What happened

Shares of space tourism pioneer Virgin Galactic (SPCE -1.20%) were on a tear Tuesday, up 12.2% as of 1:15 p.m. EDT.

You can probably thank Morgan Stanley for that -- and SpaceX, too.

Rocket trail from Earth to sky ending in what looks like a star

Image source: Getty Images.

So what

News is starting to filter out about a just-released report from Morgan Stanley in which the investment bank's space investing team estimates that Elon Musk's SpaceX could be worth as much as $175 billion.  

Yes, you read that right. This is a report about SpaceX. It's not about Virgin Galactic at all. And yet, it's Virgin Galactic's stock that appears to be benefiting from it, presumably on the theory that if SpaceX is worth $175 billion, then another space company like Virgin Galactic just has to be worth more than the $4.8 billion or so it was valued at on Monday.

Now what

Is that a reasonable assumption? Perhaps not. But when you consider that both SpaceX and Virgin Galactic are in the "space business," broadly defined, and when you consider that SpaceX doesn't have a publicly traded stock that investors can bet their money on -- but Virgin Galactic does ­­-- well, it actually kind of does make sense that investors might try to trade Virgin Galactic as a way to invest in enthusiasm about space in general, and SpaceX in particular.

That doesn't mean that investors are right, to do so, however -- to buy shares in unprofitable Virgin Galactic when what they might really want to own is profitable SpaceX. And for those who really do want to own a piece of it, there is, in fact, a viable way to invest in SpaceX itself, albeit not directly.

There's a popular and profitable tech company that also happens to own a stake in SpaceX. So before buying shares of Virgin Galactic at 1,630 times sales to get some space exposure in your portfolio, you might want to consider investing in that company instead.