A Molecular Survey of Comet C/1995 O1 (Hale-Bopp) at the IRAM Telescopes     

Bockelée-Morvan  D.  Wink  J.  Despois  D.  Colom  P.  Biver  N.  Crovisier  J.  Gautier  D.  Gérard  E.  Lellouch  E.  Moreno  R.  Paubert  G.  Rauer  H.  Davies  J. K.  Dent  W. R. F. 《Earth, Moon, and Planets》1997,78(1-3):67-67

Spectroscopic observations of comet Hale-Boppwere undertaken near perihelion at millimetre wavelengths with the Institut de Radioastronomie Millimétrique (IRAM) telescopes at Plateau de Bure (France)and Pico Veleta (Spain). They resulted in the first detections of HCOOH,SO₂, NH₂CHO and HCOOCH₃ in a comet. HDO was detected through its3₁₂–2₂₁ line at 225.897 GHz,complementing the observation of the 1₀₁–0₀₀ line at 464.925 GHz at the James Clerk Maxwell Telescope (Meier et al., 1998,Science 279, 842).Several unidentified lines are present in the spectra. Observations of HC₃N, HNCO, OCS, SO, CN, CO₊, HCO₊, in addition to more ‘classical’species CO, HCN, HNC, CH₃CN, CH₃OH, H₂CO, CS and H₂S (Biveret al., this issue) permit us to make out an extensive inventory of the composition of the coma of comet Hale-Bopp at its perihelion. It presents strong analogies with gas-phase abundances measured in interstellar hot cores and bipolar flows, which are believed to reflect the composition of interstellar grains. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

A Synthetic Interdisciplinary “Chronological Frieze”: an Attempt     

Didier Despois  Muriel Gargaud 《Earth, Moon, and Planets》2006,98(1-4):291-297

This chapter introduces the chronological and interdisciplinary “frieze” which presents the main events relevant (in our opinion) to the problem of the emergence of life on Earth. This selection of events is directly connected to the previous chapters of this book.The frieze may be found in print as an insert at the back of the print publication. This supplementary material is also available in the online version of this article at and is accesssible for authorized users.  相似文献   

Long-term Evolution of the Outgassing of Comet Hale-Bopp From Radio Observations   总被引：1，自引：0，他引：1  

Biver  N.  Bockelée-Morvan  D.  Colom  P.  Crovisier  J.  Germain  B.  Lellouch  E.  Davies  J. K.  Dent  W. R. F.  Moreno  R.  Paubert  G.  Wink  J.  Despois  D.  Lis  D. C.  Mehringer  D.  Benford  D.  Gardner  M.  Phillips  T. G.  Gunnarsson  M.  Rickman  H.  Winnberg  A.  Bergman  P.  Johansson  L. E. B.  Rauer  H. 《Earth, Moon, and Planets》1997,78(1-3):5-11

C/1995 O1 (Hale-Bopp) has been observed on a regular basis since August 1995 at millimetre and submillimetre wavelengths using IRAM, JCMT, CSO and SEST radio telescopes. The production rates of eight molecular species (CO, HCN, CH₃OH, H₂CO,H₂S, CS, CH₃CN,HNC) have been monitored as a function of heliocentric distance(r_h from 7 AU pre-perihelion to 4 AU post-perihelion. As comet Hale-Bopp approached and receded from the Sun, these species displayed different behaviours. Far from the Sun, the most volatile species were found in general relatively more abundant in the coma. In comparison to other species, HNC, H₂CO and CS showed a much steeper increase of the production rate with decreasing r_h. Less than 1.5 AU from the Sun, the relative abundances were fairly stable and approached those found in other comets near 1 AU. The kinetic temperature of the coma, estimated from the relative intensities of the CH₃OH and CO lines, increased with decreasing r_h, from about10 K at 7 AU to 110 K around perihelion. The expansion velocity of the gaseous species, derived from the line shapes, also increased with a law close tor_h ³. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Radio Line Observations Of Molecular And Isotopic Species In Comet C/1995 O1 (Hale-Bopp)     

Despois  D. 《Earth, Moon, and Planets》1997,79(1-3):103-124

We present here a review of the radio observations of the remarkable comet Hale-Bopp C/1995 O1 in which most major radio astronomical facilities have been involved. These observations started in August 1995, soon after the discovery of the comet (it was then at ∼7 AU from the sun), and well before its perihelion on April 1st, 1997; they are still going on, hopefully up to end of 1998. Extended cartographies have been obtained using multibeam receivers and on-the-fly techniques. High spatial resolution (a few ″) has been achieved with interferometers. Submillimetric observations are playing an increasing role, and high resolution (R ∼ 10⁶−10⁷) spectroscopy of cometary lines is now performed from decimetric to submillimetric wavelengths. The number of species observed at radio wavelengths now reaches ∼28,when it was ∼14 for comet C/1996 B2 Hyakutake. Most of these species are parent molecules. However, ions have been observed for the first time at radio wavelengths, and their velocities measured. Several isotopic species (involving D,¹³C,³⁴S,¹⁵N) have been sought, allowing isotopic enrichment determinations. The abundances of cometary molecules present many similarities and some differences with the abundances of interstellar molecules in regions where grain mantles are believed to be evaporated to the gas phase (hot cores, bipolar flows). They will be discussed for their implications on the origin of cometary ices and of comets themselves. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The 1995–2002 Long-Term Monitoring of Comet C/1995 O1 (HALE–BOPP) at Radio Wavelength     

Biver  Nicolas  Bockelée-Morvan  Dominique  Colom  Pierre  Crovisier  Jacques  Henry  Florence  Lellouch  Emmanuel  Winnberg  Anders  Johansson  Lars E.B.  Gunnarsson  Marcus  Rickman  Hans  Rantakyrö  Fredrik  Davies  John K.  Dent  William R.F.  Paubert  Gabriel  Moreno  Raphaël  Wink  Jörn  Despois  Didier  Benford  Dominic J.  Gardner  Matt  Lis  Dariusz C.  Mehringer  David  Phillips  Thomas G.  Rauer  Heike 《Earth, Moon, and Planets》2002,90(1-4):5-14

The bright comet Hale–Bopp provided the first opportunity to follow the outgassing rates of a number of molecular species over a large range of heliocentric distances. We present the results of our observing campaign at radio wavelengths which began in August 1995 and ended in January 2002. The observations were carried out with the telescopes of Nançay, IRAM, JCMT, CSO and, since September 1997, SEST. The lines of nine molecules (OH, CO, HCN, CH₃OH, H₂CO, H₂S, CS, CH₃CN and HNC) were monitored. CS, H₂S, H₂CO, CH₃CN were detected up to r_h= 3–4 AU from the Sun, while HCN and CH₃OH were detected up to 6 AU. CO, which is the main driver of cometary activity at heliocentric distances larger than 3–4 AU, was last detected in August 2001, at r_h= 14 AU. The gas production rates obtained from this programme contain important information on the nature of cometary ices, their thermal properties and sublimation mechanisms.Line shapes allow to measure gas expansion velocities, which, at large heliocentric distances, might be directly connected to the temperature of the nucleus surface. Inferred expansion velocity of the gas varied as r_h ^-0.4 within 7 AU from the Sun, but remained close to 0.4 km s^-1 further away. The CO spectra obtained at large r_hare strongly blueshifted and indicative of an important day-to-night asymmetry in outgassing and expansion velocity. The kinetic temperature of the coma, estimated from the relative intensities of the CH₃OH and CO lines, increased with decreasing r_h, from about 10 K at 7 AU to 110 K around perihelion.  相似文献   

Chemical Composition Diversity Among 24 Comets Observed At Radio Wavelengths     

Biver  Nicolas  Bockelée-Morvan  Dominique  Crovisier  Jacques  Colom  Pierre  Henry  Florence  Moreno  Raphaël  Paubert  Gabriel  Despois  Didier  Lis  Dariusz C. 《Earth, Moon, and Planets》2002,90(1-4):323-333

We present a comparative study on molecular abundances in comets basedon millimetre/submillimetre observations made with the IRAM 30-m,JCMT, CSO and SEST telescopes. This study concerns a sample of 24comets (6 Jupiter-family, 3 Halley-family, 15 long-period) observedfrom 1986 to 2001 and 8 molecular species (HCN, HNC, CH₃CN,CH₃OH, H₂CO, CO, CS, H₂S). HCN was detected in all comets,while at least 2 molecules were detected in 19 comets. From the sub-sample of comets for which contemporary H₂O productionrates are available, we infer that the HCN abundance relative to water variesfrom 0.08% to 0.25%. With respect to other species, HCN is the moleculewhich exhibits the lowest abundance variation from comet to comet. Therefore,production rates relative to that of HCN can be used for a comparative study ofmolecular abundances in the 19 comets. It is found that: CH₃OH/HCN varies from ≤ 9 to 64; CO/HCN varies from ≤ 24 to 180; H₂CO/HCN varies between 1.6 and 10; and H₂S/HCN varies between 1.5 and 7.6. This study does not show any clear correlation between the relative abundancesand the dynamical origins of the comets, or their dust-to-gas ratios.  相似文献   

Could we identify hot ocean-planets with CoRoT, Kepler and Doppler velocimetry?     

F. Selsis  P. Bordé  F. Brachet  F. Bouchy  J.-M. Grießmeier  C. Sotin  C. Moutou  M. Deleuil  D. Despois  A. Léger 《Icarus》2007,191(2):453-468

Planets less massive than about 10 MEarth are expected to have no massive H-He atmosphere and a cometary composition (∼50% rocks, 50% water, by mass) provided they formed beyond the snowline of protoplanetary disks. Due to inward migration, such planets could be found at any distance between their formation site and the star. If migration stops within the habitable zone, this may produce a new kind of planets, called ocean-planets. Ocean-planets typically consist in a silicate core, surrounded by a thick ice mantle, itself covered by a 100 km-deep ocean. The possible existence of ocean-planets raises important astrobiological questions: Can life originate on such body, in the absence of continent and ocean-silicate interfaces? What would be the nature of the atmosphere and the geochemical cycles? In this work, we address the fate of hot ocean-planets produced when migration ends at a closer distance. In this case the liquid/gas interface can disappear, and the hot H₂O envelope is made of a supercritical fluid. Although we do not expect these bodies to harbor life, their detection and identification as water-rich planets would give us insight as to the abundance of hot and, by extrapolation, cool ocean-planets. The water reservoir of these planets seems to be weakly affected by gravitational escape, provided that they are located beyond some minimum distance, e.g. 0.04 AU for a 5-Earth-mass planet around a Sun-like star. The swelling of their water atmospheres by the high stellar flux is expected not to significantly increase the planets' radii. We have studied the possibility of detecting and characterizing these hot ocean-planets by measuring their mean densities using transit missions in space—CoRoT (CNES) and Kepler (NASA)—in combination with Doppler velocimetry from the ground—HARPS (ESO) and possible future instruments. We have determined the domain in the [stellar magnitude, orbital distance] plane where discrimination between ocean-planets and rocky planets is possible with these instruments. The brightest stars of the mission target lists and the planets closest to their stars are the most favorable cases. Full advantage of high precision photometry by CoRoT, and particularly Kepler, can be obtained only if a new generation of Doppler instruments is built.  相似文献   

New Molecular Species in Comet C/1995 O1 (Hale-Bopp) Observed with the Caltech Ssubmillimeter Observatory     

Lis  D. C.  Mehringer  D. M.  Benford  D.  Gardner  M.  Phillips  T. G.  Bockelée-Morvan  D.  Biver  N.  Colom  P.  Crovisier  J.  Despois  D.  Rauer  H. 《Earth, Moon, and Planets》1997,78(1-3):13-20

We present millimeter-wave observations of HNCO, HC₃N, SO, NH₂CHO, H¹³CN, and H₃O⁺ in comet C/1995 O1 (Hale-Bopp)obtained in February–April, 1997 with the Caltech Submillimeter Observatory (CSO). HNCO, first detected at the CSO in comet C/1996B2 (Hyakutake), is securely confirmed in comet Hale-Bopp via observations of three rotational transitions. The derived abundance with respect to H₂O is (4-13) × 10^-4. HC₃N, SO, and NH₂CHO are detected for the first time in a comet. The fractional abundance of HC₃N based on observations of three rotational lines is (1.9 ± 0.2) × 10^-4. Four transitions of SO are detected and the derived fractional abundance, (2-8) ×10^-3, is higher than the upper limits derived from UV observations of previous comets. Observations of NH₂CHO imply a fractional abundance of (1-8) × 10^-4. H₃O is detected for the first time from the ground. The H¹³CN (3-2)transition is also detected and the derived HCN/H¹³CN abundance ratio is 90 ± 15, consistent with the terrestrial¹²C/¹³C ratio. In addition, a number of other molecular species are detected, including HNC, OCS, HCO⁺, CO⁺, and CN(the last two are first detections in a comet at radio wavelengths). This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Evidences for extended sources and temporal modulations in molecular observations of C/1995 O1 (Hale-Bopp) at the IRAM interferometer     

Wink  J.  Bockelée-Morvan  D.  Despois  D.  Colom  P.  Biver  N.  Crovisier  J.  Gérard  E.  Lellouch  E.  Davies  J. K.  Dent  W. R. F.  Jorda  L. 《Earth, Moon, and Planets》1997,78(1-3):63-63

Comet C/1995 O1 (Hale-Bopp) has been observed on October 5 and 25, 1996 and from March 6 to March 22, 1997 with the Institut de Radioastronomie Millimétrique (IRAM) interferometer at Plateau de Bure (France). Millimetre lines of HCN,HNC, CO, H₂CO, CH₃OH, H₂S, CS and SO were mapped with spatial resolutions of 1.5–3.5 arc sec. These observations allow us to investigate whether these species are released by the nucleus or produced in the coma by extended sources or photo-processes. The brightness distribution of the HCN J (1-0) line is consistent with release from the nucleus. The HNC J (1-0) distribution deviates from that of HCN in the innermost coma, and indicates production of HNC in the coma. This is in agreement with the heliocentric variation of the HNC/HCN ratio (Biver et al., 1997, Science 275, 1915; Irvine et al., 1998, this issue) and formation by chemical reactions (Rodgers and Charnley, 1998, Ap. J. 501, L227; Irvine et al., 1998, Nature 393, 547). There is clear evidence that SO is a photo dissociation product. The observations also confirm that H₂CO is mainly produced by an extended source, as first evidenced in comet P/Halley. The contribution of the nucleus to the total H₂CO production rate does not exceed 6%. The molecular lines have also been monitored hourly with the five antennas of the interferometer in single-dish mode. The line velocity shifts show aperiodic modulation linked to the nucleus rotation. The amplitude of the modulation differs from one species to another. The periodic modulation seen for the CO J (2-1) line on March 11 suggests that a significant fraction of CO is released continuously night and day by an active source situated at equatorial latitudes on the nucleus surface. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Radioastronomical observations of comets IRAS-Araki-Alcock (1983d) and Sugano-Saigusa-Fujikawa (1983e)     

W.M. Irvine  Z. Abraham  M. A&#x;Hearn  W. Altenhoff  Ch. Andersson  J. Bally  W. Batrla  A. Baudry  D. Bockelée-Morvan  G. Chin  J. Crovisier  I. de Pater  D. Despois  L. Ekelund  E. Gerard  T. Hasegawa  C. Heiles  J.M. Hollis  A. Wootten 《Icarus》1984,60(1):215-220

Detections and upper limits to the continuum emission (1 ≤ λ ≤6 cm) and spectral line emission (OH, CO, CS, HCN, HCO⁺, CN, CH₃CN, CH₃C₂H, NH₃, H₂O, HC₃N, CH₃CH₂CN) are reported from radio observations of Comets 1983d and 1983e. Comparison is made with observations of CN at optical wavelengths. These results may be useful in planning future cometary observations.  相似文献