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      Neptune-sized exoplanet is too big for its host star

      news.movim.eu / ArsTechnica · Friday, 1 December - 17:38

    Artist's conception of a planet embedded in a disk of dust.

    Enlarge (credit: NASA/JPL-Caltech )

    You win some, you lose some. Earlier this week , observations made by the Webb Space Telescope provided new data that supports what we thought we understood about planet formation. On Thursday, word came that astronomers spotted a large planet orbiting close to a tiny star—a star that's too small to have had enough material around it to form a planet that large.

    This doesn't mean that the planet is "impossible." But it does mean that we may not fully understand some aspects of planet formation.

    A big mismatch

    LHS 3154 is, by any reasonable measure, a small, dim star. Imaging by the team behind the new work indicates that the red dwarf has just 11 percent of the Sun's mass. Temperature estimates place it at about 2,850 K, far lower than the Sun's 5,800 K temperature and barely warm enough to keep it out of ultracool dwarf category. (Yes, ultracool dwarfs are enough of a thing to merit their own Wikipedia entry .)

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      Data from NASA’s Webb Telescope backs up ideas on planet formation

      news.movim.eu / ArsTechnica · Tuesday, 28 November - 13:00 · 1 minute

    Image of an orange, circular shape, with a bright object at the center and areas of higher and lower brightness.

    Enlarge / Image of a planet-forming disk, with gaps in between higher-density areas. (credit: ALMA(ESO/NAOJ/NRAO); C. Brogan, B. Saxton )

    Where do planets come from? The entire process can get complicated. Planetary embryos sometimes run into obstacles to growth that leave them as asteroids or naked planetary cores. But at least one question about planetary formation has finally been answered—how they get their water.

    For decades, planetary formation theories kept suggesting that planets receive water from ice-covered fragments of rock that form in the frigid outer reaches of protoplanetary disks, where light and heat from the emerging system’s star lacks the intensity to melt the ice. As friction from the gas and dust of the disk moves these pebbles inward toward the star, they bring water and other ices to planets after crossing the snow line, where things warm up enough that the ice sublimates and releases huge amounts of water vapor. This was all hypothesized until now.

    NASA’s James Webb Telescope has now observed groundbreaking evidence of these ideas as it imaged four young protoplanetary disks.The telescope used its Medium-Resolution Spectrometer (MRS) of Webb’s Mid-Infrared Instrument (MIRI) to gather this data, because it is especially sensitive to water vapor. Webb found that in two of these disks, massive amounts of cold water vapor appeared past the snow line, confirming that ice sublimating from frozen pebbles can indeed deliver water to planets like ours.

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      “Tasmanian Devil” event has the power of hundreds of billions of Suns

      news.movim.eu / ArsTechnica · Monday, 27 November - 16:21 · 1 minute

    Image of a bright blue explosion with purple highlights against a dark background.

    Enlarge (credit: NOIRLab/NSF/AURA/M. Garlick/M. Zamani )

    What is hundreds of billions of times more powerful than the Sun, flashes on repeat with intense bursts of light, and verges on defying the laws of physics? No, it’s not your neighbors’ holiday lights glitching again. It’s an LFBOT in the depths of space.

    LFBOTs (Luminous Fast Blue Optical Transients) are already quite bizarre. They erupt with blue light, radio, X-ray, and optical emissions, making them some of the brightest explosions ever seen in space, as luminous as supernovae. It is no exaggeration that they give off more energy than hundreds of billions of stars like our own. They also tend to live fast, blazing for only minutes before they burn themselves out and fade into darkness.

    LFBOTs are quite rare, and in many cases their sources are unidentified. But we’ve never seen anything with the intensity of an LFBOT named AT2022tsd—aka the “Tasmanian Devil.” Its strange behavior was caught by 15 telescopes and observatories, including the W.M. Keck Observatory and NASA’s Chandra Space Telescope. Like other phenomena of its kind, it initially emitted incredible amounts of energy and then dimmed. Unlike any other LFBOT observed before, however, this one seemed to come back from the dead. It flared again—and again and again.

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      Meet “Amaterasu”: Astronomers detect highest energy cosmic ray since 1991

      news.movim.eu / ArsTechnica · Thursday, 23 November - 19:00 · 1 minute

    Artist’s illustration of extensive air showers induced by ultra-high-energy cosmic rays. Credit: Toshihiro Fujii/L-INSIGHT/Kyoto University

    Astronomers involved with the Telescope Array experiment in Utah's West Desert have detected an ultra-high-energy cosmic ray (UHECR) with a whpping energy level of 244 EeV, according to a new paper published in the journal Science. It's the most energetic cosmic ray detected since 1991, when astronomers detected the so-called "Oh-My-God' particle , with energies of an even more impressive 320 EeV. Astronomers have dubbed this latest event the "Amaterasu" particle, after the Shinto sun goddess said to have created Japan. One might even call it the "Oh-My-Goddess" particle.

    Cosmic rays are highly energetic subatomic particles traveling through space near the speed of light. Technically, a cosmic ray is just an atomic nucleus made up of a proton or a cluster of protons and neutrons. Most originate from the Sun, but others come from objects outside our solar system. When these rays strike the Earth’s atmosphere, they break apart into showers of other particles (both positively and negatively charged).

    They were first discovered in 1912 by Austrian physicist Victor Hess via a series of ascents in a hydrogen balloon to take measurements of radiation in the atmosphere with an electroscope. He found that the rate of ionization was a good three times the rate at sea level, thereby disproving a competing theory that this radiation came from the rocks of  Earth. If you've ever seen a cloud chamber in a science museum, cosmic ray tracks look like wispy little white lines, similar to tiny jet contrails.

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      In the (convection) zone: Astronomers eavesdrop on stars’ innate “twinkle”

      news.movim.eu / ArsTechnica · Tuesday, 22 August, 2023 - 20:46 · 1 minute

    Visualization of "Twinkle, Twinkle, Little Star" played through three sizes of massive stars. Credit: Northwestern University.

    Science 101 tells us that the twinkling appearance of stars from our vantage point on Earth is due to atmospheric effects: winds and varying temperatures and densities in the air bend and distort the light. But stars have another sort of "twinkle" produced by how gases ripple in waves across their surface, an effect that could provide astronomers with a handy means of exploring the interior of massive stars to learn more about how they form and evolve. But the effect is much too small to be readily detected by telescopes.

    So scientists have now developed the first 3D simulations of that innate twinkle, according to a recent paper published in the journal Nature Astronomy. As a bonus, the researchers converted the data from those rippling waves of gas into an audible sound, so now we can all take a moment to listen to "Twinkle, Twinkle, Little Star" (see video above) and Gustav Holst's "Jupiter" (see video below) in the "language" of the stars.

    “Motions in the cores of stars launch waves like those on the ocean,” said co-author Evan Anders of Northwestern University. “When the waves arrive at the star’s surface, they make it twinkle in a way that astronomers may be able to observe. For the first time, we have developed computer models which allow us to determine how much a star should twinkle as a result of these waves. This work allows future space telescopes to probe the central regions where stars forge the elements we depend upon to live and breathe.”

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      An exoplanet is getting vaporized but is trying to hide it

      news.movim.eu / ArsTechnica · Tuesday, 15 August, 2023 - 17:06

    Image of a cloud of blue gas and a planet in front of a small, red star.

    Enlarge / Artist's conception of the atmosphere being blasted off an exoplanet. (credit: NASA, ESA, and Joseph Olmsted (STScI) )

    Some planets cannot hold on to their atmospheres. It's thought that most of whatever atmosphere Mars may have had was annihilated by the solar wind billions of years ago, even as Earth and Venus held on to theirs. But there are planets that orbit so close to their star that atmospheric loss is inevitable. With at least one of them, we’ve learned that it is also unpredictable.

    Exoplanet Au Mic b is that planet. It orbits the young, hot, and temperamental red dwarf star Au Microscopii (Au Mic), which is only 23 million years old—nothing compared to our 4-billion-year-old sun. NASA’s Hubble Space Telescope caught this scorched world losing a portion of its atmosphere.

    When a team of scientists from the NASA Goddard Space Flight Center, Dartmouth College, the University of California at Santa Cruz, and other institutions analyzed the Hubble observations, they were confused by the planet’s erratic behavior. There would be evidence of atmospheric loss in some of the data, then suddenly none at all. It was unpredictable.

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      Rogue planets may be more numerous than stars in our galaxy

      news.movim.eu / ArsTechnica · Tuesday, 8 August, 2023 - 14:35

    Image of a planet against a dark background.

    Enlarge / An artist's conception of an ice-encrusted rogue planet. (credit: NASA’s Goddard Space Flight Center )

    Planets that go rogue orbit no star. They wander the vacuum of space alone, having been kicked out of their star systems by gravitational interactions with other planets and stars. Nobody really knows how many rogue planets could be out there, but that may change in a few years.

    Researchers from NASA’s Goddard Space Flight Center and Osaka University in Japan have used the phenomenon of gravitational microlensing to estimate the number of rogue planets that could be revealed in the heart of the Milky Way. They analyzed data from the Microlensing Observations in Astrophysics (MOA) survey that searched for gravitational microlensing events from 2006 to 2014 to figure out how many more of these events we could expect to find with NASA’s upcoming Nancy Grace Roman Space Telescope.

    There are currently only 70 known rogue planets, but there could be hundreds more out there. The researchers now suggest that Roman could discover at least 400 Earth-mass rogues meandering through our galaxy.

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      Communal stargazing using your phone: The Unistellar eQuinox 2, reviewed

      news.movim.eu / ArsTechnica · Saturday, 29 July, 2023 - 10:30 · 1 minute

    The eQuinox 2 is ready for sundown in central Illinois. No eyepiece here, so have your smartphone handy if you want to stargaze.

    Enlarge / The eQuinox 2 is ready for sundown in central Illinois. No eyepiece here, so have your smartphone handy if you want to stargaze. (credit: Eric Bangeman/Ars Technica)

    When we reviewed the Unistellar eVscope a couple of years ago, we came away impressed. It offered a communal stargazing experience that takes our ubiquitous smartphones and turns them into a way to view the heavens. Unistellar's newest offering is the eQuinox 2, a lower-cost alternative to eVscope 2, taking all of the features from its original telescope, improving the technology, and dropping the price to $2,499.

    Unistellar's smart telescopes are designed to make astronomy more accessible by automating skywatching and using digital sensors to "collect" light from faraway objects, making light pollution a small nuisance instead of a deal-breaker.

    At a glance, the biggest difference between the eQuinox 2 and its predecessor is the former's lack of an eyepiece. Unistellar got rid of the eyepiece, which isn't much of a loss. Instead of taking turns peering through the eyepiece, up to 10 people can stargaze simultaneously with the Unistellar app. Connect to the telescope's built-in Wi-Fi network, launch the app, and you're ready to scan the skies. One person controls the telescope and everyone else can watch. The operator can give control of the telescope to anyone else easily.

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      Rover sampling finds organic molecules in water-altered rocks

      news.movim.eu / ArsTechnica · Wednesday, 12 July, 2023 - 22:18 · 1 minute

    Greyscale image of a large fan of material spread out across a crater floor.

    Enlarge / Jezero crater shows clear signs of water-formed deposits, so it's not a surprise to find water-altered material there. (credit: NASA/MSSS/USGS )

    Organic chemicals, primarily composed of carbon and hydrogen, underly all of life. They're also widespread in the Universe, so they can't be taken as a clear signature of the presence of life. That creates an annoying situation regarding the search for evidence of life on Mars, which clearly has some organic chemicals despite the harsh environment.

    But we don't know whether these are the right kinds of molecules to be indications of life. For the moment, we also lack the ability to tear apart Martian rocks, isolate the molecules, and figure out exactly what they are. In the meantime, our best option is to get some rough information on them and figure out the context of where they're found on Mars. And a big step has been made in that direction with the publication of results from imaging done by the Perseverance rover.

    Ask SHERLOC

    The instrument that's key to the new work has a name that pretty much tells you it was designed to handle this specific question: Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals (SHERLOC). SHERLOC comes with a deep-UV laser to excite molecules into fluorescing, and the wavelengths they fluoresce at can tell us something about the molecules present. It's also got the hardware to do Raman spectroscopy simultaneously.

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