Celestia Forums

Does anyone know the date when all the planets of the Solar System line up?

Never the way you're probably thinking. They all lay on slightly different planes of inclination, so from the perspective of an observer on the sun they would never line up perfectly... This site at Griffith Observatory has some good information on planetary alignments. There will be a very close alignment of the visible planets in September of 2040 and http://www.griffithobs.org/SkyAlignments.html

And this day...April 8, 2024 is not an alignment per se, but it will be a very cool observation. Total Solar Eclipse from Mexico and all major (not Pluto) planets are visible along the ecliptic.

So its near impossible in real life but how would I create it in Celestia?

I'm not sure if you mean
"create an imaginary situation in Celestia that shows planets lined up"
or
"set Celestia to a date when many planets are almost aligned"

A date when many planets were aligned was May 5, 2000.

Run Celestia
Open the menu "Time"
Select the entry "Set Time"
type 5 in the day field
type 5 in the month field
type 2000 in the year field
Select the "OK" button

Change your viewpoint and Render options to see how they look.

Here's a view from far above the Sun.


(click on this picture to see a much larger version)

[edit]
A similar alignment happened on September 2nd, 1861.
Setting Celestia's time and viewing it is left as an exercise for the reader

See http://drumright.ossm.edu/astronomy/conjunctions.html
for more information.
[/edit]