The universe isn’t just about us, you know? If there are any other intelligent lifeforms out there, they might too be searching the skies for distant exoplanets harboring like-minded creatures. Should they be extremely lucky, they might even come across planet Earth. But this begs the question, what would aliens see if they were studying our planet?
A new study by the California Institute of Technology has used scientific methods to create "a two-dimensional alien map” showing how the Earth might appear if it was studied from a distant planet beyond our Solar System using technology similar to our own. You can read the full study, which hasn’t been peer-reviewed yet, on the pre-print server ArXiv.
For starters, they collected around 10,000 images of Earth taken by the Deep Space Climate Observatory, an NOAA satellite that’s used to study space weather and observe Earth. They then compiled these images and used them to construct a map of Earth using only light curve observations and the planet's reflective properties, as if they had no knowledge of Earth’s features, such as its seas and landmasses.
As you can see from the end product (below), their image essentially looks like an extremely vague picture of Earth, complete with subtle outlines that denote landmasses, seas, and cloud formations.
Although scientists and science fiction writers suspected their existence for centuries, the first exoplanet was only detected in 1988. A few more were detected in the following years, and then came a boom of discovery. As of August 22, 2019, a remarkable 4,107 confirmed exoplanets are now listed in the Extrasolar Planets Encyclopaedia.
One of the methods used by astronomers to detect these distant planets involves carefully studying the light beaming out of stars. If the starlight has a steady wobble, it suggests that a planet is orbiting around the star. This is because it shows the wavelengths of starlight are alternately squeezed and stretched as the star moves slightly closer, then slightly farther away from us, due to gravitational tugs from orbiting planets. Different gases and chemicals in the atmosphere absorb different wavelengths of light as it passes through, so we can also get a sense of what some exoplanets are made of and the composition of their atmosphere. More recently, it’s even become possible to directly image some exoplanets too.
In theory, this new research could be used as a tool to find exoplanets with Earth-like features in the future. Astronomers are particularly keen to hunt down Earth-like exoplanets as it suggests they have a similar atmosphere and geology to us, meaning they could potentially be home to life.
“The analysis of light curves in this work has implications for determining geological features and climate systems on exoplanets," lead author Siteng Fan, of the Division of Geological and Planetary Sciences at the California Institute of Technology, explained to Universe Today. "We found that the variation of light curves of Earth is dominated by clouds and land/ocean, which are both crucial to life on Earth. Therefore, Earth-like exoplanets which harbor [these kinds] of features would be more likely to host life.”