Photo credit: NASA
By Summer Ash
We never actually see these planets directly. Instead, when a planet crosses in front of its star, we see the light from that star decrease by a measurable amount. How much it decreases, and how long, depends on the star system—and possibly its inhabitants.
In their new paper published last week in the Monthly Notices of the Royal Astronomical Society, Kipping and Teachey ask the question: What if another civilization in our galaxy had their own Kepler Mission? What would they see when they observed our star, the Sun?
They would see a tell-tale dip in the light from our Sun. This light curve would tell them there is a planet just under 13,000 kilometers in diameter orbiting a star 1,000,000 kilometers in diameter. And if they looked long enough (over one Earth year), they would see the signal repeat and be able to deduce how far we are from the Sun and the likely range of surface temperatures we experience.
What they would not be able to see with their Kepler is evidence of life on Earth. For that, they would need to detect the presence of certain “biosignatures” in our atmosphere such as water vapor, oxygen, or industrial pollutants such as ozone. We don’t yet have the technology needed to observe these fingerprints in the atmospheres of exoplanets, at least not until the James Webb Space Telescope launches in 2018. But if this hypothetical civilization did, then they might conclude that our planet plays host to advance life forms.
Would we want them to know this?
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