All about Astronomy Thread - Our Expanding Universe: Age, History & Other Facts

Discussion in 'Off Topic' started by Dr. AMK, Jul 27, 2017.

  1. Dr. AMK

    Dr. AMK The Strategist

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    Only 117 Years ’Til This Asteroid (Possibly) Hits Us

    [​IMG]
    Artist impression by NASA / Barcroft Media /Barcoft Media via Getty Images

    By Don Lincoln

    Chicken Little was right. In a very literal sense, the sky is falling. Not today and not tomorrow, but eventually. NASA has announced that on September 22, 2135 (which happens to be a Thursday, if you need to check your schedule), there is a small chance an asteroid a third of a mile across (named Bennu) will slam into the Earth with an impact energy equivalent to the currently deployed arsenal of US nuclear ballistic missiles.

    Needless to say, if that happens, it will definitely be a bad day for everyone.

    But, not to worry, NASA has a plan. In a theoretical exercise, a team of engineers devised a conceptual design of the Hypervelocity Asteroid Mitigation Mission for Emergency Response vehicle, or HAMMER. It is a hypothetical spacecraft that could either ram into Bennu or target it with a nuclear device, either of which it is hoped would deflect the asteroid away from Earth.
    HAMMER is not an actual NASA program, but rather an investigation into the technical challenges that would arise in building such a device. The 1998 movies “Armageddon” and “Deep Impact” were dramatizations of broadly similar efforts.

    While it is rather unlikely that Bennu will actually hit Earth, it is inevitable that eventually a similar one will. The probability of an impact is high for smaller rocks and decreases rapidly for larger asteroids.

    In 2013, a meteor about 60 feet (20 meters) across hit the Earth near Chelyabinsk in Russia. This relatively small rock still did considerable damage. It released about 30 times as much energy as the nuclear explosion at Hiroshima, blowing out glass windows and causing 1,500 people to seek medical attention.

    It was small enough that the energy was mostly dissipated in the atmosphere, although a few rocks hit Earth. At the other end of the spectrum was a meteor about 10 miles (16 kilometers) in diameter that hit the Yucatan Peninsula 65 million years ago with enough energy to wipe out the dinosaurs as a dominant form of life on Earth. This meteor left a crater about 100 miles (150 kilometers) across.

    Meteors like the Chelyabinsk one are fairly common, hitting the Earth every few years, while those on the scale of the Yucatan one happen perhaps every 100 million years or so. In between are impacts comparable to the Bennu asteroid, which are also fairly rare, perhaps once every 100,000 years.

    But even smaller meteors can cause considerable damage. And they are surprisingly common, although luckily most impacts occur over the oceans or uninhabited regions around the globe. An impact of even a modest-sized meteor could have catastrophic consequences if it were to occur over a large city. Humanity would have to intervene to avoid massive loss of life. Ideally, that intervention would be a mission like HAMMER to avoid the collision entirely.

    In the asteroid-deflection business, warning is everything. A small amount of force applied to an asteroid many years before a predicted impact can easily alter the asteroid’s orbit, while a last minute intervention could require so much force that it might well be impossible to avoid the impact.

    With that in mind, NASA set up a program whose chief executive has what could well be the coolest title of any position in any organization: Planetary Defense Officer. The Planetary Defense Coordination Office oversees studies of mitigation efforts (like HAMMER and others) but also the near Earth orbit, or NEO, observations program. The Center for NEO Studies is dedicated to watching the skies, looking for large space rocks in orbits that could intersect the Earth.

    CNEOS has discovered approximately 18,000 near-Earth objects, with nearly 1,000 of them being over a kilometer in size. Those, of course, are the most dangerous ones. The NEO search program has existed in various forms since the 1970s.

    In 1998, NASA was directed by the Congressional Committee on Science, Space and Technology to look for possible threats of asteroids larger than a kilometer. The program has become more sophisticated over the last two decades.

    There are a bunch of NEOs out there and astronomers have found perhaps 90% of those larger than a kilometer and a lesser fraction of smaller ones. Of all NEOs found, NASA’s programs were responsible for 98% of the discoveries, with other astronomers finding the others. At a very modest fraction of NASA’s overall budget, this office is the sentinel, watching and waiting, warning us of potentially serious dangers. This is an important effort and one well worth our support.

    Will Bennu hit Earth in 2135? Probably not.

    But the Earth will definitely be hit again. It’s not a matter of if, but when.

    We live in a cosmic shooting gallery and one day a bullet will head our way. And, when that fateful day comes, I very much hope that the good astronomers involved in NEO searches will have saved the day.
     
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  2. Dr. AMK

    Dr. AMK The Strategist

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    ESA: GAIA’S FIRST ASTEROID SURVEY - Tracking 14000 Asteroids In Our Solar System
     
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  3. Fishon

    Fishon I Will Close You

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  4. Dr. AMK

    Dr. AMK The Strategist

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    SPACE ODDITY - David Bowie cover - Puddles Pity Party :)
     
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  5. Dr. AMK

    Dr. AMK The Strategist

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    There are no words unbelievable
    b5303fc997d3d52e1bb35dac38149428.jpg
    This view across 24,000 light years of the Milky Way Galaxy shows over 150,000 stars!
    4627449304357688337037.jpg
     
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  6. Fishon

    Fishon I Will Close You

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  7. Dr. AMK

    Dr. AMK The Strategist

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    NASA: Gas Giant Ejected ‘Oumuamua Into Interstellar Space
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    It has been several months since ‘Oumuamua’s discovery, but scientists are still puzzling over our first interstellar visitor. We’ve determined a few important facts, like it’s not an alien spaceship and it’s sort of cigar-shaped. Bigger questions like where it started out and how it got to our solar system are still up in the air. Researchers from NASA’s Goddard Space Flight Center have used ‘Oumuamua’s composition to speculate on how it left its home system.
    It was Oct. 17 of last year when astronomers at the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1) facility spotted what they believed to be a new comet. The object we would eventually come to know as ‘Oumuamua was already rocketing out of the solar system at more than 196,000 mph (315,400 km/h). It also had an orbital eccentricity of 1.20. It was unmistakably alien to our solar system, but it didn’t look like we expected.

    Astronomers were wrong when they initially labeled ‘Oumuamua as a comet. Upon closer observation, there was no coma of evaporating ice and dust around the object. So, it was an interstellar asteroid. This unexpected revelation is what the Goddard team is considering in the new study.

    Based on what we know about planetary formation, icy comets accumulate toward the outer edge of a system like our Oort Cloud. They won’t last long toward the inner solar system because they’d just evaporate. It’s much easier to eject an object far from a star than one orbiting closer, so scientists always believed our first confirmed interstellar visitors would be comets. However, ‘Oumuamua appears to be inner solar system material. So, what gives?

    [​IMG]
    ‘Oumuamua’s path through the solar system.

    According to the Goddard team, there may be something wrong with our models of planetary formation if most interstellar objects are rocky like ‘Oumuamua. We only have a sample size of one so far, so it’s hard to know for certain.

    In the case of ‘Oumuamua, the team suggests an encounter with a gas giant is the most plausible explanation for its arrival in our neck of the galaxy. A planet the size of Jupiter would be able to fling an object like ‘Oumuamua (between 30 and 180 meters in length) out of its home system with a gravity slingshot. Scientists around the world will be on the lookout for more objects from beyond the stars. If too many of them turn out to look like ‘Oumuamua, we may have to reevaluate theories on solar system formation.
     
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  8. Dr. AMK

    Dr. AMK The Strategist

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    NASA’s incredible exoplanet-hunting telescope is about to launch
    TESS will give us a new view of our galactic neighborhood.
    [​IMG]
    An artist's illustration of TESS and a system that it might observe.
    NASA's Goddard Space Flight Center
    It’s been a hard month for space telescopes. First we learned that Kepler is running out of fuel, signaling the end of its second life as an exoplanet hunter. Then we got word that the much-anticipated James Webb Space Telescope faces yet another delay.

    But there is some good news on the horizon for astronomers, astrophysicists, planetary geologists, and people who just like learning neat things about far-away worlds. It's TESS—short for the Transiting Exoplanet Survey Satellite. If all goes well*, the new telescope will launch this week aboard a Falcon 9 rocket. It’s a relatively small satellite, but researchers have giant hopes for what it might discover. It has the potential to identify thousands of new planets, hundreds of rocky worlds like Earth, and dozens of planets hanging out in their star's habitable zone (where liquid water could exist on the surface), all within our own little corner of the galaxy.


    How it works
    “Kepler was amazing, and Kepler’s legacy is that we now know that there is a huge diversity of planets out there,” says Lisa Kaltenegger, Director of the Carl Sagan Institute at Cornell and a member of the TESS science team. Kaltenegger and her colleagues want to build on the knowledge gained from Kepler and take a closer look at some exoplanets that are hanging out around stars a little closer to home.

    TESS will systematically examine 85 percent of the sky seen from Earth, focusing on the stars visible in the northern hemisphere for one year, and the southern hemisphere for the next year. It will keep its peeping within 300 light years away from Earth. That might seem like a large distance, but to an astronomer, it’s right in our neighborhood. To put it in perspective, our galaxy is about 100,000 light years across.

    ”If you think about it, the closest star, Proxima Centauri, is about 4 light years away. We are looking at everything that is bright and close out to 300 light years, so about 100 times that distance, and there’s a huge number of stars that we can look at,” Kaltenegger says.

    Within that range, TESS will watch over 200,000 stars for evidence of planets over the course of a two-year mission, taking pictures of a segment of the sky every 30 minutes for 27 days. As with Kepler, researchers will use TESS to watch for moments when stars dim, which happens when a planet passes between the star and TESS. The dips in light can tell us a lot about a planet’s size, shape, and what it’s made of.

    “We don’t have any ships or vehicles yet to get there, but light travels the universe for free,” Kaltenegger says. “So we can do this exploration even though we don’t yet have any physical way to actually get there.”

    TESS will particularly look for planets around bright stars, much brighter than those Kepler studied. The brightness of the targets means that other, more powerful telescopes—like the forthcoming James Webb Space Telescope and ground-based instruments—will be able to look for even finer details of those planets, including their potential for life.


    Looking for life
    With TESS, researchers will find thousands of planets, take the measure of theirmasses, and observe strange stars. Some researchers, like Kaltenegger, hope that they will point toward a planet other than our own that might have life.

    “My passion is trying to figure out if we are alone in the universe, and what we need for that is planets where we can explore the air, where we get enough light to look at the atmosphere of those planets. [That means] we need planets that are close by, and that’s what TESS affords us,” Kaltenegger says.

    Kaltenegger and her colleagues can search for signs of life by watching for worlds with large amounts of unstable compounds in their atmospheres, including oxygen. Oxygen makes up a disproportionate amount of our atmosphere because it is a byproduct of many living organisms. A similar atmospheric imbalance on another world, and especially the presence of multiple gasses that don't belong together, could indicate the presence of life.

    Scientists can tell the composition of another planet’s atmosphere by looking for parts of light that vanish as the globe passes in front of its host star, and reappear when the planet has moved on. Those missing pieces correspond to particular molecules (water, oxygen, and methane, for example) in the planet's atmosphere that absorb specific parts of the light.

    TESS wouldn’t be taking those measurements, but it would point to promising candidates for more stringent examination by JWST or ground-based telescopes.

    “It will be the first time in human history that we have the technological means to answer the question ‘are we alone?'” Kaltenegger says.

    When does it launch again?
    Barring technical glitches, bad weather, or other strange and unfortunate events, TESS will launch on Monday, April 16, at 6:32 p.m. eastern.*

    • UPDATE: Looks like the technical glitch wins. SpaceX scrubbed the Monday launch so that their team could conduct additional analysis on the guidance, navigation and control systems. They are aiming for another launch attempt on Wednesday, April 18.
     
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  9. hmscott

    hmscott Notebook Nobel Laureate

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    Hubblecast 108 Light: Hubble finds most distant star (Icarus)
    HubbleESA
    Published on Apr 2, 2018
    Astronomers have used Hubble to make an incredible discovery — they have observed the most distant star ever seen. The bright blue star existed only 4.4 billion years after the Big Bang. This incredible distant star allows astronomers to learn more about the formation and evolution of stars in the early Universe.

    Meet Icarus, The Most Distant Star Ever Seen | Mach | NBC News
    NBC News
    Published on Apr 27, 2018
    Although galaxies have been observed at more than 9 billion light-years from Earth, astronomers looked at least 100 times farther to discovered Icarus, the most distant star yet.

    New, distant star discovered by U of M researchers
    KARE 11
    Published on Apr 4, 2018
    Researchers at the U of M just discovered Icarus, the farthest individual star ever seen. Its discovery was by accident. https://kare11.tv/2Iqpz87
     
    Last edited: Apr 30, 2018
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  10. hmscott

    hmscott Notebook Nobel Laureate

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    NASA Spacecraft Discovers New Magnetic Process in Turbulent Space
    space googlevesaire
    Published on May 9, 2018

    Though close to home, the space immediately around Earth is full of hidden secrets and invisible processes. In a new discovery reported in the journal Nature, scientists working with NASA’s Magnetospheric Multiscale spacecraft — MMS — have uncovered a new type of magnetic event in our near-Earth environment by using an innovative technique to squeeze extra information out of the data.

    Magnetic reconnection is one of the most important processes in the space — filled with charged particles known as plasma — around Earth. This fundamental process dissipates magnetic energy and propels charged particles, both of which contribute to a dynamic space weather system that scientists want to better understand, and even someday predict, as we do terrestrial weather. Reconnection occurs when crossed magnetic field lines snap, explosively flinging away nearby particles at high speeds. The new discovery found reconnection where it has never been seen before — in turbulent plasma.

    https://www.nasa.gov/feature/goddard/...

    https://www.nature.com/articles/s4158...
     
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