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Equation 2 · Part 1 · How We Know What Is Inside a Planet

Symbol I^*

I∗=0.4I^{*} = 0.4
I∗I^{*}

What this part means

I∗I^* is part of the quantity the equation computes from the expression on the right.

Its job in the formula

I∗I^* is part of the quantity the equation computes from the expression on the right.

The passage around this formula

and it measures how mass is distributed radially rather than how much there is. A uniform sphere has I∗I^{*} = 0.4 . Anything smaller means mass concentrated toward the centre; anything approaching 0.4 means a body that is close to uniform in density, which for a rocky planet means undifferentiated.

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Learn the underlying idea

An exponent tells how a base is used in multiplication. In x³, x is the base and 3 is the exponent: x³ = x × x × x.

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See this notation across published equations →

Sources cited in the article section

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