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  • richardmitnick 2:20 pm on October 19, 2014 Permalink | Reply
    Tags: , , , , , Exoplanets,   

    From astrobio.net: “Rediscovering Venus to Find Faraway Earths “ 

    Astrobiology Magazine

    Astrobiology Magazine

    Oct 19, 2014
    Lyndsay Meyer
    The Optical Society

    New optical device designed to measure gravitational pull of a planet should speed the search for Earth-like exoplanets.

    Astronomers Chih-Hao Li and David Phillips of the Harvard-Smithsonian Center for Astrophysics want to rediscover Venus—that familiar, nearby planet stargazers can see with the naked eye much of the year.

    Granted, humans first discovered Venus in ancient times. But Li and Phillips have something distinctly modern in mind. They plan to find the second planet again using a powerful new optical device installed on the Italian National Telescope that will measure Venus’ precise gravitational pull on the sun. If they succeed, their first-of-its-kind demonstration of this new technology will be used for finding Earth-like exoplanets orbiting distant stars.

    Italian National Telescope Galileo
    Italian National Telescope Galileo Internal
    Galileo Italian National Telescope

    “We are building a telescope that will let us see the sun the way we would see other stars,” said Phillips, who is a staff scientist at the Harvard-Smithsonian Center for Astrophysics. He and Li, a research associate at the Center for Astrophysics, will describe the device in a paper to be presented at The Optical Society’s (OSA) 98th Annual Meeting, Frontiers in Optics, being held Oct. 19-23 in Tucson, Arizona, USA. Li is the lead author of the paper, which has 12 collaborators.

    Astronomers have identified more than 1,700 exoplanets, some as far as hundreds of light years away. Most were discovered by the traditional transit method, which measures the decrease in brightness when a planet orbiting a distant star transits that luminous body, moving directly between the Earth and the star. This provides information about the planet’s size, but not its mass.

    Li and Phillips are developing a new laser-based technology known as the green astro-comb for use with the “radial velocity method,” which offers complementary information about the mass of the distant planet.

    From this information, astronomers will be able to determine whether distant exoplanets they discover are rocky worlds like Earth or less dense gas giants like Jupiter. The method is precise enough to help astronomers identify Earth-like planets in the “habitable zone,” the orbital distance “sweet-spot” where water exists as a liquid.

    Better Precision with a Laser

    The radial velocity method works by measuring how exoplanet gravity changes the light emitted from its star. As exoplanets circle a star, their gravitation tugs at the star changing the speed with which it moves toward or away from Earth by a small amount. The star speeds up slightly as it approaches Earth, with each light wave taking a fraction of a second less time to arrive than the wave before it.

    To an observer on Earth, the crests of these waves look closer together than they should, so they appear to have a higher frequency and look bluer. As the star recedes, the crests move further apart and the frequencies seem lower and redder.

    The astro-comb calibrates the Italian National Telescope’s HARPS-Nspectrograph using an observation of the asteroid Vesta. The top figure is a colorizedversion of the raw HARPS-N spectrum, showing the astro-comb calibration dottedlines and the sun’s spectrum reflected off Vesta as mostly solid vertical lines.The middle figure shows the raw data converted to a very precise standard one-dimensionalplot of spectral intensity vs. wavelength. The very regular astro-comb calibrationspectrum is below below. Credit: David Phillips

    This motion-based frequency change is known as the Doppler shift. Astronomers measure it by capturing the spectrum of a star on the pixels of a digital camera and watching how it changes over time.

    Today’s best spectrographs are only capable of measuring Doppler shifts caused by velocity changes of 1 meter per second or more. Only large gas giants or “super-earths” close to their host stars have enough gravity to cause those changes.

    The new astro-comb Li, Phillips and their colleagues are developing, however, will be able to detect Doppler shifts as small as 10 centimeters per second—small enough to find habitable zone Earth-like planets, even from hundreds of light years away.

    “The astro-comb works by injecting 8,000 lines of laser light into the spectrograph. They hit the same pixels as starlight of the same wavelength. This creates a comb-like set of lines that lets us map the spectrograph down to 1/10,000 of a pixel. So if I have light on this section of the pixel, I can tell you the precise wavelength,” Phillips explained.

    “By calibrating the spectrograph this way, we can take into account very small changes in temperature or humidity that affect the performance of the spectrograph. This way, we can compare data we take tonight with data from the same star five years from now and find those very small Doppler shifts,” he said.

    Seeing Green

    Li and his co-researchers pioneered the astro-comb several years ago, but it only worked with infrared and blue light. Their new version of the astro-comb lets astronomers measure green light—which is better for finding exoplanets.

    “The stars we look at are brightest in the green visible range, and this is the range spectrographs are built to handle,” Phillips said.

    Building the green astro-comb was a challenge, since the researchers needed to convert red laser light to green frequencies. They did it by making small fibers that convert one color of light to another.

    A slowly rotating planet is not guaranteed to be habitable, as is evident when looking at the inhospitable Venus. Credit: NASA/JPL/Caltech

    “Red light goes in and green light comes out,” Phillips said. “Even though I see it every day and understand the physics, it looks like magic.”

    The researchers plan to test the green astro-comb by pointing it at our sun, analyzing its spectrum to see if they can find Venus and rediscover its characteristic period of revolution, its size, its mass and its composition.

    “We know a lot about Venus, and we can compare our answers to what we already know, so we are more confident about our answers when we point our spectrographs at distant stars,” Li said.

    The Harvard-Smithsonian team is installing this device on the High-Accuracy Radial Velocity Planet Searcher-North (HARPS-N), a new spectrograph designed to search for exoplanets using the Italian National Telescope.

    “We will look at the thousands of potential exoplanets identified by the Kepler satellite telescope by the transit method. Together, our two methods can tell us a lot about those worlds,” Li said.

    And, because he will have already discovered Venus, he will be more certain of the answers.

    See the full article here.


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  • richardmitnick 11:47 am on October 4, 2014 Permalink | Reply
    Tags: , Exoplanets, ,   

    From astrobio.net: “Are the world’s religions ready for E.T.?” 

    Astrobiology Magazine

    Astrobiology Magazine

    Oct 4, 2014
    Source: Vanderbilt University
    David Salisbury

    In 1930, Albert Einstein was asked for his opinion about the possibility of life elsewhere in the universe. “Other beings, perhaps, but not men,” he answered. Then he was asked whether science and religion conflict. “Not really, though it depends, of course, on your religious views.”

    Over the past 10 years, astronomers’ new ability to detect planets orbiting other stars has taken this question out of the realm of philosophy, as it was for Einstein, and transformed it into something that scientists might soon be able to answer.

    Realization that the nature of the debate about life on other worlds is about to fundamentally change led Vanderbilt Professor of Astronomy David Weintraub to begin thinking seriously about the question of how people will react to the discovery of life on other planets. He realized, as Einstein had observed, that people’s reactions will be heavily influenced by their religious beliefs. So he decided to find out what the world’s major religions have to say about the matter. The result is a book titled Religions and Extraterrestrial Life (Springer International Publishing) published this month.

    Credit: Springer

    “When I did a library search, I found only half a dozen books and they were all written about the question of extraterrestrial life and Christianity, and mostly about Roman Catholicism, so I decided to take a broader look,” the astronomer said.

    As a result, his book describes what religious leaders and theologians have to say about extraterrestrial life in more than two dozen major religions, including Judaism, Roman Catholicism, the Eastern Orthodox churches, the Church of England and the Anglican Communion, several mainline Protestant sects, the Southern Baptist Convention and other evangelical and fundamentalist Christian denominations, the Religious Society of Friends (Quakers), Seventh Day Adventism and Jehovah’s Witnesses, the Church of Jesus Christ of Latter-Day Saints (Mormons), Islam and several major Asian religions including Hinduism, Buddhism and the Bahá’í Faith.

    Discovery of planets

    The remarkable progress that astronomers have made at detecting exoplanets gives the issue of extraterrestrial life a new sense of immediacy. In 2000, astronomers had detected 50 planets orbiting other stars. Today, the number has grown to more than 1,000. If the rate of discovery keeps up its current pace, astronomers will have identified more than a million exoplanets by the year 2045.

    “If even one exoplanet shows signs of biological activity – and those signs should not be hard to detect, if living things are present – then we will know Earth is not the only place in the universe where life exists,” Weintraub points out. “Although it is impossible to prove a negative, if we have not found any signs of life after a million exoplanets have been studied, then we will know that life in the universe is, at best, exceedingly rare.”

    Public opinion polling indicates that about one fifth to one third of the American public believes that extraterrestrials exist, Weintraub reports. However, this varies considerably with religious affiliation.

    Belief in extraterrestrials varies by religion

    55 percent of Atheists
    44 percent of Muslims
    37 percent of Jews
    36 percent of Hindus
    32 percent of Christians

    Of the Christians, more than one third of the Eastern Orthodox faithful (41 percent), Roman Catholics (37 percent), Methodists (37 percent), and Lutherans (35 percent) professed belief in extraterrestrial life. Only the Baptists (29 percent) fell below the one-third threshold.

    Asian religions would have the least difficulty in accepting the discovery of extraterrestrial life, Weintraub concluded. Some Hindu thinkers have speculated that humans may be reincarnated as aliens, and vice versa, while Buddhist cosmology includes thousands of inhabited worlds.

    Weintraub quotes passages in the Qur’an that appear to support the idea that spiritual beings exist on other planets, but notes that these beings may not practice Islam as it is practiced on Earth. “Islam, like other faiths, has fundamentalist and conservative traditions. All Muslims, however, likely would agree that the prophetically revealed religion of Islam is a set of practices designed only for humans on earth,” Weintraub wrote.

    Weintraub found very little in Judaic scriptures or rabbinical writings that bear on the question. The few Talmudic and Kabbalistic commentaries on the subject do assert that space is infinite and contains a potentially infinite number of worlds and that nothing can deny the existence of extraterrestrial life. At the same time, Jews don’t believe the discovery of extraterrestrial intelligence would have much effect on them. He quotes a Jewish anthropologist and scholar who has addressed this issue and concluded that the relationship beween Jews and God would not be affected in the slightest by “the existence of other life forms, newly discovered scientific realities or pan-human behavioral changes.”

    Christian debate

    Among Christian religions, the Roman Catholics have done the most thinking about the possibility of life on other worlds, the astronomer discovered. In fact, they have had an on-again, off-again theological debate that has gone on for a thousand years.

    Author David Weintraub (Daniel Dubois / Vanderbilt)

    The crux of the matter is original sin. If intelligent aliens are not descended from Adam and Eve, do they suffer from original sin? Do they need to be saved? If they do, then did Christ visit them and was he crucified and resurrected on other planets? “From a Roman Catholic perspective, if sentient extraterrestrials exist some but perhaps not all such species may suffer original sin and will require redemption,” Weintraub summarizes.

    The inherent diversity of Protestant denominations, where individuals are encouraged to interpret scripture independently, has led to many conflicting approaches to the question of extraterrestrial intelligence. Weintraub determined that the views of Lutheran theologian Paul Tillich appear to represent a viable consensus. Tillich argued that the need for salvation is universal and the “saving power” of God must be everywhere. At the same time, he maintained that God’s plan for human life need not be the same as his plan for aliens.

    Evangelical and fundamental Christians are most likely to have difficulty accepting the discovery of extraterrestrial life, the astronomer’s research indicates. “…most evangelical and fundamentalist Christian leaders argue quite forcefully that the Bible makes clear that extraterrestrial life does not exist. From this perspective, the only living, God-worshipping beings in the entire universe are humans, created by God, who live on Earth.” Southern Baptist evangelist Billy Graham was a prominent exception who stated that he firmly believes “there are intelligent beings like us far away in space who worship God.”

    Weintraub also identified two religions – Mormonism and Seventh-day Adventism – whose theology embraces extraterrestrials. In Mormonism, God helps exalt lesser souls so they can achieve immortality and live as gods on other worlds. And, Ellen White, who co-founded Seventh-Day Adventism, wrote that Got had given her a view of other worlds where the people are “noble, majestic and lovely” because they live in strict obedience to God’s commandments.

    Are we ready?

    In answer to the question “Are we ready?” Weintraub concludes, “While some of us claim to be ready, a great many of us probably are not… very few among us have spent much time thinking hard about what actual knowledge about extraterrestrial life, whether viruses or single-celled creatures or bipeds piloting intergalactic spaceships, might mean for our personal beliefs [and] our relationships with the divine.”

    See the full article, with video, here.


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  • richardmitnick 7:00 pm on October 2, 2014 Permalink | Reply
    Tags: , , , , , Exoplanets,   

    From Ethan Siegel: “Preparing for Alien Life” 

    Starts with a bang
    Starts with a Bang

    Oct 2, 2014
    Ethan Siegel

    “Language… has created the word ‘loneliness’ to express the pain of being alone. And it has created the word ‘solitude’ to express the glory of being alone.” -Paul Tillich

    Recently, the John Templeton Foundation ran a series of articles asking one of the biggest questions of all: Are We Alone in the Universe? One of the articles in particular I was a big fan of, but would have liked to seen go longer and more in-depth. You see, we have every reason to not only believe that some form of life is quite common in the Universe, but that if we get lucky, we’re going to find it in the next two decades, tops.

    Let me explain.

    Image credit: Robert Gendler of http://www.robgendlerastropics.com/Biography.html, of the Rosette_Nebula.

    Everywhere we look in the Universe, we see evidence that the same cosmic story is unfolding, from nearby stars to neighboring galaxies to distant clusters across the Universe. We see the same laws of physics, the same physical phenomena, and a shared history that cuts across the billions of light years that separate us.

    We see a Universe that began from a hot, dense, expanding state,

    Image credit: NASA / Goddard Space Flight Center, via http://cosmictimes.gsfc.nasa.gov/universemashup/archive/pages/expanding_universe.html.

    where matter won out over antimatter,

    Image credit: me, with the background by Christof Schaefer.

    where stable atomic nuclei and then neutral atoms formed,

    Image credit: Universe Adventure, © 2005 LBNL Physics Division.

    where gravitational collapse caused the first stars to form,

    Image credit: The Coronet Cluster, X-ray/IR composite, via NASA/CXC/J. Forbrich, NASA/JPL-Caltech L.Allen (Harvard-Smithsonian CfA), IRAC GTO.

    where the heavy elements formed in their cores were recycled back into interstellar space when those stars died in supernova explosions,

    Image credit: Supernova Remnant 1E 0102.2–7219, via NASA / CXC / MIT / SAO / STScI / J. DePasquale / D.Dewey et al., at http://www.cfa.harvard.edu/imagelist/2009-16.

    where complex molecules arose from multiple generations of stars spilling their innards back into deep space,
    Image credit: NASA, ESA, CXC, SSC, and STScI.

    where later generations of stars formed with planets, moons, asteroids and comets around them,

    Image credit: Avi M. Mandell, NASA.

    and where the ingredients essential to life are ubiquitous.

    This is the consistent cosmic story that we see cutting across the entire observable Universe, from nearby stars to distant nebulae to the galactic center to other galaxies, as far as our technology allows us to observe. Over the last two decades, we’ve discovered the first planets around Sun-like stars [exoplanets]. While initially we tended to discover hot, giant planets in close orbits around their stars, that turned out to be solely because those types of planets are the easiest to observe: they causes the largest “rocking motion” (or stellar wobble) of their parent star due to gravitation, and they also block the most amount of light if they happen to have the right alignment to transit in front of their star’s disk relative to our line-of-sight.

    It’s the planets and planetary candidates that are found via this latter method — the planetary transit — that are likely to be the first planets found that harbor life. This isn’t because planets that transit in front of their stars relative to us are more likely to contain life, but rather because it’s easiest to detect a surefire sign of life using this method.

    Even though there are many conceivable chemical reactions that can give rise to life, and many possible signatures that life would leave behind as a by-product, there are a great many abiotic processes that we’d have to rule out. In addition, there are a great many properties of Earth that — although we could see them from a distant star — aren’t necessarily indicators of life.

    From a long distance away, we could find, with a large enough telescope, that Earth contained:

    oceans and continents,
    an active, variable-cloud-cover atmosphere, and
    polar icecaps that grew and shrank with the seasons.

    But none of those are necessarily indicative of life. However, there is a signature that Earth possesses that, as far as we know, couldn’t occur on a planet that didn’t have life.

    Image credit: Ziurys et al. 2006, NRAO Newsletter, 109, 11.

    You see, every atom and molecule in existence has a signature spectrum that’s unique to that configuration. Hydrogen, helium, lithium and all the elements of the periodic table have specific wavelengths of light that they absorb and emit, corresponding to the atomic transitions that can occur within those atoms, with all other transitions being forbidden. This is true of molecules as well, including the nitrogen, water vapor, carbon dioxide and ozone in the Earth’s atmosphere.

    Periodic Tbale of elements

    All of those molecules could be the result of either organic or inorganic processes, but there’s one component of Earth’s atmosphere that couldn’t have arisen through inorganic processes, and that’s oxygen.

    Image credit: Fran Bagenal of Colorado, via http://lasp.colorado.edu/~bagenal/3720/CLASS5/5Spectroscopy.html.

    There are only a few ways to produce oxygen abiotically, mostly from the high-energy dissociation of other molecules, and even then that only produces it in trace amounts. Here on Earth, however, our atmosphere is a tremendous 21% oxygen, and that percentage has been signficant (at 10% or above) for some two billion years. Although not every planet that has life on it will have a large oxygen content in its atmosphere, every planet that has a large oxygen content in its atmosphere has, at the very least, a history of life that gave rise to that oxygen!

    So how, then, would we detect oxygen on a planetary atmosphere?

    Image credit: H. Rauer et al.: Potential Biosignatures in super-Earth Atmospheres. Astronomy & Astrophysics, February 16, 2011.

    We couldn’t do it the same way we do it here on Earth; the light coming from an individual, rocky planet in another solar system is far too faint to be seen with not only existing telescope technology, but with any of the telescopes proposed to be built over the next generation. But we are expecting huge upgrades in telescope technology over the next decade or two: the largest, most powerful telescope in space will go from Hubble, at 2.4 meters in diameter, to James Webb, which will have a primary mirror that’s 6.5 meters in diameter, with five times the light-gathering power!

    NASA Hubble Telescope
    NASA/ESA Hubble

    NASA Webb Telescope

    Image credit: NASA.

    In addition to that, the current generation of 8-to-10 meter ground-based telescopes will be superseded by 20-to-35 meter telescopes, providing not only additional light-gathering power but also increased resolution. Examples include the Giant Magellan Telescope, the Thirty Meter Telescope and the European Extremely Large Telescope projects.

    Giant Magellan TelescopeGiant Magellan Interior
    Giant Magellan Telescope

    TMT Schematic


    This improvement in sensitivity means we’re going to be able to detect smaller effects, find smaller planets around larger stars, and many other advances. But perhaps the greatest advance towards finding a planet with oxygen on it — and hence, life — will occur where we have rocky, Earth-sized planets transiting in front of their stars.

    Image credit: NASA / JPL-Caltech, via http://www.nasa.gov/centers/goddard/news/topstory/2007/cloudy_world.html.

    You see, when a planet passes in front of its star, it not only blocks a fraction of the starlight coming from the star, it also allows a tiny amount of that starlight to pass through the planet’s atmosphere, streaming on into the Universe towards us! Just as the Moon turns red during an eclipse because sunlight passes through the Earth’s atmosphere, so should we be able to see tiny absorption signatures corresponding to different elements when distant starlight passes through a transiting planet’s atmosphere.

    So far, with present technology, we’ve been able to find signatures like water in the atmospheres of Neptune-sized planets.

    Image credit: Harvard Smithsonian Center for Astrophysics, illustration of Planet HAT-P-11b.

    But what the next generation of telescope advances should bring us is the ability to find those same types of signatures around Earth-sized planet, and we should be able to find those signatures around stars up to perhaps 25-to-30 light years away, or conceivably even farther! Given that we have some 300 stars within that conservative distance alone, and given that some of those planetary systems are bound to have a fortuitous alignment with our line-of-sight, we’re going to have the first opportunity, if oxygen-producing life is really abundant in the Universe, to find our first planet with alien life within a single generation.

    Image credit: NASA / NSF / Lynette Cook. Via http://www.nasa.gov/topics/universe/features/gliese_581_feature.html.

    If the Universe is kind to us, the first signs of life beyond our Solar System will not only teach us that we’re not alone, but that the optimists have it right. Life might not only exist on planets other than Earth, it might be more common than most of us have dared to dream.

    See the full article, with video, here.

    Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible.

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  • richardmitnick 5:41 pm on September 30, 2014 Permalink | Reply
    Tags: , , , , , Exoplanets,   

    From SPACE.com: “Search for Alien Life Should Target Water, Oxygen and Chlorophyll” 

    space-dot-com logo


    September 30, 2014
    Mike Wall

    The next generation of space telescopes hunting for signs of extraterrestrial life should focus on water, then oxygen and then alien versions of the plant chemical chlorophyll, a new study suggests.

    In the past 20 years or so, astronomers have confirmed the existence of nearly 2,000 worlds outside Earth’s solar system. Many of these exoplanets lie in the habitable zones of stars, areas potentially warm enough for the worlds to harbor liquid water on their surfaces. Astrobiologists hope that life may someday be spotted on such alien planets, since there is life pretty much everywhere water exists on Earth.

    One strategy to discover signs of such alien life involves looking for ways that organisms might change a world’s appearance. For example, chemicals typically shape what are known as the spectra seen from planets by adding or removing wavelengths of light. Alien-hunting telescopes could look for spectra that reveal chemicals associated with life. In other words, these searches would focus on biosignatures — chemicals or combinations of chemicals that life could produce, but that processes other than life could not or would be unlikely to create.

    Astrophysicists Timothy Brandt and David Spiegel at the Institute for Advanced Study in Princeton, New Jersey, sought to see how challenging it might be to conclusively identify signatures of water, oxygen and chlorophyll — the green pigment that plants use to convert sunlight to energy — on a distant twin of Earth using a future off-Earth instrument such as NASA’s proposed Advanced Technology Large-Aperture Space Telescope (ATLAST).

    8-meter monolithic mirror telescope (credit: MSFC Advanced Concepts Office)
    16-meter segmented mirror telescope (credit: Northrop Grumman Aerospace Systems & NASA/STScI)
    two conceptual schemes for ATLAST

    The scientists found that water would be the easiest to detect.

    “Water is a very common molecule, and I think a mission to take spectra of exoplanets should certainly look for water,” said Brandt, the lead study author. “Indeed, we have found water in a few gas giants more massive than Jupiter orbiting other stars.”

    In comparison, oxygen is more difficult to detect than previously thought, requiring scientific instruments approximately twice as sensitive as those needed to detect water and significantly better at discriminating between similar colors of light.

    “Oxygen, however, has only been a large part of Earth’s atmosphere for a few hundred million years,” Brandt said. “If we see it in an exoplanet, it probably points to life, but not finding oxygen certainly does not mean that the planet is sterile.”

    Although a well-designed space telescope could detect water and oxygen on a nearby Earth twin, the astrophysicists found the instrument would need to be significantly more sensitive, or very lucky, to see chlorophyll. Identifying this chemical typically requires scientific instruments about six times more sensitive than those needed for oxygen. Chlorophyll becomes as detectable as oxygen only when an exoplanet has a lot of vegetation and/or little in the way of cloud cover, researchers said.

    Chlorophyll slightly reddens the light from Earth. If extraterrestrial life does convert sunlight to energy as plants do, scientists expect that the alien process might use a different pigment than chlorophyll. But alien photosynthesis could also slightly redden planets, just as chlorophyll does.

    “Light comes in packets called photons, and only photons with at least a certain amount of energy are useful for photosynthesis,” Brandt said. Chlorophyll reflects photons that are too red and low in energy to be used for photosynthesis, and it may be reasonable to assume that extraterrestrial pigments would do the same thing, Brandt noted.

    The researchers suggest a strategy for discovering Earthlike alien life that first looks for water, then oxygen on the more favorable planets and finally chlorophyll on only the most exceptionally promising worlds.

    “The goal of a future space telescope will be primarily to detect water and oxygen on a planet around a nearby star,” Brandt said. “The construction and launch of such a telescope will probably cost at least $10 billion and won’t happen for at least 20 years — a lot of technology development needs to happen first — but it could be the most exciting mission of my lifetime.”

    Brandt and Spiegel detailed their findings online Sept. 1 in the journal Proceedings of the National Academy of Sciences.

    See the full article here.

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  • richardmitnick 10:45 am on September 15, 2014 Permalink | Reply
    Tags: , , , , , , Exoplanets   

    From Astrobiology: “Planets with Oddball Orbits Like Mercury Could Host Life” 

    Astrobiology Magazine

    Astrobiology Magazine

    Sep 15, 2014
    Charles Q. Choi

    On Mercury a solar day is about 176 Earth days long. During its first Mercury solar day in orbit the MESSENGER spacecraft imaged nearly the entire surface of Mercury to generate a global monochrome map at 250 meters per pixel resolution and a 1 kilometer per pixel resolution color map. Credit: NASA/JHU APL/CIW

    Mercury has an oddball orbit — it takes longer for it to rotate on its axis and complete a day than it takes to orbit the sun and complete a year. Now, researchers suggest photosynthesis could take place on an alien planet with a similarly bizarre orbit, potentially helping support complex life.

    However, the scientists noted that the threat of prolonged periods of darkness and cold on these planets would present significant challenges to life, and could even potentially freeze their atmospheres. They detailed their findings in the International Journal of Astrobiology.

    Astronomers have discovered more than 1,700 alien planets in the past two decades, raising the hope that at least some might be home to extraterrestrial life. Scientists mostly focus the search for alien life on exoplanets in the habitable zones of stars. These are regions where worlds would be warm enough to have liquid water on their surfaces, a potential boon to life.

    The 3:2 spin orbit resonance of Mercury and the Sun. Credit: Wikicommons

    Although many exoplanets are potentially habitable, they may differ from Earth significantly in one or more ways. For instance, habitable planets around dim red dwarf stars orbit much closer than Earth does to the Sun, sometimes even closer than Mercury’s distance. Red dwarfs are of interest as possible habitats for life because they are the most common stars in the universe — if life can exist around red dwarfs, then life might be very common across the cosmos. Recent findings from NASA’s Kepler Space Observatory suggest that at least half of all red dwarfs host rocky planets that are one-half to four times the mass of Earth.

    NASA Kepler Telescope

    Since a planet in the habitable zone of a red dwarf orbits very near its star, it experiences much stronger gravitational tidal forces than Earth does from the Sun, which slows the rate at which those worlds spin. The most likely result of this slowdown is that the planet enters what is technically called a 1:1 spin orbit resonance, completing one rotation on its axis every time it completes one orbit around its star. This rate of rotation means that one side of that planet will always face toward its star, while the other side will permanently face away, just as the Moon always shows the same side to Earth. One recent study suggests that such “tidally locked” planets may develop strange lobster-shaped oceans basking in the warmth of their stars on their daysides, while the nightsides of such worlds are mostly covered in an icy shell.

    However, if a habitable red dwarf planet has a very eccentric orbit — that is, oval-shaped — it could develop what is called a 3:2 spin orbit resonance, meaning that it rotates three times for every two orbits around its star. Mercury has such an unusual orbit, which can lead to strange phenomena. For instance, at certain times on Mercury, an observer could see the Sun rise about halfway and then reverse its course and set, all during the course of one mercurial day. Mercury itself is not habitable, since it lacks an atmosphere and experiences temperatures ranging from 212 to 1,292 degrees Fahrenheit (100 to 700 degrees Celsius).

    “If the Sun were less intense, Mercury would be within the habitable zone, and therefore life would have to adapt to strange light cycles,” said lead study author Sarah Brown, an astrobiologist at the United Kingdom Center for Astrobiology in Edinburgh, Scotland.

    Light is crucial for photosynthesis, the process by which plants and other photosynthetic organisms use the Sun’s rays to create energy-rich molecules such as sugars. Most life on Earth currently depends on photosynthesis or its byproducts in one way or the other, and while primitive life can exist without photosynthesis, it may be necessary for more complex multi-cellular organisms to emerge because the main source for oxygen on Earth comes from photosynthetic life, and oxygen is thought to be necessary for multi-cellular life to arise.

    To see what photosynthetic life might exist on a habitable red dwarf planet with an orbit similar to Mercury’s, scientists calculated the amount of light that reached all points on its surface. Their model involved a planet the same mass and diameter as the Earth with a similar atmosphere and amount of water on its surface. The red dwarf star was 30 percent the Sun’s mass and 1 percent as luminous, giving it a temperature of about 5,840 degrees Fahrenheit (3,225 degrees Celsius) and a habitable zone extending from 10 to 20 percent of an astronomical unit (AU) from the star. (One AU is the average distance between Earth and the Sun.)

    The 1:1 spin orbit resonance of Earth and the Moon. Credit: Wikicommons

    The scientists found that the amount of light the surface of these planets received concentrated on certain bright spots. Surprisingly, the amount of light these planets receive do not just vary over latitude as they do on Earth, where more light reaches equatorial regions than polar regions, but also varied over longitude. Were photosynthetic life to exist on worlds with these types of orbits, “one would expect to find niches that depend on longitude and latitude, rather than just latitude,” said study co-author Alexander Mead, a cosmologist at the Royal Observatory, Edinburgh, in Scotland.

    The research team found these planets could experience nights that last for months. This could pose major problems for photosynthetic life, which depends on light. Still, the scientists noted that many plants can store enough energy to last through 180 days of darkness. Moreover, some photosynthetic microbes spend up to decades dormant in the dark, while others are mixotrophic, which means they can survive on photosynthesis when light is abundant and switch to devouring food when light is absent.

    Another problem these long spans of darkness pose for life is the cold, which could freeze the atmospheres of these planets. Still, the investigators note that heat can flow from the dayside of such a planet to its nightside and prevent this freezing if that planet’s atmosphere is sufficiently dense and can trap infrared light from the planet’s star. This heat flow could lead to very strong winds, but this does not necessarily make the world uninhabitable, they added.

    “Life having to cope with such tidally driven resonances could be common in the universe,” Mead said. “It changes one’s perception of what habitable planets in the Universe would be like. There are many possibilities that are very un-Earth-like.”

    It is difficult to form Mercury in solar system simulations, suggesting that some of our assumptions about the small planet’s formation might be wrong, a new study suggests. NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

    However, the researchers noted that the strength of a world’s magnetic field depends in large part on how quickly it spins, which suggests that planets with orbits like Mercury’s might have relatively weak magnetic fields. This could mean these worlds are not as good at deflecting harmful electrically charged particles streaming from their red dwarfs and other stars that can damage organisms and strip off the atmospheres of these planets.

    The investigators suggested that dense atmospheres could help keep such planets habitable in the face of radiation from space. They added that life might be confined to certain spots on the surfaces of those planets that experience relatively safe levels of radiation.

    Are astronomers capable of detecting habitable planets with a 3:2 spin orbit resonance?

    “Measuring the day length of extrasolar planets is enormously difficult, and the first day length measurements for any extrasolar planets were only published this year,” Mead said. “Such a measurement for the planets we discuss would be much more difficult due to the fact that they are small, rocky planets around faint stars. This means that we are probably a long way from measuring the spin rates of such habitable worlds.”

    Another problem these long spans of darkness pose for life is the cold, which could freeze the atmospheres of these planets. Still, the investigators note that heat can flow from the dayside of such a planet to its nightside and prevent this freezing if that planet’s atmosphere is sufficiently dense and can trap infrared light from the planet’s star. This heat flow could lead to very strong winds, but this does not necessarily make the world uninhabitable, they added.

    “Life having to cope with such tidally driven resonances could be common in the universe,” Mead said. “It changes one’s perception of what habitable planets in the Universe would be like. There are many possibilities that are very un-Earth-like.”

    It is difficult to form Mercury in solar system simulations, suggesting that some of our assumptions about the small planet’s formation might be wrong, a new study suggests. NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

    It is difficult to form Mercury in solar system simulations, suggesting that some of our assumptions about the small planet’s formation might be wrong, a new study suggests. NASA/Johns Hopkins University

    However, the researchers noted that the strength of a world’s magnetic field depends in large part on how quickly it spins, which suggests that planets with orbits like Mercury’s might have relatively weak magnetic fields. This could mean these worlds are not as good at deflecting harmful electrically charged particles streaming from their red dwarfs and other stars that can damage organisms and strip off the atmospheres of these planets.

    The investigators suggested that dense atmospheres could help keep such planets habitable in the face of radiation from space. They added that life might be confined to certain spots on the surfaces of those planets that experience relatively safe levels of radiation.

    Are astronomers capable of detecting habitable planets with a 3:2 spin orbit resonance?

    “Measuring the day length of extrasolar planets is enormously difficult, and the first day length measurements for any extrasolar planets were only published this year,” Mead said. “Such a measurement for the planets we discuss would be much more difficult due to the fact that they are small, rocky planets around faint stars. This means that we are probably a long way from measuring the spin rates of such habitable worlds.”

    See the full article here.


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  • richardmitnick 8:35 pm on September 14, 2014 Permalink | Reply
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    From Astrobiology: “NASA Research Gives Guideline for Future Alien Life Search” 

    Astrobiology Magazine

    Astrobiology Magazine

    Sep 13, 2014
    At NASA
    William Steigerwald
    NASA’s Goddard Space Flight Center, Greenbelt, Maryland

    Gabriela Frias
    Universidad Nacional Autonoma de Mexico, Mexico City

    Astronomers searching the atmospheres of alien worlds for gases that might be produced by life can’t rely on the detection of just one type, such as oxygen, ozone, or methane, because in some cases these gases can be produced non-biologically, according to extensive simulations by researchers in the NASA Astrobiology Institute’s Virtual Planetary Laboratory.

    Left: Ozone molecules in a planet’s atmosphere could indicate biological activity, but ozone, carbon dioxide and carbon monoxide — without methane, is likely a false positive. Right: Ozone, oxygen, carbon dioxide and methane — without carbon monoxide, indicate a possible true positive. Image Credit: NASA

    The researchers carefully simulated the atmospheric chemistry of alien worlds devoid of life thousands of times over a period of more than four years, varying the atmospheric compositions and star types.

    “When we ran these calculations, we found that in some cases, there was a significant amount of ozone that built up in the atmosphere, despite there not being any oxygen flowing into the atmosphere,” said Shawn Domagal-Goldman of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “This has important implications for our future plans to look for life beyond Earth.”

    Methane is a carbon atom bound to four hydrogen atoms. On Earth, much of it is produced biologically (flatulent cows are a classic example), but it can also be made inorganically; for example, volcanoes at the bottom of the ocean can release the gas after it is produced by reactions of rocks with seawater.

    Ozone and oxygen were previously thought to be stronger biosignatures on their own. Ozone is three atoms of oxygen bound together. On Earth, it is produced when molecular oxygen (two oxygen atoms) and atomic oxygen (a single oxygen atom) combine, after the atomic oxygen is created by other reactions powered by sunlight or lightning. Life is the dominant source of the molecular oxygen on our planet, as the gas is produced by photosynthesis in plants and microscopic, single-cell organisms. Because life dominates the production of oxygen, and oxygen is needed for ozone, both gases were thought to be relatively strong biosignatures.

    But this study demonstrated that both molecular oxygen and ozone can be made without life when ultraviolet light breaks apart carbon dioxide (a carbon atom bound to two oxygen atoms). Their research suggests this non-biological process could create enough ozone for it to be detectable across space, so the detection of ozone by itself would not be a definitive sign of life.

    “However, our research strengthens the argument that methane and oxygen together, or methane and ozone together, are still strong signatures of life,” said Domagal-Goldman. “We tried really, really hard to make false-positive signals for life, and we did find some, but only for oxygen, ozone, or methane by themselves.”

    Credit: NASA Ames/SETI Institute/JPL-Caltech

    Domagal-Goldman and Antígona Segura from the Universidad Nacional Autónoma de México in Mexico City are lead authors of a paper about this research, along with astronomer Victoria Meadows, geologist Mark Claire, and Tyler Robison, an expert on what Earth would look like as an extrasolar planet. The paper appeared in the Astrophysical Journal Sept. 10, and is available online.

    Methane and oxygen molecules together are a reliable sign of biological activity because methane doesn’t last long in an atmosphere containing oxygen-bearing molecules. “It’s like college students and pizza,” says Domagal-Goldman. “If you see pizza in a room, and there are also college students in that room, chances are the pizza was freshly delivered, because the students will quickly eat the pizza. The same goes for methane and oxygen. If both are seen together in an atmosphere, the methane was freshly delivered because the oxygen will be part of a network of reactions that will consume the methane. You know the methane is being replenished. The best way to replenish methane in the presence of oxygen is with life. The opposite is true, as well. In order to keep the oxygen around in an atmosphere that has a lot of methane, you have to replenish the oxygen, and the best way to do that is with life.”

    Scientists have used computer models to simulate the atmospheric chemistry on planets beyond our solar system (exoplanets) before, and the team used a similar model in its research. However, the researchers also developed a program to automatically compute the calculations thousands of times, so they could see the results with a wider range of atmospheric compositions and star types.

    In doing these simulations, the team made sure they balanced the reactions that could put oxygen molecules in the atmosphere with the reactions that might remove them from the atmosphere. For example, oxygen can react with iron on the surface of a planet to make iron oxides; this is what gives most red rocks their color. A similar process has colored the dust on Mars, giving the Red Planet its distinctive hue. Calculating the appearance of a balanced atmosphere is important because this balance would allow the atmosphere to persist for geological time scales. Given that planetary lifetimes are measured in billions of years, it’s unlikely astronomers will happen by chance to be observing a planet during a temporary surge of oxygen or methane lasting just thousands or even millions of years.

    It was important to make the calculations for a wide variety of cases, because the non-biological production of oxygen is subject to both the atmospheric and stellar environment of the planet. If there are a lot of gases that consume oxygen, such as methane or hydrogen, then any oxygen or ozone produced will be destroyed in the atmosphere.

    However, if the amount of oxygen-consuming gases is vanishingly small, the oxygen and the ozone might stick around for a while. Likewise, the production and destruction of oxygen, ozone, and methane is driven by chemical reactions powered by light, making the type of star important to consider as well. Different types of stars produce the majority of their light at specific colors.

    For example, massive, hot stars or stars with frequent explosive activity produce more ultraviolet light. “If there is more ultraviolet light hitting the atmosphere, it will drive these photochemical reactions more efficiently,” said Domagal-Goldman. “More specifically, different colors (or wavelengths) of ultraviolet light can affect oxygen and ozone production and destruction in different ways.”

    Astronomers detect molecules in exoplanet atmospheres by measuring the colors of light from the star the exoplanet is orbiting. As this light passes through the exoplanet’s atmosphere, some of it is absorbed by atmospheric molecules. Different molecules absorb different colors of light, so astronomers use these absorption features as unique “signatures” of the type and quantity of molecules present.

    “One of the main challenges in identifying life signatures is to distinguish between the products of life and those compounds generated by geological processes or chemical reactions in the atmosphere. For that we need to understand not only how life may change a planet but how planets work and the characteristics of the stars that host such worlds”, said Segura.

    The team plans to use this research to make recommendations about the requirements for future space telescopes designed to search exoplanet atmospheres for signs of alien life.

    “Context is key – we can’t just look for oxygen, ozone, or methane alone,” says Domagal-Goldman. “To confirm life is making oxygen or ozone, you need to expand your wavelength range to include methane absorption features. Ideally, you’d also measure other gases like carbon dioxide and carbon monoxide [a molecule with one carbon atom and one oxygen atom]. So we’re thinking very carefully about the issues that could trip us up and give a false-positive signal, and the good news is by identifying them, we can create a good path to avoid the issues false positives could cause. We now know which measurements we need to make. The next step is figuring out what we need to build and how to build it.”

    See the full article here.


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  • richardmitnick 7:18 am on September 11, 2014 Permalink | Reply
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    From Astrobiology: “In the Zone. The Venus Zone: Seeking the Twin of our Twin Among the Stars” 

    Astrobiology Magazine

    Astrobiology Magazine

    Sep 10, 2014
    Sheyna E. Gifford

    What if, in our quest to find another Earth, we happen upon another Venus?

    We should celebrate, of course. Venus is often called Earth’s “twin” because it shares of lot of our home planet’s physical characteristics: surface area, composition and density. Also, roughly speaking, both planets inhabit the area around the Sun’s habitable zone – though Venus is near the inner edge, while we on Earth occupy the relative center. Bearing the similarities and differences in mind, scientists Ravi Kumar Kopparapu, Stephen Kane and Shawn Domagal-Goldman explored how distant analogs to Venus might be detected and differentiated from Earth-like planets occupying the same relative space. The paper pinpointing their finding was published in Astrophysical Journal Letters on 9/10/2014.

    Successfully detecting analogs of our inner planets out in the Universe, as Kopparapu and colleagues describe, means that at least two important events have taken place.

    One says something about us. At present, our ability to identify the existence of other planetary systems is increasing by the day. When it comes to divining which exoplanet is a mini-Neptune and which is a mega-Earth, we still have a ways to go. Gaining the ability to pick out Venus-like planets will imply that we have gotten really good at sorting exoplanets.

    The other is a larger statement about the Universe: If Venus-like planets are found in abundance, then Solar Systems like ours may be the rule rather than the exception. Discovering a twin to Venus around another star might well spark our interest in focusing our observations there, both for signs of another Earth and for clues about the dynamics of exoplanetary systems that harbor conditions similar to our own.

    In their paper, Kopparapu, Domagal-Goldman and Kane explain how we can determine the distance between a planet and a star from calculations we can make today. They project that in the near future, when the James Webb Space Telescope takes to the skies, measurements of exoplanetary atmospheres will distinguish Venus-like from Earth-like from Mars-like. In the meantime, Kane and colleagues made some important calculations that will assist astronomers in the search for distant Venuses.

    NASA Webb Telescope

    Not every planet in or near a habitable zone is habitable. Inhospitable Venus is an excellent example. Credit: NASA/JPL/Caltech

    First, they estimated how close a planet can be to a star and still retain its atmosphere. Those figures pertain to planets like Mercury, with close-in orbits where the Solar Wind strips away nearly all atmospheric particles. Then, they approximated the furthest distance from a star likely to sustain a planet-wide runaway greenhouse effect. Taken together, these parameters describe the Venus zone: a place where we can start looking for planets with characteristics of own second planet from the Sun.

    Before we move on to finding planets in other solar systems, we should talk a bit about our own Solar System. Here to do that and then discuss his findings is Dr. Shawn Domagal-Goldman, one of the paper’s authors and the mind behind The Pale Blue Blog at astrobio.net.

    Astrobiology Magazine (AM): Shawn, the discovery of just how much Earth and Venus differ is relatively recent. What did it take for us to figure out that our own twin in the Solar System was not just uninhabited, but utterly uninhabitable?

    Domagal-Goldman: This is one of the things we’ve learned through telescope and spacecraft observations of Venus over the last century or so. And this highlights two of the things I love about this paper – it leverages what we’ve learned about planets from observations of the ones in our own solar system to inform exoplanet data; and it also reinforces the notion that two planets with fairly Earth-like “astrophysical” properties such as mass/radius can be dramatically different in terms of their habitability.

    AM: Where is our own “Venus zone”?

    Domagal-Goldman: The outer edge of the “Venus zone” is, by the way we’ve defined it here, the same as the inner edge of the habitable zone. This is roughly the “border” between where we think a planet is more likely to be Venus (closer to the Sun than the border) or more like Earth (further from the Sun than the border). This border therefore is between Earth and Venus. The inner edge of the “Venus zone” is the distance at which Venus would lose it’s atmosphere from all high energy input from the Sun. In our system, this is VERY close to the Sun – about twice as close to the Sun as Mercury is.

    AM: We’re just beginning to find rocky planets in so-called habitable zones around other stars. Why is now a good time to start breaking up these habitable zones into discrete bands that reflect Earth and Venus? How will we be able to tell a Venus-zone from an Earth-zone at such tremendous distances? Will there be a Mars-zone as well, when all is said and done?

    In the present-day Solar System with the Sun in its current state, Venus is outside of the habitable zone (HZ) – or rather, it is closer to the Sun than the inner boundary of where water will be found in liquid form. The stability of water as a liquid sets the lines for the traditional habitable zone, outlined here in blue. However, for exoplantary systems with characteristics distinct from ours – where the stars exhibit different luminosity, the planets rotate differently, or the atmosphere conditions vary on those planets vary – the HZ will vary in size and distance from the star. Image Credit: NASA

    Domagal-Goldman:: There could be a Mars-zone, as well! But getting at that will require us to understand the degree to which Mars was habitable, for how long, and what caused the demise of the red planet’s habitability. These are all questions currently being explored by Curiosity, and we look forward to answers on all those topics.

    NASA Mars Curiosity
    NASA/Mars Curiosity

    Ultimately, these sorts of categorizations are going to be done better when we can analyze exoplanets in more detail with bigger future telescopes. The reason we’re doing all this now is for two reasons. First, this gives the community scientific hypotheses for us to test with that sort of mission. Second, it helps us design those missions, and prioritize which objects we would look at first when those missions happen.

    AM: The size and location of the Venus zone in each system is going to be dependent on a lot of factors: for example, the luminosity and size of the primary star. A white dwarf star will have a Venus zone much smaller and closer in than our Sun’s. What else will we need to consider in trying to size up Venus zones?

    Domagal-Goldman: The other thing that’s really needed now is more simulations of Venus-like atmospheres. This is something that’s very difficult to do, as Venus has been one of the planets that is most difficult to simulate in our computer models. Making advances in that will help us determine the boundaries of both the Venus zone and the habitable zone. Ultimately, we want to define these boundaries with observations from telescopes, but until that happens the best thing we can do will be to improve our simulations and use those results to refine the concept of the Venus zone.

    AM: The Kepler Space Telescope has been the workhorse of our planet-hunting mission thus far. When the James Webb takes to the skies, what will change, in terms of finding the Venus Zones, the Venus-analogs, the Earth-analogs and places where we should focus the search for life?

    NASA Kepler Telescope

    Domagal-Goldman: If we’re lucky, we’ll get a couple Venus-like candidates to study, as the first tests of the hypotheses in this paper. And if we’re extremely lucky, we may get a potentially habitable world or two for us to study, as well. That will be the first mission to move us from studying the “physics” of these planets to being able to study the “chemistry” for a large number of them. Eventually, with a future mission, the goal is to study the biology of such worlds.

    See the full article here.


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  • richardmitnick 7:19 am on September 10, 2014 Permalink | Reply
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    From SPACE.com: “What Is the Fermi Paradox?” 

    space-dot-com logo


    April 02, 2014
    Elizabeth Howell

    The Fermi Paradox seeks to answer the question of where the aliens are. Given that our star and Earth are part of a young planetary system compared to the rest of the universe — and that interstellar travel might be fairly easy to achieve — the theory says that Earth should have been visited by aliens already.

    As the story goes, Enrico Fermi (an Italian physicist) first came out with the theory with a casual lunchtime remark in 1950. The implications, however, have had extraterrestrial researchers scratching their heads in the decades since.

    “Fermi realized that any civilization with a modest amount of rocket technology and an immodest amount of imperial incentive could rapidly colonize the entire galaxy,” the Search For Extraterrestrial Intelligence (SETI) said on its website.

    “Within ten million years, every star system could be brought under the wing of empire. Ten million years may sound long, but in fact it’s quite short compared with the age of the galaxy, which is roughly ten thousand million years. Colonization of the Milky Way should be a quick exercise.”

    Plentiful planets

    It is true that the universe is incredibly vast and old. One estimate says the universe spans 92 billion light-years in diameter (while growing faster and faster). Separate measurements indicate it is about 13.82 billion light-years old. At first blush, this would give alien civilizations plenty of time to propagate, but then they would have a cosmic distance barrier to cross before getting too far into space.

    The sheer number of planets that we have found outside of our solar system, however, indicates that life could be plentiful. A November 2013 study using data from the Kepler Space Telescope suggested that one in five sun-like stars has an Earth-size planet orbiting in the habitable region of its star, the zone where liquid water would be possible. That zone is not necessarily an indication of life, as other factors, such as the planet’s atmosphere, come into play. Further, “life” could encompass anything from bacteria to starship-sailing extraterrestrials.

    NASA Kepler Telescope

    A few months later, Kepler scientists released a “planet bonanza” of 715 newly discovered worlds, pioneering a new technique called “verification by multiplicity.” The theory essentially postulates that a star that appears to have multiple objects crossing its face or tugging at it would have planets, as opposed to stars. (A multiple star system at such close proximity would destabilize over time, the technique postulates.) Using this will accelerate the pace of exoplanet discovery, NASA said in 2014.


    Our understanding of astrobiology (life in the universe) is just at a beginning, however. One challenge is these exoplanets are so far away that it is next to impossible for us to send a probe out to look at them. Another obstacle is even within our own solar system, we haven’t eliminated all the possible locations for life. We know from looking at Earth that microbes can survive in extreme temperatures and environments, giving rise to theories that we could find microbe-like life on Mars, the icy Jovian moon Europa, or perhaps Saturn’s Enceladus or Titan.

    All of this together means that even within our own Milky Way Galaxy — the equivalent of the cosmic neighborhood — there should be many Earth-size planets in habitable zones that could host life. But what are the odds of these worlds having starfarers in their bounds?

    Life: plentiful, or rare?

    The odds of intelligent life are estimated in the Drake Equation, which seeks to figure out the number of civilizations in the Milky Way that seek to communicate with each other. In the words of SETI, the equation (written as N = R* • fp • ne • fl • fi • fc • L) has the following variables:

    N = The number of civilizations in the Milky Way galaxy whose electromagnetic emissions are detectable.

    R* = The rate of formation of stars suitable for the development of intelligent life.

    fp = The fraction of those stars with planetary systems.

    ne = The number of planets, per solar system, with an environment suitable for life.

    fl = The fraction of suitable planets on which life actually appears.

    fi = The fraction of life bearing planets on which intelligent life emerges.

    fc = The fraction of civilizations that develop a technology that releases detectable signs of their existence into space.

    L = The length of time such civilizations release detectable signals into space.

    None of these values are known with any certainty right now, which makes predictions difficult for astrobiologists and extraterrestrial communicators alike.

    There is another possibility that would dampen the search for radio signals or alien spacecraft, however: that there is no life in the universe besides our own. While SETI’s Frank Drake and others suggested there could be 10,000 civilizations seeking communications in the galaxy, a 2011 study later published in the Proceedings of the National Academy of Sciences suggested that Earth could be a rare bird among planets.

    It took at least 3.5 billion years for intelligent life to evolve, the theory by Princeton University researchers David Spiegel and Edwin Turner said, which indicates it takes a lot of time and luck for this to happen.

    Other explanations for the Fermi paradox include extraterrestrials “spying” on Earth, ignoring it altogether, visiting it before civilization arose, or visiting it in a way that we can’t detect.

    See the full article here.

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  • richardmitnick 7:47 am on August 29, 2014 Permalink | Reply
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    From SETI Institute: “How Can We Find Tiny Particles In Exoplanet Atmospheres?” 

    SETI Institute

    August 28 2014

    Adrian Brown
    SETI Institute
    E-mail: abrown@seti.org
    Tel: +1 650 960-4223

    Seth Shostak, Media Contact
    SETI Institute
    E-mail: seth@seti.org
    Tel: +1 650 960-4530

    It may seem like magic, but astronomers have worked out a scheme that will allow them to detect and measure particles ten times smaller than the width of a human hair, even at many light-years distance. They can do this by observing a blue tint in the light from far-off objects caused by the way in which small particles, no more than a micron in size (one-thousandth of a millimeter) scatter light.

    Credit: NASA/JPL

    In a recent study conducted by Adrian Brown of the SETI Institute, the broad outlines of this process have been worked out. “The effect is related to a familiar phenomenon known as Rayleigh scattering,” says Brown. “And that’s something everyone has seen: it makes the sky blue.”

    By analyzing spectroscopic data from the Cassini orbiter, the Mars Reconnaissance Orbiter, and ground-based telescopes, Brown has managed to document this blue enhancement in many nearby objects, including the rings of Saturn, its moons Dione and Epimetheus, Mars, the moon, and the tail of Comet 17P/Holmes.

    NASA Cassini Spacecraft

    NASA/ Mars Reconnaissance Orbiter

    Brown’s theoretical study of the phenomenon showed that the spectral bluing occurs any time sufficiently small objects are in our field of view. In his studies, he considered particles between 0.1 and 1.0 microns in size. A human hair is roughly 17 microns in diameter.

    So why isn’t the ground beneath our feet blue? Brown’s research suggests that the effect is quickly damped by other objects that, despite being of the same type, have different size distributions. The effect depends on having many particles within a narrow range of size. In addition, too many tiny particles might turn objects white. As an example of the latter, a glass of milk appears white because of multiple scattering from fat globules, and clouds appear white due to multiple scattering from water aerosols (droplets).

    Consequently, the bluing effect requires some process that forms lots of particles of almost identical size. Simply establishing that such a process is present can give researchers clues to the history and conditions on extraterrestrial bodies.

    “This technique would, in principle, allow us to find extremely tiny particles in the atmospheres or on the surfaces of exoplanets that are tens or thousands of light-years away,” Brown says.

    The research was published in the September 1 issue of Icarus.

    See the full article here.

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  • richardmitnick 8:24 am on August 22, 2014 Permalink | Reply
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    From SPACE.com: “How to Search for E.T. by Scanning Alien Skies” 

    space-dot-com logo


    August 04, 2014
    Charles Q. Choi

    In the future, astronomers could detect hints of alien life by scanning the atmospheres of distant worlds with advanced space telescopes, researchers say.

    In the past two decades, astronomers have confirmed the existence of more than 1,700 worlds outside Earth’s solar system. Many of these alien planets lie in the habitable zones of stars, areas potentially warm enough for worlds to harbor liquid water of their surfaces. This has inspired hope that one day scientists might detect life as it is known on Earth on such exoplanets, since there is life pretty much everywhere water exists on Earth.

    The alien planet Kepler-186f is the first extrasolar world ever found to be about the size of Earth and in the habitable zone of its parent star. But if scientists ever hope to try to find life on such a planet, giant new space telescopes are needed, researchers say.
    Credit: NASA Ames/SETI Institute/JPL-Caltech

    “Astronomers have now ascertained, statistically speaking, that every star in our Milky Way galaxy should have at least one planet and that small rocky planets are extremely common,” planetary scientist Sara Seager of the Massachusetts Institute of Technology wrote in an analysis appearing online Monday (Aug. 4) in the journal Proceedings of the National Academy of Sciences.

    “Our own galaxy has 100 billion stars, and our universe has upwards of 100 billion galaxies, making the chance for life elsewhere seem inevitable based on sheer probability,” she added.

    One strategy to hunt for signs of such extraterrestrial life involves looking for ways that organisms might alter a world’s appearance. For example, key chemicals might change the spectrum of light seen from the atmospheres of those planets. These searches focus on biosignature gases — chemicals or combinations of chemicals that life could produce, but that processes other than life could not or would be unlikely to create.

    “In the coming decade or two, we will have a lucky handful of potentially habitable exoplanets with atmospheres that can be observed in detail with the next generation of sophisticated space telescopes,” Seager wrote.

    So far, astronomers have studied more than three dozen exoplanet atmospheres. These observations have yielded enough data for researchers to glimpse both the future prospects and limitations of the atmosphere-based method of searching for alien life. One challenge is that exoplanet atmospheres continue to surprise researchers. For instance, scientists have detected hazes and clouds on planets once thought too hot for such features to form.

    “The atmospheres of a few of the exoplanets we have looked at do not appear as expected,” Seager told Space.com. This suggests that researchers should try their best to expect the unexpected when building scientific instruments designed to analyze exoplanetary atmospheric compositions.

    In the near future, the James Webb Space Telescope (JWST), planned for launch in 2018, can study the atmospheres of dozens of super-Earths, exoplanets slightly larger than Earth. The observatory may even be able to scan a number of worlds that might be habitable.

    NASA Webb Telescope

    However, JWST will rely upon planetary “transits” to do such work, only scanning the atmospheres of planets that pass in front of their stars from the observatory’s perspective and are thus backlit by starlight. Ideally, researchers would like to scan exoplanet atmospheres by directly taking photos of the planets without having to wait for transits.

    The problem with such direct imaging of exoplanets is that any nearby Earthlike exoplanets or “Earth twins” would be about as faint as the faintest galaxies ever observed by the Hubble Space Telescope. However, these exoplanets are next to parent stars that are up to 10 billion times brighter than the planets themselves.

    NASA Hubble Telescope
    NASA/ESA Hubble

    “The challenge of direct imaging of an Earth analog is similar to the search for a firefly in the glare of a searchlight when the firefly and searchlight are 2,500 miles distant, the separation from the East Coast to the West Coast of the United States,” Seager wrote.

    To directly image Earth twins, researchers are currently pursuing two different strategies. One involves so-called internal coronographs, or systems within telescopes that can block out the light of stars to reveal the presence of any orbiting exoplanets. This requires mirrors that can focus starlight without scattering it; these reflectors must be smoothed to levels of less than a nanometer, or a billionth of a meter. (In comparison, the average human hair is about 100,000 nanometers wide.) Laboratory experiments have already demonstrated such a level of control, Seager noted.

    Another strategy to directly image Earth twins involves a starshade, a different system designed to hide the light of stars to reveal the presence of any orbiting exoplanets. However, a starshade does not fit inside a telescope; rather, it is a giant, sunflowerlike spacecraft. Most designs involve a starshade dozens of feet wide flying tens of thousands of miles in front of a telescope, carefully positioned to blot out the light of just one star at a time. Current lab experiments have created scaled-down versions of such devices that need to cast shadows about 10 times darker before they can find use in starshades.

    In the future, researchers could build very large space telescopes with apertures more than 33 feet (10 meters) wide capable of finding more than 100 potentially habitable exoplanets. The telescopes could then analyze those planets’ atmospheres for biosignature gases.

    “While we are closer than ever, it will still be a while before we have the capability to study small exoplanet atmospheres for biosignature gases,” Seager told Space.com.

    See the full article here.

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