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.
a Approximate time needed for observation b Dates 1.6 GHz receiver is available
|Epoch of Osculation (Julian Day, ET)||2451360.5|
|Epoch of Osculation (Calendar Date, ET)||1999-07-01|
|Astronomical Reference System||FK5/J2000|
|Orbit Solution Reference||JPL#17|
|Mean Anomaly (deg)||359.9992879|
|Argument of Perihelion (deg)||40.8031036|
|Longitude of the Ascending Node (deg)||162.6724549|
|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|
|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|
|Orbit Solution Data Arc||32 days|
|Observations used in Orbit Solution||185|
|Comments B||k1=10; ref. for magnitude law is M.P.C. 34634|
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