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  • richardmitnick 12:06 pm on August 28, 2015 Permalink | Reply
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    From SPACE.com: “How to Find ‘Strange Life’ on Alien Planets” 

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    SPACE.com

    August 28, 2015
    Nola Taylor Redd

    1
    This artist’s rendition of the super-Earth GJ 1214b shows it in orbit around a dim red dwarf star. If the atmosphere is thick in hydrogen, scientists may be able to spot signs of alien life. Credit: CfA/David Aguilar

    Detecting signs of life very different from that of Earth in the atmospheres of alien planets may be difficult, but it is possible, researchers say.

    A team of scientists examined models of “super-Earths” — exoplanets slightly larger than Earth — to determine how easily signs of life could be spotted. They determined that such biosignatures could be identified more easily on planets orbiting stars producing relatively low amounts of radiation — but even then only if everything worked out just right.

    The team, led by Sara Seager of the Massachusetts Institute of Technology (MIT), did not focus solely on Earth-like life.

    “What we’ve been trying to do is move away from that,” William Bains, also of MIT, said during the Astrobiology Science Conference in Chicago in June. Bains worked with Seager and Renyu Hu to study super-Earths with hydrogen-rich atmospheres. “We wanted to build a model of biosignatures independent of Earth’s biology.”

    ‘A dynamic process’

    Super-Earths are worlds up to 10 times more massive than our planet. Because of their size, they are more likely to retain an atmosphere rich in molecular hydrogen. The girth of super-Earths also makes them easier to discover, and their atmospheres easier to characterize, relative to their Earth-size cousins. Hydrogen-rich super-Earths are now known to be quite common throughout the galaxy.

    Bains and his colleagues simulated a planet 10 times as massive and nearly twice as wide as Earth, with an atmosphere rich in molecular hydrogen. Their simulations placed the planet in an orbit around three different types of stars: a sunlike star, a normal red dwarf (a star smaller and dimmer than the sun) and and an especially inactive red dwarf. (Different stellar types produce different levels of ultraviolet radiation, with the sunlike star producing the most, which affects how molecules break down in the atmosphere of orbiting planets.)

    To search for biosignatures, Bains said, it’s important to understand why forms of life produce gas in the first place. Some gas is produced as a byproduct when energy is captured from the atmosphere. Other gases are byproducts of metabolic reactions, such as photosynthesis. The third type is created by life not as a result of its central chemical production but from stress, for signaling and in other functions.

    “Life is a dynamic process,” Bains said.

    The byproducts of life

    After determining what gases could survive in the atmosphere, the scientists then calculated how much biomass would be needed to produce a detectable amount, and whether or not such an amount of life would be reasonable to find.

    The team found four volatiles that would be generated by the production of energy in a hydrogen-rich atmosphere. Of them, three could be formed geologically, making them unreliable biosignatures.

    “This was really disappointing,” Bains said.

    The only interesting biosignature that the team came up in the first class was ammonia (NH3). For ammonia to be created, life would have to find a way to break the bonds between molecular nitrogen and molecular hydrogen. On Earth, synthetic chemistry can break each molecule apart individually, but no known system is capable of breaking both at once. Still, the team remains hopeful that a form of life could evolve on other worlds capable of capitalizing on the possibility.

    Producing a detectable amount of ammonia in the atmosphere of a distant super-Earth would require a layer of life less than one bacterial cell thick, researchers said.

    “Even if it was deader than the deadest place on Earth, we could detect it,” Bains said.

    That’s the case for super-Earths orbiting sunlike stars, anyway. For alien planets receiving lower levels of ultraviolet radiation, such as those orbiting standard or quiet red dwarfs, the required biomass would need to be significantly higher.

    While scientists should be able to detect ammonia in the atmosphere of distant planets, determining if it stems from life is another matter. At present, uncertainties about the size and mass of exoplanets remain high enough that worlds presently thought to be super-Earths could, in fact, be mini-Neptunes, gas giants smaller than those found in the solar system.

    Disregarding the fact that surface conditions on gas planets would be essentially nonexistent, the deep atmospheres could produce ammonia without the aid of life. Determining whether a planet is a super-Earth or a mini-Neptune requires probing atmospheric pressures near the surface, something that even NASA’s upcoming James Webb Space Telescope [JWST] will be unable to accomplish, researchers said.

    NASA Webb Telescope
    JWST

    Even if scientists could conclusively identify a planet as rocky, it’s possible that the world could have collected ammonia during its evolution, as Saturn’s moon, Titan, did. Ices on the surface could break down with either internal heat or with the help of ultraviolet radiation, releasing ammonia into the atmosphere to create a false positive.

    So, without getting up close to these distant worlds, characterizing whether ammonia in the atmosphere comes from life remains a significant challenge.

    The research that formed the basis of Bains’ talk at the astrobiology conference was published in late 2013 in The Astrophysical Journal.

    ‘In our favor’

    Seager, Bains and Hu also considered another group of gases — those produced for biomass building. Capturing energy from the environment requires energy. On Earth, a prime example is the oxygen plants release during the process of photosynthesis.

    Unfortunately, the team was unable to identify any potentially useful biosignature gases of this type in a hydrogen-rich atmosphere. The gases that life might produce would be expected to exist naturally in the atmosphere of such a world, Bains said.

    As a third option, the team examined molecules produced unrelated to energy generation. The presence of such gases would depend on the amount of ultraviolet (UV) radiation in the atmosphere, because high UV levels lead to the creation of lots of destructive hydrogen ions.

    Planets orbiting sunlike stars, which emit lots of UV light, would therefore need an enormous density of biomass to produce biosignatures high enough to reach detectable levels. Even around a normal red dwarf, the values would need to be high, though they could be plausible when compared to Earth’s biomass surface density range.

    According to the team, the James Webb Space Telescope (JWST) could spot evidence of biosignatures gas “if and only if every single factor is in our favor.”

    Detecting life using JWST would require a pool of transiting planets around nearby red dwarfs. Because the stars are so dim, they would need to be relatively close to Earth in order for scientists to study their planets. These planets would need a molecular hydrogen atmosphere, which would be easier to study than a more Earth-like atmosphere. The star itself would need to be quiet, with little radiation. Finally, the planet itself must have life that produces a detectable gas as a biosignature.

    “We will have the ability to predict some biosignatures gas independent of Earth,” Bains said. “But it’s going to be really hard to detect.”

    See the full article here.

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  • richardmitnick 11:13 am on August 28, 2015 Permalink | Reply
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    From SPACE.com- ” Incredible Technology: How to See a Black Hole” Very Old, But Very Worth Your Time 

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    July 08, 2013
    Clara Moskowitz

    1
    Theoretical calculations predict that the Milky Way’s central black hole, called Sagittarius A*, will look like this when imaged by the Event Horizon Telescope. The false-color image shows light radiated by gas swirling around and into a black hole. The dark region in the middle is the “black hole shadow,” caused by the black hole bending light around it.
    Credit: Dexter, J., Agol, E., Fragile, P. C., McKinney, J. C., 2010, The Astrophysical Journal, 717, 1092.

    Black holes are essentially invisible, but astronomers are developing technology to image the immediate surroundings of these enigmas like never before. Within a few years, experts say, scientists may have the first-ever picture of the environment around a black hole, and could even spot the theorized “shadow” of a black hole itself.

    Black holes are hard to see in detail because the large ones are all far away. The closest supermassive black hole is the one thought to inhabit the center of the Milky Way, called Sagittarius A* (pronounced “Sagittarius A-star”), which lies about 26,000 light-years away.

    1
    Sagittarius A*. This image was taken with NASA’s Chandra X-Ray Observatory. Ellipses indicate light echoes.
    Date 23 July 2014

    NASA Chandra Telescope
    NASA/Chandra

    This is the first target for an ambitious international project to image a black hole in greater detail than ever before, called the Event Horizon Telescope (EHT).

    Event Horizon Telescope
    Event Horizon Telescope map
    EHT and EHT Map

    The EHT will combine observations from telescopes all over the world, including facilities in the United States, Mexico, Chile, France, Greenland and the South Pole, into one virtual image with a resolution equal to what would be achieved by a single telescope the size of the distance between the separated facilities.

    “This is really an unprecedented, unique experiment,” said EHT team member Jason Dexter, an astrophysical theorist at the University of California, Berkeley. “It’s going to give us more direct information than we’ve ever had to understand what happens extremely close to black holes. It’s very exciting, and this project is really going to come of age and start delivering amazing results in the next few years.”

    From Earth, Sagittarius A* looks about as big as a grapefruit would on the moon. When the Event Horizon Telescope is fully realized, it should be able to resolve details about the size of a golf ball on the moon. That’s close enough to see the light emitted by gas as it spirals in toward its doom inside the black hole.

    Very long baseline interferometry

    To accomplish such fine resolution, the project takes advantage of a technique called very long baseline interferometry (VLBI). In VLBI, a supercomputer acts as a giant telescope lens, in effect.

    “If you have telescopes around the world you can make a virtual Earth-sized telescope,” said Shep Doeleman, an astronomer at MIT’s Haystack Observatory in Massachusetts who’s leading the Event Horizon Telescope project. “In a typical telescope, light bounces off a precisely curved surface and all the light gets focused into a focal plane. The way VLBI works is, we have to freeze the light, capture it, record it perfectly faithfully on the recording system, then shift the data back to a central supercomputer, which compares the light from California and Hawaii and the other locations, and synthesizes it. The lens becomes a supercomputer here at MIT.”

    A major improvement to the Event Horizon Telescope’s imaging ability will come when the 64 radio dishes of the ALMA (Atacama Large Millimeter/submillimeter Array) observatory in Chile join the project in the next few years.

    ALMA Array
    ALMA Array

    “It’s going to increase the sensitivity of the Event Horizon Telescope by a factor of 10,” Doeleman said. “Whenever you change something by an order of magnitude, wonderful things happen.”

    Very long baseline interferometry has been used for about 50 years, but never before at such a high frequency, or short wavelength, of light. This short-wavelength light is what’s needed to achieve the angular resolution required to measure and image black holes.

    South Pole Telescope [SPT]

    The South Pole Telescope will join the Event Horizon Telescope project in coming years to image the area around the black hole at the center of the Milky Way.

    South Pole Telescope
    SPT

    Grand technical challenge

    Pulling off the Event Horizon Telescope has been a grand technical challenge on many fronts.

    To coordinate the observations of so many telescopes spread out around the world, scientists have needed to harness specialized computing algorithms, not to mention powerful supercomputers. Plus, to accommodate the time difference between the various stations, extremely accurate clocks are needed.

    See the full article here.

    Additional:
    Event Horizon Telescope
    Event Horizon Telescope Science

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  • richardmitnick 5:37 pm on August 22, 2015 Permalink | Reply
    Tags: , , Lagrange points, space.com   

    From SPACE.com: “Lagrange Points: Parking Places in Space” 

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    August 19, 2015
    Elizabeth Howell

    1
    Diagram of the Lagrange points associated with the sun-Earth system

    A Lagrange point is a location in space where the combined gravitational forces of two large bodies, such as Earth and the sun or Earth and the moon, equal the centrifugal force felt by a much smaller third body. The interaction of the forces creates a point of equilibrium where a spacecraft may be “parked” to make observations.

    These points are named after Joseph-Louis Lagrange, an 18th-century mathematician who wrote about them in a 1772 paper concerning what he called the “three-body problem.” They are also called Lagrangian points and libration points.

    Structure of Lagrange points

    There are five Lagrange points around major bodies such as a planet or a star. Three of them lie along the line connecting the two large bodies. In the Earth-sun system, for example, the first point, L1, lies between Earth and the sun at about 1 million miles from Earth. L1 gets an uninterrupted view of the sun, and is currently occupied by the Solar and Heliospheric Observatory (SOHO) and the Deep Space Climate Observatory.

    NASA SOHO
    NASA/SOHO

    NASA DSCOVR
    NASA/DSCOVR

    L2 also lies a million miles from Earth, but in the opposite direction of the sun. At this point, with the Earth, moon and sun behind it, a spacecraft can get a clear view of deep space. NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) is currently at this spot measuring the cosmic background radiation left over from the Big Bang. The James Webb Space Telescope will move into this region in 2018.

    WMAP
    NASA/WMAP

    NASA James Webb Telescope
    NASA/Webb

    The third Lagrange point, L3, lies behind the sun, opposite Earth’s orbit. For now, science has not found a use for this spot, although science fiction has.

    “NASA is unlikely to find any use for the L3 point since it remains hidden behind the sun at all times,” NASA wrote on a web page about Lagrange points. “The idea of a hidden ‘Planet-X’ at the L3 point has been a popular topic in science fiction writing. The instability of Planet X’s orbit (on a time scale of 150 years) didn’t stop Hollywood from turning out classics like ‘The Man from Planet X.’”

    L1, L2 and L3 are all unstable points with precarious equilibrium. If a spacecraft at L3 drifted toward or away from Earth, it would fall irreversibly toward the sun or Earth, “like a barely balanced cart atop a steep hill,” according to astronomer Neil DeGrasse Tyson. Spacecraft must make slight adjustments to maintain their orbits.

    Points L4 and L5, however, are stable, “like a ball in a large bowl,” according to the European Space Agency. These points lie along Earth’s orbit at 60 degrees ahead of and behind Earth, forming the apex of two equilateral triangles that have the large masses (Earth and the sun, for example) as their vertices.

    Because of the stability of these points, dust and asteroids tend to accumulate in these regions. Asteroids that surround the L4 and L5 points are called Trojans in honor of the asteroids Agamemnon, Achilles and Hector (all characters in the story of the siege of Troy) that are between Jupiter and the Sun. NASA states that there have been thousands of these types of asteroids found in our solar system, including Earth’s only known Trojan asteroid, 2010 TK7.

    5
    Asteroid 2010 TK7 is circled in green, in this single frame taken by NASA’s Wide-field Infrared Survey Explorer, or WISE. The majority of the other dots are stars or galaxies far beyond our solar system. Astronomers discovered this object — the first known Earth Trojan asteroid — after sifting through asteroid candidates identified by WISE.
    Date October 2010
    Author NASA/Jet Propulsion Lab-Caltech/UCLA

    L4 and L5 are also possible points for a space colony due to their relative proximity to Earth, at least according to the writings of Gerard O’Neill and related thinkers. In the 1970s and 1980s, a group called the L5 Society promoted this idea among its members. In the late 1980s, it merged into a group that is now known as the National Space Society, an advocacy organization that promotes the idea of forming civilizations beyond Earth.

    If a spacecraft uses a Lagrange point close to Earth, there are many benefits to the location, the Jet Propulsion Laboratory’s Amy Mainzer told Space.com.

    Mainzer is principal investigator of NEOWISE, a mission that searches for near-Earth asteroids using the Wide-field Infrared Survey Explorer (WISE) spacecraft that orbits close to our planet. While WISE is doing well with its current three-year mission that concludes in 2016, Mainzer said, a spacecraft placed at a Lagrange point would be able to do more.

    Far from the interfering heat and light of the sun, an asteroid-hunting spacecraft at a Lagrange point would be more sensitive to the tiny infrared signals from asteroids. It could point over a wide range of directions, except very close to the sun. And it wouldn’t need coolant to stay cool, as WISE required for the first phase of its mission between 2009 and 2011 — the location itself would allow for natural cooling. The James Webb Space Telescope will take advantage of the thermal environment at the sun-Earth L2 point to help keep cool.

    L1 and L2 also “allow you to have enormous bandwidth” because over conventional Ka-band radio, the communication speeds are very high, Mainzer said. “Otherwise, the data rates just become very slow,” she said, since a spacecraft in orbit around the sun (known as heliocentric orbit) would eventually drift far from Earth.

    See the full article here.

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  • richardmitnick 9:01 am on August 21, 2015 Permalink | Reply
    Tags: , , Galaxies, Habitable planets, space.com   

    From SPACE.com: Giant Galaxies May Be Better Cradles for Habitable Planets 

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    August 21, 2015
    Charles Q. Choi

    1
    This map shows the full extent of the Milky Way galaxy – a spiral galaxy of at least two hundred billion stars. Our Sun is buried deep within the Orion Arm about 26 000 light years from the centre. Towards the centre of the Galaxy the stars are packed together much closer than they are where we live. Notice also the presence of small globular clusters of stars which lie well outside the plane of the Galaxy, and notice too the presence of a nearby dwarf galaxy – the Sagittarius dwarf – which is slowly being swallowed up by our own galaxy. From http://www.atlasoftheuniverse.com/galaxy.html

    Galaxies like the Milky Way may not be the best cradles of life in the universe — giant galaxies devoid of newborn stars and at least twice as massive as the Milky Way could host 10,000 times more habitable planets, researchers say.

    In the past 20 years, astronomers have confirmed the existence of nearly 1,900 planets that orbit stars other than our sun. These findings have led researchers to speculate which moons, planets and stars might be the best at supporting recognizable forms of life. Scientists have even investigated whether there might be a galactic habitable zone in the Milky Way — a region of the galaxy favorable to the formation and evolution of habitable worlds.

    Now, researchers have analyzed more than 140,000 neighboring galaxies to answer the question, “Which type of galaxy might be the most habitable in terms of complex life in the cosmos?”

    One potentially surprising conclusion? The number of habitable planets is not the largest in spiral galaxies like ours, study co-author Anupam Mazumdar, a particle cosmologist at Lancaster University in England, told Space.com.

    The researchers suggested three criteria that might be important in determining a galaxy’s habitability. The first was the total mass of their stars, representing potential homes to planets. The next was the amount of mass in “metals” they had — elements heavier than hydrogen and helium — since this kind of matter is needed to build worlds as well as life as it is known on Earth. The last was their ongoing rate of star formation, since galaxies with high star-formation rateswould pack stars closer together, increasing the chance that any stars with habitable worlds might dwell near massive stars that will eventually die in supernovas that can trigger mass extinctions.

    “This is the first computation ever where we are discussing life in cosmological scales, and not within our own galaxy,” Mazumdar said. “It is fair to say that our paper is the first ‘cosmobiology’ paper, which has perhaps opened a new avenue to understand habitability in the cosmos.”

    The scientists investigated galaxies that astronomers have observed using the Apache Point Observatory in New Mexico as part of the Sloan Digital Sky Survey.

    SDSS Telescope
    SDSS telescope at Apache Point, NM, USA

    About 1,800 of these 140,000 galaxies are comparable to the Milky Way in terms of total mass in stars and ongoing star-formation rates, Mazumdar said. (The Milky Way weighs as much as about 60 billion suns, and gives birth to about three suns per year, the researchers noted.)

    They found that the most habitable kind of galaxy was the metal-rich type at least twice as massive as the Milky Way with less than a tenth of its star-formation rate. In fact, the researchers said this type of galaxy can host 10,000 times as many Earth-like planets as the Milky Way. Such galaxies could also host 1 million times more gas giants, which can, in turn, host potentially habitable moons, the researchers added.

    “The most important implication of our analysis is that our cosmos is actually full of life,” Mazumdar said.

    However, don’t expect astronauts to visit such galaxies anytime soon. The nearest such galaxy is Maffei 1, discovered in 1968, which lies more than 9.5 million light-years from Earth.

    3
    Maffei 1

    About 200 ofthe 140,000 galaxies analyzed were the potentially life-rich kind the scientists defined. Such galaxies are relatively shapeless. “Perhaps they are not eye-catching, looking at their pictures, but they are key to understanding extragalactic life in our universe,” Mazumdar said.

    In the future, computer simulations of these galaxies could investigate where their habitable planets are located, Mazumdar said. He and his colleagues detailed their findings in a paper accepted for publication in Astrophysical Journal Letters.

    See the full article here.

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  • richardmitnick 8:57 am on August 18, 2015 Permalink | Reply
    Tags: , ISS, space.com   

    From SPACE.com: “NASA Extracting Tanks from Retired Shuttle Endeavour for Use on Space Station” 

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    August 17, 2015
    Robert Z. Pearlman

    1
    Photo showing the potable and waste water storage tanks on the lower deck of the space shuttle. The California Science Center is letting NASA remove the tanks from inside the shuttle Endeavour for use aboard the International Space Station. Credit: National Archives via collectSPACE.com

    NASA’s space shuttle Endeavour, retired and on exhibit in Los Angeles for the past three years, has been called back into service — or rather, parts of it have — for the benefit of the International Space Station.

    A NASA team working this week at the California Science Center will remove four tanks from deep inside the winged orbiter to comprise a water storage system for the space station. The reactivated artifacts are intended to help free more crew time for science operations onboard the orbiting outpost by reducing the astronauts’ involvement in refilling their water reserves.

    “The ISS [International Space Station] program has been steadily increasing the amount of crew time dedicated to science and technology development [onboard the station] through initiatives like the water storage system,” NASA told Endeavour’s curators at the California Science Center, according to information shared exclusively with collectSPACE.com.

    Reusing the orbiter’s tanks, rather than manufacturing new hardware, will “reduce the overall cost of building the water storage system,” NASA said.

    When space shuttle Endeavour was still flying, the same tanks were used not only to provide drinking water for the orbiter’s crew but to also fill storage bags to provide water for the space station’s crew. Similar duffle-like, soft bags are still in use today to hold the water processed through the orbiting outpost’s recycling system, which purifies the crew’s urine, perspiration and other waste water so that it is drinkable again.

    But refilling those bags is more time consuming than if the station were to have a more capable reserve. Endeavour’s water tanks can hold a total of 300 liters, enough for about 25 to 27 days.

    Taking out the tanks

    Each of Endeavour’s potable water tanks measures 3 feet long by 1.3 feet wide (0.9 by 0.4 m) and weighs 40 pounds empty (18 kg). Together with a single waste water tank of similar dimensions, they are located underneath the crew cabin’s lower living space called the mid-deck.

    Workers will enter the orbiter, which is exhibited inside the science center’s Samuel Oschin Display Pavilion, through the same hatch that was used by the astronauts to enter and exit the space shuttle before launch and after landing. The hatch is normally kept closed as the center’s visitors are not allowed to tour inside the vehicle.

    Using a lift to reach the hatch, the NASA workers will gain access the tanks through the mid-deck’s floor. Under the seats where mission specialists sat for launch and landing is a locker that held the lithium hydroxide (LiOH) canisters used to clean the orbiter’s air of carbon dioxide. Unbolting and lifting out that container offers a pathway to drop down below the deck.

    From there, it is the relatively simple task of detaching the plumbing and electrical connectors that lead to each tank and unbolting the four tanks themselves from the rails that held them in place.

    The pavilion will remain open to science center visitors as the work completed, which is expected by Friday. The four tanks will then be shipped to the Kennedy Space Center in Florida.

    How and when the new water storage system will be flown to the space station was not specified.

    Preservation vs. program

    In 2011, at the end of its 30-year shuttle program, NASA handed over Endeavour to the California Science Center. The L.A. museum and educational complex is working to exhibit the orbiter standing upright, mounted as it was for launch with the last remaining external tank built for flight and a pair of solid rocket boosters.

    The exhibit, which will stand in the science center’s yet-to-be-built Samuel Oschin Air and Space Center, is expected to open in 2018.

    Before delivering Endeavour to California, NASA prepared the orbiter to be safe for public exhibit and removed some of its parts, like the shuttle’s three main engines, for future use with its heavy-lift rocket, the Space Launch System. But the agency needed the science center’s permission to remove the four water tanks, as the space shuttle is now the museum’s property.

    Temp 1
    Space shuttle Endeavour, as currently exhibited by the California Science Center, will donate its four water tanks to support the International Space Station.
    Credit: collectSPACE

    It is not without precedent for NASA to retrieve its former parts from museums to support its on-going programs, but it is rare.

    In 2013, for example, the space agency borrowed from the Smithsonian a gas generator out of an Apollo Saturn V F-1 engine and fired up another retrieved from an F-1 engine displayed at the Marshall Space Flight Center in Alabama, in support of developing a new engine.

    NASA also temporarily removed parts from the prototype orbiter Enterprise, now on display at the Intrepid Sea, Air and Space Museum in New York City, to help in its tests following the loss of the space shuttle Columbia in 2003.

    See the full article here.

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  • richardmitnick 3:13 pm on August 14, 2015 Permalink | Reply
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    From SPACE.com: “Why Magnetars Should Freak You Out” 

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    August 14, 2015
    Paul Sutter

    1
    Artist’s impression of the magnetar in star cluster Westerlund 1. Credit: ESO/L. Calçada

    I’ll be honest: Magnetars freak me out. But to get to the “why,” I have to explain the “what.” Magnetars are a special kind of neutron star, and neutron stars are a special kind of dead star.

    They’re easy enough to make — if you’re a massive star. All stars fuse hydrogen into helium deep in their cores. The energy released supports the stars against the crushing weight of their own gravity and, as a handy byproduct, provides the warmth and light necessary for life on any orbiting planets. But eventually, that fuel in the core runs out, allowing gravity to temporarily win and crush the star’s core even tighter.

    With the greater pressure, it becomes helium’s turn to fuse, combining into oxygen and carbon, until the helium, too, gives out. That’s where our own sun gets off the fusion train, but more massive stars can keep on chugging along, climbing up the periodic table in ever more intense and short-lived reaction phases, all the way up to nickel and iron.

    Once that solid lump of nickel and iron forms in the stellar core, a lot of things go haywire — fast. There’s still a lot of star stuff left in the atmosphere, pressing into that core, but further fusion doesn’t release energy, so there’s nothing left to prevent collapse.

    And collapse it does: The nickel and iron nuclei (yes, just nuclei; don’t even think about entire atoms at these temperatures and pressures) break apart. They just can’t handle this nuclear mosh pit. Stray electrons get shoved into the nearest protons, converting them to neutrons. The neutrons … stay neutrons. And those neutrons are mighty good at preventing further collapse, for reasons I’ll explain in a bit. The infalling gas, trying to crush the core into oblivion, bounces off that neutron core and goes kablamo! (Note: I don’t know what it actually sounds like.)

    The neutron ball

    What happens during the supernova event is an exciting discussion for another day. What we’re concerned with now is the leftovers: a soupy, ball-like mixture of neutrons and a few straggler protons. This ball is supported against its own weight by “degeneracy pressure,” which is a fancy way of saying that you can only pack so many neutrons in box — or, in this case, a ball. It may seem obvious that neutrons, well, take up space, but things didn’t have to turn out this way. It’s this degeneracy pressure that causes the big bounce that puts the super in supernova.

    I should note that, if there’s still too much stuff left hanging out around this leftover neutron ball, the weight can overwhelm even degeneracy pressure. And now, look what you’ve done: You’ve gone and made a black hole. But that, too, is another story. We wouldn’t want to be like our poor star and get overwhelmed.

    The neutron ball — which I should now call by its proper name, a neutron star — is weird. Seriously, that’s the best word I can find to describe it. Neutron stars are basically city-size atomic nuclei, which makes them among the densest things in the universe. The pressure of gravity inside these stars has squeezed apart even atomic nuclei, allowing their bits to float freely.

    It’s mostly neutrons down there — hence the name — but there are also a few surviving protons floating around. Normally, those protons would repel one another, being like-minded charges and all, but they are forced close together as the Strong Nuclear Force tries to bunch them up with their fellow neutrons.

    The neutron star’s interior is a complicated dance of physics under extreme conditions, resulting in very odd structures. The oddity starts near the surface, with blobs of a few hundred neutrons that are best described as neutron gnocchi. Below that, the neutron blobs glue together into long chains. We have entered the spaghetti layer. Underneath that, at even more extreme pressures, the spaghetti strands fuse side by side and form lasagna sheets. Under it all, even neutron lasagna loses its shape, becoming a uniform mass. But that mass has gaps in it, in the form of long tubes. At last: delicious penne.

    I wish I were making these names up, but physicists must be especially hungry people when coming up with metaphors.

    Did I mention the spinning? Oh yes, neutron stars spin, up to a few hundred times per second. Let all of this sink in for a bit: An object with such strong gravity that “hills” are barely a few millimeters tall, rotating with a speed that could rival your kitchen blender. We’re not playing games anymore.

    Neutron stars are scary

    All this action — the insane densities, the complicated structures, the ridiculously fast rotation rates — means that neutron stars carry some pretty nasty magnetic fields. But don’t magnetic fields require charged particles, and aren’t neutrons neutral? That’s true, smartypants, but there are still a few protons hanging out in the star, and at these incredible densities, physics gets … complicated. So, yes: Neutron stars, despite their name, can carry magnetic fields.

    How strong? Take a star’s normal magnetic field, and squish it down. Every time you squish, you get a stronger field, just as you get higher densities. And we’re squishing something from star-size (a million kilometers or miles, take your pick) to city-size (like, 25 kilometers — just 15 miles). Plus, with all the interesting physics happening in the interiors, complex processes can operate to amplify the magnetic field, so you can imagine just how strong those fields get.

    Actually, you don’t have to imagine, because I’m about to tell you. Let’s start with something familiar: the Earth’s magnetic field. That’s around 1 gauss. It’s not much different for the sun: a few to a few hundred gauss, depending on where on the surface you are. An MRI? 10,000 gauss. The strongest human-made magnetic fields are about a few hundred thousand gauss. In fact, we can’t make magnetic fields stronger than a million gauss or so without our machines just breaking down from the stress.

    Let’s cut to the chase: A neutron star carries a whopping trillion-gauss magnetic field. You read that right — “trillion,” with a “t.”

    Enter the magnetar

    Now, we finally get to magnetars. You may guess from the name that they’re especially magnetic: up to 1 quadrillion gauss. That’s 1,000 trillion times stronger than the magnetic field you’re sitting in right now. That puts magnetars in the No. 1 spot, reigning champions in the universal Strongest Magnetic Field competition. The numbers are there, but it’s hard to wrap our brains around them.

    Those fields are strong enough to wreak havoc on their local environments. You know how atoms are made of a positively charged nucleus surrounded by negatively charged electrons? Those charges respond to magnetic fields. Not very much under normal conditions, but this ain’t Kansas anymore, is it, Toto? Any unlucky atoms stretch into pencil-thin rods near these magnetars.

    It doesn’t stop there. With the atoms all screwed up, normal molecular chemistry is just a no-go. Covalent bonds? Ha! And the magnetic fields can drive enormous bursts of high-intensity radiation. So, generally bad business.

    Get too close to one (say, within 1,000 kilometers, or about 600 miles), and the magnetic fields are strong enough to upset not just your bioelectricity — rendering your nerve impulses hilariously useless — but your very molecular structure. In a magnetar’s field, you just kind of … dissolve.

    We’re not exactly sure what makes magnetars so frighteningly magnetic. Like I said, the physics of neutron stars is a little bit sketchy. It does seem, though, that magnetars don’t last long, and after 10,000 years (give or take), they settle down into a long-term normal neutron-star retirement: still insanely dense, still freaky magnetic, just…not so bad.

    So, as scary as they are, at least they won’t stay that way for long.

    See the full article here.

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  • richardmitnick 10:10 am on August 4, 2015 Permalink | Reply
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    From SPACE.com: “3D Supernova Simulation Turns Back Clock on Star Explosions” 

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    SPACE.com

    August 03, 2015
    Sarah Lewin

    1
    This visualization depicts a massive star about to collapse and explode into a supernova. Researchers found in the new simulation that the wrinkles that develop just before collapse are crucial to detonation. Credit: S. M. Couch

    Enormous stars collapse in ultramassive supernova explosions — now in 3D! For the first time ever, researchers have turned back the clock on a star’s final moments to simulate how wrinkles in its violent collapse trigger a vast explosion.

    As massive stars age, they build up more and more iron in their cores, which cannot be used by the star as fuel. Eventually, when the core gets big enough, it collapses and, sometimes, incites a huge explosion. Most simulations start with a star already on the brink of collapse, with the different layers inside the star in perfect concentric rings. But models with those simplified starting conditions stubbornly refuse to blow.

    “Almost all supernova simulations follow about 1 second of physical time,” said Sean Couch, a physicist and astronomer at Michigan State University and lead author of the new paper. “What we did that was different is, we wound the clock back 3 minutes. That’s really challenging; it’s never been done before. We then show this has an important and big impact on the likelihood for successful supernova explosions.”

    Such a feat was very technologically demanding, but it proved necessary because models starting right at the collapse just wouldn’t explode in a supernova, Couch said. Instead, the shock would peter out, and the collapsing star would become a black hole.

    “It’s the difference between an onion” — the old, simplified starting point — “and cabbage,” Couch told Space.com. “You slice cabbage, and there’s wrinkles on the inside. It’s still basically a sphere, but it’s not nearly as concentrically layered as the onion will be.”

    Those extra few moments, where the “onion” model had the chance to wrinkle into a “cabbage” more like a complex, real star before collapsing, seem to cause enough turbulence to push the system over the edge into a supernova.

    Just modeling those extra 3 minutes back in time was a huge technological challenge, Couch said — the simulation on the supercomputer took about one month to complete, and they could run it only once. Therefore, the researchers chose their star carefully: one about 12 million years old, and 15 times the mass of the sun, that they thought would likely go supernova.

    To extend their research, the scientists are modeling four types of stars they think might lead to supernovas, and they’re hoping to push the simulation even further back in time. Couch said it might be possible to understand and model the forces within a star, to go as far as an hour before the collapse. (“An epic challenge,” Couch called it.)

    The difficulty with modeling stars is the difference in timescales, Couch said — a star evolves over the course of millions of years, but the supernova mechanism is on a millisecond scale. Incredible levels of precision and complexity are needed to understand that millisecond.

    “We know that we’ve been working with unrealistic initial conditions; it’s just only come to light in the last couple of years that it matters,” Couch said. “What we’re learning now is that the details of these stars matter.”

    The research was detailed in the July 21 edition of The Astrophysical Journal.

    See the full article here.

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  • richardmitnick 12:39 pm on August 3, 2015 Permalink | Reply
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    From SPACE.com: “‘Snowball Earth’ Might Be Slushy” 

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    SPACE.com

    August 03, 2015
    Michael Schirber, Astrobiology Magazine

    1
    Ice Ages that covered much of the world in glaciers is thought have occurred twice during the Cryogenian period, between about 720 and 660 million years ago, and again from 650 to 640 million years ago. Credit: NSF

    Imagine a world without liquid water — just solid ice in all directions. It would certainly not be a place that most life forms would like to live.

    And yet our planet has gone through several frozen periods, in which a runaway climate effect led to global, or near global, ice cover. The last of these so-called “Snowball Earth” glaciations ended around 635 million years ago when complex life was just starting to develop. It’s still uncertain if ice blanketed the entire planet, or if some mechanism was able to halt the runaway.

    “Studying Snowball Earth glaciations can tell us just how bad it can get, in which case life as we know it would probably not survive,” says geologist Linda Sohl of Columbia University.

    Sohl and her colleagues are taking global climate models — the ones most people use to predict where our planet is heading in the future — and modifying them to study where our planet has been in the past.

    In their simulations of the Cryogenian period (850-635 million years ago), the group has found that the Earth’s global mean temperature could have fallen 12 degrees Celsius below freezing, and yet the world would not completely freeze over. The models predict that half of the oceans remain ice-free even under these extreme conditions. The implication is that Earth resisted snowballing into a solid ice ball at this crucial point in Earth’s history.

    The team has received a grant from the Exobiology & Evolutionary Biology element of the NASA Astrobiology Program to explore other Snowball Earth scenarios. The goal is to identify which factors, such as the arrangement of continents and ocean circulation, play a role in driving glaciation or halting it.

    The results could influence discussions on the limits of habitability around other stars. Water-bearing planets like Earth may carry some natural defense mechanism against global freezing, and this might mean liquid water is more common in the Universe than astrobiologists have traditionally assumed.

    Hard or slushy

    Scientists contend that at least two Snowball Earth glaciations occurred during the Cryogenian period, roughly 640 and 710 million years ago. Each lasted about 10 million years or so.

    The main evidence of the severity of these events comes from geological evidence of glaciers near the equator. If ice on land made it down to the low latitudes, as the argument goes, then it must have gone everywhere.

    This “all in” climate response is due to the high reflectivity, or albedo, of ice. Ice reflects 55 to 80 percent of incoming sunlight, sending that energy back into space before it can warm the planet. By comparison, ocean water reflects just 12 percent, and land areas reflect between 10 and 40 percent, so more of the sun’s heat is absorbed by these surface conditions. An additional factor in cooling the planet is that the Sun was 6 percent fainter during the Cryogenian period than it is now.

    Early models showed that once ice reached tropical latitudes, a positive feedback loop would take hold, in which ice cover would lead to lower temperatures, which would add more ice cover, which would lower temperatures even more. This runaway effect would presumably continue until the entire planet froze over, with even the oceans covered with as much as a kilometer-thick layer of ice.

    This so-called “hard snowball” would lock the planet into an eternal winter, à la the Disney hit, “Frozen.” The difference is that no magical spells exist to release a Snowball Earth from such a deep freeze.

    Indeed, scientists have had a hard time explaining how a hard snowball could ever thaw. One proposal is that volcanic activity releases greenhouse gases that eventually warm the planet back up. The amount of carbon dioxide (CO2) needed might be several hundred times higher than what our atmosphere contains now. However, there is no geologic evidence to support that much CO2 in the Cryogenian atmosphere, Sohl says.

    Another problem for the hard snowball theory is the lack of a massive extinction event in the Cryogenian fossil record. One would expect a major hit to the ocean ecosystem when it presumably got cut off from the Sun by a thick layer of ice, but only relatively small extinctions have been found.

    A further complication is evidence of an ongoing water cycle during the Cryogenian. Such precipitation runs counter to the dry atmosphere that would likely develop if the oceans were all capped with ice.

    “The suggestion that the Earth was once entirely covered by ice — the continents by thick ice sheets and the oceans by thick sea ice — remains somewhat contentious,” says physicist Richard Peltier of the University of Toronto.

    In response to these concerns, an alternative theory has developed that goes by the name “slushball.” In this case, the Earth becomes largely covered with ice, but open water remains near the equator. Sohl says that many of her geologist colleagues lean toward the slushball scenario, as it seems to better match observations.

    That is not to say that a hard snowball never happened. Extensive glaciation took place around 2.2 billion years ago, in the Paleoproterozoic era, and it seems plausible that global ice cover occurred then, Sohl says. Compared to the Cryogenian, the Paleoproterozoic sun was even fainter (down 16 percent in brightness from now). The timing of the glaciation also seems to coincide with the evolution of photosynthetic life, which would have drastically reduced greenhouse gases through the release of oxygen.

    2
    At various times in Earth’s history, our planet has been a “snowball”. Credit: MIT

    Tuning for the past

    To give a better understanding of the contentious Cryogenian period, Sohl’s team has been developing climate models that recreate the conditions on Earth nearly a billion years ago.

    They start with the NASA/GISS Earth System Model (ModelE2-R), which has been used to make the most recent climate assessments by the Intergovernmental Panel on Climate Change (IPCC). But they turn the clock back on the simulation, altering the parameters to what they were in the past. For example, the Sun’s brightness is dimmed by 6 percent and the continents are arranged into a single supercontinent near equator.

    “You need this flexibility when studying past climate conditions,” Sohl says. “We are probably using one of the most sophisticated models available for our paleoclimate runs.”

    Some previous attempts at simulating Earth’s history have focused on explicitly trying to produce a hard snowball, but Sohl and her colleagues have preferred to let the climate model suggest what the outcome of their runs should be. They have found that ocean currents, like the present-day Gulf Stream, have a large impact on how and where heat from the Sun ends up distributed across the Earth’s surface.

    “For us, the ocean circulation seems to help in preventing a full freeze-over,” Sohl says.

    The team’s early results show that the ocean retains areas of open water in the tropics, even when glaciers cover much of the land mass. The implication seems to be that the slushball picture is more likely than the hard snowball, at least as far as the Cryogenian period is concerned.

    Sohl and her colleagues are now exploring other aspects that could play a role in past climates. For example, the day was shorter during the Cryogenian (21.9 hours instead of 24), and that likely affected the atmospheric dynamics.

    Peltier, who is not involved in this work, believes one of the most outstanding issues remaining in Snowball Earth studies is the effect of the topography (i.e., altitude variations). Higher topography could enable glaciation even when other factors work against it, he says.

    These are not the first climate simulations to show that freezing a planet is not so easy, but “the message hasn’t really gotten to the astrobiologists” Sohl says. The astrobiology community tends to think of the hard snowball as the cold edge of habitability. They are often unaware how “slushy” that edge can be.

    The traditional definition of planet habitability is the presence of liquid water. And for convenience, scientists often assume that the state of water is determined by the distance a planet is from its star. In which case, the “habitable zone” is the region around a star where liquid water should exist. A planet outside this habitable zone should be in permanent snowball territory.

    But those who study climate know that an awful lot of factors go into freezing besides just the star-to-planet distance. Through her current project, Sohl hopes to elucidate some of these factors.

    “In the end, I think we’ll come to realize that the habitable zone is broader than we originally thought,” she says.

    See the full article here.

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  • richardmitnick 1:57 pm on July 31, 2015 Permalink | Reply
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    From Space.com via SETI Institute: “SETI Targets Kepler-452b, Earth’s ‘Cousin,’ in Search for Alien Life” 


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    q

    July 31, 2015
    Nola Taylor Redd, SPACE.com Contributor

    Temp 0
    An artist’s concept of the alien Kepler-452b in orbit around its star Kepler-452, which is located 1,400 light-years from Earth. NASA has billed the potentially habitable planet as Earth’s bigger, older cousin.

    Scientists with the SETI (Search for Extraterrestrial Intelligence) Institute have already begun targeting Earth’s “older cousin,” Kepler 452b, the first near-Earth-size world found in the habitable zone of a sun-like star.

    NASA announced the discovery of Kepler-452b last week, billing the planet as the closest thing yet to an Earth 2.0 beyond Earth’s solar system. Researchers have used the Allen Telescope Array [ATA], a collection of 42 radio antennas in northern California, to study the planet for radio signals that could indicate the presence of intelligent extraterrestrial life.

    SETI ATA
    ATA

    So far, the antennas haven’t tuned into any broadcasts.

    “That’s no reason to get discouraged,” Seth Shostak, senior astronomer with the SETI Institute, which is based in Mountain View, California, said during a July 26 webcast by the Slooh Community Observatory.

    “Bacteria, trilobites, dinosaurs—they were here but they weren’t building radio transmitters,” he said.

    Tens of billions of worlds

    Kepler-452 is a sunlike star, located 1,400 light-years from Earth, in the constellation Cygnus. The star’s newly discovered planet, Kepler-452b, has a radius approximately 1.6 times larger than Earth’s. The mass of the planet and its density, which would indicate its composition, have been a bit more challenging to pin down.

    “We would love to be able to do a direct mass measurement so we could measure density,” said Jon Jenkins of NASA’s Ames Research Center in Moffett Field, California, lead author on the paper that identified Kepler-452b. “That would be a big clue as to whether this is a rocky world or a water world or a gassy world.”

    Instead, the team relied on statistics to conclude that the planet has a “better than even chance” of having a composition similar to Earth.

    “The odds slightly favor this planet being rocky,” Jenkins said.

    Based on its size, orbit and star, Kepler-452b is the closest analogue to Earth yet discovered, its discoverers and NASA officials have said.

    Kepler-452b orbits its star once every 385 days, about three weeks longer than Earth takes to travel around the sun. This orbit places the planet squarely in what scientists call the “habitable zone,” the region around a star where liquid water could exist at a planet’s surface. Water is thought to be a key requirement for life to evolve, so Kepler-452b is one of the best potentially habitable worlds found to date.

    SETI Institute researchers are using the Allen Telescope Array, a collection of 6-meter (20 feet) telescopes in the Cascade Mountains of California, to observe Kepler-452b. So far, the array has observed the exoplanet on over 2 billion frequency bands, with no result. The telescopes will continue to observe over a total of 9 billion channels, searching for signals of alien intelligence.

    “There are three ways to find life in space,” Shostak said. The first is to “go there and look”, as humans are doing on Mars and the moons of the solar system, he said. For planets like Kepler-452b, which lie so far from the solar system, such a trip would be a challenge with today’s technology.

    The second is to “build big telescopes and analyze the light bouncing off of a planet,” Shostak said. NASA’s Hubble Space Telescope has already begun to probe the atmospheres of distant planets.

    NASA Hubble Telescope
    NASA/ESA Hubble

    However, Jenkins said, the host star is too dim to allow for this sort of examination with either Hubble or its successor, the James Webb Space Telescope.

    NASA Webb Telescope
    Webb

    The third way to find life in space is to search for signals that could indicate intelligence. “That’s what SETI does,” Shostak said.

    Both Shostak and Jenkins emphasized that what makes Kepler-452b truly important is what it indicates for the wide population of planets beyond the solar system. Before this planet’s discovery, no sun-like stars had been found to host rocky worlds in their habitable zones, making Earth fairly unique in the known galaxy. Although statistics suggested many such planets orbited other stars, no such worlds had been observed with modern instruments.

    Jenkins noted that the existence of Kepler-452b suggests similar finds will be made in the near future.

    “We have a really good opportunity in the future to find a similar-size planet in a similar-size orbit about a similar star far closer to us,” he said.

    Unlike the distant exoplanet, a closer exoplanet could have its atmosphere probed for potential signatures of life.

    “What you really want to know is what [fraction] of planets could be habitable,” Shostak said. He added that Kepler-452b suggests that fraction is perhaps one in five, or even one in three.

    “There could be tens of billions of such worlds in the galaxy,” Shostak said.

    See the full article here.

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  • richardmitnick 10:50 am on July 19, 2015 Permalink | Reply
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    From SPACE.com: “Newfound Alien Planet Is One of the Farthest Ever Detected” 

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    SPACE.com

    April 16, 2015
    Elizabeth Howell

    1
    NASA’s Spitzer Space Telescope co-discovered an exoplanet more than 13,000 light-years from Earth, far from where most known exoplanets are Credit: NASA/JPL-Caltech

    A NASA telescope has co-discovered one of the most distant planets ever identified: a gas giant about 13,000 light-years away from Earth.

    The technique used by the Spitzer Space Telescope, called microlensing, is so new that it has only yielded about 30 planet discoveries so far. But the telescope’s potential for finding far-away worlds is vast, NASA said in a statement. And as astronomers begin to chart the location of these distant bodies, it will provide a sense of where planets are distributed in Earth’s Milky Way galaxy.

    NASA Spitzer Telescope
    Spitzer

    “We don’t know if planets are more common in our galaxy’s central bulge or the disk of the galaxy, which is why these observations are so important,” Jennifer Yee, of the Harvard-Smithsonian Center for Astrophysics, said in a NASA statement. Yee is the lead author on one of three new papers describing the discovery.

    2
    An infographic showing how NASA’s Spitzer Space Telescope works with ground-based telescopes to find distant exoplanets, using a technique called microlensing. Credit: NASA/JPL-Caltech

    Magnified starlight

    Microlensing happens when one star travels in front of another from the perspective of an observer (in this case, on Earth). When this happens, the gravity of the star in front magnifies the light of the star behind it, acting like a lens. Should the star in front have a planet, that planet would create a “blip” during the magnification, NASA said in the statement.

    The challenge, however, is pinning down how far away the closer star (and its planet) is from Earth. Microlensing tends to magnify the star behind, but usually the star in front is invisible to observers. That’s why about half of the 30 or so planets found with microlensing (including a few Tatooine-like planets) are at unknown distances from Earth.

    To overcome the distance problem, astronomers used the Spitzer telescope in concert with the Polish Optical Gravitational Lensing Experiment (OGLE) Warsaw Telescope at the Las Campanas Observatory in Chile. OGLE routinely does microlensing investigations, but for Spitzer, this was the first time the long-running telescope had successfully used the technique to find a planet.

    OGLE Warsaw Telescope
    OGLE Warsaw telescope interior
    Polish Optical Gravitational Lensing Experiment (OGLE) Warsaw Telescope

    Quick telescope work

    Prominent telescopes like Spitzer are usually fully booked with other astronomical observations. This makes it difficult to respond quickly when the astronomical community is alerted about a microlensing event, which lasts only 40 days on average. Spitzer officials, however, have worked to do these observations as early as three days after an event is announced.

    The new planet’s microlensing event was quite long, roughly 150 days.

    Spitzer orbits the sun from a position behind Earth (about 128 million miles or 207 million kilometers away from its home planet, further than the Earth-sun distance). This vast distance from its home planet means the telescope sees microlensing events occur at a slightly different time than do telescopes on Earth.

    Spitzer spotted the “blip” in the magnification about 20 days before OGLE did. By comparing the delay between what Spitzer and OGLE saw, astronomers could calculate the planet’s distance from Earth. Once they knew that measure, they were able to estimate the planet’s mass, which is roughly half that of Jupiter.

    This is the first time Spitzer found a planet using microlensing, but it comes after 22 previous attempts with OGLE and other telescopes on the ground. Astronomers forecast Spitzer will examine 120 more microlensing events this summer.

    So far, microlensing has helped astronomers find 30 planets at distances as far as 25,000 light-years away from Earth. That’s in addition to the more than 1,000 closer worlds discovered by the planet-hunting Kepler space telescope and ground-based observatories using other techniques. Astronomers are using the microlensing events to seek out planets in the central “bulge” of the Milky Way, a spot where stars are more densely packed and tend to cross more often.

    See the full article here.

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