Artist rendering of the system 30 Ari with its exoplanet and four stars. Excerpt from techtimes.com By Dianne Depra Researchers seeking to study the complexities of exoplanets with multiple stars have found a new system with four. Cal...
Tag: astrophysics (page 2 of 3)
The background image in this composite shows the Hubble Space Telescope image of the region known as the Hubble Deep Field South. The boxes show distant galaxies that were invisible to Hubble.Excerpt from huffingtonpost.comAlong with Earthrise ...
“The ingredients for life are plentiful, and we now know that habitable environments are plentiful,” says Professor Charley Lineweaver, a down-under astrophysicist.
Lineweaver and PhD student Tim Bovaird worked this out by reviewing the data on exoplanets discovered by the famed Kepler planet-hunter space scope. Kepler naturally tends to find exoplanets which orbit close to their parent suns, as it detects them by the changes in light they make by passing in front of the star. As a result, most Kepler exoplanets are too hot for liquid water to be present on their surfaces, which makes them comparatively boring.
Good planets in the "goldilocks" zone which is neither too hot nor too cold are much harder to detect with Kepler, which is a shame as these are the planets which might be home to alien life - or alternatively, home one day to transplanted Earth life including human colonists, once we've cracked that pesky interstellar travel problem.
However there exists a thing called the Titius-Bode relation - aka Bode's Law - which can be used, once you know where some inner planets are, to predict where ones further out will be found.
Assuming Bode's Law works for other suns as it does here, and inputting the positions of known inner exoplanets found by Kepler, Lineweaver and Bovaird found that on average a star in our galaxy has two planets in its potentially-habitable zone.
That doesn't mean there are habitable or inhabited planets at every star, of course. Even here in our solar system, apparently lifeless (and not very habitable) Mars is in the habitable zone.
Even so, there are an awful lot of planets in the galaxy, so some at least ought to have life on them, and in some cases this life ought to have achieved a detectable civilisation. Prof Lineweaver admits that the total lack of any sign of this is a bit of a puzzler.
"The universe is not teeming with aliens with human-like intelligence that can build radio telescopes and space ships," admits the prof. "Otherwise we would have seen or heard from them.
“It could be that there is some other bottleneck for the emergence of life that we haven’t worked out yet. Or intelligent civilisations evolve, but then self-destruct.”
Of course, humans - some approximations of which have been around for some hundreds of thousands of years, perhaps - have only had civilisation of any kind in any location for a few thousand of those years. Our civilisation has only risen to levels where it could be detectable across interstellar distances very recently.
There may be many planets out there inhabited by intelligent aliens who either have no civilisation at all, or only primitive civilisation. There may be quite a few who have reached or passed the stage of emitting noticeable amounts of radio or other telltale signs, but those emissions either will not reach us for hundreds of thousands of years - or went past long ago.
It would seem reasonable to suspect that there are multitudes of worlds out there where life exists in plenty but has never become intelligent, as Earth life was for millions of years before early humans began using tools really quite recently.
But the numbers are still such that the apparent absence of star-travelling aliens could make you worry about the viability of technological civilisation if, like Professor Lineweaver, you learn your astrophysics out of textbooks and lectures (and publish your research, as we see here, in hefty boffinry journals like the Monthly Notices of the Royal Astronomical Society).
But if movies, speculofictive novels and TV have taught us anything here on the Reg alien life desk, it is that in fact the galaxy is swarming with star-travelling aliens (and/or humans taken secretly from planet Earth for mysterious purposes in the past, or perhaps humans from somewhere else etc). The reason we don't know about them is that they don't want us to.
Excerpt from utahpeoplespost.com
By Frank Smith
Scientists from the Harvard-Smithsonian Center for Astrophysics (CfA) recently reported that they identified eight new exoplanets orbiting their host stars in the so-called “Goldilocks” zone. Researchers also said that many of these objects have an increased chance to be Earth-like, rocky planets with a high potential of hosting alien life.
The “Goldilocks zone,” or the habitable zone, is a patch of space around a Sun-like star that allow planets orbiting within it hold liquid water on their surface if they also have the necessary atmospheric pressure for it. Most Goldilocks planets are Earth-sized so scientists hope that one of them may host life, even microbial forms of life.
The new discovery of the exoplanets doubles the number of known planets located in the habitable zone of their host stars. Scientists explain that the habitable zone implies that the planets within it receive as much solar as our planet does. Too much radiation and heat would boil the water on their surface and even blow away their atmosphere. Too little radiation would lead to a small icy world.
The authors of the discovery also reported that two of the newly found planets are the most akin to Earth than any other known exoplanets to this date. The two planets were named Kepler-438b and Kepler-442b after the space telescope that had discovered them.
Kepler-438b is located 470 light-years from our planet, while Kepler-442b stands in the constellation Lyra at a 1,120 light-year-long distance away from Earth. Kepler-442b is also the most remote exoplanet of the eight.
The two planets have also an extremely short orbit because they are very close to their host stars. On Kepler-438b, which has a diameter only 12 percent than the Earth’s, a year lasts only 35 days, while on Kepler-442b, which is nearly one third larger than our planet, a year passes every 112 days.
Scientists estimate that Kepler-438b has a 70 percent increased chance of having a rocky core, while Kepler-442b has only a 60 percent chance.
However, the two planets being in the habitable zone of their host stars is not a certain fact. For instance, astronomers estimate that Kepler-438b has only a 70 percent chance of being located in the Goldilocks zone, while Kepler-442b has a 97 percent chance of being a Goldilocks planet.
We don’t know for sure whether any of the planets in our sample are truly habitable. All we can say is that they’re promising candidates,”David Kipping of the CfA and co-author of the discovery said.
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In this infrared image, stellar winds from a giant star cause interstellar dust to form ripples. There's a whole lot of dust—which contains oxygen, carbon, iron, nickel, and all the other elements—out there, and eventually some of it finds its way into our bodies. Photograph by NASA, JPL-Caltech |
We have stardust in us as old as the universe—and some that may have landed on Earth just a hundred years ago.
Excerpt from National Geographic
By Simon Worrall
Astrophysics and medical pathology don't, at first sight, appear to have much in common. What do sunspots have to do with liver spots? How does the big bang connect with cystic fibrosis?
Book jacket courtesy of schrijver+schrijver
Astrophysicist Karel Schrijver, a senior fellow at the Lockheed Martin Solar and Astrophysics Laboratory, and his wife, Iris Schrijver, professor of pathology at Stanford University, have joined the dots in a new book, Living With the Stars: How the Human Body Is Connected to the Life Cycles of the Earth, the Planets, and the Stars.
Talking from their home in Palo Alto, California, they explain how everything in us originated in cosmic explosions billions of years ago, how our bodies are in a constant state of decay and regeneration, and why singer Joni Mitchell was right.
"We are stardust," Joni Mitchell famously sang in "Woodstock." It turns out she was right, wasn't she?
Iris: Was she ever! Everything we are and everything in the universe and on Earth originated from stardust, and it continually floats through us even today. It directly connects us to the universe, rebuilding our bodies over and again over our lifetimes.
That was one of the biggest surprises for us in this book. We really didn't realize how impermanent we are, and that our bodies are made of remnants of stars and massive explosions in the galaxies. All the material in our bodies originates with that residual stardust, and it finds its way into plants, and from there into the nutrients that we need for everything we do—think, move, grow. And every few years the bulk of our bodies are newly created.
Can you give me some examples of how stardust formed us?
Karel: When the universe started, there was just hydrogen and a little helium and very little of anything else. Helium is not in our bodies. Hydrogen is, but that's not the bulk of our weight. Stars are like nuclear reactors. They take a fuel and convert it to something else. Hydrogen is formed into helium, and helium is built into carbon, nitrogen and oxygen, iron and sulfur—everything we're made of. When stars get to the end of their lives, they swell up and fall together again, throwing off their outer layers. If a star is heavy enough, it will explode in a supernova.
So most of the material that we're made of comes out of dying stars, or stars that died in explosions. And those stellar explosions continue. We have stuff in us as old as the universe, and then some stuff that landed here maybe only a hundred years ago. And all of that mixes in our bodies.
Stars are being born and stars are dying in this infrared snapshot of the heavens. You and I—we come from stardust.
Photograph by NASA, JPL-Caltech, University of Wisconsin
Your book yokes together two seemingly different sciences: astrophysics and human biology. Describe your individual professions and how you combined them to create this book.
Iris: I'm a physician specializing in genetics and pathology. Pathologists are the medical specialists who diagnose diseases and their causes. We also study the responses of the body to such diseases and to the treatment given. I do this at the level of the DNA, so at Stanford University I direct the diagnostic molecular pathology laboratory. I also provide patient care by diagnosing inherited diseases and also cancers, and by following therapy responses in those cancer patients based on changes that we can detect in their DNA.
Our book is based on many conversations that Karel and I had, in which we talked to each other about topics from our daily professional lives. Those areas are quite different. I look at the code of life. He's an astrophysicist who explores the secrets of the stars. But the more we followed up on our questions to each other, the more we discovered our fields have a lot more connections than we thought possible.
Karel: I'm an astrophysicist. Astrophysicists specialize in all sorts of things, from dark matter to galaxies. I picked stars because they fascinated me. But no matter how many stars you look at, you can never see any detail. They're all tiny points in the sky.
So I turned my attention to the sun, which is the only star where we can see what happens all over the universe. At some point NASA asked me to lead a summer school for beginning researchers to try to create materials to understand the things that go all the way from the sun to the Earth. I learned so many things about these connections I started to tell Iris. At some point I thought: This could be an interesting story, and it dawned on us that together we go all the way, as she said, from the smallest to the largest. And we have great fun doing this together.
We tend to think of our bodies changing only slowly once we reach adulthood. So I was fascinated to discover that, in fact, we're changing all the time and constantly rebuilding ourselves. Talk about our skin.
Iris: Most people don't even think of the skin as an organ. In fact, it's our largest one. To keep alive, our cells have to divide and grow. We're aware of that because we see children grow. But cells also age and eventually die, and the skin is a great example of this.
It's something that touches everything around us. It's also very exposed to damage and needs to constantly regenerate. It weighs around eight pounds [four kilograms] and is composed of several layers. These layers age quickly, especially the outer layer, the dermis. The cells there are replaced roughly every month or two. That means we lose approximately 30,000 cells every minute throughout our lives, and our entire external surface layer is replaced about once a year.
Very little of our physical bodies lasts for more than a few years. Of course, that's at odds with how we perceive ourselves when we look into the mirror. But we're not fixed at all. We're more like a pattern or a process. And it was the transience of the body and the flow of energy and matter needed to counter that impermanence that led us to explore our interconnectedness with the universe.
You have a fascinating discussion about age. Describe how different parts of the human body age at different speeds.
Iris: Every tissue recreates itself, but they all do it at a different rate. We know through carbon dating that cells in the adult human body have an average age of seven to ten years. That's far less than the age of the average human, but there are remarkable differences in these ages. Some cells literally exist for a few days. Those are the ones that touch the surface. The skin is a great example, but also the surfaces of our lungs and the digestive tract. The muscle cells of the heart, an organ we consider to be very permanent, typically continue to function for more than a decade. But if you look at a person who's 50, about half of their heart cells will have been replaced.
Our bodies are never static. We're dynamic beings, and we have to be dynamic to remain alive. This is not just true for us humans. It's true for all living things.
A figure that jumped out at me is that 40,000 tons of cosmic dust fall on Earth every year. Where does it all come from? How does it affect us?
Karel: When the solar system formed, it started to freeze gas into ice and dust particles. They would grow and grow by colliding. Eventually gravity pulled them together to form planets. The planets are like big vacuum cleaners, sucking in everything around them. But they didn't complete the job. There's still an awful lot of dust floating around.
When we say that as an astronomer, we can mean anything from objects weighing micrograms, which you wouldn't even see unless you had a microscope, to things that weigh many tons, like comets. All that stuff is still there, being pulled around by the gravity of the planets and the sun. The Earth can't avoid running into this debris, so that dust falls onto the Earth all the time and has from the very beginning. It's why the planet was made in the first place.
Nowadays, you don't even notice it. But eventually all that stuff, which contains oxygen and carbon, iron, nickel, and all the other elements, finds its way into our bodies.
When a really big piece of dust, like a giant comet or asteroid, falls onto the Earth, you get a massive explosion, which is one of the reasons we believe the dinosaurs became extinct some 70 million years ago. That fortunately doesn't happen very often. But things fall out of the sky all the time. [Laughs]
Many everyday commodities we use also began their existence in outer space. Tell us about salt.
Karel: Whatever you mention, its history began in outer space. Take salt. What we usually mean by salt is kitchen salt. It has two chemicals, sodium and chloride. Where did they come from? They were formed inside stars that exploded billions of years ago and at some point found their way onto the Earth. Stellar explosions are still going on today in the galaxy, so some of the chlorine we're eating in salt was made only recently.
You study pathology, Iris. Is physical malfunction part of the cosmic order?
Iris: Absolutely. There are healthy processes, such as growth, for which we need cell division. Then there are processes when things go wrong. We age because we lose the balance between cell deaths and regeneration. That's what we see in the mirror when we age over time. That's also what we see when diseases develop, such as cancers. Cancer is basically a mistake in the DNA, and because of that the whole system can be derailed. Aging and cancer are actually very similar processes. They both originate in the fact that there's a loss of balance between regeneration and cell loss.
Cystic fibrosis is an inherited genetic disease. You inherit an error in the DNA. Because of that, certain tissues do not have the capability to provide their normal function to the body. My work is focused on finding changes in DNA in different populations so we can understand better what kinds of mutations are the basis of that disease. Based on that, we can provide prognosis. There are now drugs that target specific mutations, as well as transplants, so these patients can have a much better life span than was possible 10 or 20 years ago.
How has writing this book changed your view of life—and your view of each other?
Karel: There are two things that struck me, one that I had no idea about. The first is what Iris described earlier—the impermanence of our bodies. As a physicist, I thought the body was built early on, that it would grow and be stable. Iris showed me, over a long series of dinner discussions, that that's not the way it works. Cells die and rebuild all the time. We're literally not what were a few years ago, and not just because of the way we think. Everything around us does this. Nature is not outside us. We are nature.
As far as our relationship is concerned, I always had a great deal of respect for Iris, and physicians in general. They have to know things that I couldn't possibly remember. And that's only grown with time.
Iris: Physics was not my favorite topic in high school. [Laughs] Through Karel and our conversations, I feel that the universe and the world around us has become much more accessible. That was our goal with the book as well. We wanted it to be accessible and understandable for anyone with a high school education. It was a challenge to write it that way, to explain things to each other in lay terms. But it has certainly changed my view of life. It's increased my sense of wonder and appreciation of life.
In terms of Karel's profession and our relationship, it has inevitably deepened. We understand much better what the other person is doing in the sandboxes we respectively play in. [Laughs]
Excerpt from spacedaily.com For nearly half a century, theoretical physicists have made a series of discoveries that certain constants in fundamental physics seem extraordinarily fine-tuned to allow for the emergence of a life-enabling universe.Thi...
Excerpt from theregister.co.uk
New research suggests planets similar to Earth are much more common across the galaxy than previously thought.
And the boffins behind this revelation have also come up with a simple chemical recipe for creating habitable worlds suitable for use by advanced super-powered intelligences and/or deities etc.
Ms Dressing bases this assertion on data from the HARPS-North (High-Accuracy Radial velocity Planet Searcher, Northern) instrument on the 3.6-metre Telescopio Nazionale Galileo in the Canary Islands. This is designed to accurately measure the masses of small, Earthish-sized worlds. Once you have mass and volume, as any fule kno, you have density and thus a fair notion of what a given alien world is made of - and this tells you whether it can be much like Earth.
So chuffed are the Harvard boffins with this discovery that they've come up with a handy "recipe" for cooking up a world with Earth-esque life on it, thus:
1 cup magnesiumBlend well in a large bowl, shape into a round ball with your hands and place it neatly in a habitable zone area around a young star. Do not over mix. Heat until mixture becomes a white hot glowing ball. Bake for a few million years. Cool until color changes from white to yellow to red and a golden-brown crust forms. It should not give off light anymore. Season with a dash of water and organic compounds. It will shrink a bit as steam escapes and clouds and oceans form. Stand back and wait a few more million years to see what happens.
1 cup silicon
2 cups iron
2 cups oxygen
½ teaspoon aluminum
½ teaspoon nickel
½ teaspoon calcium
¼ teaspoon sulfur
dash of water delivered by asteroids
If you are lucky, a thin frosting of life may appear on the surface of your new world.
Excerpt from bbc.comAstronomers have proved that they can accurately tell the age of a star from how fast it is spinning. We know that stars slow down over time, but until recently there was little data to support exact calculations. For ...
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| An artist's conception shows the size of super-Earth 55 Cancri e compared to Earth. A ground-based telescope in Spain was able to identify 55 Cancri e, which suggests that telescopes on the ground help in the search for habitable planets around other stars. |
Excerpt from csmonitor.com
A telescope on the Canary Islands has spotted a planet twice the size of Earth as it passed in front of a star, the first time a planet in this category has been detected by a ground-based telescope.
Finding Earthlike planets beyond our solar system has largely been the work of space-based telescopes, but new observations from a remote island suggest that could change.The Nordic Optical Telescope on La Palma — one of the Canary Islands off the west coast of Africa — observed 55 Cancri e, a planet twice the size of Earth, as it passed in front of its parent star and caused a dip in the star's brightness, according to a new study. This is the first time a planet in this "super-Earth" size category orbiting a sunlike star has been observed by a ground-based telescope using this detection method, the researchers say.
First identified in 2004 by a space-based telescope, 55 Cancri e has a diameter of about 16,000 miles (26,000 kilometers) — about twice that of Earth. The alien world is eight times as massive as Earth, making it a so-called super-Earth, a planet more massive than Earth but significantly smaller than gas giants like Neptune and Uranus. While not habitable, the planet's size and position around a sunlike star make it similar to planets that might support life, researchers say.
"We expect these surveys to find so many nearby terrestrial worlds that space telescopes simply won't be able to follow up on all of them. Future ground-based instrumentation will be key, and this study shows it can be done," Mercedes Lopez-Morales, co-author of the new research and a researcher at the Harvard-Smithsonian Center for Astrophysics (CfA), said in a statement.
Five exoplanets orbit the star 55 Cancri, which is located 40 light-years from Earth and is visible to the naked eye. The closest-orbiting of those five is 55 Cancri e, which completes one lap around the star every 18 hours. When the planet passes between Earth and the parent star, 55 Cancri appears to dim by 1/2000th (or 0.05 percent) for almost 2 hours, researchers said.
Daytime temperatures on 55 Cancri e likely reach higher than 3,100 degrees Fahrenheit (1,700 degrees Celsius) — hot enough to melt metal and much too hot to support life. But scientists involved with the study say this approach could help characterize the atmosphere of more hospitable Earthlike or super-Earth planets.
After its initial detection, 55 Cancri e also became the first super-Earth seen by NASA's Spitzer Space Telescope, using light directly from the planet. Thus, it has now served twice as a litmus test for super-Earth detection methods.
In addition to the wealth of planets identified by NASA's Kepler Space Telescope, the space agency's Transiting Exoplanet Survey Satellite (TESS) mission, scheduled for launch in 2017, is expected to "discover thousands of exoplanets in orbit around the brightest stars in the sky," according to the TESS website. The European Space Agency's Planetary Transits and Oscillations of stars (PLATO) mission, planned for launch in 2024, will also search for a large number of exoplanets.
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| NASA's GALEX ultraviolet satellite identified nearby starburst galaxies that made good analogs of early galaxies. Follow-up images taken by the Hubble Space Telescope revealed that the compact galaxy J0921 allowed a large fraction of its radiation to escape. |
Excerpt from csmonitor.com
By Nola Taylor Redd, SPACE.com Contributor
A compact galaxy some 3 billion light-years away is shedding light, shedding light on how stars formed during when our universe was young.
A densely packed star-forming galaxy is reproducing the events that brought light to the early universe.
The nearby compact galaxy named J0921+4509, which is rapidly producing stars, has many of the characteristics that would have been required to light up the early universe. Located approximately 3 billion light-years from the Milky Way, the star-forming regions of the tightly bound galaxy are surrounded by dense clouds of gas. Holes in the gas allow radiation to leak out, mimicking events that would have broken through the darkness that followed the birth of the universe.J0921+4509 produces approximately 50 solar-masses' worth of stars each year, more than 33 times the number of stars created by the Milky Way every year. While most stars in other locations remain swathed in the gas that forms them, trapping radiation inside, J0921 has holes that allow the radiation to escape, much as it might have in the early universe.
Leaking galaxies
Only a few hundred thousand years after the Big Bang, hydrogen gas in the universe cooled and became neutral as protons and electrons paired up. Any radiation emitted was quickly absorbed, rendering the period unobservable, or "dark," to astronomers. By the end of the first billion years, radiation known as Lyman continuum had reionized the hydrogen, scattering electrons and making the universe visible once again.
Events from the dark ages of the universe, including its reionization, cannot be directly studied. Instead, astronomers must search for similar processes in objects they can examine today, such as those found in the starburst galaxy J0921. The name "starburst galaxies" comes from the unusually high rate of stellar production in such locations...
A starburst studied
A handful of galaxies in the early universe are leaking radiation. Scientists are able to study these galaxies from the universe’s youth because of the correlation between the distance light travels and the time it takes to make the journey. Essentially, looking at objects in the distant universe is like looking back in time; astronomers see the light as it was when it left the object.
Two other nearby galaxies are suspected to be leaking radiation, but each has only a tenth as much radiation as J0921.
"This is the direct evidence of how the galactic feedback via winds can lead to conditions that allow Lyman continuum to escape," Borthakur said. "This tells us about the physics of star formation and its feedback in the epoch of reionization, and solves the decades-old mystery of how Lyman continuum photons can escape through the cold cloud cocoon enveloping star-forming regions."
The new research is published this week in the journal Science.
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| The 10-meter South Pole Telescope and the BICEP (Background Imaging of Cosmic Extragalactic Polarization) Telescope at Amundsen-Scott South Pole Station, which detected evidence of gravitational waves, is seen against the night sky with the Milky Way in this National Science Foundation picture taken in August 2008. |
By Ben P. Stein, Inside Science
Harvard researchers rocked the science community last March with an apparent discovery of gravitational ripples that gave credence to cosmic inflation theory – a finding that met as much skepticism as enthusiasm. Now, further analysis raises more doubts.
"Extraordinary claims require extraordinary evidence." This phrase, popularized by the late Carl Sagan, kept going through my head on March 17, the day that researchers involved with BICEP2, a telescope in Antarctica, made a big announcement at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.
The researchers reported that BICEP2 detected gravitational waves from the first moments after the big bang, a feat, which if confirmed, would open up a new field of study and would surely be recognized in a future Nobel Prize.
Gravitational waves are ripples in space and time. They're created when any object with mass accelerates. However, they're extremely weak, making them very hard to detect directly. Even for the most massive and cataclysmic events, such as the collision of two black holes, their effects, observed from Earth, are very hard to detect.
If you're looking for a detectable gravitational wave signal, what bigger event can there be than cosmic inflation? According to inflation theory, the universe multiplied its size by as much as 10 trillion trillion trillion times in the first fractions of a second after the big bang. Inflation would have generated lots of gravitational waves. In turn, gravitational waves can subtly change the properties of light that they pass through. Specifically, they can slightly affect the polarization of light, the direction in which light's electric fields vibrate. The universe's rapid expansion during inflation would have amplified the waves' imprint on the early light in the universe.
The state-of-the-art BICEP2 experiment, which uses super-sensitive superconducting sensors, could detect tiny changes in polarization in the cosmic microwave background, the very first light released in the universe, which is still reaching us today. The BICEP2 researchers reported a very high polarization signal, known as B-mode polarization after its characteristics, in the cosmic microwave background, which they interpreted as a strong gravitational wave signal in the early universe.
Detecting this polarization signal was a striking result, announced in a series of scientific talks and a press conference shortly after a preprint of the paper was posted online. Notice these last two points: announced at a press conference, and a preprint posted online. A preprint is a written paper that has not been formally reviewed by independent peers or published in a scientific journal.
Nonetheless, scientists and reporters alike reported excitement over the results. If true, they would provide the greatest experimental support yet of cosmic inflation, and the first direct detection of gravitational waves. Previously, gravitational waves have been detected indirectly, such as in observations of pairs of stars falling towards each other: they were losing energy in the form of gravitational waves.
On the day of the BICEP2 announcement, and for many days afterward, people were largely accepting the results as correct and already jumping to the implications of the BICEP2 results for what appeared to be a new era of gravitational-wave cosmology.
In writing my story for Inside Science News Service, I was fortunate to get an early voice of skepticism from David Spergel, a theoretical cosmologist at Princeton University in New Jersey. He commented:
"Given the importance of this result, my starting point is to be skeptical. Most importantly, there are several independent experimental groups that will test this result in the next year."
Spergel explained that the new gravitational wave measurements did not appear to agree with those of previous experiments, known as WMAP and Planck, unless the simplest models of inflation were replaced by more complicated ones. On the first day and week of coverage, I became very disappointed with the many commentators who disregarded or underemphasized that the earlier measurements from instruments on WMAP and Planck, which had been reported and covered for years.
Sure enough, in the weeks that followed, other researchers pointed out that the signal that BICEP2 detected may have been attributable to the polarization of light caused by dust in our galaxy. The BICEP2 team certainly knew that dust could also polarize light in a similar way to gravitational waves, but they used a model, based on the data that was available from the Planck satellite, that, the other researchers pointed out, may have underestimated the amount of dust in the part of the sky they were studying.
The BICEP2 paper underwent peer review and was published in Physical Review Letters. As a result of the peer-review process, the researchers made revisions, including removing the model that contained the lower estimates of dust based on the earlier Planck data, and thereby reducing the certainty with which they could state that they accounted for signals from interstellar dust.
During the summer, the BICEP2 and Planck collaborations agreed to work together to analyze their data, to help determine if gravitational waves had really been detected.
This week, the Planck team issued a preprint, based on an analysis of much additional data, showing a comprehensive map of dust in the sky. According to their analysis, the signal in the part of sky that BICEP2 analyzed could be completely attributable to dust and not to gravitational waves.
But, the story is not over. For starters, keep in mind the new preprint, like all newly posted publications, still needs to undergo formal peer review.
And the latest data do not completely rule out the possibility that the BICEP2 group detected a gravitational wave signal. If the evidence holds up at all, it would likely be a weaker signal, after accounting for the dust. Or, the gravitational-wave signal may completely turn to dust.
It may be possible to detect primordial gravitational waves in a different, less dusty part of the sky, or with new measurements by BICEP2, Planck or the many other experiments that are looking for them. Just as the first reported detections of exoplanets turned out to be false, perhaps this is a prelude to an actual detection of gravitational waves.
"You cannot ignore dust," he quotes from Planck scientist Charles Lawrence of NASA’s Jet Propulsion Laboratory in Pasadena, California.
The biggest lesson, to me, is that no one should rush to make announcements and pronouncements, whether big or small, even in the face of intense competition and the alluring prospects of launching a new field of study and winning a Nobel Prize.
Scientists, and the rest of the public, should follow the time-tested scientific practice of subjecting claims to sufficient levels of scrutiny, and waiting for other groups to validate results, before making bold statements. At the very least, there have been major caveats and qualifiers in announcing new data with potentially huge implications.
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Stardust got in their eyes.
In the spring a group of astronomers who go by the name of Bicep announced that they had detected ripples in the sky, gravitational waves that were the opening notes of the Big Bang. The finding was heralded as potentially the greatest discovery of the admittedly young century, but some outside astronomers said the group had underestimated the extent to which interstellar dust could have contaminated the results — a possibility that the group conceded in its official report in June.
Now a long-awaited report by astronomers using data from the European Space Agency’s Planck satellite has confirmed that criticism, concluding that there was enough dust in Bicep’s view of the sky to produce the swirly patterns without recourse to primordial gravitational waves.
“We show that even in the faintest dust-emitting regions there are no ‘clean’ windows in the sky,” the Planck collaboration, led by Jean-Loup Puget of the Astrophysical Institute in Paris, wrote in a paper submitted to the journal Astronomy & Astrophysics and posted online Monday.
As a result, cosmologists like the Bicep crew cannot ignore dust in their calculations. “However,” said Jonathan Aumont, another of the Planck authors, also from the Paris institute, “our work does not imply that they did not measure at all a cosmological signal.
Moreover, due to the very different observation techniques and signal processing in the Bicep2 and Planck experiments, we cannot say how much of the signal they measured is due to dust” and how much to gravitational waves.
So this is not the end of the story, both the Planck scientists and the Bicep group agree. But the original euphoria that the secrets of inflation and quantum gravity might be at hand has evaporated. Planck and Bicep are now collaborating on a detailed comparison of their results.
John M. Kovac of the Harvard-Smithsonian Center for Astrophysics, lead author of the Bicep paper, said the new report confirmed in greater detail the trend suggested by the first Planck papers in the spring, which indicated there is more dust even in the cleanest parts of the galaxy than anyone had thought.
Raphael Flauger of the Institute for Advanced Study in Princeton, N. J., who first raised the issue of dust in the Bicep report, said it confirmed what he had thought. “It doesn’t leave a lot of wiggle room,” he wrote in an email, “and it seems clear that at least the majority of the signal is caused by dust.”
The gravitational waves may exist, although they would be weaker than the Bicep analysis indicated, causing theorists to reshuffle their ideas. As Richard Bond, an early universe expert at the University of Toronto and a Planck team member, put it: “Planck showed that dust could possibly be the entire Bicep2 signal, but Planck alone cannot decide. We have to do this in combination with Bicep2.”
The joint comparison and Planck’s own polarization maps are due at the end of the year.
If true, Bicep’s detection of gravitational waves would confirm a theory that the universe began with a violent outward antigravitational swoosh known as inflation, the mainspring of Big Bang theorizing for the last three decades.
The disagreement over the Bicep finding will not mean the end of inflation theory; it just means it will be harder for cosmologists to find out how it worked. The Bicep group and an alphabet soup of competitors are soldiering on with new telescopes and experiments aimed at peeling away the secrets of the sky.
Michael S. Turner, a cosmologist at the University of Chicago, said: “This is going to be a long march, but the goal of probing the earliest moments of the universe makes it well worth the effort. Dust is the bane of the existence of astrophysicists — and cosmologists. It is everywhere, and yet our understanding of it is very poor.”
Others are less optimistic. Paul J. Steinhardt of Princeton University, a critic of the Bicep paper — and of inflation theory — said in an email that the Bicep paper should be retracted, “and we should return to good scientific practice.”
The Bicep observations are the deepest look yet into a thin haze of microwaves, known as cosmic background radiation, left over from end of the Big Bang, when the cosmos was about 380,000 years old.
According to theory, the onset of inflation, less than a trillionth of a second after time began, should have left ripples in space-time known as gravitational waves. They would manifest as corkscrew patterns in the direction of polarization of the cosmic microwaves.
The Bicep group — its name is an acronym for Background Imaging of Cosmic Extragalactic Polarization — is led by Dr. Kovac; Jamie Bock of Caltech; Clement Pryke of the University of Minnesota; and Chao-Lin Kuo of Stanford. They have deployed a series of radio telescopes at the South Pole in search of the swirl pattern. Their most recent, Bicep2, detected a signal in the sweet spot for some of the most popular models of inflation, leading to a splashy news conference and a summer of controversy and gossip.
As the critics pointed out, things besides quantum ripples from the beginning of time could produce those swirls, including light from interstellar dust polarized by magnetic fields in space.
Planck, launched in 2008 to survey the cosmic microwave sky, can distinguish the characteristic signature of dust by comparing the sky brightness in several radio frequencies, as well as measuring its direction of polarization. Bicep2, in contrast, looked at only one frequency, 150 gigahertz.
The Bicep astronomers asked for Planck data on their patch of sky, but it was not available until now because of suspected instrument problems, Dr. Aumont said. So they extrapolated from existing data to conclude that there was little dust interfering with their observations.
The new Planck report has knocked the pins out from under that. But there are still large uncertainties that leave room for primordial gravitational waves at some level. For example, the Planck team had to extrapolate some of its own measurements.
As the Planck report says, “This result emphasizes the need for a dedicated joint Planck-Bicep2 analysis.”
The group hopes this analysis will include data from the latest Bicep telescope, called the Keck Array, which has been gathering data for several months. In an interview this summer, Dr. Kovac said, “It’s been a funny year to be in the spotlight like this.” He said the group stood behind its work, even if the ultimate interpretation of the measurements is up for grabs.
Acknowledging that dust would not be as sexy a discovery as ripples from inflation, Dr. Kovac said, “It’s really important as an experimentalist that you can divorce yourself from an investment in what the answer is.”
He went on: “One thing that would distress me bitterly is if a major mistake in the measurement or of the analysis would come to light. The most pressing question is, what are the dust contributions to the signal?”
Stay tuned.
Lyman Page, an astrophysicist at Princeton, said the episode illustrated the messy progress of science.
“Taking a step back,” he said by email, “it is amazing that a precise measurement of the cosmos can be made, discussed in fullness, and refuted by another measurement in such a short amount of time. It is testament to a healthy field.”
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