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1 .This is Scientific American's 60-Second Space. I'm John Matson. Got a minute?
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2 .Watch for falling rocks.
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3 .Those are words to keep in mind when you're driving a mountain road.
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4 .Or, it seems, when you're cruising past a white dwarf star.
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5 .White dwarfs are small, dense remnants of normal stars that have expended their fuel.
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6 .Now researchers have identified rocky, asteroid-like material raining down on two white dwarfs.
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7 .The rocky material is akin to the building blocks of planets,
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8 .and its presence suggests that the two stars formed planetary systems before they expired and became white dwarfs.
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9 .That's the conclusion of a study in the Monthly Notices of the Royal Astronomical Society.
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10 .Astronomers identified the silicon-rich rocky material by training the Hubble Space Telescope on the nearby Hyades star cluster.
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11 .Finding rocky material means the stars once had the raw ingredients to make exoplanets,
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12 .although almost no known planets orbit stars inside of clusters.
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13 .The discovery of planetary material thus raises more questions.
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14 .Are star clusters indeed inhospitable to planets?
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15 .Or are planets around stars in clusters for some reason just harder to spot?
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16 .In the Hyades cluster, at least, it looks like there may be planets that have so far escaped our notice.
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17 .Thanks for the minute, for Scientific American's 60-Second Space. I'm John Matson.
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