5/8/2024 0 Comments Nasa firmament picturesDan Baker, director of the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder, coined this lower limit the “impenetrable barrier” and speculates that if there were no human VLF transmissions, the boundary would likely stretch closer to Earth. The probes have noticed an interesting coincidence - the outward extent of the VLF bubble corresponds almost exactly to the inner edge of the Van Allen radiation belts, a layer of charged particles held in place by Earth’s magnetic fields. This bubble is even seen by spacecraft high above Earth’s surface, such as NASA’s Van Allen Probes, which study electrons and ions in the near-Earth environment. While these waves are intended for communications below the surface, they also extend out beyond our atmosphere, shrouding Earth in a VLF bubble. VLF signals are transmitted from ground stations at huge powers to communicate with submarines deep in the ocean. “A number of experiments and observations have figured out that, under the right conditions, radio communications signals in the VLF frequency range can in fact affect the properties of the high-energy radiation environment around the Earth,” said Phil Erickson, assistant director at the MIT Haystack Observatory, Westford, Massachusetts. Their observations could help explain how clusters like NGC 6544 change over time.Credits: NASA’s Goddard Space Flight Center/Genna Dubersteinĭownload this video in HD formats from NASA Goddard’s Scientific Visualization Studio Instead of matching up sources to a pulsar, however, astronomers used Hubble to search for the counterparts of faint X-ray sources. The second observation which contributed data to this image was also designed to find the visible counterparts of objects detected at other electromagnetic wavelengths. This pulsar rotates particularly quickly, and astronomers turned to Hubble to help determine how this object evolved in NGC 6544. A pulsar is the rapidly spinning remnant of a dead star, emitting twin beams of electromagnetic radiation like a vast astronomical lighthouse. ![]() The first observation was designed to find a visible counterpart to the radio pulsar discovered in NGC 6544. This image of NGC 6544 combines data from two of Hubble’s instruments, the Advanced Camera for Surveys and Wide Field Camera 3, as well as two separate astronomical observations. This cluster of tightly bound stars lies more than 8,000 light-years from Earth and is, like all globular clusters, a densely populated region of tens of thousands of stars. The teeming stars of the globular cluster NGC 6544 glisten in this image from the Hubble Space Telescope. To zoom in to even more detail, download a full-sized, high-resolution, 288-megapixel image of this large mosaic created through multiple Hubble observations. Located in the Large Magellanic Cloud, N44 spans about 1,000 light-years and is about 170,000 light-years away from Earth. As the ionized gas begins to cool from its higher-energy state to a lower-energy state, it emits energy in the form of light, causing the nebula to glow. N44 is an emission nebula, which means its gas has been energized, or ionized, by the radiation of nearby stars. ![]() The deep blue area at about 5 o’clock around the superbubble is one of the hottest regions of the nebula and the area of the most intense star formation. Another possibility, since the nebula is filled with massive stars that would expire in titanic explosions, is that the expanding shells of old supernovae sculpted the cosmic cavern.Īstronomers have found one supernova remnant in the vicinity of the superbubble and identified an approximately 5 million year difference in age between stars within and at the rim of the superbubble, indicating multiple, chain-reaction star-forming events. Stellar winds expelled by massive stars in the bubble's interior may have driven away the gas, but this is inconsistent with measured wind velocities in the bubble. The hole is about 250 light-years wide and its presence is still something of a mystery. One of its most distinctive features, however, is the dark, starry gap called a “superbubble,” visible in this Hubble Space Telescope image in the upper central region. N44 is a complex nebula filled with glowing hydrogen gas, dark lanes of dust, massive stars, and many populations of stars of different ages.
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