相关论文: Cometary Activity Begins at Kuiper Belt Distances:…

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…

We present observations showing in-bound long-period comet C/2017 K2 (PANSTARRS) to be active at record heliocentric distance. Nucleus temperatures are too low (60 K to 70 K) either for water ice to sublimate or for amorphous ice to…

Distant long-period comet C/2017 K2 has been outside the planetary region of the solar system for 3 Myr, negating the possibility that heat retained from the previous perihelion could be responsible for its activity. This inbound comet is…

We present a study of comet C/2017 K2 (PANSTARRS) using prediscovery archival data taken from 2013 to 2017. Our measurements show that the comet has been marginally increasing in activity since at least 2013 May (heliocentric distance of…

Recent observations show activity in long-period comet C/2017 K2 at heliocentric distances beyond the orbit of Uranus. With this as motivation, we constructed a simple model that takes a detailed account of gas transport modes and simulates…

Context. A comprehensive study of comets over a wide heliocentric distance range helps us understand the physical processes driving their activity and reveals compositional differences across dynamical groups. C/2017 K2 (PANSTARRS) is a…

C/2017 K2 (PANSTARRS) is an Oort cloud comet previously observed to be active at heliocentric distances r>20 au on what is likely its first passage through the inner solar system. We observed the comet on 2021 March 19-20 at r=6.82 au…

Comets, during their journeys into the inner solar system, deliver volatile gases, organics, and particulates into their comae that provide crucial information for assessing the physico-chemical conditions in the outer disk from which they…

The close encounter of Comet C/2013 A1 (Siding Spring) with Mars on October 19, 2014 presented an extremely rare opportunity to obtain the first flyby quality data of the nucleus and inner coma of a dynamically new comet. However, the…

The ESA Rosetta spacecraft, currently orbiting around comet 67P, has already provided in situ measurements of the dust grain properties from several instruments, particularly OSIRIS and GIADA. We propose adding value to those measurements…

Optical observations of the Oort cloud comet C/2017 K2 (PANSTARRS) show that its activity began at large heliocentric distances (up to 35 au), which cannot be explained by either the sublimation or the crystallization of water ice.…

We present initial observations of the interstellar body 2I/(2019 Q4) Borisov taken to determine its nature prior to the perihelion in 2019 December. Images from the Nordic Optical Telescope show a prominent, morphologically stable dust…

Photometric and spectroscopic observations of five nearly parabolic comets with eccentricity larger than 0.99 at heliocentric distances greater than 4 AU were performed. No molecular emission was observed for any studied comet and the…

Comets, relics from the early solar system, consist of dust and ice. The ice sublimates as comets approach the Sun, ejecting dust from their nuclei seen as activity. Different volatiles sublimate at different Sun-comet distances and eject…

Spectrophotometric monitoring of distant comet C/2002 VQ94 (LINEAR) was performed with the 6-m telescope of SAO RAS and with the 2.5-m Nordic Optical Telescope between 2008 and 2013. During this period the comet was on the outbound segment…

Comet C/2017 K2 (Pan-STARRS) provided a rare opportunity to investigate the evolution of coma composition and outgassing patterns over a transitional heliocentric distance (Rh) range where activity drivers in comets are thought to change…

We report a survey of molecular emission from cometary volatiles using the Atacama Large Millimeter/Submillimeter Array (ALMA) toward comet C/2017 K2 (PanSTARRS) carried out on UT 2022 September 21, 22, and 23 at a heliocentric distance…

We observed Comet C/Siding Spring using the Hubble Space Telescope (HST) during its close approach to Mars. The high spatial resolution images obtained through the F689M, F775W, and F845M filters reveal the characteristics of the dust coma.…

We present visible and mid-infrared imagery and photometry of temporary Jovian co-orbital comet P/2019 LD$_2$ taken with HST/WFC3, Spitzer/IRAC, the GROWTH telescope network, visible spectroscopy from Keck/LRIS and archival ZTF observations…

We present optical observations and Monte Carlo models of the dust coma, tail, and trail structures of comet 22P/Kopff during the 2002 and 2009 apparitions. Dust loss rates, ejection velocities, and power-law size distribution functions are…