Results 1 to 16 of 16

Thread: I guess Peter VAn De Kamp was right

  1. #1

    I guess Peter VAn De Kamp was right

    Looks like there is a planet around Bernard's Star after all, about 3.2 earth masses and an ice ball at temperature of -150 C, I guess Hoth.
    http://spaceref.com/extrasolar-plane...ears-away.html
    From the wilderness into the cosmos.
    You can not be afraid of the wind, Enterprise: Broken Bow.
    https://davidsuniverse.wordpress.com/

  2. #2
    Join Date
    Sep 2004
    Location
    South Carolina
    Posts
    5,435
    What the heck.


    Can't believe it.

    Wasn't what he detected, but still... whoa. This one and Lalande 21185.
    Do good work. —Virgil Ivan "Gus" Grissom

  3. #3
    Join Date
    Sep 2004
    Location
    South Carolina
    Posts
    5,435
    More about this stunning discovery. Possibly two planets?


    https://phys.org/news/2018-11-astron...nard-star.html

    Astronomers discover super-Earth around Barnard's star
    November 14, 2018, Queen Mary, University of London

    ======

    https://www.nature.com/articles/s41586-018-0677-y

    Nature, Letter | Published: 14 November 2018
    A candidate super-Earth planet orbiting near the snow line of Barnard’s star
    I. Ribas, M. Tuomi, […]G. Anglada-Escudé
    Nature volume 563, pages 365–368 (2018)

    Barnard’s star is a red dwarf, and has the largest proper motion (apparent motion across the sky) of all known stars. At a distance of 1.8 parsecs1, it is the closest single star to the Sun; only the three stars in the α Centauri system are closer. Barnard’s star is also among the least magnetically active red dwarfs known2,3 and has an estimated age older than the Solar System. Its properties make it a prime target for planetary searches; various techniques with different sensitivity limits have been used previously, including radial-velocity imaging4,5,6, astrometry7,8 and direct imaging9, but all ultimately led to negative or null results. Here we combine numerous measurements from high-precision radial-velocity instruments, revealing the presence of a low-amplitude periodic signal with a period of 233 days. Independent photometric and spectroscopic monitoring, as well as an analysis of instrumental systematic effects, suggest that this signal is best explained as arising from a planetary companion. The candidate planet around Barnard’s star is a cold super-Earth, with a minimum mass of 3.2 times that of Earth, orbiting near its snow line (the minimum distance from the star at which volatile compounds could condense). The combination of all radial-velocity datasets spanning 20 years of measurements additionally reveals a long-term modulation that could arise from a stellar magnetic-activity cycle or from a more distant planetary object. Because of its proximity to the Sun, the candidate planet has a maximum angular separation of 220 milliarcseconds from Barnard’s star, making it an excellent target for direct imaging and astrometric observations in the future.
    Do good work. —Virgil Ivan "Gus" Grissom

  4. #4
    Join Date
    Sep 2006
    Posts
    1,860
    The signal-to-noise ratio of this detection is ... not so high.

    barn.jpg

    It's rarely a good sign when the authors spend page after page of the supplemental material discussing the techniques used to pull the signal out of the data.

  5. #5
    Join Date
    May 2010
    Posts
    77
    No, unfortunately, Peter van de Kamp was not right.

    His "planets" are shown on page 94 of Ken Croswell's book Planet Quest, which includes interviews with the two astronomers who disproved their existence. See pages 90-99 in the chapter "A Shaky Start."

    Van de Kamp's planets were both giants on orbits roughly as large as Jupiter's.

    In contrast, the newly discovered planet, if real, is a super-Earth whose orbital distance from the star is comparable to Mercury's and whose orbital period is similar to that of Venus.

    There is therefore no resemblance between the new planet and those proposed by Peter van de Kamp.

  6. #6
    Join Date
    Sep 2004
    Location
    South Carolina
    Posts
    5,435
    I think the reason so many of the stars once getting erroneous identifications of having giant planets are now turning up with smaller planets is simply because LOTS of stars, especially red dwarfs, have planets. Not a coincidence, just turned out that planets are everywhere, even places we gave up on.
    Do good work. —Virgil Ivan "Gus" Grissom

  7. #7
    Quote Originally Posted by SagittariusAStar View Post
    No, unfortunately, Peter van de Kamp was not right.

    His "planets" are shown on page 94 of Ken Croswell's book Planet Quest, which includes interviews with the two astronomers who disproved their existence. See pages 90-99 in the chapter "A Shaky Start."

    Van de Kamp's planets were both giants on orbits roughly as large as Jupiter's.

    In contrast, the newly discovered planet, if real, is a super-Earth whose orbital distance from the star is comparable to Mercury's and whose orbital period is similar to that of Venus.

    There is therefore no resemblance between the new planet and those proposed by Peter van de Kamp.
    I was speaking more in the metaphorical sense than a literal one. I also read the history in Searching For Earths by Allen Boss.
    From the wilderness into the cosmos.
    You can not be afraid of the wind, Enterprise: Broken Bow.
    https://davidsuniverse.wordpress.com/

  8. #8
    Join Date
    Sep 2004
    Location
    South Carolina
    Posts
    5,435
    New paper discussing discovery of Barnard's Star b and under what conditions we could determine its mass exactly, and why that is a problem for now. I am not sure if the paper is actually throwing doubt on the discovery of this super-Earth. You can read it and tell me.


    https://arxiv.org/abs/1811.05920

    Prospects for detecting the astrometric signature of Barnard's Star b

    Lev Tal-Or, Shay Zucker, Ignasi Ribas, Guillem Anglada-Escudé, Ansgar Reiners (Submitted on 14 Nov 2018)

    A low-amplitude periodic signal in the radial-velocity (RV) time-series of Barnard's Star was recently attributed to a planetary companion with a minimum mass of ∼3.2 M⊕ at an orbital period of ∼233 days. The proximity of Barnard's Star to the Sun raises the question whether the true mass of the planet can be constrained by accurate astrometric measurements. We review the astrometric capabilities and limitations of current and upcoming astrometric instruments. By combining the assumption of an isotropic probability distribution of the orbital orientation with the RV analysis results, we calculate the probability distribution function of the planet's astrometric signature. We conclude that there is a probability of only ∼1% that Gaia observations will detect it. Observations with the Hubble Space Telescope (HST) may increase the detection probability to ∼10%. In case of no detection, the implied mass upper limit with HST observations would be ∼8 M⊕, which will place the planet in the super-Earth mass range. In the next decade, observations with the Wide-Field Infrared Space Telescope (WFIRST) may increase the prospects of measuring the planet's true mass to ∼99%.

    QUOTES: Barnard’s Star is the second-nearest stellar system. The search for planets around Barnard’s Star depicts the history of achievable astrometric and RV precision for M dwarfs. It is also one of the most famous premature claims for exoplanet detections. For two decades van de Kamp (1963, 1969a,b, 1975, 1982) had been claiming an astrometric detection of one or two Jovian planets with orbital periods between 11 and 26 years. These claims were first questioned by Gatewood & Eichhorn (1973), and later rejected at a confidence level of ∼94% by Choi et al. (2013). By using precision RVs, Choi et al. (2013) could exclude the possibility of Jupiter-mass planets at almost any orbital period ~ 25 years, except for the most unlikely case of almost face-on orbits. The best existing astrometric constraints on planets around Barnard’s Star were set by Benedict et al. (1999). Using the Fine Guidance Sensor of the Hubble Space Telescope (HST-FGS), they managed to exclude an astrometric orbital perturbation larger than 1250µas, with periods of 5–600 days, at ∼95% confidence level, which translates to mass upper limits of ∼1 MJ at P ∼ 150 day orbit, or∼0.5MJ at P ∼ 400 day orbit.

    Recently, Ribas et al. (2018) reported an RV detection of a planet candidate in orbitaroundBarnard’sStar.Table1givesthe main parameters of Barnard’s Star and the detected planet. In this paper we ask the question whether the planet’s true mass can be constrained by accurate astrometric measurements of Barnard’s Star. In what follows, we estimate the probability of detecting the planet’s astrometric signature with existing and upcoming instruments, as well as the achievable mass upper limit in case of no detection.

    We reviewed the astrometric capabilities and limitations of current and forthcoming instruments, and found the HST to currently be the most promising instrument to detect the astrometric signature of Barnard’s Star b. Assuming the HST can reach an accuracy of σΛ ∼ 30µas, we found a probabilityof∼10% to detect the planet’s astrometric signature with Nobs ∼ 50. In case of no detection, which would correspond to a nearly edge-on orbit, the implied mass upper limit would be mp . 8 M⊕, which would place the planet in the super-Earth mass range. Despite the fact that Gaia will continue observing Barnard’s Star for the next few years, and will release its results around 2023,weexpectanadditionalastrometricHST-WFC3 follow-up observations to place better constrains on the mass of Barnard’s Star b. As opposed to Gaia, the timings and scan directions of HST observations can be tuned to optimize the detectability of the orbit. If in the next decade an accuracy of σΛ ∼ 10µas is indeed reached for Barnard’s Star, for example with WFIRST (Melchior et al. 2018), the prospects of measuring the planet’s true mass will growto∼99%.Then, Gaia and HST observations performed in the next few years will set valuable constraints on some parameters of the astrometric model that benefit from observations over long time baseline.

    ===========

    I wish to point out an error here, that many people believe Dr. van de Kamp "discovered" Barnard's Star b in 1963. He claimed to have actually discovered it in 1939, per a paper he wrote in 1945 (below)

    http://articles.adsabs.harvard.edu/c...;filetype=.pdf

    Stars Nearer than Five Parsecs

    van de Kamp, Peter
    Publications of the Astronomical Society of the Pacific, Vol. 57, No. 334, p.34 (02/1945)

    QUOTE: Variable proper motions have been discovered at the Sproul Observatory for Barnard's star (1939), for Lalande 21185 (1941), and4 for BD+5°1668 (1943). Provisional orbits for the first two of these stars give periods of somewhat more than a year, photocentric semi-axes major of somewhat more than 0.1 A.U., and for the unseen companions minimum masses of about 0.06 Θ.
    Do good work. —Virgil Ivan "Gus" Grissom

  9. #9
    Quote Originally Posted by The Backroad Astronomer View Post
    I was speaking more in the metaphorical sense than a literal one. I also read the history in Searching For Earths by Allen Boss.
    Sorry Alan Boss, just found the book.
    From the wilderness into the cosmos.
    You can not be afraid of the wind, Enterprise: Broken Bow.
    https://davidsuniverse.wordpress.com/

  10. #10
    Join Date
    Sep 2004
    Location
    South Carolina
    Posts
    5,435
    Two recent papers on Barnard's Star, which as noted earlier turns out to have at least one planet after all, thank heaven.


    https://arxiv.org/abs/1812.06712

    Stellar activity analysis of Barnard's Star: Very slow rotation and evidence for long-term activity cycle

    B. Toledo-Padrón, et al. (Submitted on 17 Dec 2018)

    The search for Earth-like planets around late-type stars using ultra-stable spectrographs requires a very precise characterization of the stellar activity and the magnetic cycle of the star, since these phenomena induce radial velocity (RV) signals that can be misinterpreted as planetary signals. Among the nearby stars, we have selected Barnard's Star (GJ 699) to carry out a characterization of these phenomena using a set of spectroscopic data that covers about 14.5 years and comes from seven different spectrographs: HARPS, HARPS-N, CARMENES, HIRES, UVES, APF, and PFS; and a set of photometric data that covers about 15.1 years and comes from four different photometric sources: ASAS, FCAPT-RCT, AAVSO, and SNO. We have measured different chromospheric activity indicators (Hα , Ca~{\sc II}~HK and Na I D), as well as the FWHM of the cross-correlation function computed for a sub-set of the spectroscopic data. The analysis of Generalized Lomb-Scargle periodograms of the time series of different activity indicators reveals that the rotation period of the star is 145 ± 15 days, consistent with the expected rotation period according to the low activity level of the star and previous claims. The upper limit of the predicted activity-induced RV signal corresponding to this rotation period is about 1 m/s. We also find evidence of a long-term cycle of 10 ± 2 years that is consistent with previous estimates of magnetic cycles from photometric time series in other M stars of similar activity levels. The available photometric data of the star also support the detection of both the long-term and the rotation signals.

    ======

    https://arxiv.org/abs/1901.00219

    Breezing through the space environment of Barnard's Star b

    Julián D. Alvarado-Gómez, et al. (Submitted on 1 Jan 2019)

    A physically realistic stellar wind model based on Alfvén wave dissipation has been used to simulate the wind from Barnard's Star and to calculate the conditions at the location of its recently discovered planetary companion. Barnard's Star b experiences much less intense wind pressure than the much more close-in planet Proxima~b and the planets of the TRAPPIST-1 system. The milder wind conditions are more a result of its much greater orbital distance rather than in differences in the surface magnetic field strengths of the host stars. The dynamic pressure is on average 15 times higher than experienced by the present-day Earth, and undergoes variations by factors of several as it passes through the current sheet in each orbit. The magnetopause standoff distance is ∼ 30−60 % smaller than that of the Earth for an equivalent planetary magnetic field strength.

    QUOTES: The detection by Ribas et al. (2018) of a planet around Barnard's Star is an important step in our growing understanding of the nature of planetary systems in the Universe. The M3 V red dwarf Barnard's Star is the closest star to the Sun after the alpha Centauri system, making it the closest single star planetary system. Barnard's Star b (BSb) orbits at a distance similar to that of Mercury around the Sun. Ribas et al. (2018) note that the planet resides close to the "snow line" of Barnard's Star, where stellar irradiation is sufficiently weak to allow volatile elements to condense (Kennedy & Kenyon 2008). This characteristic renders BSb of special interest from the perspective of planet formation.
    Do good work. —Virgil Ivan "Gus" Grissom

  11. #11
    Join Date
    Sep 2004
    Location
    South Carolina
    Posts
    5,435
    Surprising new reports on possible life on Barnard b, if it has a subsurface ocean and is not a mini-Neptune.

    ======== [[poster type might be rather small]]

    http://clusty.ast.villanova.edu/gall...er_AAS2019.pdf

    X-ray, UV, Optical Irradiances and Age of Barnard’s Star’s new
    Super-earth Planet:—“Can Life find a way” on a cold Planet? [[poster]]

    ========

    https://www.space.com/42963-barnards...habitable.html

    Barnard's Star Planet May Not Be Too Cold for Life After All
    By Nola Taylor Redd, Space.com Contributor | January 10, 2019 05:22pm ET

    SEATTLE — One of Earth's nearest exoplanet neighbors, the planet orbiting Barnard's Star, may still have a chance at hosting life, despite its frigid temperatures. New research suggests that heat generated by geothermal processes could warm pockets of water beneath the surface of the planet called Barnard's Star b, potentially providing havens for life to evolve. Images captured by NASA's much-delayed James Webb Space Telescope could help determine if the planet is the right size for that phenomenon to occur, and instruments coming even later in the future could identify signs of life.

    "This is the best-imageable planet, the best Earth-sized one," Edward Guinan, a researcher at Villanova University in Pennsylvania, told Space.com. Using 15 years of data, Guinan and his colleague Scott Engle, also at Villanova, determined that while the planet is too cold for liquid water, and thus probably for life, to exist on the surface, the world might still hold subsurface oceans, depending on how large it is. Such oceans could form only on a rocky world, but if the planet is a gas giant, all bets are off. "If it's a super-Earth, it could have anything going on," Engle said. The two researchers announced their results here at the 233rd annual winter meeting of the American Astronomical Society.
    Do good work. —Virgil Ivan "Gus" Grissom

  12. #12
    Join Date
    Sep 2004
    Location
    South Carolina
    Posts
    5,435
    The real problem is that without knowing the planet's orbital inclination, we can't yet know its true mass and size.
    Do good work. —Virgil Ivan "Gus" Grissom

  13. #13
    Join Date
    Sep 2004
    Location
    South Carolina
    Posts
    5,435
    Revised version out. So near....

    https://arxiv.org/abs/1811.05920

    Prospects for detecting the astrometric signature of Barnard's Star b

    Lev Tal-Or, Shay Zucker, Ignasi Ribas, Guillem Anglada-Escudé, Ansgar Reiners (Submitted on 14 Nov 2018 (v1), last revised 6 Mar 2019 (this version, v2))

    A low-amplitude periodic signal in the radial velocity (RV) time series of Barnard's Star was recently attributed to a planetary companion with a minimum mass of ∼ 3.2 M ⊕ at an orbital period of ∼ 233 days. The relatively long orbital period and the proximity of Barnard's Star to the Sun raises the question whether the true mass of the planet can be constrained by accurate astrometric measurements. By combining the assumption of an isotropic probability distribution of the orbital orientation with the RV-analysis results, we calculated the probability density function of the astrometric signature of the planet. In addition, we reviewed the astrometric capabilities and limitations of current and upcoming astrometric instruments. We conclude that Gaia and the Hubble Space Telescope (HST) are currently the best-suited instruments to perform the astrometric follow-up observations. Taking the optimistic estimate of their single-epoch accuracy to be ∼ 30 μ as, we find a probability of ∼ 10% to detect the astrometric signature of Barnard's Star b with ∼ 50 individual-epoch observations. In case of no detection, the implied mass upper limit would be ∼ 8 M ⊕ , which would place the planet in the super-Earth mass range. In the next decade, observations with the Wide-Field Infrared Space Telescope (WFIRST) may increase the prospects of measuring the true mass of the planet to ∼ 99%.
    Do good work. —Virgil Ivan "Gus" Grissom

  14. #14
    Join Date
    May 2019
    Posts
    1
    Van de Kamp's planets were both giants on orbits roughly as large as Jupiter's.

    In contrast, the newly discovered planet, if real, is a super-Earth whose orbital distance from the star is comparable to Mercury's and whose orbital period is similar to that of Venus.

    There is therefore no resemblance between the new planet and those proposed by Peter van de Kamp. DQFanFeedback
    Last edited by Tyson251; 2019-May-17 at 07:33 AM.

  15. #15
    Join Date
    Sep 2004
    Location
    South Carolina
    Posts
    5,435
    What could we find out about Barnard's Star b, a Neptunian planet, if we knew its radius?

    https://arxiv.org/abs/2006.08784
    [Submitted on 15 Jun 2020]
    Directly imaged exoplanets in reflected starlight. The importance of knowing the planet radius
    Óscar Carrión-González, Antonio García Muñoz, Juan Cabrera, Szilárd Csizmadia, Nuno C. Santos, Heike Rauer
    We have investigated the information content in reflected-starlight spectra of exoplanets. We specify our analysis to Barnard's Star b candidate super-Earth, for which we assume a radius 0.6 times that of Neptune, an atmosphere dominated by H2-He, and a CH4 volume mixing ratio of 5x10^−3. The main conclusions of our study are however planet-independent. We set up a model of the exoplanet described by seven parameters including its radius, atmospheric methane abundance and basic properties of a cloud layer. We generate synthetic spectra at zero phase (full disk illumination) from 500 to 900 nm and spectral resolution R∼125-225. We simulate a measured spectrum with a simplified, wavelength-independent noise model at Signal-to-Noise ratio S/N=10. With an MCMC-based retrieval methodology, we analyse which planet/atmosphere parameters can be inferred from the measured spectrum and the theoretical correlations amongst them. We consider limiting cases in which the planet radius is either known or completely unknown, and intermediate cases in which the planet radius is partly constrained. If the planet radius is known, we can generally discriminate between cloud-free and cloudy atmospheres, and constrain the methane abundance to within two orders of magnitude. If the planet radius is unknown, new correlations between model parameters occur and the accuracy of the retrievals decreases. Without a radius determination, it is challenging to discern whether the planet has clouds, and the estimates on methane abundance degrade. However, we find the planet radius is constrained to within a factor of two for all the cases explored. Having a priori information on the planet radius, even if approximate, helps improve the retrievals. We urge exoplanet detection efforts to extend the population of long-period planets with mass and radius determinations.
    Do good work. —Virgil Ivan "Gus" Grissom

  16. #16
    Join Date
    Sep 2004
    Location
    South Carolina
    Posts
    5,435
    Older flare stars might be better targets for searches for planets with stable atmsopheres.


    https://arxiv.org/abs/2009.01259

    The High-Energy Radiation Environment Around a 10 Gyr M Dwarf: Habitable at Last?

    Kevin France, Girish Duvvuri, Hilary Egan, Tommi Koskinen, David J. Wilson, Allison Youngblood, Cynthia S. Froning, Alexander Brown, Julian D. Alvarado-Gomez, Zachory K. Berta-Thompson, Jeremy J. Drake, Cecilia Garraffo, Lisa Kaltenegger, Adam F. Kowalski, Jeffrey L. Linsky, R.O. Parke Loyd, Pablo J. D. Mauas, Yamila Miguel, J. Sebastian Pineda, Sarah Rugheimer, P. Christian Schneider, Feng Tian, Mariela Vieytes

    High levels of X-ray and UV activity on young M dwarfs may drive rapid atmospheric escape on temperate, terrestrial planets orbiting within the liquid water habitable zone. However, secondary atmospheres on planets orbiting older, less active M dwarfs may be stable and present more promising candidates for biomarker searches. We present new HST and Chandra observations of Barnard's Star (GJ 699), a 10 Gyr old M3.5 dwarf, acquired as part of the Mega-MUSCLES program. Despite the old age and long rotation period of Barnard's star, we observe two FUV (δ130 ≈5000s; E130 ≈10^29.5 erg each) and one X-ray (EX ≈10^29.2 erg) flares, and estimate a high-energy flare duty cycle (defined here as the fraction of the time the star is in a flare state) of ∼25%. A 5A - 10 μm SED of GJ 699 is created and used to evaluate the atmospheric stability of a hypothetical, unmagnetized terrestrial planet in the habitable zone (rHZ ∼0.1 AU). Both thermal and non-thermal escape modeling indicate (1) the quiescent stellar XUV flux does not lead to strong atmospheric escape: atmospheric heating rates are comparable to periods of high solar activity on modern Earth, and (2) the flare environment could drive the atmosphere into a hydrodynamic loss regime at the observed flare duty cycle: sustained exposure to the flare environment of GJ 699 results in the loss of ≈ 87 Earth atmospheres Gyr^−1 through thermal processes and ≈ 3 Earth atmospheres Gyr^−1 through ion loss processes, respectively. These results suggest that if rocky planet atmospheres can survive the initial ∼5 Gyr of high stellar activity, or if a second generation atmosphere can be formed or acquired, the flare duty cycle may be the controlling stellar parameter for the stability of Earth-like atmospheres around old M stars.
    Do good work. —Virgil Ivan "Gus" Grissom

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •