Expert: Tom Whiting - 10/21/2008

Question
hi I'd like to know how far away Orion is from us and how long it would take to go there cause I have to do a project about it.

well thanks

Answer
Hi Erikca,
Well, a constellation...Orion, Leo, Scorpius, whatever....is just an area of sky just like a USA state.  Some stars and objects are relatively close, and others are farther away.  It's only a 'line of sight' arrangement, just like if you are looking a nearby telephone pole almost aligned with a radio antenna far off in the distance.(The two can be 'side by side' but the radio antenna is miles awaywhereas the telephone pole may only be 100 feet away from you.)

In other words, stars and other objects in a "constellation" most of the time are totally unrelated to each other, especially the very distant galaxies that are millions of lightyears distant compared to our nearby Milky Way galaxy stars and objects. That being said, some of the stars and objects in the Orion constellation DO happen to be related in the southern portion of that area, because they are all members of the Orion complex, which includes the belt and sword stars, Rigel, and the molecular cloud called M-42 or the Great Nebula in Orion.  I will assume that is the object you are referring to. Originally thought to be some 1500 ly distant, new measurements put the Great Nebula at 1270 + or - about 70 ly.  The 3 Belt stars are scattered from 800 to 1300 lightyears, see http://www.glyphweb.com/esky/constellations/orionsbelt.html
and I've seen reports that puts Rigel at from 800-900 lightyears; they are all part of the Orion Complex which includes the flame Nebula, M-78, and Barnard's Loop. Realize that absolute distances are one of the most difficult items to determine in astronomy....we can't use a tape measure, so all distances are done indirectly in some manner, and typically have at least a 10-20% built in error.

As far as travel time out to say, any object at 1300 lightyears distant, it depends on the velocity that you are traveling. But if you are up very very very close to light speed, obviously it would take 1300 Earth years to make a one-way trip.  But from the spacecraft's standpoint (Einstein's Special Relativity and the Time Dilation Effect) you might only take a few months to get there, and a few months to return at that same velocity. But don't plan on coming back to the same Earth you left, because over 2600 years (1300 doubled) will have advanced on this Earth, whereas only a few months would have passed by in your spacecraft going 99.999999999999999+% light speed. So you'd be returning in about the year 4608 AD.  (The original movie "The Planet of the Apes"...got it right...the time dilation effect of near light speed space travel, not the apes).
Hope this helps,
Clear Skies,
Tom Whiting
Erie, PA

FOLLOW UP:
Oh, for some great pictures of the Orion Nebula (M-42) and the
latest distance to same, see
http://en.wikipedia.org/wiki/Orion_Nebula
tom