Found 55 talks archived in Planetary systems
Abstract
Red Dwarf (dM) stars are the most numerous stars in our Galaxy. These faint, cool, long-lived, and low mass stars make up > 80% of all stars in the Universe. Determining the number of red dwarfs with planets and assessing planetary habitability (a planet’s potential to develop and sustain life) are critically important because such studies would indicate how common life is in the universe. Our program - "Living with a Red Dwarf" addresses these questions by investigating the long-term nuclear evolution and magnetic-dynamo coronal and chromospheric X-ray to Ultraviolet properties of red dwarf stars with widely different ages. The major focus of the program is to study the magnetic-dynamo generated X-ray-Ultraviolet emissions and flare properties of red dwarf stars from youth to old age. Emphasized are how the stellar X-UV emissions, flares & winds affect hosted planets and impact their habitability. We have developed age-rotation-activity relations and also are constructing irradiance tables (X-UV fluxes) that can be used to model the effects of X-UV radiation on planetary atmospheres and on possible life on nearby hosted planets. Despite the earlier pessimistic view that red dwarfs stars are not suitable for habitable planets - mainly because their low luminosities require a hosted planet to orbit quite close (r <0.3 AU) to be sufficiently warm to support life. Our initial results indicate that red dwarf stars (in particular the warmer dM stars) can indeed be suitable hosts for habitable planets capable of sustaining life for hundreds of billion years. Some examples of red dwarf stars currently known to host planets are discussed.
Abstract
The role of asteroids and comet impacts on the origin of Earth’s water and organic molecules is reviewed. Earth is believed to have formed dry, and magma oceans probably destroyed any primordial organics on Earth. The oldest clear evidence for water on Earth is about 3.85 Ga, right after the “Late Heavy Bombardment” (LHB). Asteroid and comet impacts during the LHB probably contributed significantly to Earth’s water and organic inventory. Evidence for this contribution is found in the D/H isotopic ratios of meteorites and comets. The abundance and variety of organic solids in asteroids and comets also point at a significant contribution to the organic inventory of the early Earth. However, the pieces of this puzzle do not all fit into a neat picture and several questions remain unanswered.
Abstract
The Infrared Spectrograph (IRS) on Spitzer has observed more than 120 asteroids, several Centaurs and Kuiper Belt objects (KBOs), and satellites of the giant planets. The asteroid sample includes objects from near-Earth space, through the Main Belt, and into the Jupiter Trojan swarms. Asteroids from all taxonomic classes have been observed, as have several binary and multiple component systems. The diameters of these targets range from a few hundred meters to a few hundred kilometers. On the whole, IRS has provided a broad sample of emissivity spectra of small Solar System bodies. The largest emissivity features detected are at the 10% level and are confined to the more primitive asteroid classes. Significant spectral variation is apparent among the IRS asteroid sample. Some of the dust observed in the close environment of other stars likely comes from asteroid collisions, so asteroids in the Solar System are proper mineralogical analogs. As capabilities continue to improve, direct observations of small body populations in other systems and inter-comparisons between systems will foster significant insights into the formation and evolution of planetary systems. The Solar System occupies a unique role by its accessibility and the detail to which it can be studied. While the IRS data are a good start, there is much to be learned from a larger set of mid-infrared spectra (e.g., from JWST and SOFIA). In this talk, I will present an overview of the IRS observations of small Solar System bodies, with a few representative objects highlighted for detailed discussion.
Abstract
Radar observation of near-Earth asteroids (NEAs) reveal the size, shape, spin characteristics of the population of small bodies near the Earth. Although spacecraft missions may give higher resolution images, they are infrequent and expensive. Only through ground based observations can we hope to understand the diverse population of NEAs. Radar imaging reveals surface features and shape at up to 7.5-m resolution. We see a surprising variety of object shapes, which tells us about their formation and evolution. Binary NEAs are easily detected using radar regardless of viewing geometry, the characteristics of which have led to new ideas about NEA evolution and internal structure. Craters and other surface concavities are often visible in radar images, unlike lightcurve-based shape models. Although opportunities to observe comets with radar are rare, more than ten comet nuclei have been detected to date, three with high resolution imaging. Radar observations have played an important role in a number of key areas in small body science, some of which will be discussed in this talk.
Abstract
The composition of the outer solar system is of particular interest because it holds the key to understanding the chemical evolution of the Solar System. Observations at the edge of the Solar System are difficult because of distance and size limitations. The Spitzer Space Telescope has provided a wealth of data for Kuiper Belt Objects (KBOs), the small inhabitants of this remote part of the Solar System past the orbit of Neptune, as well as for Centaurs, similar objects to the KBOs but with orbits that come closer to the Sun. Are these observations sufficient to tell us what the composition of these objects is? We briefly introduce spectral modeling, its strengths and limitations. Making use of synthetic surface reflectance spectra we assess the feasibility of determining the composition of Kuiper Belt Objects and Centaurs making use of Spitzer-IRAC data alone.Upcoming talks
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