For those who aren’t in the path of totality, there can still be significant impacts.

NASA sponsors an application called the Globe Observer that they hope will appeal to citizen scientists. The application gathers data about weather, temperature, with other projects about animal behavior, coronal imaging, and ionosphere activity from across a wide range of areas where both totality and partial eclipse will be able to be seen. The data is then correlated by scientists in an attempt to better understand the impacts of the Sun on the weather here on Earth.

Those interested in conducting eclipse related citizen science can download the Globe Observer application as well as the many other ways to personally participate in citizen science projects.

For those who aren’t among the millions of people expected to be within the path of totality, or are but the weather in your area isn’t cooperating, NASA TV will be live-streaming the event from special high-elevation balloons, ground-based telescopes using various types of light and polarization filters, and even from specially outfitted jets.

Partial eclipse viewing safety

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Even if one isn’t in the path of totality but will be within the continental U.S., the whole continent will still be able to see a partial solar eclipse. The most crucial aspect to viewing this phase is taking precautions for viewing safety.

Just like when the skin gets a sunburn, it’s not an immediate discomfort. When the inside of the eye receives a sunburn from exposure to the damaging rays of the Sun, it’s especially problematic because the inside of the eye doesn’t possess pain receptors. This means that the damage can go unnoticed until the delicate tissues of the retina become swollen and inflamed reducing vision. This can reverse over time, but in some cases vision can be permanently lost.

Only view the eclipse with approved eclipse safety glasses or viewers, or, better yet, make a pinhole projector to indirectly observe the eclipse. Indirect observation guarantees you won’t damage your vision. Pinhole projectors are easy to create and very inexpensive, taking from five to 10 minutes for the pinhole projector.

If you’re unable to make it to the path of totality or are unable to fully appreciate it from your location, you can start planning now for the next total solar eclipse that will be in the United States on April 8, 2024.

Video courtesy of NASA

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Saturn Moon Tethys Shines Above Rings in Gorgeous Photo

Saturn Moon Tethys Shines Above Rings in Gorgeous Photo:

The icy moon Tethys sits above Saturn's rings in this photo captured on May 13, 2017, by NASA's Cassini spacecraft.

Credit: NASA/JPL-Caltech/Space Science Institute

Saturn's icy moon Tethys hovers above the planet's iconic rings in a breathtaking photo by NASA's Cassini spacecraft.

Though NASA released the image Monday (Aug. 21), Cassini actually captured it on May 13, 2017. At the time, the probe was about 750,000 miles (1.2 million kilometers) from Saturn and 930,000 miles (1.5 million km) from Tethys, agency officials said.

The night side of Tethys is lit up by "Saturnshine" — sunlight reflected off its parent planet — in the image. But this Saturnshine isn't quite as powerful as the photo makes it seem.

"Tethys was brightened by a factor of two in this image to increase its visibility," NASA officials wrote in an image description. "A sliver of the moon's sunlit northern hemisphere is seen at top. A bright wedge of Saturn's sunlit side is seen at lower left."

At 660 miles (1,062 km) across, Tethys is the fifth-largest moon of Saturn. (The only bigger ones are Titan, Rhea, Iapetus and Dione.) Tethys has some pretty dramatic features that aren't visible in this photo — a deep canyon that snakes across three-fourths of its surface, for example, and a crater called Odysseus that's 250 miles (400 km) wide.

Cassini has been capturing stunning images like this one since arriving in orbit around Saturn in July 2004. But the probe's work is nearly done: Cassini is in the "Grand Finale" phase of its mission, which will culminate with an intentional death dive into Saturn's thick atmosphere on Sept. 15.

This maneuver is designed to ensure that Cassini doesn't contaminate Titan or fellow Saturn satellite Enceladus with microbes from Earth. (Astrobiologists think Titan and Enceladus may be capable of supporting life.)

The $3.2 billion Cassini-Huygens mission is a collaboration involving NASA, the European Space Agency and the Italian Space Agency. Huygens was a piggyback lander that traveled with the Cassini mothership and touched down on Titan in January 2005.

Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.

Proposed Orbiter Could Probe the Ocean Beneath Saturn's Moon Titan

Proposed Orbiter Could Probe the Ocean Beneath Saturn's Moon Titan:

An icy shell separates Titan's organic-rich surface from its liquid ocean. If organic material manages to penetrate that shell and travel to the water beneath, it could provide the necessary ingredients for the evolution of life as we know it.

Credit: A. D. Fortes/UCL/STFC

When NASA's Cassini mission arrived at Saturn, it pressed through the haze surrounding the ringed planet's largest moon, Titan, to reveal a complex, liquid-covered world with the potential to support life. Now, researchers are proposing a return to Titan with a mission that would investigate not only the flowing methane and ethane on its surface, but also the ocean beneath.

"It's really important that we go back to Titan," Michael Malaska told fellow scientists at the Astrobiology Science Conference in Mesa, Arizona, in April. Malaska, a researcher at the Jet Propulsion Laboratory, is part of the team proposing Oceanus, a mission with the goal of studying the moon's habitability.

"It's a really fantastic world totally rich with organic chemistry," Malaska said. "It looks like it might be an interesting place for life in the same vein as Europa and Enceladus." [Icy Water Moons That Might Host Life (Infographic)]

An ocean world

In April, Oceanus was submitted as part of NASA's New Frontiers mission competition. The New Frontiers program seeks to explore the solar system with frequent, medium-class spacecraft missions engaged in focused investigations. In addition to the ocean worlds Titan and Enceladus, the current round of proposed investigations features goals that include sample return from the moon or from comets, a study of Saturn or Venus, or a rendezvous with the Trojan asteroids of the outer solar system. By studying the organic material and landscape features, as well as capturing more detailed images, Oceanus would investigate the organic and methane cycle on Titan and probe what's going on beneath the surface.

Titan boasts an intriguing surface, with organic-rich hazes and flowing liquids. With its liquid presence fueled by energy from the sun, the planet bears a strong resemblance to Earth. Instead of water, however, Titan's atmosphere and surface are dominated by methane and ethane. The presence of these hydrocarbons in the upper atmosphere forms what Malaska called "a complex organic chemical factory," while it is the only solar system other than Earth to contain flowing lakes and rivers.

Some scientists have suggested that life, which may have followed a completely different path than it took on Earth, could evolve on Titan.

The three necessary ingredients for life as we know it include organic material, a source of energy and water. Titan's exterior holds the first two: Energy streaming in from the sun may be captured in the form of high-energy molecules. "You can almost think of it as manna from heaven," Malaska said.

While the surface doesn't contain liquid water, that doesn't mean it isn't present on the moon.

"Remember that Titan is an ocean world," Malaska said — there's a potential large ocean of liquid water beneath the surface.

When paired with the rich organic surface, that ocean could provide a home for life as intriguing as the two most well-known ocean moons, Saturn's satellite Enceladus and Jupiter's moon Europa. All three have an icy layer shielding their ocean, though Titan's lies beneath its rich organic surface.

But while Europa and Enceladus must rely on interactions with the rock to build a habitable environment where life could evolve, Malaska said that Titan's ocean could get a little help from the surface, which is also a potential home for life. Previous experiments revealed that exposing simulated Titan organics to water generates some of the molecules necessary for life as we know it, such as amino acids and nucleobases.

Oceanus would make in-depth investigations of surface features identified by Cassini, such as suspected ice volcanoes, impact sites and other signs of tectonic processes. The spacecraft would also examine the ice shell to determine if it is convecting, with warm material rising and colder material sinking. Convection could help to carry surface material through the ice and into the ocean, as well as bring water to the surface.

It's even possible that the surface could be interacting with the very core of the planet. "That's one of the things we want to find out — Is there contact with the core, or is there so much ice that [the ocean] is actually sealed off," Malaska said. [Watch Methane Clouds Swirl in Saturn Moon Titan's Skies (Video)]

Credit: Karl Tate, SPACE.com contributor


If the mission were chosen, Oceanus would spend two years orbiting Saturn, making flybys of Titan, Malaska said. Then it would settle into a two-year orbit around that moon.

The spacecraft would carry three instruments to help study the surface and subsurface. A mass spectrometer would analyze the chemistry of the heaviest molecules in the atmosphere to understand how they interact, Malaska said. An infrared camera would follow how the organic material moved across the surface, and potentially how it interacted with water near the surface. And a radar altimeter would examine tectonic activity.

Together, the instruments would not only provide a glimpse of the surface, but also how material might cycle through the crust through geological processes, providing "the building blocks for life to a water-rich environment," the team said in its abstract.

'Follow the organics'

Before Cassini caught a glimpse in 2004, Titan remained shielded behind a haze of organic material. The spacecraft revealed an intriguing surface, with seas of methane and ethane; rivers; and deltas and dunes (not to mention 'magic islands' that appear and disappear).

"Cassini revealed an absolutely beautiful landscape that is alien and bizarre, but also Earth-like," Malaska said.

But although Cassini revealed insights about the moon's features, its images could only resolve the largest, kilometer-size features. Oceanus would take advantage of orbiting Titan to capture far more detailed images, down to 82 feet (25 meters) per pixel.

A study of Titan could provide insights about the early Earth. According to Malaska, the methane-rich moon may be an analogue of our own planet, before the rise of oxygen.

"Effectively by going to Titan today, we could be going back in a time machine to early Earth," he said.

But while Earth is all about the water, Titan is all about the hydrocarbons. That's the trail Malaska and his colleagues hope to pursue with Oceanus.

"We're going to study the molecules from their source," Malaska said. "So we're effectively going to follow the organics."

Follow Nola Taylor Redd at @NolaTRedd, Facebook, or Google+. Follow us at @Spacedotcom, Facebook or Google+. Originally published on Space.com.

'Golden Record 2.0': New Horizons Probe Could Carry Digital-Age Message for Aliens

'Golden Record 2.0': New Horizons Probe Could Carry Digital-Age Message for Aliens:

The cover of the Golden Record, copies of which launched aboard NASA's Voyager 1 and Voyager 2 probes in 1977.

Credit: NASA

NASA's New Horizons spacecraft could end up bearing a message for intelligent aliens, just as the agency's venerable Voyager probes are doing.

Both Voyager 1 and Voyager 2 famously carry copies of the "Golden Record," which are loaded with photos, music, sounds and other data designed to teach any extraterrestrials who might encounter the probes about humanity and its home planet.

Though such an alien encounter isn't likely, it is possible; Voyager 1 popped into interstellar space in August 2012, and its twin will probably do the same in the next few years, mission team members have said. [The Golden Record in Pictures: Voyager Probes' Message to Space Explained]

New Horizons' ultimate fate also lies beyond the solar system, "and it's leaving without a Golden Record, without a message," said Jon Lomberg, the design director for the Voyagers' Golden Record. (He worked closely with astronomer and science communicator Carl Sagan, who chaired the committee that decided what information the record would contain.) "That seems like a missed opportunity," he said.

Lomberg wants to change things, by giving New Horizons a "Golden Record 2.0" — a new, crowdsourced digital version called the One Earth Message, which would be beamed out to the spacecraft in 2020.

On Aug. 20 — the 40th anniversary of Voyager 2's liftoff — he and his team launched a 40-day Kickstarter campaign, which seeks $72,000 to develop and maintain a website that will manage the photos and other material people submit for possible inclusion in the One Earth Message. If all goes according to plan, online voting will determine which content will ultimately make up the message.

Jon Lomberg's original sketch for the cover diagram of the Voyager mission's famous "Golden Record." This drawing and other golden-record archival material will go up for auction on Sept. 14, 2017.

Credit: Jon Lomberg/Heritage Auctions


The group is also seeking funding via other means. For example, Lomberg is auctioning off his collection of Voyager Golden-Record archival material, which includes (among other things) his original sketch for the cover diagram, numerous other drawings, and letters about the project from sci-fi legend Robert Heinlein and other notable people.

Heritage Auctions will manage the sale, which will take place Sept. 14. The collection is expected to fetch about $10,000, Heritage representatives told Space.com.

As such fundraising efforts suggest, NASA is not sponsoring or bankrolling the One Earth Message. However, agency officials and New Horizons team members have unofficially signaled support for the project, Lomberg said.

New Horizons, which flew past Pluto in July 2015, is now zooming toward a Jan. 1, 2019, rendezvous with a small object called 2014 MU69. It may take a year or so for the probe to beam all of its data from this second flyby home to Earth, Lomberg said; only then will New Horizons be able to spare the computer memory necessary to accommodate the One Earth Message.

"That gives us a good two years to first put the message together, which I estimate will take at least a year, and then another year to put it all together in software, test it and make sure it's suitable for upload," Lomberg said.

The upload to New Horizons would not happen without official NASA approval. This approval might be easier to obtain if the team approaches the agency with a finished product rather than a nebulous concept, Lomberg said.

"Forty years ago, when I worked with Carl on the Golden Record, he didn't go to NASA and try to get them to approve some vague idea of the message's music and sounds," Lomberg said. "He made it, and then he showed it to them and said what we did. They reacted to it. And if there was something they didn't like — and there was one picture they didn't like — they took it out."

Lomberg's vision for the One Earth Message doesn't end with New Horizons. Eventually, he would like every probe that leaves Earth to carry the message, or something like it.

"I think our spacecraft are our finest technical masterpieces," he said. "They're essentially works of art, and every work of art should be signed."

"Signing" probes in this fashion is worth the effort, even if they drift alone through space for eternity, Lomberg added.

"We will never know if there is an E.T. audience, but for the human audience that participates, it can be a profoundly moving experience to seriously contemplate communicating with the cosmos," he said in a statement.

You can learn more about the One Earth Message and its Kickstarter campaign here: https://www.kickstarter.com/projects/31060842/one-earth-message-a-digital-voyager-golden-record/description

Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.

Dinosaur-Killing Asteroid Cast a 2-Year Shroud of Darkness Over Earth

Dinosaur-Killing Asteroid Cast a 2-Year Shroud of Darkness Over Earth:

Credit: solarseven/Shutterstock

The 2 minutes of darkness caused by the total solar eclipse earlier this week may seem momentous, but it's nothing compared with the prolonged darkness that followed the dinosaur-killing asteroid that collided with Earth about 65.5 million years ago, a new study finds.

When the 6-mile-wide (10 kilometers) asteroid struck, Earth plunged into a darkness that lasted nearly two years, the researchers said.

This darkness was caused, in part, by tremendous amounts of soot that came from wildfires worldwide. Without sunlight, Earth's plants couldn't photosynthesize, and the planet drastically cooled. These two key factors likely toppled global food chains and contributed to the mass extinction at the end of the dinosaur age, known as the Mesozoic, according to the study. [Wipe Out: History's Most Mysterious Extinctions]

The finding may help scientists understand why more than 75 percent of all species, including the non-avian dinosaurs, such as Tyrannosaurus rex, and large marine reptiles, such as the plesiosaur, went extinct after the asteroid slammed into what is now Mexico's Yucatán Peninsula, the researchers said.

Killer asteroid

When the space rock smashed into Earth, it probably triggered earthquakes, tsunamis and even volcanic eruptions, the researchers said. The asteroid hit with such force that it launched vaporized rock sky-high into the atmosphere. Up there, the vaporized rock would have condensed into small particles, called spherules.

When the spherules plunged back down to Earth, they rubbed against one another, causing friction and heating to temperatures hot enough to ignite fires around the world. In fact, a thin band of spherules can still be found in the geologic record, the researchers said.

Most large Mesozoic land animals died in the asteroid's immediate aftermath, "but animals that lived in the oceans or those that could burrow underground or slip underwater temporarily could have survived," the study's lead researcher, Charles Bardeen, a project scientist at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, said in a statement.

"Our study picks up the story after the initial effects — after the earthquakes and the tsunamis and the broiling," Bardeen said. "We wanted to look at the long-term consequences of the amount of soot we think was created and what those consequences might have meant for the animals that were left."

Earth without photosynthesis

Even though researchers found evidence for the asteroid in the late 1970s, there still isn't "universal agreement" on how long Earth was shrouded in darkness after the space rock smacked into the planet, Bardeen told Live Science. [Doomsday: 9 Real Ways Earth Could End]

Other researchers have estimated the soot produced by these ancient wildfires by measuring soot deposits in the geologic record. But Bardeen and his colleagues took another route: they used the NCAR-based Community Earth System Model (CESM) — a modern chemistry-climate model that factors in components related to the atmosphere, land, ocean and sea ice. This model allowed the scientists to simulate the effect of soot in the years following the asteroid impact.

"Different studies have assumed various types of particles including dust, sulfates and soot," Bardeen told Live Science in an email. "All of these particles can block enough sunlight to cool the surface, but only soot is so strongly absorbing that it is self-lofting, can heat the stratosphere and reduces sunlight at the surface light to very low levels."

Furthermore, the researchers used the most up-to-date estimates of the amount of fine soot in the geologic record — that is, 15,000 million tons.

"Our study shows it is dark enough to shut down photosynthesis for up to two years," Bardeen said. "This would have a devastating effect, particularly in the ocean, since the ocean relies upon phytoplankton as a primary source of food and loss of this would be catastrophic to the entire food chain."

Even if the soot levels had been one-third the actual amount, photosynthesis would have still been blocked for an entire year, the researchers found.

Other catastrophic effects

In addition to stopping photosynthesis, this worldwide cloud of soot would have prevented much of the sun's heat from reaching Earth. For more than a year following the crash, the land and oceans would have cooled by as much as 50 degrees Fahrenheit (28 degrees Celsius) and 20 degrees F (11 degrees C), respectively, the researchers found. [Crash! 10 Biggest Impact Craters on Earth]

In contrast, the upper atmosphere, known as the stratosphere, would have warmed because that's where the soot floated around, absorbing the sun's heat. These roasting temperatures would have depleted the ozone, and also allowed for vast quantities of water vapor to hover in the stratosphere. When this water vapor chemically reacted with the stratosphere, it would have created hydrogen compounds that led to further ozone destruction, according to the researchers.

As the ozone disappeared and the soot cleared, damaging doses of ultraviolet light reached Earth, harming life there, the researchers said.

When the stratosphere eventually cooled down, the water vapor there condensed and began raining, abruptly washing away the soot, Bardeen said. As some soot left, the air there cooled, which in turn led the water vapor to condense into ice particles, which washed away more soot.

Once this cooling cycle repeated enough times, the thinning soot layer vanished within months, the researchers found.

Bardeen credited his friend Betty Pierazzo, a senior scientist at the Planetary Science Institute, a nonprofit headquartered in Tucson, Arizona, with securing funding from NASA to do this study. Unfortunately, Pierazzo died before research on the end-Cretaceous asteroid got underway.

Bardeen also noted several limitations, including that the model is based on a modern Earth, and it's unknown whether Earth at the end of the Cretaceous period had different atmospheric properties, such as different concentrations of gases.

The study was published online Monday (Aug. 21) in the journal Proceedings of the National Academy of Sciences.

Original article on Live Science.

Great American Solar Eclipse Breaks NASA's Web-Viewing Records

Great American Solar Eclipse Breaks NASA's Web-Viewing Records:

The “diamond-ring effect” is seen during the total solar eclipse of Aug. 21, 2017. This photo was taken from a NASA Gulfstream III aircraft flying 25,000 feet (7,620 meters) over the Oregon coast.

Credit: Carla Thomas/NASA

In case you didn't notice, people were really into the Great American Solar Eclipse. I mean, really into it. Just take it from NASA.

"With more than 90 million page views on nasa.gov and eclipse2017.nasa.gov, we topped our previous web traffic record about seven times over," agency officials wrote in a postmortem on Thursday (Aug. 24). "For much of the eclipse, we had more than a million simultaneous users on our sites. On social media, we reached more than 3.6 billion nonunique users, and Twitter reports there were more than 6 million eclipse tweets that day."

NASA also estimates that its live eclipse webcast Monday (Aug. 21) got more than 40 million views, another huge number.

"The nasa.gov numbers alone are several times larger than reported streaming numbers for recent Super Bowls, putting the eclipse in the realm of major news, sports and entertainment events," agency officials wrote.

User sessions on NASA websites from May 2015-present, as measured by Google Analytics.

Credit: NASA


The excitement isn't hard to understand. The path of totality Monday extended from Oregon to South Carolina, marking the first time that a total solar eclipse had crossed the U.S. mainland coast to coast since 1918. And no total solar eclipse had even touched the continental United States since 1979.

If you missed Monday's big event, don't fret: Another total solar eclipse will darken American skies on April 8, 2024, moving northeast from Mexico to Texas and then all the way to Maine and up into Canada. Maybe that one will break some more records.

Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.

The Matter with Dark Matter

The Matter with Dark Matter:

The Bullet Cluster is one example of a cosmic feature that indicates the presence of dark matter, a substance that doesn't interact with light or with itself. The image combines X-ray and visible light images, as well as gravitational lensing data.

Credit: X-ray: NASA/CXC/CfA/ M. Markevitch et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/ D.Clowe et al. 
Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.

Paul Sutter is an astrophysicist at The Ohio State University and the chief scientist at COSI Science Center. Sutter is also host of Ask a Spaceman, We Don’t Planet and COSI Science Now. 

Dark matter is more than a name — it's a part of our universe. But it's totally unfamiliar to our everyday experience. Based on the evidence, scientists think it's invisible in the truest sense of the word: It simply doesn't interact with light. Gravity, however, is universal, and so dark matter can still have an influence on the shape and motions of galaxies. But we'll never see it. At least, not directly.

As much as we would prefer to live in a simpler universe, dark matter is not the product of some astronomer's fever dream after a late-night observing session. It's only after decades of careful observations that cosmologists have come to the inescapable conclusion that most of the matter in our universe is simply invisible. [Dark Matter and Dark Energy: The Mystery Explained (Infographic)]

Too hot

The initial hints of dark matter came in the 1930s as astronomer Fritz Zwicky made the first X-ray observations of the Coma Cluster, a dense knot of a thousand galaxies over 300 million light-years away. The galaxies themselves aren't very bright in X-ray light, but the galaxies in a cluster swim in a hot, thin soup of plasma (a gas with some unique properties), which does emit high-energy radiation. In his initial measurements, Zwicky noticed an inconsistency: The plasma was much too hot.

Stable systems like galaxy clusters are a study in balance. In this case, the tendency of a hot gas to expand is balanced by the inward pull of its own gravity. If clusters are to survive for billions of years — which they must, in order for us to actually observe them all over the universe — then these two forces must be in equilibrium. But when Zwicky added up the masses of all the galaxies and the plasma itself, it was far too small; the inward gravitational pull of all that matter wasn't enough to overcome the natural expansion of the gas. In other words, the cluster should've — well, I don't want to say exploded, but you get the idea, long ago.

He named the missing mass "dunkle materie" ("dark matter" in German) and went on to figure out other problems.

Too fast

The concept of dark matter was largely ignored until the 1970s, when astronomer Vera Rubin made her groundbreaking measurements of the rotation speeds of stars within galaxies. Here, again, was a mystery: The stars appear to be orbiting far too fast. The galaxies should've flung themselves apart like a broken-down carnival ride long ago. Instead, there they were, stable as could be.

At this point, a dilemma emerged. Maybe there's some invisible matter floating around inside galaxies and clusters, keeping them gravitationally glued together. But maybe our understanding of how gravity works is just wrong; perhaps Newton's work can explain the way planets move in our solar system but not larger systems.

Without further evidence, two competing hypotheses, dark matter versus modified

Newtonian dynamics (which attempts to explain the mysteries mentioned above by adjusting the details of Newton's work), were on equal scientific footing. We simply couldn't tell them apart.

Too bumpy

That is, until more evidence came in. The first strong hints of a dark universe came from observations of the cosmic microwave background, the ancient afterglow light pattern from the hot and sweaty early years of the universe. That light is uniform to 1 part in 10,000, but buried in that all-surrounding glow are tiny variations, bumps and wiggles that give us a map of the universe at that age.

Those bumps and wiggles are also a study in balance, as multiple competing forces vied for dominance in the hot, dense plasma of the young cosmos. The outward pressure of radiation was resisted by the inward pull of matter's gravity, and that struggle was captured in a snapshot when the CMB was formed. By observing the patterns in the CMB, we can play a straightforward guess-the-recipe game: put various ingredients (normal matter, dark matter, radiation, modified gravity, etc.) into a pot, see what comes out, and compare directly to observations.

And try as we could, we just couldn't make those modified Newtonian dynamics and altered forces of gravity work. But an invisible component to the universe, one that didn't interact with radiation all? It seemed to fit the bill.

Too wide

Still, as is usual in science, there was room for debate. Perhaps not all the observations could be explained by the presence of dark matter, scientists thought. Maybe general relativity — still the most advanced theory we have on the nature of gravity — was not the be-all-end-all gravitational theory.

Those hopes were largely dashed in the most violent way possible — with a bullet. The Bullet Cluster, that is. Two massive galaxy clusters, each weighing in at hundreds of quadrillions of solar masses, slammed into each other long ago. One of the most energetic events in all of nature, the collision turned the clusters inside out, giving us a clue to their contents.

Different observations reveal different components of the Bullet Cluster. Visible light pinpoints the locations of the member galaxies, and they did about what you would expect after the collision: nothing much. The galaxies are so small compared to the volume of the cluster, they simply flew past each other like a swarm of bees.

X-rays expose the fate of the hot plasma between the galaxies. The gas got all tangled up at the midpoint of the collision, with all the complicated bow shocks, cold fronts and turbulence one would expect. This was space weather played out on the grandest of scales.

Also helpful was gravitational lensing, which allows scientists to map the location of matter (whether it interacts directly with radiation or not) based on the way its gravity bends the path of background light. The lensing maps for the Bullet Cluster show an intriguing pattern: most of the stuff in the Bullet Cluster is not tangled up in the center with the hot plasma, and it's not exactly associated with the galaxies, either.

Whatever material the majority of the Bullet Cluster is made of, it doesn't interact with light (otherwise we would see it) and it doesn't interact with itself (otherwise it would've gotten all twisted up during the interaction).

No. 1 with a Bullet

The Bullet Cluster, and a myriad of observations of similar objects, tie together our picture of dark matter along with other lines of evidence like stellar velocities in galaxies, the cosmic microwave background, and more. Nature is trying to tell us something, and we're doing our best to listen: The inescapable conclusion from multiple independent lines of evidence is that most of the matter in our universe is a new kind of particle; one that doesn't interact with light or even itself. It's dark matter.

We still haven't pinned down the exact character of the dark matter particle, but we are closing in on its properties. Sooner or later, nature will reveal to us even its darkest secrets.

Learn more by listening to the episode "What's the matter with dark matter?" on the Ask A Spaceman podcast, available on iTunes and on the Web at http://www.askaspaceman.com. Thanks to @kdawelch, Andreas C., Oscar Z., Peter W., William G., Olivia P., Matthew A, and @TheM4YOR. for the questions that led to this piece! Ask your own question on Twitter using #AskASpaceman or by following Paul @PaulMattSutter and facebook.com/PaulMattSutter.

Follow Calla Cofield @callacofield. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

Satellites Spy 2017 Solar Eclipse from Space (Videos)

Satellites Spy 2017 Solar Eclipse from Space (Videos):

The European Space Agency's Proba-2 satellite captured a partial solar eclipse three times on Aug. 21, 2017

Credit: ESA

While a long, narrow swath of the United States was treated to a total solar eclipse on Monday (Aug. 21), several different spacecraft captured views of a partially blocked sun.

NASA's Solar Dynamics Observatory (SDO) satellite recorded imagery in multiple wavelengths of light, as the following video shows:

The European Space Agency's Proba-2 satellite, which orbits Earth 14.5 times every day, observed a partial eclipse three times on Aug. 21 (just as astronauts aboard the International Space Station did), gaining several different perspectives of the event:

And the Hinode satellite — a joint mission of the Japan Aerospace Exploration Agency, NASA and other partners — captured imagery of the eclipse as well, which you can see looped here:

Monday's eclipse was the most anticipated skywatching event in decades. The 70-mile-wide (113 kilometers) "path of totality" ran through 14 states, from Oregon to South Carolina, marking the first time since 1918 that a total solar eclipse had gone coast to coast across the entire U.S. mainland. And no total solar eclipse had been visible from any part of the contiguous 48 states since 1979.

Weather permitting, everyone in North America outside the path of totality saw a partial solar eclipse Monday, as did observers in Central America, the Caribbean, northern South America, and parts of western Africa and Europe.

And everyone with an Internet connection had the chance to see totality, thanks to a variety of live webcasts. Many people tuned in; Monday's eclipse shattered NASA's web-traffic record, agency officials said.

Note: Space.com senior producer Steve Spaleta contributed to this report.

Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.

CASIS Awards Audacy Grant to Test Radio on Space Station

CASIS Awards Audacy Grant to Test Radio on Space Station:

Audacy's constellation is designed to provide high-availability mission critical communications to users anywhere in near Earth space.

Credit: Audacy

The nonprofit Center for the Advancement of Science in Space (CASIS) awarded a grant Aug. 17 to Audacy that will enable the Silicon Valley startup to demonstrate its high data-rate radio on the International Space Station.

Audacy, a company established in 2015 to create a commercial space-based communications network, plans to send the Audacy Lynq demonstration mission to the space station's NanoRacks External Payload Platform on a NASA commercial cargo fight in late 2018.

"We plan to demonstrate the efficacy of Audacy's high-rate customer terminal, as well as the utility of Audacy's communications services for downloading science and imagery data from customers onboard the ISS," Ellaine Talle, Audacy project lead, said by email.

On Aug. 8, Audacy announced a related project. The firm is working with Scotland's Clyde Space to send a cubesat into orbit in 2018 to demonstrate the performance of terminals customers flying small satellites can use to transmit data to Audacy's ground stations.

Talle declined to say the value of the CASIS award but said it was large enough to cover the cost of launching Audacy Lynq on a commercial cargo flight and a six-month test of Audacy K-band antenna and radio on the space station.

In 2019, Audacy plans to launch three large satellites into medium Earth orbit to relay data from spacecraft in low Earth orbit to ground stations. Audacy is establishing a global network of ground stations to communicate with its future relay satellites and to support customers operating missions beyond the relay satellites' field of view, Talle said.

"While we hope future ISS demonstrations will utilize the relays, this initial mission will only exercise the ground segment," she added.

This story was provided by SpaceNews, dedicated to covering all aspects of the space industry.

How did Hurricane Harvey get so strong?

How did Hurricane Harvey get so strong?:

Hurricane Harvey is whirling towards Texas with winds reaching 130 miles per hour — a Category 4 hurricane that was fueled by an unlucky pit stop over a deep patch of warm water in the Gulf of Mexico.

Warm water feeds hurricanes, which form when a weather disturbance, like a small storm, sucks the moist, warm air over the ocean’s surface into the lower atmosphere. When that moisture-laden air reaches cooler temperatures higher up in the atmosphere, the water condenses to form clouds — which spin and grow, fueled by more warm ocean water as it evaporates.

NEW: NOAA's #GOES16 shows a "sandwich loop" -- a combination of visible and infrared imagery -- of #HurricaneHarvey today, August 25, 2017. pic.twitter.com/o4EBfF69xZ

— NOAA...

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An ancient clay tablet shows that Babylonian scholars might have invented trigonometry

An ancient clay tablet shows that Babylonian scholars might have invented trigonometry:

A new interpretation into the nature of an ancient clay tablet known as Plimpton 322 claims that ancient Babylonians might have developed an advanced form of trigonometry — long before Greek mathematicians are commonly believed to have invented the concept.

That’s the theory put forward by two mathematicians from the University of New South Wales, Daniel F. Mansfield and Norman Wildberger, who published their study in the latest issue of Historia Mathematica. They claim that the tablet demonstrates a sophisticated understanding of mathematics, and that modern assumptions of the field should be reexamined in light of the interpretation.

The tablet in question is approximately five inches wide by three inch tall, and dates back to...

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Supermassive Black Holes Feed on Cosmic Jellyfish

Supermassive Black Holes Feed on Cosmic Jellyfish:

Observations of “Jellyfish galaxies” with ESO’s Very Large Telescope have revealed a previously unknown way to fuel supermassive black holes. It seems the mechanism that produces the tentacles of gas and newborn stars that give these galaxies their nickname also makes it possible for the gas to reach the central regions of the galaxies, feeding the black hole that lurks in each of them and causing it to shine brilliantly. The results appeared today in the journal Nature.

An Italian-led team of astronomers used the MUSE (Multi-Unit Spectroscopic Explorer) instrument on the Very Large Telescope (VLT) at ESO’s Paranal Observatory in Chile to study how gas can be stripped from galaxies. They focused on extreme examples of jellyfish galaxies in nearby galaxy clusters, named after the remarkable long “tentacles” of material that extend for tens of thousands of light-years beyond their galactic discs.

The tentacles of jellyfish galaxies are produced in galaxy clusters by a process called ram pressure stripping. Their mutual gravitational attraction causes galaxies to fall at high speed into galaxy clusters, where they encounter a hot, dense gas which acts like a powerful wind, forcing tails of gas out of the galaxy’s disc and triggering starbursts within it.

Six out of the seven jellyfish galaxies in the study were found to host a supermassive black hole at the center, feeding on the surrounding gas. This fraction is unexpectedly high — among galaxies in general the fraction is less than one in ten.

“This strong link between ram pressure stripping and active black holes was not predicted and has never been reported before,” said team leader Bianca Poggianti from the INAF-Astronomical Observatory of Padova in Italy. “It seems that the central black hole is being fed because some of the gas, rather than being removed, reaches the galaxy center.”

A long-standing question is why only a small fraction of supermassive black holes at the centers of galaxies are active. Supermassive black holes are present in almost all galaxies, so why are only a few accreting matter and shining brightly? These results reveal a previously unknown mechanism by which the black holes can be fed.

Yara Jaffé, an ESO fellow who contributed to the paper explains the significance: “These MUSE observations suggest a novel mechanism for gas to be funneled towards the black hole’s neighborhood. This result is important because it provides a new piece in the puzzle of the poorly understood connections between supermassive black holes and their host galaxies.”

The current observations are part of a much more extensive study of many more jellyfish galaxies that is currently in progress.

“This survey, when completed, will reveal how many, and which, gas-rich galaxies entering clusters go through a period of increased activity at their cores,” concludes Poggianti. “A long-standing puzzle in astronomy has been to understand how galaxies form and change in our expanding and evolving Universe. Jellyfish galaxies are a key to understanding galaxy evolution as they are galaxies caught in the middle of a dramatic transformation.”

Credit: ESO

Scientists Improve Brown Dwarf Weather Forecasts

Scientists Improve Brown Dwarf Weather Forecasts:

Dim objects called brown dwarfs, less massive than the Sun but more massive than Jupiter, have powerful winds and clouds -- specifically, hot patchy clouds made of iron droplets and silicate dust. Scientists recently realized these giant clouds can move and thicken or thin surprisingly rapidly, in less than an Earth day, but did not understand why.

Now, researchers have a new model for explaining how clouds move and change shape in brown dwarfs, using insights from NASA's Spitzer Space Telescope. Giant waves cause large-scale movement of particles in brown dwarfs' atmospheres, changing the thickness of the silicate clouds, researchers report in the journal Science. The study also suggests these clouds are organized in bands confined to different latitudes, traveling with different speeds in different bands.

"This is the first time we have seen atmospheric bands and waves in brown dwarfs," said lead author Daniel Apai, associate professor of astronomy and planetary sciences at the University of Arizona in Tucson.

Just as in Earth's ocean, different types of waves can form in planetary atmospheres. For example, in Earth's atmosphere, very long waves mix cold air from the polar regions to mid-latitudes, which often lead clouds to form or dissipate.

The distribution and motions of the clouds on brown dwarfs in this study are more similar to those seen on Jupiter, Saturn, Uranus and Neptune. Neptune has cloud structures that follow banded paths too, but its clouds are made of ice. Observations of Neptune from NASA's Kepler spacecraft, operating in its K2 mission, were important in this comparison between the planet and brown dwarfs.

"The atmospheric winds of brown dwarfs seem to be more like Jupiter's familiar regular pattern of belts and zones than the chaotic atmospheric boiling seen on the Sun and many other stars," said study co-author Mark Marley at NASA's Ames Research Center in California's Silicon Valley.

Brown dwarfs can be thought of as failed stars because they are too small to fuse chemical elements in their cores. They can also be thought of as "super planets" because they are more massive than Jupiter, yet have roughly the same diameter. Like gas giant planets, brown dwarfs are mostly made of hydrogen and helium, but they are often found apart from any planetary systems. In a 2014 study using Spitzer, scientists found that brown dwarfs commonly have atmospheric storms.

Due to their similarity to giant exoplanets, brown dwarfs are windows into planetary systems beyond our own. It is easier to study brown dwarfs than planets because they often do not have a bright host star that obscures them.

"It is likely the banded structure and large atmospheric waves we found in brown dwarfs will also be common in giant exoplanets," Apai said.

Using Spitzer, scientists monitored brightness changes in six brown dwarfs over more than a year, observing each of them rotate 32 times. As a brown dwarf rotates, its clouds move in and out of the hemisphere seen by the telescope, causing changes in the brightness of the brown dwarf. Scientists then analyzed these brightness variations to explore how silicate clouds are distributed in the brown dwarfs.

Researchers had been expecting these brown dwarfs to have elliptical storms resembling Jupiter's Great Red Spot, caused by high-pressure zones. The Great Red Spot has been present in Jupiter for hundreds of years and changes very slowly: Such "spots" could not explain the rapid changes in brightness that scientists saw while observing these brown dwarfs. The brightness levels of the brown dwarfs varied markedly just over the course of an Earth day.

To make sense of the ups and downs of brightness, scientists had to rethink their assumptions about what was going on in the brown dwarf atmospheres. The best model to explain the variations involves large waves, propagating through the atmosphere with different periods. These waves would make the cloud structures rotate with different speeds in different bands.

University of Arizona researcher Theodora Karalidi used a supercomputer and a new computer algorithm to create maps of how clouds travel on these brown dwarfs.

"When the peaks of the two waves are offset, over the course of the day there are two points of maximum brightness," Karalidi said. "When the waves are in sync, you get one large peak, making the brown dwarf twice as bright as with a single wave."

The results explain the puzzling behavior and brightness changes that researchers previously saw. The next step is to try to better understand what causes the waves that drive cloud behavior.

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena, California. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA.

Credit: spitzer.caltech.edu

Astrophysicists Predict Earth-Like Planet in Star System Only 16 Light Years Away

Astrophysicists Predict Earth-Like Planet in Star System Only 16 Light Years Away:

Astrophysicists at the University of Texas at Arlington have predicted that an Earth-like planet may be lurking in a star system just 16 light years away. The team investigated the star system Gliese 832 for additional exoplanets residing between the two currently known alien worlds in this system. Their computations revealed that an additional Earth-like planet with a dynamically stable configuration may be residing at a distance ranging from 0.25 to 2.0 astronomical unit (AU) from the star.

“According to our calculations, this hypothetical alien world would probably have a mass between 1 to 15 Earth's masses,” said the lead author Suman Satyal, UTA physics researcher, lecturer and laboratory supervisor. The paper is co-authored by John Griffith, UTA undergraduate student and long-time UTA physics professor Zdzislaw Musielak.

The astrophysicists published their findings this week as “Dynamics of a probable Earth-Like Planet in the GJ 832 System” in The Astrophysical Journal.

UTA Physics Chair Alexander Weiss congratulated the researchers on their work, which underscores the University’s commitment to data-driven discovery within its Strategic Plan 2020: Bold Solutions | Global Impact.

“This is an important breakthrough demonstrating the possible existence of a potential new planet orbiting a star close to our own,” Weiss said. “The fact that Dr. Satyal was able to demonstrate that the planet could maintain a stable orbit in the habitable zone of a red dwarf for more than 1 billion years is extremely impressive and demonstrates the world class capabilities of our department’s astrophysics group.”

Gliese 832 is a red dwarf and has just under half the mass and radius of our sun. The star is orbited by a giant Jupiter-like exoplanet designated Gliese 832b and by a super-Earth planet Gliese 832c. The gas giant with 0.64 Jupiter masses is orbiting the star at a distance of 3.53 AU, while the other planet is potentially a rocky world, around five times more massive than the Earth, residing very close its host star—about 0.16 AU.

For this research, the team analyzed the simulated data with an injected Earth-mass planet on this nearby planetary system hoping to find a stable orbital configuration for the planet that may be located in a vast space between the two known planets.

Gliese 832b and Gliese 832c were discovered by the radial velocity technique, which detects variations in the velocity of the central star, due to the changing direction of the gravitational pull from an unseen exoplanet as it orbits the star. By regularly looking at the spectrum of a star – and so, measuring its velocity – one can see if it moves periodically due to the influence of a companion.

"We also used the integrated data from the time evolution of orbital parameters to generate the synthetic radial velocity curves of the known and the Earth-like planets in the system,” said Satyal, who earned his Ph.D. in Astrophysics from UTA in 2014. "We obtained several radial velocity curves for varying masses and distances indicating a possible new middle planet," the astrophysicist noted.

For instance, if the new planet is located around 1 AU from the star, it has an upper mass limit of 10 Earth masses and a generated radial velocity signal of 1.4 meters per second. A planet with about the mass of the Earth at the same location would have radial velocity signal of only 0.14 m/s, thus much smaller and hard to detect with the current technology.

“The existence of this possible planet is supported by long-term orbital stability of the system, orbital dynamics and the synthetic radial velocity signal analysis”, Satyal said. “At the same time, a significantly large number of radial velocity observations, transit method studies, as well as direct imaging are still needed to confirm the presence of possible new planets in the Gliese 832 system.”

In 2014, Noyola, Satyal and Musielak published findings related to radio emissions indicating that an exomoon could be orbiting an exoplanet in The Astrophysical Journal, where they suggested that interactions between Jupiter’s magnetic field and its moon Io may be used to detect exomoons at distant exoplanetary systems.

Zdzislaw Musielak joined the UTA physics faculty in 1998 following his doctoral program at the University of Gdansk in Poland and appointments at the University of Heidelberg in Germany; Massachusetts Institute of Technology, NASA Marshall Space Flight Center and the University of Alabama in Huntsville.

Suman Satyal is a research assistant, laboratory supervisor and physics lecturer at UTA and his research area includes the detection of exoplanets and exomoons, and orbital stability analysis of Exoplanets in single and binary star systems. He previously worked in the National Synchrotron Light Source located at the Brookhaven National Laboratory in New York, where he measured the background in auger-photoemission coincidence spectra associated with multi-electron valence band photoemission processes.

Credit: uta.edu

Astrophysicists Explain the Mysterious Behavior of Cosmic Rays

Astrophysicists Explain the Mysterious Behavior of Cosmic Rays:

A team of scientists from Russia and China has developed a model which explains the nature of high-energy cosmic rays (CRs) in our Galaxy. These CRs have energies exceeding those produced by supernova explosions by one or two orders of magnitude. The model focuses mainly on the recent discovery of giant structures called Fermi bubbles. The paper was published in EPJ Web of Conferences.

One of the key problems in the theory of the origin of cosmic rays (high-energy protons and atomic nuclei) is their acceleration mechanism. The issue was addressed by Vitaly Ginzburg and Sergei Syrovatsky in the 1960s when they suggested that CRs are generated during supernova (SN) explosions in the Galaxy. A specific mechanism of charged particle acceleration by SN shock waves was proposed by Germogen Krymsky and others in 1977. Due to the limited lifetime of the shocks, it is estimated that the maximum energy of the accelerated particles cannot exceed 0.1-1.0 PeV.

The question arises of how to explain the nature of particles with energies above 1 PeV. A major breakthrough in researching the acceleration processes of such particles came when the Fermi Gamma-ray Space Telescope detected two gigantic structures emitting radiation in gamma-ray band in the central area of the Galaxy in November 2010. The discovered structures are elongated and are symmetrically located in the Galactic plane perpendicular to its center, extending 50,000 light-years, or roughly half of the diameter of the Milky Way disk. These structures became known as Fermi bubbles. Later, the Planck telescope team discovered their emission in the microwave band.

The nature of Fermi bubbles is still unclear, however the location of these objects indicates their connection to past or present activity in the center of the galaxy, where a central black hole of 106 solar masses is believed to be located. Modern models relate the bubbles to star formation and/or an energy release in the Galactic center as a result of tidal disruption of stars during their accretion onto a central black hole. The bubbles are not considered to be unique phenomena observed only in the Milky Way and similar structures can be detected in other galactic systems with active nuclei.

Dmitry Chernyshov (MIPT graduate), Vladimir Dogiel (MIPT staff member) and their colleagues from Hong Kong and Taiwan have published a series of papers on the nature of Fermi bubbles. They have shown that X-ray and gamma-ray emission in these areas is due to various processes involving relativistic electrons accelerated by shock waves resulting from stellar matter falling into a black hole. In this case, the shock waves should accelerate both protons and nuclei. However, in contrast to electrons, relativistic protons with bigger masses hardly lose their energy in the Galactic halo and can fill up the entire volume of the galaxy. The authors of the paper suggest that giant Fermi bubbles shock fronts can re-accelerate protons emitted by SN to energies greatly exceeding 1 PeV.

Analysis of cosmic ray re-acceleration showed that Fermi bubbles may be responsible for the formation of the CR spectrum above the “knee” of the observed spectrum, i.e., at energies greater than 3 PeV. To put this into perspective, the energy of accelerated particles in the Large Hadron Collider is also about 1 PeV.

"The proposed model explains the spectral distribution of the observed CR flux. It can be said that the processes we described are capable of re-accelerating galactic cosmic rays generated in supernova explosions. Unlike electrons, protons have a significantly greater lifetime, so when accelerated in Fermi bubbles, they can fill up the volume of the Galaxy and be observed near the Earth. Our model suggests that the cosmic rays containing high-energy protons and nuclei with energy lower than 1 PeV (below the energy range of the observed spectrum’s "knee"), were generated in supernova explosions in the Galactic disk. Such CRs are re-accelerated in Fermi bubbles to energies over 1 PeV (above the "knee"). The final cosmic ray distribution is shown on the spectral diagram," says Vladimir Dogiel.

The researchers have proposed an explanation for the peculiarities in the CR spectrum in the energy range from 3 PeV to 1 EeV. The scientists have proven that particles produced during the SN explosions and which have energies lower than 3 PeV experience re-acceleration in Fermi bubbles when they move from the galactic disk to the halo. Reasonable parameters of the model describing the particles’ acceleration in Fermi bubbles can explain the nature of the spectrum of cosmic rays above 3 PeV. The spectrum below this range remains undisturbed. Thus, the model is able to produce spectral distribution of cosmic rays that is identical to the one observed.

Credit: mipt.ru

Astrophysicist Predicts Detached Eclipsing White Dwarfs to Merge Into an Exotic Star

Astrophysicist Predicts Detached Eclipsing White Dwarfs to Merge Into an Exotic Star:

A University of Oklahoma astrophysicist, Mukremin Kilic, and his team have discovered two detached, eclipsing double white dwarf binaries with orbital periods of 40 and 46 minutes, respectively. White dwarfs are the remnants of Sun-like stars, many of which are found in pairs, or binaries. However, only a handful of white dwarf binaries are known with orbital periods less than one hour in the Milky Way—a galaxy made up of two hundred billion stars—and most have been discovered by Kilic and his colleagues.

“Short-period white dwarf binaries are interesting because they generate gravitational waves. One of the new discoveries emits so much gravitational waves that it is a new verification source for the upcoming Laser Interferometer Space Antenna—a gravitational wave satellite,” Kilic said.

Kilic, an astrophysics professor in the Homer L. Dodge Department of Physics and Astronomy, with OU graduate students Alekzander Kosakowski and A. Gianninas, and collaborator Warren R. Brown, Smithsonian Astrophysical Observatory, discovered the two white dwarf binaries using the MMT 6.5-meter telescope, a joint facility of the Smithsonian Institution and the University of Arizona. Observations at the Apache Point Observatory 3.5-meter telescope revealed that one of the binaries is eclipsing, only the seventh known eclipsing white dwarf binary.

In the future, Kilic and his team will watch in real time as the stars eclipse to measure how they are getting closer and closer—a sign they will likely merge. What occurs when the white dwarfs make contact continues to be a mystery at this point. One possibility is an explosion—a phenomenon known as a supernova. Kilic predicts these two stars will come together and create an “exotic star,” known as R Coronae Borealis. These stars are often identified for their spectacular declines in brightness at irregular intervals. There are only about 65 R Coronae Borealis stars known in our galaxy.

“The existence of double white dwarfs that merge in 20 to 35 million years is remarkable,” Brown said. “It implies that many more such systems must have formed and merged over the age of the Milky Way.”

Kilic’s paper, “Discovery of a Detached, Eclipsing 40 Min Period Double White Dwarf Binary and a Friend: Implications for He+CO White Dwarf Mergers,” is available at https://arxiv.org/abs/1708.05287 in The Astrophysical Journal. Support for this project was provided by the Smithsonian Institution, the National Science Foundation and the National Atmospheric and Space Administration.

Credit: ou.edu