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Exoplanet Discoveries, discussion of the latest finds
Mongo
post Feb 28 2017, 08:21 PM
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Towards Detection of Exoplanetary Rings Via Transit Photometry: Methodology and a Possible Candidate

Abstract: Detection of a planetary ring of exoplanets remains as one of the most attractive but challenging goals in the field. We present a methodology of a systematic search for exoplanetary rings via transit photometry of long-period planets. The methodology relies on a precise integration scheme we develop to compute a transit light curve of a ringed planet. We apply the methodology to 89 long-period planet candidates from the Kepler data so as to estimate, and/or set upper limits on, the parameters of possible rings. While a majority of our samples do not have a sufficiently good signal-to-noise ratio for meaningful constraints on ring parameters, we find that six systems with a higher signal-to-noise ratio are inconsistent with the presence of a ring larger than 1.5 times the planetary radius assuming a grazing orbit and a tilted ring. Furthermore, we identify five preliminary candidate systems whose light curves exhibit ring-like features. After removing four false positives due to the contamination from nearby stars, we identify KIC 10403228 as a reasonable candidate for a ringed planet. A systematic parameter fit of its light curve with a ringed planet model indicates two possible solutions corresponding to a Saturn-like planet with a tilted ring. There also remain other two possible scenarios accounting for the data; a circumstellar disk and a hierarchical triple. Due to large uncertain factors, we cannot choose one specific model among the three.
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Explorer1
post Mar 1 2017, 12:17 AM
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Very cool; reminds me of J1407 ( https://en.wikipedia.org/wiki/1SWASP_J140747.93-394542.6 ).
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marsbug
post Mar 8 2017, 02:47 AM
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Somehow I'd mised that - a ring system with the mass of Earth, and 0.6 A.U. radius. Incredible!


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TheAnt
post Mar 19 2017, 01:29 PM
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Of minor importance perhaps, yet more observations have revealed that Trappist 1h orbit the central star each 18.764 days, a value near what what predicted.
The radius turned out to be 0.715, while the calculated temperature at 169 K would make it a very cold world, which again is in line with predictions.

A terrestrial-sized exoplanet at the snow line of TRAPPIST-1

Some datasets seen on Astrobiology web

And a Youtube film where 'Universe sandbox' is used, even though it's probably not a fully reliable model.I think he get quite close to the mark there.
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Mongo
post Apr 3 2017, 01:25 AM
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A revolution is brewing: observations of TRAPPIST-1 exoplanetary system fosters a new biomarker

QUOTE
The recent discovery of seven potentially habitable Earth-size planets around the ultra-cool star TRAPPIST-1 has further fueled the hunt for extraterrestrial life. Current methods focus on closely monitoring the host star to look for biomarkers in the transmission signature of exoplanet's atmosphere. However, the outcome of these methods remain uncertain and difficult to disentangle with abiotic alternatives. Recent exoplanet direct imaging observations by THIRSTY, an ultra-high contrast coronagraph located in La Trappe (France), lead us to propose a universal and unambiguous habitability criterion which we directly demonstrate for the TRAPPIST-1 system. Within this new framework, we find that TRAPPIST-1g possesses the first unambiguously habitable environment in our galaxy, with a liquid water percentage that could be as large as ∼ 90 %. Our calculations hinge on a new set of biomarkers, CO2 and CxH2(x+1)O (liquid and gaseous), that could cover up to ∼ 10 % of the planetary surface and atmosphere. THIRSTY and TRAPPIST recent observations accompanied by our new, unbiased habitability criterion may quench our thirst for the search for extraterrestrial life. However, the search for intelligence must continue within and beyond our Solar System.


Please note what day it is! tongue.gif
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JRehling
post Apr 3 2017, 01:51 AM
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QUOTE (Mongo @ Apr 2 2017, 06:25 PM) *
Please note what day it is! tongue.gif


Also note that one of the authors is named Keg-Beer and the instrument is named THIRSTY, the star is named TRAPPIST (i.e., beer brewing monks), the title includes "brewing" and the chemical formula includes alcohol.

They've discovered extraterrestrial beer.
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Ron Hobbs
post Apr 3 2017, 02:50 AM
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And did you notice this was published in the "Journal of Astrobrewology"?

"However, the search for intelligence must continue within and beyond our Solar System."

Amen
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JRehling
post Apr 13 2017, 05:47 AM
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After that April Fools joke… here's an actual result about a Super Earth atmosphere. This is an exciting result, not only for the case of this one planet, and the general case of Super Earth atmospheres, but for the development of the technique:

http://www.blastr.com/2017-4-11/astronomer...t-whats-it-made

I'd point out that the minimal radius seen in any of the filters is not necessarily the surface – it could be the level of cloud tops, in which case, we're learning about the composition of the atmosphere above the cloud tops.

I think a successful application of this technique is a nudge in the direction of favoring red dwarf systems over sunlike star systems in the contest for funding / further research. Of course, both merit interest, but this technique is unlikely to work for many planets in the habitable zone of nearby sunlike stars.
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tanjent
post Apr 13 2017, 02:55 PM
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" it’s roughly Earth-sized, and has slightly less gravity than Earth (given its mass of about 1.6 times Earth’s, it has a surface gravity about 0.8 of ours)"

I'm no physicist, Phil, but isn't there a typo here somewhere? It would seem to make more sense if it had Earth's mass, and a diameter 1.6 times Earth's.
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scalbers
post Apr 13 2017, 04:26 PM
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I wonder what the limits of this technique are with more narrowband filters and/or high resolution spectroscopy?


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JRehling
post Apr 14 2017, 02:09 AM
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Surface gravity = m/r^2 (units in terms of Earth).

If m=1.6 and r=1.4, then g indeed is 0.8 of Earth's (1.6 / 1.4•1.4). The escape velocity, which is more relevant, would be about 0.9 of Earth's.

However, the errors in the measurements probably swamp the relevance of exact determinations of these things, and if we're concerned with the ability to hold an atmosphere, other, currently unmeasurable, factors would also be important.
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JRehling
post Apr 14 2017, 02:36 AM
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Steve, I think the potential for this technique to be applied to produce finer understanding of transiting exoplanets' spectroscopic properties indicates certain possibilities for improvement, but they are limited. One of the limitations will be noise from the star. If the star dims a bit due to its own variability, we can't distinguish that from the effects of the planet's atmosphere. We can partially make up for this by making more observations, but improving SNR with more observations only goes so far. Interestingly, this problem can't be fixed with a bigger, better light bucket.

I could dive back into the Kepler data with which I was more familiar a few years ago, but the Catch-22 here seems to be that red dwarfs provide the vast majority of transiting HZ exoplanets, but they are generally more variable than sunlike stars. On the other hand, planets in the HZ of a red dwarf have a short orbital period so we can increase the number of observations more quickly.

I don't see why, in principle, we can't achieve arbitrarily good measurements of an exoplanet's spectrum with a very large number of observations. Looking down the road, we might want to build farms of multiple light buckets scanning exoplanets all the time.
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TheAnt
post Nov 3 2017, 05:17 PM
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ALMA discover dust belt, 2 "rings" (=asteroid belts?) and possible glimpse of a Saturn size planet at Proxima Centauri.
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Gladstoner
post Nov 4 2017, 06:16 AM
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QUOTE (TheAnt @ Nov 3 2017, 12:17 PM) *
ALMA discover dust belt, 2 rings, and possible glimpse of a Saturn size planet at Proxima Centauri.


FWIW, the 45-degree inclination of the dust rings would indicate that Proxima b has a mass of 1.8 earths, assuming they are all coplanar.
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