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Stephen R. Kane - One of the best experts on this subject based on the ideXlab platform.
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the first Habitable Zone earth sized planet from tess ii spitzer confirms toi 700 d
arXiv: Earth and Planetary Astrophysics, 2020Co-Authors: Joseph E Rodriguez, Stephen R. Kane, Caroline V Morley, Andrew Vanderburg, Sebastian Zieba, Laura Kreidberg, Jason D Eastman, Alton Spencer, Samuel N Quinn, Ryan CloutierAbstract:We present $Spitzer$ 4.5$\mu$m observations of the transit of TOI-700 d, a Habitable Zone Earth-sized planet in a multiplanet system transiting a nearby M-dwarf star (TIC 150428135, 2MASS J06282325-6534456). TOI-700 d has a radius of $1.144^{+0.062}_{-0.061}R_\oplus$ and orbits within its host star's conservative Habitable Zone with a period of 37.42 days ($T_\mathrm{eq} \sim 269$K). TOI-700 also hosts two small inner planets (R$_b$=$1.037^{+0.065}_{-0.064}R_\oplus$ & R$_c$=$2.65^{+0.16}_{-0.15}R_\oplus$) with periods of 9.98 and 16.05 days, respectively. Our $Spitzer$ observations confirm the TESS detection of TOI-700 d and remove any remaining doubt that it is a genuine planet. We analyze the $Spitzer$ light curve combined with the 11 sectors of TESS observations and a transit of TOI-700 c from the LCOGT network to determine the full system parameters. Although studying the atmosphere of TOI-700 d is not likely feasible with upcoming facilities, it may be possible to measure the mass of TOI-700 d using state-of-the-art radial velocity instruments (expected RV semi-amplitude of $\sim$70 cm/s).
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the first Habitable Zone earth sized planet from tess ii spitzer confirms toi 700 d
The Astronomical Journal, 2020Co-Authors: Joseph E Rodriguez, Stephen R. Kane, Caroline V Morley, Andrew Vanderburg, Sebastian Zieba, Laura Kreidberg, Jason D Eastman, Alton Spencer, Samuel N Quinn, Ryan CloutierAbstract:We present Spitzer 4.5μm observations of the transit of TOI-700 d, a Habitable Zone Earth-sized planet in a multiplanet system transiting a nearby M-dwarf star (TIC 150428135, 2MASS J06282325-6534456). TOI-700 d has a radius of 1.220^(+0.073)_(−0.063) R_⊕ and orbits within its host star's conservative Habitable Zone with a period of 37.42 days (T_(eq) ∼269 K). TOI-700 also hosts two small inner planets (R_b = 1.044^(+0.065)_(−0.063) R_⊕ & R_c = 2.64^(+0.16)_(−0.14) R_⊕) with periods of 9.98 and 16.05 days, respectively. Our Spitzer observations confirm the TESS detection of TOI-700 d and remove any remaining doubt that it is a genuine planet. We analyze the Spitzer light curve combined with the 11 sectors of TESS observations and a transit of TOI-700 c from the LCOGT network to determine the full system parameters. With an expected RV semi-amplitude of ∼80 cm/s, it may be possible to measure the mass of TOI-700 d using state-of-the-art radial velocity instruments.
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Exploring giant planets and their potential moons in the Habitable Zone
2018Co-Authors: Michelle L., Hill, Stephen R. Kane, Dawn M. Gelino, Ravi Kumar Kopparapu, Eduardo Seperuelo Duarte, Robert A. WittenmyerAbstract:The recent discovery of a disturbance in the orbital period of a transiting exoplanet observed with the Kepler space telescope has provided the first observational hints of a giant satellite orbiting a planet, or an exomoon. The detection and study of exomoons offers new ways to understand the formation and evolution of planetary systems, and widens the search for signs of life out in the universe. This thesis thus provides proposed exoplanet target lists to search for detectable exomoons and perform more detailed follow-up studies. Improved orbital parameters compared to previous studies have been calculated to aid exomoon searches, and relevant Habitable Zone boundaries have been added. The list of planets has initially been refined to select exoplanets circular orbits contained within either the optimistic Habitable Zone (OHZ) or the conservative Habitable Zone (CHZ). Taking a giant planet mass to be 0.02MJ (Jupiter masses), 121 giant planets in the OHZ and 88 giant planets in the CHZ are found. The eccentricity of each planet’s orbit are then taken into account. In total 61 giant planets eccentric orbits have been found to remain in the OHZ while 26 giant planets eccentric orbits remain in the CHZ. Each of the 121 giant planets radial velocity curves are run through RadVel (Fulton et al. 2018) to confirm the orbital solution and look for linear trends to determine if there are indications for additional companions; potentially either additional planets in orbit or satellites. Of the 121 giant planets tested, 51 show indications of orbital companions. The potential exomoon properties of each giant planet have been calculated and tabulated for future imaging missions, with the results including the Hill radius, Roche limit and expected angular separation of any potentially detectable exomoon.
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a catalog of kepler Habitable Zone exoplanet candidates
The Astrophysical Journal, 2016Co-Authors: Stephen R. Kane, James F. Kasting, Ravi Kumar Kopparapu, David R. Ciardi, Michelle L., Hill, Elisa V., Quintana, Thomas, Barclay, Natalie M., Batalha, William J., Borucki, Nader HaghighipourAbstract:The NASA Kepler mission ha s discovered thousands of new planetary candidates, many of which have been confirmed through follow-up observations. A primary goal of the mission is to determine the occurrence rate of terrestrial-size planets within the Habitable Zone (HZ) of their host stars. Here we provide a list of HZ exoplanet candidates from the Kepler Q1–Q17 Data Release 24 data-vetting process. This work was undertaken as part of the Kepler HZ Working Group. We use a variety of criteria regarding HZ boundaries and planetary sizes to produce complete lists of HZ candidates, including a catalog of 104 candidates within the optimistic HZ and 20 candidates with radii less than two Earth radii within the conservative HZ. We cross-match our HZ candidates with the stellar properties and confirmed planet properties from Data Release 25 to provide robust stellar parameters and candidate dispositions. We also include false-positive probabilities recently calculated by Morton et al. for each of the candidates within our catalogs to aid in their validation. Finally, we performed dynamical analysis simulations for multi-planet systems that contain candidates with radii less than two Earth radii as a step toward validation of those systems.
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A Catalog of Kepler Habitable Zone Exoplanet Candidates
The Astrophysical Journal, 2016Co-Authors: Stephen R. Kane, James F. Kasting, Ravi Kumar Kopparapu, David R. Ciardi, Michelle L., Hill, Elisa V., Quintana, Thomas, Barclay, Natalie M., Batalha, William J., Borucki, Nader HaghighipourAbstract:The NASA Kepler mission has discovered thousands of new planetary candidates, many of which have been confirmed through follow-up observations. A primary goal of the mission is to determine the occurrance rate of terrestrial-size planets within the Habitable Zone (HZ) of their host stars. Here we provide a list of HZ exoplanet candidates from the Kepler Data Release 24 Q1-Q17 data vetting process. This work was undertaken as part of the Kepler Habitable Zone Working Group. We use a variety of criteria regarding HZ boundaries and planetary sizes to produce complete lists of HZ candidates, including a catalog of 104 candidates within the optimistic HZ and 20 candidates with radii less than two Earth radii within the conservative HZ. We cross-match our HZ candidates with the Data Release 25 stellar properties and confirmed planet properties to provide robust stellar parameters and candidate dispositions. We also include false positive probabilities recently calculated by Morton et al. (2016) for each of the candidates within our catalogs to aid in their validation. Finally, we performed dynamical analysis simulations for multi-planet systems that contain candidates with radii less than two Earth radii as a step toward validation of those systems.
Lisa Kaltenegger - One of the best experts on this subject based on the ideXlab platform.
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TESS Habitable Zone Star Catalog
The Astrophysical Journal, 2019Co-Authors: Lisa Kaltenegger, Joshua Pepper, Keivan G. Stassun, Ryan J. OelkersAbstract:We present the Transiting Exoplanet Survey Satellite (TESS) Habitable Zone Stars Catalog, a list of 1822 nearby stars with a TESS magnitude brighter than T = 12 and reliable distances from Gaia DR2, around which the NASA's TESS mission can detect transiting planets, which receive Earth-like irradiation. For all those stars TESS is sensitive down to 2 Earth radii transiting planets during one transit. For 408 stars TESS can detect such planets down to 1 Earth size during one transit. For 1690 stars, TESS has the sensitivity to detect planets down to 1.6 times Earth-size, a commonly used limit for rocky planets in the literature, receiving Earth-analog irradiation. We select stars from the TESS Candidate Target List, based on TESS Input Catalog Version 7. We update their distances using Gaia Data Release 2, and determine whether the stars will be observed for long enough during the 2 year prime mission to probe their Earth equivalent orbital distance for transiting planets. We discuss the subset of 227 stars for which TESS can probe the full extent of the Habitable Zone, the full region around a star out to about a Mars-equivalent orbit. Observing the TESS Habitable Zone Catalog Stars will also give us deeper insight into the occurrence rate of planets, out to Earth-analog irradiation as well as in the Habitable Zone, especially around cool stars. We present the stars by decreasing angular separation of the 1AU equivalent distance to provide insights into which stars to prioritize for ground-based follow-up observations with upcoming extremely large telescopes.
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A Methane Extension to the Classical Habitable Zone
The Astrophysical Journal, 2018Co-Authors: Ramses M. Ramirez, Lisa KalteneggerAbstract:The Habitable Zone (HZ) is the circumstellar region where standing bodies of liquid water could exist on the surface of a rocky planet. Conventional definitions assume that CO2 and H2O are the only greenhouse gases. The outer edge of this classical N2-CO2-H2O HZ extends out to nearly 1.7 AU in our solar system, beyond which condensation and scattering by CO2 outstrip its greenhouse capacity. We use a single column radiative-convective climate model to assess the greenhouse effect of CH4 (10 to about 100,000 ppm) on the classical Habitable Zone (N2-CO2-H2O) for main-sequence stars with stellar temperatures between 2,600 to 10,000 K (about A3 to M8). Assuming N2-CO2-H2O atmospheres, previous studies have shown that cooler stars more effectively heat terrestrial planets. However, we find that the addition of CH4 produces net greenhouse warming (tens of degrees) in planets orbiting stars hotter than a mid-K (about 4500K), whereas a prominent anti-greenhouse effect is noted for planets around cooler stars. We show that 10% CH4 can increase the width of the classical HZ of the hottest stars (TEFF = 10,000 K) by over 20%. In contrast, the CH4 anti-greenhouse can shrink the HZ for the coolest stars (TEFF = 2,600 K) by a similar percentage. We find that dense CO2-CH4 atmospheres near the outer edge of hotter stars may suggest inhabitance, highlighting the importance of including secondary greenhouse gases in alternative definitions of the HZ. We parameterize the limits of this N2-CO2-H2O-CH4 Habitable Zone and discuss implications in the search for extraterrestrial life.
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A Volcanic Hydrogen Habitable Zone
The Astrophysical Journal, 2017Co-Authors: Ramses M. Ramirez, Lisa KalteneggerAbstract:The classical Habitable Zone is the circular region around a star in which liquid water could exist on the surface of a rocky planet. The outer edge of the traditional N2-CO2-H2O Habitable Zone (HZ) extends out to nearly 1.7 AU in our Solar System, beyond which condensation and scattering by CO2 outstrips its greenhouse capacity. Here, we show that volcanic outgassing of atmospheric H2 on a planet near the outer edge can extend the Habitable Zone out to ~2.4 AU in our solar system. This wider volcanic hydrogen Habitable Zone (N2-CO2-H2O-H2) can be sustained as long as volcanic H2 output offsets its escape from the top of the atmosphere. We use a single-column radiative-convective climate model to compute the HZ limits of this volcanic hydrogen Habitable Zone for hydrogen concentrations between 1% and 50%, assuming diffusion-limited atmospheric escape. At a hydrogen concentration of 50%, the effective stellar flux required to support the outer edge decreases by ~35% to 60% for M to A stars. The corresponding orbital distances increase by ~30% to 60%. The inner edge of this HZ only moves out by ~0.1 to 4% relative to the classical HZ because H2 warming is reduced in dense H2O atmospheres. The atmospheric scale heights of such volcanic H2 atmospheres near the outer edge of the HZ also increase, facilitating remote detection of atmospheric signatures.
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a volcanic hydrogen Habitable Zone
The Astrophysical Journal, 2017Co-Authors: Ramses M. Ramirez, Lisa KalteneggerAbstract:The classical Habitable Zone (HZ) is the circular region around a star in which liquid water could exist on the surface of a rocky planet. The outer edge of the traditional N2–CO2–H2O HZ extends out to nearly ~1.7 au in our solar system, beyond which condensation and scattering by CO2 outstrips its greenhouse capacity. Here, we show that volcanic outgassing of atmospheric H2 can extend the outer edge of the HZ to ~2.4 au in our solar system. This wider volcanic-hydrogen HZ (N2–CO2–H2O–H2) can be sustained as long as volcanic H2 output offsets its escape from the top of the atmosphere. We use a single-column radiative-convective climate model to compute the HZ limits of this volcanic hydrogen HZ for hydrogen concentrations between 1% and 50%, assuming diffusion-limited atmospheric escape. At a hydrogen concentration of 50%, the effective stellar flux required to support the outer edge decreases by ~35%–60% for M–A stars. The corresponding orbital distances increase by ~30%–60%. The inner edge of this HZ only moves out ~0.1%–4% relative to the classical HZ because H2 warming is reduced in dense H2O atmospheres. The atmospheric scale heights of such volcanic H2 atmospheres near the outer edge of the HZ also increase, facilitating remote detection of atmospheric signatures.
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Water Planets in the Habitable Zone: Atmospheric Chemistry, Observable Features, and the case of Kepler-62e and -62f
The Astrophysical Journal, 2013Co-Authors: Lisa Kaltenegger, D. D. Sasselov, Sarah RugheimerAbstract:Planets composed of large quantities of water that reside in the Habitable Zone are expected to have distinct geophysics and geochemistry of their surfaces and atmospheres. We explore these properties motivated by two key questions: whether such planets could provide Habitable conditions and whether they exhibit discernable spectral features that distinguish a water-planet from a rocky Earth-like planet. We show that the recently discovered planets Kepler-62e and -62f are the first viable candidates for Habitable Zone water-planet. We use these planets as test cases for discussing those differences in detail. We generate atmospheric spectral models and find that potentially Habitable water-planets show a distinctive spectral fingerprint in transit depending on their position in the Habitable Zone.
Ian J M Crossfield - One of the best experts on this subject based on the ideXlab platform.
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water vapor and clouds on the Habitable Zone sub neptune exoplanet k2 18b
The Astrophysical Journal, 2019Co-Authors: Bjorn Benneke, Ian Wong, Caroline Piaulet, Heather A Knutson, Joshua Lothringer, Caroline V Morley, Ian J M Crossfield, Peter Gao, Thomas P Greene, Courtney D DressingAbstract:Results from the Kepler mission indicate that the occurrence rate of small planets (<3 R⊕) in the Habitable Zone of nearby low-mass stars may be as high as 80%. Despite this abundance, probing the conditions and atmospheric properties on any Habitable-Zone planet is extremely difficult and has remained elusive to date. Here, we report the detection of water vapor and the likely presence of liquid and icy water clouds in the atmosphere of the 2.6 R ⊕ Habitable-Zone planet K2-18b. The simultaneous detection of water vapor and clouds in the mid-atmosphere of K2-18b is particularly intriguing because K2-18b receives virtually the same amount of total insolation from its host star (1368^(+114)_(-107) W m⁻²) as the Earth receives from the Sun (1361 W m⁻²), resulting in the right conditions for water vapor to condense and explain the detected clouds. In this study we observed nine transits of K2-18b using Hubble Space Telescope/WFC3 in order to achieve the necessary sensitivity to detect the water vapor, and we supplement this data set with Spitzer and K2 observations to obtain a broader wavelength coverage. While the thick hydrogen-dominated envelope we detect on K2-18b means that the planet is not a true Earth analog, our observations demonstrate that low-mass Habitable-Zone planets with the right conditions for liquid water are accessible with state-of-the-art telescopes.
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water vapor and clouds on the Habitable Zone sub neptune exoplanet k2 18b
arXiv: Earth and Planetary Astrophysics, 2019Co-Authors: Bjorn Benneke, Ian Wong, Caroline Piaulet, Heather A Knutson, Joshua Lothringer, Caroline V Morley, Ian J M Crossfield, Peter Gao, Thomas P Greene, Courtney D DressingAbstract:Results from the Kepler mission indicate that the occurrence rate of small planets ($<3$ $R_\oplus$) in the Habitable Zone of nearby low-mass stars may be as high as 80%. Despite this abundance, probing the conditions and atmospheric properties on any Habitable-Zone planet is extremely difficult and has remained elusive to date. Here, we report the detection of water vapor and the likely presence of liquid and icy water clouds in the atmosphere of the $2.6$ $R_\oplus$ Habitable-Zone planet K2-18b. The simultaneous detection of water vapor and clouds in the mid-atmosphere of K2-18b is particularly intriguing because K2-18b receives virtually the same amount of total insolation from its host star ($1368_{-107}^{+114}$ W m$^{-2}$) as the Earth receives from the Sun (1361 W m$^{-2}$), resulting in the right conditions for water vapor to condense and explain the detected clouds. In this study, we observed nine transits of K2-18b using HST/WFC3 in order to achieve the necessary sensitivity to detect the water vapor, and we supplement this data set with Spitzer and K2 observations to obtain a broader wavelength coverage. While the thick hydrogen-dominated envelope we detect on K2-18b means that the planet is not a true Earth analog, our observations demonstrate that low-mass Habitable-Zone planets with the right conditions for liquid water are accessible with state-of-the-art telescopes.
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spitzer observations confirm and rescue the Habitable Zone super earth k2 18b for future characterization
The Astrophysical Journal, 2017Co-Authors: Bjorn Benneke, Heather A Knutson, Ian J M Crossfield, Courtney D Dressing, M W Werner, Erik A Petigura, Joshua E Schlieder, John H Livingston, Charles A BeichmanAbstract:The recent detections of two transit events attributed to the super-Earth candidate K2-18b have provided the unprecedented prospect of spectroscopically studying a Habitable-Zone planet outside the solar system. Orbiting a nearby M2.5 dwarf and receiving virtually the same stellar insolation as Earth, K2-18b would be a prime candidate for the first detailed atmospheric characterization of a Habitable-Zone exoplanet using the Hubble Space Telescope (HST)and James Webb Space Telescope (JWST). Here, we report the detection of a third transit of K2-18b near the predicted transit time using the Spitzer Space Telescope. The Spitzer detection demonstrates the periodic nature of the two transit events discovered by K2, confirming that K2-18 is indeed orbited by a super-Earth in a 33 day orbit, ruling out the alternative scenario of two similarly sized, long-period planets transiting only once within the 75 day Kepler Space Telescope (K2) observation. We also find, however, that the transit event detected by Spitzer occurred 1.85 hr ($7\sigma $) before the predicted transit time. Our joint analysis of the Spitzer and K2 photometry reveals that this early occurrence of the transit is not caused by transit timing variations, but the result of an inaccurate ephemeris due to a previously undetected data anomaly in the K2 photometry. We refit the ephemeris and find that K2-18b would have been lost for future atmospheric characterizations with HST and JWST if we had not secured its ephemeris shortly after the discovery. We caution that immediate follow-up observations as presented here will also be critical for confirming and securing future planets discovered by the Transiting Exoplanet Survey Satellite (TESS), in particular if only two transit events are covered by the relatively short 27-day TESS campaigns.
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spitzer observations confirm and rescue the Habitable Zone super earth k2 18b for future characterization
arXiv: Earth and Planetary Astrophysics, 2016Co-Authors: Bjorn Benneke, Heather A Knutson, Ian J M Crossfield, Courtney D Dressing, M W Werner, Erik A Petigura, Joshua E Schlieder, John H Livingston, Charles A BeichmanAbstract:The recent detections of two transit events attributed to the super-Earth candidate K2-18b have provided the unprecedented prospect of spectroscopically studying a Habitable-Zone planet outside the Solar System. Orbiting a nearby M2.5 dwarf and receiving virtually the same stellar insolation as Earth, K2-18b would be a prime candidate for the first detailed atmospheric characterization of a Habitable-Zone exoplanet using HST and JWST. Here, we report the detection of a third transit of K2-18b near the predicted transit time using the Spitzer Space Telescope. The Spitzer detection demonstrates the periodic nature of the two transit events discovered by K2, confirming that K2-18 is indeed orbited by a super-Earth in a 33-day orbit and ruling out the alternative scenario of two similarly-sized, long-period planets transiting only once within the 75-day K2 observation. We also find, however, that the transit event detected by Spitzer occurred 1.85 hours (7-sigma) before the predicted transit time. Our joint analysis of the Spitzer and K2 photometry reveals that this early occurrence of the transit is not caused by transit timing variations (TTVs), but the result of an inaccurate K2 ephemeris due to a previously undetected data anomaly in the K2 photometry likely caused by a cosmic ray hit. We refit the ephemeris and find that K2-18b would have been lost for future atmospheric characterizations with HST and JWST if we had not secured its ephemeris shortly after the discovery. We caution that immediate follow-up observations as presented here will also be critical in confirming and securing future planets discovered by TESS, in particular if only two transit events are covered by the relatively short 27-day TESS campaigns.
Jon M. Jenkins - One of the best experts on this subject based on the ideXlab platform.
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discovery and validation of kepler 452b a 1 6 r super earth exoplanet in the Habitable Zone of a g2 star
The Astronomical Journal, 2015Co-Authors: Jon M. Jenkins, Natalie M., Batalha, David W Latham, Michael Endl, Joseph D Twicken, Douglas A Caldwell, William D Cochran, Gilbert A EsquerdoAbstract:We report on the discovery and validation of Kepler-452b, a transiting planet identified by a search through the 4 years of data collected by NASA's Kepler Mission. This possibly rocky 1.63_(-0.20)^(+0.23) R⨁ planet orbits its G2 host star every 384.843_(-0.012)^(+0.007) days, the longest orbital period for a small (R_p < 2 R⨁) transiting exoplanet to date. The likelihood that this planet has a rocky composition lies between 49% and 62%. The star has an effective temperature of 5757 ± 85 K and a log g of 4.32 ± 0.09. At a mean orbital separation of 1.046_(-0.015)^(+0.019) AU, this small planet is well within the optimistic Habitable Zone of its star (recent Venus/early Mars), experiencing only 10% more flux than Earth receives from the Sun today, and slightly outside the conservative Habitable Zone (runaway greenhouse/maximum greenhouse). The star is slightly larger and older than the Sun, with a present radius of 1.11_(-0.09)^(+0.15) R⨁ and an estimated age of ~6 Gyr. Thus, Kepler-452b has likely always been in the Habitable Zone and should remain there for another ~3 Gyr.
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a super earth sized planet orbiting in or near the Habitable Zone around a sun like star
The Astrophysical Journal, 2013Co-Authors: Thomas, Barclay, Christopher J. Burke, Steve B. Howell, Jason F. Rowe, Daniel Huber, Howard Isaacson, Jon M. JenkinsAbstract:We present the discovery of a super-Earth-sized planet in or near the Habitable Zone of a Sun-like star. The host is Kepler-69, a 13.7 mag G4V-type star. We detect two periodic sets of transit signals in the 3-year flux time series of Kepler-69, obtained with the Kepler spacecraft. Using the very high precision Kepler photometry, and follow-up observations, our confidence that these signals represent planetary transits is >99.3%. The inner planet, Kepler-69b, has a radius of 2.24^(+0.44)_(-0.29) R_⊕ and orbits the host star every 13.7 days. The outer planet, Kepler-69c, is a super-Earth-sized object with a radius of 1.7^(+0.34)_(-0.23) R_⊕ and an orbital period of 242.5 days. Assuming an Earth-like Bond albedo, Kepler-69c has an equilibrium temperature of 299 ± 19 K, which places the planet close to the Habitable Zone around the host star. This is the smallest planet found by Kepler to be orbiting in or near the Habitable Zone of a Sun-like star and represents an important step on the path to finding the first true Earth analog.
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A super-Earth-sized planet orbiting in or near the Habitable Zone around Sun-like star
The Astrophysical Journal, 2013Co-Authors: Thomas, Barclay, Christopher J. Burke, Steve B. Howell, Jason F. Rowe, Daniel Huber, Howard Isaacson, Jon M. Jenkins, Rea Kolbl, Geoffrey W. Marcy, Elisa V., QuintanaAbstract:We present the discovery of a super-earth-sized planet in or near the Habitable Zone of a sun-like star. The host is Kepler-69, a 13.7 mag G4V-type star. We detect two periodic sets of transit signals in the three-year flux time series of Kepler-69, obtained with the Kepler spacecraft. Using the very high precision Kepler photometry, and follow-up observations, our confidence that these signals represent planetary transits is >99.1%. The inner planet, Kepler-69b, has a radius of 2.24+/-0.4 Rearth and orbits the host star every 13.7 days. The outer planet, Kepler-69c, is a super-Earth-size object with a radius of 1.7+/-0.3 Rearth and an orbital period of 242.5 days. Assuming an Earth-like Bond albedo, Kepler-69c has an equilibrium temperature of 299 +/- 19 K, which places the planet close to the Habitable Zone around the host star. This is the smallest planet found by Kepler to be orbiting in or near Habitable Zone of a Sun-like star and represents an important step on the path to finding the first true Earth analog.
Bjorn Benneke - One of the best experts on this subject based on the ideXlab platform.
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water vapor and clouds on the Habitable Zone sub neptune exoplanet k2 18b
The Astrophysical Journal, 2019Co-Authors: Bjorn Benneke, Ian Wong, Caroline Piaulet, Heather A Knutson, Joshua Lothringer, Caroline V Morley, Ian J M Crossfield, Peter Gao, Thomas P Greene, Courtney D DressingAbstract:Results from the Kepler mission indicate that the occurrence rate of small planets (<3 R⊕) in the Habitable Zone of nearby low-mass stars may be as high as 80%. Despite this abundance, probing the conditions and atmospheric properties on any Habitable-Zone planet is extremely difficult and has remained elusive to date. Here, we report the detection of water vapor and the likely presence of liquid and icy water clouds in the atmosphere of the 2.6 R ⊕ Habitable-Zone planet K2-18b. The simultaneous detection of water vapor and clouds in the mid-atmosphere of K2-18b is particularly intriguing because K2-18b receives virtually the same amount of total insolation from its host star (1368^(+114)_(-107) W m⁻²) as the Earth receives from the Sun (1361 W m⁻²), resulting in the right conditions for water vapor to condense and explain the detected clouds. In this study we observed nine transits of K2-18b using Hubble Space Telescope/WFC3 in order to achieve the necessary sensitivity to detect the water vapor, and we supplement this data set with Spitzer and K2 observations to obtain a broader wavelength coverage. While the thick hydrogen-dominated envelope we detect on K2-18b means that the planet is not a true Earth analog, our observations demonstrate that low-mass Habitable-Zone planets with the right conditions for liquid water are accessible with state-of-the-art telescopes.
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water vapor and clouds on the Habitable Zone sub neptune exoplanet k2 18b
arXiv: Earth and Planetary Astrophysics, 2019Co-Authors: Bjorn Benneke, Ian Wong, Caroline Piaulet, Heather A Knutson, Joshua Lothringer, Caroline V Morley, Ian J M Crossfield, Peter Gao, Thomas P Greene, Courtney D DressingAbstract:Results from the Kepler mission indicate that the occurrence rate of small planets ($<3$ $R_\oplus$) in the Habitable Zone of nearby low-mass stars may be as high as 80%. Despite this abundance, probing the conditions and atmospheric properties on any Habitable-Zone planet is extremely difficult and has remained elusive to date. Here, we report the detection of water vapor and the likely presence of liquid and icy water clouds in the atmosphere of the $2.6$ $R_\oplus$ Habitable-Zone planet K2-18b. The simultaneous detection of water vapor and clouds in the mid-atmosphere of K2-18b is particularly intriguing because K2-18b receives virtually the same amount of total insolation from its host star ($1368_{-107}^{+114}$ W m$^{-2}$) as the Earth receives from the Sun (1361 W m$^{-2}$), resulting in the right conditions for water vapor to condense and explain the detected clouds. In this study, we observed nine transits of K2-18b using HST/WFC3 in order to achieve the necessary sensitivity to detect the water vapor, and we supplement this data set with Spitzer and K2 observations to obtain a broader wavelength coverage. While the thick hydrogen-dominated envelope we detect on K2-18b means that the planet is not a true Earth analog, our observations demonstrate that low-mass Habitable-Zone planets with the right conditions for liquid water are accessible with state-of-the-art telescopes.
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spitzer observations confirm and rescue the Habitable Zone super earth k2 18b for future characterization
The Astrophysical Journal, 2017Co-Authors: Bjorn Benneke, Heather A Knutson, Ian J M Crossfield, Courtney D Dressing, M W Werner, Erik A Petigura, Joshua E Schlieder, John H Livingston, Charles A BeichmanAbstract:The recent detections of two transit events attributed to the super-Earth candidate K2-18b have provided the unprecedented prospect of spectroscopically studying a Habitable-Zone planet outside the solar system. Orbiting a nearby M2.5 dwarf and receiving virtually the same stellar insolation as Earth, K2-18b would be a prime candidate for the first detailed atmospheric characterization of a Habitable-Zone exoplanet using the Hubble Space Telescope (HST)and James Webb Space Telescope (JWST). Here, we report the detection of a third transit of K2-18b near the predicted transit time using the Spitzer Space Telescope. The Spitzer detection demonstrates the periodic nature of the two transit events discovered by K2, confirming that K2-18 is indeed orbited by a super-Earth in a 33 day orbit, ruling out the alternative scenario of two similarly sized, long-period planets transiting only once within the 75 day Kepler Space Telescope (K2) observation. We also find, however, that the transit event detected by Spitzer occurred 1.85 hr ($7\sigma $) before the predicted transit time. Our joint analysis of the Spitzer and K2 photometry reveals that this early occurrence of the transit is not caused by transit timing variations, but the result of an inaccurate ephemeris due to a previously undetected data anomaly in the K2 photometry. We refit the ephemeris and find that K2-18b would have been lost for future atmospheric characterizations with HST and JWST if we had not secured its ephemeris shortly after the discovery. We caution that immediate follow-up observations as presented here will also be critical for confirming and securing future planets discovered by the Transiting Exoplanet Survey Satellite (TESS), in particular if only two transit events are covered by the relatively short 27-day TESS campaigns.
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spitzer observations confirm and rescue the Habitable Zone super earth k2 18b for future characterization
arXiv: Earth and Planetary Astrophysics, 2016Co-Authors: Bjorn Benneke, Heather A Knutson, Ian J M Crossfield, Courtney D Dressing, M W Werner, Erik A Petigura, Joshua E Schlieder, John H Livingston, Charles A BeichmanAbstract:The recent detections of two transit events attributed to the super-Earth candidate K2-18b have provided the unprecedented prospect of spectroscopically studying a Habitable-Zone planet outside the Solar System. Orbiting a nearby M2.5 dwarf and receiving virtually the same stellar insolation as Earth, K2-18b would be a prime candidate for the first detailed atmospheric characterization of a Habitable-Zone exoplanet using HST and JWST. Here, we report the detection of a third transit of K2-18b near the predicted transit time using the Spitzer Space Telescope. The Spitzer detection demonstrates the periodic nature of the two transit events discovered by K2, confirming that K2-18 is indeed orbited by a super-Earth in a 33-day orbit and ruling out the alternative scenario of two similarly-sized, long-period planets transiting only once within the 75-day K2 observation. We also find, however, that the transit event detected by Spitzer occurred 1.85 hours (7-sigma) before the predicted transit time. Our joint analysis of the Spitzer and K2 photometry reveals that this early occurrence of the transit is not caused by transit timing variations (TTVs), but the result of an inaccurate K2 ephemeris due to a previously undetected data anomaly in the K2 photometry likely caused by a cosmic ray hit. We refit the ephemeris and find that K2-18b would have been lost for future atmospheric characterizations with HST and JWST if we had not secured its ephemeris shortly after the discovery. We caution that immediate follow-up observations as presented here will also be critical in confirming and securing future planets discovered by TESS, in particular if only two transit events are covered by the relatively short 27-day TESS campaigns.