If, as a child, you ever wondered where the hole in your doughnut went, you pondered a question similar to the one that intrigues astronomer Stanley Dermott.
Well, almost. What puzzles Dermott exists 200 light-years away and involves a binary star system and a possible planet. But there is still that curious doughnut-shaped batch of material, and an even more curious hole in the middle.
Dermott isn't sure how the hole got there, but in Tuesday's issue of the Astrophysical Journal, the University of Florida professor indicates that the hole may represent an area swept clean by one or more planets.
If he finds the planet (or planets), his research may yield a working method for seeking worlds outside our solar system.
Dermott's technique -- running infrared images, taken by the Keck telescope in Hawaii, through complicated computer programs -- has a useful distinction from other methods. If it works, it could pick out planets that are farther from their host stars than any ever found. Such a planetary system may be more like our own, and therefore more apt to harbor an Earth-like planet.
"The big advantage of the work is that it is capable of indicating the presence of planets even if these planets are, like the Earth, very small," Dermott said. "This hole could represent a place that has accreted into planet." He added that he will not be able to confirm this until more data is collected.
Like many other stars, HR 4796 is surrounded by a disk of dust particles -- material left over from when the star formed about 10 million years ago. Observations of the doughnut-like disk revealed that one side was slightly brighter than the other, said Mark Wyatt, who researched with Dermott. The astronomers believe this disparity could be the result of the gravitational impact of an unseen planet shifting the dust disk slightly off-center in relation to the star.
"Because the center of the doughnut is offset, one side is closer to the star, so that side is hotter and brighter," Wyatt said.
HR 4796 is part of what is known as a binary star system. It has a companion star nearby. In the neighborhood of our sun, binary systems are thought to be more common than single stars.
It's possible, the researchers say, that the companion star could be shifting the dust disk, so more observations are needed to confirm whether the researchers are in fact seeing the effects of a planet.
The search continues
Astronomers have discovered about 30 planets outside the solar system. But current techniques favor the discovery of very large planets (bigger than Jupiter) that orbit very close to their stars. Such world's would be incredibly hot, and are not prime candidates in the search for life.
The planet that Dermott and his colleagues propose could be as far away as 50 astronomical units from its star, Dermott said. One astronomical unit is the distance between the Earth and the sun.
"We need some observations of this binary star," Dermott said. "If we knew its orbit, we could see if it accounts for the offset we see."
Dermott's field -- using variations in dust disks to search for planets -- is young, and data collected during the past year on disks around other stars has not yet been studied, he said.
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