Space

Astronomers spot warm, smoking gun of a recent exoplanet collision

Astronomers spot warm, smoking...
An artist's impression of a planetary collision in the system BD +20 307
An artist's impression of a planetary collision in the system BD +20 307
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An artist's impression of a planetary collision in the system BD +20 307
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An artist's impression of a planetary collision in the system BD +20 307

So far we’ve found over 4,000 exoplanets out there in the cosmos, orbiting their stars in peace. But if they’re anything like our own solar system, they’re probably hiding turbulent histories where exoplanets smashed into each other, leaving dusty debris in their wake. And now, astronomers have found evidence of just such a cataclysm happening in the relatively recent past.

The scene of the accident is a system called BD +20 307, which sits more than 300 light-years from Earth. Here two stars, each over a billion years old, orbit each other in close proximity. The evidence of the accident? A cloud of debris that’s still warm.

It’s not unusual for stars to be surrounded by clouds of debris – even our own Sun has a few, in the form of the asteroid and Kuiper belts. These are believed to be the fragments and leftover dust from collisions between many ancient planets, but after chilling in space for 4.5 billion years or so, nowadays they’re very cold.

Given the two stars in BD +20 307 are over a billion years old, any debris clouds there should be well and truly cold by now. And yet, infrared observations by the Spitzer Space Telescope 10 years ago revealed that the dust there was still quite warm, indicating a large-scale planetary collision must have occurred in the system relatively recently.

And now the evidence has grown stronger, with new observations by NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA). The team found that the Infrared brightness of this debris has gone up by about 10 percent since the previous observations, indicating there’s more warm dust floating around now than there was a decade ago.

“The warm dust around BD +20 307 gives us a glimpse into what catastrophic impacts between rocky exoplanets might be like,” says Maggie Thompson, lead author on the study. “We want to know how this system subsequently evolves after the extreme impact.”

The team says that there are other possible explanations for why the dust might be glowing brighter now. The clouds could have drifted closer to the stars, or might just be absorbing more heat from them than previously. But these scenarios would be unlikely to happen in the space of just 10 years, which is the blink of an eye on the cosmic scale of things.

That leaves a planetary smash-up as the most likely explanation. This would inject a large amount of new, warm dust into the system over a very short timeframe.

The researchers plan to conduct follow-up observations and continue analyzing the data to watch out for further changes in the system.

The research was published in the Astrophysical Journal.

Source: NASA

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