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  • richardmitnick 11:33 am on October 8, 2020 Permalink | Reply
    Tags: "New Discoveries from Old Spacecraft", , , , , , , NASA Voyager 1 and 2 in interstellar space   

    From AAS NOVA: “New Discoveries from Old Spacecraft” 

    AASNOVA

    From AAS NOVA

    7 October 2020
    Susanna Kohler

    1
    This illustration shows NASA’s Voyager 1 and Voyager 2 probes outside of the heliosphere, the protective bubble created by the Sun around our solar system. Credit: NASA/JPL-Caltech.

    In 1977, two space probes were launched from Earth, flung out toward the farthest reaches of our solar system. Now, 43 years later, Voyager 1 and Voyager 2 are journeying through interstellar space — and they’re still providing new insights.

    NASA/Voyager 1.

    NASA/Voyager 2.

    Voyaging to the Outer Edge

    The original mission of the Voyager spacecraft was to study the giant planets in our outer solar system. But across 43 years and three mission extensions, these little probes have gone on to do so much more — most recently crossing out of the heliosphere and providing our first up-close look at interstellar space.

    NASA Heliosphere.

    What’s the heliosphere? As the solar wind streams from the Sun, it carries magnetic fields outward, inflating a bubble around the solar system that separates us from the surrounding interstellar medium (ISM). As the Sun orbits through the galaxy, the heliosphere is compressed on one side and elongated on the other, forming a blunt “nose” and a streaming “tail”.

    Into the Unknown

    When Voyagers 1 and 2 were launched, they were sent in slightly different directions — so they’re now exploring two different regions of the interface between the heliosphere and the interstellar medium. In 2012, Voyager 1 crossed the boundary of the heliosphere on one side of the nose, at a distance of ~122 au from the Sun. Voyager 2 followed suit in 2018, crossing the other side of the nose at a distance of ~119 au.

    Now, both spacecraft are traveling through the very local ISM beyond the heliosphere. But despite their distance (the one-way light travel time to Voyager 1 is ~21 hours!), the probes are still reporting back data — including from the Plasma Wave Science (PWS) instrument on each craft, which uses the long, V-shaped pair of antennae to measure oscillations in the surrounding plasma. From these oscillations, we can infer the electron density of the ISM that the Voyager spacecraft are traveling through.

    Denser and Denser

    In a new publication, University of Iowa scientists William Kurth and Donald Gurnett report the latest PWS measurement from Voyager 2, which indicates that the electron density of the ISM is currently increasing as the probe travels away from the Sun. This discovery is neatly consistent with the data from Voyager 1, which has also been reporting an increasing radial density gradient since crossing the boundary of the heliosphere and entering interstellar space.

    3
    Electron density vs. radial distance from the Sun, as measured by the Voyager 1 (black) and Voyager 2 (red) spacecraft. The radial density gradient in the ISM can be seen in the data from both probes at distances above ~120 au. Credit: Kurth & Gurnett 2020.

    Voyagers 1 and 2 have trajectories that differ by 67° in latitude and 43° in longitude — so with the new Voyager 2 data published by Kurth and Gurnett, we now have confirmation that the radial density gradient first measured by Voyager 1 is a large-scale feature around the heliospheric nose.

    Still More to Learn

    What’s causing the gradient? Two theories have been put forward:

    the interaction of the solar wind with the very local ISM creates a pile-up region outside of the heliosphere, or
    draping of magnetic field lines over the outer boundary of the heliosphere depletes the plasma just inside the heliosphere.

    We’ll potentially be able to differentiate between these two models once we have density measurements from even farther out in the ISM — so we’ll have to see if the Voyager probes last long enough to provide them!

    Citation

    “Observations of a Radial Density Gradient in the Very Local Interstellar Medium by Voyager 2,” W. S. Kurth and D. A. Gurnett 2020 ApJL 900 L1.
    https://iopscience.iop.org/article/10.3847/2041-8213/abae58

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    1

    AAS Mission and Vision Statement

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

     
  • richardmitnick 11:45 am on December 23, 2018 Permalink | Reply
    Tags: , , , Beyond the influence of the solar wind, , NASA Deep Space Network tracks Voyager spacecraft, NASA Voyager 1 and 2 in interstellar space, Voyager 2's plasma instrument will make the first direct measurements of the rarified plasma that surrounds our solar system—a substance that could tell us about the supernova blasts that seeded muc   

    From Popular Science: “Voyager 2 can finally probe the rarified plasma surrounding our solar system” 

    popsci-bloc

    From Popular Science

    It’s now one of two working spacecraft in interstellar space.

    December 10, 2018
    Charlie Wood

    1
    Voyager 2 has joined Voyager 1 beyond the influence of the solar wind. NASA/JPL-Caltech

    NASA/Voyager 1

    NASA/Voyager 2

    Voyager 2, the little spacecraft that could, continues to hurtle outward into the universe, moving around 10 miles away from the sun every second. Those miles have added up over the course of 41 years, taking it past Jupiter, Saturn, Uranus, and Neptune. On November 5 it finally joined its sibling Voyager 1 in the unexplored reaches of interstellar space.

    “I think we’re all happy and relieved that the Voyager probes have both operated long enough to make it past this milestone,” said Suzanne Dodd, Voyager project manager at NASA’s Jet Propulsion Laboratory in a press release. “This is what we’ve all been waiting for.”

    Voyager 2 is now more than 11 billion miles from the sun—about 122 times farther than Earth is from our star. Despite traveling at the speed of light, communications from the probe take more than 16 hours to reach the colossal antennas of the Deep Space Network, which listens for the faint pings from California, Spain, and Australia.

    NASA Deep Space Network dish, Goldstone, CA, USA

    NASA Canberra, AU, Deep Space Network

    NASA Deep Space Network Madrid Spain

    The announcement marks the second time in history a functioning spacecraft has left the heliosphere—the bubble inflated by the outflow of solar wind from the sun—after Voyager 1’s exit in 2012. The presence of solar wind defines the difference between interplanetary space, which is dominated by the sun’s influence, and the space between stars, which features a sparse mix of dust, gas, and cosmic rays. Pioneer 10, launched in 1972 to Jupiter has flown even farther than Voyager 2 and could conceivably have passed the boundary as well, but the spacecraft powered down in 2003 and can’t send back measurements.

    NASA Pioneer 10

    The Voyager team has been watching the machine’s remaining instruments closely as they registered an uptick in cosmic rays in recent months. The charged heliosphere pushes out and repels most of the incoming particles, so more rays hinted that Voyager 2 was approaching the boundary. Conclusive proof of the November 5 crossing arrived in three forms: the uptick of cosmic rays became a spike, the number of solar wind particles from the sun plummeted, and the magnetic field jumped in intensity as the two winds clashed.

    “There are two winds pushing on each other, said John Richardson, the principal investigator for the probe’s Plasma Science Instrument at the American Geophysical Union’s fall meeting in Washington today. “The solar wind pushing out and the interstellar wind pushing in.”

    But entering interstellar space does not mean that the spacecraft has left the solar system, Voyager’s project scientist Ed Stone emphasized. The solar system is the collection of all the rocks and iceballs captured by the sun’s gravity, which includes many comets and frozen bodies in the cosmic region known as the Oort cloud.

    Oort Cloud, The layout of the solar system, including the Oort Cloud, on a logarithmic scale. Credit: NASA, Universe Today

    Oort Cloud NASA

    He expects the Voyager spacecraft will enter this area in about 300 years, and remain there for tens of thousands of years.

    Researchers are especially excited about Voyager 2’s progress because it still has a device capable of measuring the plasma of its surroundings, while Voyager 1’s plasma instrument failed in 1980. Voyager 2 will use this tool to make the first direct measurements of the rarified plasma that surrounds our solar system—a substance that could tell us about the supernova blasts that seeded much of the material in our cosmic neighborhood.

    In the meantime, both crafts are already teaching researchers about the protective bubble the sun blows around the planets. Measurements from Voyager 1’s exit showed that the boundary stops about 70 percent of potentially harmful cosmic rays from entering the inner solar system at all, much less reaching Earth. The heliosphere inflates as the sun gets more active, and probably doesn’t have a uniform shape, so getting two data points at different locations and times has provided crucial details to guide current and upcoming surveys that aim to map out the whole bubble with indirect observations. “One of the great things about Voyager is that it keeps surprising us,” Stone said. “That means there’s a lot to learn.”

    And both machines should continue chugging along for at least a few more years. As they battle waning power and the freezing chill of deep space—Voyager 2 currently runs at about 37 degrees F, Dodd said at the AGU meeting, perilously close to its fuel’s freezing point—the team will face hard choices about which instruments to prioritize for the most valuable scientific data. Nevertheless, she’s optimistic they’ll fly for at least five more years, perhaps ten.

    “Both spacecraft are very healthy if you consider them as senior citizens,” she said.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

     
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