Exoplanet Discoveries, discussion of the latest finds |
Exoplanet Discoveries, discussion of the latest finds |
Guest_PhilCo126_* |
Apr 21 2009, 11:10 AM
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Guests |
Well-known exoplanet researcher Dr Michel Mayor ( discoverer of Peg 51b with Dr Didier Queloz in 1995 ) today announced the discovery of the lightest exoplanet found so far. The planet, “e”, in the famous system Gliese 581, is only about twice the mass of our Earth. The team also refined the orbit of the planet Gliese 581 d, first discovered in 2007, placing it well within the habitable zone, where liquid water oceans could exist:
http://www.eso.org/public/outreach/press-r...9/pr-15-09.html |
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Aug 14 2016, 07:41 AM
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Merciless Robot Group: Admin Posts: 8785 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
MOD MODE: Merged topic created for this alleged Proxima planet into this topic. There is absolutely no way that liquid water could have possibly been detected on this purported planet via the espoused (ground-based) discovery method. Media reports are spinning rapidly out of control. The characterization 'Earth-like" is inherently misleading; "Earth-sized" is much more plausible and accurate.
Furthermore, this is the same team that 'discovered' Alpha Centauri Bb, which was subsequently not confirmed. All these points should produce some healthy skepticism. Bottom line is that this story is extremely speculative at this point--and therefore of extremely questionable quality as subject matter for UMSF. Discussion will be allowed using reputably sourced information, but not obvious sensationalism as seems to be the case for this thus far. This thread will be closed immediately if the discussion does not meet Forum standards. "Extraordinary claims require extraordinary evidence"- Sagan's Law -------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Aug 14 2016, 03:01 PM
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#3
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
This is indeed a good time to invoke Sagan's Law.
The notion that Proxima Centauri might have a planet is not a wild one at all – in fact, it may be nearly certain that any given red dwarf have at least one planet. The remarkable claim is about how much it might be like Earth, and those words "might" and "like" are packed full of opportunities to be vague and say nothing meaningful. Here are key statements from the Spiegel article: • The research involved in this took place at the limit of what measurements technically feasible. • The method used involved "variations in the motion of the star." The second statement is ambiguous. The Doppler method that measures radial (towards or away from Earth) movement of the star has been one of the two most productive methods for discovering exoplanets. Another method – long-discussed, but never-yet successful – has been to look at how a star wobbles side-to-side. The Doppler method works equally well for stars that are far or near, whereas the wobble method would be more successful for close stars – and Proxima Centauri is the closest – than any other. The Doppler method is also blind to planets in orbits that we see face-on, whereas the wobble method would work just fine for those… if it works for any cases at all, which is not clear. Finding Earth-mass planets has been elusive even for the Doppler method, with the smallest so far confirmed having a mass of about 3.7 mass[Earth] with an uncertainty of about 0.7. When the uncertainty in one of the best cases is 0.7 mass[Earth], it gives you an idea of the hopelessness of determining that any subsequent discovery would be very close to 1.0 mass[Earth] without very large relative uncertainty. The first statement is of paramount importance: If the results come at the limit of what is technically feasible, then they almost inherently contain uncertainty, which would mean that there could be doubt as to whether or not they detected a planet as opposed to noise, and if they did detect a planet, even if it happened to be very much Earth-sized and getting Earth-like amounts of sunlight, the measurements would have too large of an error for us to be confident about the nature of the planet yet. Given what we know in general about exoplanet occurrence, it would be surprising if Proxima Centauri didn't have some planets smaller than Neptune orbiting it, and it wouldn't be surprising if it had one about the size of Earth and getting about that much sunlight… but "not surprising" is a long way from confirmed. |
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