transitsearch.org

Period (days)	M.A. (deg)	e	omega (deg)	M sin(i) (Mjup)	epoch
3.524739	90.00	0.00	0.0	0.66	2451508.368
Fit: (Castellano et al. 2000 ApJL, 532, L51)

In 1999, the University of California Planet Search Team (see www.exoplanets.org) used the radial velocity technique to discover a Jovian-mass planet circling the star HD209458 on a 3.52 day orbit. Soon afterward, professional observers (see for example Dr. Tim Brown's STARE website) discovered that the planet's orbital plane is aligned with the line of sight to the Earth so that the planet occults the disk of the star once per orbit, causing transits that last for about 3 hours.

During the transits, the planet blocks about 1.5% of HD209458's light, leading to a measurable dimming of HD209458 in comparison to nearby stars, whose brightness remains nearly fixed over time intervals of several hours.

Here is a GIF image of HD209458 centered in a 0.3 by 0.3 degree field.

In January 2001, several Finnish Amateur Astronomers, led by Arto Oksanen, used their own equipment to observe the transit of HD209458. We were inspired to launch the transitsearch.org project when we learned of their observation. In order to better understand the difficulties facing Amateur astronomers who wish to observe transits, we built our own observatory, based on an 8 inch telescope, and observed one of the HD209458b transits for ourselves.

Click here for a detailed account of the procedures we used to capture the transit of HD209458b shown below.

A number of other amateur astronomers have successfully observed the HD209458b transit. We have links to a number of them here.

Following are predicted central transit times for HD 209458b. The times of ingress and egress are 1.6 hours before and 1.6 hours after these central times. These central transit times are in heliocentric Julian days, computed using the following orbital data:

Uncertainties vary from 1.92 minutes for the first listed transits to 2.36 minutes for the last listed transit on 5/9/2005. Note also that the observed central transits will deviate by up to +/- 5 minutes during the course of the year as a result of the varying light travel time from HD 209458 to the Sun as compared to the light travel time from HD 209458 to the Earth.

T0= HJD 2452223.896173 +/- 0.000086
P=3.5247542 +/- 0.0000044 d

from Schultz et al, 2003 (Preprint)
http://www-lep.gsfc.nasa.gov/code693/esp_papers/web/pdf/schultz_479.pdf

HD209458 Central Transit Times (Click here for a text file version)
Julian Date	Year	Month	Day	Hour	Min
`2452731.4608`	`2003`	`04`	`01`	`23`	`03`
`2452734.9855`	`2003`	`04`	`05`	`11`	`39`
`2452738.5103`	`2003`	`04`	`09`	`00`	`14`
`2452742.0350`	`2003`	`04`	`12`	`12`	`50`
`2452745.5598`	`2003`	`04`	`16`	`01`	`26`
`2452749.0845`	`2003`	`04`	`19`	`14`	`01`
`2452752.6093`	`2003`	`04`	`23`	`02`	`37`
`2452756.1341`	`2003`	`04`	`26`	`15`	`13`
`2452759.6588`	`2003`	`04`	`30`	`03`	`48`
`2452763.1836`	`2003`	`05`	`03`	`16`	`24`
`2452766.7083`	`2003`	`05`	`07`	`04`	`59`
`2452770.2331`	`2003`	`05`	`10`	`17`	`35`
`2452773.7578`	`2003`	`05`	`14`	`06`	`11`
`2452777.2826`	`2003`	`05`	`17`	`18`	`46`
`2452780.8073`	`2003`	`05`	`21`	`07`	`22`
`2452784.3321`	`2003`	`05`	`24`	`19`	`58`
`2452787.8568`	`2003`	`05`	`28`	`08`	`33`
`2452791.3816`	`2003`	`05`	`31`	`21`	`09`
`2452794.9064`	`2003`	`06`	`04`	`09`	`45`
`2452798.4311`	`2003`	`06`	`07`	`22`	`20`
`2452801.9559`	`2003`	`06`	`11`	`10`	`56`
`2452805.4806`	`2003`	`06`	`14`	`23`	`32`
`2452809.0054`	`2003`	`06`	`18`	`12`	`07`
`2452812.5301`	`2003`	`06`	`22`	`00`	`43`
`2452816.0549`	`2003`	`06`	`25`	`13`	`19`
`2452819.5796`	`2003`	`06`	`29`	`01`	`54`
`2452823.1044`	`2003`	`07`	`02`	`14`	`30`
`2452826.6291`	`2003`	`07`	`06`	`03`	`05`
`2452830.1539`	`2003`	`07`	`09`	`15`	`41`
`2452833.6786`	`2003`	`07`	`13`	`04`	`17`
`2452837.2034`	`2003`	`07`	`16`	`16`	`52`
`2452840.7282`	`2003`	`07`	`20`	`05`	`28`
`2452844.2529`	`2003`	`07`	`23`	`18`	`04`
`2452847.7777`	`2003`	`07`	`27`	`06`	`39`
`2452851.3024`	`2003`	`07`	`30`	`19`	`15`
`2452854.8272`	`2003`	`08`	`03`	`07`	`51`
`2452858.3519`	`2003`	`08`	`06`	`20`	`26`
`2452861.8767`	`2003`	`08`	`10`	`09`	`02`
`2452865.4014`	`2003`	`08`	`13`	`21`	`38`
`2452868.9262`	`2003`	`08`	`17`	`10`	`13`
`2452872.4509`	`2003`	`08`	`20`	`22`	`49`
`2452875.9757`	`2003`	`08`	`24`	`11`	`25`
`2452879.5005`	`2003`	`08`	`28`	`00`	`00`
`2452883.0252`	`2003`	`08`	`31`	`12`	`36`
`2452886.5500`	`2003`	`09`	`04`	`01`	`11`
`2452890.0747`	`2003`	`09`	`07`	`13`	`47`
`2452893.5995`	`2003`	`09`	`11`	`02`	`23`
`2452897.1242`	`2003`	`09`	`14`	`14`	`58`
`2452900.6490`	`2003`	`09`	`18`	`03`	`34`
`2452904.1737`	`2003`	`09`	`21`	`16`	`10`
`2452907.6985`	`2003`	`09`	`25`	`04`	`45`
`2452911.2232`	`2003`	`09`	`28`	`17`	`21`
`2452914.7480`	`2003`	`10`	`02`	`05`	`57`
`2452918.2727`	`2003`	`10`	`05`	`18`	`32`
`2452921.7975`	`2003`	`10`	`09`	`07`	`08`
`2452925.3223`	`2003`	`10`	`12`	`19`	`44`
`2452928.8470`	`2003`	`10`	`16`	`08`	`19`
`2452932.3718`	`2003`	`10`	`19`	`20`	`55`
`2452935.8965`	`2003`	`10`	`23`	`09`	`30`
`2452939.4213`	`2003`	`10`	`26`	`22`	`06`
`2452942.9460`	`2003`	`10`	`30`	`10`	`42`
`2452946.4708`	`2003`	`11`	`02`	`23`	`17`
`2452949.9955`	`2003`	`11`	`06`	`11`	`53`
`2452953.5203`	`2003`	`11`	`10`	`00`	`29`
`2452957.0450`	`2003`	`11`	`13`	`13`	`04`
`2452960.5698`	`2003`	`11`	`17`	`01`	`40`
`2452964.0946`	`2003`	`11`	`20`	`14`	`16`
`2452967.6193`	`2003`	`11`	`24`	`02`	`51`
`2452971.1441`	`2003`	`11`	`27`	`15`	`27`
`2452974.6688`	`2003`	`12`	`01`	`04`	`03`
`2452978.1936`	`2003`	`12`	`04`	`16`	`38`
`2452981.7183`	`2003`	`12`	`08`	`05`	`14`
`2452985.2431`	`2003`	`12`	`11`	`17`	`50`
`2452988.7678`	`2003`	`12`	`15`	`06`	`25`
`2452992.2926`	`2003`	`12`	`18`	`19`	`01`
`2452995.8173`	`2003`	`12`	`22`	`07`	`36`
`2452999.3421`	`2003`	`12`	`25`	`20`	`12`
`2453002.8668`	`2003`	`12`	`29`	`08`	`48`
`2453006.3916`	`2004`	`01`	`01`	`21`	`23`
`2453009.9164`	`2004`	`01`	`05`	`09`	`59`
`2453013.4411`	`2004`	`01`	`08`	`22`	`35`
`2453016.9659`	`2004`	`01`	`12`	`11`	`10`
`2453020.4906`	`2004`	`01`	`15`	`23`	`46`
`2453024.0154`	`2004`	`01`	`19`	`12`	`22`
`2453027.5401`	`2004`	`01`	`23`	`00`	`57`
`2453031.0649`	`2004`	`01`	`26`	`13`	`33`
`2453034.5896`	`2004`	`01`	`30`	`02`	`09`
`2453038.1144`	`2004`	`02`	`02`	`14`	`44`
`2453041.6391`	`2004`	`02`	`06`	`03`	`20`
`2453045.1639`	`2004`	`02`	`09`	`15`	`56`
`2453048.6887`	`2004`	`02`	`13`	`04`	`31`
`2453052.2134`	`2004`	`02`	`16`	`17`	`07`
`2453055.7382`	`2004`	`02`	`20`	`05`	`42`
`2453059.2629`	`2004`	`02`	`23`	`18`	`18`
`2453062.7877`	`2004`	`02`	`27`	`06`	`54`
`2453066.3124`	`2004`	`03`	`01`	`19`	`29`
`2453069.8372`	`2004`	`03`	`05`	`08`	`05`
`2453073.3619`	`2004`	`03`	`08`	`20`	`41`
`2453076.8867`	`2004`	`03`	`12`	`09`	`16`
`2453080.4114`	`2004`	`03`	`15`	`21`	`52`
`2453083.9362`	`2004`	`03`	`19`	`10`	`28`
`2453087.4609`	`2004`	`03`	`22`	`23`	`03`
`2453090.9857`	`2004`	`03`	`26`	`11`	`39`
`2453094.5105`	`2004`	`03`	`30`	`00`	`15`
`2453098.0352`	`2004`	`04`	`02`	`12`	`50`
`2453101.5600`	`2004`	`04`	`06`	`01`	`26`
`2453105.0847`	`2004`	`04`	`09`	`14`	`01`
`2453108.6095`	`2004`	`04`	`13`	`02`	`37`
`2453112.1342`	`2004`	`04`	`16`	`15`	`13`
`2453115.6590`	`2004`	`04`	`20`	`03`	`48`
`2453119.1837`	`2004`	`04`	`23`	`16`	`24`
`2453122.7085`	`2004`	`04`	`27`	`05`	`0`
`2453126.2332`	`2004`	`04`	`30`	`17`	`35`
`2453129.7580`	`2004`	`05`	`04`	`06`	`11`
`2453133.2828`	`2004`	`05`	`07`	`18`	`47`
`2453136.8075`	`2004`	`05`	`11`	`07`	`22`
`2453140.3323`	`2004`	`05`	`14`	`19`	`58`
`2453143.8570`	`2004`	`05`	`18`	`08`	`34`
`2453147.3818`	`2004`	`05`	`21`	`21`	`09`
`2453150.9065`	`2004`	`05`	`25`	`09`	`45`
`2453154.4313`	`2004`	`05`	`28`	`22`	`21`
`2453157.9560`	`2004`	`06`	`01`	`10`	`56`
`2453161.4808`	`2004`	`06`	`04`	`23`	`32`
`2453165.0055`	`2004`	`06`	`08`	`12`	`07`
`2453168.5303`	`2004`	`06`	`12`	`00`	`43`
`2453172.0550`	`2004`	`06`	`15`	`13`	`19`
`2453175.5798`	`2004`	`06`	`19`	`01`	`54`
`2453179.1046`	`2004`	`06`	`22`	`14`	`30`
`2453182.6293`	`2004`	`06`	`26`	`03`	`06`
`2453186.1541`	`2004`	`06`	`29`	`15`	`41`
`2453189.6788`	`2004`	`07`	`03`	`04`	`17`
`2453193.2036`	`2004`	`07`	`06`	`16`	`53`
`2453196.7283`	`2004`	`07`	`10`	`05`	`28`
`2453200.2531`	`2004`	`07`	`13`	`18`	`04`
`2453203.7778`	`2004`	`07`	`17`	`06`	`40`
`2453207.3026`	`2004`	`07`	`20`	`19`	`15`
`2453210.8273`	`2004`	`07`	`24`	`07`	`51`
`2453214.3521`	`2004`	`07`	`27`	`20`	`27`
`2453217.8769`	`2004`	`07`	`31`	`09`	`02`
`2453221.4016`