相关论文: Why did Comet 17P/Holmes burst out?

We extend an existing thermophysical activity model of comet 67P/Churyumov-Gerasimenko to include pressure buildup inside the pebbles making up the nucleus. We test various quantities of H$_{2}$O and CO$_{2}$, in order to simulate the…

New 21cm HI observations made with the Green Bank Telescope show that the high-velocity cloud known as Smith's Cloud has a striking cometary appearance and many indications of interaction with the Galactic ISM. The velocities of interaction…

The time dependence of the changes in the emission spectra of Comet 9P/Tempel 1 after Deep Impact are derived and discussed. This was a unique event because for the first time it gave astronomers the opportunity to follow the time history…

Jupiter-family comet (JFC) P/2021 HS (PANSTARRS) only exhibits a coma within a few weeks of its perihelion passage at 0.8~au, which is atypical for a comet. Here we present an investigation into the underlying cause using serendipitous…

Here we report that the activity of comet Hale--Bopp ceased between late 2007 and March, 2009, at about 28 AU distance from the Sun. At that time the comet resided at a distance from the Sun that exceeded the freeze-out distance of regular…

Cometary outgassing can produce torques that change the spin state of the nucleus, influencing the evolution and lifetimes of comets (1,2). If these torques spin up the rotation to the point that centripetal forces exceed the material…

We report a new imaging spectroscopic observation of Oort-cloud comet C/2017 K2 (hereafter K2) on its way to perihelion at 2.53 au, around a heliocentric distance where H2O ice begins to play a key role in comet activation. Normalized…

Comets are made of volatile and refractory material and naturally experience various degrees of sublimation as they orbit around the Sun. This gas release, accompanied by dust, represents what is traditionally described as activity.…

One of the least understood properties of comets is the compositional structure of their nuclei, which can either be homogeneous or heterogeneous. The nucleus structure can be conveniently studied at millimeter wavelengths, using…

We report JWST MIRI/MRS observations of the H2 S(1) 17.04 micron transition in two regions in the boundary of the Taurus Molecular Cloud. The two regions, denoted Edge (near the relatively sharp boundary of the 13CO J=1-0 emission) and Peak…

Comets are primitive objects that formed in the protoplanetary disk, and have been largely preserved over the history of the Solar System. However, they are not pristine, and surfaces of cometary nuclei do evolve. In order to understand the…

We present observations of the disintegrating long-period comet C/2019 J2 (Palomar) taken to determine the nature of the object and the cause of its demise. The data are consistent with break-up of a sub-kilometer nucleus into a debris…

We present Hubble Space Telescope observations of active asteroid 313P/Gibbs (formerly P/2014 S4) taken over the five month interval from 2014 October to 2015 March. This object has been recurrently active near perihelion (at 2.4 AU) in two…

The chemical composition of comets is frequently assumed to be directly provided by the observations of the abundances of volatile molecules in the coma. The present work aims to determine the relationship between the chemical composition…

While studying extraplanar neutral hydrogen in the disk-halo transition of the inner Galaxy we have discovered what appears to be a huge superbubble centered around l ~ 30 deg, whose top extends to latitudes > 25 deg at a distance of about…

Recent observations have detected molecular outflows in a few nearby starburst nuclei. We discuss the physical processes at work in such an environment in order to outline a scenario that can explain the observed parameters of the…

We have carried out a continuous multi-band photometric monitoring of the nuclear activity of comet 29P/Schwassmann-Wachmann 1 from 2008 to 2010. Our main aim has been to study the outburst mechanism on the basis of a follow-up of the…

The widespread detection of 60Fe in geological and lunar archives provides compelling evidence for recent nearby supernova explosions within $\sim 100$ pc around 3 Myr and 7 Myr ago. The blasts from these explosions had a profound effect on…

Intrinsically faint comets in nearly-parabolic orbits with perihelion distances much smaller than 1 AU exhibit strong propensity for suddenly disintegrating at a time not long before perihelion, as shown by Bortle (1991). Evidence from…

HI 21 cm observations with the NRAO 140 Foot telescope have revealed a giant HI cloud (G28.17+0.05) in the Galactic plane that has unusual properties. The cloud is 150 pc in diameter, is at a distance of 5 kpc, and contains as much as…