Now, using a relatively new optical observational technique that produces data but not images, researchers have made the first direct measurements of one particular star suspected of having such a bulge. And they found a whopper of a gut.

The diameter of Altair, a fast-spinning star now clearly visible in the summer night sky across North America, as part of the Summer Triangle, is 14 percent greater at the equator than when measured at the poles.

The finding confirms previous observations that had hinted at this oblong shape. Other studies had shown that Altair rotates about its axis very rapidly -- once every 10.4 hours -- so scientists already figured it would be fat in the middle. In contrast, our Sun rotates once every 30 days or so and is less than 1 percent larger in diameter at its equator compared to its poles.

The new study began when scientists used a pair of telescopes at the Palomar Testbed Interferometer to study the shape of Altair. The technique of combining light from two telescopes, in this case separated by a distance roughly equal to a football field, is called interferometry, and it emerging as a boon to the study of individual stars and their shapes and sizes.

Upon first glance, Altair appeared to vary in size when viewed from different angles as it moved through the sky. This indicated that the star might not be spherical.

"This surprising observation led to a bit of challenging detective work to properly interpret the data," Gerard van Belle of NASA's Jet Propulsion Laboratory said in a press release. "We measured the size of another star, Vega, at the same time, which didn't change with angle, so we knew this wasn't just a fluke of the telescope."

The researchers also calculated Altair's speed of rotation to be at least 470,000 mph (210 kps).

"Altair is the twelfth brightest star in the sky," ," said David Ciardi, a University of Florida researcher an co-author with van Belle of a paper on the findings slated to appear in the Astrophysical Journal. "You'd think that everything there is to know about this star would have been discovered already

He cited the finding as a good example of the surprises that come with "unprecedented resolution."

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