Found 15 talks width keyword astrochemistry
Abstract
Understanding the composition and the nature of any asteroid approaching the Earth, and consequently potentially hazardous, is a matter of general interest, both scientific and practical. The potentially hazardous asteroid 1999 RQ36 is especially accessible to spacecraft and is the primary target of NASA's OSIRIS-REx sample return mission. Spectra of this asteroid point to the most primitive meteorites (CIs and CMs) as the most likely analogs. Asteroid (3200) Phaethon is also particularly interesting. Together with 2005 UD and 2001 YB5, is one of the only 3 near-Earth asteroids with associated meteor showers, which mostly come from comets. There is evidence of the presence of hydrated minerals on its surface, usually associated with organic material. Both asteroids are classified as "B". B-type asteroids are found mostly in the middle and outer main belt and are believed to be primitive and volatile-rich. We combine dynamical and spectral information to identify the most likely main-belt origin of these two objects.
IAC
Abstract
We present the new stellar population synthesis models based on the empirical stellar spectral library MILES, which can be regarded nowadays as standard in the field of stellar population studies. The synthetic SEDs cover the whole optical range at resolution 2.3 Å (FWHM). The unprecedented stellar parameter coverage of MILES allowed us to extend our model predictions from intermediate- to very-old age regimes, and the metallicity coverage from super-solar to [M/H] = -2.3. Observed spectra can be studied by means of full spectrum fitting or line-strengths. For the latter we propose a new Line Index System (LIS) to avoid the intrinsic uncertainties associated with the popular Lick/IDS system and provide more appropriate, uniform, spectral resolution. We present a web-page with a suite of on-line tools to facilitate the handling and transformation of the spectra. Online examples with practical applications to work with stellar spectra for a variety of instrumental setups will be shown. Furthermore we will also show examples of how to compute spectra and colors with varying instrumental setup, redshift and velocity dispersion for a suite of Star Formation Histories.
Abstract
Due to their orbits, near-Earth asteroids (NEAs) have been considered the most evident parent bodies of meteorites. Dynamical models show that NEAs come primarily from the inner and central parts of the Main Belt (MB), and they reach their orbits by means of gravitational resonances (mainly ?6 and 3:1). This part of the MB is dominated by spectral types S and Q, also the most common spectral types among the NEA population (~60%), and correspond to objects composed of silicates. Their reflectance spectra show very characteristic absorption bands that can be used to infer their mineralogical composition applying different methods of analysis. Those absorption bands are also present in the spectra of the most abundant class of meteorites (~80%), the ordinary chondrites (OC). In order to better understand the connection between MB asteroids, NEAs and OCs, we undertook a spectroscopic survey of asteroids between 2002 and 2007, using the telescopes and instrument facilities of "El Roque de los Muchachos" Observatory, in the Canary Islands. The survey contains visible and near-infrared spectra (0.5 - 2.5 µm) of a total of 105 asteroids. We have applied a method of mineralogical analysis based on spectral parameters to our sample of NEAs, and also to a sample of 91 MBs and 103 OCs obtained from different databases. We have found some significant compositional differences between NEAs, MBs and OCs. The most remarkable one is that NEAs compositionally differ from the whole set of OCs, and show a more olivine-rich composition, similar to what it is found for LL chondrites (only 8% of the falls). This result suggests that S type NEAs are not the immediate precursors of ordinary chondrites, as it was believed. We consider the size of the objects as the key factor to explain this difference. NEAs are km-sized objects, while meteorites are meter tocm sized objects. Combining the information obtained from the dynamical models and the drift in semimajor axis of the smaller objects due to their thermal intertia (Yarkovsky effect), we set out a possible scenario for the formation and the transport routes of NEAs and meteorites that could explain this compositional difference in a plausible way.
Abstract
There is a multitude of photochemical processes occurring in a planet's atmosphere. Some of these processes occur with an excess of energy and lead to products in the form of excited atoms, molecules and ions.In specific cases, these gases radiate at wavelengths that range from the UV to the NIR. Solar light is the ultimate cause of these airglow emissions, but traditionally one distinguishes between the day airglow (dayglow), and the night airglow (nightglow). The contribution of the Sun to the excitation of the emitting gas is more immediate in the day glow than in the nightglow. The airglow makes it possible to remotely investigate the chemical kinetics, energetic balance and dynamics of a planetary atmosphere. In the talk, I will go over some of the air glow missions that are known to exist in the atmospheres of the Earth, Mars and Venus. The examples illustrate some of my recent work, and include theoretical modelling and the interpretation of observational data. There is a long record of contributions to the nightglow from observations carried out at ground-based telescopes. I will briefly comment some of these.
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.<< First « Newer 1 | 2 Older »
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