What sort of gift is it that lets David Letterman play the American networks like yo-yos? CBS have had to come up with a $71m package to stop their sardonic and highly popular late-night talk-show host being poached by ABC. Letterman barely conceals his disdain for his bosses, but he appeals to a key target audience of younger viewers, and CBS cannot afford any slippage of advertisers to their rivals. In short, Letterman has the broadcaster over a barrel, which suits an aggressive and single-minded Aries (12 April 1947) just fine.

Like most Aries Rams, Letterman doesn't bother with the niceties, but the sign has a what-you-see-is-what-you-get quality that inspires trust. However, the touch of genius that comes through his quirky humour and his rapid-response improvisation are down to off-beam Uranus in communicative Gemini, closely linked to his Sun. This combination is "strong and independent... it is a very popular configuration, and the native is readily liked and obeyed...[his personality] appears to emanate some kind of magnetism that attracts and holds. It is not always tactful." (Charles Carter, Astrological Aspects).

Aries is hardly a team player, and by all accounts Letterman is tough to work with, but it is clear from his horoscope that his dedication to his show reflects an exacting standard that he sets himself, rooted in self-disciplined Saturn in creative Leo, giving him a fear of failure and mediocrity. This combination adds an occasional spike of bitterness to his humour, as well as a self-mocking capacity that is uncharacteristic of fiery Aries. There is nothing light and easy about this, it is driven and tense.

Letterman's powerful Uranus has been activated this year, so it is no surprise that he has come to the fore at the top of his game. It looks like he has everything just as he wants it, although there is a troublesome glitch this June when a solar eclipse falls within a degree of his Uranus. The sort of thing to watch for is losing his rag, coming out with an outspoken comment, or a skit that goes way over the top. The advice to Letterman around this time is: keep away from the edge, you might fall off.

But Letterman hasn't got where he is by listening to advice, and Ariens never bother much about what other people think. In any case, apart from this summer's hiccup there is little to suggest that he will come off his perch in the next few years. The timing of his horoscope favours a three-year renewal of his contract but nothing longer. In 2005 the Sun progresses to Uranus and Letterman really does have to think of breaking out of the track he has carved for so many years and get himself (another) life.