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  • richardmitnick 7:33 pm on March 3, 2015 Permalink | Reply
    Tags: , , , Frank Drake, , space.com   

    From Space.com: “The Father of SETI: Q&A with Astronomer Frank Drake” 

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    SPACE.com

    February 26, 2015
    Leonard David

    Arecibo Observatory

    Detecting signals from intelligent aliens is a lifelong quest of noted astronomer Frank Drake. He conducted the first modern search for extraterrestrial intelligence (SETI) experiment in 1960. More than five decades later, the hunt remains front-and-center for the scientist.

    5
    Frank Drake

    Drake also devised a thought experiment in 1961 to identify specific factors believed to play a role in the development of civilizations in our galaxy. This experiment took the form of an equation that researchers have used to estimate the possible number of alien civilizations — the famous Drake Equation.

    The Drake equation is:

    N = R*. fp. ne. fl. fi. fc. L

    where:

    N = the number of civilizations in our galaxy with which radio-communication might be possible (i.e. which are on our current past light cone);

    and

    R* = the average rate of star formation in our galaxy
    fp = the fraction of those stars that have planets
    ne = the average number of planets that can potentially support life per star that has planets
    fl = the fraction of planets that could support life that actually develop life at some point
    fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations)
    fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
    L = the length of time for which such civilizations release detectable signals into space

    Drake constructed the “Arecibo Message” of 1974 — the first interstellar message transmitted via radio waves from Earth for the benefit of any extraterrestrial civilization that may be listening.

    The message consists of seven parts that encode the following (from the top down):[4]

    The numbers one (1) to ten (10)
    The atomic numbers of the elements hydrogen, carbon, nitrogen, oxygen, and phosphorus, which make up deoxyribonucleic acid (DNA)
    The formulas for the sugars and bases in the nucleotides of DNA
    The number of nucleotides in DNA, and a graphic of the double helix structure of DNA
    A graphic figure of a human, the dimension (physical height) of an average man, and the human population of Earth
    A graphic of the Solar System indicating which of the planets the message is coming from
    A graphic of the Arecibo radio telescope and the dimension (the physical diameter) of the transmitting antenna dish

    3
    This is the message with color added to highlight its separate parts. The actual binary transmission carried no color information.

    Space.com caught up with Drake to discuss the current state of SETI during an exclusive interview at the NASA Innovative Advanced Concepts (NIAC) 2015 symposium, which was held here from Jan. 27 to Jan. 29.

    Drake serves on the NASA NIAC External Council and is chairman emeritus of the SETI Institute in Mountain View, Calif. and director of the Carl Sagan Center for the Study of Life in the Universe.

    Space.com: What’s your view today concerning the status of SETI?

    Frank Drake: The situation with SETI is not good. The enterprise is falling apart for lack of funding. While NASA talks about “Are we alone?” as a number one question, they are putting zero money into searching for intelligent life. There’s a big disconnect there.

    We’re on the precipice. The other thing is that there are actually negative events on the horizon that are being considered.

    Space.com: And those are?

    Drake: There are two instruments, really the powerful ones for answering the “are we alone” question … the Arecibo telescope[above] and the Green Bank Telescope [GBT].

    NRAO GBT
    GBT

    They are the world’s two largest radio telescopes, and both of them are in jeopardy. There are movements afoot to close them down … dismantle them. They are both under the National Science Foundation and they are desperate to cut down the amount of money they are putting into them. And their choice is to just shut them down or to find some arrangement where somebody else steps in and provides funding.

    So this is the worst moment for SETI. And if they really pull the rug out from under the Green Bank Telescope and Arecibo … it’s suicide.

    Space.com: What happens if they close those down?

    Drake: We’re all then sitting in our living rooms and watching science fiction movies.

    Space.com: How about the international scene?

    Drake: The international scene has gone down too because all the relevant countries are cash-strapped also.

    There is a major effort in China, a 500-meter [1,640 feet] aperture spherical radio telescope. The entire reflector is under computer control with actuators. They change the shape of the reflector depending on what direction they are trying to look. The technology is very complicated and challenging. The Russians tried it and it never worked right. But … there are serious resources there.

    Space.com: Why isn’t SETI lively and bouncing along fine given all the detections?

    Drake: You would think. All those planetary detections are the greatest motivator to do SETI that we ever had. But it hasn’t had any impact, at least yet.

    Space.com: How do you reconcile the fact that exoplanet discoveries are on the upswing, yet mum’s the word from ET?

    Drake: People say that all the time … saying that you’ve been searching for years and now you’ve searched thousands of stars and found nothing. Why don’t you just give up … isn’t that the sensible thing?

    There’s a good answer to all that. Use the well-know equation and put in the parameters as we know them. A reasonable lifetime of civilizations is like 10,000 years, which is actually much more than we can justify with our own experience. It works out one in every 10 million stars will have a detectable signal. That’s the actual number. That means, to have a good chance to succeed, you have to look at a million stars at least — and not for 10 minutes — for at least days because the signal may vary in intensity. We haven’t come close to doing that. We just haven’t searched enough.

    Space.com: What are we learning about habitable zones?

    Drake: Actually the case is very much stronger for a huge abundance of life. The story seems to be that almost every star has a planetary system … and also the definition of “habitable zone” has expanded. In our system, it used to be that only Mars and Earth were potentially habitable. Now we’ve got an ocean on Europa … Titan.

    The habitable zone goes out. A habitable zone is not governed just by how far you are from the star, but what your atmosphere is. If you’ve got a lot of atmosphere, you’ve got a greenhouse effect. And that means the planet can be much farther out and be habitable.

    6
    “Radio waving” to extraterrestrials. Outward bound broadcasting from Earth has announced humanity’s technological status to other starfolk, if they are out there listening.
    Credit: Abstruse Goose

    Space.com: What is your view on the debate regarding active SETI — purposely broadcasting signals to extraterrestrials?

    Drake: There is controversy. I’m very against sending, by the way. I think it’s crazy because we’re sending all the time. We have a huge leak rate. It has been going on for years. There is benefit in eavesdropping, and you would have learned everything you can learn through successful SETI searches. There’s all kinds of reasons why sending makes no sense.

    7
    Frank Drake, center, with his colleagues, Optical SETI (OSETI) Principal Investigator Shelley Wright and Rem Stone with the 40-inch Nickel telescope at Lick Observatory in California. Outfitted with the OSETI instrument, the silver rectangular instrument package protrudes from the bottom of the telescope, plus computers, etc.
    Credit: Laurie Hatch Photography

    That reminds me of something else. We have learned, in fact, that gravitational lensing works. If they [aliens] use their star as a gravitational lens, they get this free, gigantic, super-Arecibo free of charge. They are not only picking up our radio signals, but they have been seeing the bonfires of the ancient Egyptians. They can probably tell us more about ourselves than we know … they’ve been watching all these years.

    Space.com: Can you discuss the new optical SETI efforts that you are involved with? You want to search for very brief bursts of optical light possibly sent our way by an extraterrestrial civilization to indicate their presence to us.

    Drake: It’s alive and well. We’ve gotten a couple of people who are actually giving major gifts. There’s no funding problem. There is a new instrument that has been built, and it’s going to be installed at the Lick Observatory [in California] in early March.

    The whole thing is designed to look for laser flashes. The assumption is — and this is where it gets to be tenuous — the extraterrestrials are doing us a favor. It does depend on extraterrestrials helping you by targeting you. These stellar beams are so narrow that you’ve got to know the geometry of the solar system that you’re pointing it at. They want to communicate. They have to be intent on an intentional signal specifically aimed at us. That’s a big order. So there are required actions on the part of the extraterrestrials for this to work. The big plus is that it’s cheap and relatively easy to do.

    See the full article here.

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  • richardmitnick 9:07 pm on February 9, 2015 Permalink | Reply
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    From Space.com: “How We Found the Most Distant Quasar (Yet) Known” 

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    SPACE.com

    February 09, 2015
    Daniel Mortlock, Imperial College London

    1
    False-color image of the field around the quasar ULAS J1120+0641 (the faint yellow source indicated by the cross hairs). Only its color distinguishes the quasar from the other sources, mostly ordinary stars in Earth’s Milky Way galaxy. Credit: The United Kingdom Infrared Telescope [UKIRT]

    UKIRT
    UKIRT interior
    UKIRT

    Just before midnight on Sept. 3, 2010, an astronomical database went live on the Web. The Eighth Data Release of the — take a breath now — United Kingdom Infrared Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS) wasn’t particularly noteworthy in computing terms, but it was of considerable scientific significance: It contained new data on hundreds of millions of astronomical objects, many of them never previously seen.

    The vast majority of these objects were ordinary sunlike stars in Earth’s own Milky Way galaxy, but there was about a 10 percent chance that hidden somewhere in the terabytes of data was a single object more distant than any known. My job was to find it.

    Catching a quasar

    I was in an international team led by my Imperial College colleague Steve Warren, and the particular type of object we were looking for was a quasar. This is the glowing accretion disk of gas that can form around a supermassive black hole at the center of an otherwise ordinary galaxy. The material being pulled into the black hole gets compressed and heated to the point that it easily outshines all the stars in the host galaxy. In many cases, that host galaxy is so faint it is not detected, leaving only the quasar visible.

    The main reason for putting so much effort into finding distant quasars , in particular, is that they are by far the brightest, and hence most revealing, astronomical objects in the early universe. Back in 2010, the most distant quasar known appeared to astronomers as it was when the universe was 900 million years old, just 7 percent of its current age of 13.9 billion years. (The finite speed of light means that larger physical distances translate to greater distances in time, or look-back times.)

    It is remarkable that a disk of glowing gas about the size of our solar system can be seen billions of light years away, but the comparatively small size of quasars also means they appear star-like when viewed from Earth, just unresolved points of light in the night sky. This is one reason that quasars can be so hard to find: In any astronomical image taken through a single-wavelength filter, they are indistinguishable from ordinary stars, which massively outnumber them.

    The secret to finding quasars is looking for their distinctive colors . The most distant quasars are very red in color, being almost invisible at optical wavelengths while appearing bright in the near-infrared. (This is due to a combination of the cosmological expansion — which Doppler-shifts all light to longer wavelengths — and absorption by neutral — i.e., un-ionized — hydrogen atoms present in the early universe.) In contrast, stars like the sun mainly emit optical light, although cooler brown dwarfs (essentially “failed” stars in which hydrogen fusion never got going) are almost as red as the target quasars. So, quasar searches are typically done by comparing images of the same part of the sky taken with different wavelength filters.

    If the UKIDSS data had been perfect, it might have been possible to identify any record-breaking quasars immediately. But all real astronomical data is noisy: The measured colors of the sources in the UKIDSS catalogue (and all other data sets) don’t quite match their true values.

    As a result, in a plot of measured brightness ratios from different filters, stars and brown dwarfs overlap with distant quasars . The traditional approach of identifying all objects with colors like the target objects, which had worked in previous searches at lower distances, would have been hopelessly inefficient with UKIDSS.

    That could easily have been a potentially fatal problem for the project, as there were far too many objects to study more closely through re-observation. What was needed was some way to prioritize the best candidates only on the basis of the data at hand.

    This sort of problem — how best to make use of limited astronomical data — is the subject of the emerging field of astrostatistics (which, the complaints of Microsoft Word 2011 notwithstanding, is spelled without a hyphen).

    Astrostatistics sort the Big Data

    The solution we came up with was to use the statistical technique of Bayesian model comparison to assess each candidate, in turn, by considering which of two hypotheses was more consistent with the data: that a given object is a (cool) star or that the object is a (distant) quasar.

    An additional vital ingredient in the method is Bayes’ theorem, a fundamental mathematical result published posthumously by the Presbyterian minister Thomas Bayes (1701-1761). The theorem demands the inclusion of prior information, rather than just the data at hand. This is often cited as a reason not to use Bayesian methods, because it can often seem that there is no other, prior useful information available. But in our case we actively needed to use the (prior) fact that stars outnumber quasars by many thousands to one. The odds of any object chosen randomly from the UKIDSS database being a distant quasar were correspondingly low, and so most apparently promising candidates would correctly be discarded.

    2
    Measured colors (essentially the ratio of how bright objects appear in different wavelength filters) for objects detected in the United Kingdom Infrared Telescope Infrared Deep Sky Survey that passed researchers’ initial selection criteria (shown by the dashed lines). Even though the sources are broadly consistent with being distant quasars, the vast majority are actually either stars or brown dwarfs in the Milky Way galaxy (the predicted properties of which are shown as the blue curve). The five distant quasars (ULAS J1120+0641 and ULAS J1148+0702, along with the three already known) are indicated in blue, with error bars to illustrate the limited precision of the measurements. The predicted quasar properties are shown as the blue curve, with labels showing how these colors change with look-back time. Credit: Daniel Mortlock

    Another appealing aspect of the Bayesian approach is that it automatically encodes many of the criteria that we had been applying intuitively (and qualitatively) when we had first started the search. Fainter objects had been rejected because the color estimates were less precise; now they were objectively ranked in descending order by the fact that a star, when that faint, could end up having the measured colors of a quasar. We had regarded ambiguous objects with measured colors halfway between the two populations with limited enthusiasm; now they were rejected for being so much more likely to have been “scattered” from the dominant stellar population.

    The result of applying the Bayesian ranking scheme to the UKIDSS data was that an input list of tens of thousands of apparently good candidates was reduced to fewer than 50 objects. Three of those already had been identified as very distant (but not quite record-breaking) quasars by the earlier Sloan Digital Sky Survey (SDSS), an important validation of our approach. Quick follow-up observations to confirm the UKIDSS measurements of the remainder allowed us to discard all but two of the other candidates; we sent the coordinates of the two survivors to the Gemini North Telescope for more precise spectroscopic measurements (in which the light is separated into different wavelengths).

    Gemini North telescope
    Gemini North Interior
    Gemini North

    Ancient quasar revealed

    The first of the two objects, with the perhaps uninspiring name of ULAS J1120+0641, was observed on the night of Nov. 27, 2010, and it was immediately revealed it to be easily the most distant quasar known, bettering the previous record holder by a full hundred million years.

    We had found what we were looking for — and the short time between the initial data release and the confirmation was important, as there were other research groups with access to the same data attempting the same search. (The second object, ULAS J1148+0702, was also confirmed as a quasar, but was in the same distance range as the slightly closer quasars found earlier by SDSS.) In the time since its discovery, the quasar ULAS J1120+0641 has been observed using telescopes all around the planet, and the Hubble Space Telescope in orbit.

    Scientists are still unraveling this quasar’s secrets to this day. Aside from revealing what conditions were like 800 million years after the Big Bang, ULAS J1120+0641 is also the home of the earliest supermassive black hole found to date, a monster with two billion times the mass of the sun that had, in contradiction with most standard theories of black hole formation, somehow coalesced in the cosmologically short time available. And none of this would have been possible without a piece of mathematics done by an 18th century Presbyterian priest.

    See the full article here.

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  • richardmitnick 9:01 am on February 8, 2015 Permalink | Reply
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    From Space.com: “How Would the World Change If We Found Alien Life?” 

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    SPACE.com

    February 06, 2015
    Elizabeth Howell

    1
    If contact with extraterrestrial life is made through radio telescopes, a decipherment process may have to take place to understand the message.
    Credit: NASA

    In 1938, Orson Welles narrated a radio broadcast of “War of the Worlds” as a series of simulated radio bulletins of what was happening in real time as Martians arrived on our home planet. The broadcast is widely remembered for creating public panic, although to what extent is hotly debated today.

    Still, the incident serves as an illustration of what could happen when the first life beyond Earth is discovered. While scientists might be excited by the prospect, introducing the public, politicians and interest groups to the idea could take some time.

    How extraterrestrial life would change our world view is a research interest of Steven Dick, who just completed a term as the Baruch S. Blumberg NASA/Library of Congress Chair of Astrobiology. The chair is jointly sponsored by the NASA Astrobiology Program and the John W. Kluge Center, at the Library of Congress.

    Dick is a former astronomer and historian at the United States Naval Observatory, a past chief historian for NASA, and has published several books concerning the discovery of life beyond Earth. To Dick, even the discovery of microbes would be a profound shift for science.

    “If we found microbes, it would have an effect on science, especially biology, by universalizing biology,” he said. “We only have one case of biology on Earth. It’s all related. It’s all DNA-based. If we found an independent example on Mars or Europa, we have a chance of forming a universal biology.”

    Dick points out that even the possibilities of extraterrestrial fossils could change our viewpoints, such as the ongoing discussion of ALH84001, a Martian meteorite found in Antarctica that erupted into public consciousness in 1996 after a Science article said structures inside of it could be linked to biological activity. The conclusion, which is still debated today, led to congressional hearings.

    2
    Photo of the martian meteorite ALH84001. Dull, dark fusion crust covers about 80% of the sample

    “I’ve done a book about discovery in astronomy, and it’s an extended process,” Dick pointed out. “It’s not like you point your telescope and say, ‘Oh, I made a discovery.’ It’s always an extended process: You have to detect something, you have to interpret it, and it takes a long time to understand it. As for extraterrestrial life, the Mars rock showed it could take an extended period of years to understand it.”

    Mayan decipherments

    In his year at the Library of Congress, Dick spent time searching for historical examples (as well as historical analogies) of how humanity might deal with first contact with an extraterrestrial civilization. History shows that contact with new cultures can go in vastly different directions.

    Hernan Cortes’ treatment of the Aztecs is often cited as an example of how wrong first contact can go. But there were other efforts that were a little more mutually beneficial, although the outcomes were never perfect. Fur traders in Canada in the 1800s worked closely with Native Americans, for example, and the Chinese treasure fleet of the 15th Century successfully brought its home culture far beyond its borders, perhaps even to East Africa.

    Even when both sides were trying hard to make communication work, there were barriers, noted Dick.

    “The Jesuits had contact with Native Americans,” he pointed out. “Certain concepts were difficult, like when they tried to get across the ideas of the soul and immortality.”

    Indirect contact by way of radio communications through the Search for Extraterrestrial Intelligence (SETI), also illustrates the challenges of transmitting information across cultures. There is historical precedence for this, such as when Greek knowledge passed west through Arab translators in the 12th Century. This shows that it is possible for ideas to be revived, even from dead cultures, he said.

    Allen Telescope Array
    SETI’s Institute’s Allen Telescope Array

    SETI@home screensaver
    SETI@home project

    Arecibo Observatory
    Arecibo Observatory. used by SETI@home

    “There will be a decipherment process. It might be more like the Mayan decipherments,” Dick said.

    The ethics of contact

    As Dick came to a greater understanding about the potential cultural impact of extraterrestrial intelligence, he invited other scholars to present their findings along with him. Dick chaired a two-day NASA/Library of Congress Astrobiology Symposium called “Preparing for Discovery,” which was intended to address the impact of finding any kind of life beyond Earth, whether microbial or some kind of intelligent, multicellular life form.

    The symposium participants discussed how to move beyond human-centered views of defining life, how to understand the philosophical and theological problems a discovery would bring, and how to help the public understand the implications of a discovery.

    “There is also the question of what I call astro-ethics,” Dick said. “How do you treat alien life? How do you treat it differently, ranging from microbes to intelligence? So we had a philosopher at our symposium talking about the moral status of non-human organisms, talking in relation to animals on Earth and what their status is in relation to us.”

    Dick plans to collect the lectures in a book for publication next year, but he also spent his time at the library gathering materials for a second book about how discovering life beyond Earth will revolutionize our thinking.

    “It’s very farsighted for NASA to fund a position like this,” Dick added. “They have all their programs in astrobiology, they fund the scientists, but here they fund somebody to think about what the implications might be. It’s a good idea to do this, to foresee what might happen before it occurs.”

    It’s also quite possible that the language we receive across these indirect communications would be foreign to us. Even though mathematics is often cited as a universal language, Dick said there are actually two schools of thought. One theory is that there is, indeed, one kind of mathematics that is based on a Platonic idea, and the other theory is that mathematics is a construction of the culture that you are in.

    See the full article here.

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  • richardmitnick 10:38 am on February 5, 2015 Permalink | Reply
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    From Space.com: “Mystery of the Universe’s Gamma-Ray Glow Solved” 

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    SPACE.com

    February 05, 2015
    Calla Cofield

    1
    Five years of data from the Fermi Gamma-ray Space Telescope paint a picture of the universe in gamma-rays. Scientists with Fermi think the flux of gamma-rays can be explained by known sources.
    Credit: gamma ray sky, gamma ray universe, fermi telescope, blazars, radio galaxies, gamma ray emitters, gamma ray sources, milky way gamma rays

    The steady glow of high-energy gamma-ray light that spreads across the cosmos has puzzled astronomers for decades. One team of researchers thinks it has the best explanation yet for the source of this strange emission.

    After observing the universe with NASA’s Fermi Gamma-ray Space Telescope for six years, scientists with the mission say the majority of the gamma-ray glow they have seen can be explained by objects already known to science. If there are any as-yet unknown sources out there, their contribution to the glow would be very small, scientists say.

    NASA Fermi Telescope
    NASA/Fermi

    “We have a very plausible story. We’re not 100 percent confident that this is the final answer, but it really constrains what other exotic possibilities could be out there,” said Keith Bechtol, a postdoctoral researcher at the University of Chicago and a member of the Fermi collaboration who worked on the analysis.

    4
    Galactic Haze Seen by Planck and Galactic ‘Bubbles’ Seen by Fermi
    Credit: ESA/Planck Collaboration (microwave); NASA/DOE/Fermi LAT/D. Finkbeiner et al. (gamma rays)
    This all-sky image shows the distribution of the galactic haze seen by ESA’s Planck mission at microwave frequencies superimposed over the high-energy sky, as seen by NASA’s Fermi Gamma-ray Space Telescope. Image released February 13, 2012.

    ESA Planck
    ESA/Planck

    5
    W44 Supernova Remnant
    Credit: NASA/DOE/Fermi LAT Collaboration, ROSAT, JPL-Caltech, and NRAO/AUI
    Fermi’s LAT mapped GeV-gamma-ray emission (magenta) from the W44 supernova remnant. The features clearly align with filaments detectable in other wavelengths. This composite merges X-rays (blue) from the Germany-led ROSAT mission, infrared (red) from NASA’s Spitzer Space Telescope, and radio (orange) from the NRAO’s Very Large Array near Socorro, N.M.

    NASA ROSAT satellite
    ROSAT

    NASA Spitzer Telescope
    NASA/Spitzer

    NRAO VLA
    NRAO/VLA

    Fermi: a gamma-ray gumshoe

    NASA’s Fermi Gamma-ray Space Telescope snaps pictures of the entire observable universe — from end to end — in gamma-rays, which are some of the highest-energy photons in nature.

    While that wide view of the universe is useful, it can make it a challenge to pinpoint the exact sources of these gamma-rays. Instead, Fermi sees a diffuse glow coming from the universe. This glow is technically known as the extragalactic gamma ray background, or the EGB. Previous gamma-ray telescopes have also seen this light that fills the background of the cosmos.

    “We’ve known about this gamma-ray background since the late 1960s,” Bechtol said. “It’s a very-long-standing mystery, and each generation of gamma-ray telescopes has given us a little more information.”

    With help from other telescopes, the Fermi telescope can identify where some of this high-energy background light is coming from. There are very energetic galaxies called blazars, for example, that give off a high flux of gamma-rays. The Energetic Gamma Ray Experiment Telescope (EGRET), which preceded Fermi, broke records by detecting some 300 gamma-ray sources. So far, the Fermi telescope has identified more than 3,000 sources.

    NASA Energetic Gamma Ray Telescope

    But 3,000 is only a drop in the ocean of gamma-ray sources in the entire universe, scientists say.

    “We think every galaxy is producing gamma-rays at some level,” Bechtol said. “The vast majority are too faint to be seen individually and instead their collective emission is blurred together.” (Many galaxies radiate high levels of optical light, and can be seen by telescopes like the Hubble. But their gamma-ray emission is too faint to be detected.)

    “It’s frustrating not to know the answer, but the fact that there’s a mystery — I think that’s what attracted a lot of us to this problem,” Bechtol said. “At least for me, I like being on the edge of that discovery space where there’s still blank parts on the map.”

    Cracking the mystery

    The Fermi telescope can’t see most of the objects that radiate gamma-ray light, so the scientists have to try to estimate how many gamma-ray objects are out there.

    In an analysis first made public in September 2014, members of the Fermi collaboration took the known sources of gamma-rays and added them together with models that predicted the frequency and location of unseen sources. The scientists calculated how much gamma-ray light both the detected and modeled sources would produce together.

    This calculated output of gamma rays matches closely with the actual gamma ray-background that Fermi observes — the entire EGB.

    The final estimate shows that roughly 50 percent of the gamma-ray background comes from extremely energetic galaxies known as blazars. Ten to 30 percent of the gamma ray background emanates from star-forming galaxies like the Milky Way, which can collectively contain many smaller gamma-ray sources, like supernovas. Another 20 percent is from radio galaxies, which are blazars, but are pointed away from the Earth, and thus cannot be seen as easily by Fermi.

    “There could definitely be new gamma-ray sources out there,” Bechtol said. “It’s just that their total contribution would have to be relatively small.”

    It’s also possible that dark matter — the mysterious material that makes up 80 percent of all the matter in the universe — is producing gamma-rays, and the Fermi results may help scientists figure out what kind of particle (or particles) make up dark matter.

    Two large uncertainties remain in Fermi’s estimation. First, it is difficult to measure the gamma-ray glow of the universe to begin with, and Bechtol said he and his collaborators put a lot of time into improving that measurement.

    Second, the scientists are making estimates about objects they cannot directly observe, most of which are located beyond the Milky Way galaxy (or extragalactic).

    “When [scientists] first discovered the gamma-ray background, it was largely a mystery as to what created it,” Bechtol said. “And now it seems like everything is fitting together very well. Right now, the simplest explanation involving known astrophysical sources seems to be doing just fine.”

    6
    The Fermi Large Area Telescope has spotted highly energetic ejections of gamma-rays throughout the universe. Scientists with Fermi believe known gamma-ray sources can account for the overall gamma-ray flux in the universe, but they say there is still room for surprises.
    Credit: NASA/DOE/Fermi LAT Collaboration

    Light from back in time

    Fermi’s success at decoding the gamma-ray background had depended largely on its increased sensitivity to gamma-rays and its detection of more gamma-ray sources than previous telescopes. In addition, Fermi scientists have worked to gain a better understanding of how gamma-ray emissions have changed throughout the history of the universe. This is valuable because when Fermi looks at sources of gamma-rays, it is actually looking into the past.

    Light travels at a finite speed — the light from the sun takes 8 minutes to reach Earth, which means humans actually see the sun as it was 8 minutes ago. By the same logic, objects that are billions of light-years away from Earth are seen by Fermi as they were billions of years ago.

    “We’re literally measuring the light output over the history of the universe, and for me, that’s what makes this exciting,” Bechtol said. “We’re seeing all different time periods in the universe at the same time. All of the light from all those different periods is added together to form the gamma ray background.”

    Having a historical perspective makes a big difference for Fermi because the cosmic output of gamma-rays has likely been different at various times throughout the last 13 billion years. For example, the universe has seen periods when the population of blazars exploded and other times when the population growth slowed down. They also need to understand precisely how far away those blazars are, in order to accurately measure how long ago these bright sources burned.

    The Fermi scientists have solved a long-standing puzzle, but Bechtol said there are still other mysteries in the gamma-ray universe. There are other gamma-ray telescopes that can detect even higher-energy gamma-rays than Fermi, and it’s possible that in those energy ranges, there are sources of gamma-rays that scientists don’t know about yet.

    “We think this [result] is converging on the final answer, but history has shown us that, sometimes, there’s more to the story,” Bechtol said. “I certainly think that, as we start to look at higher energies […], there will start to be some surprises.”

    See the full article here.

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  • richardmitnick 5:02 pm on February 2, 2015 Permalink | Reply
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    From Space.com: “Does Humanity’s Destiny Lie in Interstellar Space Travel? (Op-Ed)” 

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    January 27, 2015
    Donald Goldsmith

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    An artist’s interpretation of utilizing a wormhole to travel through space, Thorne kick-started a serious discussion among scientists about whether or wormhole travel is possible. Credit: NASA

    Imagine a time when humans, having spent decades exploring the solar system through landings on Venus and Mars; passages by the largest asteroids; close-up surveys of Jupiter and its giant moons; repeated loops through Saturn’s system of rings and satellites; detailed photography of Uranus, Neptune and Pluto; and even landing on a comet, finally create a coherent plan to travel through interstellar space to reach the nearest stars and their planets.

    That time has almost arrived. Once NASA’s Dawn spacecraft arrives at the asteroid Ceres in March of this year , and the space agency’s New Horizons spacecraft flies by Pluto in July, humans will have completed the solar system exploration described above. They will have done so, of course, by creating complex and highly capable spacecraft that not only secure high-resolution images of the objects they encounter, but also roll across planetary surfaces to measure local conditions in a dozen different ways, including spectroscopic and chemical analysis of the composition and history of each object.

    NASA Dawn Spacescraft
    NASA/Dawn

    NASA New Horizons spacecraft
    NASA/New Horizons

    Will humans ever replace robotic explorers?

    To many of us, the success of our automated spacecraft heralds the long-awaited moments when humans finally land on Mars, Ganymede (Jupiter’s largest moon) or Titan (Saturn’s largest moon), eventually to establish self-sustaining colonies that might provide a continuing opportunity to maintain our existence if our home planet were to become uninhabitable. The interplay between our logical wishes to deepen our knowledge of the solar system and our gut-level desires for personal encounters with new situations — always present though not always acknowledged — has governed humans’ ever-shifting plans to explore our nearby cosmic environment for half a century.

    Just about everyone welcomes new information about the solar system, but what many really — really — want is for humanity to plant its boots on new soil, as Earth-bound explorers have done for many centuries. Lonely humans in space speak directly to our emotions, but pioneering spacecraft far less so. (Even an apparent exception, such as the hero of the movie “WALL-E,” connects with us through its seeming humanity, a fact that won’t surprise anyone who reflects for a moment on how storytelling works.)

    Some facts remain evident: Human exploration of space is dangerous and expensive, requiring the provision of food and water, recycling of wastes, significant amounts of energy to run those systems, protection against harsh radiation and a return journey (or not, depending on volunteers’ propensities). In comparison, automated spacecraft have only modest energy requirements, and can last for decades or more. As time passes, this comparison progressively favors machines, since they (thanks to humans!) become ever more competent, while our bodies evolve at a much slower pace.

    As the brilliant physicist Freeman Dyson explains in the new podcast available at RawScience.tv, “Instruments have gotten enormously … humans are really out of it. If you want to go to space, that’s for fun, not for science … This is not understood by the people in charge [of planning for future exploration missions].”

    To be sure, when we dream of the far future, we can easily envision (thanks, in part, to many science-fiction stories and films) beings that combine today’s human bodies with advanced technology to produce a human-machine hybrid far more capable of long journeys and survival in strange situations than individuals are today.

    Humanity’s destiny in space

    Dyson’s argument in favor of machines counts for little among those who insist — who know — that our destiny lies in the presence of humans, not our mechanistic surrogates, in space. For many of us, this knowledge runs more deeply than argument can reach. A glance at the history of the United States’ space program reminds us of the many times, during the 40-plus years since the last lunar landing, that NASA has attempted to produce a reasonable plan to send humans beyond low-Earth orbit — only to have the expense of such projects, combined with the lack of a clear focus for astronaut activity, lead to their abandonment. Because the manned lunar program basically served as a counterpunch to Soviet efforts in space, once NASA and the United States achieved their initial goal of landing on the moon, they proved unable of following a coherent plan for future space exploration by humans.

    What do these ambitions tell us about the future of interstellar exploration? Even before we consider human versus automated journeys, we should note that any answers to this question begin with a number: 1 million. The stars nearest to the sun lie at distances approximately 1 million times the distance to Mars at its closest approach to Earth. This ratio implies that travel to the stars at speeds our best spacecraft are capable of will take hundreds of thousands of years, and this, in turn, implies that any interstellar exploration will require either a civilization that knows how to plan for the long haul, or the ability to make spacecraft that can travel much faster — perhaps 10,000 times more rapidly — than what we have now. (I’ll save the discussion of “wormholes” like those seen in the movies “Contact” and “Interstellar ” for later.)

    On the fast track, or slow and steady?

    Consider spacecraft that could carry astronauts through space at speeds approaching the speed of light, conferring two great advantages on the crew. Most obviously, the journey requires less time — only a few years to reach the nearest stars, and only a couple of decades to span the distances to the closest thousand stars. In addition, time slows down at near-light velocities — by a factor of 10, for example, for those who travel at 99.5 percent the speed of light. At that velocity, an astronaut who makes an interstellar journey covering 50 light years in each direction would age by only 10 years, but would return to an Earth where everyone has aged by 100 years. (Those who suspect that Einstein’s theory of relativity creates a “twin paradox” — that the traveler and those who stay behind should each see time slow down by a factor of 10 — can find an excellent explanation of the apparent paradox in David Mermin’s book “Space and Time in Special Relativity” (Waveland, 1989).)

    But how can we hope to move through space at close to the speed of light? More than 50 years ago, Dyson — who, even then, created intriguing and controversial ideas at the Institute for Advanced Study in Princeton, New Jersey — proposed that nuclear explosions could accelerate a spacecraft to ever-higher speeds. The “Project Orion” study, directed by Ted Taylor, though largely Dyson’s brainchild, envisioned that a series of nuclear explosions would strike a “pusher plate” attached to the rear of a spacecraft, eventually accelerating the spacecraft to any desired velocity.

    The concept remains theoretically feasible, though one can easily see that the expense would be enormous. As Dyson recalls in the RawScience podcast, by using the power of nuclear explosions, the Orion spacecraft could provide “both fast acceleration and fast travel, which nothing else could do … In principle, the idea was good,” Dyson said, but “it had one fatal flaw: The bombs are highly radioactive … As soon as you had the test-ban treaty … Orion was dead.”

    Even if we manage to accelerate a spacecraft to velocities close to the speed of light (10,000 times faster than our fastest space probes), any spacecraft moving at near-light velocities encounters a significant problem. The same special-relativity rules that allow a traveler to return to Earth much younger than her twin brother who stayed home also imply that collisions with space debris — even tiny dust particles — inevitably pose great dangers. [Photos: Step-by-Step Guide to NASA’s EFT-1 Orion Spacecraft Test Flight ]

    When the spacecraft encounters dust and pebbles, the objects’ near-light velocities, relative to the craft, enormously elevate their effective masses. An impactor’s increase in mass, together with the tremendous collision speeds, call for enormous amounts of shielding to protect anyone inside the spacecraft. Hence, any plans to travel through the Milky Way at near-light speeds must embrace not only a truly massive propulsion system, but also enough shielding to protect the humans inside the craft.

    Thinking in centuries

    Nevertheless, Dyson’s Orion concept remains, in many ways, the gold standard for visions of interstellar travel. In the recent podcast, Dyson noted that the name “Orion” has been passed on to NASA’s most recent spacecraft design not for an interstellar vehicle, but for a far more modest craft to take astronauts to other worlds in the solar system. Dyson also identified the most basic requirement for interstellar spaceflight: a society capable of long-term planning and execution. “If you want to have a program for moving out into the universe, you have to think in centuries, not in decades.”

    That necessity for a long-term vision poses a serious barrier to interstellar journeys in a society that has great difficulty planning for even the next five years.

    If we are prepared to think in centuries, as Dyson recommends, we should ask the key technological question: What prospects exist for interstellar space travel at comparatively low velocities? In the decades since this question first seriously arose, theorists have provided plenty of answers, which build on the success of our current interplanetary space probes. If you want to probe deeply into them, the coordinated websites of the Tau Zero Foundation and Centauri Dreams offer useful information on this topic. And if you want to examine a representative plan for interstellar travel, I recommend the PowerPoint presentation created by Steve Kilston, an astronomer who spent much of his career at Ball Aerospace (and with whom I have been friends since our undergraduate days). Kilston’s “Plausible Path to the Stars” envisions the creation — in approximately 500 years — of a cylindrical spaceship that will carry a million inhabitants, will rotate in order to simulate Earth’s gravity, will travel at 0.2 percent of the speed of light, and could reach the few dozen nearest stars in 10,000 years’ time.

    In other words, Kilston’s “Plausible Path,” like any other low-velocity journey, requires that generations upon generations of spacefarers pass their entire lives short of their goal. Today, this plan would attract few volunteers. But if human society came to feel sure of its long-term viability, so that our time horizon stretched beyond the current limits of (at most) our grandchildren’s lifetimes, the situation would become quite different. Perhaps the wisest aspect of Kilston’s plan lies in its final prelaunch phase: a 100-year cruise through the solar system to demonstrate the full feasibility of the spacecraft and the willingness of its crew to pass their lives in space.

    Thus, a practical, technologically reasonable plan to explore our cosmic environment rests simply upon achieving a society in which a 100-year journey, and a few thousand years of travel time, seem both logical and desirable. To see how far we now stand from this goal, we may merely compare a film based on Kilston’s “Plausible Path” with a movie like “Avatar” or “Interstellar.” In today’s world, almost no one is interested in moving from a situation in which months of spacecraft travel is far too long to one that tolerates multi-thousand-year journeys. Instead, we must hope for a better tomorrow.

    The wormhole option

    If we don’t want to wait, what about taking the “Interstellar” route and using a wormhole to pass near-instantaneously from here to there? Kip Thorne, a physicist at the California Institute of Technology who’s an expert on the subject — and whose screenplay inspired “Interstellar” — has written a book to accompany the film: “The Science of Interstellar” (W.W. Norton and Company, 2014). In the book, Thorne demonstrates that humans cannot rule out wormhole travel, but there is no guarantee that this method actually works, or that it could allow safe conduct through the voids of space.

    Physicists have recently suggested that the Milky Way could contain — or even be! — a giant wormhole. On the other hand, an argument against wormhole travel, or at least against its easy operation, lies in the fact that no creatures of a more advanced civilization appear to be popping out of wormholes in our solar system. A similar argument can be made against time travel, at least in the backward direction, since we have yet to encounter beings from the future who have decided to visit our present.

    To be frank, concepts of interstellar travel have progressed only modestly since Dyson envisioned the Orion project decades ago. Yes, layers of refinement have been added: “Slow” versus “fast” spaceflight has been debated and scored, experience has now given some indications of how well humans can survive long periods in space, and theoretical physics has provided some tantalizing possibilities that might make such journeys much easier than they now appear. But the big picture has not changed: First, we must figure out how to live successfully for the long term on Earth, and then we can go to the stars.

    See the full article here.

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  • richardmitnick 5:08 am on February 2, 2015 Permalink | Reply
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    From Space.com: “Heart Nebula’s Cloudy Core Glows in Amateur Photo” 

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    January 20, 2015
    Nina Sen

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    Astrophotographer Jaspal Chadha took this stunning image of the core of the Heart Nebula over four nights in December 2014 and January 2015.of London
    Credit: Jaspal Chadha

    Stunning cosmic clouds and stars are captured in this image of Melotte 15 showing the newborn star cluster in the core of the so-called Heart nebula.

    Astrophotographer Jaspal Chadha of London took this image over four nights in December 2014 and January 2015. Chadha also took a wide-field image of the same region.

    Melotte 15 lies in the center of emission nebula IC 1805, also called the Heart Nebula due to its Valentine’s-Day related shape. It is located about 7,500 light-years away toward the constellation Cassiopeia. A light-year is the distance light travels in one year, or about 6 trillion miles (10 trillion kilometers). The newborn stars in the core are about 1.5 million years old. Radiation from these massive, hot stars create the imaginative shapes of the cosmic clouds in the image.

    Related images:

    2
    Melotte 15
    Hewholooks

    3
    Heart Nebula
    s58y

    See the full article here.

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  • richardmitnick 10:27 am on January 27, 2015 Permalink | Reply
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    From Space.com: “Eris: The Dwarf Planet That is Pluto’s Twin” 

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    January 27, 2015
    Nola Taylor Redd

    1

    e
    Eris with moon Dysmonia

    In addition to eight full-size planets, the solar system is home to a number of smaller “dwarf planets.” One of these, Eris, is almost the exact same size as the most well-known member of the collection, Pluto.

    Discovery

    When Eris was first discovered in 2005, it was thought to be significantly larger than Pluto. Originally, it was submitted as the tenth planet in the solar system. Ultimately, however, Eris’ discovery was a big reason astronomers demoted Pluto to dwarf planet status in 2006. That decision remains controversial to this day, making Eris’ name fitting.

    “Eris is the Greek goddess of discord and strife,” astronomer Mike Brown, a member of the discovery team, said via NASA. “She stirs up jealousy and envy to cause fighting and anger among men. At the wedding of Peleus and Thetis, all the gods were invited with the exception of Eris, and, enraged at her exclusion, she spitefully caused a quarrel among the goddesses that led to the Trojan War.”

    Like almost all of the known dwarf planets (with the exception of Ceres), Eris lies in the Kuiper Belt that rings the outer solar system. But Eris is even farther-flung than Pluto, circling our star from about three times farther away. It takes 561 years for the distant dwarf planet to make a single trip around the sun, though it rotates once every 25 hours, making the length of its day very similar to a day on Earth.

    k
    Kuiper Belt

    Watching Eris

    Eris’ distance allowed astronomers to make precise measurements when it passed in front of a dim star in 2010, an event known as an occultation. In addition to measuring its size, researchers were also able to conclude its shape, size and mass.

    “It is extraordinary how much we can find out about a small and distant object such as Eris by watching it pass in front of a faint star, using relatively small telescopes,” study lead author Bruno Sicardy, of the Pierre et Marie Curie University and Observatory of Paris, said in a statement. “Five years after the creation of the new class of dwarf planets, we are finally really getting to know one of its founding members.”

    The observations helped scientists determine that Eris’ diameter is 1,445 miles (2,326 kilometers), give or take 7 miles (12 km). That makes Eris’ size even more precisely known than Pluto’s. (Pluto is thought to be between 1,429 and 1,491 miles — or 2,300 to 2,400 km — across.)

    It also means that Pluto and Eris are, for all intents and purposes, the same size, researchers said.

    The researchers concluded that Eris is a spherical body. And, by studying the motion of Eris’ moon Dysnomia, they peg the dwarf planet to be about 27 percent heavier than Pluto, which means it’s considerably denser than Pluto as well.

    “This density means that Eris is probably a large rocky body covered in a relatively thin mantle of ice,” said co-author Emmanuel Jehin, of the Institut d’Astrophysique de I’Université de Liège in Belgium.

    Eris’ surface was also found to be extremely reflective, bouncing back 96 percent of the light that strikes it. That makes Eris one of the most reflective bodies in the solar system, roughly on par with Saturn’s icy moon Enceladus.

    Researchers believe Eris’ surface is probably composed of a nitrogen-rich ice mixed with frozen methane in a layer less than 1 millimeter thick. This ice layer could result from the dwarf planet’s atmosphere condensing as frost onto its surface periodically as it moves away from the sun, they said.

    The observations also allow researchers to make another estimate for the surface temperature of Eris. The side of the dwarf planet facing the sun likely gets no warmer than minus 396 degrees Fahrenheit (minus 238 Celsius), while temperatures on the night side would be even lower, researchers said.
    Dwarf planet’s companion

    Eris is one of the few dwarf planets to boast a moon. Named Dysnomia, after Eris’ daughter the demon goddess of lawlessness, the moon allowed astronomers to make more accurate measures of the planet than would have been otherwise possible, such as measurements of its density.
    Just the facts

    Semi-major axis of its orbit around the sun: 6.3 billion miles (10.2 billion kilometers)
    Perihelion (closest approach to sun): 3.6 billion miles (5.8 billion km)
    Aphelion (farthest distance from sun): 9.1 billion miles (14.6 billion km)
    Orbital period (length of year): 561.37 Earth years
    Orbit eccentricity: 0.434
    Orbit inclination: 46.87
    Sidereal rotation period (length of day): 25.9 hours, or 1.08 Earth days

    See the full article here.

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  • richardmitnick 11:35 am on January 25, 2015 Permalink | Reply
    Tags: , , Birth of the Universe, space.com   

    From Space.com: “Our Expanding Universe: Age, History & Other Facts” 

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    January 13, 2015
    Charles Q. Choi

    1
    Credit: SRON

    The universe was born with the Big Bang as an unimaginably hot, dense point. When the universe was just 10-34 of a second or so old — that is, a hundredth of a billionth of a trillionth of a trillionth of a second in age — it experienced an incredible burst of expansion known as inflation [So, Dr Alan Guth, MIT], in which space itself expanded faster than the speed of light. During this period, the universe doubled in size at least 90 times, going from subatomic-sized to golf-ball-sized almost instantaneously.

    According to NASA, after inflation the growth of the universe continued, but at a slower rate. As space expanded, the universe cooled and matter formed. One second after the Big Bang, the universe was filled with neutrons, protons, electrons, anti-electrons, photons and neutrinos.

    During the first three minutes of the universe, the light elements were born during a process known as Big Bang nucleosynthesis. Temperatures cooled from 100 nonillion (1032) Kelvin to 1 billion (109) Kelvin, and protons and neutrons collided to make deuterium, an isotope of hydrogen. Most of the deuterium combined to make helium, and trace amounts of lithium were also generated.

    For the first 380,000 years or so, the universe was essentially too hot for light to shine, according to France’s National Center of Space Research (Centre National d’Etudes Spatiales,or CNES). The heat of creation smashed atoms together with enough force to break them up into a dense plasma, an opaque soup of protons, neutrons and electrons that scattered light like fog.

    Roughly 380,000 years after the Big Bang, matter cooled enough for atoms to form during the era of recombination, resulting in a transparent, electrically neutral gas, according to NASA. This set loose the initial flash of light created during the Big Bang, which is detectable today as cosmic microwave background radiation [CMB]. However, after this point, the universe was plunged into darkness, since no stars or any other bright objects had formed yet.

    Cosmic Background Radiation Planck
    CMB Per ESA/Planck

    ESA Planck
    Planck

    About 400 million years after the Big Bang, the universe began to emerge from the cosmic dark ages during the epoch of reionization. During this time, which lasted more than a half-billion years, clumps of gas collapsed enough to form the first stars and galaxies, whose energetic ultraviolet light ionized and destroyed most of the neutral hydrogen.

    Although the expansion of the universe gradually slowed down as the matter in the universe pulled on itself via gravity, about 5 or 6 billion years after the Big Bang, according to NASA, a mysterious force now called dark energy began speeding up the expansion of the universe again, a phenomenon that continues today.

    A little after 9 billion years after the Big Bang, our solar system was born.

    The Big Bang

    The Big Bang did not occur as an explosion in the usual way one think about such things, despite one might gather from its name. The universe did not expand into space, as space did not exist before the universe, according to NASA Instead, it is better to think of the Big Bang as the simultaneous appearance of space everywhere in the universe. The universe has not expanded from any one spot since the Big Bang — rather, space itself has been stretching, and carrying matter with it.

    Since the universe by its definition encompasses all of space and time as we know it, NASA says it is beyond the model of the Big Bang to say what the universe is expanding into or what gave rise to the Big Bang. Although there are models that speculate about these questions, none of them have made realistically testable predictions as of yet.

    In 2014, scientists from the Harvard-Smithsonian Center for Astrophysics announced that they had found a faint signal in the cosmic microwave background that could be the first direct evidence of gravitational waves, themselves considered a “smoking gun” for the Big Bang. The findings were hotly debated, but the search for these mysterious ripples continues.

    Gravitational Wave Background
    Gravitations Wave background theorized By the BICEP2 collaboration but not yet accepted.

    Age

    The universe is currently estimated at roughly 13.8 billion years old, give or take 130 million years. In comparison, the solar system is only about 4.6 billion years old.

    This estimate came from measuring the composition of matter and energy density in the universe. This allowed researchers to compute how fast the universe expanded in the past. With that knowledge, they could turn the clock back and extrapolate when the Big Bang happened. The time between then and now is the age of the universe.

    Structure

    Scientists think that in the earliest moments of the universe, there was no structure to it to speak of, with matter and energy distributed nearly uniformly throughout. According to NASA, the gravitational pull of small fluctuations in the density of matter back then gave rise to the vast web-like structure of stars and emptiness seen today. Dense regions pulled in more and more matter through gravity, and the more massive they became, the more matter they could pull in through gravity, forming stars, galaxies and larger structures known as clusters, superclusters, filaments and walls, with “great walls” of thousands of galaxies reaching more than a billion light years in length. Less dense regions did not grow, evolving into area of seemingly empty space called voids.

    Content

    Until about 30 years ago, astronomers thought that the universe was composed almost entirely of ordinary atoms, or “baryonic matter,” According to NASA. However, recently there has been ever more evidence that suggests most of the ingredients making up the universe come in forms that we cannot see.

    It turns out that atoms only make up 4.6 percent of the universe. Of the remainder, 23 percent is made up of dark matter, which is likely composed of one or more species of subatomic particles that interact very weakly with ordinary matter, and 72 percent is made of dark energy, which apparently is driving the accelerating expansion of the universe.

    When it comes to the atoms we are familiar with, hydrogen makes up about 75 percent, while helium makes up about 25 percent, with heavier elements making up only a tiny fraction of the universe’s atoms, according to NASA.

    Shape

    The shape of the universe and whether or not it is finite or infinite in extent depends on the struggle between the rate of its expansion and the pull of gravity. The strength of the pull in question depends in part on the density of the matter in the universe.

    If the density of the universe exceeds a specific critical value, then the universe is “closed” and “positive curved” like the surface of a sphere. This means light beams that are initially parallel will converge slowly, eventually cross and return back to their starting point, if the universe lasts long enough. If so, according to NASA, the universe is not infinite but has no end, just as the area on the surface of a sphere is not infinite but has no beginning or end to speak of. The universe will eventually stop expanding and start collapsing in on itself, the so-called “Big Crunch.”

    If the density of the universe is less than this critical density, then the geometry of space is “open” and “negatively curved” like the surface of a saddle. If so, the universe has no bounds, and will expand forever.

    If the density of the universe exactly equals the critical density, then the geometry of the universe is “flat” with zero curvature like a sheet of paper, according to NASA. If so, the universe has no bounds and will expand forever, but the rate of expansion will gradually approach zero after an infinite amount of time. Recent measurements suggest that the universe is flat with only a 2 percent margin of error.

    It is possible that the universe has a more complicated shape overall while seeming to possess a different curvature. For instance, the universe could have the shape of a torus, or doughnut.

    Expanding universe

    In the 1920s, astronomer Edwin Hubble discovered the universe was not static. Rather, it was expanding, a find that revealed the universe was apparently born in a Big Bang.

    After that, it was long thought the gravity of matter in the universe was certain to slow the expansion of the universe. Then, in 1998, the Hubble Space Telescope’s observations of very distant supernovae revealed that a long time ago, the universe was expanding more slowly than it is today. In other words, the expansion of the universe was not slowing due to gravity, but instead inexplicably was accelerating. The name for the unknown force driving this accelerating expansion is dark energy, and it remains one of the greatest mysteries in science.

    Additional reporting by Nola Taylor Redd, Space.com Contributor.

    See the full article here.

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  • richardmitnick 7:09 am on January 24, 2015 Permalink | Reply
    Tags: , , BESSY II Synchrotron, space.com   

    From SPACE.com: “Magnetic Fields of Asteroids Lasted Hundreds of Millions of Years” 

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    January 21, 2015
    Mike Wall

    1
    An image of the Esquel meteorite, a pallasite that consists of gem-quality cystals embedded in metal.
    Credit: Natural History Museum, London

    The magnetic fields of planetary building blocks lasted for a surprisingly long time in the solar system’s early days, a new study suggests.

    The magnetic fields of these big asteroids were apparently generated by the same process that drives Earth’s global magnetic activity, and could have persisted for hundreds of millions of years after the objects’ formation, researchers said.

    The study team analyzed pallasites, iron-and-nickel meteorites believed to originate from an ancient rocky body about 250 miles (400 kilometers) wide. The pallasites contain tiny particles of ‪tetrataenite — a mineral that records a magnetic history of the parent body going back billions of years.

    The researchers probed this history using an X-ray electron microscope at the BESSY II synchrotron in Berlin, capturing the moment when the big asteroid’s global magnetic field died.

    Bessy II Synchrotron
    BESSY II Synchrotron II
    BESSY II

    ‪”We’re taking ancient magnetic field measurements in nanoscale materials to the highest-ever resolution in order to piece together the magnetic history of asteroids,” study lead author James Bryson, a Ph.D. student at Cambridge University in England, said in a statement. “It’s like a cosmic archaeological mission.”

    The pallasites’ parent body was one of many relatively large, rocky objects that formed in the first few million years of solar system history. Radioactive decay heated up the interiors of these planetary building blocks, which segregated into molten metal cores surrounded by rocky mantles.

    Scientists had thought that the global magnetic fields of these big asteroids were probably created by the circulation of heat energy within the core. This process would likely have petered out relatively quickly, after a few tens of millions of years at most, researchers said.

    But the new X-ray observations, along with computer simulations performed by the study team, paint a different picture: The pallasite parent body’s magnetic field lasted for a long time — perhaps several hundred million years. Furthermore, this field was probably generated by the progressive solidification of the core — a phenomenon known as “compositional convection,” rather than thermal convection as previously presumed, researchers said. (When the core solidified completely, the magnetic field died.)

    Compositional convection is also the primary process driving the creation of Earth’s magnetic field.

    ‪”It’s funny that we study other bodies in order to learn more about the Earth,” Bryson said. “Since asteroids are much smaller than the Earth, they cooled much more quickly, so these processes occur on shorter timescales, enabling us to study the whole process of core solidification.”

    The new study has applications to other rocky bodies in the solar system as well, study team members said.

    “These conclusions imply that a second epoch of dynamo activity [after thermal-convection-driven dynamos] across a potentially large fraction of small bodies occurred in the early solar system, and help to explain the long-lived magnetic activity observed for other bodies, such as the moon,” they wrote in the new study, which was published online today (Jan. 21) in the journal Nature.

    See the full article here.

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  • richardmitnick 8:15 am on January 17, 2015 Permalink | Reply
    Tags: , , space.com, Tidal locking   

    From SPACE.com: “For Alien Planets, Atmosphere May Be Key to Day-Night Cycle” 

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    January 15, 2015
    Calla Cofield

    Alien planets that orbit close to their parent stars may be at high risk of the ultimate hot-cold scenario, with one side stuck in permanent daylight while the other shrouded in everlasting night. But a thin atmosphere may be enough to save a planet from this fate.

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    An artist’s concept of Kepler-186f, an Earth-size planet found orbiting in the habitable zone of its parent star. A planet like Kepler-186f with a smaller orbit than Earth’s could be at risk of having only one hemisphere face toward the star, with the other hemisphere always facing away. Credit: NASA Ames/SETI Institute/JPL-Caltech

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    Size comparison of Kepler-186 f with Earth

    Living on a planet with one side in perpetual sunlight and the other in perpetual darkness would pose some significant challenges for survival — the sunny side of the planet might reach boiling temperatures while the dark side might be completely frozen.

    This scenario occurs when a planet’s rotation (its day) becomes synched with its orbit (its year), meaning only one side of the planet ever faces its parent star. Earth’s moon experiences this “synchronous rotation [tidal_locking],” which is why only one side of the moon ever faces the Earth. Some researchers fear that many of the new exoplanets being discovered around other stars are at risk of experiencing this synchronous rotation, which might lower the odds that those planets support life.

    However, new research by scientists at the Canadian Institute for Theoretical Astrophysics (CITA) shows that exoplanets with Earth-like atmospheres may have the right ingredients to avoid the fate of synchronous rotation.

    Synchronous rotation is also known as tidal locking, because tides are at the heart of why these orbits arise, the researchers explain in their paper. The moon’s pull on the Earth creates tides in the ocean — in turn, the Earth exerts a tidal pull on the moon. The tidal force slows down the rotation of the moon (or planet), until it is synchronized with the body’s orbit.

    Because tidal forces are stronger at shorter distances, synchronous rotation tends to happen to bodies that orbit close to their parent body. Earth is not at risk of falling into a synchronized cycle because it lies too far away from the sun. Some researchers have theorized that the reason Venus does not experience synchronous rotation is because of its thick atmosphere.

    Planetary atmospheres are not totally spherical — they can move, shift and bulge in some areas. As the atmosphere shifts, its mass exerts a force on the planet, and computer simulations show that this atmospheric force can be enough to counter the frictional force of the tides, potentially stopping the planet from falling into a synchronous rotation.

    A thick, heavy atmosphere like the one found on Venus could exert a rather significant force on the planet — but could an atmosphere 100 times less massive, like Earth’s, do the same?

    “The main surprise that comes out of their work is that if the Earth were in Venus’ current location, the effect of [Earth’s] atmosphere, while a hundred times less massive, would be almost ten times as strong as the effect of Venus’ atmosphere,” Jeremy Leconte, a post-doctoral fellow the CITA and an author on the new paper, wrote in an email to Space.com.

    The reason has to do with the heating of the planet’s atmosphere. Differences in temperature generate strong winds that redistribute the atmosphere, distorting it in such a way that it tends to counter the drag of tidal forces.

    As for exoplanets, Leconte writes, “While astronomers are still awaiting observational evidence, theoretical arguments suggest that many exoplanets should be able to keep an atmosphere as massive as that of the Earth.”

    “In that case, this new study shows that a large number of known terrestrial exoplanets should not be in a state of synchronous rotation, as initially believed. Thus, they would have a diurnal or night/day cycle like on Earth. The duration of their days, however, could last between a few weeks and a few months.”

    The researchers say their results also create scenarios where a planet like Earth would still become tidally locked, so the findings do not predict the fate of every Earth-like exoplanet with a short orbit. But the results do provide another bit of hope that life is surviving elsewhere in the universe.

    The study is detailed online in the Jan. 15 edition of the journal Science.

    See the full article here.

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    • kagmi 2:46 pm on January 17, 2015 Permalink | Reply

      Reblogged this on kagmi.

      Liked by 1 person

    • europasicewolf 4:51 pm on January 24, 2015 Permalink | Reply

      Great post! I’m inclined to think we’re already living in perpetual darkness just now so I suspect it would be a far more interesting experience on a different planet!

      Like

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