2014년 2월 20일 목요일

Can Quiet, Efficient 'Space Elevators' Really Work?

Is it time to push the "up" button on the space elevator?

A space elevator consisting of an Earth-anchored tether that extends 62,000 miles (100,000 kilometers) into space could eventually provide routine, safe, inexpensive and quiet access to orbit, some researchers say.

A new assessment of the concept has been pulled together titled "Space Elevators: An Assessment of the Technological Feasibility and the Way Forward." The study was conducted by a diverse collection of experts from around the world under the auspices of the International Academy of Astronautics (IAA).

The study's final judgment is twofold: A space elevator appears possible, with the understanding that risks must be mitigated through technological progress…and a space elevator infrastructure could indeed be built via a major international effort.

The tether serving as a space elevator would be used to economically place payloads and eventually people into space using electric vehicles called climbers that drive up and down the tether at train-like speeds. The rotation of the Earth would keep the tether taut and capable of supporting the climbers.

Rooted in history

The notion of a beanstalk-like space elevator is rooted in history. 
Many point to the ahead-of-its-time "thought experiment" published in 1895 by Russian space pioneer Konstantin Tsiolkovsky. He suggested creation of a free-standing tower reaching from the surface of Earth to the height of geostationary orbit (GEO; 22,236 miles, or 35,786 km).

Over the last century or so, writers, scientists, engineers and others have helped finesse the practicality of the space elevator. And the new study marks a major development in the evolution of the idea, says  IAA president Gopalan Madhavan Nair.

"No doubt all the space agencies of the world will welcome such a definitive study that investigates new ways of transportation with major changes associated with inexpensive routine access to GEO and beyond," Nair writes in the new study's preface.

"There is no doubt that the Academy, due to this study, will contribute to advancing international consensus and awareness on the need to search and develop new ways of transportation in conducting space exploration while preserving our universe in the same way we are now trying to preserve our planet Earth," Nair adds.

Elevator operator

While it's always tricky to predict the future study lead editor Peter Swan told Space.com that space elevators are more than just a science-fiction fantasy. "The results of our study are encouraging," he said.

Swan's view is fortified by the late science fact/fiction soothsayer, Arthur C. Clarke, who stated in 2003: "The space elevator will be built ten years after they stop laughing…and they have stopped laughing!"

Swan is chief engineer at SouthWest Analytic Network, Inc. in Paradise Valley, Ariz., and is focused on developing and teaching innovative approaches to "new space" development. He's also head elevator operator of the International Space Elevator Consortium (ISEC), which has organizational members in the United States, Europe and Japan and individual members from around the world.

ISEC's goal is nothing short of getting a lengthy space elevator built.
"The question is when, of course," Swan said. "But the point is that the technologies are progressing in a positive manner, such that we who work in it believe that there will be space elevators."

Pacing technologies

Swan said the giggle factor regarding space elevators is "down significantly" given work carried out over the last decade by a global network of individuals and groups. "Still, there are many, many issues and I certainly would not want to say that it's not a challenging project."

The IAA appraisal delves into a number of issues, such as: Why build a space elevator? Can it be done? How would all the elements fit together to create a system of systems? And what are the technical feasibilities of each major space elevator element?
Two technologies are pacing the development of the space elevator, Swan said.

Producing an ultra-strong space tether and other space elevator components, Swan said, has been advanced by the invention of carbon nanotubes (CNTs) that are 1,000 times better in strength-to-weight ratio than steel. The good news, he said, is that CNTs are being developed with billions of dollars by nanotechnology, electronics, optics, and materials specialists.

Similarly, lightweight solar cells "are coming along nicely," Swan said. "That's an industry that the space elevator people are watching, too. We're not going to drive it, but we can certainly watch it and appreciate the advances."

Money, motivation and desire

Regarding who would erect a space elevator, Swan said the study dives into details. A primarily commercial effort with some government support is possible, as is a public-private enterprise, or an entirely governmental project.

"All three are viable. Any one of them could work. It's a matter of money, motivation and the desire to do it," Swan said, though the study centers on commercial development of the space elevator. "It's conceivable all three could be going on at the same time."

The study team was encouraged by the future, though Swan and others acknowledge there are many questions left to be studied. Indeed, another evaluation of the space elevator idea 10 years hence would be worthwhile, Swan said.

Erasing the rocket equation

Are there any technical, political or policy "showstoppers" that could prevent the space elevator from becoming a reality?

"You're asking the wrong guy," Swan responded. "I am an optimist. I have always had the attitude that good people, motivated by good rationale working hard will make it work. My guess is that space elevators are going to work, whether it's by 2035, 2060 or even 2100."
Swan said the rationale is moving beyond the "rocket equation," which involves tossing away 94 percent of a rocket's mass sitting on the launch pad.

"And it still costs a lot of stinking money to get up there," he said.
The space elevator opens everything up, Swan said. It's a soft ride, a week to GEO. There are no restrictions on the size or shape of payloads.

"People will laugh and ask why did we ever do space rockets…it's a dumb idea," Swan said. "Space elevators are the answer if we can make them work. Why would you do anything else?"

Source: Space.com
By Leonard David, Space.com's Space Insider Columnist 

How NASA's MAVEN Probe Will Investigate Mars Atmosphere Mystery

It's almost five times easier to leave Mars than it is to leave Earth or Venus.
At least, that's the case for many particles in the upper atmosphere. Mars' upper atmosphere is swarming with atoms, ions and molecules actively exiting the planet's sphere of influence. That's why NASA's Mars Atmosphere and Volatile EvolutioN spacecraft, or MAVEN, is headed there: to discover why.

"The basic goal of MAVEN is to understand what happened to the atmosphere of Mars," said Davin Larson, scientific lead for one of the MAVEN instruments, "It's not understood where the oceans and the atmosphere went to. It could have been absorbed into the regolith — sank down into the dirt — but it's pretty well accepted that Mars itself couldn't hide the entire atmosphere, and that most of it escaped."

An atmosphere cannot engineer its own exit. Once an atom, ion or molecule has been captured from space or created in situ, securing release from the planet's sphere of influence typically requires an accomplice. The usual suspect in these cases is the sun.

One mechanism of freeing a captive particle is called Jeans escape. Jeans escape has nothing to do with clothing. It has everything to do with a molecule moving just fast enough to drift away. Jeans escape happens when a planetary atmosphere is heated, often by solar events. Particles that were previously content to hang around begin moving so fast that they attain escape velocity.

Another scenario of loss is photoionization. In this case, fast-moving photons from the sun knock electrons off atmospheric particles. The affected particles then carry a positive charge. Once particles carry a charge, they are more likely to get caught in magnetic fields or picked up by the solar wind and blown away.

In the meantime, the newly liberated electrons bounce around and break up other molecules. This process is known as dissociation. Dissociation can result from native Martian electrons bouncing around or directly from the solar wind. Every day, the solar wind's ions and radiation belts knock the atmosphere away, particle by particle, in a process called sputtering.

Sputtering, dissociation, photoionization, and Jeans escape: any of these mechanisms can cause loss in the ionosphere, or upper atmosphere. This in turns leads to the slow bleeding away of the lower atmosphere. In the absence of a protective magnetic field, these escape phenomena lead to atmospheric loss on a grand scale. Scientists think that Mars lost its planet-wide magnetic field about 3.8 billion years ago, and that the subsequent disappearance of its air and oceans have been largely driven by the sun.

Measuring the loss

To examine that hypothesis, MAVEN — which launched in November and is due to arrive at Mars this September — has been equipped with four sensors that measure every aspect of the solar input. Three of them have the word 'solar' in the title: the Solar Wind Electron Analyzer (SWEA), the Solar Energetic Particles (SEP), and the Solar Wind Ion Analyzer (SWIA). Larson, mentioned above, is the science lead on SEP, an instrument named after what it detects.

Solar energetic particles (SEPs), according to Larson, "are one form of energy that can ionize and heat the gas in the upper atmosphere of Mars." SEPs can arrive as part of large and small events. Small events would be SEPs blown by a light solar wind. Large events launch SEPs directly from the surface of the sun. Small SEP events might only sputter away molecules in the upper ionosphere, close to the boundary with space. During bigger events, SEPs can act like powerful cosmic rays and plow through everything in their path.
"The more energetic the particle, the deeper it tends to get into the atmosphere," Larson said. "There is more ionization, more excitation, more sputtering, more heating of the atmosphere."

Heating of the atmosphere gives rise to Jeans escape, which will be observed by other MAVEN instruments. Meanwhile, the SEP instrument sits on either side of the probe's central disk. Poised at the lower margin, the SEP sensors watch patiently for the interplanetary particles that create dissociation, ionization and sputtering.

Eye of an insect

On the other side of MAVEN's golden body, protruding 5 feet (1.5 meters) into space, is another Solar Package instrument: SWEA. With its glistening black patina and thatched circular grating, SWEA resembles the eye of a large insect.

"There are actually two concentric bug-eye grids," said David Mitchell, SWEA's science lead. "The instrument places a voltage across the inner and outer grids to decelerate incoming electrons without altering their trajectories."

Once electrons enter the eye, an internal electric field slows them down so SWEA can observe them. SWEA establishes which way the electrons were going and how quickly, and determines if those electrons originated in the sun or are native to Mars. In this way, it can read the solar wind's speed and direction of the ionosphere, where particles from the sun and Mars continually interplay, and contributing to sputtering the atmosphere away.

The solar wind itself is the object of yet another instrument's examination. With its sensor always turned toward the sun, the Solar Wind Ion Analyzer will measure the speed, contents, temperature and density of the solar wind.
"SWIA is built and designed to measure the incoming solar wind ions, both upstream and after the encounter the magnetosphere of Mars," said SWIA principal investigator Jasper Halekas. "These ions provide an important energy input to the magnetosphere of Mars, and may help determine how much of Mars' atmosphere ultimately escapes."

Around the atmosphere of any planet, electrons liberated by photoionization can form a free-flowing cloud called a plasmasphere. Mars' plasmasphere rotates independently from the planet, almost wrapping around it at times. Blobs of plasma trail behind Mars like two tails, blown there by the steady solar wind. The tails trail farther and farther behind Mars and are eventually lost to space.

While the solar wind's ions and electrons tend to remain in high altitudes near the plasmasphere, photons in the extreme ultraviolent part of the spectrum can ionize atmospheric particles all the way down to the ground. Extreme UV (EUV) radiation may be why Mars has too many heavy isotopes of elements like hydrogen and carbon, and too little air and water. In breaking apart chemical bonds, EUV may have played a part in helping the lighter bit of H2O and CO2 break away and escape.

"Knowing the amount of EUV going into an atmosphere and how that EUV varies lets scientists understand the temperature, ionization, composition, and escape rates from that atmosphere," said Frank Eparvier, EUV instrument lead.
By measuring the extreme UV in Mars' atmosphere today, and adding in data about the number of ionized molecules and their rates of escape, we may deduce how much H2O and CO2existed on Mars four billion years ago.

Like SEP, the EUV sensors were named after what they detect. The EUV sensors sit anchored at the bottom of two 23-foot (7 m) booms. Their presence there rounds out observations of incoming solar particles in the upper atmosphere. SWIA watches the solar wind. SWEA sorts solar electrons, counting how many charges stick in Mars' atmosphere, and how deep into they penetrate. SEP detects ionizing particles and EUV senses ionizing radiation all through the upper atmosphere, brought to Mars largely by coronal mass ejections (CMEs).

CMEs, SEPs and the solar wind have each played a part in divesting Mars of its atmosphere over the last four billion years. With its Sun, Solar Wind and Storms instruments, MAVEN will tell us how much of each is occurring and where.

Coupled with measurements from the five other instruments on board, by this time next year we'll have a more complete picture of what's entering in and leaving the ionosphere. We'll have a better idea of what happened to 85-95 percent of Mars' original atmosphere, which likely supported rivers, lakes and shallow oceans. Above all, for the first time ever, we'll know much energy it takes to strip away the sky.

Source: Space.com
By Sheyna E. Gifford, MD, Astrobiology Magazine

No Meteorite Behind 'Jelly Doughnut' Mars Rock, Pictures Show

New photos of the Martian landscape further rule out a meteorite impact as the culprit behind the "jelly doughnut" rock that mysteriously appeared in front of one of NASA's Mars rovers last month.

NASA's Mars Reconnaissance Orbiter snapped pictures as it flew above the Opportunity rover on Feb. 14, and this week, the space agency released a photo from that flyover campaign. In a view that covers a patch about 0.25 miles (0.4 kilometers) wide, Opportunity looks like a speck and some of the rover's faint tracks are visible, but there are no new impact craters in sight, NASA officials say.

A fresh meteorite scar might have explained how a rock got tossed in front of Opportunity last month. The rock was dubbed "Pinnacle Island," and Steve Squyres, the rover's lead scientist at Cornell University, had noted its resemblance to a jelly doughnut. The strange feature materialized in Opportunity's field of view on Jan. 8, and it was absent in pictures of the same place just days before.

NASA scientists had already concluded that the rock was most likely kicked up by one of Opportunity's wheels. Using further observations from the rover, researchers said they could trace where the rock had been struck, cracked and moved.

But that conclusion hasn't stopped fringe theories from cropping up. One person has even filed a lawsuit against the space agency, alleging that NASA has failed to properly investigate what is likely a mushroom-like fungus growing on the Red Planet.

Opportunity, which recently celebrated its 10th anniversary on Mars, is now exploring Murray Ridge, a spot on the western wall of Endeavour Crater, which spans about 14 miles (22 km) in diameter. With the Pinnacle Island enigma behind it, Opportunity is being steered uphill to check out exposed rock layers on the slope of the ridge.

Source: Space.com
By Megan Gannon, News Editor 

2014년 2월 15일 토요일

Mysterious Energy Ribbon at Solar System's Edge a 'Cosmic Roadmap'

A strange ribbon of energy and particles at the edge of the solar system first spotted by a NASA spacecraft appears to serve as a sort of "roadmap in the sky" for the interstellar magnetic field, scientists say.

By comparing ground-based studies and in-space observations of solar system's mysterious energy ribbon, which was first discovered by NASA's Interstellar Boundary Explorer (IBEX) in 2009, scientists are learning more details about the conditions at the solar system's edge. The study also sheds light into the sun's environment protects the solar system from high-energy cosmic rays.

"What I always have been trying to do was to establish a clear connection between the very high-energy cosmic rays we're seeing [from the ground] and what IBEX is seeing," study leader Nathan Schwadron, a physicist at the University of New Hampshire, told Space.com.

Previously, maps from ground-based observatories showed researchers that clusters of cosmic rays — extremely high-energy particles that originate from supernovas — are correlated with the IBEX ribbon. The ribbon is roughly perpendicular to the interstellar magnetic field while cosmic rays stream, on average, along the interstellar magnetic field. (The particles themselves are created from interactions between the solar wind and interstellar matter.)

In the longer term, Schwadron said work like this will help scientists better understand more about the boundary between our solar system and interstellar space. This is a region that only one mission — NASA's Voyager 1 spacecraft — has reached so far, and scientists know little about what that environment is like.

Traveling through the transition zone

The sun's sphere of influence in the solar system is known as the heliosphere. The sun's "solar wind" of high-energy particles flows within the heliosphere and pushes back against high-energy cosmic rays originating in interstellar space. The transition zone between these two regions is called the heliosheath.

Here's where a mystery arises: Voyager 1's measurements of the magnetic field from the edge of interstellar space show a starkly different direction of the magnetic field inferred in the IBEX ribbon, Schwadron said.

"At that point, you say to yourself what’s wrong? What could possibly be the issue? It seems like we now have good independent confirmation that the IBEX ribbon is ordered by the interstellar magnetic field, and we know that Voyager 1 takes fairly good measurements," Schwadron said.

The few studies examining this issue, showing little consensus. An October paper co-authored by Schwadron in Astrophysical Journal Letters argued that Voyager 1 could be measuring interstellar plasma coming in through magnetic field lines, but may still be in the heliosheath itself. This stands in contrast to findings from NASA and other science groups saying Voyager 1 is definitively in interstellar space.

The researchers noted that Voyager 1 is picking up its information "at a specific time and place", but IBEX's data is collected and averaged across vast distances, so that could also lead to discrepancies.

"What is really missing here is our understanding of the physics," Schwadron said, adding that reconnection between magnetic field lines could be an example of something that changes the conditions of the boundary region.

Source of Article: Space.com
By Elizabeth Howell, Space.com Contributor 

How Nuclear Bombs Could Save Earth from Killer Asteroids

The most destructive weapon humanity has ever developed could help our species avoid going the way of the dinosaurs.

Pretty much any asteroid that poses a threat to Earth can be blasted out of the heavens using a nuclear bomb, even with warning times of a week or less, say a team of scientists who have been developing the idea.

"We have the solution, using our baseline concept, to be able to mitigate the asteroid-impact threat, with any range of warning," Bong Wie, of Iowa State University, said Feb. 6 at the 2014 NASA Innovative Advanced Concepts (NIAC) meeting at Stanford University.

A very real threat

Wie presented his team's latest findings nearly a year to the day after a previously undetected 65-foot-wide (20 meters) space rock detonated in the skies above the Russian city of Chelyabinsk, injuring 1,500 people.

He and many other researchers regard the Feb. 15, 2013 Russian meteor explosion— which took locals and scientists alike by surprise — as a wake-up call about the threat Earth faces from incoming space rocks.

"A couple of years ago, I had to use the dinosaur example to justify our research," he said, referring to the asteroid impact that wiped out the giant reptiles 65 million years ago. "Now, that's no more — we had this major event."
It's just a matter of time before Earth gets hit again, Wie and other scientists stress — and the next strike may inflict far more damage.

In a perfect world, hazardous space rocks would be detected decades before their close encounters with Earth, giving humanity enough time to launch robotic "gravity tractors," which would nudge the asteroids off course by flying alongside them for long periods of time.

But our species needs a strategy to employ when a dangerous asteroid pops onto the radar with much less time to spare — less than a year, for example. And nuclear bombs are the best answer, Wie said.

A one-two punch

Wie and his colleagues are developing a concept spacecraft called the Hypervelocity Asteroid Intercept Vehicle, or HAIV. They've gotten two rounds of NIAC funding for their work, one in 2011 and the other in 2012.

The HAIV would rendezvous with an asteroid in deep space, then send a kinetic impactor barreling into the object to blast out a crater. The nuclear bomb would follow one millisecond behind — perhaps attached via a long boom, or perhaps flying freely — and then detonate inside the hole, shattering the asteroid into millions of tiny pieces.
Excavating a crater for the bomb increases its destructive power by a factor of 20, Wie said.

Some of the resulting asteroid fragments may still impact Earth, depending on how far away from our planet the explosion occurred. But the effects are likely to be minimal, Wie said.
For example, a 1,000-foot-wide (300 m) asteroid can be neutralized far outside Earth's gravitational field with a warning time of just 30 days, according to Wie. Computer simulations suggest that less than 0.1 percent of the destroyed object's mass would eventually strike our planet.

"We would have a heavy meteor shower, or maybe 100 Chelyabinsk meteor events," Wie said. But doing nothing, he added, invites a single impact with 150,000 times the power of the bomb dropped on the Japanese city of Hiroshima during World War II.

A complete solution?

Wie and his team suggest that the HAIV concept be coupled with an asteroid-warning system, such as the Asteroid Terrestrial-impact Last Alert System (ATLAS), a survey effort being led by the University of Hawaii with $5 million in NASA funding.
When it's fully operational in 2015, ATLAS should be able to provide a one-day warning for asteroids 26 feet (8 m) wide, a one-week alert for space rocks measuring 148 feet (45 m) across and a three-week warning for 459-foot (140 m) asteroids.
That should provide plenty of time to launch an HAIV mission, which would likely cost about $500 million, Wie said.

"If our system is going to be built, tested, pre-deployed, ready to be launched at any time, then we solve the problem," he said.

Source of Article: Space.com
By Mike Wall, Senior Writer

NASA's 'Jelly Doughnut' Mars Rock Mystery Solved

Scientists have solved the mystery of the strange "jelly doughnut" rock on Mars.
NASA's Opportunity rover spotted an odd Martian rock that looked like a doughnut on Jan. 8. Four days earlier, however, the rock wasn't there at all. So how did the rock appear? Alien rock throwers? A nearby meteorite impact?

The truth is much less surprising. Scientists working with the intrepid robot have just confirmed that the rock (called Pinnacle Island) was simply kicked up by one of Opportunity's wheels as it made its way across the planet's surface.

"Once we moved Opportunity a short distance, after inspecting Pinnacle Island, we could see directly uphill an overturned rock that has the same unusual appearance," Opportunity deputy principal investigator Ray Arvidson, of Washington University in St. Louis, said in a statement. "We drove over it. We can see the track. That's where Pinnacle Island came from."

The rock stirred up enough controversy that a concerned citizen even filed a lawsuit against the space agency, claiming that NASA failed to properly investigate a possible fungus growing on the Red Planet.

Although researchers figured out where the rock came from, there are other weird aspects of the Pinnacle Island tale. Using Opportunity's tools, mission scientists have discovered that the rock has very high levels of sulfur and manganese. Both of those elements are water-soluble, suggesting that they were concentrated in the rock due to the "action of water," NASA officials said.

"This may have happened just beneath the surface relatively recently, or it may have happened deeper below ground longer ago and then, by serendipity, erosion stripped away material above it and made it accessible to our wheels," Arvidson said.

The rock is located in a spot on "Murray Ridge" along the wall of Endeavour Crater, where Opportunity is spending the Martian winter. Now that the rover is done examining Pinnacle Island, the Opportunity team is planning to drive the rover uphill to check out exposed rock layers on a different part of the Martian surface.

"We are now past the minimum solar-energy point of this Martian winter," Opportunity project manager John Callas, of NASA's Jet Propulsion Laboratory in Pasadena, Calif., said in a statement. "We now can expect to have more energy available each week. What's more, recent winds removed some dust from the rover's solar array. So we have higher performance from the array than the previous two winters."

Opportunity has been exploring Mars since 2004, landing on the Red Planet a few weeks after its twin, Spirit, touched down on the Martian surface. Both rovers were assigned 90-day missions, but Spirit gathered data until 2010 and Opportunity is still roving along.

Source of Article: Space.com
By: Miriam Kramer, Staff Writer

2014년 2월 5일 수요일

Wobbly Alien Planet with Wild Seasons Found by NASA Telescope

Astronomers have discovered an alien planet that wobbles at such a dizzying rate that its seasons must fluctuate wildly.

Throughout all of the planet's fast-changing seasons, however, no forecast would be friendly to humans. The warm planet is a gassy super-Neptune that orbits too close to its two parent stars to be in its system's "habitable zone," the region where temperatures would allow liquid water, and perhaps life as we know it, to exist.

The faraway world, which lies 2,300 light-years away in the constellation Cygnus, was discovered by NASA's planet-hunting Kepler space telescope. Dubbed Kepler-413b, the planet orbits a pair of orange and red dwarf stars every 66 days.

Kepler was designed to detect exoplanets by noticing the dips in brightness caused when these worlds transit, or cross in front of, their parent stars. Normally these transits occur in a regular pattern, but Kepler-413b behaved strangely.

"What we see in the Kepler data over 1,500 days is three transits in the first 180 days (one transit every 66 days), then we had 800 days with no transits at all," study lead investigator Veselin Kostov, of the Space Telescope Science Institute and Johns Hopkins University, said in a statement. "After that, we saw five more transits in a row."

Kostov and colleagues concluded that the planet's wobble must be causing it to move up or down relative to our view, so much so that it sometimes doesn't appear to cross in front of its parent stars. (A NASA statement compared the planet's motions to a child's spinning top on the rim of a wobbling bicycle wheel rotating on its side.)

The scientists determined that the planet's axial tilt can vary by as much as 30 degrees over 11 years,. For comparison, Earth's tilt has shifted 23.5 degrees over 26,000 years. The researchers say it's amazing that this planet is wobbling, or precessesing, so much on a human time scale, and they say it's possible that there are other planets like Kepler-413b awaiting discovery.

"Presumably there are planets out there like this one that we're not seeing because we're in the unfavorable period," Peter McCullough, a team member from STScI and JHU, said in a statement.

Kostov and colleagues are still investigating what causes the extreme wobble of the gas planet, which has a mass about 65 times that of Earth. They say Kepler-413b's orbit may have been tilted by other planets in the system or by a nearby star exerting gravitational influence.

The research was detailed in the Jan. 29 issue of The Astrophysical Journal.
Kepler was disabled last year after suffering a major failure, but engineers are have developed a possible new mission that would use the spacecraft in its compromised state. The $600 million Kepler mission launched in 2009 and has detected more than 3,500 exoplanet candidates to date.

Source of Article: Space.com
By Megan Gannon, News Editor

Black Holes Heated Early Universe Slower Than Previously Thought

Black holes acting as companions to early stars may have taken more time to raise the temperature of the ancient universe than previously thought, a new study suggests.
Scientists found that the energy streaming from these early pairings took longer to raise the temperature of the universe, which means astronomers could detect signs of the heating process previously thought to be out of bounds. Two cosmic milestones occurred in the universe a few hundred million years after the Big Bang— dominating hydrogen gas was both heated and made transparent.

"Previously, it was thought that these two milestones are well separated in time, and thus in observational data as well," study co-author Rennan Barkana, of Tel Aviv University, told Space.com via email.

Barkana worked with lead study author Anastasia Fialkov, also of Tel Aviv University, and Eli Visbal, of Columbia University, to determine that the heating most likely overlapped the early, and perhaps middle, part of reionization, the process that allowed the events of the early universe to become visible to scientists today, making the heating potentially observable to astronomers today.

High energy, low heat

Like stars today, stars in the early universe often had companions. When one of the two companion stars exploded to create a black hole, the new system — known as an X-ray binary (XRB) — emitted energy in the X-ray spectra. Although other systems emit X-rays, XRBs are the brightest, dominating the total cosmic intensity of X-rays.

In the early universe, energetic X-rays served to heat the hydrogen gas that filled space. Previously, scientists suspected that low-energy X-rays provided the energy to heat the early universe. But recent improved models of XRBs revealed that high-energy X-rays dominated the scene.

Fialkov's team used new models to recalculate the amount of time required to increase the temperature of the hydrogen spread throughout the universe. Surprisingly, the researchers said, the higher-energy X-rays took longer to raise temperatures than the less-powerful rays.

"High-energy X-rays typically travel a long distance, over a long time, before their energy is absorbed and heats the gas," Barkana said. "Eventually, all their energy is deposited, but 'eventually' is too late in the early universe, when galaxy and star formation are ramping up."

After the Big Bang, protons and neutrons joined together to form neutral hydrogen, the most basic element on the periodic table and the dominate gas in the universe. The dominance of neutral hydrogen rendered the universe opaque, in a period known as the cosmic 'Dark Ages' that existed during the first 100 million years after the Big Bang. Only after stars and galaxies began to form and release ultraviolet light did the universe begin the process of reionization, clearing the hydrogen gas and making the universe once again transparent for high-energy events.

The early stars didn't manage to clear the darkness of the early universe until nearly a billion years had passed since the Big Bang. As a result, astronomers struggle to peer through the darkness to observe the first billion years in the life of the 13.8-billion-year-old universe. However, low-energy radiation does pass through the cosmic gas and is a promising probe of those early times.

With low-energy X-rays dominating the scene, hydrogen gas in the early universe would have heated quickly as it absorbed energy. Under this model, scientists would have a difficult time observing any signs of the heating, which would have finished long before reionization was complete.

But the slowdown caused by the presence of high-energy X-rays means that the heating should overlap the spreading transparency, allowing scientists to capture glimpses of the process.

Source of Article: Space.com
By Nola Taylor Redd, Space.com Contributor