What happened

Shares of space stock AST SpaceMobile (ASTS 5.12%) jumped out of the gate Tuesday, soaring as high as $9.50 by 11:11 a.m. EDT -- an 18.5% gain.

It's given back some of that since, but its gain today is still impressive! 

Cartoon rocket zooming up like a stock on a chart

Image source: Getty Images.

So what

AST SpaceMobile aims to turn every cellphone in the world into a satellite phone using "highly proprietary" technology -- so super-secret that "exactly how it works cannot be disclosed," says the company. But the stock has suffered since coming public via a special purpose acquisition company (SPAC) in April, falling 20% below its initial valuation of $10 as of yesterday's close.

On Monday, however, rumors began floating that AST might soon be added to the Russell 2000 index of small companies. That would require mutual funds and ETFs that track the index to buy AST shares, presumably pushing up the price.  

Now what

And those rumors could be correct. Currently, the smallest stock on the Russell 2000, biotech Bellerophon Therapeutics, carries a market capitalization of barely $42 million. Despite its recent stock price collapse, AST has a market cap more than 10 times as big: nearly $470 million.  

If market cap is any guide (and it should be), then AST's eventual inclusion in the Russell 2000 seems all but assured. That won't be enough to turn the company profitable, of course. But it could still be good news for the stock price.