Christopher Posted January 10, 2017 Report Share Posted January 10, 2017 The Dec. 2016 issue of Scientific American features an article about more new discoveries about the formation of the Solar System. As the author notes, 20 years ago we had a clear and simple model of planet formation: In the course of a few hundred million years, a spinning disk of dust and gas condenses into dust bunnies, then pebbles, boulders, planetesimals and planetary embryos, that finally consolidate into planets. Thanks to studies of exoplanetary systems, accretion disks around other stars and new techniques for very precise measuring of isotopes and magnetic fields in meteorites, that stately picture is now dead. The author recounts new evidence that a lot of early planetesimals generated enough internal heat for their insides to melt, segregate and even generated their own magnetic fields. (Radioactive aluminum-26 is proposed as the chief heat source.) Along the way, it looks like the entire process of planet formation took less than 10 million years. In fact, planetesimals with liquid iron cores might have formed in only 500,000 years. The article concludes with a proposed mission to asteroid Psyche, a big nickel-iron asteroid that may be the stripped-off core of one such planetesimal. Dean Shomshak Okay, AL-26 sounds interesting. It has a half life of about 70.000 years and only cosmic radiation hitting magnesium is likely to produce more. Wich means you can use it to "Carbon Date" asteroids The relatively short halflife combined with Magnetic Fields preventing it's existence, means that AL-26 might delay the formation of planets quite a bit (if it is indeed the souce of the heating). But as a result it will not actually hinder it forever (as the magnetic fields+decay will result in stopping to exist). Quote Link to comment Share on other sites More sharing options...
tkdguy Posted January 10, 2017 Author Report Share Posted January 10, 2017 A new theory on how the moon formed Quote Link to comment Share on other sites More sharing options...
tkdguy Posted January 19, 2017 Author Report Share Posted January 19, 2017 ALMA captures images of Sun Cassini photographs Mimas Dark energy, but no dark matter? DShomshak, Netzilla and Christopher 3 Quote Link to comment Share on other sites More sharing options...
Cancer Posted January 24, 2017 Report Share Posted January 24, 2017 Something making waves on the IntarWebz now is something about a giant asteroid collision 466 million years ago. I tracked down the technical paper (here) and read it. People sifting (figuratively) meteoritic grains from rock layers of the Ordovician period (485 to 444 million years ago). The number of these chrome spinel grains (which are tough, and can withstand weathering etc. for that long and still be identifiable and countable) jumps by a factor of 100 or so at that 466 Myr ago point. Also at that time there is a real shift on the proportions of the different meteorite types in the strata. At that point in a time, suddenly a couple of types that were less common (like 22% of the meteorites found) jump so they make up approximately all (">~99%") of the meteorites found in the strata.. This makes some sense if a big collision between two asteroids of the correct composition types sprayed lots of fragments into orbits around the Sun that put them "in the way" of Earth so that they would get swept up and fall into the Earth. An extended point: When you look at main belt asteroids now, the asteroids in orbits best suited for sending pieces that will fall on Earth are not of the composition type that makes the majority of recent meteorites. Implication: recent meteorites dominantly come from a few parent asteroids that collided relatively recently and put lots of chunks into Earth-encountering orbits, and did not leave many large pieces left that you'd observe as asteroids. That is, the stuff falling on Earth at any point in time is strongly influenced by asteroid collisions that happened shortly before. This makes some sense, but definitive evidence that this is so wasn't something we had before. Irreverently: you'll get lots of Alderaan chunks falling on you for a while after the Death Star zaps Alderaan. Before and long after, not so much. Then when the rebels blow the Death Star, you'll get lots of Death Star chunks falling on you for a while; before that and long after, not so much. And so on. Quote Link to comment Share on other sites More sharing options...
Old Man Posted January 27, 2017 Report Share Posted January 27, 2017 Pluto. Cancer, DShomshak and Christopher 3 Quote Link to comment Share on other sites More sharing options...
Old Man Posted January 27, 2017 Report Share Posted January 27, 2017 Directly imaged four planet system Quote Link to comment Share on other sites More sharing options...
DShomshak Posted January 28, 2017 Report Share Posted January 28, 2017 Feb. '17 Scientific American has two space-related articles. One deals with experiments in simulating the effects of cosmic rays on the brain. Bad news: It appears they are more damaging than was previously thought, which may seriously curtail human activity in space if we can't develop better shielding or drugs to counter the effects. The other rips into the "Cosmological Inflation" hypothesis. Although the idea that the very early universe underwent a brief period of hyperspeed expansion that flattened space and homogenized the distribution of matter is often presented as settled astrophysics, the authors point out numerous flaws in the idea. In fact, terms such as "utter bilge" do not seem too strong. (Incidentally, one of the authors -- Paul J. Steinhardt -- was one of the early theorists who contributed to the hypothesis, which I think shows rare intellectual integrity. Most of us tend to hold onto our ideas to the bitter end.) Dean Shomshak Quote Link to comment Share on other sites More sharing options...
tkdguy Posted January 28, 2017 Author Report Share Posted January 28, 2017 Am I a bad person for thinking that cross-section of Pluto would make a great battle mat for wargames? Quote Link to comment Share on other sites More sharing options...
Old Man Posted January 28, 2017 Report Share Posted January 28, 2017 It has some craters already. Quote Link to comment Share on other sites More sharing options...
Asperion Posted January 28, 2017 Report Share Posted January 28, 2017 Am I a bad person for thinking that cross-section of Pluto would make a great battle mat for wargames? With the human nature to seek out a challenge no matter where it is located, even if it has to be located - I would say the answer is no. I believe that there are several people who looked at that image with the same or similar thought, myself among them. tkdguy 1 Quote Link to comment Share on other sites More sharing options...
Old Man Posted January 28, 2017 Report Share Posted January 28, 2017 I just thought it would be a nice place to hike. (You know, aside from the unimaginably frigid temps and the hard vacuum.) What annoys me is that there's no scale. Quote Link to comment Share on other sites More sharing options...
DShomshak Posted January 28, 2017 Report Share Posted January 28, 2017 I just thought, "Wow." (Okay, and then I thought, "Yes, this place definitely has active geology." But mostly just that it's a stunning view.) Dean Shomshak Quote Link to comment Share on other sites More sharing options...
Christopher Posted January 29, 2017 Report Share Posted January 29, 2017 I just thought, "Wow." (Okay, and then I thought, "Yes, this place definitely has active geology." But mostly just that it's a stunning view.) Dean Shomshak Very active geology. That "heart" shape (partialyl seen in the lower half) actually works like a cosmic lava-lamp: https://www.nasa.gov/feature/pluto-s-heart-like-a-cosmic-lava-lamp Quote Link to comment Share on other sites More sharing options...
Cancer Posted January 29, 2017 Report Share Posted January 29, 2017 It has some craters already. But only a few. I don't think anyone foresaw finding that young a surface. Quote Link to comment Share on other sites More sharing options...
Old Man Posted January 30, 2017 Report Share Posted January 30, 2017 What if the Plutonians just have better anti-asteroid defenses than we do? Quote Link to comment Share on other sites More sharing options...
Zeropoint Posted January 30, 2017 Report Share Posted January 30, 2017 It's obviously working better than the Martian defense grid; that one seems to let about half the things through. Old Man 1 Quote Link to comment Share on other sites More sharing options...
Old Man Posted January 31, 2017 Report Share Posted January 31, 2017 NASA to ... Crash World Economy Quote Link to comment Share on other sites More sharing options...
Cancer Posted January 31, 2017 Report Share Posted January 31, 2017 What if the Plutonians just have better anti-asteroid defenses than we do?That isn't a reassuring idea. Quote Link to comment Share on other sites More sharing options...
Netzilla Posted February 4, 2017 Report Share Posted February 4, 2017 http://www.iflscience.com/space/thousands-of-galaxies-on-death-row-as-they-are-stripped-of-their-gas/ tkdguy 1 Quote Link to comment Share on other sites More sharing options...
tkdguy Posted February 4, 2017 Author Report Share Posted February 4, 2017 Interesting read. Quote Link to comment Share on other sites More sharing options...
tkdguy Posted February 12, 2017 Author Report Share Posted February 12, 2017 Re: Exoplanets orbiting red dwarfs A piece of the sun Quote Link to comment Share on other sites More sharing options...
DShomshak Posted February 14, 2017 Report Share Posted February 14, 2017 The current (March 2017) issue of Discover magazine has an article about how amateur astronomers contribute to exoplanet studies. Photometers and telescopes that are within the price range for amateurs are sufficient to detect the dip in brightness from an exoplanet transit; and combining the data from many observers compensates for the lower precision of the individual measurements. This blows my mind. There's also an article about early planning and development for a Europa lander mission. Dean Shomshak pinecone and tkdguy 2 Quote Link to comment Share on other sites More sharing options...
tkdguy Posted February 17, 2017 Author Report Share Posted February 17, 2017 New space suits pinecone and Christopher 2 Quote Link to comment Share on other sites More sharing options...
Christopher Posted February 17, 2017 Report Share Posted February 17, 2017 New space suits Finally, a important step closer to the final goal: http://tvtropes.org/pmwiki/pmwiki.php/Main/LatexSpaceSuit Quote Link to comment Share on other sites More sharing options...
tkdguy Posted February 17, 2017 Author Report Share Posted February 17, 2017 NASA actually has been trying to develop a latex space suit. Proponents say it would look better than the one astronauts use today, and they usually show a young woman modeling the suit. Robert Zubrin has countered in his book How to Live on Mars that the suit won't look ats good on people who don't look like models. If you've got a beer belly, it's going to show in your space suit. Quote Link to comment Share on other sites More sharing options...
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