Celestia Forums

If we get a spacecraft (manned or otherwise) to pluto by the time displayed in the screenshot, we will have a chance to see our own home planet transit the sun as seen from pluto.



I made this discovery last summer, and I emailed some astronomer, but I never heard back, so I figured I'd post here to share my discovery with the rest of the world.

Given the high inclination and long period of Pluto's orbit, an Earth transit of the Sun as seen from Pluto is a rather rare event (perhaps once in a hundred years), but the phenomenon is hardly of that much interest to astronomers, as there is little to study.

When Saturn was in opposition on January 13-14 this year, the Earth spent nearly 12 hours transiting the Sun as seen from Cassini, which was however busy preparing for the Huygens data relay operation. I wondered if perhaps solar radiation might interfere with command signals from Earth to Cassini, but since nobody even mentioned the event I suppose the radio link isn't vulnerable to such interference. In any case, everybody here on Earth were (justifiably) more concerned with the Huygens landing than with taking snapshots of themselves sunbathing...

A more important event would be the Sun obscuring the line of sight between Earth and some interplanetary spacecraft, interrupting communications. This is however carefully accounted for in mission planning, and while it doesn't seem to have happened to Cassini, there was a close conjunction between Earth and Sun on July 8, 2004, just a week after Saturn Orbit Insertion. Saturn crossed the ecliptical plane on January 8 this year, bringing Cassini along, and a similarly close conjunction will take place on July 23, but every conjunction after that (at least until mission completion in 2008) will be less dramatic.

Interesting, but there's no way any spacecraft would be able to image the earth transiting the sun - the imaging CCDs would either oversaturate (if you're lucky) or burn out if they pointed at the sun.

There are 56 occurences of this phenomenon from year -3000 to year 3000

Date Time
-2919/06/02 18.11
-2762/11/30 04.17
-2761/11/30 16.10
-2516/12/01 05.24
-2515/12/02 17.11
-2270/12/03 04.32
-2269/12/03 16.38
-2024/12/04 01.16
-2023/12/05 13.13
-1935/06/08 07.47
-1777/12/06 06.13
-1689/06/08 19.46
-1531/12/07 20.49
-1443/06/09 23.40
-1285/12/08 07.46
-1284/12/09 19.29
-1196/06/12 04.39
-1038/12/11 04.13
-0950/06/13 00.28
-0792/12/11 09.37
-0791/12/12 21.23
-0703/06/14 21.15
-0545/12/13 00.23
-0544/12/14 12.03
-0456/06/16 12.51
-0298/12/15 10.09
-0210/06/16 18.14
-0051/12/16 17.45
+0197/12/17 19.51
+0286/06/21 00.31
+0444/12/18 20.25
+0445/12/20 07.48
+0533/06/21 17.06
+0692/12/21 03.59
+0780/06/22 05.14
+0939/12/22 22.16
+1028/06/24 17.25
+1186/12/23 13.30
+1187/12/25 00.49
+1275/06/25 21.05
+1434/12/25 13.49
+1523/06/28 00.48
+1683/01/06 10.47
+1930/01/09 17.51
+1931/01/11 05.18
+2018/07/12 14.23
+2178/01/12 08.46
+2179/01/13 19.56
+2266/07/16 05.18
+2426/01/15 20.42
+2427/01/17 07.55
+2514/07/19 12.39
+2674/01/19 05.21
+2675/01/20 16.25
+2762/07/22 17.10
+2923/01/23 22.40

Hmm... probably should've said "I made an interesting discovery in celestia" in the title instead... :hmm:

Since we're talking about Transits,

cel://Follow/Sol:Pluto/2005-03-15T13:19:50.92159?x=AAASztvWIz4CDA&y=CkzwtbvitwXM&z=Vcpg+InriAOBBQ&ow=0.991639&ox=0.065477&oy=0.071437&oz=0.085209&select=Sol:Pluto&fov=0.002517&ts=1.000000&ltd=0&rf=40855&lm=49154