Astronomers have found 13 candidate planets flying so close to their parent stars that a year on these worlds lasts between just three and 10 hours.
If confirmed, the planets, which were found by NASA's Kepler space telescope, would add another twist to the quirky and dynamic relationship between stars and their orbiting planets.
"This does really force us to think hard about how planets form, where they can live and how they evolve. It seems like almost anytime you think of something crazy to go looking for, it's out there somewhere," astronomer Brian Jackson, a postdoctoral fellow at the Carnegie Institution for Science, told Discovery News.
"Like almost every discovery in extrasolar astronomy, it is basically causing people to have to go back and rewrite the textbooks," he said.
For starters, astronomers do not know how the candidate planets ended so close to their parent stars, nor where they came from. The shortest distance between one of the newly found candidate planets and its host stars is about 865,000 miles. That suspected planet orbits its star every 3.3 hours.
By comparison, Mercury, the innermost planet in our solar system, is located about 36 million miles from the sun and it takes 88 days to complete an orbit.
"It's been suggested for some time that the really hot super-Earths that are in close (to their host stars) are just the cores of evaporated ‘'hot Jupiters,'" University of Maryland astronomer Drake Deming told Discovery News.
Hot Jupiters are a type of extrasolar planet -- not found in our solar system -- where gas giants, similar to Jupiter and Saturn, orbit sizzlingly close to their host stars. These planets are believed to have solid cores of rock and ice deep in their interiors.
The candidate planets found by Jackson and colleagues may be what remained after hot Jupiters wandered too close to their parent stars and had their atmospheres stripped away.
Computer models suggest that any gas giant cores eventually would vaporize or make death spirals into their parent stars, but the Kepler data shows the objects may last long enough to be detected.
More work remains to eliminate the possibility that the light dips detected by the Kepler telescope are due to planets passing by, relative to Kepler's line of sight, and not eclipsing binary stars.
The new analysis covers Kepler observations made between late 2009 and January 2012. The telescope currently is not working due to a failure of its pointing system. Engineers are attempting to revive the observatory, which was designed to find Earth-sized planets orbiting host stars at the right distances for liquid water to exist on their surfaces. Water is believed to be essential for life.
In the process of looking for Earth-like worlds, astronomers are uncovering a proverbial cosmic planetary zoo.
"These planets are just weird," Jackson said.
The research appears on online at arXiv.org and will be published in an upcoming issue of The Astrophysical Journal.