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  • richardmitnick 1:38 pm on January 20, 2017 Permalink | Reply
    Tags: , , , , , , HATnet, Hot Jupiters   

    From AAS NOVA: “Reinflating Giant Planets” 


    American Astronomical Society

    18 January 2017
    Susanna Kohler

    Artist’s impression of a hot Jupiter exoplanet transiting across the face of its host star. [NASA/ESA/C. Carreau]

    Two new, large gas-giant exoplanets have been discovered orbiting close to their host stars. A recent study examining these planets — and others like them — may help us to better understand what happens to close-in hot Jupiters as their host stars reach the end of their main-sequence lives.

    Unbinned transit light curves for HAT-P-65b. [Adapted from Hartman et al. 2016]

    Oversized Giants

    The discovery of HAT-P-65b and HAT-P-66b, two new transiting hot Jupiters, is intriguing. These planets have periods of just under 3 days and masses of roughly 0.5 and 0.8 times that of Jupiter, but their sizes are what’s really interesting: they have inflated radii of 1.89 and 1.59 times that of Jupiter.

    These two planets, discovered using the Hungarian-made Automated Telescope Network (HATNet) in Arizona and Hawaii, mark the latest in an ever-growing sample of gas-giant exoplanets with radii larger than expected based on theoretical planetary structure models.

    HATNet telescopes at Fred Lawrence Whipple Observatory, Mount Hopkins, Arizona. Photo credit: Gaspar Bakos.pple-observatory-mount-hopkins-arizona-photo-credit-gaspar-bakos
    HATNet telescopes at Fred Lawrence Whipple Observatory, Mount Hopkins, Arizona. Photo credit: Gaspar Bakos

    HATnet, Mauna Kea Hawaii USA
    HATNet, Mauna Kea Hawaii USA

    What causes this discrepancy? Did the planets just fail to contract to the expected size when they were initially formed, or were they reinflated later in their lifetimes? If the latter, how? These are questions that scientists are only now starting to be able to address using statistics of the sample of close-in, transiting planets.

    Exploring Other Planets

    Unbinned transit light curves for HAT-P-66b. [Hartman et al. 2016]

    Led by Joel Hartman (Princeton University), the team that discovered HAT-P-65b and HAT-P-66b has examined these planets’ observed parameters and those of dozens of other known close-in, transiting exoplanets discovered with a variety of transiting exoplanet missions: HAT, WASP, Kepler, TrES, and KELT. Hartman and collaborators used this sample to draw conclusions about what causes some of these planets to have such large radii.

    The team found that there is a statistically significant correlation between the radii of close-in giant planets and the fractional ages of their host stars (i.e., the star’s age divided by its full expected lifetime). The two newly discovered hot Jupiters with inflated radii, for instance, are orbiting stars that are roughly 84% and 83% through their life spans and are approaching the main-sequence turnoff point.

    Fractional age of the host stars of close-in transiting exoplanets vs. the planet’s radius. There is a statistically significant correlation between age and planet radius. [Adapted from Hartman et al. 2016]

    Late-Life Reinflation

    Hartman and collaborators propose that the data support the following scenario: as host stars evolve and become more luminous toward the ends of their main-sequence lifetimes, they deposit more energy deep into the interiors of the planets closely orbiting them. These close-in planets then increase their equilibrium temperatures — and their radii reinflate as a result.

    Based on these results, we would expect to continue to find hot Jupiters with inflated radii primarily orbiting closely around older stars. Conversely, close-in giant planets around younger stars should primarily have non-inflated radii. As we continue to build our observational sample of transiting hot Jupiters in the future, we will be able to see how this model holds up.


    J. D. Hartman et al 2016 AJ 152 182. doi:10.3847/0004-6256/152/6/182

    See the full article here .

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  • richardmitnick 12:26 pm on June 22, 2016 Permalink | Reply
    Tags: , , , , Hot Jupiters, Where the Wild (Planet)Things Are   

    From Astrobites: Where the Wild (Planet)Things Are 

    New research shows hot Jupiters find safety in numbers. According to radial velocity data, these giant exoplanets are more commonly found around stars in open clusters.

    Source: Where the Wild (Planet)Things Are

    Title: Search for giant planets in M67 III: excess of hot Jupiters in dense open clusters
    Authors: A. Brucalassi, L. Pasquini, R. Saglia, M.T. Ruiz, P. Bonifacio, I. Leão, B.L. Canto Martins, J.R. de Medeiros, L. R. Bedin, K. Biazzo, C. Melo, C. Lovis, and S. Randich

    First Author’s Institution: Max-Planck für extraterrestrische Physik, Garching bei München, Germany

    Status: Accepted for publication in A&A Journal Letters

    If you wanted to discover a new giant exoplanet, where would you look? New research, shows that star clusters are a good place to start, at least if you want to look for giant exoplanets close to their host star.

    Hot Jupiters are a breed of exoplanets that have masses about or larger than Jupiter and orbit a star in 10 days or less (for comparison, Mercury takes 88 days to go around the Sun). When they were first discovered, they posed a problem to planet formation models as it was thought gas giants could only form far from their host star where it was cool enough for ices to form, which allows for larger planets to be made. Since then, studies have shown these planets could form far out and migrate inwards over their lifetime. This can happen through interactions with the disk in which the planet forms (known as Type II migration), or through gravitational scattering with other planets or nearby stars.

    Brucalassi and her team decided to investigate an open cluster in the Milky Way (Messier 67) to look for hot Jupiters. Over several years they used three different telescopes (the ESO 3.6m telescope, the Hobby Eberly Telescope and the TNG on La Palma of the Canary Islands) to take high-precision spectra of 88 stars, 12 of which are binary stars. This spectra could then be analyzed for small blue- and redshifts which indicate the star is moving slightly. In this case, that movement is caused by the presence of another body, the exoplanet. This method is known as the radial velocity method and is the method that was used in the first exoplanet discoveries. To make sure that each star’s own activity wasn’t affecting its spectra, the group measured the Hα line which shows how active the star’s chromosphere is. Figure 1 shows an example of the radial velocity measurements.

    Figure 1: Radial velocity measurements for YBP401. The coloured dots represent the different telescopes the measurements were made at. The measurements show an exoplanet with a period of just 4.08 days.

    The group’s measurements revealed a new exoplanet around the main sequence star YBP401. They were also able to get better measurements on two stars (YBP1194 and YBP1514) with known hot Jupiters. This brought the total number of hot Jupiters to 3 out of 88 stars. Although 3 might not seem like a very big number, it is larger than the number of hot Jupiters found around field stars (stars not in clusters). For the statistical analysis, Brucalassi compares the number of exoplanets with the number of main sequence and subgiant stars, i.e. stars that are not yet at the ends of their lives. Of the 88 stars, 66 are main sequence or subgiant, and of those only 53 are not binary stars. Most radial velocity studies choose to not observe binary stars so it is important to compare numbers with that in mind. A previous study from 2012 found a hot Jupiter frequency of 1.2% ± 0.38 around field stars. Brucalassi finds 4.5+4.5-2.5% when comparing with only single stars (not including binaries) in M67. To compare with statistics from the Kepler mission, binaries are included, as Kelper also surveys binaries, and the percentage for hot Jupiters in a cluster is 5.6+5.4-2.6%. The Kepler mission finds a frequency of hot Jupiters of just ~0.4%, which is considerably lower. And this trend isn’t seen just in M67. Combining radial velocity surveys for the clusters M67, Hyades, and Praesepe, there are 6 hot Jupiters in 240 surveyed stars, whereas the study from 2012 found only 12 in survey of 836 field stars.

    It’s known that systems with more metals tend to produce more planets and the star’s mass may also have an effect on planet production. However, the clusters stars and field stars are on average the same mass, so this alone cannot account for the differneces. M67 is also at solar metallicity (i.e. it’s stars tend to have the same amount of metals as our Sun) so this can also not account for the excess of hot Jupiters. Brucalassi concludes that the high number of hot Jupiters is due to the environment. Past simulations show that stars in a crowded cluster environment will experience at least one close encounter with another star, which is all that is needed to drive a Jupiter in to a closer orbit. This new research gives further evidence to this theory, putting us one step closer to understanding how exoplanets can form.

    Figure 2: An artist’s rendition of the new hot Jupiter. Click on the image for a full animated video of the M67 cluster. Courtesy of the ESO press release (#eso1621).

  • richardmitnick 4:49 pm on March 31, 2016 Permalink | Reply
    Tags: , , , Hot Jupiters, TYC 3667-1280-1   

    From astrobites: “A Warm Jupiter around an Evolving Star: Exploring Planet Migration” 

    Astrobites bloc


    Mar 31, 2016
    Matthew Green

    Title: TAPAS IV. TYC 3667-1280-1 b – the most massive red giant star hosting a warm Jupiter
    Authors: A. Niedzielski, E. Villaver, G. Nowak, M. Adamów, G. Maciejewski, K. Kowalik, A. Wolszczan, B. Deka-Szymankiewicz, M. Adamczyk
    First Author’s Institution: Toruń Centre for Astronomy, Nicolaus Copernicus University, Toruń, Poland
    Status: Accepted by A&A

    Planetary systems are dynamic places. Some planetary orbits change over time, moving the planet either closer in towards the star or further out. Not only that, but the stars in the centre of planetary systems will eventually evolve off the main sequence, growing into giants and then, in most cases, collapsing into white dwarfs. This can significantly change the planetary system as a whole, in some cases leading to planets being swallowed by their host stars or ejected from the system. Of course, these changes occur over timescales of millions to billions of years.

    There has recently been a spike of interest in what happens to planets as their host star evolves, inspired by the discovery of a system of disintegrating planets around a white dwarf. Today’s paper introduces TYC 3667-1280-1, a Jupiter-mass exoplanet whose host star is in the process of evolving into a giant. The authors believe that the planet is of interest not only because of its evolving host, but also because of the planet’s potentially revealing migration history.

    Stars as Homes for Habitable Planetary Systems. JPL-Caltech
    Stars as Homes for Habitable Planetary Systems. JPL-Caltech

    Warm Jupiters and the Kozai-Lidov mechanism

    Planets of Jupiter mass, like TYC 3667-1280-1, are thought to form far out in the system, where there is more material from which they can form. However, we have seen many Jupiter-mass planets which are incredibly close to their host star, often much closer than the Earth is to the Sun. Consequentially these systems have very short orbital periods. The so-called hot Jupiters have orbits shorter than 10 days, while “warm Jupiters” have orbits of 10-100 days (compare this to Jupiter’s orbital period of 12 years).

    How did these planets end up so close to their host stars? Warm and hot Jupiters may have travelled inwards by different means. Jupiter-mass planets can migrate inwards by being gravitationally pushed to high eccentricities (highly elliptical orbits). However, many systems in both classes have orbits with very low (their orbits are almost perfect circles). In hot Jupiters, the planet’s orbit can be “circularised” again by the gravitational pull of the star — however, this doesn’t work as well across the distances at which warm Jupiters orbit. How, then, do we explain the low eccentricities in some warm Jupiters?

    There’s also a second mystery around warm Jupiters. We see fewer hot and warm Jupiters around evolved or evolving stars than we do around main sequence stars. For hot Jupiters this is easily explained: for most of these systems, the planet is close enough to have been swallowed by its host star. However, warm Jupiters are further out from their stars, and so we would expect them to last longer than they seem to.

    Both of these problems might be explained by an effect known as the Kozai-Lidov mechanism. This is a tidal effect that occurs in hierarchical three-body systems – that is, systems in which two of the bodies (in this case, a star and a planet) are in a tight orbit around each other, with a third object in a wider orbit around the two (a potentially unseen companion such as a brown dwarf). If the orbit of the outer object is tilted relative to the orbits of the inner binary, the gravity of the outer object pulls on the inner pair in such a way that the eccentricity of their orbits fluctuates. (For more detail on the Kozai-Lidov mechanism, see Erika Nesvold’s section in this astrobite.) The low-eccentricity warm Jupiters that we see could simply be those in a low-eccentricity phase of these fluctuations.

    Conversely, when the planet fluctuates up to a highly eccentric orbit it will pass much closer to its host star, causing it to be swallowed by the expanding star much earlier than it would be if there were no Kozai-Lidov mechanism in play. In fact, for a sample system their simulations showed the planet might be swallowed by the time the star grew to 5 solar radii, compared to 40 solar radii for the same system with no Kozai-Lidov mechanism.

    TYC 3667-1280-1

    Enter TYC 3667-1280-1, whose star has a radius of 6.3 solar radii — putting it just inside the range of what should have been swallowed if the Kozai-Lidov mechanism is at work in this system. In other respects TYC 3667-1280-1 appears to be a typical warm Jupiter, having the low eccentricity (0.036 in this case) that could imply the Kozai-Lidov mechanism is at work. Further studies of TYC 3667-1280-1 could help clear up this seeming conflict, as well as helping us to understand the Kozai-Lidov mechanism further.

    The science team:
    A. Niedzielski1, E. Villaver2, G. Nowak3; 4; 1, M. Adamów5; 1, G. Maciejewski1, K. Kowalik6, A. Wolszczan7; 8, B.
    Deka-Szymankiewicz1, and M. Adamczyk1
    1 Toru´n Centre for Astronomy, Faculty of Physics, Astronomy and Applied Informatics, Nicolaus Copernicus University in Toru´n,
    Grudziadzka 5, 87-100 Toru´n, Poland. e-mail: Andrzej.Niedzielski@umk.pl
    2 Departamento de Física Teórica, Universidad Autónoma de Madrid, Cantoblanco 28049 Madrid, Spain. e-mail:
    3 Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain.
    4 Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain.
    5 McDonald Observatory and Department of Astronomy, University of Texas at Austin, 2515 Speedway, Stop C1402, Austin, Texas,
    78712-1206, USA.
    6 National Center for Supercomputing Applications, University of Illinois, Urbana-Champaign, 1205 W Clark St, MC-257, Urbana,
    IL 61801, USA
    7 Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802,
    USA. e-mail: alex@astro.psu.edu
    8 Center for Exoplanets and Habitable Worlds, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802,

    See the full article here .

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    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

  • richardmitnick 11:59 am on March 10, 2016 Permalink | Reply
    Tags: , , Hot Jupiters,   

    From phys.org: “Astronomers discover two new ‘hot Jupiter’ exoplanets” 


    March 10, 2016
    Tomasz Nowakowski

    Hot Jupiter orbiting one star in a binary system
    Hot Jupiter orbiting one star in a binary system (not part of this work)

    A team of Chilean astronomers recently detected two new hot Jupiters using the data from NASA’s Kepler spacecraft operating in a new mission profile called K2.

    NASA Kepler Telescope

    The planets, designated EPIC210957318b and EPIC212110888b, were discovered via the radial velocity method, and are excellent candidates for further orbital and atmospheric characterization via detailed follow-up observations. A research paper describing the discovery appeared online on Mar. 5, on the arXiv server.

    The so-called “hot Jupiters” are gas giant planets, similar in characteristics to the solar system’s biggest planet, with orbital periods of less than 10 days. They have high surface temperatures as they orbit their parent stars very closely—between 0.015 and 0.5 AU—while Jupiter orbits the sun at 5.2 AU. To date, about 250 transiting “hot Jupiters” have been found, mostly by ground-based photometric surveys. Now, the researchers have made use of a space-borne telescope to detect new, interesting hot giant exoworlds.

    K2 is a repurposed mission of the Kepler spacecraft to perform high-precision photometry of selected fields in the ecliptic, following the failure of two reaction wheels in 2013. Due to this malfunction, observations are currently conducted only within the orbital plane of the spacecraft, which approximates to the ecliptic. However, despite these difficulties, K2 has managed to detect 234 planetary candidates in the first year of the mission.

    The researchers, led by Rafael Brahm of the Pontifical Catholic University of Chile, have analyzed the photometric data of K2’s two observation campaigns and discovered that the stars EPIC210957318 and EPIC212110888 show significant periodic signals every four and three days, respectively.

    “Both of these systems were selected as strong Jovian planetary candidates based on their transit properties (depths, shapes and durations), and due to the lack of evident out of transit variations,” the paper reads.

    Next, the researchers acquired high-resolution spectra of the two candidates, with three different stabilized spectrographs mounted on telescopes at the [ESO]La Silla Observatory in Chile. These instruments were helpful in measuring the radial velocity variation of the stellar hosts produced by the gravitational pull of orbiting planets.

    ESO LaSilla
    ESO La Silla

    According to the paper, the smaller planet of the newly discovered duo, named EPIC210957318b, orbits its parent sun-like star, located about 970 light years from the Earth, every 4.1 days. The mass of this exoplanet is between the Saturn and Jupiter masses (approximately 0.65 Jupiter masses) and its radius is slightly larger than the one of the solar system’s largest planets. The temperatures on this planet range from 584 to 939 degrees Celsius.

    EPIC212110888b is more massive and larger than Jupiter. Having a mass of about 1.63 Jupiter masses, this planet orbits its host star every three days and is even hotter than EPIC210957318b, with temperatures spanning from 932 to 1,430 degrees Celsius. The star, slightly more massive than sun, lies some 1,270 light years away from our planet.

    Both planets have similar densities, close to half of Jupiter’s. The scientists noted that the physical and orbital properties of both of these extrasolar systems are typical of the population of known hot Jupiters. They also concluded that these two exoplanets are interesting candidates for follow-up studies.

    “The low density of EPIC210957318b combined with the relatively small radius of its host star implies a scale height of 340 km and a transmission spectroscopic signal of 744 ppm (assuming an H2 dominated atmosphere and a signal of five scale-heights), which means that this system is a good target to be observed via transmission spectroscopy to characterize its atmosphere,” they wrote.

    More information: An independent discovery of two hot Jupiters from the K2 mission, arXiv:1603.01721 [astro-ph.EP] arxiv.org/abs/1603.01721.

    See the full article here .

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  • richardmitnick 5:08 pm on January 27, 2016 Permalink | Reply
    Tags: , , , Hot Jupiters   

    From AAS NOVA: “Hot Jupiters Aren’t As Lonely As We Thought” 


    American Astronomical Society

    27 January 2016
    Susanna Kohler

    Hot Jupiter orbiting one star in a binary system
    This median-stacked image, obtained with adaptive optics, shows one of the newly-discovered stellar companions to a star hosting a hot Jupiter. The projected separation is ~180 AU. [Ngo et al. 2015]

    The Friends of Hot Jupiters (FOHJ) project is a systematic search for planetary- and stellar-mass companions in systems that have known hot Jupiters — short-period, gas-giant planets. This survey has discovered that many more hot Jupiters may have companions than originally believed.

    Missing Friends

    FOHJ was begun with the goal of better understanding the systems that host hot Jupiters, in order to settle several longstanding issues.

    The first problem was one of observational statistics. We know that roughly half of the Sun-like stars nearby are in binary systems, yet we’ve only discovered a handful of hot Jupiters around binaries. Are binary systems less likely to host hot Jupiters? Or have we just missed the binary companions in the hot-Jupiter-hosting systems we’ve seen so far?

    An additional issue relates to formation mechanisms. Hot Jupiters probably migrated inward from where they formed out beyond the ice lines in protoplanetary disks — but how?

    Observations reveal two populations of hot Jupiters: those with circular orbits aligned with their hosts’ spins, and those with eccentric, misaligned orbits. The former population support a migration model dominated by local planet-disk interactions, whereas the latter population suggest the hot Jupiters migrated through dynamical interactions with distant companions. A careful determination of the companion rate in hot-Jupiter-hosting systems could help establish the ability of these two models to explain the observed populations.

    Search for Companions

    The FOHJ project began in 2012 and studied 51 systems hosting known, transiting hot Jupiters — with roughly half on circular, aligned orbits and half on eccentric, misaligned orbits. The survey consisted of three different, complementary components:

    Study 1
    Lead author: Heather Knutson (Caltech)
    Technique: Long-term radial velocity monitoring
    Searching for: Planetary companions at 1–20 AU from the star
    Study 2
    Lead author: Henry Ngo (Caltech)
    Technique: Adaptive optics imaging
    Searching for: Stellar companions at 50–2000 AU from the star
    Study 3
    Lead author: Danielle Piskorz (Caltech)
    Technique: Spectroscopy
    Searching for: Any additional stellar companions at <125 AU from the star

    Migration Implications

    Using these three different techniques, the team found a significant number of both planetary and stellar companions that had not been previously detected. After correcting their results for completeness, they found a multiple-star rate of ~50% for these systems, resolving the problem of the missing companions. So really, we just weren’t looking hard enough for the companions previously.

    Intriguingly, the binary companion rate found for these hot Jupiter systems is higher than the average rate for the field stars (which is below 25% for the semimajor-axis range the FOHJ studies are sensitive to). This suggests that companion stars may indeed play a role in hot Jupiter formation and migration.

    That said, none of the three studies found a significant difference in the binary fraction for aligned versus misaligned hot Jupiters — which means that the answer is not as simple as thought, with companion stars causing the misaligned planets. Thus, while hot Jupiters’ “friends” may play a role in their formation and migration, we still have work to do in understanding what that role is.


    Danielle Piskorz et al 2015 ApJ 814 148. doi:10.1088/0004-637X/814/2/148
    Henry Ngo et al 2015 ApJ 800 138. doi:10.1088/0004-637X/800/2/138
    Heather A. Knutson et al 2014 ApJ 785 126. doi:10.1088/0004-637X/785/2/126

    See the full article here .

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  • richardmitnick 10:02 am on December 31, 2015 Permalink | Reply
    Tags: , , , Hot Jupiters   

    From CFHT: “Hot Jupiters courting baby stars?” 

    CFHT icon
    Canada France Hawaii Telescope

    September 9th 2015 [Some CFHT articles were not properly made public. They promised to corect this.]

    Dr. Claire Moutou (CFHT, Hawaii)

    Dr. Lison Malo (CFHT, Hawaii)

    Dr. Jean-Francois Donati (IRAP, Toulouse, France)

    Temp 1
    Formation of stars and their planets in the Taurus nursery as seen at millimeter wavelengths by the APEX telescope in Chile (credits ESO/APEX)

    Although first detected 20 years ago, hot Jupiters are still enigmatic bodies. These celestial objects are giant Jupiter-like exoplanets that orbit 20 times closer to their host stars than the Earth does to the Sun. Using the ESPaDOnS spectro-polarimeter on the Canada-France-Hawaii Telescope, the Matysse(1) team led by Dr J.-F. Donati (Toulouse, CNRS) reports the preliminary evidence that a hot Jupiter orbits a 2-My star of the Taurus star forming region.

    CFHT ESPaDOns preferred

    This planet, yet to be confirmed, has a mass of 1.4 Jupiter mass and a 6-day period orbit and is unveiled by the gravitational pull it imprints on its star(2), once the stellar activity features are modeled. This discovery(3) could help us better understand how planetary systems like (or unlike) the solar system form and evolve into maturity. This could also be the first exoplanet ever revealed by CFHT, a nice introduction to the coming SPIRou(4) planet search survey.

    In our solar system, rocky planets like the Earth or Mars are found near the Sun whereas giant planets like Jupiter and Saturn orbit much further out. “Hence the surprise in 1995 when Mayor & Queloz first unveiled a giant planet sitting very close to its host star” says Dr C. Moutou, CNRS astronomer at CFHT and co-author of this new study. Since then, astronomers demonstrated that such planets must form in the outer regions of the protoplanetary disc, then migrate inwards and yet avoid falling into their host star. This could happen either very early in their lives, when still embedded within their primordial disc. Or much later, once multiple planets are formed and mutually interact in a rather unstable choreography – with some being pushed inwards at the immediate vicinity of their stars.

    An international team of astronomers led by Dr J.-F. Donati just secured preliminary evidence supporting the first of these two scenarios. Using ESPaDOnS, a spectropolarimeter built by IRAP / OMP for the CFHT, they looked at newly-born stars in the Taurus stellar nursery about 450 light-years away from us. They showed that the latest baby star they scrutinized, nicknamed V830 Tau, exhibits signatures that closely resemble those caused by a 1.4 Jupiter-mass planet orbiting 15 times closer to its host star than the Earth does to the Sun. This discovery, published in MNRAS, provides preliminary evidence that hot Jupiters may be extremely young and far more frequent around very young stars than around mature Sun-like stars.

    Although potentially very informative about planet formation, young stars are extremely challenging to observe. “Being enormously active and strongly magnetic, baby stars are covered with huge spots hundreds of times wider than those of our Sun, which generate perturbations in their spectra much larger than those caused by orbiting planets. As a result, their planets are quite tricky to detect, even in the case of hot Jupiters”, outlines E. Hebrard, PhD student at IRAP / OMP and co-author of the study. To address this issue, the team initiated the MaTYSSE survey aimed at mapping the surfaces of baby stars and at looking for the potential presence of hot Jupiters. “By monitoring these stars and using tomographic techniques inspired from medical imaging, we can unveil how dark and bright features are distributed across their surfaces, and how their magnetic fields expand into space. This modeling allows us to compensate for the perturbations that spots and fields generate in the spectra of young stars, and thus to regain the power of diagnosing the presence of close-in giant planets”, explains Dr G. Hussain (ESO, UFTMiP), co-author of the study. In the case of V830 Tau, the authors accurately modeled the surface field and spots in order to clean out their polluting effects, enabling them to discover the much weaker signal that hints at the presence of a giant planet. Although more data are required for a definite validation, this promising first result clearly demonstrates that the technique the team devised is powerful enough to solve the puzzling question of how hot Jupiters form. ” SPIRou, the new instrument currently built for CFHT by our team and scheduled for first light in 2017, will offer vastly superior performances thanks to its operation at near infrared wavelengths, at which young stars are far brighter, and will allow us to address this long-standing problem with unprecedented accuracy”, Dr J.-F. Donati concludes.

    ESPaDOnS observations of V830 Tau – a baby star in the Taurus nursery. Once the polluting effect of spots is removed, the residual shift of the spectrum (red dots and error bars) varies with time with a 6-day period. This spectral motion is compatible with that expected from a 1.4 Jupiter-mass planet orbiting at only 1/15 of the Sun-Earth distance (light blue curve). More densely-sampled observations are necessary to validate this preliminary result.

    Additional information

    • 1. Matysse (Magnetic Topologies of Young Stars and the Survival of close-in giant Exoplanets) is a CFHT Large Program started in 2013 with ESPaDOnS. Matysse is a collaboration led by J.F. Donati (IRAP, Obs Midi-Pyrenees, France) with astronomers from IPAG (Grenoble, F), ENS (Lyon, F), CEA (Saclay, F), LAM (Marseille, F), OCA (Nice, F), UdM (Montreal, C), UFMG (Belo Horizonte, B), ASIAA (Taipei, T), NAO (Beijing, C) and many associated scientists outside the CFHT community.
    • 2. The radial-velocity method uses the gravitational pull on the star by the planet modulated by its orbital motion, and measures the resulting spectral shift of the star with respect to the observer using the Doppler effect. This effect is of the order of 100 m/s for a hot Jupiter as the putative V 830 b and is repeatable at the period of the orbit – here, about 6 days.
    • 3. The full paper is accepted in the Monthly Notices of the Royal Astronomical Society (MNRAS, Oxford University Press); it is entitled: “Magnetic activity and hot Jupiters of young Suns: the weak-line T Tauri stars V819 Tau and V830 Tau”, by J.-F. Donati, E. Hebrard, G. Hussain, C. Moutou, L. Malo, K. Grankin, A. Vidotto, S. Alencar, S.G. Gregory, MM. Jardine, G. Herczeg, J. Morin, R. Fares, F. Menard, J. Bouvier, X. Delfosse, R. Doyon, M. Takami, P. Figueira, P. Petit, I. Boisse and the MaTYSSE collaboration, and is accessible here.
    • 4. SPIRou i is a near-infrared spectropolarimeter and a high-precision velocimeter optimized for both the detection of habitable Earth twins orbiting around nearby red dwarf stars, and the study of forming Sun-like stars and their planets. SPIRou is managed in the framework of an international consortium led by France and involving, in addition to the Canada-France-Hawaii Telescope (CFHT), Canada, Switzerland, Brazil, Taiwan and Portugal. The construction of SPIRou has started in 2015, with integration in Toulouse, France, scheduled for 2016 and first light at CFHT for 2017.

    See the full article here .

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    The CFH observatory hosts a world-class, 3.6 meter optical/infrared telescope. The observatory is located atop the summit of Mauna Kea, a 4200 meter, dormant volcano located on the island of Hawaii. The CFH Telescope became operational in 1979. The mission of CFHT is to provide for its user community a versatile and state-of-the-art astronomical observing facility which is well matched to the scientific goals of that community and which fully exploits the potential of the Mauna Kea site.

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  • richardmitnick 1:41 pm on December 14, 2015 Permalink | Reply
    Tags: , Hot Jupiters,   

    From Hubble: “NASA Space Telescopes Solve Missing Water Mystery in Comprehensive Survey of Exoplanets” 

    NASA Hubble Telescope


    December 14, 2015
    Ray Villard
    Space Telescope Science Institute, Baltimore, Maryland

    Mathias Jäger
    ESA/Hubble, Garching, Germany

    Whitney Clavin
    Jet Propulsion Laboratory, Pasadena, California

    Tim Stephens
    University of California, Santa Cruz, California

    David Sing
    University of Exeter, Exeter, United Kingdom

    Hannah Wakeford
    NASA Goddard Space Flight Center, Greenbelt, Maryland

    Jonathan Fortney
    University of California, Santa Cruz, California

    Artist’s Impression of “Hot Jupiter” Exoplanets – Annotated

    A survey of 10 hot, Jupiter-sized exoplanets conducted with NASA’s Hubble and Spitzer space telescopes has led a team to solve a long-standing mystery — why some of these worlds seem to have less water than expected.

    NASA Spitzer Telescope

    The findings offer new insights into the wide range of planetary atmospheres in our galaxy and how planets are assembled.

    Of the nearly 2,000 planets confirmed to be orbiting other stars, a subset are gaseous planets with characteristics similar to those of Jupiter but that orbit very close to their stars, making them blistering hot.

    Their close proximity to the star makes them difficult to observe in the glare of starlight. Due to this difficulty, Hubble has only explored a handful of hot Jupiters in the past. These initial studies have found several planets to hold less water than predicted by atmospheric models.

    The international team of astronomers has tackled the problem by making the largest-ever spectroscopic catalog of exoplanet atmospheres. All of the planets in the catalog follow orbits oriented so the planet passes in front of their parent star, as seen from Earth. During this so-called transit, some of the starlight travels through the planet’s outer atmosphere. “The atmosphere leaves its unique fingerprint on the starlight, which we can study when the light reaches us,” explained co-author Hannah Wakeford of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

    By combining data from NASA’s Hubble and Spitzer Space telescopes, the team was able to attain a broad spectrum of light covering wavelengths from the optical to infrared. The difference in planetary radius as measured between visible and infrared wavelengths was used to indicate the type of planetary atmosphere being observed for each planet in the sample, whether hazy or clear. A cloudy planet will appear larger in visible light than at infrared wavelengths, which penetrate deeper into the atmosphere. It was this comparison that allowed the team to find a correlation between hazy or cloudy atmospheres and faint water detection.

    “I’m really excited to finally see the data from this wide group of planets together, as this is the first time we’ve had sufficient wavelength coverage to compare multiple features from one planet to another,” said David Sing of the University of Exeter, United Kingdom, lead author of the paper. “We found the planetary atmospheres to be much more diverse than we expected.”

    “Our results suggest it’s simply clouds hiding the water from prying eyes, and therefore rule out dry hot Jupiters,” explained co-author Jonathan Fortney of the University of California, Santa Cruz. “The alternative theory to this is that planets form in an environment deprived of water, but this would require us to completely rethink our current theories of how planets are born.”

    The results are being published in the Dec. 14, 2015, issue of the British science journal Nature.

    The study of exoplanetary atmospheres is currently in its infancy. Hubble’s successor, the James Webb Space Telescope, will open a new infrared window on the study of exoplanets and their atmospheres.

    NASA Webb Telescope

    The science team comprises: D. Sing (University of Exeter, UK), J. Fortney (University of California, Santa Cruz), N. Nikolov, T. Kataria, and T. Evans (University of Exeter, UK), H. Wakeford (NASA/GSFC), S. Aigrain (University of Oxford, UK), G. Ballester (University of Arizona, Tucson), A. Burrows (Princeton University), D. Deming (University of Maryland, College Park), J.-M. Désert (University of Colorado, Boulder), N. Gibson (European Southern Observatory, Germany), G. Henry (Tennessee State University), C. Huitson (University of Colorado, Boulder), H. Knutson (California Institute of Technology), A. Lecavelier des Etangs (CNRS, Institut d’Astrophysique de Paris), F. Pont (University of Exeter, UK), A. Showman (University of Arizona, Tucson), A. Vidal-Madjar (CNRS, Institut d’Astrophysique de Paris), M. Williamson (Tennessee State University), and P. Wilson (CNRS, Institut d’Astrophysique de Paris).

    See the full article here .

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    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 12:12 pm on September 19, 2015 Permalink | Reply
    Tags: , , , Hot Jupiters   

    From Astronomy Now: “‘Hot Jupiter’ exoplanets may have formed very rapidly” 

    Astronomy Now bloc

    Astronomy Now

    18 September 2015
    No Writer Credit

    An artist’s impression of a gas giant planet in formation within the protoplanetary disc of a young star. Image credit: NASA/ JPL-Caltech.

    Twenty years after they were first discovered, hot Jupiters, gas giant planets that orbit very close to their star, are still enigmatic objects. Using the spectropolarimeter ESPaDOnS on the Canada-France-Hawaii Telescope [CFHT], an international team of astrophysicists led by Jean-François Donati (CNRS) has shown that such bodies may only take several million years to migrate close to their newly formed star.


    CFHT Telescope
    CFHT Interior

    The discovery should shed light on how solar systems like — or unlike — our own solar system form and evolve over the course of their existence. The work was recently published in Monthly Notices of the Royal Astronomical Society.

    In the solar system, rocky planets like the Earth and Mars are found near the Sun, whereas gas giant planets such as Jupiter and Saturn are further away. Hence the surprise of Michel Mayor and Didier Queloz when they discovered the very first exoplanet, exactly twenty years ago. This turned out to be a gas giant like Jupiter, but orbiting twenty times closer to its host star than the Earth does to the Sun.

    Since then, astronomers have shown that these future ‘hot Jupiters’ form in the outer regions of the protoplanetary disc, the cloud of dust and gas from which the central star and its surrounding planets are born, and then migrate inwards. It is when such gas giants get close to their star that they heat up and become hot Jupiters, unlike our own Jupiter, a cold gas giant which is five times further from the Sun than the Earth.

    But just when do these hot Jupiters migrate close to their host star? Until now, astronomers hypothesised two possible scenarios: the process might take place at a very early stage, when the young planets are still forming within the original disc, or else much later, once a number of planets have formed and interact in a choreography so unstable that some of them are flung inwards to the immediate vicinity of the central star.

    Part of the Taurus Molecular Cloud (TMC-1), a stellar nursery for the formation of stars and planets. Image credit: ESO/APEX (MPIfR/ESO/OSO) /A. Hacar et al./Digitized Sky Survey 2. Acknowledgment: Davide De Martin.


    Now, an international team of astrophysicists, including several French researchers and led by Jean-François Donati from the Institut de Recherche en Astrophysique et Planétologie (IRAP, CNRS/Université Toulouse III-Paul Sabatier), may have found evidence supporting the first of these scenarios. Using ESPaDOnS, a spectropolarimeter built by teams at IRAP for the Canada-France-Hawaii Telescope (CFHT), they observed stars in formation in a stellar nursery located in the constellation Taurus, some 450 light-years from the Earth. One of them, V830 Tau, exhibits signatures similar to those caused by a planet 1.4 times more massive than Jupiter, but orbiting 15 times closer to its star than the Earth does to the Sun. This discovery suggests that hot Jupiters may be extremely young and potentially far more frequently found around stars in formation than around mature stars like the Sun.

    Animation of sunspots on the young star V830, as reconstructed from ESPaDOnS observations. Image credit: Jean-Francois Donati et al. / MaTYSSE collaboration.

    Young stars are a mine of information about planetary formation. Due to their very intense activity and magnetic fields, they are covered with sunspots hundreds of times bigger than those on the Sun. These therefore generate perturbations in the star’s spectrum that are much greater than those caused by planets, making them much harder to detect, even when they are hot Jupiters.

    To overcome this problem, the team initiated the MaTYSSE (Magnetic Topologies of Young Stars and the Survival of close-in giant Exoplanets) survey aimed at mapping the surface of these stars and detecting the presence of any hot Jupiters.

    Magnetic field surrounding the young star V830, as reconstructed from ESPaDOnS observations. Image credit: Jean-Francois Donati et al. / MaTYSSE collaboration.

    By monitoring these young stars as they rotate and using tomographic techniques inspired from medical imaging, it is possible to reconstruct the distribution of dark and bright features on their surfaces, as well as the topology of the magnetic field. Modelling also makes it possible to correct the perturbations caused by this activity and thus detect the potential presence of hot Jupiters.

    In the case of V830 Tau, the authors were able to use this new technique to discover a hitherto hidden signal hinting at the presence of a giant planet. Although more data are required to validate the signal, this promising first result clearly demonstrates that the method used by the team can be the key to solving the puzzle of how hot Jupiters form.

    SPIRou, the new instrument being built by teams at IRAP for the CFHT and scheduled for first light in 2017, will push back the limits of this method, thanks to its ability to observe at infrared wavelengths, where young stars are much brighter.


    This will make it possible to explore the formation of stars and exoplanets in even greater detail.

    See the full article here .

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  • richardmitnick 9:31 am on November 21, 2014 Permalink | Reply
    Tags: , , , , , Hot Jupiters,   

    From Science Daily: “How to estimate the magnetic field of an exoplanet” 

    ScienceDaily Icon

    [Similar material to an earlier post; but a different slant.]

    Science Daily

    November 20, 2014
    Source: Lomonosov Moscow State University

    Scientists developed a new method which allows to estimate the magnetic field of a distant exoplanet, i.e., a planet, which is located outside the Solar system and orbits a different star. Moreover, they managed to estimate the value of the magnetic moment of the planet HD 209458b.The group of scientists including one of the researchers of the Lomonosov Moscow State University (Russia) published their article in the Science magazine.

    Size comparison of HD 209458 b with Jupiter.

    Artist’s interpretation of Planet HD 209458b. Scientists have now estimated the value of the magnetic moment of the planet HD 209458b.
    Credit: NASA/ESA/CNRS/Alfred Vidal-Madjar

    In the two decades which passed since the discovery of the first planet outside the Solar system, astronomers have made a great progress in the study of these objects. While 20 years ago a big event was even the discovery of a new planet, nowadays astronomers are able to consider their moons, atmosphere and climate and other characteristics similar to the ones of the planets in the Solar system. One of the important properties of both solid and gaseous planets is their possible magnetic field and its magnitude. On Earth it protects all the living creatures from the dangerous cosmic rays and helps animals to navigate in space.

    Kristina Kislyakova of the Space Research Institute of the Austrian Academy of Sciences in Graz together with an international group of physicists for the first time ever was able to estimate the value of the magnetic moment and the shape of the magnetosphere of the exoplanet HD 209458b. Maxim Khodachenko, a researcher at the Department of Radiation and computational methods of the Skobeltsyn Institute of Nuclear Physics of the Lomonosov Moscow State University, is also one of the authors of the article. He also works at the Space Research Institute of the Austrian Academy of Sciences.

    Planet HD 209458b (Osiris) is a hot Jupiter, approximately one third larger and lighter than Jupiter. It is a hot gaseous giant orbiting very close to the host star HD 209458. HD 209458b accomplishes one revolution around the host star for only 3.5 Earth days. It has been known to astronomers for a long time and is relatively well studied. In particular, it is the first planet where the atmosphere was detected. Therefore, for many scientists it has become a model object for the development of their hypotheses.

    Scientists used the observations of the Hubble Space Telescope of the HD 209458b in the hydrogen Lyman-alpha line at the time of transit, when the planet crosses the stellar disc as seen from Earth. At first, the scientists studied the absorption of the star radiation by the atmosphere of the planet. Afterwards they were able to estimate the shape of the gas cloud surrounding the hot Jupiter, and, based on these results, the size and the configuration of the magnetosphere.

    NASA Hubble Telescope
    NASA/ESA Hubble

    “We modeled the formation of the cloud of hot hydrogen around the planet and showed that only one configuration, which corresponds to specific values of the magnetic moment and the parameters of the stellar wind, allowed us to reproduce the observations,” explained Kristina Kislyakova.

    To make the model more accurate, scientists accounted for many factors that define the interaction between the stellar wind and the atmosphere of the planet: so-called charge exchange between the stellar wind and the neutral atmospheric particles and their ionization, gravitational effects, pressure, radiation acceleration, and the spectral line broadening.

    At present, scientists believe that the size of the atomic hydrogen envelope is defined by the interaction between the gas outflows from the planet and the incoming stellar wind protons. Similarly to Earth, the interaction of the atmosphere with the stellar wind occurs above the magnetosphere. By knowing the parameters of an atomic hydrogen cloud, one can estimate the size of the magnetosphere by means of a specific model.

    Since direct measurements of the magnetic field of exoplanets are currently impossible, the indirect methods are broadly used, for example, using the radio observations. There exist a number of attempts to detect the radio emission from the planet HD 209458b. However, because of the large distances the attempts to detect the radio emission from exoplanets have yet been unsuccessful.

    “The planet’s magnetosphere was relatively small being only 2.9 planetary radii corresponding to a magnetic moment of only 10% of the magnetic moment of Jupiter,” explained Kislyakova, a graduate of the Lobachevsky State University of Nizhny Novgorod. According to her, it is consistent with the estimates of the effectiveness of the planetary dynamo for this planet.

    “This method can be used for every planet, including Earth-like planets, if there exist an extended high energetic hydrogen envelope around them,” summarized Maxim Khodachenko.

    Journal Reference:

    K. G. Kislyakova, M. Holmstrom, H. Lammer, P. Odert, M. L. Khodachenko. Magnetic moment and plasma environment of HD 209458b as determined from Ly observations. Science, 2014; 346 (6212): 981 DOI: 10.1126/science.1257829

    See the full article here.

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  • richardmitnick 4:43 pm on November 20, 2014 Permalink | Reply
    Tags: , , , , Hot Jupiters,   

    From SPACE.com: “Unlocking the Secrets of an Alien World’s Magnetic Field” 

    space-dot-com logo


    November 20, 2014
    Charles Q. Choi

    The strength of an alien world’s magnetic field may have been deduced for the first time, by analyzing extraordinarily fast winds slamming against it from the planet’s star, researchers say.

    This research could help gauge the strength of other exoplanets‘ magnetic fields as well, scientists say.

    The magnetic field of a planet can influence its evolution in crucial ways. “It works as a shield against stellar wind particles, which erode the atmosphere, so it is important to know if this field is big or small,” said study lead author Kristina Kislyakova, a planetary scientist at the Austrian Academy of Sciences, in Graz.

    In order to find out magnetic details about exoplanets — planets beyond our own solar system — Kislyakova and her colleagues investigated HD 209458b, which orbits a sunlike star in the constellation Pegasus about 150 light-years from Earth. This alien world is only about 70 percent the mass of Jupiter, but nearly 40 percent wider.

    Size comparison of HD 209458 b with Jupiter.

    HD 209458b is a “hot Jupiter,” a gas giant that orbits its star closer than Mercury does to the sun — specifically, HD 209458b circles its star at a distance of less than one-twentieth the distance between the sun and Earth. The extraordinary roasting that HD 209458b endures makes its atmosphere blow away like the tail of a comet. Astronomers have informally dubbed the world “Osiris,” after the Egyptian god torn to pieces by his evil brother Set.

    Artist’s concept of an evaporating “hot Jupiter” exoplanet.
    Credit: NASA’s Goddard Space Flight Center

    The researchers used NASA’s Hubble Space Telescope to analyze the spectrum of light from HD 209458b as it passed in front of its star. Oddly, the data revealed hydrogen atoms moving away extremely quickly from the exoplanet in a lopsided manner.

    NASA Hubble Telescope
    NASA/ESA HUbble

    To help explain the unusual way in which the hydrogen is blowing off HD 209458b, the scientists built a 3D model to account for all the known interactions between planetary atmospheres and stellar winds, the flow of particles that stream off stars. The model suggested the exoplanet had a magnetic field about 10 percent as strong as Jupiter’s, and that the stellar wind blowing onto the planet was moving at about 895,000 mph (1.44 million km/h).

    “The implication of these findings is improvement of our understanding of the worlds outside the solar system — some new light shed on bodies many light-years away from us,” Kislyakova told Space.com.

    These findings support prior research suggesting that hot Jupiters have relatively weak magnetic fields compared with their cooler gas giant cousins. Since hot Jupiters orbit very near their stars, they experience powerful gravitational pulls that likely slow the rates at which these hot Jupiters spin. This slower rotation should result in weaker magnetic fields, because a planet’s magnetic field “is generated most effectively in fast-rotating cores of planets,” Kislyakova said.

    The scientists detailed their findings online today (Nov. 20) in the journal Science.

    See the full article here.

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