next up previous
Next: About this document ...

Water in Comets: A Target of Opportunity Proposal to Observe
Cometary OH

A. Wootten,(NRAO)
and Green Bank and Charlottesville REU Students

Water is the primary parent constituent of cometary atmospheres within 3 AU of the sun, but is normally unobservable or difficult to observe using earthbound telescopes. In the inner solar system, water escaping from the nucleus photodissociates, resulting in the production of the observable daughter molecule OH.

We propose to measure the water production rate in a bright newly discovered comet. This comet, C/1999 H1 (Lee), is a rich and productive comet, which will be entering southern skies accessible from Green Bank during late May. During that time, it will be optically visible at about magnitude 7.5. Using a formula due to Festou, we predict from this a water production rate of about 10 29 mol s-1, one-third of P/Halley. From this we estimate that the OH lines would have an intrinsic strength of 0.3 K for the 1667 line, including a rough estimate of the Swings effect, which can extinguish the OH emission at certain relative velocities.

In addition to providing supporting data for other observatories, these observations will provide the summer students with a chance to gain observing and data reduction experience, produce a publishable result, as well as provide an introduction to some cometary science.

Photo of Comet Lee

Recent Comet News

some appearance predictions.

Scheduling Parameters
1em #& #& #& #& #

Comet & LST Range & Transit & $\Delta$Ta & Datesb Name & & (LST) & (hours) &

C/1999 H1 (Lee) & 4h - 10h & 8h 48m & 4 & 22-25 May

a Approximate time needed for observation b Dates 1.6 GHz receiver is available

JPL DASTCOM Database Browser

JPL DASTCOM Database Browser

Comet C/Lee (1999 H1)
Alternate Designation: none

Record Number201642
Epoch of Osculation (Julian Day, ET)2451360.5
Epoch of Osculation (Calendar Date, ET)1999-07-01
Astronomical Reference SystemFK5/J2000
Orbit Solution ReferenceJPL#17

(heliocentric ecliptic reference frame)

Mean Anomaly (deg)359.9992879
Argument of Perihelion (deg)40.8031036
Longitude of the Ascending Node (deg)162.6724549
Inclination (deg)149.3503289
Semi-major Axis (AU)584.0668979
Perihelion Passage (Julian Day, ET)2451370.6985308
Perihelion Passage (Calendar Date, ET)1999-07-11.1985308
Perihelion Distance (AU)0.707314274


GM (km^3 s^-2)n/a
Radius (km)n/a
A1 (e-8 AU/d^2)n/a
A2 (e-8 AU/d^2)n/a
M1 (total absolute magnitude) 7.0
M2 (nuclear absolute magnitude)n/a
Year Designation1999
Orbit Solution Data Arc 32 days
Observations used in Orbit Solution 185
Comments A
Comments B k1=10; ref. for magnitude law is M.P.C. 34634

JPL/SSD Home Credits/Awards

Contact: Webmaster (

Last modified: 1999 March 3 15:39

next up previous
Next: About this document ...
Al Wootten