C/1999 H1 (Lee)

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C/1999 H1 (Lee)
Cometa Lee 1999 H1 con anticoda frontale.jpg
A mosaic of C/1999 H1 (Lee) taken on 9 December 1999
Discovery [1]
Discovered by Steven Lee
Discovery site Mudgee, Australia
Discovery date16 April 1999
Orbital characteristics [2]
Epoch 17 August 1999 (JD 2451407.5)
Observation arc 267 days
Number of
observations		1,019
Aphelion ~5,500 AU
Perihelion 0.708 AU
Semi-major axis ~2,800 AU
Eccentricity 0.99974
Orbital period ~146,000 years
Inclination 149.25°
162.65°
Argument of
periapsis 		40.702°
Mean anomaly 0.0002°
Last perihelion11 July 1999
TJupiter –0.896
Earth MOID 0.151 AU
Jupiter MOID 0.257 AU
Comet total
magnitude (M1)		9.4
Comet nuclear
magnitude (M2)		13.1

C/1999 H1 (Lee) is a non-periodic comet observed between April 1999 and January 2000. It is the only comet discovered by Australian astronomer, Steven Lee. Lee found the comet visually during a star party near Mudgee, New South Wales on 16 April 1999. [3] He estimated the comet had an apparent magnitude of 9. [1]

Contents

Physical characteristics

In February 1999, Comet Lee became the first moderately active comet where its properties were observed and measured by the Hubble Space Telescope in ultraviolet light. [4] Data obtained through the Telescope's STIS revealed the presence of S2 within its coma, making it the third comet known where such chemical compound was detected after C/1983 H1 (IRAS–Araki–Alcock) and C/1996 B2 (Hyakutake). [4] Observations of the coma from the La Palma Observatory in June 1999 indicated that the comet was dust-poor, with a relatively high gas-to-dust mass ratio of around 6.5–11.7 and a dust production rate of around Afρ = 500 cm. [5]

Spectrophotometric observations conducted at the European Southern Observatory between May and October 1999 detected the presence of OH, CH3OH, HCN, H2CO, and CS within its coma. [6] Water production rate while it was at least 1.3–1.7 AU (190–250 million km) from the Sun was estimated to be about 3.2×1028 sec−1 based on observations conducted by the Submillimeter Wave Astronomy Satellite (SWAS) during its outbound trajectory between September and December 1999. [7]

Additional data obtained from the Keck Observatory in August 1999 revealed that the comet is strongly depleted in carbon monoxide gas compared to other comets like C/1995 O1 (Hale–Bopp) and C/1996 B2 (Hyakutake), which may demonstrate the chemical diversity that occurred during the formation of the outer Solar System. [8]

References

  1. 1 2 S. Lee; G. J. Garradd (16 April 1999). D. W. Green (ed.). "Comet 1999 H1". IAU Circular. 7144 (1). Bibcode:1999IAUC.7144....1L.
  2. ↑ "C/1999 H1 (Lee) – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory . Retrieved 8 November 2025.
  3. ↑ S. Lee (1999). "The Discovery of Comet Lee" (PDF). www.cometchaser.de. Retrieved 8 November 2025.
  4. 1 2 P. D. Feldman; H. A. Weaver; M. F. A'Hearn; et al. (1999). "Ultraviolet imaging spectroscopy of comet Lee (C/1999 H1) with HST/STIS". Bulletin of the Astronomical Society. 31 (4): 1127. Bibcode:1999BAAS...31.1127F.
  5. ↑ L. M. Lara; R. Rodrigo; G. P. Tozzi; H. Boehnhardt; P. Leisy (2004). "The gas and dust coma of Comet C/1999 H1 (Lee)" (PDF). Astronomy & Astrophysics. 420 (1): 371–382. Bibcode:2004A&A...420..371L. doi: 10.1051/0004-6361:20034214 .
  6. ↑ N. Biver; D. Bockelée-Morvan; J. Crovisier; et al. (2000). "Spectroscopic Observations of Comet C/1999 H1 (Lee) with the SEST, JCMT, CSO, IRAM, and NanÇay Radio Telescopes". The Astronomical Journal. 120 (3): 1554–1570. Bibcode:2000AJ....120.1554B. doi: 10.1086/301529 .
  7. ↑ K. Chiu; D. A. Neufeld; E. A. Bergwin; et al. (2001). "Post-perihelion SWAS Observations of Water Vapor in the Coma of Comet C/1999 H1 (Lee)". Icarus. 154 (2): 345–349. Bibcode:2001Icar..154..345C. doi:10.1006/icar.2001.6706.
  8. ↑ M. J. Mumma; I. S. McLean; M. A. DiSanti; et al. (2001). "A Survey of Organic Volatile Species in Comet C/1999 H1 (Lee) Using NIRSPEC at the Keck Observatory". The Astrophysical Journal. 546 (2): 1183–1193. Bibcode:2001ApJ...546.1183M. doi: 10.1086/318314 .
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