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An introduction to exoplanets
An introduction to exoplanets

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2.6  Remember, stars are big!

In Activity 2 you saw that the Sun has a radius around 10 times bigger than that of Jupiter, so it has a cross-sectional area of about 100 times that of Jupiter. In Week 2 you compared their volumes and saw that the Sun has a volume more than 1000 times greater than Jupiter’s. And, the average densities of the Sun and Jupiter are similar, so their masses differ by this same factor. In fact, the Sun’s mass is a whopping 2 × 1030 kg, which is remember, 2 with 30 zeros after it!

And the Sun is quite a modest star!

The largest O-type main sequence stars can have radii twenty times greater than the Sun, while the very smallest M-type stars are sometimes not much larger than Jupiter, around 1/10th the size of the Sun. There are even far more gigantic stars out there that are at a later stage in their lives than the main sequence – the largest currently known stars have radii of more than 1500 times that of the Sun!