What’s the largest planet in the Universe?
You might think Jupiter is large, but you’ll be surprised at what happens if you try and make it larger!
“A few centuries ago, the pioneer navigators learnt the size and shape of our Earth, and the layout of the continents. We are now just learning the dimensions and ingredients of our entire cosmos, and can at last make some sense of our cosmic habitat.” -Martin Rees
In our Solar System, Jupiter is the largest planet we have, but what’s the upper limit to planetary size?
If you get too much mass together in a single object, its core will fuse lighter elements into heavier ones.
At about eighty times the mass of Jupiter, you’ll have a true star, burning hydrogen into helium.
But lower than that, at about 14 times the mass of Jupiter, you’ll initiate deuterium fusion, where leftover fuel from the Big Bang slowly self-generates its own energy.
This line — between a gas giant and a brown dwarf — defines the most massive planet.
In terms of physical size, however, brown dwarfs are actually smaller than the largest gas giants.
Above a certain mass, the atoms inside large planets will begin to compress so severely that adding more mass will actually shrink your planet.
This happens in our Solar System, explaining why Jupiter is three times Saturn’s mass, but only 20% physically larger.
But many solar systems have planets made out of much lighter elements, without large, rocky cores inside.
As a result, the largest planets can be up to twice as big as Jupiter before becoming stars.
Mostly Mute Monday tells the scientific story of an astronomical object or phenomenon in images, visuals and no more than 200 words.
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