Latest News on Comet Hale-Bopp

97/03/29. Detection of water.

N. Dello Russo (Goddard Space Flight Center, NASA) and collaborators detected water on January 21.5, February 23.9-24.1 and March 1.7-1.9 using the NASA Infrared Telescope Facility (IAUC 6604). The water production rates were 2.7, 4.3 and 4.0×10³⁰ molecules/s on each date.

97/03/27. Hubble and IUE observations yield surprising data.

The findings can be summarised in these key results: 1) The surface of Hale-Bopp's nucleus must be an incredibly dynamic place, with 'vents' being turned on and off as new patches of icy material are rotated into sunlight for the first time; 2) Water ice sublimates at a different rate than the trace ices, implying that those components are not contained within the water on the comet. This result is contrary to previous models for a comet's nucleus which suggest that the trace components, such as carbon disulfide ice, are contained inside of the most abundant ice on the comet; 3) By studying Hubble Space Telescope images, the astronomers have estimated that its nucleus may be about 30 to 40 kilometers in diameter. The average comet is thought to have a nucleus of about 5 kilometers or even smaller. A Press- Photo can be found here [jpg,339k].

97/03/26. First detection of H₂CS in Hale-Bopp.

Laura Woodney (University of Maryland) and collaborators report the detection of H₂CS for the first time in comet Hale-Bopp using the NRAO 12-meter on March 23. They derive a production rate of 5.4×10²⁶.

97/03/24. Summary of molecules detected so far.

Richard West (ESO) reports the following list of molecules detected on Hale-Bopp written by Dominique Bockelee-Morvan (Observatoire de Paris): H₂O, HDO, OH, H₂O+, CO, CO₂, CO+, HCO+, H₂S, SO, SO₂, OCS, CS, CH₃OH, H₂CO, HCOOH, HCN, CH₃CN, HNC, HC₃N, HNCO, CN, NH₂, NH, CH₄, C₂H₂, C₂H₆, C₃, C₂, Na, and the isotopes: H¹³CN, HC¹⁵N, C³⁴S.

97/03/23. Detection of methyl cyanide.

A.J. Apponi (Steward Observatory) and collaborators detected methyl cyanide using the NRAO 12 m telescope on March 20 (IAUC 6599). The transition observed of the CH₃CN was located near 147.1 GHz. Although they searched for vinyl cyanide (H₂CCHCN) and ethyl cianide (H₃ CCH₂CN) no emission was detected. This is not the first detection of methyl cyanide because it was first observed in 1996 (IAUC 6458) as Dominique Bockelee-Morvan (Observatoire de Paris) informs.

97/03/23. Formic acid on Hale-Bopp.

J.E. Wink (IRAM) and collaborators observed formic acid (HCOOH) at the IRAM Plateau de Bure interferometer on March 20.6 UT (IAUC 6599). The derived production rate is about 5×10²⁷ molecules/s.

97/03/23. Straight dust striae.

K. Birkle (Max Planck Institute for Astronomy) and collaborators observed a pattern of at least 12 straight dust striae with the Calar Alto Schmidt telescope on March 17 (IAUC 6598). The striae are 1 to 3 arcminutes wide and at a nuclear distance of 1.5 to 3 degrees in the dust tail. The pattern doesn't follow the synchronic direction so they must be due to secondary processes in the outer coma.

97/03/20. First detection of SO₂ in a comet.

J.E. Wink (IRAM) and collaborators found SO₂ in Hale-Bopp at the IRAM Plateau de Bure interferometer on March 18 (IAUC 6591). The calculated production rate is 6×10²⁷.

97/03/20. Observations of HCO+ and CO.

G. Narayanan (Steward Observatory) and collaborators observed HCO+ and CO lines using the 10 m Heinrich Hertz Telescope on March 5 and 9 (IAUC 6591). They found a slight asymmetry with a red wing in the line HCO+(3-2) at 267.6 GHZ. The HCO+ (4-3) line was observed on Mar 9 with identical result, a redward wing that is offset by 3.6 km/s relative to the main line. They calculated the following column densities and production rates: CO, 6.1×10¹⁴ cm^-2 and 1.7×10²⁹ molecules/s; HCO+, 2.7×10¹² cm^-2 and 7.0×10²⁶ molecules/s.

97/03/18. Maps of HCN, CS and HCO+.

A. Lovell and collaborators (University of Massachusetts) mapped the lines HCN J=1-0, CS J=2-1 and HCO+ J=1-0 using the FCRAO 14 m antenna on March 11-13 (IAUC 6590). HCN and CS emissions peak at the nucleus, but the HCO+ is highly asymmetric. They report that HCN and CS lines have widths of 2.0 km/s and are centered on the velocity of the nucleus. However, the HCO+ line is broader at the nucleus position (width 3.2 km/s) and it is redshifted by 1.0 km/s.

97/03/17. Abundance ratio [HNC]/[HCN].

A.J. Apponi and collaborators from the University of Arizona have detected HNC J=3-2 transition at 271.981 GHz on March 10 and HCO+ J=2-1 and J=3-2 at 178.375 and 267.557 GHz respectively, and CHN J=2-1 at 177.261 GHz on March 9 using the NRAO 12 m telescope at Kitt Peak. They suggest an abundance ratio for [HNC]/[HCN] about 0.5 (IAUC 6586).

97/03/17. Jacobus Kapteyn Telescope confirms spiral-jet and arc structures.

Richard West (ESO) informs that observations obtained by the European Comet Hale-Bopp Team with the 1m Jacobus Kapteyn Telescope (IAU Circular 6587, March 14), taken by J. Licandro (IAC) and P. Rudd (ING), broadly confirm the observations of Birkle and Boehnhardt (see below, 97/03/12) reported on IAUC 6583. The images, taken through a CN and a blue continuum filter with Laplacian filtering applied to the reduced images, reveal both spiral-jet and arc structures. Pictures are available at a small version of 49k or a larger version of 184k. Assuming, as on IAUC 6583, that the two arcs are ejected by the same active spot and that the nucleus rotates with an 11.47 hour period (Lecacheaux et al., IAUC 6560, Jorda et al., IAUC 6583) they obtain an expansion velocity for CN of 1.3km/s for a 60 degree rotation between arc emission, very close to the velocity calculated by Birkle and Boehnhardt.

97/03/16. Production rates at r=1.02-1.01 AU.

T. Farnham, D. Schleicher (Lowell Observatory) and S. Lederer (University of Florida) using the 31" telescope at Lowell Observatory measured log Q(OH)=30.24, log Q(CN)=28.05 and log Q(C₂)=28.16 on March 6.5 and 7.5. The dust production rate was log A=5.93. Gas production is leveling off and dust production is increasing at a slower rate compared to the 7 previous weeks (IAUC 6589).

97/03/13. NASA plans comet Hale-Bopp Observing Campaign.

NASA and agency-supported scientists will study Hale-Bopp using sounding rockets, spacecraft and ground-based observations. The Wallops Flight Facility (WFF) will conduct four sounding rocket launches starting March 24 through April 5. The joint NASA/ESA Ulysses spacecraft will study what happens to comets as they are exposed to different solar wind conditions at various solar latitudes. Hubble Space Telescope cannot observe Hale-Bopp during the next few months because the comet is too close to the Sun. The last observation was made on October 18, 1996 and the next possible opportunity will be this autumn. And finally NASA's Polar spacecraft will make observations of Hale-Bopp using ultraviolet and visible imaging instruments.

97/03/12. New results about the spin period.

L. Jorda (Max Planck Institut), J. Lecacheux (Observatoire de Paris) and F. Colas (Bureau des Longitudes) confirm the spin period of 11.47 +/- 0.05 hr but with a periodic oscillation between 11.20 +/- 0.10 hr and 11.65 +/- 0.10 hr and a superperiod of 22 +/- 2 days. A sequence of images covering a whole rotation period is available at http://www.bdl.fr/s2p/comete/halebopp/hbrot.html.

97/03/12. Determination of the gas-expansion velocity.

K. Birkle (Max Planck Institut fur Astronomie) and H. Bohnhardt (Universitats Sternwarte) determined a CN gas-expansion velocity of about 1.3 km/s using observations obtained with the Calar Alto 1.2 m telescope.

97/03/11. Synchronic Bands in Dust Tail of Comet Hale-Bopp.

H. Fukushima (National Astronomical Observatory of Japan), M. Takata (Univ. Electro-Communications) and D. Kinoshita (Tohoku University) recognized several filaments in dust tail on March 6. They inform that the characteristics of these filaments are similar to that of the synchronic bands, which appeared in dust tail of several great comets such as West 1976VI, Seki-Lines 1962III, Ikeya-Seki 1965VIII and Mrkos 1957V, although the synchronic bands in these comets were observed when the heliocentric distance was smaller than 0.5 AU. Their images are released at their web site.

97/03/05. First detection of HCO+ in a comet.

J. M. Veal and L. E. Snyder (University of Illinois), M. C. H. Wright, J. R. Forster, W. Hoffman, M. Pound, I. de Pater, T. Helfer, R. L. Plambeck, G. Engargiola and T. Wong (University of California), L. M. Woodney and M. F. A'Harn (University of Maryland), P. Palmer (University of Chicago) and Y.-J. Kuan (Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan) detected HCO+ using seven antennae of the Berkeley-Illinois-Maryland-Association Array on February 19, 22 and 28.

97/03/04. Very strong emission from organic grains.

M. J. Mumma, M. A. DiSanti and N. Dello Russo (Goddard Space Flight Center, NASA), K. Magee-Sauer (Rowan College of New Jersey), R. Novak (Iona College) and M. Fomenkova (University of California) observed the dust continnuum spectrum using the NASA Infrared Telescope Facility on February 24 and suggest very strong emission from organic grains.

97/03/04. First secure detection of SO in a comet.

D. C. Lis, M. Gardner and T. G. Phillips (Caltech Submillimeter Observatory), D. Bockelee-Morvan, N. Biver, Crovisier, H. Rauer, P. Colom and D. Gautier (Observatoire de Paris) and D. Despois (Observatoire de Bordeaux) detected by radio SO, OCS, CO+ and CN at the Caltech Submillimeter Observatory on February 20-23. This is the first secure detection of SO in a comet.

97/02/27. Na D emission detected.

T. Kawabata, K. Ayani, K. Kinoshita and M. Fujii (Bisei Astrronomical Observatory, Japan) detected Na I D1 and D2 emission lines using the 1-m telescope at Bisei Astronomical Observatory on February 27.

97/02/26. Production rates of CO and H₂O.

M. J. Mumma, M. A. DiSanti and N. Dello Russo (Goddard Space Flight Center), K. Magee-Sauer (Rowan College of New Jersey) and M. Fomenkova (University of California) using the NASA Infrared Telescope Facility derived Q(CO)=3.2e29 mol/s and Q(H₂O)=5e30 mol/s on January 21.

97/02/25. First detection of 14N/15N in a comet

H. Matthews (Joint Astronomy Centre), Herzberg (Institute of Astrophysics) and D. Jewitt (University of Hawaii) measured the following isotopes ratios with the James Clerk Maxwell Telescope on February 16: H₁₂CN/H₁₃CN=90+/-10 and HC₁₄N/HC₁₅N=299+/-30. Within the uncertainties, these isotope ratios are compatible with the terrestrial values.

97/02/25. Continuum flux density measurement

H. Matthews (Joint Astronomy Centre), Herzberg (Institute of Astrophysics) and DD. Jewitt (University of Hawaii) measured the continuum flux density using the James Clerk Maxwell Telescope, obtaining 329 +/- 96 and 464 +/- 62 mJy on February 9 and 16 respectively. The effective cross-section is 40 times larger than in comet 1P/Halley at similar heliocentric distances.

97/02/25. Detection of HNCO and HCCCN.

D. C. Lis, M. Gardner and T. G. Phillips (Caltech Submillimeter Observatory), D. Bockelee-Morvan, N. Biver, J. Crovisier and P. Colom (Observatoire de Paris) and D. Despois (Observatoire de Bordeaux) detected several transitions of HNCO and HCCCN in the range 218-352 GHz observing with Caltech Submillimeter Observatory. The estimated production rates are 2.3 and 0.8e27 mol/s respectively. They have also detected HNC, HCN and H₁₃CN. The first identifications of HNCO and H₁₃CN in a comet were detected in C/1996 B2.

97/02/25. Detection of OCS J(12-11). Production rates of H₂S and CS.

Laura Woodney, Mike A'Hearn (University of Maryland), Joe McMullin (NRAO) and Nalin Samarasinha (NOAO) have detected OCS J(12-11) transition at 145.95 Ghz in C/Hale-Bopp using the NRAO 12-meter dish on Kitt Peak. They observed this line on both January 29th and February 21st. They derive production rates of Q(OCS)=4.2e27-6.2e27 mol/sec. They also observed H₂S and CS on February 21st. The derived production rates are 1.8e28 and 8.0e27 mol/sec respectively.

97/02/19. Infered rotation period of 11.47 +/- 0.05 hours.

J. Lecacheux (Observatoire de Paris-Meudon), L. Jorda, (Max-Planck-Institut fur Aeronomie) and F. Colas (Bureau des Longitudes) infer a possible rotation period of 11.47 +/- 0.05 hours from the comparison of images obtained during different nights between the 12th of January and the 10th of February. They also confirm the dust shells first observed by O. Lardiere at Haut Provence Observatory.