Alien astronomers might think we are too close to the sun.
Earth is habitable — no shocker there because well, here we are. But have you ever wondered whether it would look like a great place to live and be a candidate for life when viewed from hundreds, or even thousands, of light-years away?
Astronomer Rory Barnes from the University of Washington-based Virtual Planetary Laboratory wondered that very thing, and what he came up with was that Earth would look good, but not great.
The researchers used the habitability index — developed to help scientists analyze the potential habitability of exoplanets orbiting their stars — to give Earth a grade. Surprisingly, Earth did not score 100 percent, rather it received a mere 82 percent score for its likelihood of being able to sustain life.
Definitely a little ironic, considering we know 100 percent that it does sustain life. However, we have to approach it as if we knew absolutely nothing about Earth to understand why it received this low score.
How astronomers find potentially habitable exoplanets is by spotting the dimming of light that occurs when the planets pass in front of their host star. Spectrometry is then used to estimate the mass and radius of the host star and therefore estimate the size of the planet.
A lot of factors go into judging a planet’s habitability. For example, the amount of energy it absorbs and reflects from its star, the distance and radius of its orbit, the behavior of neighboring planets, whether the atmospheric pressure is sufficient enough for liquid water to exist on the surface, and how rocky they are.
Astronomers use this data to create a model of a planet, which is then compared with information about other worlds. “And you basically try and sort out, do I think that could reasonably be a planet that’s habitable?,” explained Barnes in a press release.
So, where did Earth lose points?
“Basically, where we lose some of the probability, or chance for life, is that we could be too close to the star,” said Barnes. “We actually are kind of close to the inner edge of the habitable zone. If we spotted Earth with our current techniques, we would reasonably conclude that it could be too hot for life.”
With all the data considered, the researchers say Earth would look good but not great to alien astronomers observing us from afar. Meaning, if there were astronomers on other planets who also arrived at the same conclusions as Barnes, they might overlook Earth entirely and begin to search elsewhere.
“The point of the paper is that the [higher-ranking planet] is the best to spend our time on. Because it's less in danger,” said Barnes. “But, it's obviously based on this very limited information.”
So maybe we won’t ever have to worry about impending alien invasions, because Earth really doesn’t look like a great place to live from space. Phew!