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  • richardmitnick 3:01 pm on November 6, 2018 Permalink | Reply
    Tags: , Centauri Dreams, , NIROSETI-Near-Infrared Optical SETI instrument at Lick on The Nickel Telescope   

    From Centauri Dreams: “SETI in the Infrared” 

    From Centauri Dreams

    November 6, 2018
    Paul Gilster

    One of the problems with optical SETI is interstellar extinction, the absorption and scattering of electromagnetic radiation. Extinction can play havoc with astronomical observations coping with gas and dust between the stars. The NIROSETI project (Near-Infrared Optical SETI) run by Shelley Wright (UC-San Diego) and team is a way around this problem. The NIROSETI instrument works at near-infrared wavelengths (1000 – 3500 nm), where extinction is far less of a problem. Consider infrared a ‘window’ through dust that would otherwise obscure the view, an advantage of particular interest for studies in the galactic plane.

    NIROSETI team from left to right Rem Stone UCO Lick Observatory Dan Werthimer UC Berkeley Jérôme Maire U Toronto, Shelley Wright UCSD Patrick Dorval U Toronto Richard Treffers Richard Treffers Starman Systems. (Image by Laurie Hatch)

    Would an extraterrestrial civilization hoping to communicate with us choose infrared as the wavelength of choice? We can’t know, but considering its advantages, NIROSETI’s instrument, mounted on the Nickel 1-m telescope at Lick Observatory, is helping us gain coverage in this otherwise neglected (for SETI purposes) band.

    UC Santa Cruz Shelley Wright at the 1-meter Nickel Telescope NIROSETI


    UCSC alumna Shelley Wright, now an assistant professor of physics at UC San Diego, discusses the dichroic filter of the NIROSETI instrument. (Photo by Laurie Hatch).jpg

    I had the chance to talk to Dr. Wright at one of the Breakthrough Discuss meetings in Palo Alto, where she made a fine presentation on the subject. Since then my curiosity about infrared SETI has remained high.

    Meanwhile, at MIT…

    Then this morning I came across graduate student James Clark, who has just published a paper on interstellar beacons in the infrared in The Astrophysical Journal. Working at MIT’s Department of Aeronautics and Astronautics, Clark is not affiliated with NIROSETI. He’s wondering what it would take to punch a signal through to another star, and concludes that a large infrared laser and a telescope through which to focus it would be the tools of choice.

    The goal: An infrared signal at least 10 times greater than the Sun’s natural infrared emissions, one that would stand out in any routine astronomical observation of our star and demand further study. Clark believes that a 2-megawatt laser working in conjunction with a 30-meter telescope would produce a signal easily detectable at Proxima Centauri b, while a 1-megawatt laser working through a 45-meter telescope would produce a clear signal at TRAPPIST-1.

    But nearby stars are just the beginning, for in Clark’s view, either of these setups would produce a signal that could be detected up to 20,000 light years away, almost to galactic center. All of this may remind you of Philip Lubin’s work, recently described here, on laser propulsion. Depending on the system in play, one of Lubin’s DE-STAR 4 beams would be observed as the brightest star in the sky from 1000 light years away (see Trillion Planet Survey Targets M-31 for more on this). The NIROSETI website makes the same observation about laser visibility:

    “The most powerful laser beams ever created (e.g. LFEX) can produce optical pulses with 2 petawatts (2.1015W) peak power for an incredibly short duration, approximately one picosecond. Such lasers would outshine our sun by several order of magnitudes if seen by a distant receiver. It can be shown that strong pulsed signals at nanosecond (or faster) intervals can be distinguishable from any known astrophysical sources.”

    3
    An MIT study proposes that laser technology on Earth could emit a beacon strong enough to attract attention from as far as 20,000 light years away. Credit: MIT.

    The kind of system Clarke is talking about is not beyond our capabilities even now:

    “This would be a challenging project but not an impossible one,” Clark says. “The kinds of lasers and telescopes that are being built today can produce a detectable signal, so that an astronomer could take one look at our star and immediately see something unusual about its spectrum. I don’t know if intelligent creatures around the sun would be their first guess, but it would certainly attract further attention.”

    In terms of current capabilities, we can think about Clark’s 30-meter telescope in relation to plans for telescopes as huge as the 39-meter European Extremely Large Telescope, now under construction in Chile, or the likewise emerging 24-meter Giant Magellan Telescope.

    ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

    Giant Magellan Telescope, to be at the Carnegie Institution for Science’s Las Campanas Observatory, to be built some 115 km (71 mi) north-northeast of La Serena, Chile, over 2,500 m (8,200 ft) high

    How and where to build such a laser is the same sort of issue now being analyzed by Breakthrough Starshot, which conceptualizes a series of small lightsail missions to nearby stars using laser beaming.

    Breakthrough Starshot image. Credit: Breakthrough Starshot

    Caveats include safety issues for both humans and spacecraft equipment. Clark suggests the far side of the Moon would be the ideal place for such an installation.

    With METI (Messaging to Extraterrestrial Intelligence) continuing to be controversial, to say the least, whether or not we would ever choose to build an infrared laser as an interstellar beacon is up for question.

    METI (Messaging Extraterrestrial Intelligence) International has announced plans to start sending signals into space

    But Clark’s analysis takes in the question of whether today’s technologies could detect such a signal if a civilization elsewhere put it into play and tried to communicate with us. As we’ve seen in other discussions of interstellar beacons, detection is highly problematic.

    “With current survey methods and instruments, it is unlikely that we would actually be lucky enough to image a beacon flash, assuming that extraterrestrials exist and are making them,” Clark says. “However, as the infrared spectra of exoplanets are studied for traces of gases that indicate the viability of life, and as full-sky surveys attain greater coverage and become more rapid, we can be more certain that, if E.T. is phoning, we will detect it.”

    We don’t know whether E.T. does astronomical surveys, but we know we do, and we are rapidly moving toward the study of small, rocky exoplanets through the spectra of their atmospheres. Thus Clark’s paper could be seen as a reminder to astronomers that an unusual signal could lurk within their infrared data, one that we should at least be aware of and prepared to analyze. A conversation between nearby stars at a data rate of a few hundred bits per second could eventually result.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Tracking Research into Deep Space Exploration

    Alpha Centauri and other nearby stars seem impossible destinations not just for manned missions but even for robotic probes like Cassini or Galileo. Nonetheless, serious work on propulsion, communications, long-life electronics and spacecraft autonomy continues at NASA, ESA and many other venues, some in academia, some in private industry. The goal of reaching the stars is a distant one and the work remains low-key, but fascinating ideas continue to emerge. This site will track current research. I’ll also throw in the occasional musing about the literary and cultural implications of interstellar flight. Ultimately, the challenge may be as much philosophical as technological: to reassert the value of the long haul in a time of jittery short-term thinking.

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  • richardmitnick 8:32 pm on October 1, 2018 Permalink | Reply
    Tags: , , , Centauri Dreams, , Phil Lubin-UCSB, SETI searches in the modern age, The Trillion Planet Survey   

    From Centauri Dreams: “Trillion Planet Survey Targets Messier 31 Andromeda” 

    From Centauri Dreams

    October 1, 2018
    Paul Gilster

    Can rapidly advancing laser technology and optics augment the way we do SETI?

    Laser SETI, the future of SETI Institute research

    At the University of California, Santa Barbara, Phil Lubin believes they can, and he’s behind a project called the Trillion Planet Survey to put the idea into practice for the benefit of students. As an incentive for looking into a career in physics, an entire galaxy may be just the ticket.

    For the target is the nearest galaxy to our own. The Trillion Planet Survey will use a suite of meter-class telescopes to search for continuous wave (CW) laser beacons from Messier 31, the Andromeda galaxy. But TPS is more than a student exercise. The work builds on Lubin’s 2016 paper called “The Search for Directed Intelligence,” which makes the case that laser technology foreseen today could be seen across the universe. And that issue deserves further comment.

    Centauri Dreams readers are familiar with Lubin’s work with DE-STAR, (Directed Energy Solar Targeting of Asteroids and exploRation), a scalable technology that involves phased arrays of lasers. DE-STAR installations could be used for purposes ranging from asteroid deflection (DE-STAR 2-3) to propelling an interstellar spacecraft to a substantial fraction of the speed of light (DE-STAR 3-4). The work led to NIAC funding (NASA Starlight) in 2015 examining beamed energy systems for propulsion in the context of miniature probes using wafer-scale photonics and is also the basis for Breakthough Starshot.

    Breakthrough Starshot Initiative

    Breakthrough Starshot

    ESO 3.6m telescope & HARPS at LaSilla, 600 km north of Santiago de Chile at an altitude of 2400 metres.

    SPACEOBS, the San Pedro de Atacama Celestial Explorations Observatory is located at 2450m above sea level, north of the Atacama Desert, in Chile, near to the village of San Pedro de Atacama and close to the border with Bolivia and Argentina

    SNO Sierra Nevada Observatory is a high elevation observatory 2900m above the sea level located in the Sierra Nevada mountain range in Granada Spain and operated maintained and supplied by IAC

    Teide Observatory in Tenerife Spain, home of two 40 cm LCO telescopes

    Observatori Astronòmic del Montsec (OAdM), located in the town of Sant Esteve de la Sarga (Pallars Jussà), 1,570 meters on the sea level

    Bayfordbury Observatory,approximately 6 miles from the main campus of the University of Hertfordshire

    A bit more background here: Lubin’s Phase I study “A Roadmap to Interstellar Flight “ is available online. It was followed by Phase II work titled “Directed Energy Propulsion for Interstellar Exploration (DEEP-IN).” Lubin’s discussions with Pete Worden on these ideas led to talks with Yuri Milner in late 2015. The Breakthrough Starshot program draws on the DE-STAR work, particularly in its reliance on miniaturized payloads and, of course, a laser array for beamed propulsion, the latter an idea that had largely been associated with large sails rather than chip-sized payloads. Mason Peck and team’s work on ‘sprites’ is also a huge factor.

    But let’s get back to the Trillion Planet Survey — if I start talking about the history of beamed propulsion concepts, I could spend days, and anyway, Jim Benford has already undertaken the task in these pages in his A Photon Beam Propulsion Timeline. What’s occupies us this morning is the range of ideas that play around the edges of beamed propulsion, one of them being the beam itself, and how it might be detected at substantial distances. Lubin’s DE-STAR 4, capable of hitting an asteroid with 1.4 megatons of energy per day, would stand out in many a sky.

    In fact, according to Lubin’s calculations, such a system — if directed at another star — would be seen in systems as distant as 1000 light years as, briefly, the brightest star in the sky. Suddenly we’re talking SETI, because if we can build such systems in the foreseeable future, so can the kind of advanced civilizations we may one day discover among the stars. Indeed, directed energy systems might announce themselves with remarkable intensity.

    2
    Messier 31, the Andromeda Galaxy, the target of the largely student led Trillion Planet Survey. Credit & Copyright: Robert Gendler.

    Lubin makes this point in his 2016 paper, in which he states “… even modest directed energy systems can be ‘seen’ as the brightest objects in the universe within a narrow laser linewidth.” Amplifying on this from the paper, he shows that stellar light in a narrow bandwidth would be very small in comparison to the beamed energy source:

    “In case 1) we treat the Sun as a prototype for a distant star, one that is unresolved in our telescope (due to seeing or diffraction limits) but one where the stellar light ends up in ~ one pixel of our detector. Clearly the laser is vastly brighter in this sense. Indeed for the narrower linewidth the laser is much brighter than an entire galaxy in this sense. For very narrow linewidth lasers (~ 1 Hz) the laser can be nearly as bright as the sum of all stars in the universe within the linewidth. Even modest directed energy systems can stand out as the brightest objects in the universe within the laser linewidth.”

    And again (and note here that the reference to ‘class 4’ is not to an extended Kardashev scale, but rather to a civilization transmitting at DE-STAR 4 levels, as defined in the paper):

    “As can be seen at the distance of the typical Kepler planets (~ 1 kly distant) a class 4 civilization… appears as the equivalent of a mag~0 star (ie the brightest star in the Earth’s nighttime sky), at 10 kly it would appear as about mag ~ 5, while the same civilization at the distance of the nearest large galaxy (Andromeda) would appear as the equivalent of a m~17 star. The former is easily seen with the naked eye (assuming the wavelength is in our detection band) while the latter is easily seen in a modest consumer level telescope.”

    Out of this emerges the idea that a powerful civilization could be detected with modest ground-based telescopes if it happened to be transmitting in our direction when we were observing. Hence the Trillion Planet Survey, which looks at using small telescopes such as those in the Las Cumbres Observatory’s robotic global network to make such a detection.

    With Messier 31 as the target, the students in the Trillion Planet Survey are conducting a survey of the galaxy as TPS gets its software pipeline into gear. Developed by Emory University student Andrew Stewart, the pipeline processes images under a set of assumptions. Says Stewart:

    “First and foremost, we are assuming there is a civilization out there of similar or higher class than ours trying to broadcast their presence using an optical beam, perhaps of the ‘directed energy’ arrayed-type currently being developed here on Earth. Second, we assume the transmission wavelength of this beam to be one that we can detect. Lastly, we assume that this beacon has been left on long enough for the light to be detected by us. If these requirements are met and the extraterrestrial intelligence’s beam power and diameter are consistent with an Earth-type civilization class, our system will detect this signal.”

    Screening transient signals from its Messier 31 images, the team will then submit them to further processing in the software pipeline to eliminate false positives. The TPS website offers links to background information, including Lubin’s 2016 paper, but as of yet has little about the actual image processing, so I’ll simply quote from a UCSB news release on the matter:

    “We’re in the process of surveying (Andromeda) right now and getting what’s called ‘the pipeline’ up and running,” said researcher Alex Polanski, a UC Santa Barbara undergraduate in Lubin’s group. A set of photos taken by the telescopes, each of which takes a 1/30th slice of Andromeda, will be knit together to create a single image, he explained. That one photograph will then be compared to a more pristine image in which there are no known transient signals — interfering signals from, say, satellites or spacecraft — in addition to the optical signals emanating from the stellar systems themselves. The survey photo would be expected to have the same signal values as the pristine “control” photo, leading to a difference of zero. But a difference greater than zero could indicate a transient signal source, Polanski explained. Those transient signals would then be further processed in the software pipeline developed by Stewart to kick out false positives. In the future the team plans to use simultaneous multiple color imaging to help remove false positives as well.”

    Why Andromeda? The Trillion Planet Survey website notes that the galaxy is home to at least one trillion stars, a stellar density higher than the Milky Way’s, and thus represents “…an unprecedented number of targets relative to other past SETI searches.” The project gets the students who largely run it into the SETI business, juggling the variables as we consider strategies for detecting other civilizations and upgrading existing search techniques, particularly as we take into account the progress of exponentially accelerating photonic technologies.

    Projects like these can exert a powerful incentive for students anxious to make a career out of physics. Thus Caitlin Gainey, now a freshman in physics at UC Santa Barbara:

    “In the Trillion Planet Survey especially, we experience something very inspiring: We have the opportunity to look out of our earthly bubble at entire galaxies, which could potentially have other beings looking right back at us. The mere possibility of extraterrestrial intelligence is something very new and incredibly intriguing, so I’m excited to really delve into the search this coming year.”

    And considering that any signal arriving from M31 would have been enroute for well over 2 million years, the TPS also offers the chance to involve students in the concept of SETI as a form of archaeology. We could discover evidence of a civilization long dead through signals sent well before civilization arose on Earth. A ‘funeral beacon’ announcing the demise of a once-great civilization is a possibility. In terms of artifacts, the search for Dyson Spheres or other megastructures is another. The larger picture is that evidence of extraterrestrial intelligence can come in various forms, including optical or radio signals as well as artifacts detectable through astronomy. It’s a field we continue to examine here, because that search has just begun.

    Phil Lubin’s 2016 paper is “The Search for Directed Intelligence,” REACH – Reviews in Human Space Exploration, Vol. 1 (March 2016), pp. 20-45. (Preprint / full text).

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Tracking Research into Deep Space Exploration

    Alpha Centauri and other nearby stars seem impossible destinations not just for manned missions but even for robotic probes like Cassini or Galileo. Nonetheless, serious work on propulsion, communications, long-life electronics and spacecraft autonomy continues at NASA, ESA and many other venues, some in academia, some in private industry. The goal of reaching the stars is a distant one and the work remains low-key, but fascinating ideas continue to emerge. This site will track current research. I’ll also throw in the occasional musing about the literary and cultural implications of interstellar flight. Ultimately, the challenge may be as much philosophical as technological: to reassert the value of the long haul in a time of jittery short-term thinking.

     
  • richardmitnick 9:07 am on March 7, 2018 Permalink | Reply
    Tags: A New Theory of Lunar Formation, , , , , Centauri Dreams,   

    From Centauri Dreams: “A New Theory of Lunar Formation” 

    Centauri Dreams

    March 6, 2018
    Paul Gilster

    Simon Lock and Sarah Stewart are intent upon revising our views on how the Moon was formed. Lock is a Harvard graduate student who last year, in company with Stewart (UC-Davis) presented interesting work on what the duo are calling a ‘synestia,’ which is the kind of ‘structure’ resulting from the collision of huge objects. Current thinking about the Moon is that it formed following the collision of a Mars-sized object with the Earth, two huge objects indeed.

    What Lock and Stewart asked is whether this formation scenario can produce the result we see today. What it calls for is the ejection of material that forms into a disk and, through processes of accretion, gradually becomes the Moon. The problem with it, says Lock, is that it’s a very hard trick to pull off:

    “Getting enough mass into orbit in the canonical scenario is actually very difficult, and there’s a very narrow range of collisions that might be able to do it. There’s only a couple-of-degree window of impact angles and a very narrow range of sizes … and even then some impacts still don’t work.”

    Perhaps we’ve misunderstood the original, massive collision. An adjusted formation scenario could explain why some volatile elements like potassium, sodium and copper are less abundant on the Moon than the Earth, and why isotope ratios for the Earth and the Moon are nearly identical. The ‘synestia’ hypothesis works like this: We still begin with an impact, but the assumed disk of raw materials never forms. Instead, the angular momentum of both colliding bodies is added together, creating a vast, indented disk much bigger than either object.

    I’m going to drop back to an earlier Lock and Stewart paper for an illustration here.

    1
    Image: The structure of a planet, a planet with a disk and a synestia, all of the same mass. Credit: Simon Lock and Sarah Stewart.

    The 2018 paper describes a synestia as:

    “…an impact-generated structure with Earth-mass and composition that exceeds the corotation limit (CoRoL). Synestias are formed by a range of high-energy, high-AM [angular momentum] collisions during the giant impact stage of planet formation (Lock and Stewart, 2017, hereafter LS17). A synestia is a distinct dynamical structure compared to a planet with a condensate-dominated circumplanetary disk, and, as a result, different processes dominate the early evolution of a synestia….”

    So the synestia we get from major collisions — and these should be frequent in young planetary systems — is a rapidly rotating, partially vaporized object, molten or gaseous material expanding in volume, an object in the shape of a squashed doughnut without any solid surface. The synestia cannot rotate like a solid body because of variations in rotational rate and thermal energy, so we get an inner region rotating one way and an outer region moving at orbital speeds. Perhaps 10 percent of the Earth’s rock is vaporized, while the rest becomes liquid.

    When Lock and Stewart set up simulations of cooling synestias and examine them with dynamic, thermodynamic and geochemical calculations, they find that a ‘seed’ forms within the synestia, a gathering of liquid rock that forms off-center and grows as the structure cools, with vaporized rock condensing and falling toward the center of the synestia. As some of this material strikes the ‘seed’ that will become the Moon, it begins to grow. The Moon eventually emerges from the vapor of the synestia as condensation continues and the synestia recedes within the lunar orbit, with the remainder of the spinning debris coalescing into the Earth.

    From the paper:

    “Most high-energy, high-AM giant impacts can produce synestias. The formation of the Moon within a terrestrial synestia can potentially reproduce the lunar bulk composition, the isotopic similarity between Earth and the Moon, and the large mass of the Moon. If the post-impact body also had high obliquity, the same giant impact may trigger a tidal evolution sequence that explains the present day lunar inclination and the AM of the Earth-Moon system…”

    3
    Image: Part of the paper’s Figure 18, illustrating Moon formation within a terrestrial synestia. Credit: Lock & Stewart.

    The impact scenario for lunar formation thus shifts to a study of the properties of the synestia that produced the Moon. The similarity in isotopes between the Earth and the Moon is an issue because simulations of giant impacts under the older model produce a lunar disk made primarily of material from the impacting body. But isotope ratios vary among the planets. We would expect differences within these ratios if the Moon formed largely from the impactor’s materials.

    Under the synestia model, Earth and Moon emerge from the same cloud of vaporized rock, explaining the isotopic similarity. In this scenario, a planetary satellite forms inside the planet it will orbit. Lock and Stewart explain the Moon’s lack of volatile elements by the same formation story, with the forming Moon surrounded by high-temperature material from the synestia. The paper adds:

    “The MVEs [moderately volatile elements] that are not incorporated into the Moon remain in the synestia. As the synestia cools and contracts within the lunar orbit, the remaining MVEs are destined to be incorporated into the bulk silicate Earth.”

    This is a complicated model, but Stewart points out in this Harvard news release that it replicates features of the Moon’s composition that are otherwise hard to explain. Further exploration of synestias will be useful as we model what happens in early exoplanet systems, where collisions on a similar colossal scale should be a feature of planet formation.

    The paper is Lock et al., “The Origin of the Moon within a Terrestrial Synestia,” Journal of Geographysical Research: Planets 28 February 2018 (abstract / preprint). The 2017 paper is Lock & Stewart, “The structure of terrestrial bodies: Impact heating, corotation limits, and synestias,” Journal of Geophysical Research: Planets 122 (2017). Abstract / preprint.

    Centauri Dreams

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Tracking Research into Deep Space Exploration

    Alpha Centauri and other nearby stars seem impossible destinations not just for manned missions but even for robotic probes like Cassini or Galileo. Nonetheless, serious work on propulsion, communications, long-life electronics and spacecraft autonomy continues at NASA, ESA and many other venues, some in academia, some in private industry. The goal of reaching the stars is a distant one and the work remains low-key, but fascinating ideas continue to emerge. This site will track current research. I’ll also throw in the occasional musing about the literary and cultural implications of interstellar flight. Ultimately, the challenge may be as much philosophical as technological: to reassert the value of the long haul in a time of jittery short-term thinking.

     
  • richardmitnick 4:07 pm on November 2, 2017 Permalink | Reply
    Tags: , , , Centauri Dreams, Cold Trap in a Hot Jupiter’s Atmosphere, , Kepler-13Ab,   

    From Centauri Dreams: “Cold Trap in a Hot Jupiter’s Atmosphere” 

    Centauri Dreams

    November 2, 2017
    Paul Gilster

    The other day I looked at how we can use transit spectroscopy to study the atmospheres of exoplanets. Consider this a matter of eclipses, the first occurring when the planet moves in front of its star as seen from Earth.

    Planet transit. NASA/Ames

    We can measure the size of the planet and also see light from the star as it moves through the planetary atmosphere, giving us information about its composition. The secondary eclipse, when the planet disappears behind the star, is also quite useful. Here, we can study the atmosphere in terms of its thermal variations.

    In my recent post, I used a diagram from Sara Seager to show primary and secondary eclipse in relation to a host star. The image below, by Josh Winn, is useful because it drills down into the specifics.

    1
    Image: A comparison between transits and secondary eclipses (also sometimes called occultations). In a planetary transit, the planet crosses in front of the star (see lower dip) blocking a fraction of the star’s brightness. In a secondary eclipse, the planet crosses behind the star, blocking the planet’s brightness (see dip in the middle). The latter dip in brightness is fainter due to the faintness of the planet. Credit: Josh Winn. See A New Discovery of a Secondary Eclipse for more background as it applies to the HAT-P-11 system.

    Secondary eclipses have been significant in the study of Kepler-13Ab, a world where conditions could not be more different on the planet’s nightside vs. its dayside. A ‘hot Jupiter’ some 1730 light years from Earth, this is a world close enough to its parent star that it is tidally locked. Researchers led by Thomas Beatty (Pennsylvania State) have used the Hubble Space Telescope to determine that that the dayside here can surpass a blistering 3000 Kelvin.

    By contrast, the nightside of Kepler-13Ab, turned forever away from the star, is a place where titanium oxide snow can fall. The process is intriguing: Any titanium oxide gas on the star-facing side is carried by strong winds around to the nightside, where the gas condenses into clouds and eventually falls as snow. A gravitational tug six times greater than Jupiter’s pulls the titanium oxide into the lower atmosphere, forming a ‘cold trap’ — an atmospheric layer that is colder than the layers both below and above it. Ascending gases drop back into the trap.

    Science paper:
    Evidence for Atmospheric Cold-trap Processes in the Noninverted Emission Spectrum of Kepler-13Ab Using HST/WFC3

    Centauri Dreams

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Tracking Research into Deep Space Exploration

    Alpha Centauri and other nearby stars seem impossible destinations not just for manned missions but even for robotic probes like Cassini or Galileo. Nonetheless, serious work on propulsion, communications, long-life electronics and spacecraft autonomy continues at NASA, ESA and many other venues, some in academia, some in private industry. The goal of reaching the stars is a distant one and the work remains low-key, but fascinating ideas continue to emerge. This site will track current research. I’ll also throw in the occasional musing about the literary and cultural implications of interstellar flight. Ultimately, the challenge may be as much philosophical as technological: to reassert the value of the long haul in a time of jittery short-term thinking.

     
  • richardmitnick 1:28 pm on September 29, 2017 Permalink | Reply
    Tags: , , , Centauri Dreams, ,   

    From Centauri Dreams: “Project Blue: Looking for Terrestrial Worlds at Alpha Centauri” 

    Centauri Dreams

    September 29, 2017
    Paul Gilster

    Eduardo Bendek’s ACEsat, conceived at NASA Ames by Bendek and Ruslan Belikov, seemed to change the paradigm for planet discovery around the nearest stellar system. The beauty of Alpha Centauri is that the two primary stars present large habitable zones as seen from Earth, simply because the system is so close to us.

    ESO Red Dots Campaign

    The downside, in terms of G-class Centauri A and K-class Centauri B, is that their binary nature makes filtering out starlight a major challenge.

    1
    Image: The Alpha Centauri system. The combined light of Centauri A (G-class) and Centauri B (K-class) appears here as a single overwhelmingly bright ‘star.’ Proxima Centauri can be seen circled at bottom right. Credit: European Southern Observatory.

    If we attack the problem from the ground, ever bigger instruments seem called for, like the European Southern Observatory’s Very Large Telescope…

    ESO/VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

    …in conjunction with the VISIR instrument (VLT Imager and Spectrometer for mid-Infrared) that Breakthrough Initiatives is now working with the ESO to enhance.

    Breakthrough Listen Project

    1

    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA



    GBO radio telescope, Green Bank, West Virginia, USA


    CSIRO/Parkes Observatory, located 20 kilometres north of the town of Parkes, New South Wales, Australia

    Or perhaps one of the extremely large telescopes now in the works, like the Thirty Meter Telescope in Hawaii, or the Giant Magellan Telescope in Chile.

    TMT-Thirty Meter Telescope, proposed and now approved for Mauna Kea, Hawaii, USA4,207 m (13,802 ft) above sea level

    Giant Magellan Telescope, to be at Las Campanas Observatory, to be built some 115 km (71 mi) north-northeast of La Serena, Chile, over 2,500 m (8,200 ft) high

    And if we did this from space, surely it would be an expensive platform. Except that ACEsat wasn’t expensive, nor was it large. It was designed to do just one thing and do it well.

    While NASA turned down Bendek and Belikov’s idea for Small Explorer funding, the striking thing is that it would have fit that category’s definition. ACEsat was designed as a 30 to 45 cm space telescope (you can see a Belikov presentation on the instrument here, or for that matter, read Ashley Baldwin’s ACEsat: Alpha Centauri and Direct Imaging). The small instrument now being proposed by an initiative called Project Blue builds on many of the ACEsat concepts.

    3
    Project Blue. Many Partners. the BoldlyGo Institute and its Project Blue partners – including the SETI Institute, the University of Massachusetts at Lowell, and Mission Centaur.

    It would run perhaps $50 million even though the original ACEsat was a $175 million design.

    In other words, compared to the $8 billion James Webb Space Telescope, Project Blue’s instrument is almost inexpensive enough to be a rounding error. A privately funded initiative out of the Boldly Go Institute, in partnership with the SETI Institute, Mission Centaur, and UMass Lowell, the telescope shows its pedigree both in its low cost and big scientific return. It seems the ACEsat concept is just too good to go away.

    So now we have Project Blue, which is all about seeing the blue of an Earth-like world around one or even both of the Sun-like stars of the Alpha Centauri system. No one discounts the value of the planet already discovered around Proxima Centauri, but the project hopes to find an Earth 2.0, a rocky planet in a habitable zone orbit around a star like our own. That would mean no tidal locking, no small red dwarf primary, and a year measured in months rather than days.

    4
    Image: An Earth-like planet around one of the primary Alpha Centauri stars, as simulated by Project Blue.

    The project’s new Indiegogo campaign has been set up to raise $175,000 to help establish mission requirements, including the design of an initial system architecture to which computer simulations can be applied by way of testing ideas and simulating outcomes. The launch goal of 2021 is ambitious indeed, as is the low $50 million budget profile, but the project’s backers believe their work can leverage advances in the small satellite industry and imaging systems to pull it off. An explicit goal is to engage the public while tapping the original NASA work.

    The project’s connection to NASA is in the form of a cooperative agreement explained on the Indiegogo site:

    “The BoldlyGo Institute and NASA have signed a Space Act Agreement to cooperate on Project Blue, a mission to search for potentially habitable Earth-size planets in the Alpha Centauri system using a specially designed space telescope. The agreement allows NASA employees – scientists and engineers – to interact with the Project Blue team through its mission development phases to help review mission design plans and to share scientific results on Alpha Centauri and exoplanets along with the latest technology tests being undertaken at NASA facilities. The agreement also calls for the raw and processed data from Project Blue to be made available to NASA within one year of its acquisition on orbit via a publicly accessible online data archive. The Project Blue team has been planning such an archive for broadly sharing the data with the global astronomical community and for enabling citizen scientist participation.”

    And I notice that Eduardo Bendek is among the ranks of an advisory committee (available here) that includes the likes of exoplanet hunters Olivier Guyon, Debra Fischer, Jim Kasting and Maggie Turnbull. But have a look at the advisor page; every one of these scientists is playing a significant role in our discovery and evaluation of new exoplanetary systems.

    Thus we can say that ACEsat lives on in this new incarnation that will benefit from the input of its original designers. The spacecraft would spend two years in low Earth orbit accumulating thousands of images with the help of an onboard coronagraph to remove light from the twin stars, along with a deformable mirror, low-order wavefront sensors, and control algorithms to manage incoming light, enhancing image contrast with software processing methods.

    Unlike the major observatories we’re soon to be launching — not just the James Webb Space Telescope but the Transiting Exoplanet Survey Satellite (TESS) — the Project Blue observatory will be dedicated to a single target, with no other observational duties.

    NASA/ESA/CSA Webb Telescope annotated

    NASA/TESS

    A photograph of an Earth-like planet 40 trillion kilometers away gives us a sense of the changes in scale that have occurred since Voyager 1’s ‘pale blue dot’ photograph. But we already knew that Earth was inhabited. Now, gaining spectral information about a blue and green world around a nearby star would allow us to determine whether biosignature gases could be found in its atmosphere, potential signs of life that would mark a breakthrough in our science. The degree of public involvement assumed in the project makes the quest all the more tantalizing.

    Centauri Dreams

    See the full article here .

    Please help promote STEM in your local schools.

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    Tracking Research into Deep Space Exploration

    Alpha Centauri and other nearby stars seem impossible destinations not just for manned missions but even for robotic probes like Cassini or Galileo. Nonetheless, serious work on propulsion, communications, long-life electronics and spacecraft autonomy continues at NASA, ESA and many other venues, some in academia, some in private industry. The goal of reaching the stars is a distant one and the work remains low-key, but fascinating ideas continue to emerge. This site will track current research. I’ll also throw in the occasional musing about the literary and cultural implications of interstellar flight. Ultimately, the challenge may be as much philosophical as technological: to reassert the value of the long haul in a time of jittery short-term thinking.

     
  • richardmitnick 1:47 pm on September 19, 2017 Permalink | Reply
    Tags: , , , Centauri Dreams, , Red Edge’ Biomarkers on M-dwarf Planets   

    From Centauri Dreams: “‘Red Edge’ Biomarkers on M-dwarf Planets” 

    Centauri Dreams

    September 19, 2017
    Paul Gilster

    When we think about the markers of possible life on other worlds, vegetation comes to mind in an interesting way. We’d like to use transit spectroscopy to see biosignatures, gases that have built up in the atmosphere because of ongoing biological activity. But plants using photosynthesis offer us an additional option. They absorb sunlight from the visible part of the spectrum, but not longer-wavelength infrared light. The latter they simply reflect.

    What we wind up with is a possible observable for a directly imaged planet, for if you plot the intensity of light against wavelength, you will find a marked drop known as the ‘red edge.’ It shows up when going from longer infrared wavelengths into the visible light region. The red-edge position for Earth’s vegetation is fixed at around 700–760 nm. What we’d like to do is find a way to turn this knowledge into a practical result while looking at exoplanets. Where would we find the red edge on planets circling stars of a different class than our own?

    Led by Kenji Takizawa, researchers at the Astrobiology Center (ABC) of National Institutes of Natural Science (NINS) in Japan have taken up the question with regard to M-dwarfs. These stars have lower surface temperatures than the Sun and emit more strongly at near-infrared wavelengths than at visible wavelengths. Assuming vegetation in such an environment evolves to use the most abundant photons for photosynthesis, shouldn’t we expect the red edge to shift accordingly? Perhaps not, argue the authors, as only blue-green light penetrates beyond a few meters of water. Visible light, in other words, may play a larger role than we imagine.

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    Image: Artist’s impressions of a habitable planet around M-dwarfs (left) and primordial Earth (right). Credit: ABC/NINS.

    Centauri Dreams


    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    Tracking Research into Deep Space Exploration

    Alpha Centauri and other nearby stars seem impossible destinations not just for manned missions but even for robotic probes like Cassini or Galileo. Nonetheless, serious work on propulsion, communications, long-life electronics and spacecraft autonomy continues at NASA, ESA and many other venues, some in academia, some in private industry. The goal of reaching the stars is a distant one and the work remains low-key, but fascinating ideas continue to emerge. This site will track current research. I’ll also throw in the occasional musing about the literary and cultural implications of interstellar flight. Ultimately, the challenge may be as much philosophical as technological: to reassert the value of the long haul in a time of jittery short-term thinking.

     
  • richardmitnick 3:59 pm on August 15, 2017 Permalink | Reply
    Tags: , , , Centauri Dreams, ,   

    From Centauri Dreams: “TRAPPIST-1: The Importance of Age” 

    Centauri Dreams

    If life can arise around red dwarf stars, you would think TRAPPIST-1 would be the place to look. Home to seven planets, this ultracool M8V dwarf star about 40 light years away in Aquarius has been around for a long time. The age range in a new study on the matter goes from 5.4 billion years up to almost ten billion years. And we have more than one habitable zone planet to look at.

    Adam Burgasser (UC-San Diego) and Eric Mamajek (JPL) are behind the age calculations, which appear in a paper that has been accepted at The Astrophysical Journal. We have no idea how long it takes life to emerge, having only one example to work with, but it’s encouraging that we find evidence for it very early in Earth’s history, dating back some 3.8 billion years. But we also have much to learn about habitability around red dwarfs in general.

    The TRAPPIST-1 star, an ultracool dwarf, is orbited by seven Earth-size planets (NASA).

    ESO Belgian robotic Trappist National Telescope at Cerro La Silla, Chile interior

    ESO Belgian robotic Trappist-South National Telescope at Cerro La Silla, Chile

    The good thing about being a somewhat older red dwarf is that flare activity should have slowed over time, a fact that the authors confirm. This doesn’t make it necessarily benign. In fact, as the paper points out, “…despite TRAPPIST-1’s modest emission as compared to other late-M dwarfs, the radiation and particle environment is still extreme as compared to the Earth.”

    Centauri Dreams


    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Tracking Research into Deep Space Exploration

    Alpha Centauri and other nearby stars seem impossible destinations not just for manned missions but even for robotic probes like Cassini or Galileo. Nonetheless, serious work on propulsion, communications, long-life electronics and spacecraft autonomy continues at NASA, ESA and many other venues, some in academia, some in private industry. The goal of reaching the stars is a distant one and the work remains low-key, but fascinating ideas continue to emerge. This site will track current research. I’ll also throw in the occasional musing about the literary and cultural implications of interstellar flight. Ultimately, the challenge may be as much philosophical as technological: to reassert the value of the long haul in a time of jittery short-term thinking.

     
  • richardmitnick 7:58 am on July 20, 2017 Permalink | Reply
    Tags: , , , Centauri Dreams, , Nickel 1-meter telescope at Lick Observatory, NIROSETI-Near-Infrared Optical SETI instrument, Optical SETI, Radio SETI, , Shelley Wright,   

    From Centauri Dreams: “Making Optical SETI Happen” 

    Centauri Dreams

    July 18, 2017
    Paul Gilster

    Yesterday I made mention of the Schwartz and Townes paper “Interstellar and Interplanetary Communication by Optical Masers,” which ran in Nature in 1961 (Vol. 190, Issue 4772, pp. 205-208). Whereas the famous Cocconi and Morrison paper that kicked off radio SETI quickly spawned an active search in the form of Project Ozma, optical SETI was much slower to develop. The first search I can find is a Russian project called MANIA, in the hands of V. F. Shvartsman and G. M. Beskin, who searched about 100 objects in the early 1970s, finding no significant brightness variations within the parameters of their search.

    If you want to track this one down, you’ll need a good academic library, as it appears in the conference proceedings for the Third Decennial US-USSR Conference on SETI, published in 1993. Another Shvartsman investigation under the MANIA rubric occurred in 1978. Optical SETI did not seem to seize the public’s imagination, perhaps partially because of the novelty of communications through the recently discovered laser. We do see several optical SETI studies at UC-Berkeley’s Leuschner Observatory and Kitt Peak from 1979 to 1981, the work of Francisco Valdes and Robert Freitas, though these were searches for Bracewell probes within the Solar System rather than attempts to pick up laser transmissions from other star systems.

    1
    Harvard’s Paul Horowitz, a key player in the development of optical SETI. Credit: Harvard University.

    This was an era when radio searches for extraterrestrial technology had begun to proliferate, but despite the advocacy of Townes and others (and three conferences Townes helped create), it wasn’t until the 1990s that optical SETI began to come into its own. Charles Townes himself was involved in a search for laser signals from about 300 nearby stars in the ‘90s, using the 1.7-meter telescope on Mt. Wilson and reported on at the 1993 conference. Stuart Kingsley began an optical SETI search using the 25-centimeter telescope at the Columbus Optical SETI Observatory (COSETI) in 1990, while Gregory Beskin searched for optical signals at the Special Astrophysical Observatory run by the Russian Academy of Sciences in the Caucasus in 1995.

    Optical SETI’s advantages were beginning to be realized, as Andrew Howard (Caltech) commented in a 2004 paper:

    “The rapid development of laser technology since that time—a Moore’s law doubling of capability roughly every year—along with the discovery of many microwave lines of astronomical interest, have lessened somewhat the allure of hydrogen-line SETI. Indeed, on Earth the exploitation of photonics has revolutionized communications technology, with high-capacity fibers replacing both the historical copper cables and the long-haul microwave repeater chains. In addition, the elucidation (Cordes & Lazio 1991) of the consequences to SETI of interstellar dispersion (first seen in pulsar observations) has broadened thinking about optimum wavelengths. Even operating under the prevailing criterion of minimum energy per bit transmitted, one is driven upward to millimetric wavelengths.”

    In the late 90’s, the SETI Institute, as part of a reevaluation of SETI methods, recommended and then co-funded several optical searches including one by Dan Werthimer and colleagues at UC Berkeley and another by a Harvard-Smithsonian team including Paul Horowitz and Andrew Howard. The Harvard-Smithsonian group also worked in conjunction with Princeton University on a detector system similar to the one mounted on Harvard’s 155-centimeter optical telescope. A newer All-Sky Optical SETI (OSETI) telescope, set up at the Oak Ridge Observatory at Harvard and funded by The Planetary Society, dates from 2006.

    4
    http://seti.harvard.edu/oseti/allsky/allsky.htm

    5
    http://www.setileague.org/photos/oseti3.htm

    6
    http://seti.harvard.edu/oseti/

    At Berkeley, the optical SETI effort is led by Werthimer, who had built the laser detector for the Harvard-Smithsonian team. Optical SETI efforts from Leuschner Observatory and Lick Observatory were underway by 1999. Collaborating with Shelley Wright (UC Santa Cruz), Remington Stone (UC Santa Cruz/Lick Observatory), and Frank Drake (SETI Institute), the Berkeley group has gone on to develop new detector systems to improve sensitivity. As I mentioned yesterday, UC-Berkeley’s Nate Tellis, working with Geoff Marcy, has analyzed Keck archival data for 5,600 stars between 2004 and 2016 in search of optical signals.

    Working in the infrared, the Near-Infrared Optical SETI instrument (NIROSETI) is designed to conduct searches at infrared wavelengths. Shelley Wright is the principal investigator for NIROSETI, which is mounted on the Nickel 1-meter telescope at Lick Observatory, seeing first light in March of 2015. The project is designed to search for nanosecond pulses in the near-infrared, with a goal “to search not only for transient phenomena from technological activity, but also from natural objects that might produce very short time scale pulses from transient sources.” The advantage of near-infrared is the decrease in interstellar extinction, the absorption by dust and gas that can sharply impact the strength of a signal.

    7
    Shelley Wright, then a student at UC-Santa Cruz, helped build a detector that divides the light beam from a telescope into three parts, rather than just two, and sends it to three photomultiplier tubes. This arrangement greatly reduces the number of false alarms; very rarely will instrumental noise trigger all three detectors at once. The three-tube detector is in the white box attached here to the back of the 1-meter Nickel Telescope at Lick Observatory. Credit: Seth Shostak.

    8
    UCSC Lick Observatory Nickel Telescope

    I might also mention METI International’s Optical SETI Observatory at Boquete, Panama. The idea is to put the optical SETI effort in context. With the SETI Institute now raising money for its Laser SETI initiative — all-sky all-the-time — the role of private funding in making optical SETI happen is abundantly clear. And now, of course, we also have Breakthrough Listen, which in addition to listening at radio wavelengths at the Parkes instrument in Australia and the Green Bank radio telescope in West Virginia, is using the Automated Planet Finder at Lick Observatory to search for optical laser transmissions.

    CSIRO/Parkes Observatory, located 20 kilometres north of the town of Parkes, New South Wales, Australia



    GBO radio telescope, Green Bank, West Virginia, USA

    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

    Funded by the Breakthrough Prize Foundation, the project continues the tradition of private funding from individuals, institutions (the SETI Institute) and organizations like The Planetary Society to get optical SETI done.

    Centauri Dreams


    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Tracking Research into Deep Space Exploration

    Alpha Centauri and other nearby stars seem impossible destinations not just for manned missions but even for robotic probes like Cassini or Galileo. Nonetheless, serious work on propulsion, communications, long-life electronics and spacecraft autonomy continues at NASA, ESA and many other venues, some in academia, some in private industry. The goal of reaching the stars is a distant one and the work remains low-key, but fascinating ideas continue to emerge. This site will track current research. I’ll also throw in the occasional musing about the literary and cultural implications of interstellar flight. Ultimately, the challenge may be as much philosophical as technological: to reassert the value of the long haul in a time of jittery short-term thinking.

     
  • richardmitnick 3:46 pm on July 19, 2017 Permalink | Reply
    Tags: , Centauri Dreams, , , , , , , U Chicago Yerkes Observatory   

    From Centauri Dreams: “Keeping an Eye on Ross 128” 

    Centauri Dreams

    July 19, 2017
    Paul Gilster

    1
    A screen shot from Abel Méndez’s lab note titled “Strange Signals from the Nearby Red Dwarf Star Ross 128.” Credit: Planetary Habitability Laboratory/University of Puerto Rico, Arecibo/Aladin Sky Atlas.

    Frank Elmore Ross (1874-1960), an American astronomer and physicist, became the successor to E. E. Barnard at Yerkes Observatory.

    1
    U Chicago Yerkes Observatory

    2
    U Chicago Yerkes Observatory interior

    Barnard, of course, is the discoverer of the high proper motion of the star named after him, alerting us to its proximity.

    3
    http://www.daviddarling.info/encyclopedia/B/BarnardsStar.html

    And as his successor, Ross would go on to catalog over 1000 stars with high proper motion, many of them nearby. Ross 128, now making news for what observers at the Arecibo Observatory are calling “broadband quasi-periodic non-polarized pulses with very strong dispersion-like features,” is one of these, about 11 light years out in the direction of Virgo.

    NAIC/Arecibo Observatory, Puerto Rico, USA

    Any nearby stars are of interest from the standpoint of exoplanet investigations, though thus far we’ve yet to discover any companions around Ross 128. An M4V dwarf, Ross 128 has about 15 percent of the Sun’s mass. More significantly, it is an active flare star, capable of unpredictable changes in luminosity over short periods. Which leads me back to that unusual reception. The SETI Institute’s Seth Shostak described it this way in a post:

    “What the Puerto Rican astronomers found when the data were analyzed was a wide-band radio signal. This signal not only repeated with time, but also slid down the radio dial, somewhat like a trombone going from a higher note to a lower one.”

    And as Shostak goes on to say, “That was odd, indeed.”

    It’s this star’s flare activity that stands out for me as I look over the online announcement of its unusual emissions, which were noted during a ten-minute spectral observation at Arecibo on May 12. Indeed, Abel Mendez, director of the Planetary Habitability Laboratory at Arecibo, cited Type II solar flares first in a list of possible explanations, though his post goes on to note that such flares tend to occur at lower frequencies. An additional novelty is that the dispersion of the signal points to a more distant source, or perhaps to unusual features in the star’s atmosphere. All of this leaves a lot of room for investigation.

    We also have to add possible radio frequency interference (RFI) into the mix, something the scientists at Arecibo are examining as observations continue. The possibility that we are dealing with a new category of M-dwarf flare is intriguing and would have obvious ramifications given the high astrobiological interest now being shown in these dim red stars.

    All of this needs to be weighed as we leave the SETI implications open. The Arecibo post notes that signals from another civilization are “at the bottom of many other better explanations,” as well they should be assuming those explanations pan out. But we should also keep our options open, which is why the news that the Breakthrough Listen initiative has now observed Ross 128 with the Green Bank radio telescope in West Virginia is encouraging.



    GBO radio telescope, Green Bank, West Virginia, USA

    No evidence of the emissions Arecibo detected has turned up in the Breakthrough Listen data. We’re waiting for follow-up observations from Arecibo, which re-examined the star on the 16th, and Mendez in an update noted that the SETI Institute’s Allen Telescope Array had also begun observations.

    SETI/Allen Telescope Array situated at the Hat Creek Radio Observatory, 290 miles (470 km) northeast of San Francisco, California, USA

    Seth Shostak tells us that the ATA has thus far collected more than 10 hours of data, observations which may help us determine whether the signal has indeed come from Ross 128 or has another source.

    “We need to get all the data from the other partner observatories to put all things together for a conclusion,” writes Mendez. “Probably by the end of this week.”
    [Shostak]

    Or perhaps not, given the difficulty of detecting the faint signal and the uncertainties involved in characterizing it. If you’re intrigued, an Arecibo survey asking for public reactions to the reception is now available.

    I also want to point out that Arecibo Observatory is working on a new campaign to observe stars like Ross 128, the idea being to characterize their magnetic environment and radiation. One possible outcome of work like that is to detect perturbations in their emissions that could point to planets — planetary magnetic fields could conceivably affect flare activity. That’s an intriguing way to look for exoplanets, and the list being observed includes Barnard’s Star, Gliese 436, Ross 128, Wolf 359, HD 95735, BD +202465, V* RY Sex, and K2-18.

    A final note: Arecibo is now working with the Red Dots campaign in coordination with other observatories to study Barnard’s Star, for which there is some evidence of a super-Earth mass planet. More on these observations can be found in this Arecibo news release.

    ESO Red Dots Campaign

    Centauri Dreams


    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Tracking Research into Deep Space Exploration

    Alpha Centauri and other nearby stars seem impossible destinations not just for manned missions but even for robotic probes like Cassini or Galileo. Nonetheless, serious work on propulsion, communications, long-life electronics and spacecraft autonomy continues at NASA, ESA and many other venues, some in academia, some in private industry. The goal of reaching the stars is a distant one and the work remains low-key, but fascinating ideas continue to emerge. This site will track current research. I’ll also throw in the occasional musing about the literary and cultural implications of interstellar flight. Ultimately, the challenge may be as much philosophical as technological: to reassert the value of the long haul in a time of jittery short-term thinking.

     
  • richardmitnick 5:20 pm on July 18, 2017 Permalink | Reply
    Tags: Bernard's Star, Centauri Dreams, , , Paul Gilster   

    From Red Dots: “Dreaming Peter van de Kamp’s dream” 

    Red Dots

    7.18.17
    by Paul Gilster, writer and author of “Centauri Dreams”
    Edited by Zaira M. Berdiñas

    1

    The Red Dots campaign to study Proxima Centauri, Barnard’s Star and Ross 154 gives us a cannily chosen set of targets. All red dwarfs much smaller than the Sun, these stars offer us the opportunity of atmospheric analysis of any planets discovered there by future space-and ground-based instruments because all are close. At 4.2 light years, Proxima Centauri is nearest to the Sun, but Barnard’s Star is a scant 6 light years out, making it the closest known star other than the three Alpha Centauri stars. Ross 154 comes in at just under 10 light years, still very much in the local neighborhood in astronomical terms.

    2
    The proper motion of Barnard’s Star between the years 1991 and 2007, an indication of its proximity to our own Solar System. No image credit.

    But it is not just their proximity that makes these stars interesting. We’d like to know how stars like this age, considering that young M-dwarfs can show strong flare activity. All three of these stars do, with Proxima Centauri and Ross 154 being catalogued as UV Ceti stars; i.e., stars that produce major flares every few days. Barnard’s Star is of a variable category known as BY Draconis, stars that show starspots, variations in luminosity and other activity.

    So consider the spread here. Proxima Centauri is thought to be about 4.85 billion years old, while Barnard’s Star is perhaps twice that. Ross 154, however, shows a high rate of rotation — 3.5 ± 1.5 km/s — that indicates a younger star, perhaps one less than a billion years old. Thus we have three stars and possible planets at markedly different stages of development, giving us the ability to take a deeper look into flare activity on M-dwarfs as they age, and to assess flare effects on planetary habitability, assuming Barnard’s Star and Ross 154 do have planets. We’ll also be investigating the prospects for multiple planets around Proxima Centauri itself.

    Barnard’s Star has already produced its own share of notoriety. Working at the Sproul Observatory (Swarthmore College, Pennsylvania), astronomer Peter van de Kamp examined 2,413 photographic plates of the star taken between 1916 and 1962. The astronomer observed what he believed to be a telltale wobble in the motion of Barnard’s Star that fit the profile of a planet about 1.6 times Jupiter’s mass in an orbit at 4.4 AU [1]. He would later suggest the possibility of two gas giants here [2], and by 1973, Oliver Jensen (University of British Columbia) and Tadeusz Ulrych had upped the number to three [3].

    4
    Peter van de Kamp (right) and the the 61 cm Sproul refracting telescope (left) he used in his work on Barnard’s Star.

    If confirmed, these would have been the first planets ever detected outside our Solar System, but it was not to be. Follow-up studies by George Gatewood (University of Pittsburgh) and John Hershey (also at the Sproul Observatory) found systematic errors in van de Kamp’s work. The culprit: Lens adjustments to the Swarthmore instrument that were later confirmed by Hershey when he found an identical wobble in the M-dwarf Gliese 793 [4]. Subsequent work by Gatewood and, later, Jieun Choi (UC Berkeley) would be able to detect no planets [5],[6].

    5
    Figure from Gatewood & Eichhorn that shows the disagreement between their data (black dots) and the model fitted by Van de Kamp using the data from the Sproul Observatory (dashed line).

    Peter van de Kamp’s tool was astrometry, meaning he used precise measurements in the proper motion of the star to look for the presence of planets, finding minute variations on photographic plates that were consistent with the hypothesis. His observational skills and persistence were rightly praised, but errors in his instrument negated what would have been a major discovery.

    So what do we have today? We can rule out gas giants at Barnard’s Star thanks to continuing Doppler monitoring, but we can’t yet rule out small rocky planets of the kind we are now turning up around other M-dwarfs in data from the Kepler mission.

    NASA/Kepler Telescope

    Kepler has shown us that planets of a few times Earth-mass are not uncommon, while a 2013 study by Ravi Kopparapu (Pennsylvania State) found that about half of all M-dwarfs should have Earth-size planets in the habitable zone[7]. What might Red Dots uncover around this tantalizingly close star?

    It was Peter van de Kamp’s work that helped the energetic team of starship designers behind the British Interplanetary Society’s Project Daedalus choose Barnard’s Star as their destination. And physicist Robert Forward, no stranger to fiction, would use a planetary system around Barnard’s Star as the setting for his novel ​Rocheworld​ (1984). The system is reached by a lightsail beamed by a laser array, a concept not unfamiliar to today’s Breakthrough Starshot (read the article by Avi Loeb), which envisions sending small sails by laser to Proxima Centauri.

    How fitting, then, that Red Dots should home in on this interesting system, along with a return to Proxima Centauri and a deep exploration of Ross 154 as well. Red dwarf stars like these account for as much as 80 percent of the stars in our galaxy. The new campaign will let us see, in real time, no less, just how this inspiring search of nearby dwarfs proceeds.

    References:

    van de Kamp, P. “Astrometric study of Barnard’s star from plates taken with the 24-inch Sproul refractor”, Astronomical Journal, 68, 515, (1963).
    van de Kamp, P. “Alternate dynamical analysis of Barnard’s star”, Astronomical Journal, 74, 757, (1969).
    Jensen, O. G. & Ulrych, T. “An analysis of the perturbations on Barnard’s Star”, Astronomical Journal, 78, 1104, (1973).
    Hershey, J. L. “Astrometric analysis of the field of AC +65 6955 from plates taken with the Sproul 24-inch refractor”, Astronomical Journal, 78, 421, (1973).
    Gatewood, G. & Eichhorn, H. “An unsuccessful search for a planetary companion of Barnard’s star BD +4 3561”, Astronomical Journal, 78, 769, (1973).
    Choi, J. et al. “Precise Doppler Monitoring of Barnard’s Star”, Astrophysical Journal, 764, 131, (2013).
    Kopparapu, R. K. “A Revised Estimate of the Occurrence Rate of Terrestrial Planets in the Habitable Zones around Kepler M-dwarfs”, Astrophysical Journal, 767, L8, (2013).

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    Red dots is a project to attempt detection of the nearest terrestrial planets to the Sun. Terrestrial planets in temperate orbits around nearby red dwarf stars can be more easily detected using Doppler spectroscopy, hence the name of the project.

    ESO 3.6m telescope & HARPS at LaSilla, 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO/HARPS at La Silla

    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker

     
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