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A star that appears to wink may have planets or even asteroids circling around it, astronomers announced on Wednesday. Star KH 15D is about 2,400 light-years away in the constellation of Monoceros and is part of a well known cluster of young stars called NGC 2264. Observations over the last year, by an international group of scientists, has revealed changes in brightness that may be caused by planets or asteroids churning up a disk of dust that surrounds the star. Although many stars show similar changes in brightness what makes KH 15D special is that it stays faint for 18 days. Other stars remain faint for much shorter times because the second 'partner' star, which passes in front of them, is quite small. In KH 15D the eclipse, which makes the star faint, must be due to extended bulge of dust in the disk surrounding it. Because KH 15D becomes faint every 48.3 days astronomers believe that the bulge in the disk, and the planets or asteroids that cause it, is closer to the star than Mercury is to our Sun.
Planets are thought to form piece-wise by the sticking together of dust grains to form larger objects within the dusty gas disks surrounding young stars. The disks form because the gas clouds that collapse to create stars are slowly rotating. When such clouds fall in on themselves to form a star they spin faster and, therefore, flatten out into a disk. It was in the dusty disk surrounding the early Sun, 4.5 billion years ago, that all the planets, moons, asteroids and comets within our Solar System formed. Star KH 15D is only 3 million years old and thus is still very young. Astronomers expect that observations of KH 15D will thus provide us with a much better understanding of how planets and asteroids form.
More info: Spaceflight Now Article
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