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  • richardmitnick 10:20 am on June 9, 2019 Permalink | Reply
    Tags: "Einstein's Quest to 'Know God's Thoughts' Could Take Millennia" Don Lincoln of FNAL, , , , , space.com   

    From SPACE.com: “Einstein’s Quest to ‘Know God’s Thoughts’ Could Take Millennia” Don Lincoln of FNAL 

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    From SPACE.com


    (Image: © Shutterstock)

    In 1925, Einstein went on a walk with a young student named Esther Salaman. As they wandered, he shared his core guiding intellectual principle: “I want to know how God created this world. I’m not interested in this or that phenomenon, in the spectrum of this or that element. I want to know His thoughts; the rest are just details.”

    The phrase “God’s thoughts” is a delightfully apt metaphor for the ultimate goal of modern physics, which is to develop a perfect understanding of the laws of nature — what physicists call “a theory of everything,” or TOE. Ideally, a TOE would answer all questions, leaving nothing unanswered. Why is the sky blue? Covered. Why does gravity exist? That’s covered, too. Stated in a more scientific way, a TOE would ideally explain all phenomena with a single theory, a single building block and a single force. In my opinion, finding a TOE could take hundreds, or even thousands, of years. To understand why, let’s take stock.

    We know of two theories that, when taken together, give a good description of the world around us, but both are light-years from being a TOE.

    The first is Einstein’s theory of general relativity, which describes gravity and the behavior of stars, galaxies and the universe on the largest scales. Einstein described gravity as the literal bending of space and time. This idea has been validated many times, most notably with the discovery of gravitational waves in 2016.

    The second theory is called the Standard Model, which describes the subatomic world. It is in this domain that scientists have made the most obvious progress toward a theory of everything.

    Standard Model of Particle Physics

    If we look at the world around us — the world of stars and galaxies, poodles and pizza, we can ask why things have the properties they do. We know everything is made up of atoms, and those atoms are made up of protons, neutrons and electrons.

    And, in the 1960s, researchers discovered that the protons and neutrons were made of even smaller particles called quarks and the electron was a member of the class of particles called leptons.

    Finding the smallest building blocks is only the first step in devising a theory of everything. The next step is understanding the forces that govern how the building blocks interact. Scientists know of four fundamental forces, three of which — electromagnetism, and the strong and weak nuclear forces — are understood at the subatomic level. Electromagnetism holds atoms together and is responsible for chemistry. The strong force holds together the nucleus of atoms and keeps quarks inside protons and neutrons. The weak force is responsible for some types of nuclear decay.

    Each of the known subatomic forces has an associated particle or particles that carry that force: The gluon carries the strong force, the photon governs electromagnetism, and the W and Z bosons control the weak force. There is also a ghostly energy field, called the Higgs field, that permeates the universe and gives mass to quarks, leptons and some of the force-carrying particles. Taken together, these building blocks and forces make up the Standard Model.

    A theory of everything will explain all known phenomena. We aren’t there yet, but we have unified the behavior of the quantum world in the standard model (yellow) and we understand gravity (pink). In the future, we imagine a series of additional unifications (green). However, the problem is that there are phenomena we don’t understand (blue) that need to fit in somewhere. And we are not certain that we won’t find other phenomena as we go to higher energy (red circles). (Image: © Don Lincoln)

    Using quarks and leptons and the known force-carrying particles, one can build atoms, molecules, people, planets and, indeed, all of the known matter of the universe. This is undoubtedly a tremendous achievement and a good approximation of a theory of everything.

    And yet it really isn’t. The goal is to find a single building block and a single force that could explain the matter and motion of the universe. The Standard Model has 12 particles (six quarks and six leptons) and four forces (electromagnetism, gravity, and the strong and weak nuclear forces). Furthermore, there is no known quantum theory of gravity (meaning our current definition covers just gravity involving things larger than, for example, common dust), so gravity isn’t even part of the Standard Model at all. So, physicists continue to look for an even more fundamental and underlying theory. To do that they need to reduce the number of both building blocks and forces.

    Finding a smaller building block will be difficult, because that requires a more powerful particle accelerator than humans have ever built. The time horizon for a new accelerator facility coming on line is several decades and that facility will provide only a relatively modest incremental improvement over existing capabilities. So, scientists must instead speculate on what a smaller building block might look like. A popular idea is called superstring theory, which postulates that the smallest building block isn’t a particle, but rather a small and vibrating “string.” In the same way a cello string can play more than one note, the different patterns of vibrations are the different quarks and leptons. In this way, a single type of string could be the ultimate building block.

    The problem is that there is no empirical evidence that superstrings actually exist. Further, the expected energy required to see them is called the Planck energy, which is a quadrillion (10 raised to the 15th power) times higher than we can currently generate. The very large Planck energy is intimately connected to what’s known as the Planck length, an unfathomably tiny length beyond which quantum effects become so large that it is literally impossible to measure anything smaller. Meanwhile, go smaller than the Planck length (or bigger than the Planck energy), and the quantum effects of gravity between photons, or light particles, become important and relativity no longer works. That makes it likely this is the scale at which quantum gravity will be understood. This is, of course, all very speculative, but it reflects our current best prediction. And, if true, superstrings will have to remain speculative for the foreseeable future.

    The plethora of forces is also a problem. Scientists hope to “unify” the forces, showing that they are just different manifestations of a single force. (Sir Isaac Newton did just that when he showed the force that made things fall on Earth and the force that governed the motion of the heavens were one and the same; James Clerk Maxwell showed that electricity and magnetism were really different behaviors of a unified force called electromagnetism.)

    In the 1960s, scientists were able to show that the weak nuclear force and electromagnetism were actually two different facets of a combined force called the electroweak force. Now, researchers hope that the electroweak force and the strong force can be unified into what is called a grand unified force. Then, they hope that the grand unified force can be unified with gravity to make a theory of everything.

    Historically, scientists have shown how seemingly unrelated phenomena originate from a single underlying force. We imagine that this process will continue, resulting in a theory of everything. (Image: © Don Lincoln)

    However, physicists suspect this final unification would also take place at the Planck energy, again because this is the energy and size at which quantum effects can no longer be ignored in relativity theory. And, as we’ve seen, this is a much higher energy than we can hope to achieve inside a particle accelerator any time soon. To give a sense of the chasm between current theories and a theory of everything, if we represented the energies of particles we can detect as the width of a cell membrane, the Planck energy is the size of Earth. While it is conceivable that someone with a thorough understanding of cell membranes might predict other structures within a cell — things like DNA and mitochondria — it is inconceivable that they could accurately predict the Earth. How likely is it that they could predict volcanoes, oceans or Earth’s magnetic field?

    The simple fact is that with such a large gap between currently achievable energy in particle accelerators and the Planck energy, correctly devising a theory of everything seems improbable.

    That doesn’t mean physicists should all retire and take up landscape painting — there is still meaningful work to be done. We still need to understand unexplained phenomena such as dark matter and dark energy, which make up 95% of the known universe, and use that understanding to create a newer, more comprehensive theory of physics. This newer theory will not be a TOE, but will be incrementally better than the current theoretical framework. We will have to repeat that process over and over again.

    Disappointed? So am I. After all, I’ve devoted my life to trying to uncover some of the secrets of the cosmos, but perhaps some perspective is in order. The first unification of forces was accomplished in the 1670s with Newton’s theory of universal gravity. The second was in the 1870s with Maxwell’s theory of electromagnetism. The electroweak unification was relatively recent, only half a century ago.

    Given that 350 years has elapsed since our first big successful step in this journey, perhaps it’s less surprising that the path ahead of us is longer still. The notion that a genius will have an insight that results in a fully developed theory of everything in the next few years is a myth. We’re in for a long slog — and even the grandchildren of today’s scientists won’t see the end of it.

    But what a journey it will be.

    See the full article here .


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  • richardmitnick 2:38 pm on May 1, 2019 Permalink | Reply
    Tags: , Charged particles travel faster than light through the quantum vacuum of space that surrounds pulsars., , Dame Susan Jocelyn Bell Burnell (1943 – ) still working, , , space.com   

    From SPACE.com: “Faster-Than-Light Particles Emit Superbright Gamma Rays that Circle Pulsars” 

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    From SPACE.com

    Yasemin Saplakoglu

    The Vela pulsar that lives 1,000 light years from our planet. (Image: © NASA/CXC/Univ of Toronto/M.Durant et al)

    Charged particles travel faster than light through the quantum vacuum of space that surrounds pulsars. As these electrons and protons fly by pulsars, they create the ultrabright gamma-ray flashes emitted by the rapidly twirling neutron stars, new research reveals.

    These gamma-rays, called Cherenkov emissions, are also found in powerful particle accelerators on Earth, such as the Large Hadron Collider near Geneva, Switzerland. The rays are also the source of the bluish-white glow in the waters of a nuclear reactor.


    CERN map

    CERN LHC Tunnel

    CERN LHC particles

    Daya Bay, nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China

    But until now, no one thought that pulsar emissions consisted of Cherenkov radiation.

    That’s in part because of Albert Einstein’s famous theory of relativity, which holds that nothing can travel faster than light in a vacuum. Because of those propositions, scientists previously thought that Cherenkov emissions couldn’t happen in the quantum vacuum of space surrounding pulsars. That area is mostly devoid of matter but home to ghostly quantum particles that flicker in and out of existence.

    So, does this new research mean Einstein’s landmark theory was just violated? Not at all, said study co-author Dino Jaroszynski, a professor of physics at the University of Strathclyde in Scotland.

    Pulsars create crushingly strong electromagnetic fields in the quantum vacuum surrounding the stars. These fields warp, or polarize, the vacuum, essentially creating speed bumps that slow down light particles, Jaroszynski told Live Science. Meanwhile, charged particles such as protons and electrons zoom through these fields, racing past light.

    As charged particles fly through this field, they displace electrons along their path and emit radiation, which gathers into an electromagnetic wave. This wave, like an optical version of a sonic boom, is what we see as the gamma-ray flash, according to a statement.

    The team still doesn’t know exactly how bright these gamma-ray flashes are, Jaroszynski said.

    “What we do know is that, under the right conditions, vacuum Cherenkov radiation outshines synchrotron radiation,” he added, referring to another type of radiation that is emitted from pulsars by charged particles moving along a curved path.

    But the new findings could have implications beyond pulsars, the researchers said.

    “This is a very exciting new prediction because it could provide answers to basic questions such as what is the origin of the gamma-ray glow at the centre of galaxies?” Jaroszynski said in the statement. “It provides a new way of testing some of the most fundamental theories of science by pushing them to their limits.”

    The researchers reported their findings April 25 in the journal Physical Review Letters.

    See the full article here .

    Women in STEM – Dame Susan Jocelyn Bell Burnell

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    Dame Susan Jocelyn Bell Burnell at work on first plusar chart 1967 pictured working at the Four Acre Array in 1967. Image courtesy of Mullard Radio Astronomy Observatory.

    Dame Susan Jocelyn Bell Burnell 2009

    Dame Susan Jocelyn Bell Burnell (1943 – ), still working from http://www. famousirishscientists.weebly.com


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  • richardmitnick 12:05 pm on May 1, 2018 Permalink | Reply
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    From SPACE.com: “Dawn Mission: Shedding Light on Asteroids” 

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    May 1, 2018
    Nola Taylor Redd

    NASA Dawn Spacescraft

    When NASA’s Dawn mission launched in 2007, it was on its way to breaking several records. When it entered orbit around the Vesta, it became the first to orbit a main-belt asteroid. After leaving Vesta, it journeyed on to Ceres, becoming the first spacecraft to visit and then orbit a dwarf planet and the first spacecraft to orbit two extraterrestrial targets.

    The journey hasn’t been smooth. Along the way, the spacecraft lost threeof its four reaction wheels that keep it oriented. It successfully concluded its primary mission to study both targets in 2016. Once it runs out of fuel near the end of 2018, it will continue to orbit Ceres for another 50 years.

    “To me, the real story here is how cool it is that we’re exploring what, in my view, are some of the last uncharted worlds in the inner solar system,” chief engineer and Dawn mission director Marc Rayman told Space.com. “Most people think of asteroids as chips of rock, but these are whole new worlds.”


    This map from NASA’s Dawn mission shows locations of bright material on the dwarf planet Ceres. There are more than 300 bright areas, called “faculae,” on Ceres.
    Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI/Caltech

    Out of this world

    Dawn launched from Cape Canaveral, Florida, on Sept. 27, 2007. Its arrived at the asteroid Vesta on July 16, 2011. The spacecraft spent almost a year in orbit around the second-largest object in the asteroid belt, departing on Sept. 5, 2012.

    On March 6, 2015, Dawn entered orbit around Ceres. Ceres is by far the most massive object in the asteroid belt between Mars and Jupiter, weighing in at nearly two-thirds the total mass of the belt. Its massive size and roundness means it qualifies as a dwarf planet. Unlike a full-size planet, a dwarf planet is a round object that fails to clear out its orbit. Dawn was just barely the first mission to arrive at a dwarf planet; NASA’s New Horizons mission zipped by Pluto only a few months later (though, in fairness, New Horizons launched first but had much farther to travel).

    Dawn traveled 1.7 billion miles (2.8 billion kilometers) to reach Vesta, then another 3.1 billion miles (4.9 billion km) to Ceres. Boosted by an ion propulsion system, the spacecraft took four days to accelerate from 0 to 60 mph (0 to 97 km/h) at maximum throttle. Each engine produces about the same amount of force as a single piece of paper notebook paper presses against your hand.

    Over time, however, that small force adds up. In 2010, it surpassed the previous record for velocity change held by NASA’s Deep Space 1 when its accumulated acceleration over the mission exceeded 9,600 MPH (4.3 km per second).

    “I am delighted that it will be Dawn that surpasses DS1’s record,” Rayman, who was a previous project manager for Deep Space 1, said in a statement. “It is a tribute to all those involved in the design and operations of this remarkable spacecraft.

    NASA Deep Space 1

    Ion engines are extremely fuel-efficient — Dawn only carried 937 lbs. (425 kilograms) of xenon propellant at launch — but the fuel won’t last forever. The spacecraft also carried 100.5 lbs. (45.6 kg) of hydrazine propellant used to change the spacecraft’s orientation, and that tank is quickly running dry. Dawn is expected to run out of hydrazine fuel in the second half of 2018.

    “When the last of the hydrazine is exhausted, the spacecraft will no longer be able to control its orientation, so it won’t be able to point its solar arrays at the sun, its sensors at Ceres, nor its antenna at Earth,” Rayman told Space.com in 2017. “That will be the end of Dawn’s operational life.”

    Dawn will continue to orbit Ceres for decades. Planetary protection rules insisted on at least 20 years before the spacecraft crashed into the dwarf planet, to reduce the chances of contamination. The Dawn team opted to set the spacecraft on an orbit that would keep it aloft for at least 50 years.

    The dwarf planet Ceres spins in this series of photos captured by NASA’s Dawn spacecraft on April 29, 2017, when the probe was between Ceres and the sun.
    Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

    Exploring Vesta

    Dawn’s first stop was Vesta, a rocky asteroid and the second largest inhabitant of the asteroid belt, where it made several significant findings at Vesta. It discovered a geologic landscape that scientists called “exotic and diverse,” and compiled the first map of the 330-mile (530 km) wide body.

    The Dawn team reasoned that reaching those temperatures would have caused the heavy elements to melt and sink down to the core in a process known as differentiation. In fact, joked JPL’s Carol Raymond, Dawn’s deputy principal investigator, “We like to call Vesta ‘the smallest terrestrial planet.'”

    Dawn also confirmed that Vesta is the source of the howardite-eucrite-diogenite (HED) meteorites found on Earth and Mars. The Dawn team thinks that the HEDs came from an impact basin the team named Rheasilvia. The basin itself has an age of about 1 billion years, and formed from a massive collision that stripped the away the bulk of the asteroid’s southern hemisphere. With a diameter of 310 miles (500 km), Rheasilvia is nearly as large as Vesta itself.

    “Vesta likely came close to shattering,” said Raymond.

    A second basin showcases another dangerous impact beneath Rheasilvia. Named Veneneia, the basin is nearly as big and nearly a billion years younger than Rheasilvia and may be another potential source for HED meteorites.

    Research from Dawn also suggests that Vesta may hide ice beneath its surface. Originally, the scientists suspected that roughness on the asteroid’s surface came from impacts, but Dawn’s data suggests that some of the features are caused by ice buried beneath the surface.

    “We suggest that modifications of the surface by melting of buried ice could be responsible for smoothing those areas,” Essam Heggy, a planetary scientist at the University of Southern California in Los Angeles, told Space.com. “Buried ice could have been brought to the surface after an impact, which caused heated ice to melt and travel up through the fractures to the surface.”

    “We went to Vesta to fill in the blanks of our knowledge about the early history of our solar system,” said Dawn principal investigator Christopher Russell, of UCLA, said in a statement.

    “Dawn has filled in those pages, and more, revealing to us how special Vesta is as a survivor from the earliest days of the solar system. We can now say with certainty that Vesta resembles a small planet more closely than a typical asteroid.”


    215 years after its discovery, we know so much more about the dwarf planet Ceres. NASA’s Dawn spacecraft captured this amazing view of Ceres in the asteroid belt, showing the dwarf planet’s Occator Crater in false color, after it arrived in orbit around Ceres in 2015. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

    Ceres science

    While Vesta is rocky, Ceres is surprisingly icy. Before Dawn arrived, scientists estimated that water could make up as much as a quarter of the dwarf planet, though that water would be tucked beneath the surface. Observations made by the Hubble Space Telescope revealed a cloud of vapor that suggested the dwarf planet might be degassing, though no strong signs of such activity has been spotted by Dawn.

    On the surface, Ceres appears relatively bland. Aside from a few craters — though less than scientists anticipated — the only outstanding feature is a single mountain, Ahuna Mons. Researchers suspected the mountain was a cryovolcano, oozing ice instead of hot lava. Further studies revealed that, while it may be thought of as a “lonely mountain” today, it could have had companions in the past. Made of ice, these mountains may have slowly flowed back onto the surface.

    “We think we have a very good case that there have been lots of cryovolcanoes on Ceres but they have deformed,” Dawn researcher Michael Sori of the University of Arizona in Tucson said in a statement.

    The same fate may await the lonely volcano.

    “Ahuna Mons is at most 200 million years old. It just hasn’t had time to deform,” Sori said.

    From a distance, Dawn caught sight of bright spots from a distance that soon resolved into more than 130 bright patches, most of them tied to craters. Initially thought to be Epsom salt, the patches turned out to be a version of salts that require water to form. Since water skips to gas almost immediately on the dwarf planet’s surface, that suggests that the liquid must lie beneath the crust.

    “That was something we had not expected,” Russell told Space.com. “The carbonates are a very strong indication of the processes now that we believe took place in the interior, that makes it more Earthlike, when it can alter the chemistry inside.”

    “It’s not something that’s just lying around out there in space,” he added.

    The flowing ice that formed Ahuna Mons and the presence of salts suggest that an ancient ocean once lie beneath the crust of Ceres.

    “We believe these bright spots are a sign that Ceres once had a global ocean,” planetary geologist Lynnae Quick, of the Smithsonian Institute in Washington, D.C., told Space.com.

    “It’s possible there is still brine coming up to the surface,” Nathan Stein, a planetary scientist at the California Institute of Technology in Pasadena, told Space.com. “It’s certainly intriguing.”

    Researchers also spotted ammonia-rich clays on the dwarf planet. Ammonia is more commonly found in the outer solar system. The material could have been delivered to Ceres by comets, or its presence could be a sign that the dwarf planet formed in the outer solar system.

    These and other discoveries by Dawn have revealed that Ceres is a rich, evolving world.

    “The IAU [International Astronomical Union] has defined what a planet is in a particular way,” Russell said, “but I think of a planet more as a body which, when it’s big enough and has enough activity … is now making things, producing things in its interior that are not just sitting there for the eons but in fact that the body evolves with time inside.”

    Additional resources

    NASA Dawn mission
    Dawn mission home page (JPL)

    See the full article here .

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  • richardmitnick 12:15 pm on April 2, 2018 Permalink | Reply
    Tags: , , , , , space.com, Target is asteroid 162173 Ryugu   

    From SPACE.com: “Hayabusa2: Japan’s 2nd Asteroid Sample Mission” 

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    March 30, 2018
    Elizabeth Howell

    JAXA/Hayabusa 2 Credit: JAXA/Akihiro Ikeshita

    Hayabusa2 is a Japanese asteroid-sampling spacecraft that launched in December 2014. It is currently on the way to asteroid 162173 Ryugu and will arrive there between June and July 2018, according to the Japanese Aerospace Exploration Agency (JAXA). The mission is a follow-up of Hayabusa, which returned samples of asteroid 25143 Itokawa to Earth in 2010 despite numerous technical difficulties.

    JAXA’s original Hayabusa spacecraft

    Mission development

    Hayabusa2 was first selected by Japan’s Space Activities Commission in 2006, and received funding in August 2010 (shortly after Hayabusa’s return). The cost is estimated at 16.4 billion yen ($150 million).

    A year after launch, Hayabusa2 briefly returned to Earth. The spacecraft made a planned flyby to get a speed boost by using the Earth’s gravitational field. Meanwhile, astronomers are doing periodic observations of Ryugu to gather information ahead of the spacecraft’s arrival. The 600-kg spacecraft is expected to remain at the asteroid for 18 months, and return to Earth in 2020 with samples on board.

    The basic configuration of Hayabusa2 is very similar to Hayabusa, except for some improved technology, according to JAXA. Here are some of the improvements on Hayabusa2.

    Ion engine: Improving the lifespan of the neutralizers (which failed on Hayabusa) by strengthening the internal magnetic field. Also, more careful checks of the ion engine will be performed to improve its propulsion generation and ignition stability.
    Sampler mechanism: Better seal performance, more compartments and an improved mechanism for picking up material from the surface. On Hayabusa, it was unclear at the time of sample collection if it had actually picked up something from the surface.
    Re-entry capsule: JAXA has added an instrument to measure acceleration, movement and interior temperatures during flight. (The Hayabusa capsule broke up during re-entry.)
    Flat antennas: Instead of Hayabusa’s parabolic antenna, Hayabusa2 will have flat antennas. This will allow it to have the same communications capacity as Hayabusa, while saving on weight (and launch fuel). “A flat antenna can perform to the same capacity as a parabolic antenna due to technological improvements … Thanks to the flat design, the weight of the antenna is reduced to one-fourth, compared to a parabolic antenna whose performance is the same.” JAXA said.

    Here are the major instruments of the mission:

    Small Carry-on Impactor (SCI): This will create an artificial crater on the surface of the asteroid. Hayabusa2 will look at the changes on the surface before and after the impact takes place. They will also sample the crater to get “fresh” materials from underground.
    Near InfraRed Spectrometer (NIRS3) and Thermal Infrared Imager (TIR): The spectrometer will look at mineral composition of the asteroid, and the properties of water there. The imager will study the temperature and thermal inertia (resistance to changing temperature) of the asteroid.
    The small rovers MINERVA-II: Three small rovers will bounce along the surface and collect data from close-up. They are successors to the MINERVA rover aboard Hayabusa, which failed to meet its target after launch.
    A small lander (MASCOT): This is a lander that will jump only once after it arrives on the surface. It will also perform close-up observations of the surface. This instrument is built by DLR (Germany’s space agency) and the CNES (France’s space agency).

    Science goals

    Japan chose a different type of asteroid to study for Hayabusa2. The goal is to collect information about a wide variety of asteroids across the solar system. Ryugu is a C-type asteroid, meaning that it is carbonaceous; with a high percentage of carbon, this is the most common type of asteroid in the solar system. (The target for Hayabusa was Itokawa, an S-type asteroid — meaning that it is made up more of stony materials and nickel iron.)

    Ryugu is an older type of body than Itokawa, and likely contains more organic or hydrated minerals, JAXA stated. Organics and water are key elements for life on Earth, although their presence on other bodies doesn’t necessarily mean life itself. “We expect to clarify the origin of life by analyzing samples acquired from a primordial celestial body such as a C-type asteroid to study organic matter and water in the solar system, and how they co-exist while affecting each other,” JAXA said.

    See the full article here .

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  • richardmitnick 12:49 pm on January 25, 2018 Permalink | Reply
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    From SETI Institute via SPACE.com: “‘Search for Extraterrestrial Intelligence’ Needs a New Name, SETI Pioneer Says” 

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    SETI Institute



    January 25, 2018
    Calla Cofield

    Jill Tarter at the Arecibo radio telescope in Puerto Rico, which was used to search for communications signals from alien civilizations.
    Credit: Acey Harper/The LIFE Images Collection/Getty

    NAIC/Arecibo Observatory, Puerto Rico, USA, at 497 m (1,631 ft)

    Astrophysicist Jill Tarter is one of the world’s best-known leaders in the search for extraterrestrial intelligence, or SETI. For 35 years, she served as the director of the Center for SETI Research (part of the SETI institute) and was also the project scientist for NASA’s SETI program, before its cancellation in 1993.

    Despite her longtime association with that four-letter acronym, Tarter says it’s time for “SETI” to be rebranded.

    At a recent meeting of the National Academy of Sciences’ Committee on Astrobiology Science Strategy for the Search for Life in the Universe, held here at the University of California, Irvine, Tarter explained that the phrase “search for extraterrestrial intelligence” generates an incorrect perception of what scientists in this field are actually doing. A more appropriate title for the field, she said, would be “the search for technosignatures,” or signs of technology created by intelligent alien civilizations.

    “We need to be very careful about our language,” Tarter said during a presentation at the committee meeting on Jan. 18. “SETI is not the search for extraterrestrial intelligence. We can’t define intelligence, and we sure as hell don’t know how to detect it remotely. [SETI] … is searching for evidence of someone else’s technology. We use technology as a proxy for intelligence.

    “[The acronym] ‘SETI’ has been problematic in history, and we should just drop [it] and just continue to talk about a search for technosignatures,” she said.

    Signs of life

    What constitutes a “technosignature”? Tarter reviewed some of the possibilities that she and other SETI scientists have proposed.

    “We have a pragmatic definition for technology, which is the ability to deliberately modify an environment in ways that can be sensed over interstellar or interplanetary distances, including the unintended consequences of that modification,” Tarter said. “Life does this, but it doesn’t do it deliberately.”

    One technosignature that scientists have been actively seeking for decades is communication signals. These could include signals used by members of an alien civilization to communicate with each other or attempts to communicate with other civilizations. The SETI Institute continues to search for alien communications in radio waves, using the Allen Telescope Array.

    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)

    (Tarter was the inspiration for the main character in Carl Sagan’s novel Contact, which was adapted into a movie; in that story, aliens make contact with Earth via radio waves.) But recent SETI efforts have expanded to look for other mediums of alien communication, and SETI scientists have theorized that an interstellar civilization might use laser light to communicate.

    Laser SETI, the future of SETI Institute research

    Science-fiction writer Arthur C. Clarke wrote that “any sufficiently advanced technology is indistinguishable from magic,” which would mean that alien technology could be as mysterious and unexplainable to humans as technologies that appear in science-fiction TV shows and movies. That opens up a dauntingly large range of possibilities for what technosignatures might look like. What if an alien civilization were communicating via a mechanism that Earth-based scientists haven’t discovered yet? Would humans immediately recognize these “magical” technosignatures, or would we not see them as unnatural?

    Tarter said she prefers to focus on a slight alteration of Clarke’s prediction written by the futurist Karl Schroeder: “Any sufficiently advanced technology is indistinguishable from nature.”

    “[The system] will be so efficient that there will be no wastage, and [it] will appear to be natural,” Tarter said. If this prediction is correct, it might also be impossible for humans to identify technosignatures from very advanced civilizations. But Tarter uses it as a jumping-off point to brainstorm how scientists might identify technologies that have not yet reached that level of sophistication.

    In the field of exoplanet science, new techniques and new instruments are increasing scientists’ ability to study exoplanets and gather information about their atmospheres and surface conditions. The central focus in that field is to find habitable planets, or planets with “unintelligent” life-forms (like plants). Tarter said those tools could also provide the opportunity to look for signs of technology that artificially alters a planet’s climate or conditions.

    “As we begin to look for exoplanets and image them, you might get an unexpected glint, [because] maybe mirrors re cooling their planet, reflecting light away from the planet,” Tarter said.

    But a technosignature wouldn’t necessarily have to be the detection of the technology itself. The artificial alteration of a planet’s climate could be revealed simply because the planet in question is too close or too far away from its parent star to have the observed climate. A star system with multiple planets that all have similarly moderate, habitable climates, despite their particular proximity to the parent star, could indicate large-scale bioengineering by an intelligent civilization, Tartar said.

    “[An alien civilization] also might want to decrease latitudinal variation in temperature; maybe they want more of their planet to be nice and cozy,” Tarter said. “It’s going to take a lot of energy to do that, but I don’t know the physics that says you can’t.”

    Into the future

    The search for technosignatures is daunting, but Tarter says now is “a really opportunistic time” for it. The field is benefiting from new instruments and a wider array of instruments. SETI scientists are often searching through large volumes of data, seeking the proverbial needle in the haystack. Artificial intelligence and artificial “neural networks” can help aid this effort by combing through this vast data to search for signals that the scientists program machines to find and also allowing “the data to tell us what kind of signals are there,” Tarter said, which increases the odds of finding an unanticipated technosignature.

    Tarter listed multiple SETI projects and initiatives that are underway around the world. The most high-profile is Breakthrough Listen, a private initiative that has funded a group of researchers at the University of California, Berkeley to utilize various telescopes to search for signs of alien communication or other possible technosignatures.

    Breakthrough Listen Project


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

    GBO radio telescope, Green Bank, West Virginia, USA

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

    The Berkeley group has led an effort to crack the mystery of Boyajian’s star, which has exhibited a very strange pattern of dimming and brightening. A few years ago, some researchers proposed that perhaps the strange light patterns were created by an alien megastructure orbiting the star — a fantastic example of a technosignature. Though that possibility has largely been ruled out, the Breakthrough Listen researchers are still working to understand this phenomenon.

    The challenge of searching for alien technosignatures may be daunting, but Tarter remains unwavering in her optimism for the search for life beyond Earth.

    “In 2004, Craig Venter and Daniel Cohen made a really bold statement: They said the 20th century had been the century of physics, but the 21st century would be the century of biology,” Tarter said. “I think they were right, but I don’t think they were bold enough. Because I think the 21st century is going to be the century of biology on Earth and beyond.”

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  • richardmitnick 11:18 pm on December 2, 2017 Permalink | Reply
    Tags: , Lightning Bolts Are Churning Out Antimatter All Over Planet Earth, , space.com   

    From SPACE.com: “Lightning Bolts Are Churning Out Antimatter All Over Planet Earth” 

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    November 27, 2017
    Rafi Letzter

    Credit: Vasin Lee/Shutterstock

    Particles split in the hot belly of a lightning bolt. Radioactive particles decay in the afterglow. Gamma rays rain down to Earth.

    Teruaki Enoto, a physicist at Kyoto University in Japan, proved for the first time, in a paper published Nov. 23 [Nature], that lightning bolts work as natural particle accelerators. Enoto and his co-authors’ results confirm for the first time speculation dating back to 1925 [Proceedings of the Physical Society of London] about this phenomenon. Back then, scientists suggested that energized, radioactive particles might zip through the booms and flashes of a thunderstorm. Those particles emit energy at precise wavelengths, which Enoto and colleagues are the first to detect.

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  • richardmitnick 2:04 pm on November 8, 2017 Permalink | Reply
    Tags: A rapidly spinning neutron star called a magnetar, A years-long supernova explosion challenges scientist's current understanding of star formation and death, , , , , , For now the event remains a mystery, Las Cumbres Observatory [based] in Goleta California, Pulsation pair instability (PPI) supernova, space.com, The existence of iPTF14hls has far-reaching implications   

    From SPACE.com: “Bizarre 3-Year-Long Supernova Defies Our Understanding of How Stars Die” 

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    November 8, 2017
    Harrison Tasoff

    A massive star reaches the end of its life in an artist’s conception of a supernova. Credit: M. Kornmesser/ESO

    The appearance of a years-long supernova explosion challenges scientist’s current understanding of star formation and death, and work is underway to explain the bizarre phenomenon.

    Stars more than eight times the mass of the sun end their lives in fantastic explosions called supernovas. These are among the most energetic phenomena in the universe. The brightness of a single dying star can briefly rival that of an entire galaxy. Supernovas that form from supermassive stars typically rise quickly to a peak brightness and then fade over the course of around 100 days as the shock wave loses energy.

    In contrast, the newly analyzed supernova iPTF14hls grew dimmer and brighter over the span of more than two years, according to a statement by Las Cumbres Observatory [based] in Goleta, California, which tracked the object. Details of the discovery appeared on Nov. 8 in the journal Nature.

    Las Cumbres Observatory Global Telescope Network 1-meter telescope node at Cerro Telolo, Chile

    An inconspicuous discovery

    Supernova iPTF14hls was unremarkable when first detected by a partner telescope in San Diego on Sept. 22, 2014. The light spectrum was a textbook example of a Type II-P supernova, the most common type astronomers see, lead author Iair Arcavi, an astronomer at the University of California, Santa Barbara, told Space.com. And the supernova looked like it was already fading, he said.

    The observatory was in the middle of a 7.5-year collaborative survey, so Arcavi focused on more-promising objects. But in February, 2015, Zheng Chuen Wong, a student working for Arcavi that winter, noticed the object had become brighter over the past five months.

    “He showed me the data,” Arcavi said, “and he [asked], ‘Is this normal?’ and I said, ‘Absolutely not. That is very strange. Supernovae don’t do that,'” Arcavi said.

    At first, Arcavi thought it might be a local star in our galaxy, which would appear brighter because it was closer, he said. Many stars are also known to have variable brightness. But the light signature revealed that the object was indeed located in a small, irregular galaxy about 500 million light-years from Earth.

    And the object only got weirder. After 100 days, the supernova looked just 30 days old. Two years later, the supernova’s spectrum still looked the way it would if the explosion were only 60 days old. The supernova recently emerged from behind Earth’s sun, and Arcavi said it’s still bright, after roughly three years. But at one one-hundredth of its peak brightness, the object appears to finally be fading out.

    “Just to be clear, though, there is no existing model or theory that explains all of the observations we have,” said Arcavi. The supernova may fade out; it may grow brighter, or it may suddenly disappear.

    One reason for Arcavi’s uncertainty is that a supernova was seen in the same location in 1954. This means that the event Acavi has been observing, whatever it is, may actually be 60 years running. There’s a 1 to 5 percent chance the two events are unrelated, but that would be even more surprising, said Arcavi. Astronomers have never observed unrelated supernova in the same place decades apart. “We are beyond the cutting-edge of models,” Arcavi said.

    Supernova iPTF14hls dwarfs typical supernovas in both brightness and longevity. And the event’s dramatic fluctuations pose an exciting challenge for the astronomical community to explain.
    Credit: Credit: S. Wilkinson/LCO

    Beyond cutting edge

    “I’m not sure, and I don’t think anyone else is sure, just what the hell is happening,” astrophysicist Stanford Woosley, at University of California, Santa Cruz, told Space.com. “And yet it happened, and so it begs explanation.”

    Woosley is not affiliated with the study, but he is among the theoreticians working to understand the event. Two hypotheses show promise in explaining it, he said.

    The first involves the famous equation E = mc2. With this formula , Albert Einstein demonstrated that matter and energy are fundamentally interchangeable. Stars burn by converting matter into energy, fusing lighter elements like hydrogen and helium into heavier elements, which build up in the star’s core and also release energy. When a star more than 80 times the mass of the sun reaches a temperature of 1 billion degrees Celsius (1.8 billion degrees Fahrenheit), this energy-matter equivalence produces pairs of electrons and their antiparticle counterparts, positrons, Woosley said. The process robs the star of energy, and so the object shrinks.

    But as this happens, the temperature rises in the star’s core. At 3 billion C (5.4 billion F), oxygen fuses explosively, blowing off massive amounts of material and resetting the cycle. This process repeats until the star reaches a stable mass, explained Woosley. When the front of an ejected shell of material hits the trailing edge of a previous shell, it releases energy as light.

    The star continues to fuse oxygen and the elements of greater masses, up until iron, at which point the reaction fails to release enough energy to keep the star from collapsing in on itself.Eventually, a star like the one that gave rise to iPTF14hls will collapse into a black hole without another explosion, said Woosley.

    This image depicts a simulated collision between two shells of matter ejected by subsequent pulsation pair instability supernova explosions.
    Credit: Ke-Jung Chen/School of Physics and Astronomy, University of Minnesota

    This phenomenon, called a pulsation pair instability (PPI) supernova, could account for iPTF14hls’ sustained luminosity as well as the object’s varying brightness. This explanation would require the star to have been 105 times the mass of the sun, said Woosley. However, the PPI model cannot account for the tremendous amount of energy iPTF14hls has released. The first explosion of 2014 had more energy than the model predicts for all the explosions combined, said Arcavi.

    What’s more, this phenomenon has yet to be verified observationally. “Stars between 80 and 140 solar masses, which do this kind of thing, have to exist,” said Woosley, “and they have to die, and so, somewhere, this has to be going on.” But no one has seen it yet, he said.

    A magnetic superstorm

    An alternative explanation involves a star 20 to 30 times the mass of Earth’s sun. After a more conventional supernova, such a star could have condensed into a rapidly spinning neutron star, called a magnetar.

    A neutron star packs the mass of 1.5 suns into an object with a diameter about the size of New York City. A neutron star rotating at 1,000 times per second would have more energy than a supernova, according to Woosley. It would also generate a magnetic field 100 trillion to 1 quadrillion times the strength of Earth’s field. As the star spun down over the course of several months, its incredible magnetic field could transfer the star’s rotational energy into the remnants of the supernova that it formed from, releasing light, Woosley explained.

    An artist depicts a magnetar in the star cluster Westerlund 1. The luminous arcs follow the object’s intense magnetic field. Credit: L. Calçada/ESO

    “It’s like there’s a lighthouse down in the middle of the supernova,” said Woolsey.

    But the magnetar explanation is not perfect, either. It has trouble explaining the dips and peaks in iPTF14hls’ brightness, and the physics behind how such a phenomenon might work is still uncertain, said Woosley.

    As iPTF14hls sheds energy, Arcavi said he hopes to be able to see deeper into the object’s structure. If it is a magnetar, then he expects to see X-rays, previously obscured by the supernova itself, beginning to break through, he said. “Maybe by combining pulsation pair instability with [a magnetar], you can start to explain the supernova,” Arcavi said.

    Keeping busy while keeping watch

    The existence of iPTF14hls has far-reaching implications, the researchers said. At 500 million light-years away, the supernova is still relatively close to Earth, and the universe is practically the same today — in terms of composition and organization —as it was when this event occurred, according to Arcavi. If the event was a PPI supernova, it tells astronomers that stars more than 100 times the mass of the sun — thought to be more prevalent in the early universe — are still forming today.

    The event also had far more hydrogen than researchers expected to see. The explosion in 1954 should have expelled nearly all of the star’s hydrogen, said Arcavi. Astrophysicists will have to revisit their models of supernovas to understand how this can occur, he said.

    The finding has ramifications for the study of galaxies as well. “The energy of the gravity that’s keeping that galaxy together is about the same order of magnitude as the energy that was released in the supernova,” Arcavi said. “So, a few of these in a galaxy could actually unbind the entire galaxy.”

    Arcavi and his team plan to continue monitoring iPTF14hls for at least one to two years. And a suite of international telescopes and observatories will join the effort. Swedish colleagues at the Nordic Optical Telescope, in the Canary Islands, will track the object as it continues to dim beyond what Arcavi’s telescope array can detect. NASA’s Swift spacecraft will look for X-ray emissions, while the Hubble Space Telescope is scheduled to image the location beginning in December, and others will follow, Arcavi said.

    For now, the event remains a mystery.

    “It’s just a puzzle in the sky,” said Woosley. “That’s what we live for, what astronomers love.”

    See the full article here .

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  • richardmitnick 1:53 pm on November 3, 2017 Permalink | Reply
    Tags: , , , , Heart Nebula IC 1805, Miguel Claro, space.com   

    From SPACE.com: “Star-Speckled Heart Nebula Glows Red in Lovely Deep-Space Photo” 

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    November 3, 2017
    Miguel Claro

    Miguel Claro is a professional photographer, author and science communicator based in Lisbon, Portugal, who creates spectacular images of the night sky. As a European Southern Observatory Photo Ambassador and member of The World At Night and the official astrophotographer of the Dark Sky Alqueva Reserve, he specializes in astronomical “Skyscapes” that connect both Earth and night sky. Join Miguel here as he takes us through his photograph, “Heart Nebula: When the Universe Falls in Love.”


    Heart Nebula IC 1805 captured by astrophotographer Miguel Claro from Cumeada Observatory, headquarters of Dark Sky Alqueva Reserve, Reguengos de Monsaraz, Portugal.
    Credit: Miguel Claro
    The beautiful Heart Nebula, also known as IC 1805, is a bright, red emission nebula with a shape that resembles a human heart.
    This cosmic cloud glows red because it’s filled with ionized hydrogen gas. Darker lanes of interstellar dust create a dark silhouette in the center of the luminous, heart-shaped outline.

    Located about 7,500 light-years from Earth, the Heart Nebula resides in the Perseus Arm of the Milky Way galaxy, in the constellation Cassiopeia. The brightest section, a fish-shaped knot at the cusp of the heart, was discovered before the rest of the Heart Nebula and is separately classified as NGC 896, or the Fishhead Nebula.

    The nebula’s red glow and peculiar shape are a result of intense radiation emanating from a small cluster of stars near the nebula’s core. Known as Melotte 15, this cluster contains a few young, hot and bright-blue supergiant stars nearly 50 times the mass of our sun. These stars are only about 1.5 million years old. (For comparison, our sun is about 4.6 billion years old). Many more dim stars that are only a fraction of our sun’s mass also reside in this cluster.

    Stellar wind, or the stream of charged particles that flows outward from the newborn stars, has sculpted the shape of the Heart Nebula by pushing its clouds of dust and gas outward from the core.

    To capture this image of the Heart Nebula, I used a Takahashi FSQ-106ED refractor telescope with an EM-200 auto-guided mount and a Canon EOS 60Da DSLR astrophotography camera. The camera was programmed to shoot with an ISO setting of 1600 and an exposure time of 210 seconds. The final composite combines 12 frames with a combined exposure time of 42 minutes. Image processing was completed with PixInsight 1.8 and Adobe Photoshop CS6.

    The image was taken from the Cumeada Observatory at the Dark Sky Alqueva Reserve in Reguengos de Monsaraz, Portugal.

    See the full article here .

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  • richardmitnick 4:21 pm on October 30, 2017 Permalink | Reply
    Tags: , , , , Diary of a Supernova: How (Some) Stars Blow Up, space.com   

    From SPACE.com- “Diary of a Supernova: How (Some) Stars Blow Up” 

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    October 30, 2017
    Paul Sutter

    This supernova remnant was famously discovered in 1604 by Johannes Kepler.
    Credit: X-ray: NASA/CXC/NCSU/M.Burkey et al; Infrared: NASA/JPL-Caltech

    NASA/Chandra Telescope

    NASA Infrared Telescope facility Mauna Kea, Hawaii, USA, 4,207 m (13,802 ft) above sea level

    Everything in the universe someday comes to an end. Even stars. Though some might last for trillions of years, steadily sipping away at their hydrogen reserves and converting them to helium, they eventually run out of fuel. And when they do, the results can be pretty spectacular.

    Our own sun will make a mess of the solar system when it enters the last stages of its life in 4 billion years or so. It will swell, turn red (consuming Earth in the process) and cast off its outer layers, giving one last gasp as a planetary nebula before it settles down into post-fusion retirement as a white dwarf.

    The most spectacular deaths, though, are reserved for the most massive stars. Once an object builds up to at least eight times the mass of the sun, interesting games can be played inside the core, with … explosive results.

    To understand how this works, let’s work through a thought experiment. Imagine that the gravity were to increase a tiny bit, then the increased pressure would raise the intensity level of the fusion reactions, which, in turn, would release more energy and thus prevent further collapse of the star. And on the opposite end, if the fusion party were to get just a little bit wilder, it would cause to star to overinflate, lessening the grip of gravity and easing the pressure in the core, cooling things off.

    This balancing act enables a star to last millions, billions and even trillions of years.

    Until it doesn’t.

    The game can be played as long as there’s fuel to keep the lights on. As long as there’s a sufficient supply of hydrogen near the core, the star can keep cranking out the helium and keep resisting the inevitable crush of gravity.

    A crushing force

    I’m not just using a flair of language when I describe the crush of gravity as inevitable. Gravity never stops, never sleeps, never halts. It can be resisted for a long time, but not forever.

    As a star ages, it builds up a core of inert helium. Once the hydrogen supply exhausts itself, there’s nothing to stop the infalling weight of the surrounding material. That is, until the core reaches a scorching temperature of 100 million kelvins (180 million degrees Fahrenheit), at which point helium itself begins to fuse.

    Hooray, the party’s back on! Well, for a while, at least. Helium fusion isn’t as efficient as good ol’ hydrogen, so the reactions happen at an even faster pace to compete with gravity.

    While the “main sequence” of a star’s life may last hundreds of millions of years as it happily burns hydrogen, the helium phase barely lasts a single million.

    The product of helium fusion is carbon and oxygen, and the same game gets played again, but at even higher temperatures and shorter timescales. Once the helium is sucked dry, the core collapses and intensifies to 1 billion K (1.8 billion degrees F), allowing those new elements to get their turn.

    Out of control

    Then, silicon fuses at around 3 billion K (5.4 billion degrees F) in the core, generating iron. Surrounded by plasmatic onion-like layers of oxygen, neon, carbon, helium and hydrogen, the situation at the center starts to get dicey.

    The problem is that, due to its internal nuclear configuration, fusing iron consumes energy rather than releases it. Gravity keeps pressing in, shoving iron atoms together, but there’s no longer anything to oppose its push.

    In less than a day, after millions of years of peaceful nuclear regime changes, the star forms a solid core of iron, and everything goes haywire.

    In a matter of minutes, the intense gravitational pressure slams electrons into the iron nuclei, transforming protons into neutrons. The small, dense neutron core finally has the courage to resist gravity, not by releasing energy but through an effect called degeneracy pressure. You can only pack so many neutrons into a box; eventually, they won’t squeeze any tighter without overwhelming force, and in the first stages of a supernova explosion, even gravity can’t muster enough pull.

    So now you have, say, a couple dozen suns’ worth of material collapsing inward onto an implacable core. Collapse. Bounce. Boom.

    The inside-out inferno

    Except there’s a stall. The shock front, ready to blast out from the core and shred the star to stellar pieces, loses energy and slows down. There’s a bounce but no boom.

    To be perfectly honest, we’re not exactly sure what happens next. Our earliest simulations of this process failed to make stars actually blow up. Since they do blow up in reality, we know we’re missing something.

    For a while, astrophysicists assumed neutrinos might come to the rescue. These ghostly particles hardly ever interact with normal matter, but they’re manufactured in such ridiculously quantities during the “bounce” phase that they can reinvigorate the shock front, filling its sails so it can finish the job.

    But more sophisticated simulations in the past decade have revealed that not even neutrinos can do the trick. There’s plenty of energy to power a supernova blast, but it’s not in the right place at the right time.

    The initial moments of a supernova are a very difficult time to understand, with plasma physics, nuclear reactions, radiation, neutrinos, radiation — a whole textbook’s worth of processes happening all at once. Only further observations and better simulations can fully unlock the final moments of a star’s life. Until then, we can only sit back and enjoy the show.

    See the full article here .

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  • richardmitnick 10:21 am on October 29, 2017 Permalink | Reply
    Tags: , , , , , Dwarf Planets: Science & Facts About the Solar System’s Smaller Worlds, space.com   

    From SPACE.com: “Dwarf Planets: Science & Facts About the Solar System’s Smaller Worlds” 

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    October 27, 2017
    SPACE.com Staff
    No writer credit found

    Dwarf planet Eris Credit: ESO/L. Calçada

    Dwarf planets are worlds that are too small to be considered full-fledged planets, but too large to fall into smaller categories.

    In recent years, there’s been a lot of hubbub about Pluto losing its status as one of the planets of the solar system. Pluto is no longer considered the ninth planet in the series of major planetary objects, but instead is now just one of the many so-called “dwarf planets.” The debate started anew after the New Horizons mission passed by Pluto in 2015, revealing a world of surprising geological complexity. As of 2017, delegates from the mission are trying to get Pluto’s planethood status back.

    Astronomers estimate that there could be as many as 200 dwarf planets in the solar system and the Kuiper Belt. But the differences between planets and dwarf planets may not be obvious at first.

    Kuiper Belt. Minor Planet Center

    Dwarf planets of the solar system

    The International Astronomical Union defines a planet as being in orbit around the sun, has enough gravity to pull its mass into a rounded shape (hydrostatic equilibrium), and has cleared its orbit of other, smaller objects. This last criterion is the point at which planets and dwarf planets differ. A planet’s gravity either attracts or pushes away the smaller bodies that would otherwise intersect its orbit; the gravity of a dwarf planet is not sufficient to make this happen.

    Meet the dwarf planets of our solar system, Pluto Eris, Haumea, Makemake and Ceres. Credit: Karl Tate, SPACE.com contributor.

    As of 2014, the IAU recognizes five named dwarf planets: Ceres, Pluto, Eris, Haumea, and Makemake. But those aren’t the only ones. Other solar system bodies that are possibly dwarf planets include Sedna and Quaoar, small worlds far beyond Pluto’s orbit, and 2012 VP113, an object that is thought to have one of the most distant orbits found beyond the known edge of our solar system. The object DeeDee could also be a dwarf planet, according to observations made in 2017. According to NASA, scientists think that there may be more than a hundred dwarf planets awaiting discovery.

    However, the debate over the status of dwarf planets, particularly Pluto, remains a hot topic. The primary concern stems from the requirement for a planet to clear out its local neighborhood.

    “In no other branch of science am I familiar with something that absurd,” New Horizons principle investigator Alan Stern told Space.com in 2011. “A river is a river, independent of whether there are other rivers nearby. In science, we call things what they are based on their attributes, not what they’re next to.”

    Is a dwarf planet a separate entity from a planet, or simply another classification? The question may not be settled in the near future.


    Ceres is the earliest known and smallest of the current category of dwarf planets. Sicilian astronomer Giuseppe Piazzi discovered Ceres in 1801 based on the prediction that the gap between Mars and Jupiter contained a missing planet. It is only 590 miles (950 km) in diameter and has a mass of just 0.015 percent that of Earth.

    In fact, Ceres is so small that it is classified as both a dwarf planet and an asteroid, and is often named in scientific literature as one of the largest asteroids in the solar system. Although it makes up approximately a fourth of the mass of the asteroid belt, it is still 14 less massive than Pluto.

    Unlike its asteroid neighbors, Ceres has a nearly round body. The rocky dwarf planet may have water ice beneath its crust. In 2014, the European Space Agency’s Herschel Space Observatory detected water vapor spewing from two regions on Ceres.

    NASA’s robotic Dawn mission arrived at Ceres in 2015. The mission has shown many interesting features on its surface, ranging from various bright spots to a 4-mile-high (6.5-kilometer-high) mountain. (Another mission, the European Space Agency’s Herschel Space Observatory, spotted evidence of water vapor in 2014.)

    NASA/Dawn Spacecraft

    ESA/Herschel spacecraft


    Pluto is the most well known of the dwarf planets. Since its discovery in 1930 and until 2006, it had been classified as the ninth planet from the sun. Pluto’s orbit was so erratic, however, that at times it was closer to the sun than the eighth planet, Neptune. In 2006, with the discovery of several other rocky bodies similar in size or larger than Pluto, the IAU decided to re-classify Pluto as a dwarf planet.

    This is the most detailed view to date of the entire surface of the dwarf planet Pluto, as constructed from multiple NASA Hubble Space Telescope photographs taken from 2002 to 2003.
    Credit: NASA, ESA, and M. Buie (Southwest Research Institute)

    NASA/ESA Hubble Telescope

    Despite its small size — 0.2 percent the mass of Earth and only 10 percent the mass of Earth’s moon — Pluto’s gravity is enough to capture five moons of its own. The pairing between Pluto and its largest moon, Charon, is known as a binary system, because both objects are orbiting around a central point that is not within the mass of Pluto.

    NASA’s New Horizons mission flew by Pluto in 2015 and revealed a wealth of surprises.

    NASA/New Horizons spacecraft

    This included zones that are bereft of craters (indicating the surface is relatively young), mountains that are likely as high as 11,000 feet (3,500 meters), and even haze above the dwarf planet’s surface.




    When it was first discovered, Eris was thought to be the largest of the dwarf planets, with a mass 27 percent larger than that of Pluto and a diameter of approximately 1,400 to 1,500 miles (2,300 to 2,400 km). It was the discovery of Eris that prompted the IAU to reconsider the definition of a planet. Further observation went on to suggest that the dwarf planet is slightly smaller than Pluto.

    The orbit of Eris is very erratic, crossing that of Pluto and nearly intersecting the orbit of Neptune, but is still more than three times larger than Pluto’s orbit. It takes 557 years for Eris to orbit the sun. At its farthest point from the sun, a point that is also called its aphelion, Eris and its satellite Dysmonia travel far beyond the Kuiper Belt. The surface of Eris is likely nitrogen and methane-rich, but in a thin (1 millimeter) layer across the surface. Some scientists suggest the surface is the condensed atmosphere of Eris, which expands into gas when the dwarf planet is closer to the sun.

    Haumea and Makemake

    Haumea. Wikipedia

    An early artist’s interpretation of the dwarf planet Makemake beyond Pluto. Credit: NASA

    Haumea and Makemake are the most recently named dwarf planets in the solar system.

    Haumea is unique because of its ellipsoid shape, only just meeting the hydrostatic equilibrium criteria for dwarf planet status. The elongated shape of the dwarf planet is due to its rapid rotational spin, not a lack of mass, which is about one-third that of Pluto. The cigar-shaped dwarf planet rotates on its axis every four hours, likely a result of a collision. The odd object also hosts a red spot and a layer of crystalline ice. Finally, Haumea is the only object in the Kuiper belt other than Pluto known to host more than one moon.

    A moon was discovered around Makemake in 2016, more than a decade after the dwarf planet itself was found. Its diameter is known to be about two-thirds that of Pluto, and the newly found moon will allow for measurements of its mass. Makemake is also of value to the astronomical community, as it is another reason for the reconsideration of the definition of a planet. Its comparable mass and diameter to Pluto would grant it planet status if Pluto wasn’t also stripped of that title.

    Dwarf planets as ‘plutoids’

    Pluto, Eris, Haumea and Makemake are all known as “plutoids,” unlike the asteroidal dwarf planetoid Ceres. A plutoid is a dwarf planet with an orbit outside that of Neptune. Plutoids are sometimes also referred to as “ice dwarfs” due to their diminutive size and cold surface temperatures.

    The outer planets show evidence of interaction with plutoids. Triton, the largest moon of Neptune, is likely a captured plutoid, and it is even possible that the odd tilt of Uranus on its axis is due to a collision with a plutoid. Similarly to dwarf planets, there are potentially hundreds of plutoid objects in the solar system that have yet to be given official status.

    Additional reporting by Elizabeth Howell and Nola Taylor Redd

    See the full article here .

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