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Star Wars
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 Star WarsExplanation: In the upper left corner, surrounded by blue arms and dotted with red nebulas, is spiral galaxy M81. In the lower right corner, marked by a light central line and surrounded by red glowing gas, is irregular galaxy M82. This stunning vista shows these two mammoth galaxies locked in gravitational combat, as they have been for the past billion years. The gravity from each galaxy dramatically affects the other during each hundred-million-year pass. Last go-round, M82's gravity likely raised density waves rippling around M81, resulting in the richness of M81's spiral arms. But M81 left M82 with violent star forming regions and colliding gas clouds so energetic the galaxy glows in X-rays. This big battle is seen from Earth through the faint glow of an Integrated Flux Nebula, a little studied complex of diffuse gas and dust clouds in our Milky Way Galaxy. In a few billion years, only one galaxy will remain |
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Cosmology Lecture On Saturday, May 10, 2025 at 01:37:29 AM PDT, Alan S <dmarc-noreply@freelists.org> wrote: This article in astronomy magazine discusses some of what was talked about in Dr. Johnson's presentation tonight at the meeting. www.astronomy.com There are a lot of variables in the hubble constant. From Dr. Johnson's presentation tonight - this is an area of cosmology that will take a lot more research and study to come to any provable thesis. Al Excellent find, Alan. There is clearly something critical being overlooked. The difference between the early route (67.8) and the late route (73.2 km/second per Million parsecs), aka the “Hubble Tension,” is sufficiently large ~5 km/sec/Mpc) to cause consternation, especially given the error bars don’t overlap. Adding the error margins reduces the tension gap to 5.4-3.5=1.9 km/second/Mpc. Small, but vexing. Either one or the other (or both) are missing something. There is still so much we do not know. I think the notion we should toss the Big Bang is a bit premature, given all the evidence in support of it. Both Hubble and Einstein discovered the universe expansion, though Albert rejected the implications of his field equations for general relativity, or he would have scooped Edwin. Bell Labs discovery of the 3K CMB (2.7° Kelvin cosmic background radiation) defeated competing models of the universe. So many other bits of evidence support the model that it’s problematic to simply discard it altogether. Obviously it needs some fairly major tweaking. My view (for whatever it is worth) is that a better understanding of dark matter may well resolve the discrepancy. I remember there were two competing methods for determining stellar ages, the oldest values clustering around both 20 billion and 12 billion years, as though a person might be simultaneously both 12 years old and 20 years old. A twenty-year-old behaving like a 12 year-old, perhaps. COBE and WMAP explained why both measurements were wrong, pointing to the currently accepted age of 13.8 billion years. Granted, JWST is throwing shade (or the opposite) on that value. So there is a lot more work yet to do. The more we know, the more we realize the vast depth of our ignorance. Even discerning the nature of dark matter still leaves us completely in the dark regarding dark energy, which comprises the majority of all there is. That a LOT more research is required—we completely agree. Parsec: A parallax of one arc second. Think of it as astronomers using the diameter of Earth’s orbit as a yardstick, whereas the public is more comfortable interpreting interstellar distances in terms of Earth’s orbital circumference (years). km/sec/Mpc = kilometers per second per million parsecs. So solar system orbits are not expanding, nor the space between stars. Instead, the gulf between galactic clusters widens as time passes. So between two galaxies the distance may be shrinking, such as between Andromeda and our own Milky Way (Andromeda’s light is blue shifted—we will ultimately collide) but for every million parsecs (3.26 million light years) the average recession rate is either 67.8 or 73.2 kilometers per second. 70 km/sec is about 44 miles/second, or 157,000 miles per hour. In comparison, Voyager 1 moves away from us 11 miles per second, while light propagates at 186,300 miles per second. One slide Dr. Johnson showed the diameter of the universe as 84 million light years. That threw me for a second, until I realized he meant at the 384,000 year age of the universe where the temperature had fallen so light was no longer ionizing hydrogen, rendering the universe transparent instead of opaque. The density would have been somewhat uniform—no stars should yet have formed. That light is the light now stretched into the 2.7° K infrared wavelength we measure as the CMB. Alan knows all this—I’m just writing for the benefit of others on the list. I have included Dr. Johnson to correct any of the errors I am prone to make. Any lack of response should NOT be construed as confirmation or agreement with anything I’ve written here. Elen sila lumenn' omentielvo |
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