Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Orbital Sciences (NYSE:OA) rose as much as 28.6% in early trading today after the manufacturer of satellites and other space systems announced a merger with Alliant Techsystems (NYSE:ATK). Shares settled at a 16% gain later in the day.  

So what: Alliant is splitting itself into a sports business that makes ammunition and rifles and an aerospace and defense company, effectively fusing its military and government contract businesses together while splitting off the commercial side. The aerospace and defense portion will then be merged with Orbital Sciences, and shareholders will receive 0.449 shares of Alliant Techsystems for each share of Orbital common stock.  

Now what: The merger brings together two companies with complementary products in space and rocket technology, and that already have a significant track record of collaboration. I like the move overall and would hang on after this gain because this development should be good for both companies' shareholders in the long term.

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Travis Hoium has no position in any stocks mentioned. The Motley Fool recommends Orbital Sciences. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.