Weighing
a planet is a tough task. I mean, it's not like you can just put them
on a bathroom scale. And, while astronomers figured out how to measure
the mass of planets in our solar system a long time ago, it's
practically impossible to weigh
exoplanets. Well, it was until recently.
MIT planetary scientists Julien de Wit and Sara Seager just devised a method that
enables them to weigh an exoplanet by measuring the starlight that
shines through its atmosphere. It's so simple, it's genius. See, when an
exoplanet passes in front of its star, it causes a blip in the amount
of light that shines toward Earth. This is actually how we're able to discover exoplanets in the first place.
Not
all of the starlight zooms past the exoplanet, though. Some is actually
filtered through the atmosphere, and by measuring the spectrum of that
light, the MIT scientists are able to learn all
kinds of things about the planet, such as atmospheric pressure,
temperature, and gravitational pull. With that information, they've come
up with a new method for calculating not just atmospheric chemistry but
a planet's weight and mass.
So
why does this matter? Well, it's always been really difficult to learn
details about exoplanets. They're really far away! With this tried and true starlight method,
though, astronomers can now also deduce whether the planet is gassy
like Venus or rocky like Earth. It also makes it easier to discover new
exoplanets which—let's cut to the chase—brings us that much closer to finding an Earth twin
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