First Detection of Gravitational Waves from Neutron-Star Crash Marks New Era of Astronomy


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First Detection of Gravitational Waves from Neutron-Star Crash Marks New Era of Astronomy

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  A new era of astronomy has begun.

For the first time ever, scientists have spotted both gravitational wavesand light coming from the same cosmic event — in this case, the cataclysmic merger of two superdense stellar corpses known as neutron stars.

The landmark discovery initiates the field of “multimessenger astrophysics,” which promises to reveal exciting new insights about the cosmos, researchers said. The find also provides the first solid evidence that neutron-star smashups are the source of much of the universe’s gold, platinum and other heavy elements. [How Gravitational Waves Work (Infographic)]

How do researchers describe the finding? “Superlatives fail,” said Richard O’Shaughnessy, a scientist with the Laser Interferometer Gravitational-wave Observatory (LIGO) project.

“This is a transformation in the way that we’re going to do astronomy,” O’Shaughnessy, who’s based at the Rochester Institute of Technology’s Center for Computational Relativity and Gravitation, told Space.com. “It’s fantastic.”

An artist’s illustration of merging neutron stars.

An artist’s illustration of merging neutron stars.

Credit: Robin Dienel; Carnegie Institution for Science

Gravitational waves are ripples in the fabric of space-time generated by the acceleration of massive cosmic objects. These ripples move at the speed of light, but they’re much more penetrating; they don’t get scattered or absorbed the way light does.

Albert Einstein first predicted the existence of gravitational waves in histheory of general relativity, which was published in 1916. But it took a century for astronomers to detect them directly. That milestone came in September 2015, when LIGO saw gravitational waves emitted by two merging black holes.

That initial find won three project co-founders the 2017 Nobel Prize in physics. The LIGO team soon followed it up with three other discoveries, all of which also traced back to colliding black holes.

The fifth gravitational-wave detection — which was announced today (Oct. 16) at news conferences around the world, and in a raft of papers in multiple scientific journals — is something altogether new. On Aug. 17, 2017, LIGO’s two detectors, which are located in Louisiana and Washington state, picked up a signal that lasted about 100 seconds — far longer than the fraction-of-a-second “chirps” spawned by merging black holes.

“It immediately appeared to us the source was likely to be neutron stars, the other coveted source we were hoping to see — and promising the world we would see,” David Shoemaker, a spokesman for the LIGO Scientific Collaboration and a senior research scientist at the Massachusetts Institute of Technology’s Kavli Institute for Astrophysics and Space Research, said in a statement. [How to Detect Gravitational Waves: LIGO Simply Explained (Video)]

Indeed, calculations by the LIGO team suggest that each of the colliding objects harbors between 1.1 and 1.6 times the mass of the sun, putting both objects in neutron-star territory in terms of mass. (Each of the merging black holes responsible for the other detected signals contained dozens of solar masses.)

Neutron stars, the collapsed remnants of massive stars that have died in supernova explosions, are some of the most exotic objects in the universe.

“They are as close as you can get to a black hole without actually being a black hole,” theoretical astrophysicist Tony Piro, of the Observatories of the Carnegie Institution for Science in Pasadena, California, said in a different statement. “Just one teaspoon of a neutron star weighs as much as all the people on Earth combined.”

Right: An image taken on Aug. 17, 2017, with the Swope Telescope at the Las Campanas Observatory in Chile shows the light source generated by a neutron-star merger in the galaxy NGC 4993. Left: In this photo taken on April 28, 2017, with the Hubble Space Telescope, the neutron star merger has not occurred and the light source, known as SSS17a, is not visible.

Right: An image taken on Aug. 17, 2017, with the Swope Telescope at the Las Campanas Observatory in Chile shows the light source generated by a neutron-star merger in the galaxy NGC 4993. Left: In this photo taken on April 28, 2017, with the Hubble Space Telescope, the neutron star merger has not occurred and the light source, known as SSS17a, is not visible.

Credit: D.A. Coulter, et al.

The Virgo gravitational-wave detector near Pisa, Italy, also picked up a signal from the Aug. 17 event, which was dubbed GW170817 (for the date of its occurrence). And NASA’s Fermi Gamma-ray Space Telescope spotted a burst of gamma-rays — the highest-energy form of light — at about the same time, coming from the same general location.

All of this information allowed researchers to trace the signal’s source to a small patch of the southern sky. Discovery team members passed this information on to colleagues around the world, asking them to search that patch with ground- and space-based telescopes.

This teamwork soon bore fruit. Just hours after the gravitational-wave detection, Piro and his colleagues spotted a matching optical light source about 130 million light-years from Earth, using a telescope at Las Campanas Observatory in Chile.

“We saw a bright-blue source of light in a nearby galaxy — the first time the glowing debris from a neutron star merger had ever been observed,” team member Josh Simon, also of the Carnegie Observatories, said in a statement. “It was definitely a thrilling moment.”

Then, about an hour later, researchers using the Gemini South telescope, also in Chile, spotted that same source in infrared light. Other teams using a variety of instruments soon studied the source across the electromagnetic spectrum, from radio to X-ray wavelengths.

This work revealed that some of the observed light was the radioactive glow of heavy elements such as gold and uranium, which were produced when the two neutron stars collided.

That’s a big deal. Scientists already knew the provenance of lighter elements — most hydrogen and helium was generated during the Big Bang, and other elements all the way up to iron are created by nuclear fusion processes inside stars — but the origin of the heavy stuff was not well understood. [The Big Bang to Now: 10 Easy Steps]

“We’ve shown that the heaviest elements in the periodic table, whose origin was shrouded in mystery until today, are made in the mergers of neutron stars,” Edo Berger, of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, said in a statement. Berger leads a team that studied the event using the Dark Energy Camera at the Cerro Tololo Inter-American Observatory in Chile.

“Each merger can produce more than an Earth’s mass of precious metals like gold and platinum and many of the rare elements found in our cellphones,” Berger said in a statement.

Indeed, GW170817 likely produced about 10 Earth masses’ worth of gold and uranium, researchers said.

The in-depth investigation of GW170817 has revealed other important insights.

For example, this work demonstrated that gravitational waves do indeed move at the speed of light, as theory predicts. (The Fermi space telescope detected the gamma-ray burst just 2 seconds after the gravitational-wave signal ended.) And astronomers now know a little more about neutron stars.

“There are some types of things that neutron stars could be made of that we’re sure they’re not made of, because they didn’t squish that much” during the merger, O’Shaughnessy said.

But GW170817 is just the beginning. For instance, such “multimessenger” observations provide another way to calibrate distances to celestial objects, said the CfA’s Avi Loeb, who also chairs Harvard University’s astronomy department.

Such measurements could, in theory, help scientists finally nail down the rate of the universe’s expansion. Estimates of this value, known as theHubble Constant, vary depending on whether they were calculated using observations of supernova explosions or the cosmic microwave background (the ancient light left over from the Big Bang), said Loeb, who was not involved in the newly announced discovery.

“Here’s another path that is open that was not available before,” he told Space.com.

Many other such paths are likely to open, O’Shaughnessy stressed, and where they may lead is anyone’s guess.

“I think probably the most exciting thing of all is really that it’s the beginning,” O’Shaughnessy said of the new discovery. “It resets the board for what astronomy is going to look like in the years to come, now that we have multiple ways of simultaneously probing a transient and violent universe.”

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

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Huge Gravitational Waves Discovery Gets the Nobel Prize It Deserves


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Huge Gravitational Waves Discovery Gets the Nobel Prize It Deserves

 https://gizmodo.com/huge-gravitational-waves-discovery-gets-the-nobel-prize-1819101178
Image: NASA/CXC/A.Hobart/Wikimedia Commons

The Nobel Prizes are important and all. But if you’ve been paying attention to physics for the past two years, this year’s prize is akin to saying “my beautiful dog has won the Good Boy prize.” We’re very excited, but we aren’t surprised.

Today, the Royal Swedish Academy of Sciences has awarded the 2017 Nobel Prize in Physics half to Rainer Weiss and half jointly to Barry C. Barish and Kip S. Thorne, all from the LIGO/VIRGO Collaboration, “for decisive contributions to the LIGO detector and the observation of gravitational waves.”

These waves have a long story behind them. Back in 1915, Albert Einstein published his famous theory of general relativity, the one that says that massive things can distort the shape of space itself. He, and others, proposed that the force of gravity itself should be able to ripple through space, changing its shape like as it traveled like a wave through a pond . Einstein later came to doubt the existence of gravitational waves, but another physicist spotted an error in his work. By the 1950s, even before theorists accepted the existence of the waves’ most apparent sources (black holes), scientists had proven mathematically that these gravitational waves should be out there, according to the Nobel committee’s Scientific Background statement.

Tantalizing hints followed. In 1969, Joseph Weber from University of Maryland claimed a discovery in a small detector, a bar floating on liquid with special crystals meant to convert vibrational energy to electricity. But similar experiments in the 1970s couldn’t recreate the results. If scientists wanted to prove the existence of the waves, they’d need to go bigger, and build something more sensitive.

Thorne and Weiss were dedicated to finding the waves, and designed a new detector. After some bureaucratic and planning hiccups, it was Barish who saw the construction to its completion. This resulted in a pair of several-kilometer-long, L-shaped experiments called the Laser Interferometer Gravitational Wave Observatories in Louisiana and Washington State, that cost the United States’ National Science Foundation several hundreds of millions of dollars. These detectors consist of a laser beam split down each pipe’s length, bouncing off mirrors and returning to a single spot where their light waves cancel each other out. A gravitational wave should make the beams vibrate in and out of phase with each other the tiniest amount, creating a little bit of light that shines into a new detector.

Then, on Sept. 14, 2015, almost immediately after a major upgrade, ripples from a pair of colliding black holes 29 and 36 times the mass of our own Sun 1.3 billion light years away arrived on planet Earth, showing up as a tiny vibrations in the data, with an amplitude far smaller than an atom. The team announced their discovery on February 11, 2016. It was very exciting and we clapped a lot.

This might sound like the end of the story, but is in fact the beginning; since then, several more waves have been detected from other pairs of colliding black holes, and a third detector sensitive enough to spot the waves called Virgo has joined the mix. Lots of physicists are dreaming up new ways to use the detectors to discover more exotic things like the elusive dark matter or tobetter understand black holes. Rumors are swelling about potential new sources of gravitational waves that might also come with corresponding light waves that more traditional telescopes can spot.

In the current era, some scientists are re-thinking how the Physics prize is awarded. The Royal Swedish Academy can only award the Nobel Prize in Physics to a maximum three people, but some experiments often feature a thousand physicists working hard to keep the science happening. And rather than single discoveries, there is often lots of incremental work that eventually sums into a larger understanding of the universe, Princeton physicist Shivaji Sondhi and Stanford physicist Steven Kivelson wrote in an editorial published recently in Nature Physics. They propose offering the prize to more people simultaneously, identifying the most important scientists to a given effort, or even creating a prize that instead rewards scientists for cumulative lifetime achievement.

Last year, Science magazine guessed Weiss and Thorne would win, and lamented that Barish might not receive the reward.

Now that LIGO has received their award, the real question is: What will they discover next?

[The Royal Swedish Academy of Sciences]

Why Has Our Sun Been Freaking Out So Much Lately?


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Why Has Our Sun Been Freaking Out So Much Lately?

The solar flare as seen by NASA’s Solar Dynamics Observatory on September 10, 2017. (Image: NASA/SDO/Goddard)

Since early last week, the Sun has belched out a steady stream of solar flares, including the most powerful burst recorded in the star’s current 11-year cycle. It sounds very alarming, but scientists say this is simply what stars do every now and then, and that there’s nothing to be concerned about.

Solar flares are powerful bursts of radiation that stream out into space after periods of sunspot-associated magnetic activity. Sunspots are surface features that occasionally form owing to the strong magnetic field lines that come up from within the Sun and pierce through the solar surface. Solar flares are the largest explosive events in the Solar System, producing bright flashes that last anywhere from a few minutes to a few hours. Earth’s atmosphere protects us from most of their harmful rays, but this radiation can disturb GPS, radio, and communications signals, particularly near our planet’s polar regions.

The solar flare as seen by NASA’s Solar Dynamics Observatory on September 10, 2017. (Image: NASA/SDO/Goddard)

On Sunday September 10, 2017,NASA’s Solar Dynamics Observatory recorded an X8.2 class flare. Class X flares are the most intense flares, and the number attached to it denotes its strength, where X2 is twice as intense as X1, and X3 is three times as intense, and so on. M-class flares are a tenth the size of X-class flares and C-class flares are the weakest of the bunch. Both X- and M-class flares can cause brief radio blackouts on Earth, and other mild technological disruptions. Unless it’s part of an unusually strong solar storm—the kind that happens about once every one hundred years—in which case that would be very bad.

The latest flare spurted out from the Sun’s Active Region 2673, which scientists first noticed on August 29. Activity from this region began to intensify on September 4. Over the past week, NASA has catalogued six sizeable flares, including X2.2 and X9.3 flares on September 6, and an X1.3 flare on September 7. The X9.3 flare is the largest flare recorded so far in the current solar cycle—an approximately 11 year-cycle in which the Sun’s activity waxes and wanes. We’re in the ninth year of the current cycle, and we’re heading towards a solar minimum in terms of intensity. Flares like this are rare during this waning phase, but as these latest bursts show, they can still be pretty intense.

This gif shows both the X2.2 and the X9.3 flares that the Sun emitted on Sept. 6, 2017. (Image: NASA/GSFC/SDO)

“Big flares towards the end of sunspot cycles are not unusual, and in fact, that’s fairly standard behavior,” said Scott MacIntosh, director of the High Altitude Observatory at the National Center for Atmospheric research (NCAR), in an interview with Gizmodo. “The trick is to explain why.”

MacIntosh says that when the Sun’s activity gets low, the magnetic systems underlying the spots appear to be in close-contact near the equator. This creates an opportunity for the Sun to produce “hybrid” sunspots—regions which contain magnetic fields that twist like water in the Northern and Southern hemisphere oceans.

“Remember how the rotation of the Earth makes water [spin] in different directions in each hemisphere? The Sun does the same thing for the same reason—the Coriolis force,” said MacIntosh. “Those systems are veryunstable. Typically these types of spots produce the biggest, baddest flares and coronal mass ejections when they emerge through the Sun’s surface.”

But the paradoxical thing, says MacIntosh, is that the periods of very low solar activity are known to have produced the biggest geomagnetic storms in history, and these late-cycle events can persist for a very long time, even though the total number of flares is low. “It’s basically about how the different magnetic systems interact,” he says.

As a result of the most recent solar flares, NOAA’s Space Weather Prediction Center has issued a moderate geomagnetic storm watch for September 13, and a minor geomagnetic storm watch for September 14. This shouldn’t cause too much of a problem on Earth, but as NASA Solar Scientist Mitzi Adams explained to Gizmodo, we need to be concerned about flares and coronal mass ejections, since we’re now so reliant on technology that can be impacted by these events.

“The Space Weather Prediction Center (SWPC) shows an image from SOHO’s coronagraph with ‘speckles.’ The speckles are energetic charged particles interacting with the camera, which do degrade the camera over time,” said Adams. “These events also cause radio blackouts, corrosion in pipelines, and ground-induced currents that can damage transformers. Through monitoring and basic research, the goal is to understand what the Sun does and is likely to do so that we can prepare satellites, power grids, and even astronauts.”

The particles that speckle our cameras, says Adams, arrive about an hour after traveling about 93,000,000 miles per hour (150,000,000 km/h) from the Sun to the Earth. But the bulk of the particles take a couple of days to reach our planet, giving us some time to prepare.

Correction: A previous version of this post incorrectly identified the Space Weather Prediction Center as being run by NASA. Sorry about the error.

[NASA/Goddard, Space Weather Prediction Center]

An Earth-Sized Space Shield to Protect Us From Solar Storms Is Less Crazy Than It Sounds


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An Earth-Sized Space Shield to Protect Us From Solar Storms Is Less Crazy Than It Sounds

 https://gizmodo.com/an-earth-sized-space-shield-to-protect-us-from-solar-st-1819057677
Image: NASA

Every 100 years or so, our Sun gives off a great big belch that sends an intense wave of charged particles towards Earth. This wasn’t a problem in the past, but our high-tech civilization is now disturbingly vulnerable to these solar storms. A new study quantifies the economic risks posed by these extreme solar storms, while also proposing a super-futuristic solution to the problem: an Earth-sized shield built in outer space.

The term “solar storm” is used to identify the various nasties the Sun can hurl our way, including x-rays, charged particles, and magnetized plasma. In 1859, a series of powerful coronal mass ejections (CMEs) hit our planet head on, disrupting telegraph stations and causing widespread communication outages.If we were to be hit by an equally powerful solar storm today, it would knock out satellites and electrical grids, disrupting global communications, transportation, and supply chains. Total worldwide losses could reach up to $10 trillion, with recovery taking many years.

We have no idea when the next Carrington-like event will occur, but a 2012 paper proposed a 10 percent chance of one happening in the next decade. Indeed, like an earthquake-prone city built above a pair of conflicting fault lines, it’s only a matter of time before our planet is hit by the next Big One. And to make matters worse, we’re becoming increasingly vulnerable to these events owing to steady technological advances.

A new paper by Manasvi Lingam and Avi Loeb from Harvard-Smithsonian Center for Astrophysics is the first to consider the economic impacts of a sizeable solar storm in the future, when our reliance on technology is far greater than it is today. In addition, the authors propose a strategy to mitigate the effects—and they’re not thinking small. Lingam and Loeb say we should construct a massive shield in space, and that the costs would be far lower than having to deal with the aftermath of a solar storm. The researchers go on to argue that advanced extraterrestrial civilizations have likely done this already, and that we should search for these shields as a way to detect aliens.

The new paper is currently being considered for publication in The Astrophysical Journal Letters.

To help them with their economic model, Lingam and Loeb factored in two important assumptions. First, the longer the duration between powerful solar flares, the more powerful they will be. Second, our civilization will experience exponential growths in technology and Gross Domestic Product (GDP) in the coming decades.

“We predict that within about 150 years, there will be an event that causes damage comparable to the current United States’ GDP of approximately $20 trillion, and the damage will increase exponentially at later times until technological development will saturate [i.e. when technological development finally starts to slow down and be globally distributed],” Loeb told Gizmodo. “Such a forecast was never attempted before.”

With these potentially catastrophic losses in mind, Lingam and Loeb turn to potential solutions. Unsurprisingly, the proposed mitigation strategies aren’t subtle, but of the three solutions considered, only one was deemed viable by the researchers.

“[Some] shielding solutions rely on placing physical object(s) between the Earth and the Sun. This would not work since the mass will be tremendous and can block the sunlight,” Lingam told Gizmodo. “Similarly, one can use electrical fields instead of magnetic fields. However, the problem is that the electrical field will repel positive particles but will attract the negative particles. Hence, we suggest that magnetic shielding is relatively the most viable.”

An illustration of the proposed magnetic deflector (not drawn to scale). (Image: Lingam and Loeb, 2017)

This Earth-sized “magnetic deflector” would be placed at the Lagrange L1 point between the Earth and the Sun at a distance of about 205,000 miles (329,000 km) from our planet’s surface. It would act as a current loop, and deflect the sun’s harmful particles back into space. The researchers say the required amount of deflective force is relatively small, and that we already have much of the technology required to make this possible. The big challenge, they say, will be to scale it up to its superstructural size.

“The related engineering project could take a few decades to construct in space,” said Loeb. “The cost for lifting the needed infrastructure to space (weighing 100,000 tons) will likely [cost around] hundreds of billions of dollars, much less than the expected [solar storm] damage over a century.”

The authors say the price of the magnetic deflector is comparable to the total cost of the International Space Station, and that it’s about three to four orders of magnitude cheaper than the current global GDP—or the economic damage from a flare in about a hundred years time. But that’s if we use material from Earth. It may make more economic sense to build the superstructure using materials extracted from the asteroid belt.

“I agree completely that the risk and economic damage from solar eruptions is too large and should be mitigated—imagine the current situation in Puerto Rico but worldwide,” said Anders Sandberg, a research fellow who works out of Oxford University’s Future of Humanity Institute, a part of the Oxford Martin School, in an interview with Gizmodo. “However, I was not convinced by their economic model at all… there seemed to be far too many arbitrary assumptions. In particular, the vulnerability of the world economy can both increase and decrease, for example, if we build a more modularized and resilient power grid.”

As for the prescribed solution—the magnetic deflector—Sandberg says it’s basically a “backup magnetic field,” and, as a megascale engineering problem, “not too daunting.”

“Just an Earth-sized loop of one-centimeter thick copper wire weighing 100,000 tons and presumably powered by a 1 TW solar power farm [should do it],” said Sandberg, who wasn’t involved in the new study. “It does not seem to be that far away from what we can currently do (except for that solar power farm). But it is not going to be as cheap as they calculated since the big cost is likely the energy system and installation, not the wiring. Now, reducing solar eruption risk is worth a lot, but I doubt this on its own will be cost-effective. As part of space industrialization, yes (especially since it is extra vulnerable), but otherwise I suspect smarter power-grids give more safety per dollar.”

Sandberg’s concerns notwithstanding, a gigantic magnetic deflector makes a lot of sense, particularly for a technological civilization considerably more advanced than our own. And in fact, it’s conceivable that some hypothetical alien civilizations have done this already. It would be wise, argue Loeb and Lingam, for us to search for signs of these shields as a way to detect extraterrestrial civilizations. We could do it using the transit method, the exoplanet detection technique that aims to observe such objects when they eclipse their host stars from our vantage point here on Earth.

“The [resulting] imprint could be changes in the brightness of the host star due to occultation (similar behavior to Tabby’s star) if the structure is big enough,” said Loeb. “The situation could be similar to Dyson spheres, but instead of harvesting the energy of the star [as a Dyson sphere hypothetically would], the purpose of the infrastructure is to protect a technological civilization on a planet from the flares of its host star.”

Andrew Siemion, Director of Berkeley SETI Research Center and Principal Investigator at the Breakthrough Listen program, says our deep dependence on electronics has created a particular susceptibility to stellar flare events, and that Loeb and Lingam have the right idea.

“Indeed we might some day attempt to mitigate these events using large scale ‘astroengineering,’ and under certain circumstances these structures could be detectable at interstellar distances,” Siemion told Gizmodo. “This is a fascinating thought experiment, and is exactly the kind of thinking that SETI scientists must continually engage in as we seek to identify technologies in the widest variety of incarnations.”

The authors of the new study are right to raise the prospect of solar storms as an important public issue. When it comes to mitigating existential or catastrophic natural hazards, our attention tends to be focused on asteroid impacts. Trouble is, solar storms happen with far greater frequency, so it would be a good idea to start thinking about mitigation strategies pretty much immediately. A solar deflector may be a sensible solution (eventually), but as Sandberg points out, it would also be smart to build a technological infrastructure that’s immune to the Sun’s harmful flares. The more angles we use to approach this problem, the better.

[A pre-print of this paper is available at arXiv]

How to build a Dyson sphere in five (relatively) easy steps


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How to build a Dyson sphere in five (relatively) easy steps

We are closer to being able to build a Dyson Sphere than we think. By enveloping the sun in a massive sphere of artificial habitats and solar panels, a Dyson Sphere would provide us with more energy than we would ever know what to do with while dramatically increasing our living space. Implausible you say? Something for our distant descendants to consider? Think again. We could conceivably get going on the project in about 25 to 50 years, with completion of the first phase requiring only a few decades.

Given that our resources here on Earth are starting to dwindle, and combined with the problem of increasing demand for more energy and living space, this would seem to a good long-term plan for our species.

Now, before I tell you how we could do such a thing, it’s worth doing a quick review of what is meant by a “Dyson sphere”.

Dyson Spheres, Swarms, and Bubbles

The Dyson sphere, also referred to as a Dyson shell, is the brainchild of the physicist and astronomer Freeman Dyson. In 1959 he put out a two page paper titled, “Search for Artificial Stellar Sources of Infrared Radiation” in which he described a way for an advanced civilization to utilize all of the energy radiated by their sun. This hypothetical megastructure, as envisaged by Dyson, would be the size of a planetary orbit and consist of a shell of solar collectors (or habitats) around the star. With this model, all (or at least a significant amount) of the energy would hit a receiving surface where it can be used. He speculated that such structures would be the logical consequence of the long-term survival and escalating energy needs of a technological civilization.

Needless to say, the amount of energy that could be extracted in this way is mind-boggling. According to Anders Sandberg, an expert on exploratory engineering, a Dyson sphere in our solar system with a radius of one AU would have a surface area of at least 2.72×10^17 km2, which is around 600 million times the surface area of the Earth. The sun has an energy output of around 4×10^26 W, of which most would be available to do useful work.

I should note at this point that a Dyson sphere may not be what you think it is. Science fiction often portrays it as a solid shell enclosing the sun, usually with an inhabitable surface on the inside. Such a structure would be a physical impossibility as the tensile strength would be far too immense and it would be susceptible to severe drift.

Dyson’s original proposal simply assumed there would be enough solar collectors around the sun to absorb the starlight, not that they would form a continuous shell. Rather, the shell would consist of independently orbiting structures, around a million kilometres thick and containing more than 1×10^5 objects. Consequently, a “Dyson sphere” could consist of solar captors in any number of possible configurations. In a Dyson swarm model, there would be a myriad of solar panels situated in various orbits. It’s generally agreed that this would be the best approach. Another plausible idea is that of the Dyson bubble in which solar sails, as well as solar panels, would be put into place and balanced by gravity and the solar wind pushing against it.

For the purposes of this discussion, I’m going to propose that we build a Dyson swarm (sometimes referred to as a type I Dyson sphere), which will consist of a large number of independent constructs orbiting in a dense formation around the sun. The advantage of this approach is that such a structure could be built incrementally. Moreover, various forms of wireless energy transfer could be used to transmit energy between its components and the Earth.

Megascale construction

So, how would we go about the largest construction project ever undertaken by humanity?

As noted, a Dyson swarm can be built gradually. And in fact, this is the approach we should take. The primary challenges of this approach, however, is that we will need advanced materials (which we still do not possess, but will likely develop in the coming decades thanks to nanotechnology), and autonomous robots to mine for materials and build the panels in space.

Now, assuming that we will be able to overcome these challenges in the next half-decade or so-which is not too implausible- how could we start the construction of a Dyson sphere?

Oxford University physicist Stuart Armstrong has devised a rather ingenious and startling simple plan for doing so-one which he claims is almost within humanity’s collective skill-set. Armstrong’s plan sees five primary stages of construction, which when used in a cyclical manner, would result in increasingly efficient, and even exponentially growing, construction rates such that the entire project could be completed within a few decades.

Broken down into five basic steps, the construction cycle looks like this:

1. Get energy
2. Mine Mercury
3. Get materials into orbit
4. Make solar collectors
5. Extract energy

The idea is to build the entire swarm in iterative steps and not all at once. We would only need to build a small section of the Dyson sphere to provide the energy requirements for the rest of the project. Thus, construction efficiency will increase over time as the project progresses. “We could do it now,” says Armstrong. It’s just a question of materials and automation.

And yes, you read that right: we’re going to have to mine materials from Mercury. Actually, we’ll likely have to take the whole planet apart. The Dyson sphere will require a horrendous amount of material-so much so, in fact, that, should we want to completely envelope the sun, we are going to have to disassemble not just Mercury, but Venus, some of the outer planets, and any nearby asteroids as well.

Why Mercury first? According to Armstrong, we need a convenient source of material close to the sun. Moreover, it has a good base of elements for our needs. Mercury has a mass of 3.3×10^23 kg. Slightly more than half of its mass is usable, namely iron and oxygen, which can be used as a reasonable construction material (i.e. hematite). So, the useful mass of Mercury is 1.7×10^23 kg, which, once mined, transported into space, and converted into solar captors, would create a total surface area of 245g/m2. This Phase 1 swarm would be placed in orbit around Mercury and would provide a reasonable amount of reflective surface area for energy extraction.

There are five fundamental, but fairly conservative, assumptions that Armstrong relies upon for this plan. First, he assumes it will take ten years to process and position the extracted material. Second, that 51.9% of Mercury’s mass is in fact usable. Third, that there will be 1/10 efficiency for moving material off planet (with the remainder going into breaking chemical bonds and mining). Fourth, that we’ll get about 1/3 efficiency out of the solar panels. And lastly, that the first section of the Dyson sphere will consist of a modest 1 km2 surface area.

And here’s where it gets interesting: Construction efficiency will at this point start to improve at an exponential rate.

Consequently, Armstrong suggests that we break the project down into what he calls “ten year surges.” Basically, we should take the first ten years to build the first array, and then, using the energy from that initial swarm, fuel the rest of the project. Using such a schema, Mercury could be completely dismantled in about four ten-year cycles. In other words, we could create a Dyson swarm that consists of more than half of the mass of Mercury in forty years! And should we wish to continue, if would only take about a year to disassemble Venus.

And assuming we go all the way and envelope the entire sun, we would eventually have access to 3.8×10^26 Watts of energy.

Dysonian existence

Once Phase 1 construction is complete (i.e. the Mercury phase), we could use this energy for other purposes, like megascale supercomputing, building mass drivers for interstellar exploration, or for continuing to build and maintain the Dyson sphere.

Interestingly, Armstrong would seem to suggest that this might be enough energy to serve us. But other thinkers, like Sandberg, suggest that we should keep going. But in order for us to do so we would have to deconstruct more planets. Sandberg contends that both the inner and outer solar system contains enough usable material for various forms of Dyson spheres with a complete 1 AU radius (which would be around 42 kg/m2 of the sphere). Clearly, should we wish to truly attain Kardashev II status, this would be the way to go.

And why go all the way? Well, it’s very possible that our appetite for computational power will become quite insatiable. It’s hard to predict what a post-Singularity or post-biological civilization would do with so much computation power. Some ideas include ancestor simulations, or even creating virtual universes within universes. In addition, an advanced civilization may simply want to create as many positive individual experiences as possible (a kind of utilitarian imperative). Regardless, digital existence appears to be in our future, so computation will eventually become our most valuable and sought after resource.

That said, whether we build a small array or one that envelopes the entire sun, it seems clear that the idea of constructing a Dyson sphere should no longer be relegated to science fiction or our dreams of the deep future. Like other speculative projects, like the space elevator or terraforming Mars, we should seriously consider putting this alongside our other near-term plans for space exploration and work.

And given the progressively worsening condition of Earth and our ever-growing demand for living space and resources, we may have no other choice.

This post originally appeared on Sentient Developments.

Top illustration by Oh Jihoon.

Why We Should Look For Alien Megastructures Around Pulsars


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Why We Should Look For Alien Megastructures Around Pulsars

Image: NASA

Some day in the far future, it’s possible our descendants will kick it up a notch and wrap the entire Sun in a massive solar-collecting shell known as a Dyson Sphere. It’s also possible that some advanced alien civilizations have already gone this route, which is why some SETI folks are on the lookout for these hypothetical objects. But a new study proposes that aliens are more likely to build megastructures around pulsars than stars—and importantly, we should be able to detect these objects from Earth using current technology.

When Freeman Dyson came up with his mind-altering idea back in 1959, he wasn’t imagining an energy solution for future humans. Instead, he was thinking about aliens, and the kinds of things we should be looking for to finally prove they actually exist. Today, the search for alien megastructures is referred to as Dysonian SETI, and we haven’t found anything yet (though we’ve had some false signals).

Conceptually, Dyson’s hypothetical sphere makes a lot of sense, particularly for advanced civilizations with a huge appetite for energy. By constructing a thin spherical shell around its sun, a civilization could capture oodles of solar energy that would otherwise bleed uselessly into space.

Graduating to a Type 2 Kardashev civilization sounds all good and well, but constructing—and maintaining—a megastructure of this scale won’t be easy. The shell itself would be located around one AU from the host star (that’s the average distance the Earth orbits the Sun). Consequently, the amount of material required to build a Dyson Sphere would be literally astronomical, andsome experts have speculated that, if we were to ever build a Dyson Sphere, we’d have to dismantle Mercury, and possibly even Venus and the Asteroid Belt. Unfortunately, this could disrupt the delicate gravitational balance within the Solar System, leading to downstream consequences like planet-on-planet collisions. Other challenges exist as well, such as maintaining the shape and position of the shell, and repairing the endless damage wrought to the structure by incoming asteroids and comets.

It’s for these and other reasons that Zaza Osmanov, an astronomer from the Free University of Tbilisi, believes that Dyson Spheres aren’t the way to go. Ina paper he published last year in the International Journal of Astrobiology, Osmanov said that Dyson Spheres are “unrealistically massive and cannot be considered seriously,” and that aliens (or future humans for that matter) are more likely to build Dyson Rings—a stripped down version of a Dyson Sphere. What’s more, he said aliens weren’t likely to construct these solar-collecting rings around stars, but pulsars instead. Now, in a follow-up study to this first paper, Osmanov is arguing that we should be able to detect these structures from Earth.

Osmanov’s idea is actually kind of awesome. Pulsars are rapidly rotating neutron stars or white dwarfs that emit a concentrated beam of electromagnetic radiation. From our vantage point on Earth, we can only see pulsars if their beams are pointing directly at us. Pulsars have short and highly regular rotational periods, which is why they blink. (Fun fact: When the first pulsar was discovered in 1967, astronomers thought they had stumbled upon an alien intelligence—they even named it LGM, which stands for Little Green Men.)

According to Osmanov, advanced alien civilizations are likely to exploit this high-power celestial phenomenon. Extending Dyson’s concept to pulsars, he says a ring of solar panels could be constructed around a slowly-rotating pulsar (spinning around about once every half second, so not that slow) at a distance of around nine million miles, or roughly one-third of the distance between Mercury and our Sun. He estimates that the Dyson Ring would be exposed to temperatures of around 117 degrees C (242 degrees F), which would make the object visible to observers on Earth in the infrared (IR) band.

Consequently, and assuming these objects actually exist, Osmanov says we could detect these Dyson rings from Earth using existing telescopes, such as the Very Large Telescope Interferometer (VLTI), the Wide-field Infrared Survey Explorer (WISE), and in future, the James Webb Space Telescope. “The search of infrared rings is quite promising for distances up to [652 lightyears], where one will be able to monitor potentially 64 [known] pulsars by using the IR instruments,” he writes in the study. “Observation of distant pulsars [up to 3,262 lightyears]… will significantly increase the total number of potential objects to [around] 1,600, but at this moment the UV instruments cannot provide such a level of sensitivity.”

Artist’s impression of a Dyson Ring. (Image: Wikimedia)

“This is pretty cool,” Milan M. Ćirković, an astronomer and astrobiologist at the Astronomical Observatory of Belgrade, told Gizmodo. “I do agree that they are detectable in principle… and this study is worthy of attention just for that. Whether [the construction of Dyson Rings around pulsars] is likely to happen depends on too many issues, including perhaps the most intriguing one, namely what other [kinds]… of megastructures could we expect from a Type 2 civilization that has capacity and will to build pulsar rings.”

Anders Sandberg, a senior research fellow at Oxford University’s Future of Humanity Institute, likes Osmanov’s idea, but he’s still a big believer in good ol’ fashion Dyson spheres.

“For stars, a Dyson swarm [a variation of the Dyson sphere] can pick up most of the energy because the star shines evenly in all directions,” Sandberg told Gizmodo. “For a pulsar there is not much light, but indeed a big electromagnetic field with a lot of directionality one can capture and use using much smaller rings. Osmanov is right in that this requires less material, but it is not clear why this would matter much. One could build a thin yet energy-collecting Dyson swarm out of a few large asteroids in the solar system. If you have self-replicating [robotic] technology, scale is not a problem, and if you lack it you will struggle to build even a Dyson ring.”

Sandberg also says that Dysonian superstructures don’t have to be located in a star system’s habitable zone, and that we should look for alien megastructures in other regions of space as well.

“But it makes sense to look at pulsars to see if there is something there: They are rare enough to stand out—and it has been suggested that SETI should look near them for this very reason—and they might have accessible energy sources useful in ways normal Dyson swarms aren’t,” he said.

So what the hell are we waiting for? Time for someone with access to an IR-scanning telescope to hone in on on this rather small set of candidate objects. Who knows, the celestial phenomena we once thought were signs of alien intelligence may in fact be home to ET—and possibly a glimpse into our very own future.

[International Journal of Astrobiology]

Hubble Catches a Glimpse of the Most Distant Active Comet Ever Seen George Dvorsky Friday 1:20pmFiled to: INCOMING! 19.9K 23 8 Image: NASA, ESA, and D. Jewitt (UCLA) Behold C/2017 K2 (PANSTARRS), or “K2″ for short. At a jaw-dropping distance of 1.5 billion miles (2.4 billion km) from the Sun, it’s the farthest active inbound comet ever documented by astronomers. K2 was discovered in May 2017 by the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) in Hawaii, but this is our first opportunity—thanks to the Hubble Space Telescope—to see the comet in any sort of meaningful detail. To the surprise of astronomers, the inbound comet has entered into its active mode, even though it’s currently located somewhere between the orbits of Uranus and Saturn. At this distance, the ambient temperature is a chilly minus 400 degrees Fahrenheit, and the Sun’s intensity is a mere 1/225th of what it is at Earth. Yet the comet is already starting to shed its icy coating. According to the press release, Hubble’s observations “represent the earliest signs of activity ever seen from a comet entering the solar system’s planetary zone for the first time.” Image: NASA, ESA, and A. Feild (STScI) K2 is currently travelling towards the Sun, and it’s now close enough such that it has developed a cloud of dust and gas around it, a feature known as a coma, one that currently measures about 80,000 miles (128,000 km) wide. “K2 is so far from the Sun and so cold, we know for sure that the activity—all the fuzzy stuff making it look like a comet—is not produced, as in other comets, by the evaporation of water ice,” explained David Jewitt, a research at the University of California, Los Angeles, who’s studying the comet, in the press release. “Instead, we think the activity is due to the sublimation [a solid changing directly into a gas] of super-volatiles as K2 makes its maiden entry into the solar system’s planetary zone. That’s why it’s special. This comet is so far away and so incredibly cold that water ice there is frozen like a rock.” Jewitt said that the particular mixture of volatile gases observed, including oxygen, nitrogen, carbon dioxide, and carbon monoxide, make K2 “the most primitive comet we’ve seen.” K2’s inbound journey has been a long one, originating within the Oort Cloud—a spherical shell nearly a light-year in diameter that contains billions of comets. These rocky balls of ice, dust, and gas date back to the formation of the Solar System some 4.6 billion years ago. The comet has not developed a tail—at least not yet. K2’s closest approach will happen on July 14, 2022, at which time it will be just outside the orbit of Mars at a distance of 2.677 AU (250 million miles) from the Sun. No word yet on whether K2 will be visible to the naked eye when it swings by in five years time. [Hubble]


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Hubble Catches a Glimpse of the Most Distant Active Comet Ever Seen

Image: NASA, ESA, and D. Jewitt (UCLA)

Behold C/2017 K2 (PANSTARRS), or “K2″ for short. At a jaw-dropping distance of 1.5 billion miles (2.4 billion km) from the Sun, it’s the farthest active inbound comet ever documented by astronomers.

K2 was discovered in May 2017 by the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) in Hawaii, but this is our first opportunity—thanks to the Hubble Space Telescope—to see the comet in any sort of meaningful detail.

To the surprise of astronomers, the inbound comet has entered into its active mode, even though it’s currently located somewhere between the orbits of Uranus and Saturn. At this distance, the ambient temperature is a chilly minus 400 degrees Fahrenheit, and the Sun’s intensity is a mere 1/225th of what it is at Earth. Yet the comet is already starting to shed its icy coating. According to the press release, Hubble’s observations “represent the earliest signs of activity ever seen from a comet entering the solar system’s planetary zone for the first time.”

Image: NASA, ESA, and A. Feild (STScI)

K2 is currently travelling towards the Sun, and it’s now close enough such that it has developed a cloud of dust and gas around it, a feature known as a coma, one that currently measures about 80,000 miles (128,000 km) wide.

“K2 is so far from the Sun and so cold, we know for sure that the activity—all the fuzzy stuff making it look like a comet—is not produced, as in other comets, by the evaporation of water ice,” explained David Jewitt, a research at the University of California, Los Angeles, who’s studying the comet, in the press release. “Instead, we think the activity is due to the sublimation [a solid changing directly into a gas] of super-volatiles as K2 makes its maiden entry into the solar system’s planetary zone. That’s why it’s special. This comet is so far away and so incredibly cold that water ice there is frozen like a rock.”

Jewitt said that the particular mixture of volatile gases observed, including oxygen, nitrogen, carbon dioxide, and carbon monoxide, make K2 “the most primitive comet we’ve seen.”

K2’s inbound journey has been a long one, originating within the Oort Cloud—a spherical shell nearly a light-year in diameter that contains billions of comets. These rocky balls of ice, dust, and gas date back to the formation of the Solar System some 4.6 billion years ago.

The comet has not developed a tail—at least not yet. K2’s closest approach will happen on July 14, 2022, at which time it will be just outside the orbit of Mars at a distance of 2.677 AU (250 million miles) from the Sun. No word yet on whether K2 will be visible to the naked eye when it swings by in five years time.

[Hubble]