Updated from 5:38 p.m. EST

Apple

(AAPL) - Get Report

said Wednesday that CEO Steve Jobs will take a medical leave of absence from the iPhone and Macintosh maker until the end of June.

The company released a letter from Jobs after the market closed and said Chief Operating Officer Tim Cook will be responsible for Apple's day-to-day operations while Jobs is away.

Jobs said in his letter that "the curiosity over my personal health continues to be a distraction not only for me and my family, but everyone else at Apple as well. In addition, during the past week I have learned that my health-related issues are more complex than I originally thought."

var config = new Array(); config<BRACKET>"videoId"</BRACKET> = 7255740001; config<BRACKET>"playerTag"</BRACKET> = "TSCM Embedded Video Player"; config<BRACKET>"autoStart"</BRACKET> = false; config<BRACKET>"preloadBackColor"</BRACKET> = "#FFFFFF"; config<BRACKET>"useOverlayMenu"</BRACKET> = "false"; config<BRACKET>"width"</BRACKET> = 265; config<BRACKET>"height"</BRACKET> = 255; config<BRACKET>"playerId"</BRACKET> = 1243645856; createExperience(config, 8);

For months, Apple investors have been worried about

Jobs' health

. He had pancreatic cancer in 2004, and last year he

appeared thin

in public appearances. That led to continuing speculation about his wellness.

In an effort to finally answer questions about his health, Jobs earlier this month said a hormone imbalance had led to his weight loss last year. Now though, just days later, he says he'll step aside, at least for the next few months.

Shares of Apple were halted in late trading, but when they reopened, they fell 10% almost immediately. Apple shares closed regular trading at $85.33, down 2.7% on the day.

"I am surprised, but I am not shocked. There were indications that this might happen," says Ezra Gottheil, an analyst at Technology Business Research. "My conclusion is that the company is well situated to endure Jobs' absence, even his departure."

var config = new Array(); config<BRACKET>"videoId"</BRACKET> = 7255740001; config<BRACKET>"playerTag"</BRACKET> = "TSCM Embedded Video Player"; config<BRACKET>"autoStart"</BRACKET> = false; config<BRACKET>"preloadBackColor"</BRACKET> = "#FFFFFF"; config<BRACKET>"useOverlayMenu"</BRACKET> = "false"; config<BRACKET>"width"</BRACKET> = 265; config<BRACKET>"height"</BRACKET> = 255; config<BRACKET>"playerId"</BRACKET> = 1243645856; createExperience(config, 8);

With its three iconic product lines of Mac computers, iPhone smartphones, and iPod music players, Gottheil feels that Apple's core offerings are strong enough to carry the company's stock, even without Jobs at the helm. Apple, which sold 6.9 million iPhones in its third quarter, also has a strong management team and culture, he said.

On the financial side, Apple has more than $24 billion in cash, which should also insulate it against any future problems.

Jobs said by handing over control to Cook he could concentrate on his health and "allow everyone at Apple to focus on delivering extraordinary products." He added that he would "remain involved in major strategic decisions" while he's out.

The Cupertino, Calif., company, which has become one of the most respected consumer-technology names in the world, is much more associated with Jobs, one of its founders, than the bulk of companies are to their own executive leadership. Jobs, after all, is one of a handful of celebrity CEOs.

Not that's always been that way. After a spat with the board led to his ouster from the company he helped get off the ground, Jobs returned to Apple in the late 1990s and oversaw its rebirth at a time that PCs based around

Microsoft's

(MSFT) - Get Report

Windows platform were dominating computing.

By embracing a rebel image and casting itself as a trendy alternative to the software from Redmond, Wash., and the beige boxes sold by the likes of

Dell

(DELL) - Get Report

and

Hewlett-Packard

(HPQ) - Get Report

, Apple regained the relevance it had been losing during Jobs' first time away from the company.

One of the early successes after Jobs returned was the original iMac, a blue-and-white desktop machine that stood out from the competing look-alike PCs on the market. Subsequent years would see various versions of the iPod and in 2007, the rollout of the iPhone, a smartphone that has kept the

Research in Motions

(RIMM)

and

Nokias

(NOK) - Get Report

of the world honest with their own offerings.

Because many of Apple's brightest days have occurred with Jobs at the helm, investors can be forgiven if they're tempted to flee at the thought of an Apple minus its current CEO. At the same time, it's worth remembering that he isn't the only clever employee of the tech company that's been to the brink and fought its way back to become a household name.

Tim Cook, the company's COO, has earned a reputation as a safe pair of hands, although he lacks Jobs' star quality.

Cook's management abilities should not be under-estimated. The executive heads Apple's crucial Mac division and is also responsible for the company's worldwide sales and operations, so he knows a thing or two about marketing the company's all-important brand. The former

IBM

(IBM) - Get Report

executive also worked at

Compaq

and

Intelligent Electronics

prior to joining Apple.

"Cook is kind of the steady hand at the tiller," says Gottheil, explaining that Cook also took the Apple reins when Jobs was being treated for cancer.

Gottheil, however, acknowledges that Apple could feel the impact of Jobs' absence, particularly when it comes to identifying opportunities to sell cutting-edge technologies.

"If Jobs is not coming back, Apple might not have the consistent ability to take these innovative leaps into new businesses and new product lines," he said.