37,444 research outputs found

    Prospects for detecting the Rossiter-McLaughlin effect of Earth-like planets: the test case of TRAPPIST-1b and c

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    The Rossiter-McLaughlin effect is the principal method of determining the sky-projected spin--orbit angle (β\beta) of transiting planets. Taking the example of the recently discovered TRAPPIST-1 system, we explore how ultracool dwarfs facilitate the measurement of the spin--orbit angle for Earth-sized planets by creating an effect that can be an order of magnitude more ample than the Doppler reflex motion caused by the planet if the star is undergoing rapid rotation. In TRAPPIST-1's case we expect the semi-amplitudes of the Rossiter-McLaughlin effect to be 40−5040-50 m/s for the known transiting planets. Accounting for stellar jitter expected for ultracool dwarfs, instrumental noise, and assuming radial velocity precisions both demonstrated and anticipated for upcoming near-infrared spectrographs, we quantify the observational effort required to measure the planets' masses and spin--orbit angles. We conclude that if the planetary system is well-aligned then β\beta can be measured to a precision of ≲10∘\lesssim 10^{\circ} if the spectrograph is stable at the level of 2 m/s. We also investigate the measure of Δβ\Delta \beta, the mutual inclination, when multiple transiting planets are present in the system. Lastly, we note that the rapid rotation rate of many late M-dwarfs will amplify the Rossiter-McLaughlin signal to the point where variations in the chromatic Rossiter-McLaughlin effect from atmospheric absorbers should be detectable.Comment: 11 pages, 4 figures. Accepted to MNRAS. Comments welcom

    The power of neural nets

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    Implementation of the Hopfield net which is used in the image processing type of applications where only partial information about the image may be available is discussed. The image classification type of algorithm of Hopfield and other learning algorithms, such as the Boltzmann machine and the back-propagation training algorithm, have many vital applications in space

    Impact processes in the Solar System: New understandings through numerical modeling

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    A collision of two rocky objects circling the sun in space, each roughly the size and mass of a large mountain range, was modeled. A fragmentation hydrocode was developed to perform dynamical computations of collisional outcomes. Explosive framentation and fluid dynamics were used and drawn together into a single application. To model a solid, certain material parameters, such as density, elasticity, rigidity, and energies of melting and vaporization were input. These parameters are well-known for a variety of important materials, such as ice, iron, granite, and basalt. Another important parameter used is the distribution of initial flaws within the material

    Calibration of the NASA-GSFC high energy cosmic ray experiment

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    Calibration of high energy cosmic ray experimen
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