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Once or twice a day, a strange object in the Milky Way blinks at us. Now, astronomers think they know why.
The object is called NGTS-7, and to most telescopes it looks like a single star. Researchers at the University of Warwick in England started watching because it seemed to be emitting flares, but on closer examination they noticed that its starlight dims briefly every 16.2 hours. When the astronomers zoomed in, they realized there are actually two similarly sized stars in the system, and that only one of them is dimming briefly in that way — suggesting that there's something dark circling on or just above the star's surface. Now, in a paper posted to the preprint journal arXiv, the astronomers offer an explanation: A brown dwarf is orbiting one of the stars, in an orbit so tight that it takes just 16.2 hours to complete.
Researchers - Technique - Exoplanets - Light - Dwarf
To pull it off, the researchers applied a similar technique to that used to detect exoplanets: Measuring how the light dipped as the brown dwarf passed between its host star and Earth. This dip represents the signal of a "transit": a brief, partial eclipse of the star by something too small to see directly, even through a bright telescope.
"Detecting this system is probably the easy bit," Osborn told Live Science. "Because the star is so small and the brown dwarf relatively large, the transit signal is actually about 10 times larger than that of [a typical exoplanet that turns up in surveys of the night sky]."
Transit - Signal - Sense - Transit - Signals
But once you detect the transit signal, you have to make sense of it. That's tricky because brown dwarf transit signals are strange. For one thing, they tend to glow faintly from internal heat and the heat of nearby stars.
"The typical brown dwarf temperature is somewhere between luke-warm water, which...
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