Sundog Posted September 30, 2012 Report Share Posted September 30, 2012 Re: More space news! I think it portends the fluttering of astronomers. Quote Link to comment Share on other sites More sharing options...
Cancer Posted October 1, 2012 Report Share Posted October 1, 2012 Re: More space news! I forget' date=' do these portend plagues, or earthquakes, or war? Or is it more of a general-misfortune kind of omen?[/quote'] Often they portend PR disasters for astronomers when the comet doesn't come anywhere close to living up to its advance billing. It's been almost fifty years since the last drastic case of that: does anyone else here remember the early fuss over Comet Kohoutek? That was such a wipe-out PR-wise that when the quite spectacular Comet West came by a couple years later no one said anything until it was just about over. Quote Link to comment Share on other sites More sharing options...
Cancer Posted October 2, 2012 Report Share Posted October 2, 2012 Re: More space news! Curiosity finds ancient streambed Side-by-side images of old streambed rocks on Mars and Earth, to make the case for the identification of the streambed clearer. Quote Link to comment Share on other sites More sharing options...
tkdguy Posted October 3, 2012 Author Report Share Posted October 3, 2012 Re: More space news! L2 space station criticized Cooling Earth with asteroid dust Pulsar planets may leave electric trails Earth is singing like a whale Did solar shock waves stagger the solar system's formation? Quote Link to comment Share on other sites More sharing options...
Xavier Onassiss Posted October 3, 2012 Report Share Posted October 3, 2012 Re: More space news! Re-useable rockets that make powered landings. http://www.scientificamerican.com/article.cfm?id=reusable-grasshopper-rocket Quote Link to comment Share on other sites More sharing options...
Cancer Posted October 4, 2012 Report Share Posted October 4, 2012 Re: More space news! Two black holes seemingly found in M22 Quote Link to comment Share on other sites More sharing options...
Old Man Posted October 4, 2012 Report Share Posted October 4, 2012 Re: More space news! So that's where I left them! Quote Link to comment Share on other sites More sharing options...
SteveZilla Posted October 5, 2012 Report Share Posted October 5, 2012 Re: More space news! New comet discovered' date=' perhaps one of the brightest in history[/url'] AFAICT it is crossing our orbit but there is no mention of "closest approach", so I presume it poses no threat on either its inbound or outbound journeys. Quote Link to comment Share on other sites More sharing options...
Cancer Posted October 5, 2012 Report Share Posted October 5, 2012 Re: More space news! Current elements have its closest approach to Earth at 0.43 AU, which is only slightly closer than Mars. On the other hand, the smart money isn't betting on it getting that spectacular. Quote Link to comment Share on other sites More sharing options...
tkdguy Posted October 8, 2012 Author Report Share Posted October 8, 2012 Re: More space news! Dragon capsule launched to ISS Quote Link to comment Share on other sites More sharing options...
tkdguy Posted October 9, 2012 Author Report Share Posted October 9, 2012 Re: More space news! Dragon capsule launched to ISS Speaking of which... In other news, "So that's what it is!" Quote Link to comment Share on other sites More sharing options...
tkdguy Posted October 12, 2012 Author Report Share Posted October 12, 2012 Re: More space news! A diamond bigger than Earth? NEO flyby on Friday Quote Link to comment Share on other sites More sharing options...
tkdguy Posted October 12, 2012 Author Report Share Posted October 12, 2012 Re: More space news! Meteorite's black glass may reveal secrets of Mars Cookie Monster in Mercury? Quote Link to comment Share on other sites More sharing options...
SteveZilla Posted October 14, 2012 Report Share Posted October 14, 2012 Re: More space news! Supersonic skydive 'a go' on Sunday! Quote Link to comment Share on other sites More sharing options...
Cancer Posted October 15, 2012 Report Share Posted October 15, 2012 Re: More space news! A diamond bigger than Earth? Finally tracked down the tech paper on this one. 55 Cancri e is another planet in the 55 Cnc system. The host star is a G8V: sun-like, a little cooler than ours. Planet e was initially discovered in 2004, it was found in 2011 to transit, and with that information we can really nail down its mass (8.37 +/- 0.38 Earth masses) and size (r = 2.04 +/- 0.15 Earth radii). That density is really close to earth's, about 1.5% less. The orbit is pretty small, so the surface temperature is about 2500 K (there are many brown dwarfs rather cooler than that). With that data you can try to model the planet. Take the equations of state (that is, the tables of density as functions of pressure and temperature and composition) for lots of things you expect as plausible constituents of planets. You have trouble making this planet: the density is low. Most materials are compressible, so if you take Earth's composition you can't make something with that low a density. With a pure-silicate-rock composition you barely get within the uncertainty tolerances, and it seems unlikely that there's no iron-nickel metal in the core of such a planet. To accommodate any, you need to include a thick water layer. But water on top with a 2500 K temperature? No, that doesn't work either. There has been a suggestion that the host star is carbon-rich, which in this context means there's more carbon than there is oxygen in the star. (Our sun has about 2-3 times as much O than C, by count of atoms.) That's unusual but not unknown, even for main sequence stars. (Most "carbon stars" are red giants.) When that happens, that changes the chemical mix you make planets out of. In an astrophysical gas, the O and C gobble each other up and make carbon monoxide and carbon dioxide, which remain gases until rather cold temperatures, so they don't participate in making rocky planets. The remaining extra O or C becomes available to make other compounds. Usually this is oxygen, which makes minerals collectively referred to as silicates in the planetary-interiors-modeling racket. But if extra carbon is the winner, well, carbon doesn't have the reactivity with metals that oxygen does, so it's believed plausible that you would get substantial amounts of more or less pure solid carbon, and depending on temperature and pressure the most stable form of that can be diamond. So that where the diamond comes from. We know the equation of state of carbon, including diamond, and if you have a carbon-rich mixture in your planet model, then you get a planet that both easily satisfies the observational data for planetary radius for the measured mass of 55 Cnc e, AND it has a substantial carbon layer that is mostly in the diamond state. There's a lot of ifs and speculations there, and I am not entirely convinced by the published stellar composition. But if you accept it all at face value, then you get a bigger-than-earth planet with a large mass of carbon in the diamond state. Quote Link to comment Share on other sites More sharing options...
Zeropoint Posted October 15, 2012 Report Share Posted October 15, 2012 Re: More space news! How long before DeBoers blockades it? Quote Link to comment Share on other sites More sharing options...
Old Man Posted October 16, 2012 Report Share Posted October 16, 2012 Re: More space news! And my wife still wouldn't be satisfied. Quote Link to comment Share on other sites More sharing options...
tkdguy Posted October 16, 2012 Author Report Share Posted October 16, 2012 Re: More space news! Tiniest Alien Solar System Discovered Quote Link to comment Share on other sites More sharing options...
Sociotard Posted October 16, 2012 Report Share Posted October 16, 2012 Re: More space news! Closest Alien Solar System! Alpha centauri B has an Earth-sized one that is close in and hot. http://www.msnbc.msn.com/id/49439505/ns/technology_and_science-space/ Quote Link to comment Share on other sites More sharing options...
tkdguy Posted October 17, 2012 Author Report Share Posted October 17, 2012 Re: More space news! Four suns?! Now I know where to go for a suntan. Quote Link to comment Share on other sites More sharing options...
megaplayboy Posted October 17, 2012 Report Share Posted October 17, 2012 Re: More space news! Closest Alien Solar System! Alpha centauri B has an Earth-sized one that is close in and hot. http://www.msnbc.msn.com/id/49439505/ns/technology_and_science-space/ The more important question is, are there any planets inside its habitable zone? If so, then the follow up question would be, how long would it take us to send a probe there? Even at 10% of light speed, which would require a staggering amount of energy for even a 100kg probe, sending an unmanned probe to one of the nearest stars would still take over 40 years. Quote Link to comment Share on other sites More sharing options...
Cancer Posted October 17, 2012 Report Share Posted October 17, 2012 Re: More space news! Just a quick scan of the Nature paper ... (1) Man, that's noisy data. (2) The inferred orbital period is 3.2357 +/- 0.0008 days, and planet mass is 1.13 Earth's. No, that is nowhere near the habitable zone. (3) They really should find a better acronym than FAP for their critical detection number. Really really really. The Generalized Lomb-Scargle periodogram35 of the radial-velocity residuals shows two peaks at 3.236 and 0.762 days' date=' with a FAP lower than a conservative 1% limit (Fig. 4(a)).[/quote'] AFAICT they never define what the acronym stands for, even. [EDIT^2: the acronym stands for "False Alarm Probability". None of the authors is a native English speaker; most are French or Swiss, with one Portuguese thrown in. EDIT: Once long ago ... decades ago ... I remember seeing someone present a predicted apparent magnitude for a duplicate of Earth in the alpha Cen system (albeit orbiting A, not . I have almost certainly purged the notes from that talk, but I may be able to reconstruct the number. It's guaranteed to be very faint, and about 3/4 of an arc second away from a first-magnitude star. Quote Link to comment Share on other sites More sharing options...
Cancer Posted October 17, 2012 Report Share Posted October 17, 2012 Re: More space news! OK, if I've done it right, the apparent magnitude of Earth in a 1 AU orbit around alpha Cen A, at brightest, would be about +24.5. Add 1.3 to that if it's 1 AU from alpha Cen B. Those aren't impossibly faint by themselves; the difficulty, of course, is that teh Earth would be 3/4 of an arc second away from tremendously bright stars (apparent magnitudes ~0 and +1.3 for Alpha Cen A and B respectively). Kind of challenging to see. Unless, of course, on the planet there's a planet's worth of VHF/UHF radio broadcast towers pouring out FM, TV, and radar power, in which case in that frequency band the planet would be just insanely bright as a radio source. (It's not; we've looked.) Quote Link to comment Share on other sites More sharing options...
SteveZilla Posted October 18, 2012 Report Share Posted October 18, 2012 Re: More space news! 140,000 ton asteroid set to narrowly miss Earth in February may destroy SATELLITES... and it could hit us for real in 2020 Quote Link to comment Share on other sites More sharing options...
tkdguy Posted October 18, 2012 Author Report Share Posted October 18, 2012 Re: More space news! 140' date='000 ton asteroid set to narrowly miss Earth in February may destroy SATELLITES... and it could hit us for real in 2020[/url'] So the Mayans were right if you take the margin of error into account? Quote Link to comment Share on other sites More sharing options...
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