All the members of Orion are within the Milky way, and some of them look pretty close to a neighbor. And could the bow* be an effect similar to the Radcliffe Wave?


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    $\begingroup$ What is a "Radcliffe Wave"? What does "All the members of Orion" mean? How many stars are you talking about? Thanks! $\endgroup$ – uhoh Feb 16 at 1:49
  • $\begingroup$ Maybe include a link. It's an interesting question and the article suggests that the Radcliffe wave is in the same part of the sky (when viewed from Earth) as Orion's belt and other constellations, but viewed from Earth and in the same part of space don't necessarily go hand in hand. It says star formation happens in the Radcliffe wave, but the stars in Orion's belt are HUGE and two of the systems are fairly close to each other, the 3rd is quite far. My guess would be different formation events, but it's just a guess. space.com/radcliffe-wave-largest-milky-way-structure.html $\endgroup$ – userLTK Feb 16 at 6:35
  • $\begingroup$ Orion's belt, sword and nebula are more-or-less at the same distance $\endgroup$ – Rob Jeffries Feb 16 at 9:17
  • $\begingroup$ @userLTK Betelgeuse is not in Orion's belt. The three belt stars are Alnitak, Alnilam and Mintaka. Despite what you read on wikipedia they are (along with sigma Ori) thought to be at a similar distance. There can be major problems with Hipparcos parallaxes to bright, multiple stars. $\endgroup$ – Rob Jeffries Feb 16 at 16:31
  • $\begingroup$ @RobJeffries I know, but you said belt, sword and nebula - which I may have miss-read. I should have checked. There's still about 800 light years between the more distant star and the other two in the belt (star systems not stars - minor point). Maybe that can happen in a few million years if the one star has high enough velocity. I'll delete the other comment, but it's still about 800 light years. $\endgroup$ – userLTK Feb 16 at 18:53

The three stars in Orion's belt, along with Sigma Orionis and the Orion Nebula cluster, along with several other young clusters and star forming regions in the central Orion region are all part of the Orion OB1 association at a distance of 350-420 pc.

A review of Orion OB1 can be found in Bally (2008). The three belt stars are probably a similar age and distance and form the brightest stars of the OB1b sub-association. Measured distances to these stars are individually rather uncertain, but better estimates come from the low-mass, co-moving stars around them. It is therefore true to say that the individual distances to each star are not known well enough to be sure that they are close together in distance.

The other bright stars in Orion - Betelgeuse, Rigel, Bellatrix, Saiph are significantly closer than this by 150-300 pc and probably not at a common distance. It has been speculated in the past though that these stars and the Orion OB1 association are part of one, large star forming complex, extending 200-300 pc along the line of sight (Bouy & Alves 2015).

The recent paper, claiming the discovery of a "Radcliffe wave" gas structure in the solar vicinity, does include the young stars in Orion as part of this structure.

So to spell it out: The belt stars are within 70pc of each other in terms of distance. If they are at a similar distance of 400pc, their angular separation on the sky of around 3 degrees, translates to a tangential distance separation of about 20 pc. Other members are more separated than this.

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    $\begingroup$ I think the question involved how close these stars are to each other rather than how close they are to us. $\endgroup$ – antlersoft Feb 16 at 17:13
  • $\begingroup$ @antlersoft How far away they are from us is what mostly determines their relative separation, since at a distance of 400pc, the belt stars have a tangential separation of 20pc at most. The other stars are separated by 100s of pc. $\endgroup$ – Rob Jeffries Feb 16 at 18:16
  • $\begingroup$ Without Gaia-type data you probably can’t answer that, how else would you plug in all those member coordinates, the Orion’s belt scale gives a naive (angular without radial) thumb method of approximating those distances, thanks. $\endgroup$ – Gabe Fernandez Feb 17 at 18:21

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