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 Post subject: Re: proxima fever!
PostPosted: Thu Feb 02, 2017 5:56 pm 
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No Conclusive Evidence for Transits of Proxima b in MOST Photometry

http://iopscience.iop.org/article/10.38 ... /3/93/meta

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The analysis of Proxima Centauri's radial velocities recently led Anglada-Escudé et al. to claim the presence of a low-mass planet orbiting the Sun's nearest star once every 11.2 days. Although the a priori probability that Proxima b transits its parent star is just 1.5%, the potential impact of such a discovery would be considerable. Independent of recent radial velocity efforts, we observed Proxima Centauri for 12.5 days in 2014 and 31 days in 2015 with the Microwave and Oscillations of Stars space telescope. We report here that we cannot make a compelling case that Proxima b transits in our precise photometric time series. Imposing an informative prior on the period and phase, we do detect a candidate signal with the expected depth. However, perturbing the phase prior across 100 evenly spaced intervals reveals one strong false positive and one weaker instance. We estimate a false-positive rate of at least a few percent and a much higher false-negative rate of 20%–40%, likely caused by the very high flare rate of Proxima Centauri. Comparing our candidate signal to HATSouth ground-based photometry reveals that the signal is somewhat, but not conclusively, disfavored (1?–2?), leading us to argue that the signal is most likely spurious. We expect that infrared photometric follow-up could more conclusively test the existence of this candidate signal, owing to the suppression of flare activity and the impressive infrared brightness of the parent star.


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 Post subject: Re: proxima fever!
PostPosted: Tue Feb 14, 2017 11:00 am 
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To Boldly Go to the Nearest Star and the Distant Past

https://www.scientificamerican.com/arti ... tant-past/

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 Post subject: Re: proxima fever!
PostPosted: Tue May 16, 2017 3:11 pm 
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The forecast for Proxima b: Wet with a chance of alien life

https://www.cnet.com/news/proxima-b-wea ... eter-nasa/

Quote:
"Our research team looked at a number of different scenarios for the planet's likely orbital configuration using a set of simulations," explained Dr. Ian Boutle, lead author of the paper. "As well as examining how the climate would behave if the planet was 'tidally-locked' (where the same side of the planet is always facing its star), we also looked at how an orbit similar to Mercury, which rotates three times on its axis for every two orbits around the sun (a 3:2 resonance), would affect the environment."

Remarkably, all the different scenarios and simulations showed that climate on Proxima b could be quite stable and support a potentially habitable world.

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 Post subject: Re: proxima fever!
PostPosted: Tue Jun 20, 2017 7:25 am 
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Red Dots: The Live Search for Terrestrial Planets around Proxima Centauri Continues

http://www.astrowatch.net/2017/06/red-d ... trial.html

Quote:
The Red Dots campaign will follow the astronomers as they use ESO’s exoplanet-hunter to look for planets around some of our nearest stellar neighbors: Proxima Centauri, Barnard's Star and Ross 154.

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 Post subject: Re: proxima fever!
PostPosted: Thu Sep 21, 2017 8:19 pm 
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Our closest star system may be home to a stolen star and planet

https://www.newscientist.com/article/21 ... nd-planet/

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 Post subject: Re: proxima fever!
PostPosted: Fri Sep 29, 2017 11:16 am 
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Project Blue: Looking for Terrestrial Worlds at Alpha Centauri

https://www.centauri-dreams.org/?p=38561

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 Post subject: Re: proxima fever!
PostPosted: Fri Nov 03, 2017 1:58 pm 
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Closest Star Proxima Centauri Has a Dust Belt, Maybe More Planets

http://www.popularmechanics.com/space/a ... i-planets/

Quote:
Proxima Centauri is already known to have one Earth-sized world around it, and now astronomers have detected dust belts that could be an indication of more.

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 Post subject: Re: proxima fever!
PostPosted: Mon Nov 20, 2017 12:48 pm 
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Planet Detectability in the Alpha Centauri System

http://astrobiology.com/2017/11/planet- ... ystem.html

Quote:
We use more than a decade of radial velocity measurements for α Cen A, B, and Proxima Centauri from HARPS, CHIRON, and UVES to identify the Msini and orbital periods of planets that could have been detected if they existed.

At each point in a mass-period grid, we sample a simulated, Keplerian signal with the precision and cadence of existing data and assess the probability that the signal could have been produced by noise alone. Existing data places detection thresholds in the classically defined habitable zones at about Msini of 53 M⊕ for α Cen A, 8.4 M⊕ for α Cen B, and 0.47 M⊕ for Proxima Centauri.

Additionally, we examine the impact of systematic errors, or "red noise" in the data. A comparison of white- and red-noise simulations highlights quasi-periodic variability in the radial velocities that may be caused by systematic errors, photospheric velocity signals, or planetary signals. For example, the red-noise simulations show a peak above white-noise simulations at the period of Proxima Centauri b. We also carry out a spectroscopic analysis of the chemical composition of the α Centauri stars.

The stars have super-solar metallicity with ratios of C/O and Mg/Si that are similar to the Sun, suggesting that any small planets in the α Cen system may be compositionally similar to our terrestrial planets. Although the small projected separation of α Cen A and B currently hampers extreme-precision radial velocity measurements, the angular separation is now increasing.

By 2019, α Cen A and B will be ideal targets for renewed Doppler planet surveys.

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 Post subject: Re: proxima fever!
PostPosted: Tue Dec 12, 2017 2:56 pm 
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Searching for the Transit of the Earth-mass Exoplanet Proxima Centauri b in Antarctica: Preliminary Result

http://iopscience.iop.org/article/10.38 ... a9b86/meta

Quote:
Proxima Centauri is known as the closest star to the Sun. Recently, radial velocity (RV) observations revealed the existence of an Earth-mass planet around it. With an orbital period of ~11 days, Proxima Centauri b is probably in the habitable zone of its host star. We undertook a photometric monitoring campaign to search for its transit, using the Bright Star Survey Telescope at the Zhongshan Station in Antarctica. A transit-like signal appearing on 2016 September 8 has been tentatively identified. Its midtime, T C = 2,457,640.1990 ± 0.0017 HJD, is consistent with the predicted ephemeris based on the RV orbit in a 1σ confidence interval. Time-correlated noise is pronounced in the light curve of Proxima Centauri, affecting the detection of transits. We develop a technique, in a Gaussian process framework, to gauge the statistical significance of a potential transit detection. The tentative transit signal reported here has a confidence level of 2.5σ. Further detection of its periodic signals is necessary to confirm the planetary transit of Proxima Centauri b. We plan to monitor Proxima Centauri in the next polar night at Dome A in Antarctica, taking advantage of continuous darkness. Kipping et al. reported two tentative transit-like signals of Proxima Centauri b observed by the Microvariability and Oscillation of Stars space telescope in 2014 and 2015. The midtransit time of our detection is 138 minutes later than that predicted by their transit ephemeris. If all of the signals are real transits, the misalignment of the epochs plausibly suggests transit timing variations of Proxima Centauri b induced by an outer planet in this system.

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 Post subject: Re: proxima fever!
PostPosted: Tue Dec 19, 2017 1:09 pm 
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What We Can Rule Out at Alpha Centauri

https://www.centauri-dreams.org/?p=38980

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 Post subject: Re: proxima fever!
PostPosted: Tue Dec 19, 2017 4:05 pm 
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No big planets at Alpha Centauri, but maybe small ones

http://earthsky.org/space/no-big-planet ... small-ones

Quote:
“Because Alpha Centauri is so close, it’s our first stop outside our solar system. There are almost certain to be small, rocky planets around Alpha Centauri A and B.”

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 Post subject: Re: proxima fever!
PostPosted: Wed Dec 20, 2017 11:12 am 
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NASA wants to explore Alpha Centauri for alien life, but doesn't know how to get there just yet

http://www.ibtimes.co.uk/nasa-wants-exp ... et-1652228

Quote:
In a report released by the AGU, the mission was broken down into six phases: accelerate out of our Solar System, survive cruise to Proxima Centauri, decelerate on approach, adjust trajectory for close encounter, acquire data, and return information to Earth.

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 Post subject: Re: proxima fever!
PostPosted: Tue Feb 27, 2018 10:21 am 
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Proxima Centauri's no good, very bad day

https://www.sciencedaily.com/releases/2 ... 103341.htm

Quote:
Astronomers have detected a massive stellar flare -- an energetic explosion of radiation -- from the closest star to our own Sun, Proxima Centauri, which occurred last March. This finding raises questions about the habitability of our Solar System's nearest exoplanetary neighbor, Proxima b, which orbits Proxima Centauri.

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 Post subject: Re: proxima fever!
PostPosted: Fri Mar 16, 2018 8:00 pm 
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No dust ring required around Proxima Centauri

https://astrobites.org/2018/03/15/proxi ... uri_flare/

Quote:
As all the excess emission is detected in a small fraction of the ACA observations, there is no significant excess quiescent emission, meaning no need for a dust belt between 1-4 AU. The authors also offer alternative explanations for Anglada’s marginal detections of a warm belt at 0.4 AU and outer belt at ~ 30 AU. The slight excess in emission detected in the ALMA observations attributed to a warm belt at 0.4 AU could be due to coronal heating of the photosphere caused by continual smaller flares, as seen in another active M dwarf, AU Mic. Slight excess emission attributed to an outer belt at 30 AU may be due to the large number of known background sources behind Proxima Centauri in the galactic plane.

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