Tagged: Astronomy Magazine Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 11:17 am on November 25, 2022 Permalink | Reply
    Tags: "What the image of the Milky Way’s black hole really shows", , Astronomy Magazine, , , , , Event Horizon Telescope (EHT), , , The massive object at the galaxy’s center is invisible. But this year’s picture of the swirling plasma around its edges will help to reveal more about the galaxy’s history and evolution.   

    From “Astronomy Magazine” : “What the image of the Milky Way’s black hole really shows” 

    From “Astronomy Magazine”

    11.11.22 [Just now in social media.]
    Katie McCormick

    The massive object at the galaxy’s center is invisible. But this year’s picture of the swirling plasma around its edges will help to reveal more about the galaxy’s history and evolution.

    1
    To create the first image of the Milky Way’s black hole, scientists ran numerous simulations of the swirling envelope of plasma that encircles it. This clip shows the version of the animated computer model that seemed to best mirror the radio wave data collected by the Event Horizon Telescope. Credit: Abhishek Joshi/UIUC.
    _________________________________________
    Event Horizon Telescope Array

    The locations of the radio dishes that will be part of the Event Horizon Telescope array. Image credit: Event Horizon Telescope. via University of Arizona.

    About the Event Horizon Telescope (EHT)

    The EHT consortium consists of 13 stakeholder institutes; The Academia Sinica Institute of Astronomy & Astrophysics [中央研究院天文及天文物理研究所](TW) , The University of Arizona, The University of Chicago, The East Asian Observatory, Goethe University Frankfurt [Goethe-Universität](DE), Institut de Radioastronomie Millimétrique, Large Millimeter Telescope, The MPG Institute for Radio Astronomy[MPG Institut für Radioastronomie](DE), MIT Haystack Observatory, The National Astronomical Observatory of Japan[[国立天文台](JP), The Perimeter Institute for Theoretical Physics (CA), Radboud University [Radboud Universiteit](NL) and The Center for Astrophysics | Harvard & Smithsonian.
    _________________________________________

    Black holes keep their secrets close. They imprison forever anything that enters. Light itself can’t escape a black hole’s hungry pull.

    It would seem, then, that a black hole should be invisible — and taking its picture impossible. So great fanfare accompanied the release in 2019 of the first image of a black hole [Messier 87*].

    Then, in spring 2022, astronomers unveiled another black hole photo — this time of the one at the center of our own Milky Way.

    The image shows an orange, donut-shaped blob that looks remarkably similar to the earlier picture of the black hole in the center of galaxy Messier 87. But the Milky Way’s black hole, Sagittarius A*, is actually much smaller than the first and was more difficult to see, since it required peering through the hazy disk of our galaxy. So even though the observations of our own black hole were conducted at the same time as M87’s, it took three additional years to create the picture. Doing so required an international collaboration of hundreds of astronomers, engineers and computer scientists, and the development of sophisticated computer algorithms to piece together the image from the raw data.

    3
    The new image of the black hole Sagittarius A*, confirms and refines previous predictions of its size and orientation. The mass of the black hole determines its size, or what scientists call its gravitational diameter. The point at which no light can escape from the black hole, called the event horizon, is determined by this mass and by the spin of the black hole. Hot plasma speeds around the massive object in the accretion disk, emitting radio waves. Those radio waves are bent and warped by gravity (through the effect of “gravitational lensing”) to produce the image of the orange outer circles. The black hole shadow and emission ring shown here are gravitationally-lensed projections of the far-side of the black hole’s event horizon and accretion disk, respectively.

    These “photos” do not, of course, directly show a black hole, defined as the region of space inside a point-of-no-return barrier known as an event horizon. They actually record portions of the flat pancake of hot plasma swirling around the black hole at high speeds in what’s known as the accretion disk. The plasma is composed of high-energy charged particles. As plasma spirals around the black hole, its accelerating particles emit radio waves. The blurry orange ring seen in the images are an elaborate reconstruction of these radio waves captured by eight telescopes scattered around the Earth, collectively known as the Event Horizon Telescope (EHT).

    The latest image tells the tale of the epic journey of radio waves from the center of the Milky Way, providing unprecedented detail about Sagittarius A*. The image also constitutes “one of the most important visual proofs of General Relativity,” our current best theory of gravity, says Sera Markoff, an astrophysicist at the University of Amsterdam and member of the EHT collaboration.

    Studying supermassive black holes such as Sagittarius A* will help scientists learn more about how galaxies evolve over time and how they congregate in vast clusters across the universe.

    From the galactic core

    Sagittarius A* is 1,600 times smaller than Messier 87* imaged in 2019, and is also about 2,100 times closer to Earth. That means the two black holes appear to be about the same size on the sky. Geoffrey Bower, an EHT project scientist at the Academia Sinica Institute of Astronomy and Astrophysics in Taiwan, says that the resolution required to see Sagittarius A* from Earth is the same as would be required to take a picture of an orange on the surface of the Moon.

    The center of our galaxy is 26,000 light-years away from us, so the radio waves collected to create this image were emitted around the time that one of the earliest-known permanent human settlements was constructed. The radio waves’ voyage began when they were first emitted from particles in the black hole’s accretion disk. With a wavelength of about 1 mm, the radiation traveled toward Earth relatively undisturbed by the intervening galactic gas and dust. If the wavelength were much shorter, like visible light, the radio waves would have been scattered by the dust. If the wavelength were much longer, the waves would have been bent by charged clouds of plasma, distorting the image.

    Finally, after the 26,000-year trek, the radio waves were picked up and recorded at the radio observatories distributed across our planet. The large geographic separation between the observatories was essential — it allowed the consortium of researchers to detect extremely subtle differences in the radio waves collected at each site through a process called interferometry. These small differences are used to deduce the minuscule differences in the distance each radio wave traveled from its source. Using computer algorithms, the scientists managed to decode the path-length differences of the radio waves to reconstruct the shape of the object that emitted them.

    3
    The latest black hole image was created using a technique called interferometry, in which the radio waves emitted by the black hole and collected by eight telescopes located around the world are compared. If two sites collected waves that were “in-phase”, meaning the waves’ peaks lined up with one another, then the two waves would add together to create a bright spot on the image. If, on the other hand, the waves were out-of-phase, meaning one wave’s peak lined up with the other’s trough, the waves would cancel each other, producing a dark spot in the image. Working together, the telescopes are able to collect more detailed data than any one could alone.

    Researchers put all this into a false-color image, where orange represents high-intensity radio waves and black represents low-intensity. “But each telescope only picks up a tiny fraction of the radio signal,” explains Fulvio Melia, an astrophysicist at University of Arizona who has written about our galaxy’s supermassive black hole [Annual Review of Astronomy and Astrophysics (below)] . Because we’re missing much of the signal, “instead of seeing a crystal clear photo, you see something that’s a little foggy … a little blurred.”

    The image helps reveal more about the black hole’s event horizon — the closest point to which anything can approach the black hole without being sucked in. Beyond the event horizon, not even light can escape.

    From the image, scientists have been able to better estimate the size of the event horizon and deduce that the accretion disk is tilted by more than 40 degrees from the Milky Way’s disk, so that we’re seeing the round face of the flat accretion disk, rather than the thin sliver of its edge.

    But even if the black hole’s accretion disk were oriented edge-on relative to Earth, the gravity around the black hole warps the space around it so much that light emitted from the backside of the black hole would be bent around to come toward us, making a ringlike image regardless of its orientation. So, how do scientists know its orientation? Because the ring is mostly round; if we were viewing the accretion disk edge-on, then the ring would be more squished and oblong.

    Markoff thinks that this new ability to look into the heart of our galaxy will help to fill in gaps in our understanding of the evolution of galaxies and the large-scale structure of the universe. A dense, massive object such as a black hole at the center of a galaxy influences the movements of the stars and dust near it, and that influences how the galaxy changes over time. Properties of the black hole, such as in which direction it spins, depend on the history of its collisions — with stars or other black holes, perhaps. “A lot of people … look at the sky and think of it all as static, right? But it’s not. It’s a big ecosystem of stuff that’s evolving,” Markoff says.

    So far, the fact that the image matches the scientists’ expectations so precisely makes it an important confirmation of current theories of physics. “This has been a prediction that we’ve had for two decades,” Bower says, “that we would see a ring of this scale. But, you know, seeing is believing.”

    Science paper:
    Annual Review of Astronomy and Astrophysics
    See the science paper for instructive material with images.

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct.

    Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

    Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

     
  • richardmitnick 8:36 am on November 11, 2022 Permalink | Reply
    Tags: "Ghost particles caught streaming from dust-shrouded black hole", , Astronomy Magazine, , , Blazars are prime candidates for generating neutrinos., , , Messier 77 has a magnetic field that is acting as a powerful particle accelerator., , , Neutrinos are not rare — roughly 100 trillion of them pass through your body every second., Neutrinos barely interact with matter., , The IceCube observatory in Antarctica has captured the best evidence yet that the galactic core of M77 is producing neutrinos.   

    From “Astronomy Magazine” : “Ghost particles caught streaming from dust-shrouded black hole” 

    From “Astronomy Magazine”

    11.7.22
    Mark Zastrow

    The IceCube observatory in Antarctica has captured the best evidence yet that the galactic core of Messier 77 is producing neutrinos.

    __________________________________________________

    U Wisconsin IceCube neutrino observatory

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration.

    Lunar Icecube.

    IceCube Gen-2 DeepCore PINGU annotated.

    IceCube neutrino detector interior.

    IceCube DeepCore annotated.

    DM-Ice II at IceCube annotated.


    __________________________________________________

    2
    The active galaxy Messier 77 as captured by the Hubble Space Telescope. Credit: A. van der Hoeven/The National Aeronautics and Space Agency/ The European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganization](EU).

    The origins of neutrinos are notoriously hard to pin down. The cosmos is flooded by these ghostlike particles, which come from all over the sky. But for years, neutrinos’ elusive nature meant astronomers could point confidently to just one galaxy known to produce them.

    Now, there is strong evidence for a second: the bright spiral Messier 77 (NGC 1068) in Cetus. In a paper published Nov. 3 in Science [below], researchers report fresh observations from the IceCube neutrino observatory at the South Pole, plus improved analysis techniques that draw on machine learning. Combined, the results point to Messier 77 as the origin of 79 neutrinos that IceCube has detected over the past decade.

    That interpretation suggests that the supermassive black hole at the dust-obscured heart of Messier 77 has a magnetic field that is acting as a powerful particle accelerator. But it also hints at answers to a larger astronomical mystery: how neutrinos are produced and how that process relates to other high-energy forms of light and matter that astronomers detect in the sky — cosmic rays and gamma rays.

    In Messier 77, IceCube could be getting a glimpse of the origin of cosmic rays, says Francis Halzen, IceCube’s principal investigator and a particle physicist at the University of Wisconsin-Madison. In any case, Halzen is optimistic that more results will be forthcoming: “I think that we have the tools to solve the oldest problem in astronomy.”

    Elusive particles

    Theory predicts that neutrinos originate in some of the most energetic and violent regions of space: for instance, the cores of galaxies, when cosmic rays run into dust and radiation. The radioactive debris of such collisions eventually decays into neutrinos and gamma rays.

    Observing this, however, is not easy. Neutrinos are not rare — roughly 100 trillion of them pass through your body every second. The difficulty is that unlike light, which is easily reflected or bent by mirrors and lenses, neutrinos barely interact with matter. A neutrino could travel through lead for a light-year before having a 50 percent chance of interacting with an atom.

    In 2017, IceCube played a pivotal role in one of the first examples of a multi-messenger astronomy campaign, when the observatory detected a particularly energetic neutrino coming from a point in Orion. Follow-up observations from ground- and space-based telescopes — including NASA’s Fermi gamma-ray telescope — working across the electromagnetic spectrum showed that the neutrino likely came from a known blazar, TXS 0506+056, that was in the middle of producing a flare of gamma rays.


    Blazars are prime candidates for generating neutrinos: They have central supermassive black holes spitting out jets of material at near-light speed aligned directly at Earth. However, the amount of neutrinos that IceCube has detected from TXS 0506+056 is much less than astronomers would expect if blazars were the sole source for all neutrinos seen across the sky.

    This led astronomers to suspect that other types of galaxy could be producing neutrinos, too — ones whose gamma rays are “hidden,” perhaps obscured. An analysis of IceCube data published in 2020 [Physical Review Letters (below)]tentatively identified one such candidate galaxy: M77 in Cetus, roughly 30 million to 60 million light-years away. It appeared to be the source of dozens of neutrinos, despite the fact that its core lacks the powerful jets seen in blazars. It is “a clear example of such [a] gamma-ray obscured cosmic-ray accelerator,” Khota Murase, an astrophysicst at Penn State University who was not involved in the work, told Astronomy via email.

    3
    This sky map produced from IceCube data depicts neutrino sources by the probability that they are not false positives. The circled spot in the northern hemisphere is Messier 77 — the most probable detection in the northern sky. Credit: IceCube Collaboration.

    But the evidence as of 2020 wasn’t strong enough for the IceCube team to claim Messier 77 as a clear detection; according to the team’s analysis, the statistical significance was 2.9σ, meaning there was roughly a 1-in-500 chance that the build-up of neutrinos from Messier 77’s location could be a random occurrence. It left open the question, “Was this real, or were these fluctuations?” says Halzen. But with the new paper, he says, “we have now answered this question.”

    Improved analysis

    The new analysis includes a bevy of improvements, including machine-learning techniques to improve the accuracy of the neutrino tracks and their energies. The team says it also has a better understanding of the optical properties of the ice and IceCube’s directional sensitivity to neutrinos. These factors push the statistical significance of the find up to 4.2 σ. This is still short of the 5σ threshold that is considered the gold standard in physics, which equates to a probability that the signal could be a random error of just 1 in 3.5 million. Still, it is “great progress,” says Murase, who also penned a commentary for Science [below] accompanying the paper.

    IceCube plans to keep up its momentum. During the South Pole summer season spanning 2025 and 2026, the observatory will be upgraded with more sensors and new calibration devices. The additions will improve the telescope’s sensitivity and also allow for another improved reanalysis of 15 years of data, says Halzen.

    The team has also proposed a next-gen version of IceCube with eight times the volume of the current observatory, which would be capable of confirming sources like Messier 77 at the 5σ level and was endorsed by last year’s astronomy decadal survey.

    Science papers:
    Science
    Physical Review Letters 2020
    See this science paper for detailed material with images if the reader has proper credentials.
    Commentary for Science

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

    Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

     
  • richardmitnick 10:34 am on September 23, 2022 Permalink | Reply
    Tags: "Why does Earth have continents?", Astronomy Magazine, , , ,   

    From “Astronomy Magazine” : “Why does Earth have continents?” 

    From “Astronomy Magazine”

    9.15.22
    Erik Klemetti

    If you were to arrive in our solar system never having seen it before, you’d be impressed with variety. Giant gas planets with rings, moons spanning from minuscule to enormous, icy comets that hurtle in from the edges, rocky planets all with varying amounts of atmospheres. It almost seems like no two planets/moons formed the same way, but one really sticks out as an oddball.

    It’s Earth. Our planet has liquid water (weird!) It has life (even weirder!) It has plate tectonics churning away (continued weirdness!) It even has gigantic masses of rocks unlike anything else in the solar system (totally weird!) Those masses are the continents, made of rocks like granite, sandstone, gneiss, slate, andesite, rhyolite and more.

    The rest of the planets are almost entirely basalt or something close, but Earth. No, earth hides most of its basalt surface under deep oceans, instead letting its freak flag fly with continental rocks showing off to any passersby.

    All of these unique features are connected. Plate tectonics may exist on Earth because we have liquid water at the surface. Life might be a product of the abundant water and volcanism. The composition of the Earth’s continents might be a product of life’s interactions with rock. It is all deep time evolution of minerals, rocks and organism that make Earth what it is.

    What are continents anyway?

    There is still a lot unknown about the formation of our continents. We’re pretty sure that no other planet has the silica-rich continental masses that Earth possesses. Mars might have a little bit of what geologists call “evolved” rocks (in other words, more silica than basalt). Venus could have a little bit as well. The Moon has anorthosite highlands that are a bit like continents except they formed from lighter minerals floating in a primordial magma ocean … that and those highlands are mostly all the same stuff.

    No planet has the complex melange of volcanic rocks, sediment, metamorphic rocks and cooled magma that are Earth’s continents. The current theory, based on the ages of tiny zircon crystals found in Australia, is that our continents may have started forming over 4 billion years ago. However, whether they all formed quickly to close to their current size or have been slowly growing over time is an open question.

    What makes continents so special?

    Well, they are less dense and much thicker than the other flavour of plate on Earth, oceanic plates. Our ocean basins exist mainly because the crust underneath them are denser and thinner basalt plates, meaning they sit lower on the Earth’s ductile mantle (note: the Earth’s mantle is not made of molten magma). The continents, on the other hand, sit high because of their lower density and thicker profile, much like a volleyball sits higher in a pool than a tennis ball (a concept we call isostasy).

    This difference does more than just create the different shapes of Earth’s surface. Continents are so buoyant that they can’t get shoved back into Earth’s mantle like the denser continental crust. Thus is born features like mountain belts formed from continental collision and subduction zones (and their volcanoes) where oceanic crust dives underneath continental crust.

    The continents change as well. With plate tectonics comes the “supercontinent cycle” (also known as the Wilson Cycle) where continents collide to form massive supercontinents like Pangaea and then split apart over hundreds of millions of years. Today, the only thing we have close to a supercontinent is the amalgam of Europe, Asia and India.

    The core of continents

    The oldest parts of our continents are called cratons (and if those rocks are exposed at the surface, they’re called shields.) They represent the nucleus of each major continent, usually much smaller than the continent as a whole. These areas haven’t seen much in the ways of active tectonic processes like collisions or rifts for hundreds of millions to billions of years.

    In North America, the craton stretches from northern Canada and Greenland (where the oldest rocks going back 3-4 billion years) to the south into Texas, but only parts of it are exposed at the surface. Most continents are more than just their cratons, so we know that the continents didn’t form all at once in the early history of the Earth. You can check out a map of the world’s cratons below to get a sense of the old cores of continents.
    One of the biggest questions might be what got the whole continent thing started … and what keeps it going. It didn’t seem to happen at the other rocky planets of our solar system. This means that there are some factors that are likely intrinsic to Earth — our liquid water and molten/solid core — that helped continents develop as fully as they have. However, as they say, that’s not all.

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

    Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

     
  • richardmitnick 2:10 pm on September 16, 2022 Permalink | Reply
    Tags: "How will we recognize life elsewhere in the cosmos?", , Astronomy Magazine, , , , With scientists finding new and bizarre exoplanets each year searching for life as we know it might be too narrow a parameter.   

    From “Astronomy Magazine” : “How will we recognize life elsewhere in the cosmos?” 

    From “Astronomy Magazine”

    9.9.22
    Conor Feehly

    With scientists finding new and bizarre exoplanets each year searching for life as we know it might be too narrow a parameter.

    1
    Astronomers estimate that there are more exoplanets than stars in the Milky Way, but what might alien life look like on these worlds? Credit: NASA/JPL-Caltech.

    In the search for extraterrestrial life, astrobiologists face a bit of a conundrum: How wide of a net should they cast when searching for life elsewhere in the cosmos?

    After all, scientists have been shocked by the extreme environments life manages to thrive in here on Earth. So it isn’t too hard to imagine that the universe might be teeming with the unexpected. However, with human interplanetary travel still more science fiction than reality, researchers are limited by the technology and knowledge of life currently accessible. But that doesn’t mean they can’t get creative.

    Identifying candidates for life

    In astrobiology, a popular technique for determining whether an exoplanet might support extraterrestrial life involves analyzing the atmosphere of the planet via the transit method.

    When a distant star passes behind its exoplanet from the point of view of Earth, starlight filters through the atmosphere of the exoplanet before making its way to our instruments. Using a spectrograph, astronomers can separate that filtered starlight into its constituent components. Analyzing this resulting emission spectra can provide astronomers with a detailed log of the chemistry likely present in the atmosphere of the alien world.

    Astrobiologists who investigate the atmospheres of exoplanets this way are looking for what they call biosignatures, or chemical evidence for past or present life. Since we know that certain biological processes on Earth leave chemical traces in our atmosphere, if we manage to identify those same traces in the atmospheres of other planets, then we would have good reason to believe living organisms inhabit or inhabited those other worlds.

    Currently, the transit method has been mostly used to analyze giant, hot planets that orbit very near their host stars. That’s because they are much easier to spot and confirm, as these so-called “hot Jupiters” block more starlight more frequently than smaller, more distantly orbiting worlds.

    2
    Researchers detected the basic chemistry for life in the hot gas planet HD 209458b. Credit: T. Pyle (SSC)/NASA/JPL-Caltech.

    But hot Jupiters are unlikely to be habitable locales for life — at least life as we know it. To fully realize the potential of the transit method in detecting possible life-supporting planets, astronomers must seek improvements in our technology for detecting and isolating the emission spectra of exoplanets.

    Fortunately, NASA’s proposed FINESSE mission, the European Space Agency’s proposed Exoplanet Spectroscopy Mission, and the recently launched Webb will provide scientists with a look at many new potential homes for extraterrestrial life, as well as provide them with a vastly improved ability to analyze the emission spectra of exoplanets.

    There are, however, certain problems with the biosignature method of detecting life on alien worlds.

    The problem with assumptions

    Some astrobiologists argue that we should be open to the possibility that extraterrestrial organisms could be very different to life as we know it. One of the most basic signs that an entity is an organism on Earth, that it produces carbon dioxide or water as a product of respiration or photosynthesis, may not apply as the universal indicator of life elsewhere in the cosmos.

    3
    The super-Earth HD 219134b is a mere 21 light-years from our solar system. Credit: NASA/JPL-Caltech.

    Even our understanding of biosignatures on Earth is still murky, as discoveries in exotic metabolic processes can attest. It is an ongoing debate as to how astrobiologists might distinguish between the chemical compositions of alien atmospheres that indicate the presence of life and those that don’t since we cannot assume that extraterrestrial life will produce the same biosignatures of living organisms on Earth.

    So, if the parameters set out for identifying life in the cosmos is currently too narrow, how can we search for extraterrestrial life if we don’t necessarily know what we are looking for?

    According to Princeton philosopher David Kinney and Search for Extraterrestrial Intelligence (SETI) principal investigator Christopher Kempes, we should be looking at planets with the strangest atmospheres.

    Strange bedfellows

    Planets with peculiar atmospheres, relative to a representative sample, should be regarded as the most likely settings for extraterrestrial life. The parameters for ‘anomalousness’ should be data-dependent, rather than being based on assumptions about life that may be Earth-centric.

    “Conceptually, there must be some common thread between all things in the universe that we want to describe as being alive,” says Kinney, who co-authored the paper, published June 22 in Biology & Philosophy [below], outlining their theory.

    In moving away from the assumption that the thread must be chemical, Kinney and Kempes hope to avoid some common pitfalls, namely abiotic processes that mimic biotic ones. “There has been a long history in exoplanet research of people finding abiotic mechanisms that produce candidate biosignature gases,” says Kinney. “Our method circumvents this issue a bit by saying ‘let the data tell us what is anomalous.’”

    Still their argument does rest on a few core assumptions. First that a given sample of exoplanets can be statistically representative of all the atmospheres in the universe. While over 5,000 exoplanet candidates have been confirmed, scientists estimate that there are hundreds of billions of planets within the Milky Way alone. It also assumes that life in that set of observable exoplanets is rare and that living organisms tend to leave biosignatures in the planets they inhabit.

    Although each of these assumptions can be questioned, it follows that if the chemical composition of a planet is unusual, then a possible cause of this unusual composition is that life exists on that planet. The foundation of their method comes from a paper published in Astrobiology [below] in 2016 in which a list of roughly 14,000 compounds likely to appear as gasses in the atmospheres of extrasolar planets’ is outlined.

    “A key takeaway from our paper is that when science is conducted under conditions of deep uncertainty, a scientist often must be willing to speculate,” says Kemples. “That is, they must be ready to make assumptions that go beyond their data, and to then explore the consequences of those assumptions. Whatever one discovers very likely won’t verify those initial assumptions, but this method can nevertheless lead to extraordinary breakthroughs.”

    Science papers:
    Biology & Philosophy
    Astrobiology

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

    Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

     
  • richardmitnick 1:34 pm on September 16, 2022 Permalink | Reply
    Tags: "Webb photographs universe’s most distant known star", Astronomy Magazine, , , , It was the Hubble Space Telescope which actually discovered this ancient object., , Webb has photographed a star that began shining just 900 million years after the Big Bang.   

    From “Astronomy Magazine” : “Webb photographs universe’s most distant known star” 

    From “Astronomy Magazine”

    9.7.22

    1
    The James Webb Space Telescope captured the most distant known star, Earendel, in this deep field shot released Aug. 2, 2022. Credit: NASA/ESA/CSA/STScI

    One of the great challenges for astronomers is to understand when the first stars formed and what they were like. They already have some clues.

    First, hydrogen and helium formed about 380,000 years after the Big Bang. The first stars were made of this. And second, the oldest galaxies formed about 400 million years after the Big Bang.

    Meet the ancient star Earendel

    So the first stars must have formed at some point in between. The best estimate is that the earliest stars began to shine perhaps 100 million years or so after the Big Bang. But the truth is that nobody really knows because these stars have never been observed. Until this year, the oldest observed star formed about 4.4 billion years after the Big Bang. That’s considerably later than this first period of star formation.

    Now the James Webb Space Telescope has photographed a star that began shining just 900 million years after the Big Bang. The images improve on those taken earlier this year by the Hubble Space Telescope which actually discovered this ancient object, and provide astronomers with their first glimpse of a star from this early period of the universe.

    2
    Earendel’s host galaxy, the Sunrise Arc, is smeared across the sky by gravitational lensing.

    Astronomers call this ancient star “Earendel”, a word derived from Old English meaning “rising light”. It began burning some 13 billion years ago but, because of the expansion of the universe, now sits about 28 billion light years from Earth, making it the most distant star ever observed.

    “Earendel” is only observable because of an extraordinary cosmic coincidence. As seen from the Earth, it sits behind a vast cluster of galaxies called WHL0137-08 with a gravitational field that focuses its starlight towards Earth, magnifying it up to 40,000 times.

    This gravitational lensing effect makes “Earendel’s” host galaxy appear as a smear of light across the distant universe — astronomers have named it the Sunrise Arc. The arc contains bright knots of light along its length and one of these knots is “Earendel”.

    Webb’s images improve on Hubble’s and narrow down the potential size of the star. The star appears as a point source of light suggesting it cannot be greater than 4000 astronomical units across. “These new observations strengthen the conclusion that “Earendel” is best explained by an individual star or multiple star system,” say Brian Welch at Johns Hopkins University in Baltimore and colleagues who have analyzed the images.

    The team say that the photometry suggests “Earendel” has a surface temperature of between 13000 and 16000 Kelvin. This in turn suggests the star is a giant hydrogen-burning B-type star with a mass somewhere between 20 and 200 times that of the sun.

    Is “Earendel” a binary star?

    However, the team also say that “Earendel” could be a binary system and that various combinations of stars could better fit the observed data. Indeed, the best fit is a combination of a luminous cool star and a hot companion.

    For the moment, the data does not allow the team to solve this problem. However, Webb is due to observe “Earendel” again later this year when more data could help to constrain the nature of this star or star system. It will also provide astronomers with more data about one the universe’s earliest stars.

    That is interesting work that shows off the extraordinary light gathering power of the Webb and its older relative Hubble, and how this instrument is already changing the way we see the universe.

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

    Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

     
  • richardmitnick 9:05 am on August 19, 2022 Permalink | Reply
    Tags: "The star that changed the cosmos:: M31-V1", Astronomy Magazine, , Cepheids are pulsating stars whose brightness varies over timescales ranging from one to more than 120 days., Harlow Shapley measured the size of the Milky Way in 1915 and found it far larger than most astronomers had imagined., Hubble used M31-V1 a Cepheid variable star to show Messier 31 lies far outside the Milky Way proving it had to be another galaxy., In 1912 Henrietta Swan Leavitt discovered a linear relationship between the logarithm of the periods of Cepheid variables and their apparent magnitudes., In 1923 Edwin Hubble using the 100-inch Hooker Telescope and photographic glass plates at Mount Wilson Observatory discovered a variable star within Messier 31., In 1929 Hubble published an estimated distance to Messier 31 of 900000 light-years. The currently accepted distance to Messier 31 is 2537000 light-years., On April 26 1920 Harlow Shapley-Mount Wilson Observatory and Heber Curtis-Lick Observatory held a Debate at the Smithsonian. The nature of spiral nebulae; scale of the universe., , Prior to the work of Edwin Hubble astronomers referred to Messier 31 and scores of other galaxies scattered throughout the sky as spiral nebulae., Shapley argued the Milky Way was the entire universe and the spiral nebulae were smaller objects within it., The same errors that caused Shapley to overestimate the diameter of the Milky Way caused Hubble to underestimate the distance to Messier 31.   

    From “Astronomy Magazine” : “The star that changed the cosmos:: M31-V1” 

    From “Astronomy Magazine”

    8.9.22
    Rod Pommier

    1
    This colorful image shows a closeup of a portion of the Andromeda Galaxy’s (Messier 31) disk. The Cepheid variable star M31-V1 is indicated with an arrow [?]. The shot is a composite of luminance data acquired on many of the 57 nights over which the author imaged, to which color data have subsequently been added. Credit: Rod Pommier.

    “You know that Messier 31 (NGC 224) in Andromeda is another galaxy far outside our own Milky Way, don’t you?

    Of course you do! Everyone knows that.

    But we haven’t always known it. In fact, we’ve only known for just under a century. Prior to that, astronomers referred to Messier 31 and scores of other galaxies scattered throughout the sky as spiral nebulae. They were visible in great numbers in a bewildering variety of sizes, shapes, and orientations. But no one knew their distance. And their true nature was a hotly debated issue.

    On April 26, 1920, astronomers Harlow Shapley of Mount Wilson Observatory and Heber Curtis of Lick Observatory held a Great Debate at the Smithsonian Institution in Washington, D.C. The topic: the nature of spiral nebulae and the scale of the universe.

    Shapley had measured the size of the Milky Way in 1915 and found it far larger than most astronomers had imagined. He argued the Milky Way was the entire universe and the spiral nebulae were smaller objects within it. Perhaps they were swirling stellar nurseries or condensing solar systems. Curtis argued they were galaxies, each like the Milky Way, and therefore extremely large and at vast distances. The debate had no clear winner.

    Just a few years later, in 1923, Edwin Hubble settled it. Using the 100-inch Hooker Telescope and photographic glass plates at Mount Wilson Observatory, he discovered a variable star within Messier 31.

    Hubble used that star to show Messier 31 lies far outside the Milky Way, proving it had to be another galaxy. The universe suddenly got much bigger. In fact, if the myriad spiral nebulae that appeared smaller than Messier 31 were also galaxies in their own right, they must be farther still. The universe had to be unbelievably enormous.

    Hubble’s star, the first variable found in Messier 31, has since been dubbed M31-V1. It is the star that changed the cosmos.

    Emulating Hubble

    As an avid astrophotographer, I wanted to take my own image of this tar. But could I? I don’t have a 100-inch telescope. I have a 14-inch telescope, which is magnitudes smaller. On the other hand, I do have a cooled CCD camera, which is much more sensitive to light than the photographic glass plates Hubble used. Could my smaller telescope with a more responsive detector possibly match a larger scope with less sensitive plates when looking at this faint target?

    With some research, I found that 11 members of The American Association of Variable Star Observers (AAVSO) had successfully imaged M31-V1 in 2010 at the request of the Space Telescope Science Institute. Researchers wanted to know when the star was brightest to best image it with the Hubble Space Telescope (HST) for a public outreach program. The AAVSO report indicated they found M31-V1 a challenging but achievable target for modern CCD cameras and “larger” telescopes. How large was not reported. Still, their success convinced me I could at least attempt to image M31-V1 for myself.

    Then a bigger question hit me. While imaging M31-V1, could I also use my images to prove Messier 31 is another galaxy? That would be a fantastic project. After all, we are approaching the centennial of Hubble’s discovery of M31-V1. What better time to emulate his work? To do that, I would not only need to duplicate Hubble’s astrophotography; I would also need to understand how he used his images of M31-V1 to prove M31’s distance.

    1
    Delta (δ) Cephei is the prototype Cepheid variable. This light curve shows its apparent magnitude versus time. All Cepheids produce a characteristic sawtooth pattern, with a rapid increase in brightness followed by a slow dimming. The timescale over which this pattern repeats is the period, and the difference between maximum and minimum brightness is the amplitude. Delta Cephei’s period is 5.4 days and its amplitude is 0.7 magnitude. Credit: Roen Kelly/ Astronomy, after R Nave/Hyperphysics.

    A standard candle

    Hubble determined the distance to Messier 31 by finding a so-called standard candle within it. A standard candle is an object of known luminosity, or intrinsic brightness. If you know an object’s luminosity, you can compare that to how bright it appears from your vantage point and work out how far away it must be. The standard candle Hubble found in Messier 31, the star M31-V1, is a Cepheid variable star.

    Cepheids are pulsating stars whose brightness varies over timescales ranging from one to more than 120 days. They exhibit a distinctive pattern on a graph of brightness versus time, called a light curve, consisting of a sharp increase in brightness followed by a gradual dimming. This pattern repeats at regular intervals, known as the period.

    2
    Henrietta Swan Leavitt discovered a linear relationship between the logarithm of the periods of Cepheid variables, plotted on the x-axis, and their apparent magnitudes, plotted on the y-axis. This relationship was derived from 25 Cepheids in the Small Magellanic Cloud. The upper tracing and best-fit line show the stars’ maximum magnitudes; the bottom tracing and best-fit line, their minimum magnitudes. Leavitt suggested the relationship could best be expressed using the stars’ period and average apparent magnitude. This is now known as the period-luminosity relationship, or the Leavitt law. Credit: Roen Kelly/Astronomy after Leavitt & Pickering, 1912.

    She noted that the longer a Cepheid variable’s period, the brighter it appeared. In 1912, she published a graph showing a strong positive linear correlation between the logarithm of these stars’ periods and average apparent magnitudes. This is now known as the period-luminosity relationship, or the Leavitt law.

    Danish astronomer Ejnar Hertzsprung realized the tremendous significance of Leavitt’s discovery. Once calibrated, this relationship would allow astronomers to calculate the distance to any Cepheid from two pieces of data: its period and its average apparent magnitude. But Hertzsprung’s early attempts at calibration were crude at best, yielding a distance to the Small Magellanic Cloud of 30,000 light-years, compared to the currently accepted value of 200,000.

    Shapley revised the calibration but his work was also incorrect, leading him to estimate our galaxy’s diameter was 300,000 light-years instead of the currently accepted 100,000. His measurements did correctly show we were at the outskirts of the Milky Way, rather than its center — the biggest demotion of our place in the universe since Copernicus put the Sun at the center of the solar system.

    However, a much bigger demotion was to come.

    3
    This graph shows the period-luminosity relationship, calibrated by measuring the distances to Cepheid variables in the Milky Way. These distances can be used to calculate the stars’ true luminosities, or absolute magnitudes, to calibrate the y-axis of the graph. Calibration enables use of any Cepheid variable as a standard candle, whose distance can be determined from only its period and average apparent magnitude. In this case, an example Cepheid with a period of 4.76 days yields an absolute magnitude of –3.57. Credit: Roen Kelly/Astronomy, after Australia Telescope National Facility.

    How Hubble did it

    In September 1923, Hubble began taking serial exposures of Messier 31 from Mount Wilson. On the night of Oct. 5/6, he made a 45-minute exposure on plate H335H. (The first H stands for Hooker, the last for Hubble.) Upon examination, he marked three stars in black with the letter N for novae, because they appeared to be new compared to earlier plates. However, he subsequently noticed that one of those three was present on earlier plates, including H331H taken the previous night. In fact, it appeared on archival plates as far back as 1909, but fluctuated in brightness. So, it couldn’t be a nova and must be a variable star.

    With a red pen, Hubble crossed out the letter N and wrote “VAR!” for variable. Why the exclamation point? Hubble realized that if this star was a Cepheid, he had struck astronomical gold. If he could determine the Cepheid’s period and its average apparent magnitude, then he could calculate the distance to Messier 31 and solve the mystery of the spiral nebulae.

    In early 1924, Hubble imaged this star on as many successive nights as weather permitted and determined its nightly magnitude. His data produced the characteristic light curve of a Cepheid. He measured its period as 31.415 days and estimated its median apparent magnitude at 18.5. From the period, Hubble derived an absolute magnitude of –5.0. He then calculated that for a Cepheid this bright to exhibit an apparent magnitude of 18.5, it had to be nearly 1 million light-years away. Therefore, Messier 31 could only be an enormous independent galaxy outside the Milky Way.

    In 1929 Hubble published an estimated distance to Messier 31 of 900000 light-years, calculated using additional observations and Shapley’s revised calibration of the period-luminosity relationship. The currently accepted distance to Messier 31 is 2537000 light-years. The same errors that caused Shapley to overestimate the diameter of the Milky Way caused Hubble to underestimate the distance to Messier 31.

    4
    Hubble’s glass photographic plate H335H, obtained with the 100-inch Hooker Telescope Oct. 5/6, 1923, shows the galaxy Messier 31. Three “new” stars are marked in black with the letter N. However, Hubble later noted that the star at the top right was present on earlier plates but fluctuated in brightness. He subsequently crossed out the N and marked it with “VAR!” in red. This is the Cepheid variable M31-V1, which Hubble used to calculate the distance to Messier 31 and solve the mystery of the spiral nebulae. Courtesy of Carnegie Institution for Science.

    Planning the project

    To reproduce Hubble’s work, I needed to produce a light curve to determine both M31-V1’s period and average apparent magnitude. Measuring magnitudes of stars on digital images is now done with photometry software, which determines the magnitude of a target star by comparing its brightness to that of a comparison star of known magnitude on the same image. My imaging software, MaxIm DL Pro, includes a tool to do this.

    The AAVSO website’s Star Plotter, which allows users to create star charts at various scales and orientations to match their images, includes comparison stars and their magnitudes. Fortunately for me, the AAVSO established many comparison stars within 15′ of M31-V1 in preparation for their 2010 project.

    Research indicated that to obtain the most accurate magnitude measurements, I should bin my images to 1×1. Further, my telescope is a Schmidt-Cassegrain, which is subject to mirror flop — a shift in mirror position with actions such as focusing or parking the telescope. Mirror flop can significantly change the illumination of a CCD chip between imaging sessions, affecting magnitude readings. Therefore, I committed to shooting new flat field calibration frames each night.

    I imaged through a clear filter to capture as many photons as possible and used an f/7.5 focal reducer/corrector to reduce exposure time. M31 spans the width of six Full Moons across the sky, so only a portion of it would fit within my scope’s field of view. Therefore, my first tasks were to determine M31-V1’s location within M31 and how best to frame it on my CCD chip.

    M31-V1 is at R.A. 00h41m27.3s, Dec. 41°10’10.4″, in the northeast quadrant of Messier 31. Using imaging-planning software, I determined turning my CCD camera to a rotation angle of 135° and aiming at R.A. 00h41.1m, Dec. 41°11′ placed M31-V1 near the center of my chip. This orientation would also include the magnitude 9.27 foreground Milky Way star SAO 36590 as a suitable guide star in my off-axis guider, allowing for accurate tracking during imaging sessions. Several AAVSO comparison stars were present on my images.

    Hubble didn’t know how many nights he would have to image M3-V1 to determine its period, but with the benefit of his work, I knew it would require at least a month and likely longer. A Cepheid’s period is most reliably measured between dates of maximum brightness. I didn’t know where M31-V1 would be in its cycle during my first observation. Therefore, I’d likely have to continue imaging until it peaked in brightness and carried out another full cycle until it peaked again. That meant I’d have to image some nights with a nearly Full Moon, which unfortunately would be in the vicinity of Messier 31 during upcoming months. Bright moonlight flooding down my telescope tube might completely wash out M31-V1, especially if the Full phase coincided with the dim portion of the star’s cycle.

    Then, there was weather. Hubble worked in sunny southern California, where he had only a few cloudy nights. I live in rainy Portland, Oregon, where even clear nights are often interrupted by clouds rolling in. There was also a risk of heavy smoke obscuring the sky for long periods during the upcoming wildfire season. This would indeed be a challenge.

    Imaging the star

    I began imaging in early August, a time when Messier 31 rises above 45° altitude by 1 A.M. I calibrated and stacked the first night’s sub-exposures into a single integrated image. Then I zoomed in on the region containing Hubble’s Cepheid for inspection. M31-V1 appeared as a small, faint dot right where it was supposed to be! I stopped and stared at that star for a long time. During my 35 years as an astrophotographer, I have captured and inspected countless stars in my shots. This star was as inconspicuous and seemingly insignificant as any I had ever seen. Yet no other star I have imaged has been more important to cosmology and our understanding of our place in the universe than this small, dim one. Seeing the star that changed the universe on an image I had made myself took my breath away.

    Spurred on by my initial success, I eagerly returned to my backyard observatory every clear night. I couldn’t wait to see if and when M31-V1 changed in brightness. As the Moon waxed toward Full, the star grew dim and I was concerned it might soon disappear from my images. My fears were allayed as it suddenly brightened, quickly reaching a peak. I continued imaging for weeks afterward, as it slowly faded again. As the Moon once again approached Full, the star quickly brightened, reaching a second peak. I observed every clear night for another couple of weeks as it faded for a third time. At that point, having imaged over a period of 57 nights, I knew I had collected data for more than one full period.

    With my imaging completed, I calibrated and stacked all the sub-exposures from each night into an integrated image for that date. I was ready to make my own light curve of M31-V1.

    5
    Incorporating data from observations made over 57 nights, the author’s light curve exhibits the characteristic pattern of a Cepheid variable. From this light curve, the author obtained the star’s period of 31.91 days, peak apparent magnitude of 18.6, minimum apparent magnitude of 19.8, average apparent magnitude of 19.2, and amplitude of 1.2 magnitudes.
    Credit: Roen Kelly/Astronomy,after Rod Pommier.

    Making light curves

    I calibrated my photometry software on a comparison star near the center of each image. This worked extremely well — my magnitude readings on all other comparison stars read accurately to within a few hundredths of a magnitude. That gave me confidence my recorded magnitudes for M31-V1 were also accurate. Although my software displays magnitude readings to three decimal places, I could only justify reading M31-V1’s brightness to the nearest 0.1 magnitude because the magnitudes of comparison stars in my chart were given only to one decimal place.

    After measuring M31-V1’s magnitude on all my images, I plotted these by date on a graph. The resulting light curve definitely exhibited the characteristic pattern of a Cepheid. I could now derive the period and apparent magnitude to calculate the distance to Messier 31.

    The apparent magnitudes for the first and second maxima were 18.6 and both minima were 19.8. Therefore, the amplitude of my light curve was 1.2 magnitudes and the average apparent magnitude was 19.2. The difference in Julian dates for the maxima yielded a period of 31.91 days. Although this is not the period of 31.415 days derived by Hubble, the small difference had no appreciable impact on my calculated absolute magnitude. This is because the period-luminosity relationship uses the logarithm of the period to obtain absolute magnitude. The logarithms of 31.91 and 31.415 both round to 1.5.

    6
    This calibrated and stacked image — greatly zoomed in — from the author’s first night of observation shows M31-V1, as a faint dot, right where expected. Credit: Rod Pommier.

    The distance to Messier 31

    To compare my results for the distance to Messier 31 directly to Hubble’s, I needed to use Shapley’s flawed calibration of the period-luminosity relationship. Curiously, Hubble adjusted this graph to yield absolute magnitude at maximum, rather than the average absolute magnitude as originally suggested by Leavitt and used in virtually all other calibrations. Hubble indicated he believed his maximum magnitude readings were more reliable than those obtained during dimmer portions of the cycle. Based on this graph, the logarithm of my 31.91-day period yielded an absolute magnitude for M31-V1’s maximum of –3.6.

    Once you have an object’s absolute magnitude and corresponding apparent magnitude, it is simple to calculate its distance using an equation called the distance modulus: m – M = 5[log10(d/10)], where m is the apparent magnitude, M is the absolute magnitude, and d is the distance in parsecs. (One parsec is equal to 3.26 light-years.) Solving this equation for d gives d = 10(m-M+5)/5.

    My values for m and M yielded a distance of 275,423 parsecs, or 897,879 light-years — very close to Hubble’s published value of 900,000. With this, I had accomplished my goal. Despite the flawed calibration, I had also proven Messier 31 is so far away it must be a separate galaxy.

    I was extremely pleased that my result was so close to Hubble’s. The difference was only 2,121 light-years. Then, while reading Hubble’s 1929 publication again, I noticed something remarkable. Although Hubble did not show his values for maximum apparent and absolute magnitude, he gave their difference: m – M = 22.2. That was precisely the value I had obtained! That could only mean Hubble had obtained exactly the same distance: 897,879 light-years. He simply rounded to 900,000 light-years in his paper. Now I was thrilled. I had done in my backyard what Hubble did at Mount Wilson, with precisely the same result.

    Still, that result is incorrect because it is based on an incorrect calibration of the period-luminosity relationship. Since 1929, as technology has improved, the calibration has been revised. This has greatly increased the calculated distance to Messier 31. With the advent of HST, that number is now 2.537 million light-years.

    A memorable endeavor

    With that, I declared the project a great success. Following in Hubble’s footsteps was an exhilarating experience I will certainly remember for the rest of my life. Most of all, I am amazed that I, a mere amateur astronomer using equipment in my backyard, was able to reproduce a feat that less than a century ago was accomplished by the world’s greatest astronomer using the world’s largest telescope.

    This is a testament to amateur astronomy as a hobby. Want to be an amateur archaeologist or paleontologist? Good luck accessing an Egyptian tomb or a T. rex fossil bed to conduct your own research projects. Such valuable materials are reserved exclusively for professionals.

    Not so with amateur astronomy. All astronomers have unrestricted access to the same crucial resource: the entire sky above us. And with that, the sky is truly the limit of what we amateurs can do.”

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

    Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

     
  • richardmitnick 7:12 am on August 19, 2022 Permalink | Reply
    Tags: "Unique liquid-mirror telescope comes online in India", Astronomy Magazine, , , , , The Devasthal Observatory in Uttarakhand (IN)   

    From “Astronomy Magazine” : “Unique liquid-mirror telescope comes online in India” 

    From “Astronomy Magazine”


    At 8,040 feet above sea level (2,450 meters) in Uttarakhand, India, lies a prime site for astronomical observations — Devasthal, 31 (52 kilometers) miles east of the resort town Nainital. Surrounded by the scenic beauty of the lofty Himalayas, Devasthal Observatory already hosts two research-grade optical telescopes.

    Now, a novel instrument has joined the race to unravel cosmic mysteries — the International Liquid Mirror Telescope (ILMT), which uses a rotating pan of liquid mercury as its primary mirror, not a solid sheet of polished glass.

    ILMT is the first telescope of its kind for India, the largest in Asia, and made solely for astronomical surveys. Although the idea of a liquid mirror is not new, no modern instrument has ever been constructed in a location as suited for astronomy as Devasthal.

    “The site has a very dark sky and a good number of clear nights,” says Paul Hickson, an astronomer at the University of British Columbia (UBC) in Vancouver who has worked on other liquid mirror telescopes and visited Devasthal on multiple occasions.

    An old idea

    Liquid mirrors have a long but mixed record in astronomy. Over 300 years ago, Isaac Newton noted that a liquid in a rotating container would take on the shape of a parabola — precisely the shape needed by a telescope mirror to focus light to a single point. In 1850, Italian astronomer Ernesto Capocci further conceptualized this idea, but couldn’t build a working model.

    During the rest of that decade, London-born astronomer Henry Skey investigated the concept independently and experimented with building one. He emigrated to New Zealand in 1860 and published an account of a working liquid-mirror telescope in 1872 [Papers Past (below)].

    In the early 20th century, Robert Wood, a physicist at Johns Hopkins University, played a pivotal role by constructing LMTs of different sizes to observe astronomical objects passing over the zenith (the point in the sky directly overhead). But despite his best attempts, the technology was still not precise and plagued by vibrations.

    Eventually, LMTs took a back seat as solid-mirror technology advanced. Then, in the 1980s, scientists began to resurrect the technology, addressing its limitations with modern technology. From 1994 to 2002, NASA operated a 3-meter LMT to scan Earth’s orbit for space debris. Later, UBC reused some parts to construct the 6-meter Large Zenith Telescope — the largest of its kind.

    However, the weather at its site was not ideal for astronomy and it was decommissioned in 2016.

    Today, the concept may be poised for a mainstream resurgence. “In 1997, a consortium of astronomers interested in the 4-meter-wide ILMT was formed. But construction took almost 25 years due to liquid requirements and other delays,” says Jean Surdej, ILMT’s project director. India, Belgium, Canada, Poland and Uzbekistan did the work of telescope construction.

    A mercurial mirror

    ILMT uses shiny mercury in liquid form to collect and focus light. Mercury has strong reflective power and stays in a liquid form at room temperature. And it’s much cheaper than highly prized glass mirrors. Grinding mirrors into a parabolic shape is an arduous and expensive task. The total cost of ILMT comes in at $2 million, while a conventional solid-mirror telescope of its size could reach hundreds of millions.

    “One problem is that mercury is hazardous to humans, so proper care needs to be taken,” says Kuntal Misra, Project Investigator of ILMT at the Aryabhatta Research Institute of Observational Sciences (ARIES), which operates Devasthal Observatory and is located in Nainital.

    13.2 gallons (50 liters) of liquid weighing 1,540 pounds (700 kg) have been used to create a 0.14-inch-thick (3.5 millimeters) layer in a bowl that slowly spins every eight seconds via motors. As a result, the liquid takes a parabolic shape under the influence of gravity and centrifugal force — that’s what Newton stated.

    The liquid surface must be smooth and rotate at a constant speed, as any distortions could lead to warped images. To avoid deformities, the mercury is protected on both sides. On top, a thin mylar sheet protects the liquid from wind; from the bottom, it sits on an air bearing system — a 10-micron-thick cushion of compressed air (human hair is 70 microns). It is so delicate that even smoke particles can harm its performance.

    Observing the zenith

    Because the shape of a liquid-mirror telescope depends on gravity, it can only point straight up at the zenith of the sky. However, this is not as much of a disadvantage as it might appear, as the zenith slews across the night sky with Earth’s rotation. “Over the year, the telescope can observe nearly 120 square degrees of sky — 600 times the area of the Full Moon. This area corresponds to about 1 percent of the entire sky and is large enough to contain thousands of interesting objects,” explains Hickson, an astronomer at the University of British Columbia (UBC).

    Those objects could range from supernovae explosions, luminous quasars, elusive stars, and gravitational lenses to solar system objects like asteroids, comets and even space debris.

    Observing the same patch of sky also has its advantages, especially in detecting transient objects. Scientists can look for changes by subtracting images taken on different nights.

    “ILMT will generate a huge 10–15 GB of data nightly. So, advanced computational tools, artificial intelligence, and machine learning will be implemented to classify space objects,” Kuntal adds.

    When it does discover objects, the steerable 3.6-meter Devasthal Optical Telescope next door will be able to take a quick follow-up observation.

    1
    The barred spiral galaxy NGC 4274 (upper right) features in this commissioning image from the ILMT. Credit: India Ministry of Science & Technology.

    The future of liquid mirrors

    LMTs could play an expanded role as the current era of space exploration picks up. With their lightweight and simple design, astronauts could easily deploy one on the Moon, where there is no atmosphere to get in the way of observations.

    Researchers at the University of Texas in Austin have even proposed installing a Ultimately Large Telescope with a 100-meter liquid mirror on the Moon [The University of Texas-Austin (below)].

    2
    The University of Texas-Austin astronomers advocate that rather than have a 20-meter liquid mirror (shown), the size be increased to 100 meters so that the telescope can study the first stars that formed in the universe. Credit: Roger Angel et al./Univ. of Arizona.

    Like to the James Webb Space Telescope, such a telescope could observe infrared light to peer straight into the early years of the universe. But a ULT would have vastly more light-gathering power than JWST, and be capable of directly observing the first stars ever created in the universe composed of primordial gas, known as Population III stars.

    There’s a catch: The extreme lunar conditions would freeze liquid mercury. However, ionic liquids [Nature (below)] would stay in liquid form at frigid temperatures and could be coated with silver for a reflective surface.

    NASA has already been explore the possibilities of constructing liquid mirrors in space with a project called the Fluidic Telescope Experiment (FLUTE) [NASA].

    2
    Fluidic Telescope Experiment (FLUTE). NASA.

    For it, the crew of the private Axiom-1 mission to the International Space Station conducted several experiments on how liquids take shape in microgravity.

    3
    Axiom-1 Credit: NASASpaceFlight.com

    Meanwhile, ILMT has already seen first light and will kick off science observations in October, after monsoon season. “We feel very confident that ILMT will deliver interesting data in the future,” says Surdej.

    Science paper and article:
    Papers Past
    The University of Texas-Austin
    Nature
    NASA

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

    Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

     
  • richardmitnick 1:58 pm on August 5, 2022 Permalink | Reply
    Tags: "Rare Earth hypothesis:: Why we might really be alone in the universe", , Astronomy Magazine, , , , Peter Ward and Donald Brownlee explain to "Astronomy" why they think the development of complex life on other worlds is likely extraordinarily rare.   

    From “Astronomy Magazine” : ” ‘Rare Earth hypothesis’ :: Why we might really be alone in the universe” 

    From “Astronomy Magazine”

    7.29.22
    Doug Adler

    The Rare Earth hypothesis

    In 2000, two researchers, Peter Ward and Donald Brownlee, published a book that offered a possible explanation for our species’ apparent aloneness. It is called Rare Earth: Why Complex Life is Uncommon in the Universe (Copernicus Books, 2000). Ward, a paleontologist by training, and Brownlee, an astronomer, combined forces to produce what has come to be termed the Rare Earth hypothesis.

    Simply stated, the Rare Earth hypothesis suggests that the very unique conditions of Earth that allowed complex life to arise and flourish are exceptionally uncommon — and they’re unlikely to widely occur throughout the universe.

    Ward and Brownlee postulated that many fortuitous features of Earth, our Sun, and the solar system led to our highly favorable and surprisingly stable ecosystem. While some of these properties had been widely discussed in astronomy circles before, others had scarcely been mentioned.

    2
    According to the Rare Earth hypothesis, without massive gas giants like Jupiter and Saturn, Earth and the rest of the inner solar system would be unceasingly bombarded by potentially devastating debris. (Illustration not to scale.)
    Credit: NASA.

    Peter Ward and Donald Brownlee, explain to Astronomy why they think the development of complex life on other worlds is likely extraordinarily rare.

    1
    The “Rare Earth hypothesis” argues that a confluence of very specific environmental factors is responsible for Earth’s ability to support complex life. These same factors are very unlikely to be so finely tuned for worlds elsewhere in the universe. Credit: NASA/Reto Stöckli, based on data from NASA and NOAA.

    The first spacecraft to explore the space beyond Earth orbit was Pioneer 4 in 1959.

    3
    Pioneer 4. Credit: NASA.

    Twenty-five years later, in 1984, astronomers Carl Sagan and Jill Tarter founded the Search for Extraterrestrial Intelligence (SETI), a program that has been scouring the cosmos for signs of alien life ever since.

    SETI Institute

    About The SETI Institute

    The SETI Institute is a 501 (c)(3) nonprofit scientific research institute headquartered in Mountain View, California. We are a key research contractor to National Aeronautics and Space Agency and the National Science Foundation (NSF), and we collaborate with industry partners throughout Silicon Valley and beyond.

    SETI/Allen Telescope Array situated at the Hat Creek Radio Observatory, 290 miles (470 km) northeast of San Francisco, California, USA, Altitude 986 m (3,235 ft), the origins of the Institute’s search.

    The NIROSETI instrument saw first light on the Nickel 1-meter Telescope at Lick Observatory on March 15, 2015. (Photo by Laurie Hatch.)

    Alumna Shelley Wright, now an assistant professor of physics at University of California- San Diego, discusses the dichroic filter of the NIROSETI instrument, developed at the U Toronto Dunlap Institute for Astronomy and Astrophysics (CA) and brought to UCSD and installed at the University of California-Santa Cruz Lick Observatory Nickel Telescope (Photo by Laurie Hatch).


    Shelley Wright of UC San Diego with NIROSETI, developed at U Toronto Dunlap Institute for Astronomy and Astrophysics (CA) at the 1-meter Nickel Telescope at Lick Observatory at UC Santa Cruz


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

    Laser SETI


    LaserSETI observatory installation at Haleakala Observatory in Maui, Hawai’i aimed East.

    There is also an installation at Robert Ferguson Observatory, Sonoma, CA aimed West for full coverage [no image available].

    Also in the hunt, but not a part of the SETI Institute
    SETI@home, a BOINC [Berkeley Open Infrastructure for Network Computing] project originated in the Space Science Lab at UC Berkeley.

    BOINC is a leader in the field(s) of Distributed Computing, Grid Computing and Citizen Cyberscience. BOINC is more properly the Berkeley Open Infrastructure for Network Computing, developed at UC Berzerkeley.

    Founded in 1984, the SETI Institute employs more than 130 scientists, educators, and administrative staff. Work at the SETI Institute is anchored by three centers: the Carl Sagan Center for the Study of Life in the Universe (research), the Center for Education and the Center for Outreach.

    The SETI Institute welcomes philanthropic support from individuals, private foundations, corporations and other groups to support our education and outreach initiatives, as well as unfunded scientific research and fieldwork.

    A Special Thank You to SETI Institute Partners and Collaborators
    Campoalto, Chile, NASA Ames Research Center, NASA Headquarters, National Science Foundation, Aerojet Rocketdyne,SRI International

    Frontier Development Lab Partners
    Breakthrough Prize Foundation, The European Space Agency [La Agencia Espacial Europea] [Agence spatiale européenne][Europäische Weltraumorganisation](EU), Google Cloud, IBM, Intel, KBRwyle. Kx Lockheed Martin, NASA Ames Research Center, Nvidia, SpaceResources Luxembourg, XPrize
    In-kind Service Providers
    • Gunderson Dettmer – General legal services, Hello Pilgrim – Website Design and Development Steptoe & Johnson – IP legal services, Danielle Futselaar

    But, to date, neither an international armada of robotic spacefarers nor alien-seeking scientists have found any evidence of extraterrestrial life. Indeed, while our exploration of the solar system has been nothing short of staggering in terms of the images and scientific data obtained, the worlds we’ve visited beyond Earth all appear to be completely sterile.

    Even the most dedicated SETI researcher would have to admit that, at least so far, our efforts to find life elsewhere in the universe have been met with an uncomfortable stony silence. But why?

    The Rare Earth hypothesis focuses on numerous aspects of Earth and its environment that played a role in allowing complex life to develop. Some of the key factors Ward and Brownlee felt were critical to the formation of complex life included:

    A planet that exists in a favorable part of the right kind of galaxy, where significant amounts of heavy elements are available and sterilizing radiation sources are located far away.

    An orbit around a star that has a long lifetime (billions of years) but does not give off too much ultraviolet radiation.

    An orbital distance that allows liquid water to exist at or near the planet’s surface.

    An orbital distance that is far enough away to prevent the planet from becoming tidally locked to its host star.

    An orbit that is stable around its host star over cosmic timescales.

    A planetary tilt that allows for seasonal atmospheric changes to be mild, not severe.

    A solar system that includes gas giants capable of preventing debris from polluting the inner solar system, reducing the odds of major cosmic impacts and subsequent mass extinctions.

    A planetary mass large enough to both retain an atmosphere and allow for liquid oceans.

    A moon large enough to help stabilize the tilt of the planet’s axis.

    A molten planetary core that generates a significant global magnetic field, largely protecting the surface from solar radiation.

    The presence of oxygen, and the right amount of oxygen, at the right time for complex life to utilize it.

    The presence of plate tectonics, which build up land masses, create diverse ecosystems, cycle carbon into and out of the atmosphere, prevent a runaway greenhouse effect, and help stabilize the surface temperature worldwide.

    Could we really be alone?

    In the two decades since this book was published, interest in these ideas has only grown. Last year, Astronomy caught up with both Ward and Brownlee to discuss the Rare Earth hypothesis. During those conversations, Ward recounted how the whole concept of the Rare Earth hypothesis spawned from a movie-based chat with Brownlee.

    “We were just talking about how ridiculous the Star Wars bar room scene was,” said Ward. “That’s how it all started. Look at all those aliens! You know, I just think [the notion of aliens everywhere] has been foisted on the public.”

    Ward and Brownlee challenged many widely held notions that supported the idea that complex life is out there waiting to be found. For example, while astronomer Carl Sagan often opined that our Sun is an unremarkable star, in reality, about 80 to 95 percent of stars are significantly different from our own in terms of size, mass, luminosity, lifespan, and many other factors.

    Furthermore, prior researchers who had attempted to answer the question of why life on Earth was so plentiful yet so rare in the universe had not included plate tectonics in their thinking at all. Indeed, an entire chapter in Rare Earth is devoted to the topic, going to great lengths to explain the role of plate tectonics in shaping Earth into a good place for life. Earth is, to the best of our knowledge, the only body in the solar system with active plate tectonics. And there are many other features of our life-friendly planet that we haven’t seen replicated anywhere else in the universe, too.

    3
    The Moon’s elusive far side comes into focus in this image captured by the DISCOVR spacecraft. Earth’s large natural satellite not only produces ocean tides, but also helps stabilize Earth’s tilt. Credit: NASA/NOAA.

    Does simple life count?

    It’s important to remember that the Rare Earth hypothesis only applies to the emergence of complex life. Ward and Brownlee believe that simple life, such as bacteria, is widespread in the universe — after all, even the harshest habitats on Earth harbor microbes. However, the pair feel that complex life, metazoans like animals and us, are exceptionally rare.

    “If you find life elsewhere, it’s likely to be microbial,” said Brownlee. “You know, Earth will have a lifetime of about 12 billion years, but [compared to bacteria], metazoans have a much more restricted range of environmental criteria that they can survive in.” That means that a planet’s environment is conducive to simple life for much longer than it is conducive to complex life.

    “The period of time when we have oxygen in the atmosphere — carbon dioxide to go to plants and oxygen for metazoans — is probably only like 10 or 20 percent of [Earth’s lifespan]. So, if you just landed on our planet randomly throughout its entire history, you would not have anything to see.”

    Counter-evidence welcome

    Just because Ward and Brownlee don’t believe complex life is common throughout the universe, that doesn’t mean they don’t want it found. The duo welcome new data from cutting-edge observatories, like the James Webb Space Telescope (JWST), which seek to reveal the atmospheres of exoplanets in detail.
    ________________________________________
    The NASA/ESA/CSA James Webb Space Telescope


    ________________________________________

    And there are certain atmospheric signatures that would be more revealing than others.

    “I think is way more important to try to look for oxygen atmospheres, but also look for reflections that indicate chlorophyll. You’re only going to have a number of ways to build specific molecules,” said Ward. “It really does come back to the fact that, as [University of Washington planetary scientist] David Catling has said, any animal equivalent is going to have to need oxygen — a lot of it. You cannot have really rapidly moving creatures and rapidly thinking creatures, which is a form of movement, and not have oxygen in the atmosphere to do it. You’re not going to have people living on carbon dioxide out there,” he added.

    While compelling, the Rare Earth hypothesis still has its detractors; many of the environmental factors Ward and Brownlee identified in their book have come under fire over the past 20 years. Among the most frequently attacked proposed conditions for complex life is that a large planet like Jupiter is required to keep the inner solar system relatively free of dangerous debris. Some researchers argue such planets could actually increase the frequency of planetary impacts. Other critics have taken issues with the proposed requirements of a global magnetic field and plate tectonics.

    With regard to these criticisms, Ward is understanding, encouraging challenges to his ideas. “Good science does a couple of things,” he says,”but the most important thing it does is it stimulates other science; good science makes people angry. It makes some people angry enough that they go out and do something about it.”

    The Rare Earth hypothesis remains unproven, but it is hard to ignore the plethora of data that Ward and Brownlee have compiled to support their case. The barren and stark surfaces of Mercury, Venus, and Mars all serve as nearby reminders of what a lucky paradise Earth is by comparison. And rare or not, it’s the only home we have.

    And there are certain atmospheric signatures that would be more revealing than others.

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

    Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

     
  • richardmitnick 9:05 am on July 22, 2022 Permalink | Reply
    Tags: "How artificial intelligence is changing Astronomy", Artificial intelligence is a term used to describe any kind of computational behavior that mimics the way humans think and perform tasks., , Astronomy Magazine, , Machine learning has become an essential piece of astronomers’ toolkits., Machine Learning is a family of technologies that learn to make predictions and decisions based on vast quantities of historical data.   

    From “Astronomy Magazine” : “How artificial intelligence is changing Astronomy” 

    From “Astronomy Magazine”

    July 15, 2022
    Ashley Spindler

    Machine learning has become an essential piece of astronomers’ toolkits.

    1
    Breakthrough Listen

    When most people picture an astronomer, they think of a lone person sitting on top of a mountain, peering into a massive telescope. Of course, that image is out of date: Digital cameras have long since done away with the need to actually look though a telescope.

    But now the face of astronomy is changing again. With the advent of more powerful computers and sky surveys that generate unimaginable quantities of data, artificial intelligence is the go-to tool for the keen researcher of space. But where is all of this data coming from? And how can computers help us learn about the universe?

    AI’s appetite for data

    Chances are you’ve heard the terms “artificial intelligence” and “machine learning” thrown around recently, and while they are often used together, they actually refer to different things. Artificial intelligence (AI) is a term used to describe any kind of computational behavior that mimics the way humans think and perform tasks. Machine learning (ML) is a little more specific: It’s a family of technologies that learn to make predictions and decisions based on vast quantities of historical data. Crucially, ML creates models which exhibit behavior that is not pre-programmed, but learned from the data used to train it.

    The facial recognition in your smartphone, the spam filter in your emails, and the ability of digital assistants like Siri or Alexa to understand speech are all examples of machine learning being used in the real world. Many of these technologies are now being used by astronomers to investigate the mysteries of space and time. Astronomy and machine learning are a match made in the heavens, because if there’s one thing astronomers have too much of — and ML models can’t get enough of — it’s data.

    We’re all familiar with megabytes (MB), gigabytes (GB), and terabytes (TB), but data at that scale is old news in astronomy. These days, we’re interested in petabytes (PB). A petabyte is about one thousand TB, a million GB, or a billion MB. It would take around 10 PB of storage to hold every single feature-length movie ever made in 4K resolution — and it would take over a hundred years to watch them all.

    The Vera C. Rubin Observatory, a new telescope under construction in Chile, will be tasked with mapping the entire night sky in unprecedented detail, every single night. Over a 10-year survey, Vera Rubin will produce about 60 PB of raw data — studying everything from asteroids in our solar system, to galaxies in the distant universe. No human being could ever hope to analyze all that data — and that’s from just one of the next-generation observatories being built, so the race is on among astronomers in every field to find new ways to leverage the power of AI.

    Planet hunters

    One area of astronomy where AI has made a significant impact is in the search for exoplanets. There are many ways to look for their signals, but the most productive methods with current technology usually involve studying the variation of a star’s brightness over time. If a star’s light curve shows a characteristic dimming, it could be a sure sign of a planet transiting in front of the host star.

    Conversely, a phenomenon called gravitational microlensing can cause a large spike in a star’s brightness, when the exoplanet’s gravity acts as a lens and magnifies a more distant star along the line of sight.

    Detecting these dips and spikes means sifting through millions of light curves, studiously collected by space telescopes like NASA’s Kepler and TESS (Transiting Exoplanet Survey Satellite).

    Using the huge libraries of observed light curves, astronomers have been able to develop ML-based models that can outperform humans in the search for exoplanets. But AI can do much more than just find exoplanets: It can also lead astronomers to new insights into how those techniques work.

    In a paper published May 23 in Nature Astronomy [below], a team of researchers reported that ML algorithms had helped them discover a more elegant understanding of exoplanet microlensing, unifying multiple interpretations of how the exoplanet’s configuration with its host star might vary. The report came just months after researchers at DeepMind reported in Nature new AI-aided fundamental insights into mathematics [below].

    3
    An exoplanet that microlenses a background star creates a spike in brightness, which can be detected by humans or algorithms. However, because microlensing offers relatively little information about the lensing exoplanet itself, the data leave open many possibilities for the planet’s configuration with its host star — i.e. its mass and how closely it orbits its host star. Previously, astronomers had identified multiple ways in which different configurations of star and planet could produce the same microlensing signal. But machine learning helped researchers from the University of California in Berkeley and Ohio State University realize that, in fact, two of these types of ambiguity — called degeneracies — can be thought of as specific cases of another, more general degeneracy. The find effectively created a more unified theory of exoplanet microlensing. “This discovery was hiding in plain sight,” wrote co-author Joshua Bloom of UC Berkeley in a blog post. Credit: L. Calçada/ESO.

    Astronomers also hope that in the near future, machine learning will help them identify which planets might be habitable. Using next-generation observatories like the Nancy Grace Roman Telescope and James Webb Space Telescope, astronomers intend to use ML to detect water, ice, and snow on rocky planets.

    Galactic forgeries

    While many ML models are trained to distinguish between different types of data, others are intended to produce new data. These generative models are a subset of AI techniques that create artificial data products, such as images, based on some underlying understanding of the data used to train it.

    The series of DALL-E models developed by the research company OpenAI — and the free-to-use imitator it inspired, DALL-E mini — have pushed this concept into the public eye. These models generate an image from any written prompt and have set the internet alight with their uncanny ability to construct images of, for instance, Garfield inserted into episodes of Seinfeld.

    You might think that astronomers would be wary of any kind of fake imagery, but in recent years, researchers have turned to generative models in order to create galactic forgeries. A paper published Jan. 28 in Monthly Notices of the Royal Astronomical Society [below] describes using the method to produce incredibly detailed images of fake galaxies, which can be used to test predictions from enormous simulations of the universe. They can also help develop and refine the data processing pipelines for next-generation surveys.

    Some of these algorithms are so good that even professional astronomers can struggle to distinguish between the real and the fake. Take this recent entry into NASA’s Astronomy Picture of the Day webpage, which features dozens of synthetically generated images of objects in the night sky — and just one real image.

    Searching for serendipity

    AI is also primed to make discoveries that we cannot predict. There’s a long history of discoveries in astronomy that happened because someone was in the right place, at the right time. Uranus was discovered by chance when William Herschel was scanning the night sky for faint stars, Vesto Slipher measured the speed of spiral arms in what he thought were protoplanetary disks — eventually leading to the discovery of the expanding universe — and Jocelyn Bell Burnell’s famous detection of pulsars happened while she was analyzing measurements of quasars.

    Perhaps soon, an AI could join these ranks of serendipitous discoverers though a field of techniques called anomaly detection. These algorithms are specifically trained to sift through mountains of images, light curves, and spectra, looking for the samples that don’t look like anything we’ve seen before. In the next generation of astronomy, with its petabytes of raw data from observatories like the Rubin and JWST, we can’t possibly imagine what these algorithms might find.

    Science papers:

    Nature Astronomy

    Nature

    Nature

    MNRAS

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

    Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

     
  • richardmitnick 11:01 am on July 8, 2022 Permalink | Reply
    Tags: "Seismology": The study of quakes and seismic waves, "What can earthquakes and marsquakes teach us about planets?", A fraction of that energy is converted into waves that travel away from the epicenter of the event., , Astronomy Magazine, , During an earthquake (or marsquake) four main types of waves are generated: p-waves; s-waves; Love waves and Rayleigh waves., , , , Mars Observation, , Seismic waves are by-products of geologic events. They are the result of energy being released when a planet experiences movement of faults; magma flows; impacts from space; massive landslides; more., , The way seismic waves travel through a planetary world can reveal a lot about its internal composition.   

    From “Astronomy Magazine” : “What can earthquakes and marsquakes teach us about planets?” 

    From “Astronomy Magazine”

    June 29, 2022
    Erik Klemetti

    The way seismic waves travel through a planetary world can reveal a lot about its internal composition. Here are the basics.

    1
    NASA/JPL-Caltech

    Understanding what’s inside of a planet is like trying to figure out what’s inside of a gift without unwrapping it. But because we can’t simply tear open a planet, instead, we must rely on secondary evidence, like the waves generated by geologic events.

    Seismology — the study of quakes and seismic waves — lets us take “images” of the interiors of planets. NASA’s Viking landers brought the first seismometers to Mars in 1976, but they were plagued by noise, which rendered them largely ineffective.

    It took more than 40 years until Mars hosted another mission equipped with a quake-measuring instrument: NASA’s InSight lander.

    And although InSight is expected to retire later this year, ever since the lander touched down in 2018, this stationary surveyor has been studying marsquakes, slowly unveiling the interior of the Red Planet.

    What’s shaking?

    Seismic waves are the by-products of geologic events. They are the result of energy being released when a planet experiences the movement of faults, rising magma flows, impacts from space, massive landslides, and more. Much of that energy is spent grinding, melting, and/or moving rocks, but a fraction of it is converted into waves that travel away from the epicenter of the event.

    Scientists use seismometers to measure exactly how the ground moves in response to these passing seismic waves, monitoring any movement in up to three primary directions. On Earth, seismometers are most useful for determining the location, magnitude, and depth of an earthquake. On Mars, however, the main goal of these devices is to provide a window into the inner structure of the planet itself.

    Seismic waves, however, are not all the same. During an earthquake (or marsquake) four main types of waves are generated: p-waves; s-waves; Love waves and Rayleigh waves.

    2
    P-waves and s-waves make up a group called body waves, which travel through rock. The fastest are p-waves (primary, or compression waves), which squeeze rocks as they race through them. The movement of these waves is akin to someone in the back of a line shoving the person in front of them. As p-waves pass through different materials, they speed up and slow down, and that changes their path. So, by mapping how these p-waves change direction, scientists can attempt to piece together a planet’s internal layering and composition.

    The other type of body wave is called an s-wave (secondary, or shear wave), and these are the second fastest type of seismic wave. S-waves move rock perpendicular to the direction the wave is moving, like shaking a beach towel to fling off sand. In order to propagate, S-waves require material that has some internal strength and rigidity. This means that s-waves can’t pass through liquids, including our planet’s liquid metallic outer core.

    The last two seismic waves make up a group called surface waves. On Earth, these are the waves that cause the most devastation. The first type, Love waves, oscillate the surface from side to side (horizontally). Meanwhile, the other type, Rayleigh waves, move through the surface like an ocean wave (vertically). When we feel the ground shaking during an earthquake, Love waves and Rayleigh waves are usually what we’re feeling.

    Inside looking out

    Inside Earth, p- and s-waves speed up as you get deeper into the planet’s crust and mantle. There are some variations as the waves transition from the brittle crust to the malleable mantle to the dense core, but in general, they travel faster at greater depth. This is due to the changing pressure (and thus density) of Earth’s interior, as well as changes in the minerals that make up the mantle.

    When the seismic waves hit Earth’s mantle-core boundary, big things happen. First, the s-waves disappear because the outer core of Earth is liquid. Remember, s-waves shear rocks, and with nothing to shear, they vanish. However, the s-waves return in the planet’s solid inner core. That’s because s-waves, or secondary waves, are mostly a byproduct of the movement of p-waves, or primary waves.

    Meanwhile, p-wave velocities drop dramatically at the mantle-core boundary. That’s because they are going from silica-rich rocks to an iron-nickel core. In fact, inside Earth, p-waves drop in velocity by almost 50 percent. However, p-waves again speed up as they travel deeper into Earth’s outer and inner core.

    After both s- and p-waves make their way through Earth’s core, their speeds change again — but this time in reverse, as they are now venturing from core out to crust.

    In the shadows

    Planets and moons are spheres. So, whether an earthquake, marsquake, or moonquake, a quake will send seismic waves that move in an arc-like shape through the world’s interior (see the image below). When these waves hit different materials, they increase or decrease in speed, causing their paths to bend. This phenomenon is known as refraction, and it’s the same thing that happens when light (which can be a wave) passes through a lens.

    3

    A seismometer positioned on a planet that experiences a quake will detect the arrival of p- and s-waves, allowing scientists to calculate the waves’ average velocities. And if there are multiple seismometers scattered around the world, the waves will arrive at some stations but not others, depending on how much the seismic waves were refracted along the way. This can lead to what are called “shadow zones.”

    To understand how various waves travel through a world, planetary geologists input the arrival times (wave velocities), as well as the location and size of the shadow zones (wave phases), into models. Based on deviations between what the model predicts and what was observed, scientists then further tweak and refine their model to determine the best set of parameters that replicates the seismic data.

    In other words, by unraveling the multitude of seismic waves produced during a quake, scientists can estimate the compositions and dimensions of a world’s various layers.

    InSight’s insights into Mars

    Over the past several years, the seismic data collected by NASA’s InSight lander has revealed that Mars is still a geologically active world. However, both the rate and intensity of geological activity on Mars pales in comparison to what we experience on Earth. So far, in about four years, InSight has detected only one magnitude-5 marsquake. For comparison, our planet experiences hundreds of magnitude-5 earthquakes every month.

    Despite a lack of many powerful marsquakes, InSight has detected hundreds of smaller quakes, which are still valuable for refining models of Mars’ interior. So far, we know the martian crust is thin, going down to a depth of only some 12 to 23 miles (20 to 37 kilometers). Mars’ mantle then stretches down another roughly 970 miles (1,560 km). And the martian core appears to be fully liquid, rather than the dichotomous liquid-solid core that Earth has.

    3
    This view of Cerberus Fossae, created using stereo data collected by ESA’s Mars Express spacecraft, shows fault cracks cutting across the Red Planet.

    Recent data released from NASA’s InSight lander shows this region is still active today.
    Credit: ESA/DLR/FU Berlin.

    The InSight mission has helped scientists peel back the layers of Mars’ interior, providing planetary scientists with years of data that could answer questions about Mars’ lack of both plate tectonics and a strong magnetic field. And that’s just the start. Future missions capable of collecting seismic data may soon venture to other planets and moons beyond Mars, allowing scientists to peer into the hearts of some of the solar system’s most intriguing objects.

    See the full article here .


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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Astronomy is a magazine about the science and hobby of Astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

    Astronomy was founded in 1973 by Stephen A. Walther, a graduate of The University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at The University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However, he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: