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Islander

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Everything posted by Islander

  1. From Wikipedia... Two spectroscopic companions have been proposed to the red supergiant star. Analysis of polarization data from 1968 through 1983 indicated a close companion with a periodic orbit of about 2.1 years. Using speckle interferometry, the team concluded that the closer of the two companions was located at 0.06″±0.01″ (≈9 AU) from the main star with a position angle of 273 degrees, an orbit that would potentially place it within the star's chromosphere. The more distant companion was estimated at 0.51″±0.01″ (≈77 AU) with a position angle of 278 degrees.[69][70] Further studies have found no evidence for these companions or have actively refuted their existence,[71] but the possibility of a close companion contributing to the overall flux has never been fully ruled out.[72] High-resolution interferometry of Betelgeuse and its vicinity, far beyond the technology of the 1980s and '90s, have not detected any companions.[16][73]
  2. Let me say it again. Betelgeuse is not a threat to Earth or life on Earth. Oh and a quote from that article: "But that doesn’t mean – contrary to scare stories in the media – that the core has collapsed, and is about to trigger a supernova. For a start, it would implode in literally a matter of seconds, and the shock wave would rip through Betelgeuse before the outer layers have a chance to fade. So if this dimming were a harbinger of doom, Betelgeuse would have self-destructed weeks ago. Betelgeuse will go supernova one day, and rival the Full Moon in brightness – but probably not for 100,000 years."
  3. None of the possible outcomes are a threat to Earth. The most likely outcome is that it will eventually return to normal brightness.
  4. Everything has to happen some time, and not all of the possibilities are happening. The scientific consensus seems to be that the dimming isn't that unusual unless it persists. Even if it does persist it's more likely that it'll return at some point. A supernova is unlikely, but in the event it happens in our lifetime, it's not a threat. It's also more likely to produce a neutron star than a black hole but again, neither are dangerous to Earth.
  5. It does sound like you're confused. If it returns to normal brightness then it'll carry on as normal, no supernova just a red supergiant star. If it continues dimming, then something new is happening but the likelihood is that the effect will be down to expulsion of material which partially obscures the star and eventually it'll brighten again. If it were to become a supernova, then it wouldn't affect us apart from being visible in daytime and eventually changing the shape of Orion forever. To become a black hole it has to undergo catastrophic gravitational collapse and that would produce a supernova. It's still not dangerous to Earth though.
  6. Two things, the net gravitational effect on Earth will be zero, and nobody can predict the exact date of a supernova occurring.
  7. No, it really isn't. The more sensationalist press might run with that but it's not mainstream scientific opinion. Red supergiants are inherently variable. Betelgeuse has dimmed somewhat but that's likely to be caused by material being expelled, again a feature of red supergiants.
  8. Seriously, Betelgeuse is too distant to affect us whatever happens to it. It's more likely that it'll brighten again and return to business as usual than become a supernova.
  9. Why would a stellar merger become a black hole? Also, where did the date pop up from? I'm really not sure what you're looking for...
  10. Better pack a waterproof and umbrella just to be on the safe side
  11. They aren't coming at us. Quote from the article: "The symmetry of the bubbles billowing above and below the galaxy suggests they were formed by an extremely energetic explosion near the supermassive black hole at the center of the Milky Way. The most likely explanation is a flare up in the black hole’s activity as it gobbled up extra nearby material and burped out other particles and radiation." Note the first statement in the quote "above and below the galaxy" not laterally and towards the arms.
  12. No. The e+9 means that the decimal point shifts 9 places to the right. As others have already said, a parsec is 3.26. light years. A Megaparsec is a million times that.
  13. It's the density that matters and the density that causes the curvature of spacetime to increase. When the star runs out of fuel, there is no longer sufficient pressure of fusion to hold the outer layers up against gravity, the star is no longer in hydrostatic equilibrium and the outer layers rapidly collapse into the core which then further collapses until the density is infinite.
  14. No. The Earth would experience the same gravitational pull as it did before the Sun collapsed (which it actually couldn't - too little mass available). It would continue to orbit normally.
  15. This is a gross oversimplification but... Remember that the mass if he star has collapsed into a point of infinite density and this causes the curvature of spacetime at the point of singularity to become infinite as well. It's this that prevents anything from escaping. Think of it this way. A photon entering the region outside the black hole's influence can travel in any direction. As it approaches the black hole, the directions of travel available to it begin to disappear until it can only head into the singularity itself. That point is defined by the event horizon.
  16. I'd use a C20 mix. I bag cement to 2 of sand and 4 of aggregate. For 1 cubic metre, you'd need 320kg cement, 640 kg sand and 1280kg of aggregate (10-20mm). Oh and about 300 litres of water. For that quantity it's worth considering a readimix delivery. I've never been impressed by the 1m3 isolated cube for a pier foundation argument. When I eventually get round to building my own, I'll just pour a 150mm thick slab for the whoe thing and build a pier from concrete blocks on top of it. ETA Oh and I'm on glacial till i.e clay with rocks in it.
  17. If you do decide to buy rather than build, I'd recommend the Davis Vantage Pro 2. I've been running one for years and apart from 2 sets of anemometer bearings, it's been faultless. There are people on the various forums (Cumulus, WXForum) that make aftermarket data loggers for interfacing to Cumulus. The initial outlay is high but the reliability compensates for that.
  18. Take the mirror out and look at a light source through the back (non-reflective) side of the mirror. That'll give you a good idea of the condition of the coating - if it appears perforated then you know it's degrading and is going to need a recoat at some point in it's future. I recommend Vacuum Coatings/Scientific Mirrors for this, they're very helpful and will work with you. However, having said that I'd give the surface a clean (with a gentle soap solution - I use a weak solution of Lux flakes for this - a rinse with clean water and a final rinse with distilled water) and carry on using it. It's not that bad at the moment and perfectly usable - you really won't notice a problem at this stage.
  19. Give Scientific Mirrors/Vacuum Coatings a ring. They're very helpful and very high quality. Here's a link to their price list: http://www.scientificmirrors.co.uk/vcsm-Aluminising.html
  20. Both for me, backed up with a decent (Tirion) star atlas
  21. Fair enough but they're still objects that have been ejected from the Earth by an impact, and then returned by gravity albeit on a short time scale. They're a record of a cataclysmic event. Mars and Moon meteorites are also produced by and are records of cataclysmic events. It depends on viewpoint I suppose.
  22. Tektites tend to be more like a glass. They're formed from the ejecta of a large impact with the high energy yield and pressure and temperatures that that implies - normal rock simply won't survive that unchanged. John mentioned Moldavites which have the appearance of a beautiful green patterned glass and are thought to originate from the Nordlinger Ries impact crater in Bavaria. I have some Indochinite tektites which have a black glassy appearance similar to weathered obsidian.
  23. We have tektites, which consist of material ejected from the Earth's surface by impactors and then returned by gravity.
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