The Experts below are selected from a list of 42648 Experts worldwide ranked by ideXlab platform
Yoshiko K Okamoto - One of the best experts on this subject based on the ideXlab platform.
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an early extrasolar planetary system revealed by planetesimal belts in β pictoris
2004Co-Authors: Yoshiko K Okamoto, Hirokazu Kataza, M Honda, Takuya Yamashita, Takashi Onaka, Junichi Watanabe, Takashi Miyata, Shigeyuki SakoAbstract:β Pictoris (β Pic) is a main-sequence star with an edge-on dust disk1,2,3 that might represent a state of the early Solar System. The dust does not seem to be a remnant from the original protoplanetary disk, but rather is thought to have been generated from large bodies like planetesimals and/or comets4,5. The history and composition of the parent bodies can therefore be revealed by determining the spatial distribution, grain size, composition and crystallinity of the dust through high-resolution mid-infrared observations. Here we report that the sub-micrometre amorphous silicate grains around β Pic have peaks in their distribution around 6, 16 and 30 au (1 au is the Sun–Earth Distance), whereas the crystalline and micrometre-sized amorphous silicate grains are concentrated in the disk centre. As sub-micrometre grains are blown quickly out from the system by radiation pressure from the central star, the peaks indicate the locations of ongoing dust replenishment, which originates from ring-like distributions of planetesimals or ‘planetesimal belts’.
D Queloz - One of the best experts on this subject based on the ideXlab platform.
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an extrasolar planetary system with three neptune mass planets
2006Co-Authors: Christophe Lovis, Jacques Laskar, Yann Alibert, Christoph Mordasini, M Mayor, F Bouchy, F. Pepe, W. Benz, A.c.m. Correia, D QuelozAbstract:Over the past two years, the search for low-mass extrasolar planets has led to the detection of seven so-called ‘hot Neptunes’ or ‘super-Earths’ around Sun-like stars. These planets have masses 5–20 times larger than the Earth and are mainly found on close-in orbits with periods of 2–15 days. Here we report a system of three Neptune-mass planets with periods of 8.67, 31.6 and 197 days, orbiting the nearby star HD 69830. This star was already known to show an infrared excess possibly caused by an asteroid belt within 1 au (the Sun–Earth Distance). Simulations show that the system is in a dynamically stable configuration. Theoretical calculations favour a mainly rocky composition for both inner planets, while the outer planet probably has a significant gaseous envelope surrounding its rocky/icy core; the outer planet orbits within the habitable zone of this star. As the techniques used to search for extrasolar planets have been refined, more and more have been discovered (over 170), and they get smaller. In recent years seven ‘hot Neptunes’ or ‘super-Earths’ have been detected. These have masses 5–20 times larger than the Earth and are in close-in orbits (periods of 2–15 days) around Sun-like stars. Now the first multiple system of three Neptune-mass planets has been found, with periods of 8.67, 31.6 and (in the ‘habitable’ zone) 197 days. They are orbiting the nearby star HD 69830. Theoretical calculations favour a mainly rocky composition for both inner planets. The outer planet probably has a significant gaseous envelope surrounding a rocky/icy core: it is the first Neptune-mass object detected inside the habitable zone of a Sun-like star. Simulations show that the system of three Neptune-mass planets is in a dynamically stable configuration, with theoretical calculations favouring a mainly rocky composition for both inner planets, but a significant gaseous envelope surrounding a rocky/icy core for the outer planet.
Christophe Lovis - One of the best experts on this subject based on the ideXlab platform.
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an extrasolar planetary system with three neptune mass planets
2006Co-Authors: Christophe Lovis, Jacques Laskar, Yann Alibert, Christoph Mordasini, M Mayor, F Bouchy, F. Pepe, W. Benz, A.c.m. Correia, D QuelozAbstract:Over the past two years, the search for low-mass extrasolar planets has led to the detection of seven so-called ‘hot Neptunes’ or ‘super-Earths’ around Sun-like stars. These planets have masses 5–20 times larger than the Earth and are mainly found on close-in orbits with periods of 2–15 days. Here we report a system of three Neptune-mass planets with periods of 8.67, 31.6 and 197 days, orbiting the nearby star HD 69830. This star was already known to show an infrared excess possibly caused by an asteroid belt within 1 au (the Sun–Earth Distance). Simulations show that the system is in a dynamically stable configuration. Theoretical calculations favour a mainly rocky composition for both inner planets, while the outer planet probably has a significant gaseous envelope surrounding its rocky/icy core; the outer planet orbits within the habitable zone of this star. As the techniques used to search for extrasolar planets have been refined, more and more have been discovered (over 170), and they get smaller. In recent years seven ‘hot Neptunes’ or ‘super-Earths’ have been detected. These have masses 5–20 times larger than the Earth and are in close-in orbits (periods of 2–15 days) around Sun-like stars. Now the first multiple system of three Neptune-mass planets has been found, with periods of 8.67, 31.6 and (in the ‘habitable’ zone) 197 days. They are orbiting the nearby star HD 69830. Theoretical calculations favour a mainly rocky composition for both inner planets. The outer planet probably has a significant gaseous envelope surrounding a rocky/icy core: it is the first Neptune-mass object detected inside the habitable zone of a Sun-like star. Simulations show that the system of three Neptune-mass planets is in a dynamically stable configuration, with theoretical calculations favouring a mainly rocky composition for both inner planets, but a significant gaseous envelope surrounding a rocky/icy core for the outer planet.
Joseph Harrington - One of the best experts on this subject based on the ideXlab platform.
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infrared radiation from an extrasolar planet
2005Co-Authors: Drake Deming, Sara Seager, Jeremy L Richardson, Joseph HarringtonAbstract:For the first time, light from a planet outside our Solar System has been detected on Earth. The planet is HD 209458b, previously identified by the wobble its gravity induces in its host star's orbit. It is slightly larger than Jupiter, but orbits its star at less than a twentieth of the Distance between the Earth and the Sun, making it a so-called ‘hot Jupiter’ planet. As HD 209458b passes behind the star, the amount of infrared light coming from the area drops slightly: that drop represents the planet's light contribution. A class of extrasolar giant planets—the so-called ‘hot Jupiters’ (ref. 1)—orbit within 0.05 au of their primary stars (1 au is the Sun–Earth Distance). These planets should be hot and so emit detectable infrared radiation2. The planet HD 209458b (refs 3, 4) is an ideal candidate for the detection and characterization of this infrared light because it is eclipsed by the star. This planet has an anomalously large radius (1.35 times that of Jupiter5), which may be the result of ongoing tidal dissipation6, but this explanation requires a non-zero orbital eccentricity (∼ 0.03; refs 6, 7), maintained by interaction with a hypothetical second planet. Here we report detection of infrared (24 µm) radiation from HD 209458b, by observing the decrement in flux during secondary eclipse, when the planet passes behind the star. The planet's 24-µm flux is 55 ± 10 µJy (1σ), with a brightness temperature of 1,130 ± 150 K, confirming the predicted heating by stellar irradiation2,8. The secondary eclipse occurs at the midpoint between transits of the planet in front of the star (to within ± 7 min, 1σ), which means that a dynamically significant orbital eccentricity is unlikely.
Shigeyuki Sako - One of the best experts on this subject based on the ideXlab platform.
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an early extrasolar planetary system revealed by planetesimal belts in β pictoris
2004Co-Authors: Yoshiko K Okamoto, Hirokazu Kataza, M Honda, Takuya Yamashita, Takashi Onaka, Junichi Watanabe, Takashi Miyata, Shigeyuki SakoAbstract:β Pictoris (β Pic) is a main-sequence star with an edge-on dust disk1,2,3 that might represent a state of the early Solar System. The dust does not seem to be a remnant from the original protoplanetary disk, but rather is thought to have been generated from large bodies like planetesimals and/or comets4,5. The history and composition of the parent bodies can therefore be revealed by determining the spatial distribution, grain size, composition and crystallinity of the dust through high-resolution mid-infrared observations. Here we report that the sub-micrometre amorphous silicate grains around β Pic have peaks in their distribution around 6, 16 and 30 au (1 au is the Sun–Earth Distance), whereas the crystalline and micrometre-sized amorphous silicate grains are concentrated in the disk centre. As sub-micrometre grains are blown quickly out from the system by radiation pressure from the central star, the peaks indicate the locations of ongoing dust replenishment, which originates from ring-like distributions of planetesimals or ‘planetesimal belts’.
