For years now, I have believed that there were nine planets -- no more, no less. You can imagine my surprise then when I picked up the newspaper and learned that 2,000 astronomers are now meeting in Prague, where they are seriously debating the possibility of adding three new celestial bodies to our well-known solar system or, alternatively, dropping one existing planet. The three new bodies go by the names Ceres, Charon, and Xena. The poor planet on the chopping block is Pluto.

This celestial reconfiguration got to me to thinking about a different kind of reordering, namely portfolio reconfiguration.

Can the old be new?
Of the three bodies up for planethood, the one that astonished me the most was Ceres. It had been considered a planet back in the 1800s, only to be demoted to asteroid status for reasons I don't entirely understand.

To my mind, this makes Ceres somewhat akin to a solid stock that was once a core holding in your portfolio, but was then dropped for dubious or short-sighted reasons, or because it was out of fashion. For instance, many stockholders have recently dumped Microsoft (NASDAQ:MSFT) and UnitedHealth Group (NYSE:UNH) -- both Motley Fool Inside Value recommendations. A compelling case, however, could be made that both companies are undervalued at the present time and are worthy of being added back to your portfolio.

In the case of Microsoft, the fact that sales for both the SQL server and the Xbox 360 are strong bodes well for the company's future growth. In UnitedHealth Group's case, its leadership as the top provider of Medicare Part D, in combination with its tight association with AARP, suggests that it is very well positioned to continue to serve the growing legions of aging baby boomers -- the first of whom are turning 60 this year.

Are there new finds on the horizon?
I liken Charon, now better known as Pluto's largest moon, to a hidden gem, in that it is easy to overlook. In this way, it is somewhat like current Hidden Gems selection Sadia (NYSE:SDA). Because the company is in an unsexy area (food processing) and is located in a distant, far-off land (Brazil), it is easy for investors to overlook. But if you are a serious investor, it is the kind of stock that might make sense to add to your portfolio because of its ability to expand into growing markets such as the Middle East and, of course, Latin America, where per capita consumption rates for Sadia's frozen food products are increasing at a healthy annualized clip of 15%.

Next, we come to my favorite, Xena -- which, in case you were wondering, was, in fact, named by its discoverer after the warrior princess of TV fame. (Unfortunately, the more stodgy members of astronomy community call it UB313 and are likely to rename it should they deem the celestial body worthy of being a planet.)

Xena is the farthest-known object in the solar system and can be compared to a stock like Motley Fool Rule BreakerHarris & Harris (NASDAQ:TINY), in that it occupies a somewhat distant and risky field. It is, however, the kind of stock that could do wonders for expanding your portfolio returns.

The publicly traded venture capital firm specializes in investments in the exciting new world of nanotechnology and has equity stakes in a number of "small tech" companies that are involved in everything from the production of next generation integrated circuits, flexible solar cells, and new drug discovery technologies, to quantum computing.

Or is it time to drop a familiar name?
Finally, it is entirely possible that the astronomy community might decide to add no new planets and just drop Pluto. In the unlikely event that this does occur, it would be the equivalent of dropping a good old standby like Wal-Mart (NYSE:WMT) from your portfolio. Sure, given that the retailing giant just reported its first quarterly loss in ten years, a case could be made that the company is now out of fashion; but it would seem like a rash thing to do without the proper due diligence.

Foolish bottom line
Now, I am not sure which -- if any -- of these bodies will become planets (or in Pluto's case be dropped), but my point is this: if 2,000 astronomers can consider adding three new planets, or subtracting one, to our existing solar system, I think the average investor can considering realigning his or her portfolio with both old and new stocks.

In fact, I would argue that not only is such a reordering a healthy thing to do on occasion, it is indeed an essential element if we ever hope to more fully contemplate -- and ultimately understand -- the broader investing universe.

Looking for stocks that are more down to earth? Consider a taking a free 30-day ride on either Motley Fool's Inside Value or Stock Advisor. If you are more interested in exploring unknown places, try a ride on the Hidden Gems. And if you are looking for an out-of-this-world experience, consider a free 30-day spacewalk with Rule Breakers.

Microsoft, Wal-Mart, and UnitedHealth are Motley Fool Inside Value recommendations; UnitedHealth is also a Stock Advisor selection. Sadia is a Hidden Gems recommendation, and Harris & Harris is Rule Breaker recommendation.

Jack Uldrich is more interested in boldly going where no man has gone before. He is the author of two books on nanotechnology, including Investing in Nanotechnology: Think Small, Win Big. He owns stock in Microsoft, UnitedHealth, and Harris & Harris. The Fool has a strict disclosure policy.