Related papers: An Oort cloud origin of the Halley-type comets

The dynamical evolution of HII regions with and without stellar motion in dense, structured molecular clouds is studied. Clouds are modeled in hydrostatic equilibrium, with gaussian central cores and external halos that obey r**-2 and r**-3…

High-velocity clouds (HVCs) are multi-phase gas structures whose velocities (|v_LSR|>100 km/s) are too high to be explained by Galactic disk rotation. While large HVCs are well characterized, compact and small HVCs (with HI angular sizes of…

To date, at least three comets -- 2I/Borisov, C/2016 R2 (PanSTARRS), and C/2009 P1 (Garradd) -- have been observed to have unusually high CO concentrations compared to water. We attempt to explain these observations by modeling the effect…

Conventional narrowband photoelectric photometry of Comet Hale-Bopp (1995 O1) was obtained on 99 nights from mid-1995 to early-2000, yielding gas and dust production rates over an unprecedented range of time and distance. The appearance of…

We review the current state of knowledge of the long-term evolution of the small bodies that give rise to comets and exocomets, as well as their reservoirs. The active cometary phase is only transitory, and bodies that become comets pass…

The general picture that emerged by the end of 1990s from a large set of optical and X-ray, spectral and timing data was that the X-rays are produced in the innermost hot part of the accretion flow, while the optical/infrared (OIR) emission…

The nearly continuous stream of miniature comets dominated by the Kreutz sungrazers has been an unexpected bonanza for cometary science initiated by the launch of the Solar and Heliospheric Observatory (SOHO) in 1995. Over the nearly 30…

Surveys with the Spitzer and Herschel space observatories are now enabling the discovery and characterization of large samples of protostars in nearby molecular clouds, providing the observational basis for a detailed understanding of star…

We review the progress made in understanding molecular cloud formation and evolution toward star formation since the first Crete conference in 1990. It now seems clear that molecular clouds in the Galaxy at least form from compressed HI…

We present a study of the three forbidden oxygen lines [OI] located in the optical region (i.e., 5577.339 \r{A} (the green line), 6300.304 \r{A} and 6363.776 \r{A} (the two red lines)) in order to better understand the production of these…

An important tracer of the origin and evolution of cometary ices is the comparison with ices found in dense clouds and towards Young Stellar Objects (YSOs). We present a survey of ices in the 2-5 micron spectra of 23 massive YSOs, taken…

We present measurements, analyses and results for the seventeen strongly carbon-chain depleted comets in Lowell Observatory's narrowband photometry database. The majority of comets exhibit a very similar, i.e. typical, composition in…

X-ray emissions from cometary atmospheres were modeled from first principles using the charge-exchange interaction with solar wind ions as well as coherent scattering of solar X-rays from dust and ice grains. Scattering cross-sections were…

We present polarization images of Comet ISON (C/2012 S1) taken with the Hubble Space Telescope (HST) on UTC 2013 May 8 (rh = 3.81 AU, Delta = 4.34 AU), when the phase angle was alpha = 12.16 degrees. This phase angle is approximately…

Via joint analysis of a calibrated telescopic survey, which found scattering Kuiper Belt objects, and models of their expected orbital distribution, we measure the form of the scattering object's size distribution. Ruling out a single…

Filamentary molecular clouds are recognized as primary sites for the formation of stars. Specifically, regions characterized by the overlapping point of multiple filaments, known as hub regions, often associated with active star formation.…

We performed a monitoring observation of a Jupiter-Family comet, 17P/Holmes, during its 2014 perihelion passage to investigate its secular change in activity. The comet has drawn the attention of astronomers since its historic outburst in…

We present chemical evolution models of the Galactic disk with different Z-dependent yields. We find that a moderate mass loss rate for massive stars of solar metallicity produces an excellent fit to the observed C/H and C/O gradients of…

Black hole accretion flows can be divided into two broad classes: cold and hot. Cold accretion flows, which consist of cool optically thick gas, are found at relatively high mass accretion rates. Prominent examples are the standard thin…

We present first deep VLT-spectra of a new class of compact extraplanar objects located in the disk-halo interface of the edge-on spiral galaxy NGC55. Their spectra reveal continuum emission from stars and show typical emission-lines as…