Shares of Sirius XM Radio (Nasdaq: SIRI) hit a new 52-week high today. Let's look at how it got here and see whether clear skies are ahead.

How it got here
Sirius XM has seemed unstoppable lately, as Liberty Media's (Nasdaq: LMCA) pursuit of majority ownership has pushed shares ever higher. The two companies have virtually moved in lockstep over the past year:

SIRI Chart

SIRI data by YCharts.

Liberty, the parent of Starz, Encore, and the Atlanta Braves, received a 40% stake in the company when it bailed out Sirius XM in its darkest hour in 2009, and it has recently grown that stake to 49.6%. Sirius shares jumped yesterday after the Federal Communications Commission invited comments or petitions to deny the de facto acquisition, which are due by Nov. 1. Liberty has said if the FCC approves the takeover, it will buy up enough shares to give it majority control within 60 days.

While Sirius shareholders may be flattered by Liberty CEO John Malone's interest, it's unclear what will happen to the satellite-radio company should Liberty become the majority owner. Malone has been critical of Sirius XM CEO Mel Karmazin for not expanding internationally or improving its technology. Karmazin, meanwhile, has suggested that he and the rest of the board could be ousted following the takeover. For now, shares seem to have climbed mainly because Liberty has been soaking them up, with many analysts and investors thinking a large share buyback will follow.

What's next?
Some of this enthusiasm could be a bit overblown, as financial acrobatics can propel a stock only so far. While the company has taken formidable strides in recent quarters, adding subscribers at a strong pace and improving its product line with the addition of an on-demand service, there are a number of potential concerns further down the road.

Howard Stern is still the entertainment provider's No. 1 draw, and his contract expires in 2015. He's 58, and many expect him to retire when the current agreement ends.

Sirius XM thus far has thrived in spite of Internet radio specialists such as Pandora (NYSE: P), but competition could heat up in that area, as Apple (Nasdaq: AAPL) has announced plans to enter the market. A bill in Congress to lower royalty rates for streaming services, which pay higher prices than Sirius XM, could also provide a boost for the Internet DJs.

Finally, Sirius XM's fortunes are closely tied to the auto industry; a weak economy and the looming fiscal cliff could leave auto sales lagging.

At an adjusted P/E of 24, Sirius shares aren't cheap, not to mention the nearly $3 billion in debt on its books. The recent bull run could continue as Malone swallows up more shares, but Foolish investors may want to keep the long-term threats in the back of their mind even as shares move higher.

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