If a massive comet struck the Earth, the oceans would boil and the air would catch fire (don't worry, this isn't about to happen). But to alien astronomers studying our planet from afar, humanity's brutal demise would look like nothing more than a faint flicker of light. If we could detect such impacts on distant worlds, we might learn a lot about their star systems.
As New Scientist reports this week, a team of astronomers is trying to figure out what it'd take for us spot a comet collision on a faraway planet. In a new paper, the researchers looked at comet Shoemaker-Levy 9, which smashed into Jupiter in 1994. According to their analysis, if a person watched that cometary collision from outside our solar system, he might observe a small uptick in Jupiter's visible light output in the months following the crash. But at near-infrared wavelengths, Jupiter would appear much brighter, because cometary dust debris would block out thick clouds of atmospheric methane (which typically absorb starlight).
Armed with this knowledge and the next generation of telescopes, astronomers may soon be able to spot cometary strikes on Jupiter-sized worlds outside our solar system. (Watching a comet strike an Earth-sized planet would take an even more powerful telescope, because our planet is so much smaller and fainter in the sky). Studying comet collisions, the researchers say, could shed light on a planet's rotation rate, atmospheric composition, and stellar neighbourhood:
How often a planet is impacted by planetesimals is intimately related to the architecture of the planetary system because the small body populations and planets evolve together. Generally speaking, planets interior to massive planetesimal belts, planets close to their stars, and planets with larger gravitational cross sections are more likely to be impacted.
And it's a long shot, but who knows — we might inadvertently bear witness to somebody else's apocalypse.
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