Alert Notice 755: Exoplanet transit observation requested for HD 80606

September 22, 2021

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Dr. Dennis Conti, AAVSO Exoplanet Section Leader, provides the following:

“Rob Zellem (JPL/NASA’s Exoplanet Watch program) has requested help in observing a transiting exoplanet in order to help a researcher appropriately schedule JWST time. Because of the uncertain mid-transit time, such follow-up observations will help narrow JWST’s observing window.

“The target star is HD 80606, a 9.0 mag (V) star located at RA 09:22:37.57, DEC +50:36:13.4 (J2000.0). The expected transit depth is 11.0ppt, which should make it observable from most modest-size amateur telescopes. The exoplanet has a long transit duration (close to 12 hours), so most likely only an ingress or egress capture will be possible. An out-of-transit baseline of at least 30-60 minutes before ingress or after egress is requested. Also, since the exoplanet has a long period (111.4 days), the next observation opportunity is on or around December 7, 2021, from anywhere in the Northern Hemisphere.

“To determine the specific transit times for your particular location over the next 12 months, you can use the Swarthmore Transit Finder at, with the following suggested entries:

1. Target list: NASA Exoplanet Archive Database
2.  Choose “manual coordinate entry” and enter your location’s coordinates.
3.  Select a Base date of “today” and a “From” date of 365.
4.  Keep all other default values, but under Name, enter the string HD 80606 b.

"Observers should use the AAVSO Variable Star Plotter (VSP) to create a finder chart and to obtain potential comparison stars. Note, there is a 9.1 V mag star to the East of the target and should not be mistaken for the target.

“If you plan on conducting the observation or if you have any questions, please contact the AAVSO Exoplanet Section Lead, Dennis Conti, at Also, observations are to be submitted to Dennis for his review before being passed along. For further information on the Exoplanet Watch program, visit: Thank you for your help on this!”

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen using material supplied by Dr. Dennis Conti.


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