By Michelle Starr
No two planets in the Solar System are exactly alike, but we can broadly categorise them – rocky worlds Earth, Venus, Mercury and Mars; gas giants Saturn and Jupiter; ice giants Neptune and Uranus; and dwarf planets, like Pluto and Ceres.
That sounds pretty diverse, but astronomers have just made a detailed study of a fascinating type of planet we don’t have – super-puff worlds.
Of all the exoplanets our efforts have uncovered to date, only a handful – less than 15 – have been puffy. These three young planets, seen orbiting a star around 2,600 light-years away, are almost the size of Jupiter, but have less than one percent of its mass.
That means they have spectacularly low density; in fact, they’re the puffiest planets ever seen, with a density lower than 0.1 grams per cubic centimetre. In press statements, the texture of these planets has been likened to cotton candy.
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