U.S. Equities Icahn Doubles Stake In Chesapeake Energy, Sends Stock Flying Agustino Fontevecchia, 12.20.10, 12:55 PM EST With year winding down billionaire makes another move. Chesapeake Energy Corporation 12/20/2010 2:19PM ET$25.05$1.757.51%At A GlanceChartNewsPeople Full CHK Chart at Dynegy Inc. 12/20/2010 2:19PM ET$5.65$0.020.36%At A GlanceChartNewsPeopleFull DYN Chart at Lions Gate Entertainment Corp. 12/20/2010 2:15PM ET$6.72$0.091.36%At A GlanceChartNewsPeopleFull LGF Chart at BATS Real-Time Market Data by XigniteBillionaire Carl Icahn showed that he's got ants in his pants. With the end of an active year just days away, Icahn more than doubled his position in Chesapeake Energy, sending the stock through the roof in a very light session Monday. Considering that the shares were "undervalued," billionaire Carl Icahn increased his stake in Chesapeake Energy ( CHK - news - people ) to 38.6 million shares, from 16.6 million. The move, valued at about $500 million since shares were purchased in the $22.72 to $22.89 range, raises Icahn's stake to 5.9%, making him the second largest shareholder behind Southeastern Asset Management. Article Controls email print reprint newsletter comments share del.icio.us Digg It! yahoo Facebook Twitter Reddit rss Yahoo! BuzzIcahn recently reached an agreement to acquire electric utility Dynegy ( DYN - news - people ) for $5.50 per share, or $665 million in cash, for a total of $4.7 billion including assumption of its debt. The investor, known for his active engagement of management in companies he holds big stakes in, recently lost a fight with Lions Gate Entertainment ( LGF - news - people )'s board over a possible merger with MGM. (See "Caught in the Crossfire: Lions Gate's Value as Icahn Battles Board.") Chesapeake Energy has suffered from the steep drop in natural gas prices, with its stock down more than 10% for the year. While prices for energy sources such as oil and coal have gained handsomely in 2010, natural gas prices have been hindered by excess supply. The January 2011 contract priced in at $4.14 at midday Monday. CEO Aubrey McClendon has been shedding assets to focus on oil production, according to Bloomberg. Year-to-date, Chesapeake has sold $3.6 billion in assets this year in order to focus on accelerating its crude oil business. Stock in Chesapeake Energy skyrocketed Monday, gaining 7% or $1.62 to $24.92 on news of Icahn's increased stake