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Thread: Proxima Centauri b: Terrestrial or Neptunian?

  1. #31
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    Correction, that is the wrong link. Yours has 00954 in the url but it should be 00984:

    https://arxiv.org/abs/2003.00984

    "The problem with quotes on the Internet is that it is hard to verify their authenticity." — Abraham Lincoln

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  2. #32
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    Thank you for the correction, greatly appreciated.
    Do good work. —Virgil Ivan "Gus" Grissom

  3. #33
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    You’re quite welcome.

    "The problem with quotes on the Internet is that it is hard to verify their authenticity." — Abraham Lincoln

    I say there is an invisible elf in my backyard. How do you prove that I am wrong?

    The Leif Ericson Cruiser

  4. #34
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    A new paper says that the explosive eruptions from Proxima Centauri could have significant effects on the atmosphere of Proxima b, as detailed by the authors. You won't be able to breathe the air, but the planet might be warm. https://arxiv.org/abs/2003.02036
    Do good work. —Virgil Ivan "Gus" Grissom

  5. #35
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    Waiting for confirmation of Proxima c. Maybe a telescope will get it.

    https://arxiv.org/abs/2003.09305

    Expectations for the confirmation of Proxima c from a long-term radial velocity follow-up
    Mario Damasso, Fabio Del Sordo
    (Submitted on 20 Mar 2020)

    Proxima c, a candidate second planet orbiting Proxima Centauri, was detected with the radial velocity method. The announced long orbital period (5.21 +0.26/−0.22 years), and small semi-amplitude of the induced Doppler signal (1.2 ± 0.4 m/s), make this detection challenging and the target worthy of a follow-up in the next years. We intend to evaluate the impact of future data on the statistical significance of the detection through realistic simulated radial velocities to be added to the published dataset, spanning up to one orbital period of Proxima c in the time range 2019-2023. We find that the detection significance of Proxima c increases depending not only on the amount of data collected, but also on the number of instruments used, and especially on the timespan covered by the observational campaign. However, on average we do not get strong statistical evidence and we predict that, in the best-case scenario, in the next 5 years the detection of Proxima c can become significant at 4
    σ level. If instead Proxima c does not exist, the detected signal may lower its significance down to 2σ.
    Do good work. —Virgil Ivan "Gus" Grissom

  6. #36
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    https://arxiv.org/abs/2003.13106

    Orbital inclination and mass of the exoplanet candidate Proxima c
    Pierre Kervella, Frédéric Arenou, Jean Schneider
    (Submitted on 29 Mar 2020)

    We analyse the orbital parameters of the exoplanet candidate Proxima c recently discovered by Damasso et al. (2020) using a combination of its spectroscopic orbital parameters and Gaia DR2 proper motion anomaly. We obtain an orbital inclination of i = 152 ± 14° for the prograde solution, corresponding to a planet mass of mc=12 +12−5 M⊕, comparable to Uranus or Neptune. While the derived orbital parameters are too uncertain to predict accurately the position of the planet for a given epoch, we present a map of its probability of presence relatively to its parent star in the coming years.
    Do good work. —Virgil Ivan "Gus" Grissom

  7. #37
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    A powerful effort to find Proxima Centauri c optically has ended without a definite answer: was it a planet that was detected or just noise?

    https://arxiv.org/abs/2004.06685
    Searching for the near infrared counterpart of Proxima c using multi-epoch high contrast SPHERE data at VLT
    R. Gratton, et al.
    (Submitted on 14 Apr 2020)
    Proxima Centauri is known to host an earth-like planet in its habitable zone; very recently a second candidate planet was proposed based on radial velocities. At quadrature, the expected projected separation of this new candidate is larger than 1 arcsec, making it a potentially interesting target for direct imaging. While difficult, identification of the optical counterpart of this planet would allow detailed characterization of the closest planetary system. We searched for a counterpart in SPHERE images acquired during four years through the SHINE survey. In order to account for the large orbital motion of the planet, we used a method that assumes the circular orbit obtained from radial velocities and exploits the sequence of observations acquired close to quadrature in the orbit. We checked this with a more general approach that considers keplerian motion, K-stacker. We did not obtain a clear detection. The best candidate has S/N=6.1 in the combined image. A statistical test suggests that the probability that this detection is due to random fluctuation of noise is < 1% but this result depends on the assumption that distribution of noise is uniform over the image. The position of this candidate and the orientation of its orbital plane fit well with observations in the ALMA 12m array image. However, the astrometric signal expected from the orbit of the candidate we detected is 3-sigma away from the astrometric motion of Proxima as measured from early Gaia data. This, together with the unexpectedly high flux associated with our direct imaging detection, means we cannot confirm that our candidate is indeed Proxima c. On the other hand, if confirmed, this would be the first observation in imaging of a planet discovered from radial velocities and the second one (after Fomalhaut b) of reflecting circumplanetary material. Further confirmation observations should be done as soon as possible.
    Do good work. —Virgil Ivan "Gus" Grissom

  8. #38
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    More on the image of "Proxima c" and whether it is the real thing.

    https://www.syfy.com/syfywire/is-thi...ar-maaaaaaaybe
    Last edited by Roger E. Moore; 2020-Apr-16 at 07:51 PM.
    Do good work. —Virgil Ivan "Gus" Grissom

  9. #39
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    New observations of Proxima Centauri say planet b exists, but planet c, if there, is smaller than Earth. What?

    https://arxiv.org/abs/2005.12114
    Revisiting Proxima with ESPRESSO
    A. Suárez Mascareño, et al.
    [Submitted on 25 May 2020]
    We aim to confirm the presence of Proxima b using independent measurements obtained with the new ESPRESSO spectrograph, and refine the planetary parameters taking advantage of its improved precision. We analysed 63 spectroscopic ESPRESSO observations of Proxima taken during 2019. We obtained radial velocity measurements with a typical radial velocity photon noise of 26 cm/s. We ran a joint MCMC analysis on the time series of the radial velocity and full-width half maximum of the cross-correlation function to model the planetary and stellar signals present in the data, applying Gaussian process regression to deal with stellar activity. We confirm the presence of Proxima b independently in the ESPRESSO data. The ESPRESSO data on its own shows Proxima b at a period of 11.218 ±0.029 days, with a minimum mass of 1.29 ±0.13 Me. In the combined dataset we measure a period of 11.18427 ±0.00070 days with a minimum mass of 1.173 ±0.086 Me. We find no evidence of stellar activity as a potential cause for the 11.2 days signal. We find some evidence for the presence of a second short-period signal, at 5.15 days with a semi-amplitude of merely 40 cm/s. If caused by a planetary companion, it would correspond to a minimum mass of 0.29 ±0.08 Me. We find that the FWHM of the CCF can be used as a proxy for the brightness changes and that its gradient with time can be used to successfully detrend the radial velocity data from part of the influence of stellar activity. The activity-induced radial velocity signal in the ESPRESSO data shows a trend in amplitude towards redder wavelengths. Velocities measured using the red end of the spectrograph are less affected by activity, suggesting that the stellar activity is spot-dominated. The data collected excludes the presence of extra companions with masses above 0.6 Me at periods shorter than 50 days.
    Do good work. —Virgil Ivan "Gus" Grissom

  10. #40
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    If Proxima b has continents and oceans, how will that affect its climate and habitability?

    https://arxiv.org/abs/2005.14185
    The Effect of Substellar Continent Size on Ocean Dynamics of Proxima Centauri b
    Andrea M. Salazar, Stephanie L. Olson, Thaddeus D. Komacek, Haynes Stephens, Dorian S. Abbot
    [Submitted on 28 May 2020]
    The potential habitability of tidally locked planets orbiting M-dwarf stars has been widely investigated in recent work, typically with a non-dynamic ocean and without continents. On Earth, ocean dynamics are a primary means of heat and nutrient distribution. Continents are a critical source of nutrients, strongly influence ocean dynamics, and participate in climate regulation. In this work, we investigate how the size of a substellar land mass affects the oceans ability to transport heat and upwell nutrients on the tidally locked planet Proxima Centauri b using the ROCKE-3D coupled ocean-atmosphere General Circulation Model (GCM). We find that dayside ice-free ocean and nutrient delivery to the mixed layer via upwelling are maintained across all continent sizes. We also find that Proxima Centauri ** climate is more sensitive to differences among atmospheric GCMs than to the inclusion of ocean dynamics in ROCKE-3D. Finally, we find that Proxima Centauri b transitions from a lobster state where ocean heat transport distributes heat away from the substellar point to an eyeball state where heat transport is restricted and surface temperature decreases symmetrically from the substellar point when the continent size exceeds about 20 percent of the surface area. Our work suggests that both a dynamic ocean and continents are unlikely to decrease the habitability prospects of nearby tidally locked targets like Proxima Centauri b that could be investigated with future observations by the James Webb Space Telescope (JWST).
    Do good work. —Virgil Ivan "Gus" Grissom

  11. #41
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    Yet another detection of Proxima c, different from the previous ones.

    https://phys.org/news/2020-06-astron...t-proxima.html
    Do good work. —Virgil Ivan "Gus" Grissom

  12. #42
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    Astronomers at McDonald Observatory confirm a second planet, 7x Earth mass, at Proxima Centauri

    https://earthsky.org/space/2nd-exopl...oxima-centauri
    A 2nd exoplanet confirmed for Proxima Centauri
    https://mcdonaldobservatory.org/news/releases/20200602
    2 June 2020
    AUSTIN — Fritz Benedict has used data he took over two decades ago with Hubble Space Telescope to confirm the existence of another planet around the Sun’s nearest neighbor, Proxima Centauri, and to pin down the planet’s orbit and mass. Benedict, an emeritus Senior Research Scientist with McDonald Observatory at The University of Texas at Austin, will present his findings today in a scientific session and then in a press conference at a meeting of the American Astronomical Society.
    Proxima Centauri has been in the news frequently since 2016, when scientists including McDonald Observatory’s Michael Endl found its first planet, Proxima Centauri b. The discovery incited speculation on the types of in-depth studies that could done on an extrasolar planet so close to our own solar system.
    Adding to the excitement, earlier this year a group led by Mario Damasso of Italy’s National Institute for Astrophysics (INAF) announced they might have found another planet orbiting Proxima Centauri farther out. This group used radial velocity observations, that is, measurements of the star’s motion on the sky toward and away from Earth, to deduce the possible planet (dubbed Proxima Centauri c) orbits the star every 1,907 days at distance of 1.5 AU (that is, 1.5 times the distance at which Earth orbits the Sun).
    Do good work. —Virgil Ivan "Gus" Grissom

  13. #43
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    This is getting confusing. Either astronomers are talking about two different planets, both called Proxima c, or someone is wrong, or something. The ESPRESSO data does not match up with this latest information, and other studies do not match up either.
    Do good work. —Virgil Ivan "Gus" Grissom

  14. #44
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    Proxima Centauri's flares are not the only danger to life on Proxima b.

    https://arxiv.org/abs/2006.12503
    [Submitted on 22 Jun 2020]
    Risks for Life on Proxima b from Sterilizing Asteroid Impacts
    Amir Siraj, Abraham Loeb
    We consider the implications that a debris belt located between Proxima b and Proxima c would pose for the rate of large asteroid impacts that could sterilize Proxima b from life. Future observations by ALMA or JWST could constrain the existence of an asteroid belt in the life-threatening regime. We generalize our rate calculation of sterilizing impacts for habitable planets in systems with an asteroid belt and an outer planet.
    Do good work. —Virgil Ivan "Gus" Grissom

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