Or, maybe, we envision intercepting a message from an advanced culture in one of our radio telescopes. MY BAD! Methinks their comment suggesting CaCO3 is criminally unfounded speculation. ), An earlier paper on the star and the debris disk here: http://www.astro.keele.ac.uk/jkt/pubs/2007MNRAS.380L..35G.pdf. You are actually asking about 2 different things so I will answer for each of them. So if we were to take the Earth and we were to slice it in half you would see that it has an iron metal core surrounded by a rocky exterior. More likely than not, it’s going to come as a nuanced signature that may not be immediately recognizable. Robyn Williams: Ali, I'll take that as a surprise. I can’t find an estimate of the age of the star in the main sequence, which would be interesting to compare to Earth. We may be looking, Melis and Dufour suggest, at calcium carbonate (CaCO3), a mineral widely found in shelled marine organisms here on Earth. What happens to a galaxy when a black hole is formed within it? Meet Ed Young and Alexandra Doyle. has this white dwarf been observed for transits? The force of gravity is what creates it's high density (think mass of the sun compressed into the volume of the Earth). Robyn Williams: We begin with stars. White dwarf stars are the remains of stars like the Sun — this one was once a few times the Sun’s mass — that have gone through their red giant phase and expelled all their outer material. (The amount of carbon is suspicious. MY OPINION IS: What we are LIKELY seeing are the REMAINS of Calcium Carbonate AND Silicon Carbide. They are tens of thousands of times more oxidised than one might have predicted. So, for instance, people hypothesise that when our sun evolves into a white dwarf, that it will expand and gobble up Mercury and Venus and maybe even the Earth. So these are all very important things, and we are nibbling away at things that might be important in terms of habitability as well. If its location gives more info (say, being part of a cluster), I dunno. A “Stardust”-like sample and return mission to Enceladus has been proposed, and if we can retrieve A DECENT AMOUNT OF CARBON, we should be able to determine the c12/c13 ratio. The technique used for these observations alone is fascinating enough, but the possibility that we are observing calcium carbonate delightfully suggestive. Robyn Williams: Amongst all that, how are you able to discern chemically what's going on? If you think of a spinning figure skater bringing their arms in causes them to speed up rotation, now apply that on a massive scale and you can end up with a rotating neutron star. These bodies are within 600 light years of Earth. Where a star ends up at the end of its life depends on the mass it was born with. And Ed has collaborated with the astronomers on this Polluted White Dwarf Project, and so I get to straddle the bounds of geology and geochemistry that I know and also learn all of the astronomy that I need to do this project. CaCO3 would result in “large amounts of carbon, Ca, and oxygen”, instead, or not? Image (click to enlarge): Artist’s impression of the surface of the massive, planet-like body being devoured by the white dwarf SDSSJ1043+0855. And even if we have found it, we may not be able to determine what that signature really means for a while. A biogenic process would almost certainly produce a different from a non-biogenic process. With white dwarfs. White Dwarfs Where do White Dwarfs Come From? The study asserts that the atmospheric composition of Earth-like planets orbiting white dwarfs could be quickly and precisely retrieved with the James Webb Space Telescope, to be launched in late 2021. KEEP IN MIND: Calcium Carbonate(AND Calcium Dicarbonate) were ALSO detected in the plumes of Enceladus, but no far-out fantastical claims of multi-cellular sea-life came out of THAT detection. Credit: A. Hara/C. More likely than not, it’s going to come as a nuanced signature that may not be immediately recognizable.”. EXCITING TIMES! The very first putative biosignature (apart from a martian paper)! - The white dwarfs are residues of faded stars. White dwarf stars are the remains of stars like the Sun — this one was once a few times the Sun’s mass — that have gone through their red giant phase and expelled all their outer material. The presentation is Melis and Dufour, “The Surface of a Limestone-Rich World?” American Astronomical Society 20 June 2016, AAS Meeting #228, id.#201.03 (abstract). And so if an asteroid comes too close to the white dwarf, the white dwarf's immense gravity that Ed was speaking of will shred it into a debris disc. Edward Young: Because of that immense gravity that I mentioned, all those heavy elements like magnesium, iron, silicon, oxygen, they should sink rather rapidly out of sight into the star. So far we can say that most of these things look oxidised, but we can't say that that really means that most rocks everywhere are oxidised but that's the plan. Normally, the best way to do that would be to use radial velocity observations to discern the object’s mass and thereby its potential composition and nature. If the latter, most likely we are seeing CaO, SiC, and SiO2, maybe elemental carbon, also. If the progenitor star really was ‘a few times the sun’s mass’, then its main sequence lifetime would have been fairly short – surely too short for any life to develop? When people think about finding extra-terrestrial life, they think about Hollywood dramatizations.

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