- 2993 - PULSARS - are used to find Dark Matter? - Pulsars can be used to measure tiny changes of acceleration within the Milky Way, scanning internally for Dark Matter and Dark Energy.
---------------------- 2993 - PULSARS - are used to find Dark Matter?
- As our Sun moves along its orbit in the Milky Way, it is gravitationally tugged by nearby stars, nebulae, and other masses. Our galaxy is not a uniform distribution of mass, and our Sun experiences small accelerations in addition to its overall orbital motion. Measuring those small tugs has been nearly impossible.
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- To get to the precision needed the focus is on “binary pulsars“. These are pulsars that have an orbiting companion. Pulsars emit bursts of radio light at regular intervals. The pulses are so regular they can serve as a kind of celestial clock.
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- As a binary pulsar orbits its companion, the timing of the pulsars varies slightly as the signal is Doppler shifted by the motion of the pulsar relative to us. By measuring the timing shift, you can calculate the orbit and the acceleration of the pulsars.
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- After calculating the relative motion of 14 pulsars, calculations were made of their accelerations relative to the solar system. These accelerations are extremely tiny but from these accelerations astronomers have measured the “mass density” within the plane of the Milky Way.
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- Stars don’t orbit the galaxy in simple circles. Instead, their motion bobs up and down through the galactic plane as the mass in the plane pulls them gravitationally. The pulsars observed by the team also do this. By measuring their accelerations the team could determine how strongly the galaxy pulls on them, and thus the mass within the galaxy.
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- This work is important because it could help us understand the distribution of dark matter within our galaxy. We know that most of our galaxy’s dark matter is distributed in a halo surrounding the galaxy, but if we can determine how much dark matter is in the galactic plane it will help us understand how dark matter clumps together within a galaxy.
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- Knowing this distribution could also help us understand how dark energy expands the universe. One of the things this initial study found was that mass within the galactic plane is not evenly distributed, which could be a dark matter signal.
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- It is well known that the expansion of the universe is accelerating due to a mysterious “dark energy“. Within galaxies, stars also experience an acceleration, though this is due to some combination of dark matter and the stellar density.
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- Astronomers have made the first direct measurement of the average acceleration taking place within our home galaxy, the Milky Way. They used pulsar data to clock the radial and vertical accelerations of stars within and outside of the galactic plane. Based on these new high-precision measurements and the known amount of visible matter in the galaxy, researchers were then able to calculate the Milky Way’s dark matter.
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- This analysis not only gives the first measurement of the tiny accelerations experienced by stars in the galaxy, but also opens up the possibility of extending this work to understand the nature of dark matter, and ultimately dark energy on larger scales.
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- Stars hurtle through the galaxy at hundreds of kilometers per second, yet this study indicates that the change in their velocities is occurring at a few centimeters per second.
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- To detect this subtle motion the research team relied on the ultra-precise time-keeping ability of pulsars that are widely distributed throughout the galactic plane and the halo which is a diffuse spherical region that surrounds the galaxy.
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- By exploiting the unique properties of pulsars, astronomers are able to measure very small accelerations in the galaxy. Extending outwards approximately 300,000 light years from the galactic center, the halo may provide important hints to understanding dark matter, which accounts for about 90 percent of the galaxy’s mass and is highly concentrated above and below the star-dense galactic plane.
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- Stellar motion in this particular region can be influenced by dark matter. While previous studies assumed a state of galactic equilibrium to calculate average mass density, this research is based on the natural, non-equilibrium state of the galaxy.
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- An analogy to this would be the difference between the surface of a pond before and after a stone is tossed in. By accounting for the “ripples” the team was able to obtain a more accurate picture of reality. Though in this case, rather than stones, the Milky Way is influenced by a turbulent history of galactic mergers and continues to be perturbed by external dwarf galaxies like the Small and Large Magellanic Clouds.
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- As a result, stars do not have flat orbits and tend to follow a path similar to that of a warped vinyl record, crossing above and below the galactic plane.
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- The accelerations measured are directly caused by the gravitational forces from the matter in the galaxy, both visible and dark, and thereby provide a new and promising window on the distribution and the composition of the matter in the galaxy and the universe.
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- While a direct picture of our home galaxy, similar to the ones of Earth taken by the Apollo astronauts, is not yet possible, this study has provided essential new details to help envision the dynamic organization of the galaxy from within.
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----------------------------------- Other reviews about Pulsars
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- 2803 - PULSARS - Magnetars, stars behaving badly? Pulsars and magnetars are stars behaving badly. But, they are still following the laws of physics. These are Neutron stars. When stars get so big, their gravity gets so intense, the electrons collapse into the nucleus of protons and the star’s core made only of neutrons becomes a “Neutron Star” only 12 miles in diameter.
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- 2681 - PULSARS - rotating neutron stars? Neutron Stars can spin! Our own star, the Sun, spins. Rather slowly, one rotation takes 25 days. This is the story about PSR J17482446 whose name will be referred to as Neutron Star henceforth. This Neutron Star is located in a Globular Cluster of stars in the Constellation Sagittarius the Archer (the “teapot” in the southern night sky). It is 18,000 lightyears away. This star is spinning at 716 rotations per second.
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- 2659 - PULSARS - rotating Neutron Stars? - Pulsars are rapidly rotating, highly magnetic compact stars. The rotating magnetic field of a pulsar acts as a generator, accelerating energetic charged particles that then stream along the field lines.
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- 2602 - PULSAR - spinning Neutron Star? - Pulsars were discovered more than 50 years ago as beacons of stars that have collapsed into dense cores, behaving unlike anything we see on Earth. For decades, scientists have been studying pulsars in the hopes of getting a better understanding of their inner workings.
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- 1897 - The mysterious Neutron Stars, Pulsars, and Quasars create radio bursts of energy that astronomers are still trying to explain.
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- 1431 - Pulsars are Nature’s precision clocks that may help us discover gravity waves. Pulsars are super dense Neutron Stars. They are the remnants of a massive star that has exploded as a supernova. A Neutron Star will have more that one Solar Mass of weight compressed into a volume the size of city of San Francisco. A larger mass star compressed to greater density would collapse into a Blackhole.
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- 1396 - High School Students Discover Pulsar. Some high school students in Kentucky and Virginia discovered a Millisecond Pulsar. They were part of project called the Pulsar Search Collaboratory. The students were trained by astronomers on how to use the Green Bank Telescope. After 300 hours of observing data the students discovered 4 Pulsars and one Millisecond Pulsar
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- 1376 - How Can Pulsars Have Planets? The first planets discovered in 1993 were not orbiting a Sun-like star but a Neutron Star, a Pulsar. When a massive star goes supernova the explosion is expected to evaporate any existing solar system. How do we explain Pulsar Planets?
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- 1327 - Neutron Stars - The surface is solid and harder that a diamond, 50 trillion times denser than solid lead. Its magnetic field is a trillion times more intense than that of our Sun.
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- 1273 - Neutron Star mergers.
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- 1192 - The new zoo of Pulsars.
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- 642 - Neutron Stars, Pulsars, and Magnetars.
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- 861 - Cannon Ball Stars
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- 625 - Neutron Stars.
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- 381 - Stars grow old.
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January 22, 2021 PULSARS -to find Dark Matter? 2993
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