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  • richardmitnick 11:35 am on August 15, 2017 Permalink | Reply
    Tags: , , , , , Detecting Exoplanet Life in Our Proximity, Proxima b   

    From astrobites: “Detecting Exoplanet Life in Our Proximity” 

    Astrobites bloc

    Astrobites

    8.15.17
    Mara Zimmerman

    1
    This artist’s interpretation shows the planet Proxima Centauri b around its host star. Proxima Centauri is actually part of a trinary system which includes the close binary Alpha Centauri AB. You can see Alpha Centauri AB in between the planet and star, as two faint white dots in the background. [ESO]

    Title: Detecting Proxima b’s Atmosphere with JWST Targeting CO2 at 15 Micron Using a High-Pass Spectral Filtering Technique
    Author: I.A.G. Snellen, J.M. D’esert, L.B.F.M. Waters, T. Robinson, et al.
    First Author’s Institution: Leiden Observatory, Leiden University, The Netherlands

    Leiden Observatory


    Status: Accepted to AJ, open access

    Proxima Centauri b and the Significance of CO2

    This summer marks the one-year anniversary of the detection of an exoplanet orbiting our solar system’s nearest stellar neighbor, Proxima Centauri. This Earth sized exoplanet, with the oh-so-imaginative name Proxima Centauri b, lies in the habitable zone of its M-dwarf star. As we’ve previously discussed, having such an Earth-like planet in our stellar backyard is really exciting, and astronomers are keen to explore the system as thoroughly as possible for potential signs of life. The cover image above shows an artist’s rendition of this intriguing exoplanet.

    Since the discovery of this close planet, researchers have been studying methods that might detect the presence of life on Proxima Centauri b. Today’s paper approaches this by devising a method to detect carbon dioxide (CO2) in the planet’s atmosphere. The authors focus on this particular molecule because it is one of the four main biomarkers used in evaluating habitability of exoplanets; water, methane, carbon dioxide, and oxygen are primarily produced during biological processes, so their presence in an atmosphere can imply life. In addition to being a biomarker molecule, CO2 has many distinguishable features that are visible in the 15 micron band, which JWST is equipped to look at.

    Snellen and collaborators present a technique that can be performed with the soon-to-be-launched James Webb Space Telescope (JWST), which would reveal the presence of CO2 in the atmosphere of this nearby exoplanet.

    NASA/ESA/CSA Webb Telescope annotated

    The emission in the 15 micron band will be ideal for detecting CO2, since this molecule has over 100 features within this band.

    JWST and High-Pass Spectral Filtering Techniques

    JWST is equipped with several extremely sensitive instruments. One of the goals of this mission is to detect and characterize atmospheres of exoplanets. With this in mind, these authors suggest using the medium resolution spectrograph (MRS) mode of the Mid-Infrared Instrument (MIRI) to detect CO2 markers in the atmosphere of Proxima Centauri b.

    3
    Figure 1: This shows an example planet spectrum and high-pass filtered spectrum. The high-pass image has more distinguishable features, which allows for greater sensitivity in molecule detection. [Snellen et al. 2017]

    This new technique combines several methods to attain greater sensitivity. The cross-correlation requires a high spectral resolution to find the radial component of the planet orbital velocity, used to filter out the planet’s signal. The authors’ method cross-correlates the observed spectrum with template spectra; however, the spectral resolution is not high enough to achieve this with Proxima Centauri b, so the authors suggest a slight modification: use this method while targeting a specific feature in the spectrum. Proxima Centauri b is believed to be tidally locked, meaning that the same hemisphere always faces the star. This means that at certain alignments, Proxima b will show a contrast of up to 100 ppm with respect to the star. This contrast will be helpful in separating planet signatures from the flux of the star. The method does not require absolute flux calibration, but only depends on the relative flux of the star and the planets. However, one limitation is that the stellar spectrum must be precisely known beforehand, since the flux of the planet, even at its highest, is much smaller than the stellar flux.

    The authors used atmospheric models of Proxima Centauri b to show the limits of their detection method in extreme cases and expected results which are shown in Figure 2.

    4
    Figure 2: Planet model spectra, assuming a standard Earth atmospheric model for the temperatures and gas mixing ratios. The temperature and pressure relation is shown on the right column. The left column has the observed spectra given the temperature profiles. The upper panel has stratospheric temperatures that are equal to the tropopause temperature; the middle panel shows a model for clear sky conditions with an Earth-like temperature profile; the lower panel shows the spectrum for high, thick cloud coverage, again with an Earth-like temperature profile. [Snellen et al. 2017]

    A Step Forward in the Search for Extraterrestrial Life

    If we can detect exoplanet life or a habitable exoplanet so close to Earth, this could tell us more about how common life is in our universe and the origins of life in different environments. Until we find a way to accurately detect the presence of life, such as detecting CO2 in atmospheres, we won’t know the extent of life in all parts of the universe. Though we don’t know for certain yet, I for one hope that we can soon discover and say hello to our new alien neighbors, hopefully on Proxima b!

    See the full article here .

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

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  • richardmitnick 12:04 pm on August 6, 2017 Permalink | Reply
    Tags: , , , , , , Proxima b   

    From NASA: “An Earth-like Atmosphere May Not Survive Proxima b’s Orbit” 

    NASA image
    NASA

    July 31, 2017
    Last Updated: Aug. 4, 2017
    Editor: Rob Garner

    1
    This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the solar system. The double star Alpha Centauri AB also appears in the image. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface.
    Credits: ESO/M. Kornmesser

    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker

    A newly discovered, roughly Earth-sized planet orbiting our nearest neighboring star might be habitable, according to a team of astronomers using the European Southern Observatory’s 3.6-meter telescope at La Silla, Chile, along with other telescopes around the world.

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

    The exoplanet is at a distance from its star that allows temperatures mild enough for liquid water to pool on its surface.

    Proxima b, an Earth-size planet right outside our solar system in the habitable zone of its star, may not be able to keep a grip on its atmosphere, leaving the surface exposed to harmful stellar radiation and reducing its potential for habitability.

    At only four light-years away, Proxima b is our closest known extra-solar neighbor. However, due to the fact that it hasn’t been seen crossing in front of its host star, the exoplanet eludes the usual method for learning about its atmosphere. Instead, scientists must rely on models to understand whether the exoplanet is habitable.

    One such computer model considered what would happen if Earth orbited Proxima Centauri, our nearest stellar neighbor and Proxima b’s host star, at the same orbit as Proxima b. The NASA study, published on July 24, 2017, in The Astrophysical Journal Letters, suggests Earth’s atmosphere wouldn’t survive in close proximity to the violent red dwarf.

    “We decided to take the only habitable planet we know of so far — Earth — and put it where Proxima b is,” said Katherine Garcia-Sage, a space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study. The research was supported by NASA’s NExSS coalition — leading the search for life on planets beyond our solar system — and the NASA Astrobiology Institute.

    2
    At its orbit, the exoplanet Proxima b likely couldn’t sustain an Earth-like atmosphere. Credits: NASA’s Goddard Space Flight Center/Mary Pat Hrybyk-Keith.

    Just because Proxima b’s orbit is in the habitable zone, which is the distance from its host star where water could pool on a planet’s surface, doesn’t mean it’s habitable. It doesn’t take into account, for example, whether water actually exists on the planet, or whether an atmosphere could survive at that orbit. Atmospheres are also essential for life as we know it: Having the right atmosphere allows for climate regulation, the maintenance of a water-friendly surface pressure, shielding from hazardous space weather, and the housing of life’s chemical building blocks.

    Garcia-Sage and her colleagues’ computer model used Earth’s atmosphere, magnetic field and gravity as proxies for Proxima b’s. They also calculated how much radiation Proxima Centauri produces on average, based on observations from NASA’s Chandra X-ray Observatory.

    NASA/Chandra Telescope

    With these data, their model simulates how the host star’s intense radiation and frequent flaring affect the exoplanet’s atmosphere.

    “The question is, how much of the atmosphere is lost, and how quickly does that process occur?” said Ofer Cohen, a space scientist at the University of Massachusetts, Lowell and co-author of the study. “If we estimate that time, we can calculate how long it takes the atmosphere to completely escape — and compare that to the planet’s lifetime.”

    An active red dwarf star like Proxima Centauri strips away atmosphere when high-energy extreme ultraviolet radiation ionizes atmospheric gases, knocking off electrons and producing a swath of electrically charged particles. In this process, the newly formed electrons gain enough energy that they can readily escape the planet’s gravity and race out of the atmosphere.

    Opposite charges attract, so as more negatively charged electrons leave the atmosphere, they create a powerful charge separation that pulls positively charged ions along with them, out into space.

    In Proxima Centauri’s habitable zone, Proxima b encounters bouts of extreme ultraviolet radiation hundreds of times greater than Earth does from the sun. That radiation generates enough energy to strip away not just the lightest molecules — hydrogen — but also, over time, heavier elements such as oxygen and nitrogen.

    The model shows Proxima Centauri’s powerful radiation drains the Earth-like atmosphere as much as 10,000 times faster than what happens at Earth.

    “This was a simple calculation based on average activity from the host star,” Garcia-Sage said. “It doesn’t consider variations like extreme heating in the star’s atmosphere or violent stellar disturbances to the exoplanet’s magnetic field — things we’d expect provide even more ionizing radiation and atmospheric escape.”

    To understand how the process can vary, the scientists looked at two other factors that exacerbate atmospheric loss. First, they considered the temperature of the neutral atmosphere, called the thermosphere. They found as the thermosphere heats with more stellar radiation, atmospheric escape increases.

    The scientists also considered the size of the region over which atmospheric escape happens, called the polar cap. Planets are most sensitive to magnetic effects at their magnetic poles. When magnetic field lines at the poles are closed, the polar cap is limited and charged particles remain trapped near the planet. On the other hand, greater escape occurs when magnetic field lines are open, providing a one-way route to space.

    “This study looks at an under-appreciated aspect of habitability, which is atmospheric loss in the context of stellar physics,” said Shawn Domagal-Goldman, a Goddard space scientist not involved in the study. “Planets have lots of different interacting systems, and it’s important to make sure we include these interactions in our models.”

    The scientists show that with the highest thermosphere temperatures and a completely open magnetic field, Proxima b could lose an amount equal to the entirety of Earth’s atmosphere in 100 million years — that’s just a fraction of Proxima b’s 4 billion years thus far. When the scientists assumed the lowest temperatures and a closed magnetic field, that much mass escapes over 2 billion years.

    “Things can get interesting if an exoplanet holds on to its atmosphere, but Proxima b’s atmospheric loss rates here are so high that habitability is implausible,” said Jeremy Drake, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics and co-author of the study. “This questions the habitability of planets around such red dwarfs in general.”

    Red dwarfs like Proxima Centauri or the TRAPPIST-1 star are often the target of exoplanet hunts, because they are the coolest, smallest and most common stars in the galaxy. Because they are cooler and dimmer, planets have to maintain tight orbits for liquid water to be present.

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

    But unless the atmospheric loss is counteracted by some other process — such as a massive amount of volcanic activity or comet bombardment — this close proximity, scientists are finding more often, is not promising for an atmosphere’s survival or sustainability.

    For more information, go to:

    https://exoplanets.nasa.gov

    See the full article here .

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    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

     
  • richardmitnick 10:09 am on July 19, 2017 Permalink | Reply
    Tags: "Top five places to look for extraterrestrial life, , , , Proxima b, The moon Titan,   

    From COSMOS: “Top five places to look for extraterrestrial life” 

    Cosmos Magazine bloc

    COSMOS Magazine

    19 July 2017
    Andrew Masterson

    For all the hope and expectation, it is sobering to recall that, despite the best efforts of scientists and engineers, there is still no evidence that life exists anywhere beyond our own planet. There are, however, some planetary prime suspects. Here are the five places astronomers and astrobiologists think are the best chances for harbouring ET.

    1
    An artist’s impression of “rocky super-Earth” LHS 1140b and its red dwarf host. M. Weiss/CfA

    LHS 1140b

    News of this planet, a “rocky super-earth”, was announced in the journal Nature in April. Orbiting a red dwarf 39 light-years from Earth, the planet sits in its star’s habitable zone and has an estimated mass almost seven times that of our own planet, leading to the assumption that it comprises rock encasing a solid iron core. According to Jason Dittmann of the Harvard Smithsonian Centre for Astrophysics in Massachusetts, US, LHS 1140b’s density means it might have survived the runaway global warming thought to denude many red dwarf planets. If so, it might now boast a stable atmosphere and liquid water. “This is the most exciting exoplanet I’ve seen in the past decade,” he said. “We could hardly hope for a better target to perform one of the biggest quests in science – searching for evidence of life beyond Earth.”

    4
    Enceladus Curtains: Comparing Data and Simulation. http://photojournal.jpl.nasa.gov/catalog/PIA19061.

    Enceladus

    Thanks to data from NASA’s Cassini spacecraft, Saturn’s moon Enceladus has emerged as every ET-hunter’s favourite target – mainly due to the strong likelihood that it features a subterranean ocean. In April this year, a team of scientists from the South West Research Institute (SWRI) in Texas, US, revealed a plume of hydrogen erupting from the moon’s surface. The plume may well be evidence of hydrothermal vents in the subsurface ocean – the same type of vents that support extremophile life on earth. “The discovery of hydrogen gas and the evidence for ongoing hydrothermal activity offer a tantalising suggestion that habitable conditions could exist beneath the moon’s icy crust,” says principal investigator Hunter Waite.

    In its final swoop close to the surface of Enceladus, NASA’s Cassini spacecraft has delivered a stunning cliffhanger by detecting the most remarkable hints yet that there may be life on Saturn’s sixth-largest moon.

    That swoop took place in October 2015, but research published this month in Science reveals that the spacecraft – which is due to end its 22-year mission by plunging into the planet’s surface in a few months – detected hydrogen gas in a plume of material erupting from the moon’s surface.

    3
    Hovering over Titan. NASA.

    Titan

    Another of Saturn’s 53 moons, Titan is known to have permanent hydrocarbon lakes, a nitrogen-heavy atmosphere, and possibly a subsurface ocean beneath a salty crust. It is a possible host for either water-dependent or methane-dependent life.

    6

    Proxima-b

    https://cosmos-magazine.imgix.net/file/spina/photo/10883/170628_ProximaB_Full.jpg?fit=clip&w=835
    Artist’s impression of the planet orbiting Proxima Centauri. ESO/M. KORNMESSER / GETTY.

    This planet, discovered in August 2016, orbits the star Proxima Centauri, 4.2 light-years away from our sun, and is the nearest candidate beyond the solar system for hosting ET. Research in May’s Astronomy & Astrophysics journal found the chances of life existing on the planet may hinge on its orbital speed. Astrophysicists at the University of Exeter calculated that if Proxima-b rotates on its axis three times for every two times it orbits its sun, then the chances of it being habitable are substantially improved.

    4
    TRAPPIST-1 planet lineup. NASA.

    The announcement of the Trappist-1 system in February, with seven rocky planets orbiting an ultracool dwarf star, sent ripples of excitement through astrobiologists everywhere. At least three of the planets looked like they were within the star’s habitable zone. The latest analysis, by Eric Wolf from the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder, US, has somewhat dampened expectations, suggesting that only one of the group has life-sustaining potential. But never mind: one chance in seven is still better than no chance at all.

    See the full article here .

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  • richardmitnick 9:54 am on May 16, 2017 Permalink | Reply
    Tags: , , , , , Proxima b   

    From COSMOS: “Exoplanet’s rotation speed may hold key to life” 

    Cosmos Magazine bloc

    COSMOS

    16 May 2017
    Andrew Masterson

    1
    An artist’s impression of the surface of Proxima-B. ESO / M. Kornmesser

    How fast the exoplanet Proxima-B rotates on its axis could determine its climate and the possibility of it containing life.

    The planet, discovered in August 2016, orbits the star Proxima Centauri, 4.2 million light-years from the Sun and is thought to be the closest candidate beyond the Solar System for hosting extraterrestrial life.

    A new study published in Astronomy and Astrophysics, using the complex weather and climate modeling tools that comprise the UK Met Office’s Unified Model, indicates Proxima-B’s atmospheric stability is affected by how often it rotates compared to how often it orbits its host star.

    The research, led by Ian Boutle, found Proxima-B’s rotational speed – known as “resonance” – significantly affected the area of the planet’s surface that could sustain liquid water, considered to be a critical precursor for life to exist.

    Previous studies have picked Proxima-B as a prime life candidate because the Earth-sized planet orbits its star within the “habitable zone”, a distance far enough from Proxima Centauri to prevent water vapour boiling away but close enough to stop it turning to ice.

    Whether the planet actually has water vapour is, of course, unconfirmed – a probe would have to travel more than 50 million kilometres to get close enough to take a cloud sample.

    The researchers therefore derived their conclusions from two possible atmospheric models – one similar to Earth’s, and another comprising just nitrogen with a small amount of carbon dioxide. They then used the Unified Model to run the numbers on a range of possible orbit-to-rotation variations – known as “eccentricities”.

    One possibility considered was a “tidally locked” scenario, in which the rotational period matched the orbital period. The Moon is an excellent example here: its rotation of the Earth lasts exactly as long as its orbit, which is why we always only see one side of it.

    Another modelled eccentricity is known as a 3:2 resonance. In this scenario Proxima-B would rotate three times during every two orbits around the star. This is similar to Mercury’s behaviour.

    The researchers also factored in the fact that light from Proxima Centauri sits much more towards the infrared end of the spectrum than light from the Sun.

    “These frequencies of light interact much more strongly with water vapour and carbon dioxide in the atmosphere,” explains co-author James Manners, “which affects the climate that emerges in our model.”

    The results of the computer simulations show very stable atmospheres produced by both the tidally locked and 3:2 models, but with the latter resulting in much larger areas of the planet being potentially habitable.

    See the full article here .

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  • richardmitnick 12:38 pm on March 28, 2017 Permalink | Reply
    Tags: A Cosmic Beach Getaway, , , , Escape velocity, Proxima b   

    From astrobites: “A Cosmic Beach Getaway” 

    Astrobites bloc

    Astrobites

    Mar 28, 2017
    Emily Sandford

    Title: The cosmic shoreline: The evidence that escape determines which planets have atmospheres, and what this may mean for Proxima Centauri b
    Authors: Kevin J. Zahnle and David C. Catling
    First author’s institution: NASA Ames Research Center, USA

    Status: Posted to arXiv (2017) [open access]

    Escaping from prison is hard. First, you have to convince your skeptical friend to smuggle you a rock hammer and a big poster of Rita Hayworth. Then you have to spend 20 years digging a tunnel through your cell wall by night and laundering money for your despotic warden by day. You’re not even done after you crawl half a mile through a sewer pipe to break out, because you have to hike into the cornfields in a business suit to leave an inspirational note under a rock for your friend.

    Escaping from Earth, on the other hand, is easy. All you have to do is go up at 25,000 miles per hour. Admittedly, that’s challenging when you’re heavy, like an Atlas V rocket, because it takes a lot of energy to make a heavy thing go fast. But when you’re light, like a hydrogen molecule, even a little jolt of energy from a ray of sunlight can free you from Earth’s gravity.

    For a planet, therefore, hanging on to an atmosphere becomes a somewhat delicate proposition. Being very massive helps, because it means that the planet’s gravity is stronger, so atmosphere molecules have to reach higher speeds to escape it. Being farther away from the star helps, too, because the starlight which reaches the planet is dimmer and less able to evaporate the atmosphere.

    So what separates planets that successfully hang on to atmospheres from planets that don’t? And are the planets in our own Solar System, both “atmosphered” and not, a good guide to planets beyond?

    Drawing a line in the sand

    The authors start by taking every big object in the solar system–planets, dwarf planets, moons, asteroids–and plotting, very colorfully, the energy it receives from the Sun (“insolation”) against the strength of its gravity. They measure gravity strength by the speed you’d have to reach to escape from the planet (“escape velocity”).

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    Figure 1: “Insolation” (energy received from starlight) vs. “escape velocity” (the speed at which you’d have to travel to escape the object’s gravity). The color-coding marks objects belonging to the same mass category (Saturn-sized, Neptune-sized, Earth-sized, dwarf-planet-sized, asteroid-sized). The turquoise line is the “cosmic shoreline.” (You can ignore the non-turquoise lines, which get into details about the chemical makeup of various atmospheres.)

    The first thing to notice is that the objects with atmospheres (the filled-in symbols: Earth, Jupiter, Neptune, Pluto, Titan, etc.) separate surprisingly neatly from those without (the hollow symbols: Mercury, the Moon, the asteroids, etc.). The authors draw a nice turquoise line, which they term the “cosmic shoreline,” to mark the boundary, and then they draw a bunch of other lines because they hate your eyes.

    This tidy cosmic shoreline is just something the authors noticed, not a fit to the data, but it hints that the authors may be on to something. If a planet’s ability to hang on to an atmosphere (or not!) depended on the amount of atmosphere it was born with, or the amount of gas deposited onto it by comets crashing into it, then insolation and escape velocity wouldn’t tell us much at all. But they do, which means that the strength of a planet’s gravity and the amount of energy it receives from its star really are determining factors.

    Hanging out on the beach

    Next, the authors take every exoplanet in the universe of which we’ve measured the escape velocity and toss those on the plot as well. (There are relatively few of these, even though we’ve discovered thousands of exoplanets, because measuring the escape velocity is difficult–it requires a measurement of mass and an independent measurement of size.) We can’t yet observe most of these exoplanets in enough detail to know what their atmospheres are like, but we deduce that they do have atmospheres, because their masses and sizes are consistent with the gas giants of the Solar System.

    To their surprise, they find that the exoplanets more or less fall on the cosmic shoreline. This is weird because they have to extrapolate the shoreline quite a ways up and to the right to get to the exoplanets. All the exoplanets fall in the upper right corner because big exoplanets (high escape velocity) orbiting close to their host stars (high insolation) are the easiest ones to discover, so they’re the ones we’ve found and studied so far.

    Once these big, hot exoplanets are added, the cosmic shoreline runs from the tiny icy bodies of the Solar System to the hot Jupiters, a hundred million times more insolated. That’s a lot of real estate for one trend to cover–it’s a simplistic picture, but an intriguing one nonetheless.

    If we trust the cosmic shoreline, it might have major implications for exoplanet exploration: Proxima b, our nearest exoplanet neighbor, is right on the beach with the other atmosphered planets. A cosmic Zihuatanejo?

    See the full article here .

    Please help promote STEM in your local schools.

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 8:32 am on January 9, 2017 Permalink | Reply
    Tags: , , Proxima b   

    From COSMOS: “‘Goldilocks’ planets might not be so nice” 

    Cosmos Magazine bloc

    COSMOS

    06 January 2017
    Katie Mack

    1
    This artist’s impression shows the planet Proxima b orbiting the red dwarf star Proxima Centauri. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface. ESO / M. Kornmesser

    The recent discovery of a planet around Proxima Centauri, the closest star to our own sun, created immense excitement. Not only was the new world, called Proxima Centauri b (Proxima b for short), conveniently close to us – only about four light-years away – it was roughly the mass of Earth and just the right distance from its host star. A “habitable planet”!

    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker
    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker

    But don’t fire up the generation ships just yet.

    In the study of alien worlds, there is perhaps no designation more hopeful, or more misleading, than “habitable”. While it evokes a vision of a pleasant, temperate world, complete with breathable air and a human-friendly landscape, to an astronomer it means none of those things. While we would certainly classify our own planet as habitable, the term could be applied to any of a wide range of lethal nightmare planets, and Proxima b might be one of them.

    We don’t really know what a planet needs to harbour life. Worlds inhospitable to humanity could be teeming with a kind of life we can’t even understand, possibly more alien than the “extremophile” life forms that populate subglacial lakes and hydrothermal vents. All we know is that for the kind of life that exists on Earth, liquid water is a necessity – at least intermittently.

    ___________________________________________________________________

    While we would classify our own planet as habitable, the term could be applied to a wide range of lethal nightmare planets.
    ___________________________________________________________________

    With current technology, we don’t have the capability to conclusively detect liquid water on the surface of any worlds outside our own solar system, so we have to work with the information we have – the temperature of the star and the distance of the planet’s orbit. A planet too close to its star might be so hot that water would immediately boil off. Too far away, and it’s a solid ice world. The habitable zone is the sweet spot, the Goldilocks zone, in which the amount of starlight reaching the planet is just enough to allow water to exist on the surface in liquid form.

    But there are some caveats, and they’re big. Distance isn’t everything when it comes to the temperature on a planet’s surface. In our own solar system, both Venus and Mars are often considered to be in the habitable zone. However, Venus has such a suffocatingly thick atmosphere that it’s undergone a runaway greenhouse effect; its surface is a sweltering 460 °C. The present-day atmosphere of Mars is so thin that liquid water can only appear briefly in salty rivulets on crater slopes on the warmest days of the year.

    Studying the atmosphere of exoplanets is difficult. So far we’ve only been able to examine a tiny number of atmospheres, and none belong to rocky worlds in the habitable zone. But a problematic atmosphere isn’t the only thing that can render a world uninhabitable. In many cases, we don’t know for certain if a planet has a surface at all. In the case of Proxima b, we can tell that it’s at least 1.3 times as massive as Earth – and no more than three times – but if it’s over two, it’s probably more like Neptune, forgoing any solid surface for a thick gas and liquid envelope over a small, deep, rocky core.

    Another wild card for Proxima b is its host star. Proxima Centauri is a red dwarf, much cooler and smaller than our Sun. This means Proxima Centauri’s habitable zone lies very close to it – so close that the gravitational interaction between it and its planet is extreme enough that Proxima b is probably tidally locked. This means that the same side of the planet faces the star at all times, in the same way our moon always shows us its same face.

    On such a world, rather than a temperate, circulating atmosphere, the day side might be boiling and the night side frozen. Even worse, Proxima Centauri is a flare star, meaning that it sends out giant flares of stellar material into space with alarming frequency. Even if Proxima b had a perfectly good atmosphere to begin with, it may have been stripped by its star’s unruly outbursts.

    With future telescopes, some of them already under construction, we might soon be able to peer directly at Proxima b to analyse its atmosphere. In the meantime, we can only speculate and search for more habitable planets in the hope of learning more about our own origins. Perhaps someday we’ll find unmistakable signs of life on another world.

    See the full article here .

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  • richardmitnick 10:50 am on November 8, 2016 Permalink | Reply
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    From Astronomy Now: “Breakthrough Listen searches new-found nearby planet Proxima b for signs of ET” 

    Astronomy Now bloc

    Astronomy Now

    8 November 2016
    No writer credit found

    1
    The 64-metre-wide Parkes Radio Telescope in New South Wales, Australia is affectionately known as “The Dish.” It played an iconic role in receiving the first deliberate transmissions from the surface of another world, as the astronauts of Apollo 11 set foot on our Moon. Now, Parkes joins once again in expanding human horizons as we search for the answer to one of our oldest questions: Are we alone? Image credit: Parkes Radio Telescope © 2005 Shaun Amy.

    Breakthrough Listen, the 10-year, $100-million astronomical search for intelligent life beyond Earth launched in 2015 by Internet entrepreneur Yuri Milner and Stephen Hawking, today announced its first observations using the Parkes Radio Telescope in New South Wales, Australia.

    Parkes joins the Green Bank Telescope (GBT) in West Virginia, USA, and the Automated Planet Finder (APF) at Lick Observatory in California, USA, in their ongoing surveys to determine whether civilisations elsewhere have developed technologies similar to our own.

    gbo-logo
    GBO radio telescope, West Virginia, USA
    GBO radio telescope, West Virginia, USA

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

    Parkes radio telescope is part of the Australia Telescope National Facility, owned and managed by Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO).

    Drawing on over nine months of experience in operation of the dedicated Breakthrough Listen instrument at GBT, a team of scientists and engineers from the University of California, Berkeley’s SETI Research Center (BSRC) deployed similar hardware at Parkes, bringing Breakthrough Listen’s unprecedented search tools to a wide range of sky inaccessible from the GBT. The Southern Hemisphere sky is rich with targets, including the centre of our own Milky Way galaxy, large swaths of the galactic plane, and numerous other galaxies in the nearby universe.

    “The Dish” at Parkes played an iconic role in receiving the first deliberate transmissions from the surface of another world, as the astronauts of Apollo 11 set foot on our Moon. Now, Parkes joins once again in expanding human horizons as we search for the answer to one of our oldest questions: Are we alone?

    “The Parkes Radio Telescope is a superb instrument, with a rich history,” said Pete Worden, Chairman of Breakthrough Prize Foundation and Executive Director of the Breakthrough Initiatives. “We’re very pleased to be collaborating with CSIRO to take Listen to the next level.”

    With its new combined all-sky range, superb telescope sensitivity and computing capacity, Breakthrough Listen is the most powerful, comprehensive, and intensive scientific search ever undertaken for signs of intelligent life beyond Earth.

    Moreover, this expansion of Breakthrough Listen’s range follows the announcement on 12 October that it will be joining forces with the new FAST telescope — the world’s largest filled-aperture radio receiver — to coordinate their searches for artificial signals. The two programs will exchange observing plans, search methods and data, including the rapid sharing of promising new signals for additional observation and analysis. The partnership represents a major step toward establishing a fully connected, global search for intelligent life in the universe.

    “The addition of Parkes is an important milestone,” said Yuri Milner, founder of the Breakthrough Initiatives, which include Breakthrough Listen. “These major instruments are the ears of planet Earth, and now they are listening for signs of other civilisations.”

    First light focused on exo-Earth

    After 14 days of commissioning and test observations, first light for Breakthrough Listen at Parkes was achieved on 7 November, with an observation of the newly-discovered Earth-size planet orbiting the nearest star to the Sun. Proxima Centauri, a red dwarf star 4.2 light-years from Earth, is now known to have a planet (“Proxima b”) within its habitable zone — the region where water could exist in liquid form on the planet’s surface. Such “exo-Earths” (habitable zone exoplanets) are among the primary targets for Breakthrough Listen.

    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker
    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker

    “The chances of any particular planet hosting intelligent life-forms are probably minuscule,” said Andrew Siemion, director of UC Berkeley SETI Research Center. “But once we knew there was a planet right next door, we had to ask the question, and it was a fitting first observation for Parkes. To find a civilisation just 4.2 light-years away would change everything.”

    As the closest known exoplanet, Proxima b is also the current primary target for Breakthrough Listen’s sister initiative, Breakthrough Starshot, which is developing the technology to send gram-scale spacecraft to the nearest stars.

    “Parkes is one of the most highly cited radio telescopes in the world, with a long list of achievements to its credit, including the discovery of the first ‘fast radio burst.’ Parkes’ unique view of the southern sky, and cutting-edge instrumentation, means we have a great opportunity to contribute to the search for extra-terrestrial life,” said Douglas Bock, Director of CSIRO Astronomy and Space Science.

    See the full article here .

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  • richardmitnick 5:05 pm on September 12, 2016 Permalink | Reply
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    From Many Worlds: “Proxima b Is Surely Not “Earth-like.” But It’s A Research Magnet And Just May Be Habitable” 

    NASA NExSS bloc

    NASA NExSS

    Many Words icon

    Many Worlds

    1
    A simulated comparison of a sunset on Earth and Proxima b. The images sets out to show that the red-dwarf star Proxima Centauri appears almost three times bigger than our sun in a redder and darker sky. There is value in illustrating how conditions in different solar systems would change physical conditions on the planets, but there is a real danger that the message conveyed becomes the similarities between planets such as Earth and Proxima b. At this point, there is no evidence that Proxima b is “Earth-like” at all. The original photo of the beach was taken at Playa Puerto Nuevo in Vega Baja, Puerto Rico. (PHL @ UPR Arecibo))

    It is often discussed within the community of exoplanet scientists that a danger lies in the description of intriguing exoplanets as “Earth-like.”

    Nothing discovered so far warrants the designation, which is pretty nebulous anyway. Size and the planet’s distance from a host star are usually what earn it the title “Earth-like,” with its inescapable expectation of inherent habitability. But residing in a habitable zone is just the beginning; factors ranging from the make-up of the planet’s host star to the presence and content of an atmosphere and whether it has a magnetic field can be equally important.

    The recent announcement of the detection of a planet orbiting Proxima Centauri, the closest star to our own, set off another round of excitement about an “Earth-like” planet.

    Pale Red Dot
    Pale Red Dot project

    It was generally not scientists who used that phrase — or if they did, it was in the context of certain “Earth-like” conditions. But the term nonetheless became a kind of shorthand for signalling a major discovery that just might some day even yield a finding of extraterrestrial life.

    Consider, however, what is actually known about Proxima b:

    The planet, which has a minimum mass of 1.3 Earths and a maximum of many Earths, orbits a red dwarf star. These are the most common class of star in the galaxy, and they put out considerably less luminosity than a star like our sun — about one-tenth the power.

    These less powerful red dwarf stars tend to have planets orbiting much closer in than a larger star. Proxima b, for instance, circles the star in 11.3 days.

    A consequence of this proximity is that the planet is undoubtedly tidally locked by the gravitational forces of the star — meaning that the planet does not rotate like Earth does but rather has a daytime and nighttime side like our moon. Some now argue that a tidally locked planet could theoretically be habitable, but the consensus seems to be that it is an obstacle to habitability rather than a benefit.

    The authors of the Proxima b paper make clear that evidence that the planet is rocky (as opposed to gaseous) is limited, and that’s why they label it as a “candidate terrestrial planet.”

    So to describe Proxima b as “Earth-like” seems unfortunate to me, and prone to giving the public the misguided impression of a planet with blue skies, oceans, and fish swimming in them. Proxima b may have some very broadly defined characteristics that parallel Earth, but so do many other exoplanets that are definitely not habitable. And therein lies the really interesting part.

    Before getting into that area, it should be made clear that the Proxima b detection was a game-changer, a discovery of historic proportions. It was and will be for a long time.

    The detection, after all, provides the nearest opportunity possible for beginning to understand the extraordinary complexities of what makes a planet truly habitable — something that is far from understood today. And later, Proxima b may become a petri dish of sorts for identifying and measuring chemical signatures that could be a byproduct of some kind of life.

    These are difficult tasks, to say the least, and will take an army of scientists years to come up with answers. But the good news is that the exoplanet field has already begun publishing papers on the dynamics and possible habitability of Proxima b, and they provide beginning insights into the issues, the excitement and the untold difficulties associated with this grandest of scientific chases.

    2
    The detection of Proxima b has been met with enormous enthusiasm in the exoplanet community. Some call it the biggest discovery since the detection of 51 Pegasi a, the first exoplanet to be positively identified. Detecting a planet, however, is just the beginning of the still unsettled process of determining its history and current makeup, and whether or not it might be habitable. (ESO/L.Calçada/Nick Risinger)

    Two Proxima papers that appeared soon after the August 24 announcement came from the University of Washington’s Virtual Planetary Laboratory. Supported by the NASA Astrobiology Institute since 2000, it is a leader in exoplanet research, modelling and habitability The team, directed by Victoria Meadows, received the Proxima detection paper before it was released because of longstanding relationships with the lead author, Guillem Anglada-Escude.

    The two papers from the VPL team — one with Meadows in the lead and the other organized by University of Washington astronomer Rory Barnes — take broad, interdisciplinary approaches to the planet.

    “Part one is what happened to this planet over time — what can we learn about its history, its evolution?” Meadows said. “Part two is what does the history mean for the current environment right now? We need photo-chemical models of what might be present, and then we have to look at what instruments we would need to detect what is decided we should be looking for.”

    The Barnes paper is here and the Meadows paper is here.

    The two take on different tasks, but really are one. Both start with an appreciative nod to what will quickly become the planet that scientists want to study, and then they go into the extraordinary complexity of the task ahead.

    As Barnes and his team concluded, a major obstacle to habitability on Proxima b is the well documented evolution of red dwarf stars.

    While their energy output is relatively low when mature, they go through early phases when they are much brighter and send out enormous solar flares that can double their brightness in a matter of minutes. Barnes said these intense phases could easily sterilize a close-in planet, leaving it incapable of evolving into a potentially living world even if, a billion years later, conditions for life were much more favorable.

    “The planet is in a habitable zone and so could have had liquid water, but my biggest concern is the retention of that water,” Barnes said of Proxima b. “If the planet was formed in its current orbit, then it was baked enough for 100, 200 million years to form a runaway greenhouse effect.” A different dynamic resulted in the same results on Venus, which once was wet but now is super-hot and parched.

    This leads to the next big question: Could Proxima b have been formed elsewhere, and was later pushed or pulled to its current location? Barnes said it is certainly possible that the planet spent its early years much further from Proxima Centauri, and he said that the (relatively) nearby presence of much larger star Alpha Centauri A and B certainly could have had dramatic effects on the locations and evolution of the planet.

    For these reasons and many more, Barnes said, there is absolutely no way to conclude now that Proxima b either is, or is not, potentially habitable.

    3
    This artist’s impression shows a view of the surface of the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB
    also appears in the image to the upper-right of Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature issuitable for liquid water to exist on its surface. (ESO/M. Kornmesser)

    The VPL group specializes in modeling possible planetary scenarios based on particular proposed condition. The team gets an idea of whether a planet might be habitable based on the history and potential current atmospheric and surface characteristics introduced into the model.

    In the paper she led, Meadows and her team reported:

    “We used coupled climate-photochemistry models to simulate several plausible states for the current environment of Proxima Cen b, for those various evolutionary scenarios. We find several post-runaway {greenhouse} states that are uninhabitable either due to extreme water loss or inclement surface temperatures. In particular, a dense Venus-like CO2 atmosphere will result in extremely high surface temperatures at Proxima Cen’s current semi-major axis.

    “However, several evolutionary scenarios may lead to possibly habitable planetary environments, including O2-rich atmospheres that retain a remnant ocean after extreme water loss.”

    It’s a conclusion parallel to that of Rory Barnes — that we have no idea now whether Proxima b might be habitable — but it moves the discussion further by describing scenarios where the planet definitely would not be habitable, and some where it just might be.

    These are essential guidepost for astronomers to know when actually observing Proxima b, which will surely become a target for many a telescope. To make an important discovery, it’s definitely useful to know what you’re looking for.

    Meadows also looked into which telescopes have capacities to make the needed observations, and concluded that large ground-based telescopes have a role to play, though with current technology it will be a very challenging one. But given the possible results, she said, “I can’t image they wouldn’t make the upgrades happen as fast a possible.”

    And then there’s the James Webb Space Telescope (JWST), due to launch in 2018. Because it observes in the infrared section of the spectrum, it is able to measure heat signatures with precision. And that opens some exciting possibilities.

    NASA/ESA/CSA Webb Telescope annotated
    NASA/ESA/CSA Webb Telescope annotated

    4
    This picture combines a view of the southern skies over the European Southern Observatory’s 3.6-metre telescope at the La Silla Observatory in Chile with images of the stars Proxima Centauri (lower-right) and the double star Alpha Centauri AB (lower-left) from the NASA/ESA Hubble Space Telescope. Proxima Centauri is the closest star to the Solar System and is orbited by the planet Proxima b, which was discovered using the HARPS instrument on the ESO 3.6-metre telescope. (Y. Beletsky (LCO)/ESO/ESA/NASA/M. Zamani)

    Meadows laid them out, and so did and so did Harvard astronomer Laura Kreidberg, in a paper for The Astrophysical Journal with Harvard-Smithsonian Center for Astrophysics theoretical physicist and cosmologist Abraham Loeb.

    As Loeb explained in an email: “As the planet orbits around the star, we should see a changing fraction of its day side, similarly to the phases of the Earth’s moon. The changing color of the planet as it orbits the star provides evidence for the temperature contrast between its day and night sides.

    “This contrast has an extreme value for bare rock, but is moderated by an atmosphere or an ocean that transfers heat across the planet’s surface. Our paper shows that JWST will be able to distinguish between these cases with high significance after observing the planet for a full orbital time of 11 days.”

    In other words, the temperature difference between the planet’s day side and its night side will be larger than expected if there is no atmosphere., and lower than expected if there is.

    Determining that there is an atmosphere present, Loeb said, would substantially increase the chances that Proxima b is, or once was, habitable. The first order would be to look for things like oxygen, water vapor, and methane, which could indicate habitable conditions if not active biological processes.

    This is a very difficult task because it requires the ability to catch starlight as it bounces off or filters through the planet’s atmosphere. He said that while the JWST might be able to detect a few compounds including ozone, full atmospheric analysis will have to wait for future ground-based observatories like the European Extremely Large Telescope, which is expected to see first light in the mid-2020s.

    ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile
    ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile

    Ultimately, it will take a direct imaging space telescope like the one being proposed for a launch in the 2030s to answer many of the important questions.

    So the process of getting to really know Proxima b, of learning more than its promising but less-than-revealing location and mas,s is about to begin.

    It’s exciting for sure, and not because Proxima b is “Earth-like.” Rather, there’s the real possibility of finding a habitable planet that — except in some grand-scale structural ways — is really not so “Earth-like” at all.

    See the full article here .

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    About Many Worlds

    There are many worlds out there waiting to fire your imagination.

    Marc Kaufman is an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer, and is the author of two books on searching for life and planetary habitability. While the “Many Worlds” column is supported by the Lunar Planetary Institute/USRA and informed by NASA’s NExSS initiative, any opinions expressed are the author’s alone.

    This site is for everyone interested in the burgeoning field of exoplanet detection and research, from the general public to scientists in the field. It will present columns, news stories and in-depth features, as well as the work of guest writers.

    About NExSS

    The Nexus for Exoplanet System Science (NExSS) is a NASA research coordination network dedicated to the study of planetary habitability. The goals of NExSS are to investigate the diversity of exoplanets and to learn how their history, geology, and climate interact to create the conditions for life. NExSS investigators also strive to put planets into an architectural context — as solar systems built over the eons through dynamical processes and sculpted by stars. Based on our understanding of our own solar system and habitable planet Earth, researchers in the network aim to identify where habitable niches are most likely to occur, which planets are most likely to be habitable. Leveraging current NASA investments in research and missions, NExSS will accelerate the discovery and characterization of other potentially life-bearing worlds in the galaxy, using a systems science approach.
    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

     
  • richardmitnick 11:32 am on September 4, 2016 Permalink | Reply
    Tags: , , , , Proxima b   

    From Astronomy: “How can we get to Proxima Centauri b?” 

    Astronomy magazine

    Astronomy.com

    September 01, 2016
    Corey S Powell

    1

    Sometimes it takes a while for the meaning of a new scientific discovery to really sink in. In the case of the planet Proxima Centauri b, announced last week, it may take decades or even centuries to fully grasp the importance of what we have found. You see, this is not just any planet: It is similar to Earth in mass, and it orbits its star in the “habitable zone,” where temperatures could potentially allow the existence of Earthlike bodies of liquid water. Proxima Centauri is not just any star, either: It is the very nearest one after the Sun, and it is a small red orb whose feeble light makes it relatively easy to study the planet close beside it.

    The science at stake here is enormous. Proxima Centauri b will surely become the archetype for understanding more distant Earth-size, and possibly Earth-like, planets all across our galaxy. The effort needed to study it will be enormous, too, however. At present the planet cannot even be glimpsed directly through the mightiest telescopes on Earth. Nevertheless, the race is on–a thrilling but maddeningly slow-motion race to bring Proxima Centauri into view, to figure out if it could (or does!) support life, even to visit it with an interstellar probe.

    That last goal is the most ambitious; some might call it the most absurd. But the discovery of Proxima Centauri b comes at a propitious time, just as a group of physicists and engineers have been thinking very realistically about how to send a space probe to another star, and to do it within a single human lifetime. The resulting Breakthrough Starshot concept would use an array of extremely high-power lasers to shoot a beam at a huge, extremely thin reflective sail. Energy from the beam would accelerate the sail (and a miniature probe attached to it) to 1/5 the speed of light, more than 1,000 times faster than anything humans have yet achieved.

    2
    Breakthrough Starshot concept would use a giant Earth-based laser array to accelerate a space sail to a significant fraction of the speed of light. Destination: Proxima Centauri b? (Credit: Breakthrough Initiatives)

    I worked with Philip Lubin of the University of California at Santa Barbara to develop a popular-level summary of how the Starshot would work. You can read about it here. If you want to dig into the more technical details of the project, Lubin also has a much longer paper posted online. This proposal envisions technology beyond what is available today, but there are no science-fiction elements in it. No warp drive, no wormholes. It is a straight extrapolation from things we know and do right now, just executed on a vastly greater scale—which is broadly similar to where the idea of going to the moon was around 1950.

    In other words, we don’t know how to build a Starshot yet, but at least we know where to start. If we invested seriously in the project—on the order of $20 billion total, more than the Large Hadron Collider but far less than the International Space Station—and got started right away, Lubin and other researchers guesstimate that we could have the technology ready in three decades. I’ll be more conservative and add another two decades to allow for all the full suite of components: In addition to the phased laser array you need the the energy-collecting sails, the probes themselves, and a “mothership” to carry them into orbit before interstellar launch. Just this week, a group of Starshot planners met at Moffett Field in California to hash out some of the details.

    Lubin suggests that the a laser-accelerated lightsail could reach 0.25c (that is, 25 percent the speed of light). The Breakthrough Starshot announcementsimilarly suggests a target velocity of 0.2c. I’ll again be conservative–within this frame of crazy optimism, that is–and say that what is really possible is closer to 0.05c, or 5 percent the speed of light. That is still roughly 10,000 miles per second, a hugely ambitious goal. At that speed, sending probes to Proxima Centauri b would take approximately 85 years.

    Notice, by the way, that I said probes. To make the Starshot work, you want to start with very small payloads, no larger than an iPhone and possibly a good deal smaller; the lighter the payload, the easier it is to accelerate to ultra-high velocity. A low-mass payload will necessarily have limited capabilities, probably a camera, a couple types of spectrometers, particle & magnetism detectors, and a laser communication system. When that probe reaches its destination, it will still be moving at 10,000 miles per second and will have no way to slow down. Your trip through the most interesting part of the Proxima Centauri system will happen very quickly, in a matter of hours, and you will have no way to steer toward planet b or any other specific targets.

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    Artist’s impression of what Proxima Centauri b might look like. Nobody alive today will ever know if this scene is accurate, but a fast flyby view of the planet just might be possible within a human lifetime. (Credit: ESO/M. Kornmesser)

    But there is a huge upside to the Starshot concept. Almost all of the cost goes into the laser system that launches your probe. The probe itself would be a tiny, solid-state device attached to a thin sail. If the probes were mass produced, the cost per launch might be just a few hundred thousand dollars. The Breakthrough Starshot team therefore envisions launching not one, but a swarm of thousands. Some of those probes would fail at launch; some would fail along the way; some would miss Proxima Centauri, or not pass close enough to interesting targets to get a good look. But it doesn’t matter; a 99 percent failure rate would still be a tremendous success. If you launch 1,000 probes, you need only a dozen to survive in order to achieve one of the most amazing missions of exploration in human history.

    If you tally my numbers, you’ll see that I envision the first probes reaching Proxima Centauri in about 135 years (and then you have to allow another 4.3 years for their signal to get back home). Using much more aggressive assumptions, Lubin suggests that we could get start receiving our first up-close reports on Proxima Centauri b around 2070. Either way it is a very long wait time to make sense of a new discovery, and that assumes both a sustained, focused effort and the successful resolution of a vast number of technical challenges.

    Fortunately, this race passes a lot of milestones that are much closer and easier to reach. Even in its early stages, laser-sail technology would be useful for high-speed exploration through the solar system, or for deflecting and maneuvering asteroids. More to the point, there is a whole other race to Proxima Centauri–one that does not require high-power lasers and interstellar travel, one that is underway right now. I’ll talk more about that in my next post.

    See the full article here .

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  • richardmitnick 4:39 pm on August 30, 2016 Permalink | Reply
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    From GIZMODO: “How We’ll Get Our First Big Clue About Life on Proxima b” 

    GIZMODO bloc

    GIZMODO

    1
    Artist’s concept of Proxima b orbiting Proxima Centauri. (Image: ESO./L. Calçada/Nick Resigner)

    Last week, astronomers announced that our nearest neighboring star hosts an Earth-sized planet in the habitable zone—an exciting prospect for alien life, and a possible second home for humanity. But before we assemble the interstellar welcoming party to greet our cosmic neighbors, we need to figure out whether Proxima b is capable of supporting life at all. Thanks to the James Webb Space Telescope, that question could be answered in less than three years.

    NASA/ESA/CSA Webb Telescope annotated
    NASA/ESA/CSA Webb Telescope annotated

    “It is controversial whether or not life can exist in low mass star systems like Proxima Centauri,” Harvard astronomer Avi Loeb told Gizmodo. “Some people have argued that such planets cannot have an atmosphere.”

    That’s why Loeb, along with Harvard astronomer Laura Kreidberg, has just submitted a paper to Astrophysical Journal Letters describing how we can use the JWST—the highly-anticipated successor to Hubble that launches in 2018—to answer this critical question within just a few days of observation.

    The concern that Proxima b may be a dead, airless world stems from the fact that it orbits its dim red dwarf star, Proxima Centauri, at a distance of just 4.6 million miles. (Earth, for comparison, is 93 million miles from the Sun.) This tight orbit affords Proxima b enough sunlight for Earth-like temperatures and liquid water, but it also subjects the planet to powerful, atmosphere-stripping solar winds. What’s more, it virtually ensures that Proxima b is tidally locked, with a permanent dayside and a permanent nightside. Unfortunately, models suggest that the atmospheres of tidally locked planets may be prone to sudden collapse, as volatile gases freeze out on the nightside.

    But atmospheres can also be replenished through volcanic activity, and on planets with strong magnetic fields, they’re less likely to escape. Since we know nothing of Proxima b’s volcanic activity or magnetic field strength, we can’t even make an educated guess about its prospects of having an atmosphere. But we’re dying to know, because an atmosphere means oceans are possible, and the two together mean life is.

    That’s where the JWST comes in. As Loeb and Kreidberg discuss in their paper, the key to sniffing out Proxima b’s atmosphere lies in the planet’s infrared heat signature. And it just so happens that Hubble’s successor is highly attuned to the infrared part of the spectrum.

    “As Proxima b moves about its star, there is no day-night variation,” Loeb explained. “The day side is hot and the night side is cold. But the temperature difference between day and night depends on whether the planet is bare rock, or if it has an atmosphere or ocean, because these redistribute heat.”

    In other words, the temperature difference between Proxima b’s day side and its night side will be larger if there is no atmosphere. In fact, the day side will re-emit all of the energy it absorbs from Proxima Centauri as a blackbody, and we can calculate exactly how much blackbody radiation there should be. The night side, on the other hand, will be hell frozen over.

    If the temperature difference between day and night is less extreme, we can infer the presence of an atmosphere. Conveniently, it won’t take long for the JWST to measure IR emissions from both faces of Proxima b as it orbits its star—an entire year only takes 11.2 Earth days.

    If Proxima b does have an atmosphere, the next step will be figuring out what it’s made of. We’ll specifically want to look for things like oxygen, water vapor, and methane, which could indicate habitable conditions if not active biological processes. This, however, requires us to catch starlight as it bounces off or filters through the planet’s atmosphere—an extraordinarily difficult thing to do. While the JWST might be able to detect a few compounds including ozone, full atmospheric analysis will have to wait for future ground-based observatories like the Extremely Large Telescope, which is expected to see first light in the mid-2020s.

    “The important thing is that in a couple of years, we should be able to start learning about the atmosphere [of Proxima b],” Loeb said. “If there is one, it’s quite likely there’d be a call for a special mission to study just this planet.”

    As we continue building the tools to study Proxima b from Earth, Loeb is already thinking about how we might pay the planet a visit. He’s chairing the advisory committee for Breakthrough Starshot, a billionaire-backed effort to develop tiny, laser-propelled spacecraft that can travel at up to 20 percent the speed of light. While Breakthrough Starshot was initially packaged as a voyage to the nearby binary star system Alpha Centauri, the discovery of Proxima b changes everything.

    “I think it’s extremely important, psychologically, to have a target,” Loeb said. “If you ask a person to build a ship without knowing where it will sail, it’s quite different than if you have a destination in mind. The fact that we now have a target, in the habitable zone, is very exciting.”

    See the full article here .

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