共查询到20条相似文献，搜索用时 62 毫秒
1.
Gaudi BS Bennett DP Udalski A Gould A Christie GW Maoz D Dong S McCormick J Szymanski MK Tristram PJ Nikolaev S Paczynski B Kubiak M Pietrzynski G Soszynski I Szewczyk O Ulaczyk K Wyrzykowski L;OGLE Collaboration Depoy DL Han C Kaspi S Lee CU Mallia F Natusch T Pogge RW Park BG;MuFUN Collaboration Abe F Bond IA Botzler CS Fukui A Hearnshaw JB Itow Y Kamiya K Korpela AV Kilmartin PM Lin W Masuda K Matsubara Y Motomura M Muraki Y Nakamura S Okumura T Ohnishi K Rattenbury NJ Sako T Saito T Sato S 《Science (New York, N.Y.)》2008,319(5865):927-930
Searches for extrasolar planets have uncovered an astonishing diversity of planetary systems, yet the frequency of solar system analogs remains unknown. The gravitational microlensing planet search method is potentially sensitive to multiple-planet systems containing analogs of all the solar system planets except Mercury. We report the detection of a multiple-planet system with microlensing. We identify two planets with masses of approximately 0.71 and approximately 0.27 times the mass of Jupiter and orbital separations of approximately 2.3 and approximately 4.6 astronomical units orbiting a primary star of mass approximately 0.50 solar mass at a distance of approximately 1.5 kiloparsecs. This system resembles a scaled version of our solar system in that the mass ratio, separation ratio, and equilibrium temperatures of the planets are similar to those of Jupiter and Saturn. These planets could not have been detected with other techniques; their discovery from only six confirmed microlensing planet detections suggests that solar system analogs may be common. 相似文献
2.
Boss AP 《Science (New York, N.Y.)》1995,267(5196):360-362
The sensitivities of astrometric and radial velocity searches for extrasolar planets are strongly dependent on planetary masses and orbits. Because most nearby stars are less massive than the sun, the first detection is likely to be of a Jupiter-mass planet orbiting a low-mass star, with a possible theoretical expectation being that Jupiter-like planets will be found much closer [inside the Earth-sun separation of 1 astronomical unit (AU)] to these low-luminosity stars than Jupiter is to the sun (5.2 AU). However, radiative hydrodynamic models of protoplanetary disks around low-mass stars (of 0.1 to 1 solar mass) show that Jupiter-like planets should form at distances (approximately 4 to 5 AU) that are only weakly dependent on the stellar mass. 相似文献
3.
Carter JA Agol E Chaplin WJ Basu S Bedding TR Buchhave LA Christensen-Dalsgaard J Deck KM Elsworth Y Fabrycky DC Ford EB Fortney JJ Hale SJ Handberg R Hekker S Holman MJ Huber D Karoff C Kawaler SD Kjeldsen H Lissauer JJ Lopez ED Lund MN Lundkvist M Metcalfe TS Miglio A Rogers LA Stello D Borucki WJ Bryson S Christiansen JL Cochran WD Geary JC Gilliland RL Haas MR Hall J Howard AW Jenkins JM Klaus T Koch DG Latham DW MacQueen PJ Sasselov D Steffen JH Twicken JD Winn JN 《Science (New York, N.Y.)》2012,337(6094):556-559
In the solar system, the planets' compositions vary with orbital distance, with rocky planets in close orbits and lower-density gas giants in wider orbits. The detection of close-in giant planets around other stars was the first clue that this pattern is not universal and that planets' orbits can change substantially after their formation. Here, we report another violation of the orbit-composition pattern: two planets orbiting the same star with orbital distances differing by only 10% and densities differing by a factor of 8. One planet is likely a rocky "super-Earth," whereas the other is more akin to Neptune. These planets are 20 times more closely spaced and have a larger density contrast than any adjacent pair of planets in the solar system. 相似文献
4.
Setiawan J Klement RJ Henning T Rix HW Rochau B Rodmann J Schulze-Hartung T 《Science (New York, N.Y.)》2010,330(6011):1642-1644
Stars in their late stage of evolution, such as horizontal branch stars, are still largely unexplored for planets. We detected a planetary companion around HIP 13044, a very metal-poor star on the red horizontal branch, on the basis of radial velocity observations with a high-resolution spectrograph at the 2.2-meter Max-Planck Gesellschaft-European Southern Observatory telescope. The star's periodic radial velocity variation of P = 16.2 days caused by the planet can be distinguished from the periods of the stellar activity indicators. The minimum mass of the planet is 1.25 times the mass of Jupiter and its orbital semimajor axis is 0.116 astronomical units. Because HIP 13044 belongs to a group of stars that have been accreted from a disrupted satellite galaxy of the Milky Way, the planet most likely has an extragalactic origin. 相似文献
5.
Wolszczan A 《Science (New York, N.Y.)》1994,264(5158):538-542
The discovery of two Earth-mass planets orbiting an old ( approximately 10(9) years), rapidly spinning neutron star, the 6.2-millisecond radio pulsar PSR B1257+12, was announced in early 1992. It was soon pointed out that the approximately 3:2 ratio of the planets' orbital periods should lead to accurately predictable and possibly measurable gravitational perturbations of their orbits. The unambiguous detection of this effect, after 3 years of systematic timing observations of PSR B1257+12 with the 305-meter Arecibo radiotelescope, as well as the discovery of another, moon-mass object in orbit around the pulsar, constitutes irrefutable evidence that the first planetary system around a star other than the sun has been identified. 相似文献
6.
In the past decade there has been a gradual, but substantial change in our understanding of the physical nature of (2060) Chiron. Once thought to be the first known member of a population of asteroids orbiting between Saturn and Uranus, Chiron is now generally regarded as the largest known comet. The detection of CN emission in the spectrum of Chiron is reported. Not only do these observations underscore the cometary nature of Chiron, but, at a heliocentric distance exceeding 11 astronomical units, represent the most distant detection yet of a neutral gas species common in comets. These results are consistent with the outgassing from Chiron being primarily driven by isolated outbursts of CO(2) from a very small fraction of Chiron's surface. These may be indicative of primordial inhomogeneities. 相似文献
7.
Perrin MD Graham JR Kalas P Lloyd JP Max CE Gavel DT Pennington DM Gates EL 《Science (New York, N.Y.)》2004,303(5662):1345-1348
We have used laser guide star adaptive optics and a near-infrared dual-channel imaging polarimeter to observe light scattered in the circumstellar environment of Herbig Ae/Be stars on scales of 100 to 300 astronomical units. We revealed a strongly polarized, biconical nebula 10 arc seconds (6000 astronomical units) in diameter around the star LkHalpha 198 and also observed a polarized jet-like feature associated with the deeply embedded source LkHalpha 198-IR. The star LkHalpha 233 presents a narrow, unpolarized dark lane consistent with an optically thick circumstellar disk blocking our direct view of the star. These data show that the lower-mass T Tauri and intermediate mass Herbig Ae/Be stars share a common evolutionary sequence. 相似文献
8.
Sincell M 《Science (New York, N.Y.)》2000,289(5482):1125
Last week at the International Astronomical Union 24th General Assembly, astronomers announced nine newly discovered planets orbiting other stars. The roster of extrasolar planets, now nearing 50, suggests that stars are fecund breeding grounds for worlds but that young planets must battle hordes of rivals for a handful of stable orbits. 相似文献
9.
Hubble Space Telescope imaging observations of two nearby brown dwarfs, DENIS-P J1228.2-1547 and Kelu 1, made with the near-infrared camera and multiobject spectrometer (NICMOS), show that the DENIS object is resolved into two components of nearly equal brightness with a projected separation of 0.275 arc second (5 astronomical units for a distance of 18 parsecs). This binary system will be able to provide the first dynamical measurement of the masses of two brown dwarfs in only a few years. Upper limits to the mass of any unseen companion in Kelu 1 yield a planet of 7 Jupiter masses aged 0. 5 x 10(9) years, which would have been detected at a separation larger than about 4 astronomical units. This example demonstrates that giant planets could be detected by direct imaging if they exist in Jupiter-like orbits around nearby young brown dwarfs. 相似文献
10.
A circumstellar disk has been observed optically around the fourth-magnitude star beta Pictoris. First detected in the infrared by the Infrared Astronomy Satellite last year, the disk is seen to extend to more than 400 astronomical units from the star, or more than twice the distance measured in the infrared by the Infrared Astronomy Satellite. The beta Pictoris disk is presented to Earth almost edgeon and is composed of solid particles in nearly coplanar orbits. The observed change in surface brightness with distance from the star implies that the mass density of the disk falls off with approximately the third power of the radius. Because the circumstellar material is in the form of a highly flattened disk rather than a spherical shell, it is presumed to be associated with planet formation. It seems likely that the system is relatively young and that planet formation either is occurring now around beta Pictoris or has recently been completed. 相似文献
11.
We present the discovery of a circumstellar dust disk surrounding AU Microscopii (AU Mic, GJ 803, HD 197481). This young M star at 10 parsec has the same age and origin as beta Pictoris, another nearby star surrounded by a dust disk. The AU Mic disk is detected between 50 astronomical units (AU) and 210 AU radius, a region where dust lifetimes exceed the present stellar age. Thus, AU Mic is the nearest star where we directly observe the solid material required for planet formation. Because 85% of stars are M-type, the AU Mic disk provides new clues on how the majority of planetary systems might form and evolve. 相似文献
12.
Nittler LR Starr RD Weider SZ McCoy TJ Boynton WV Ebel DS Ernst CM Evans LG Goldsten JO Hamara DK Lawrence DJ McNutt RL Schlemm CE Solomon SC Sprague AL 《Science (New York, N.Y.)》2011,333(6051):1847-1850
X-ray fluorescence spectra obtained by the MESSENGER spacecraft orbiting Mercury indicate that the planet's surface differs in composition from those of other terrestrial planets. Relatively high Mg/Si and low Al/Si and Ca/Si ratios rule out a lunarlike feldspar-rich crust. The sulfur abundance is at least 10 times higher than that of the silicate portion of Earth or the Moon, and this observation, together with a low surface Fe abundance, supports the view that Mercury formed from highly reduced precursor materials, perhaps akin to enstatite chondrite meteorites or anhydrous cometary dust particles. Low Fe and Ti abundances do not support the proposal that opaque oxides of these elements contribute substantially to Mercury's low and variable surface reflectance. 相似文献
13.
Weissman PR 《Science (New York, N.Y.)》1984,224(4652):987-989
The Infrared Astronomical Satellite (IRAS) science team has discovered a shell of particulate material around the star Vega. At the mean distance and temperature of the shell, the expected condensation products from a protostellar nebula would be dominated by frozen volatiles, in particular water ice. It is not possible to discriminate between dirty ice and silicate materials in the Vega shell on the basis of the IRAS data. The Vega shell is probably a ring of cometary bodies with an estimated minimum mass of 15 earth masses, analogous to one that has been hypothesized for the solar system. A possible hot inner shell around Vega may be an asteroid-like belt of material a few astronomical units from the star. 相似文献
14.
Interstellar dust grains intercepted by the dust detectors on the Ulysses and Galileo spacecrafts at heliocentric distances from 2 to 4 astronomical units show a deficit of grains with masses from 1 x 10(-17) to 3 x 10(-16) kilograms relative to grains intercepted outside 4 astronomical units. To divert grains out of the 2- to 4-astronomical unit region, the solar radiation pressure must be 1.4 to 1.8 times the force of solar gravity. These figures are consistent with the optical properties of spherical or elongated grains that consist of astronomical silicates or organic refractory material. Pure graphite grains with diameters of 0.2 to 0.4 micrometer experience a solar radiation pressure force as much as twice the force of solar gravity. 相似文献
15.
R Rebolo MRZ Osorio S Madruga VJS Bejar S Arribas J Licandro 《Science (New York, N.Y.)》1998,282(5392):1309-1312
A substellar-mass object in orbit at about 300 astronomical units from the young low-mass star G 196-3 was detected by direct imaging. Optical and infrared photometry and low- and intermediate-resolution spectroscopy of the faint companion, hereafter referred to as G 196-3B, confirm its cool atmosphere and allow its mass to be estimated at 25-10+15 Jupiter masses. The separation between the objects and their mass ratio suggest the fragmentation of a collapsing cloud as the most likely origin for G 196-3B, but alternatively it could have originated from a protoplanetary disc that has been dissipated. Whatever the formation process was, the young age of the primary star (about 100 million years) demonstrates that substellar companions can form on short time scales. 相似文献
16.
Comet Halley passed within 0.27 astronomical unit of Venus on 4 February 1986, 5 days before perihelion. This provided a unique opportunity to observe the comet's coma with the ultraviolet spectrometer orbiting the planet aboard the Pioneer Venus Orbiter spacecraft when the coma was otherwise obscured from Earth's view by the sun's glare. More than 9000 data points acquired systematically over the 5-day period from 2 to 6 February were combined to construct an excellent Lyman-alpha image of the hydrogen coma. The Lyman-alpha image was successfully reproduced with a comprehensive physical model, thereby verifying and documenting the underlying chemical kinetics and dynamics of the hydrogen coma. 相似文献
17.
Hart JE Toomre J Deane AE Hurlburt NE Glatzmaier GA Fichtl GH Leslie F Fowlis WW Gilman PA 《Science (New York, N.Y.)》1986,234(4772):61-64
Experiments on thermal convection in a rotating, differentially heated hemispherical shell with a radial buoyancy force were conducted in an orbiting microgravity laboratory. A variety of convective structures, or planforms, were observed, depending on the magnitude of the rotation and the nature of the imposed heating distribution. The results are compared with numerical simulations that can be conducted at the more modest heating rates, and suggest possible regimes of motion in rotating planets and stars. 相似文献
18.
The recent confirmation of the discovery of a satellite of the minor planet 532 Herculina indicates that other similar anomalous sightings are probably also due to satellites, which must therefore be numerous and commonplace. There are now 23 candidate satellites for eight minor planets, and no one of these minor planets occulting a star has failed to show evidence of at least one secondary event. Such companions are gravitationally stable but apparently have rapid tidal evolution rates. 相似文献
19.
Seven-millimeter continuum observations of a massive bipolar outflow source, G192.16-3.82, were made at a milli-arc-second resolution with a capability that links the National Radio Astronomy Observatory's Very Large Array radio interferometer with the Very Long Baseline Array antenna, located in Pie Town, New Mexico. The observations provide evidence for a true accretion disk that is about the size of our solar system and located around a massive star. A model of the radio emission suggests the presence of a binary protostellar system. The primary protostar, G192 S1, at the center of the outflow, with a protostar mass of about 8 to 10 times the solar mass, is surrounded by an accretion disk with a diameter of 130 astronomical units (AU). The mass of the disk is on the order of the protostar mass. The outflow is poorly collimated with a full opening angle of about 40 degrees; there is no indication of a more highly collimated jetlike component. The companion source, G192 S2, is located 80 AU north of the primary source. 相似文献
20.
Lagage PO Doucet C Pantin E Habart E Duchêne G Ménard F Pinte C Charnoz S Pel JW 《Science (New York, N.Y.)》2006,314(5799):621-623
Although planets are being discovered around stars more massive than the Sun, information about the proto-planetary disks where such planets have built up is sparse. We have imaged mid-infrared emission from polycyclic aromatic hydrocarbons at the surface of the disk surrounding the young intermediate-mass star HD 97048 and characterized the disk. The disk is in an early stage of evolution, as indicated by its large content of dust and its hydrostatic flared geometry, indicative of the presence of a large amount of gas that is well mixed with dust and gravitationally stable. The disk is a precursor of debris disks found around more-evolved A stars such as beta-Pictoris and provides the rare opportunity to witness the conditions prevailing before (or during) planet formation. 相似文献